E-carrier. Connecting to an E-carrier service.
Stands for Extensible Authentication Protocol, a security enhancement of Point-to-Point Protocol (PPP).
See Also Extensible Authentication Protocol (EAP)
Stands for Exterior Border Gateway Protocol, the version of Border Gateway Protocol (BGP) used for exchanging routing information between different autonomous systems.
See Also Exterior Border Gateway Protocol (EBGP)
Refers generally to the process of using the Internet for conducting key activities of your business.
In the new Internet economy two terms are generally confused:
e-commerce: This refers specifically to the process of buying and selling goods and services over the Internet.
e-business: This more general term may include e-commerce activity, but also includes using the Internet for additional core business processes, including management of supply-line services, customer relations, and human resources.
E-commerce is generally B2C (business-to-consumer) in orientation, but e-business includes B2B (business-to- business) activities that join separate businesses entities over the Internet into value chains using negotiated agreements. In an e-business scenario, the basic activities of business (including invoicing, transactions, and procurement) are all performed electronically over the Internet. Technologies such as Electronic Data Interchange (EDI) and Extensible Markup Language (XML) are employed to facilitate the exchange of information between business partners. Because the Internet is a public network, security is a high priority for e-business, and technologies such as virtual private networks (VPNs) and Internet Protocol Security (IPsec) are used to ensure the privacy, integrity, and authenticity of electronic business transactions.
In addition to businesses forming their own private negotiated business arrangements, a large number of public and private e-business marketplaces have emerged in the last few years to facilitate B2B relationships. An example is the Microsoft Market, which is Microsoft Corporation's internal Web-based procurement system.
For companies migrating from the old brick-and-mortar model to the new e-business model, there are many advantages incurred in the move. These include lowered procurement costs, shorter business cycles, more efficient customer service, and new kinds of sales opportunities.
See Also B2B , XML
Stands for Electronic Business Extensible Markup Language, an XML standard that allows businesses to locate each other on the Internet, form partnerships, and exchange business information.
See Also Electronic Business Extensible Markup Language (ebXML)
The digital telecommunications services backbone system of Europe, a format standardized by the International Telecommunication Union (ITU).
Overview
The E-carrier service rates are specified by the organization CEPT (Conf rence Europ enne des Administration des Postes et des T l communications, or European Conference of Postal and Telecommunications Administrations). The most popular of these services, E1, is also the slowest. E1 transmits data at speeds of up to 2.048 megabits per second (Mbps) over two pairs of twisted wires. It consists of 32 separate 64-kilobits-per-second (Kbps) DS-0 channels multiplexed together, each of which can carry either a voice conversation or a stream of data. E1 is sometimes referred to as 2-Meg.
E-carrier. Connecting to an E-carrier service.
E-carrier transmissions are graded E1, E2, and so on, in order of increasing transmission speeds. These different service grades are multiples of the basic DS-0 data transmission rate, similar to the T-carrier system of North American telecommunications carriers. The E-carrier transmission rates are shown in the table included in the article "DS-0" elsewhere in this book. E-carrier lines use 8 bits per channel for encoding signals and do not rob bits for control signals as T-carrier lines do.
E-carrier services were developed in the 1970s and became widely available in the 1980s. E-carrier services can be used for wide area network (WAN) connections, for high-speed Internet connections, for private videoconferencing services, and for public frame relay services. E-carrier services are generally available wherever the parallel T-carrier services are not.
Notes
If the E1 service entering your customer premises needs to connect directly to a different building, you have two options. First, you could have the service provider extend the E1 line to the other building, thus moving the demarcation point (termination point) of the line. This could be costly, however. A simpler solution might be to connect the E1 line to a fiber-optic line driver, install a fiber-optic cable from the line driver to a similar driver in the other building, and then connect the remote line driver to your E1 equipment (see diagram).
See Also T-carrier
Stands for Electronic Data Gathering, Analysis, and Retrieval, an online document management system used by the U.S. Securities and Exchange Commission (SEC).
Overview
EDGAR is an online service with two main functions:
To provide corporations with an electronic method for filing public disclosures such as quarterly earnings statements, annual reports, and so on. This is the "private" side of EDGAR, and companies currently file this information by means of the Web, through virtual private network connections (VPN) or through dial-up modem connections.
To provide a clearinghouse that allows individuals and organizations to view archived reports of publicly traded companies. This is the "public" side of EDGAR, which receives almost 1 million visitors daily.
EDGAR was upgraded in 2000 from its older OS/2 system to Microsoft Windows NT, and the SEC is looking into ways to use Extensible Markup Language (XML) to help EDGAR submissions search for information in its vast database more easily.
For More Information
Visit the SEC at www.sec.gov.
Stands for Enhanced Data Rates for Global Evolution, a third-generation (3G) upgrade for General Packet Radio Service (GPRS).
See Also Enhanced Data Rates for Global Evolution (EDGE)
A device in an Asynchronous Transfer Mode (ATM) network that routes data between an ATM backbone network and local area networks (LANs).
Overview
Edge routers can be used to translate Ethernet or Token Ring data for transmission over ATM backbones. This allows ATM to be used as a backbone for connecting multiple LANs into a metropolitan area network (MAN) or wide area network (WAN).
Edge router. Using an edge router to connect LANs to an ATM backbone.
An alternative and more commonly used configuration is to connect LAN networking equipment directly to ATM backbone switches, which provide points of contact with an ATM provider's backbone network.
An edge router can function as an ATM switch and provide routing capabilities for LAN networking protocols-all in one hybrid device.
See Also Asynchronous Transfer Mode (ATM) ,backbone
Stands for electronic data interchange, the industry standard format for exchanging business information electronically.
See Also electronic data interchange (EDI)
The latest version of Novell Directory Services (NDS).
Overview
Novell eDirectory is the new name for NDS version 8.x and emphasizes the enhanced Internet functionality of NDS. Novell eDirectory is a key part of Novell's "One Net" strategy and includes the following enhancements over previous versions of NDS:
Native support for Lightweight Directory Access Protocol version (3LDAPv3) and LDAP Data Interchange Format (LDIP)
An internal schema that more closely conforms to the LDAPv3 standard than earlier versions
Support for enhanced Domain Name System (DNS) naming conventions
Extensible support for management using the ConsoleOne utility
Increased scalability to support more than a billion objects per directory tree
Novell eDirectory is available for the Novell NetWare, Microsoft Windows NT, Windows 2000, UNIX, AIX, Compaq Tru64 UNIX, Solaris, and Linux platforms. The current version is eDirectory 8.5.
See Also directory
In Microsoft Windows 2000, Windows XP, and Windows .NET Server, the cumulative permissions a user has for accessing a resource based on a user's individual permissions, group permissions, and group membership.
Overview
The effective permissions a user experiences in trying to access a file or folder depend on the various permissions granted to the user expressly or by virtue of membership in a particular group. When a permissions conflict exists between one group and another, or between the user and a group, rules are applied that resolve the issue.
In networks based on Windows 2000, Windows XP, and Windows .NET Server, calculation of effective permissions can be determined using three simple rules:
First, if a user belongs to two (or more) groups, and these groups have different NTFS file system (NTFS) standard file permissions on a given file, the user's ability to access the file both locally and over the network is determined as follows: the effective NTFS permission is the least restrictive (most permissive) NTFS standard permission. For example,
read (NTFS) + change (NTFS) = change (NTFS)
The exception to this is that the no-access permission overrides all other permissions. For example,
read (NTFS) + no access (NTFS) = no access (NTFS)
Second, if a user belongs to two (or more) groups, and these groups have different shared folder permissions on a given shared folder, the user's ability to access the shared folder over the network is determined as follows: the effective shared folder permission is the least restrictive (most permissive) shared folder permission. For example,
read (shared folder) + change (shared folder) = change (shared folder)
The exception to this is that the no-access permission overrides all other permissions. For example,
read (shared folder) + no access (shared folder) = no access (shared folder)
Third, when a user attempts to access a folder or file over a network that has both NTFS permissions (the first example) and shared folder permissions (the second example) configured on it, the effective permission is the most restrictive (least permissive) permission. For example,
read (NTFS) + change (shared folder) = read (combined)
See Also NTFS permissions (Windows 2000,Windows XP ,and Windows .NET Server),shared folder permissions
Stands for Extensible Firmware Interface, a firmware standard for 64-bit Intel processors.
See Also Extensible Firmware Interface (EFI)
A feature of Microsoft Windows 2000, Windows XP, and Windows .NET Server that allows files stored on NTFS file system (NTFS) volumes to be secured through encryption.
See Also Encrypting File System (EFS)
Stands for exterior gateway protocol, any routing protocol used to distribute routing information among different autonomous systems.
See Also exterior gateway protocol (EGP)
Stands for Exterior Gateway Protocol, the original exterior routing protocol used to connect autonomous systems on the Internet.
See Also Exterior Gateway Protocol (EGP)
Stands for Electronic Industries Alliance, the main trade organization representing the U.S. high-tech community.
See Also Electronic Industries Alliance (EIA)
Standards for commercial and telecommunications wiring developed by the Electronic Industries Alliance (EIA) and Telecommunications Industry Association (TIA).
Overview
The EIA/TIA wiring standards actually comprise a group of standards covering different aspects of premise cabling and other wiring practices. These standards include
EIA/TIA 570: Residential/Light Commercial Wiring Standard
EIA/TIA 568A: Commercial Building Telecommunications Cabling Standard
EIA/TIA 569: Commercial Building Standard for Telecommunications Pathways and Spaces
EIA/TIA 606: Design Guideline for Administration of Telecommunications Infrastructure in Commercial Buildings
EIA/TIA 607: Commercial Building Grounding and Bonding Requirements for Telecommunications
When installing wiring for your network, be sure to follow the EIA/TIA standards to ensure that your network functions as expected and that it complies with all local and state building codes and regulations.
The EIA/TIA wiring standards are also supported by the American National Standards Institute (ANSI).
For More Information
Visit the Electronic Industries Alliance (EIA) at www.eia.org and the Telecommunications Industry Association (TIA) at www.tiaonline.org
See Also premise cabling ,structured wiring
Stands for Enhanced Interior Gateway Routing Protocol, a popular interior routing protocol developed by Cisco Systems.
See Also Enhanced Interior Gateway Routing Protocol (EIGRP)
Stands for Enterprise Information Portal, a business software system used to provide a single point of access to information stored in different corporate databases.
See Also Enterprise Information Portal (EIP)
Stands for Enterprise Java Beans, a Java-based technology from Sun Microsystems for building transactional e-commerce systems.
See Also Enterprise Java Beans (EJB)
Stands for Enterprise Knowledge Portal, a business software system that couples knowledge management tools with an Enterprise Information Portal (EIP) to provide a powerful way of handling the flood of information that characterizes large businesses today.
See Also Enterprise Knowledge Portal (EKP)
The process of selecting a new master browser from a Microsoft Windows network's potential browsers.
Overview
If a client machine cannot locate a master browser on the network in Windows NT, Windows 2000, Windows XP, or Windows .NET Server, it initiates an election to select a new master browser. Elections ensure that a master browser is always available on the network, since the absence of a master browser means that clients will be unable to locate and access network resources such as shared files and folders.
If a client machine cannot locate a master browser on the network, it broadcasts an election datagram. When a machine that is a potential browser receives this datagram, it examines the election criteria in the datagram. If its election criteria are better than those of the datagram's sender, the potential browser broadcasts its own election datagram and an election is declared to be in progress. The election criteria for becoming a master browser include many factors, such as the machine's operating system, version, and role. Eventually, one potential browser prevails over other machines on the network because it has superior election criteria, and the election ends.
Notes
Elections also occur when domain controllers are restarted.
See Also browsing ,Computer Browser service
Electrical noise induced in cabling by the presence of nearby electrical equipment such as motors, air conditioners, fluorescent lights, and power lines.
Overview
Electromagnetic interference (EMI) can interfere with the transmission of signals and render network communications unreliable or impossible. EMI is only a problem if copper cabling is used-fiber-optic cabling is immune to sources of EMI.
EMI is caused when the changing electromagnetic fields generated by one cable induce extraneous currents or interference in adjacent or nearby cables. EMI in copper cabling can be reduced to acceptable levels by
Avoiding bunching of unshielded cabling
Keeping all cabling away from power cords and transformers
Using shielded twisted-pair (STP) cabling instead of unshielded twisted-pair (UTP) cabling
Enclosing cabling in external mesh or wire shielding
Properly grounding electrical equipment and external shielding
Taking care not to excessively untwist the terminating ends of twisted-pair cabling
EMI can be a greater concern in heavy industrial settings where high voltages and equipment, such as motors and generators, produce high levels of electrical noise. Using coaxial cabling in these settings affords greater resistance to the effects of EMI than using twisted-pair cabling. Fiber-optic cabling is an even better solution in heavy industrial settings because it is wholly resistant to EMI. (Changing electromagnetic fields has no effect on the light waves traveling along a glass fiber.)
See Also cabling ,noise ,signal
An Extensible Markup Language (XML) standard that allows businesses to locate each other on the Internet, form partnerships, and exchange business information.
Overview
The ebXML standard specifies protocols and mechanisms that allow businesses to use the Internet and XML to create and centrally store business profiles of their companies, find other companies providing desired types of business services, enter into partnership agreements, and collaborate through electronic document exchange such as invoicing, receipts, shipping notices, and so on. The ebXML standard is designed to promote electronic business between companies of any size located anywhere in the world using a common infrastructure (the Internet) and a common language for sharing structured information (XML).
The ebXML standard provides open specifications for how companies define their business processes, create and register company profiles and business processes, enter into trading agreements, and exchange business information using XML messages. Businesses can use ebXML to exchange business information with each other without being concerned about the structure of the underlying data processes of other partners in the process.
The ebXML standard is an initiative of the Organization for the Advancement of Structured Information and Standards (OASIS) and a United Nations (UN) standards body called UN/CEFACT (United Nations Center for Trade Facilitation and Electronic Business). Development of the ebXML standard began in 1999 with the backing and support of IBM, Sun Microsystems, BEA Systems, Commerce One, and a number of other companies.
Implementation
The ebXML standard specifies a set of protocols for packaging business information as high-level messages and routing them to required destinations. Any kind of business transactional message can be encapsulated by ebXML, including electronic data exchange (EDI) X12 messages, EDIFACT messages, XML messages, or some proprietary transactional message schemes.
The ebXML protocol suite is modular in architecture and consists of several protocols that enable encapsulation, transport, and routing of XML messages. To help promote uniform standards in the B2B arena and prevent fracturing of the market, the ebXML group has agreed not to compete with the developers of Simple Object Access Protocol (SOAP), but instead to incorporate SOAP 1.1 as its underlying protocol for enabling remote activation of software components over the Internet. SOAP 1.1 was developed by Microsoft in conjunction with IBM.
For More Information
Visit the ebXML initiative at www.ebxml.org
See Also Simple Object Access Protocol (SOAP) ,XML
An online document management system used by the U.S. Securities and Exchange Commission (SEC), better known by its acronym, EDGAR.
See Also EDGAR
The industry standard format for exchanging business information electronically.
Overview
Electronic data interchange (EDI) is a well-established standard by which companies can exchange business data and perform financial transactions using electronic means. EDI is commonly used by large companies to link their financial systems to supply-chain partners to automate and speed procurement for assembly line processing. Some analysts estimate there are more than 300,000 companies worldwide using some form of EDI to streamline their procurement processes.
EDI is a compact format that allows information to be structured in a way that it can easily mapped to traditional business forms such as invoices, purchase orders, receipts, and so on. EDI is used mostly by large companies that process high volumes of business transactions, and it can save these companies considerable costs by greatly reducing paperwork, mail, and fax charges.
History
EDI was born in the 1970s when large companies such as Kmart Corporation and Sears, Roebuck, and Company saw the need for a standard way of exchanging business information with trading and supply-chain partners. Developing custom solutions for electronic business document exchange was costly, so the Data Interchange Standards Association (DISA) was formed, consisting of government, transportation, and private sector companies, to address this issue. In 1979, EDI was approved as an American National Standards Institute (ANSI) standard called X.12. The X.12 standard defines the data dictionary used by EDI for formatting messages for standard communications between business partners. Other standards competing with EDI for electronic exchange of business documents were concurrently developed, but by the mid-1980s, X12 had become a widely recognized standard and EDI began to be widely deployed, especially in large companies.
Architecture
The basic unit of an EDI transmission is the message, which consists of a transaction set with a header and footer attached. An EDI message adheres to a standard format called the Electronic Data Interchange for Administration, Commerce, and Transport (EDIFACT) protocol.
An EDI transaction set is roughly equivalent to a typical business form, such as a purchase order, and consists of data segments, each containing various fields delimited by some character. These fields represent individual elements of the business transaction, such as company name, account number, quantity, and so on; they are formatted according to a standard code. This code is then implemented as a map between your business application's data fields and the type of EDI standard appropriate to the transaction performed.
EDI transactions are typically processed in batch form. Some forms of interactive EDI have emerged, but the basic architecture of EDI was designed around the concept of mainframe batch processing.
Implementation
EDI-enabled systems communicate through translation software that formats the data into standard EDI encoding format. This information is then exchanged using one of several methods:
Using a dedicated leased line between the business partners. This method is expensive but is often employed by large enterprises that have high volumes of EDI transactions to process.
Using a dial-up modem connection between business partners. This method saves costs by using EDI's strength batch-processing strength. Transactions can be queued and then sent as a batch job over a dial-up connection to save money. Small to medium-sized supply-chain partners often use this method to exchange business information with a large company purchasing their goods or services.
Through an external third-party value-added network (VAN) service provider that acts as a clearinghouse for EDI transactions. The VAN processes EDI messages and routes them to the appropriate electronic mailbox for the destination business partner, who can then retrieve the EDI messages from the mailbox and process the transactions using business applications. The VAN is responsible for message routing, delivery, security, auditing, and archiving. This approach has grown in popularity over the last decade and is probably the most popular EDI implementation in use today.
A newer method used by small suppliers to exchange EDI information with large manufacturers is Web- enabled EDI. Typically, a VAN will offer a Web forms front end that the supplier can use to submit invoices and issue receipts to the purchasing company. This saves suppliers considerable costs over having to build EDI into the back end of their business processes but involves additional expenditure of manual labor in entering data into the forms. Nevertheless, this is a popular scheme that has become widely implemented in some sectors.
Advantages and Disadvantages
Besides its entrenched usage in the big business marketplace, particularly in government, manufacturing, transport, and warehouse sales, EDI has other advantages over such emerging technologies as Extensible Markup Language (XML). For one thing, EDI messages are compact, using a highly condensed format that makes them difficult to read. XML messages, by comparison, are plain text and tend to be much larger than EDI messages. As a result, small businesses that use dial-up connections for exchanging business information with their purchasers and suppliers can save online costs using EDI compared to XML. Because EDI mainly uses leased lines, the technology is intrinsically more secure than a technology such as XML that uses an insecure public network such as the Internet. However, by employing virtual private network (VPN) technology for tunneling over the Internet, the level of security in using XML has been made comparable to that of EDI.
While the costs of implementing EDI or leasing VAN services might at first glance seem higher than XML, this is not actually true because XML is not yet an established standard for communication of business transactions. In particular, XML has the same hidden costs as EDI due to the expense of building either system into a company's back-end business processes, which usually requires much customized programming and tinkering.
EDI's disadvantages are more perception than reality. That EDI is difficult to implement is acknowledged, but so is any translation system that must be deeply integrated into the back end of a company's business software, and nowadays EDI-enabled Enterprise Resource Planning (ERP) and customer relationship management CRM systems are commonly available, as are tools for helping developers custom-build EDI into existing business processes. Another perceived disadvantage of EDI is that it is complex and difficult to learn, but most EDI programmers would disagree with this assessment.
Marketplace
Some of the bigger VANs in the EDI marketplace include GE Information Services and IBM's Advantis. General Electric also offers a Web-based EDI service called GE TradeWeb, which provides companies with browser-based access to a library of EDI-enabled Web forms and an EDI mailbox for exchanging transactions with their business partners. Another player in this market is Sterling Commerce with its Gentran Web Suite, which uses Microsoft ActiveX technologies.
For the foreseeable future, both EDI and XML are expected to coexist, and as a result efforts are under way by both standards bodies and vendors to harmonize the two. Vitria Technology offers a kind of universal translation system for changing EDI information into XML and vice versa. General Electric is implementing the XMLSolutions Business Integration Platform to streamline its online procurement system. Another player in this hybrid EDI/XML service provider market is PaperFree Systems, now acquired by Sybase.
Prospects
Some analysts view the emergence of XML as a threat to the very existence of EDI, supposedly relegating EDI to the arena of legacy systems. This is hardly the case, and most of the electronic business world still gets by using EDI. However, XML has some advantages over EDI; namely, it is more flexible, easier to work with, and more open in its specifications. On the other hand, just as there are different flavors of EDI that hinder interoperability, XML itself has more than 100 different variants, and it might take an initiative such as ebXML (Electronic Business Extensible Markup Language) to bring order to the XML chaos and make XML a truly viable alternative to EDI.
Most large companies are somewhat reluctant to migrate wholesale form EDI to XML. Besides the considerable investment they have already made in EDI systems and the "if it ain't broke, don't fix it" attitude that results, a big concern is the reliability of using XML for exchange of business information over the Internet. Because large businesses usually implement EDI using leased lines, carriers can provide these companies with service-level agreements (SLAs) guaranteeing minimal downtime. The Internet is another factor, however, and it is hard to guarantee bandwidth and availability for information transmitted over the Internet. For batch processing of EDI transactions this is not a big issue, but for companies with delay-sensitive assembly-line processes that use real-time EDI for procurement of direct materials, the XML/Internet combination does not offer the same guarantees as the leased-line/VAN implementations of EDI. As a result, large companies that depend on EDI have been reluctant to open their supply chains to replace EDI with XML, and many are taking a wait- and-see attitude, believing that if they fall behind in the short run they can always use their deep pockets to catch up in the long run.
For More Information
Visit the Data Interchange Standards Association (DISA) at www.disa.org
See Also B2B , XML
The main trade organization representing the U.S. high-tech community.
Overview
The Electronic Industries Alliance (EIA) was founded in 1924 as the Radio Manufacturers Association. The EIA plays an important role in enabling U.S. electronics producers to be competitive by developing technical standards, hosting trade shows and seminars, performing market analyses, and facilitating relations with the government. The EIA represents a broad spectrum of U.S. electronics manufacturing interests.
The EIA is organized along the lines of specific electronic products and markets, with each sector, group, or division having its own board of directors and its own agenda for enhancing competitiveness. Major divisions include the components, consumer electronics, electronic information, industrial electronics, government, and telecommunications divisions.
An important computer networking function of the EIA is the series of standards for residential and commercial network cabling that are collectively known as the EIA/TIA wiring standards. Individuals and companies installing cabling for computer networks must follow these standards to meet government legal and safety requirements.
For More Information
Visit the Electronic Industries Alliance (EIA) at www.eia.org
The practice of backing up data directly to a remote backup facility.
Overview
Classic backup procedures involve backing up data regularly to network tape drives and libraries. In addition, daily copy backups are made of critical business data on servers and these tapes are taken off-site to a secure storage facility. When a disaster occurs, recovery using these off-site daily copies typically takes 48 to 72 hours because the hardware failure must be repaired or the server replaced, the operating system installed, and tapes shipped in from the off-site storage location. Some data is typically lost permanently under this scenario because the tapes are written only once a day but business transactions take place continually.
Electronic tape vaulting, or e-vaulting, is a technique that helps make recovery times faster and restores more up-to-date. In a typical scenario, e-vaulting supplements an existing backup plan similar to the one described above. Information written to local storage on servers is also transmitted over the network through a wide area network (WAN) link to a remote e-vaulting site, where it is written to tape. Data can be e-vaulted periodically (once an hour, for example), or even continuously as each transaction occurs. This transactional information, coupled with traditional daily copy backups, allows databases and other business information to be restored with little or no data loss.
Marketplace
Large enterprises have been using e-vaulting for some time, but recently with the proliferation of storage service providers (SSPs) even small to medium-sized businesses can lease e-vaulting services from a provider. An example of such a service is provided by CNT, a specialist in storage area networking and other storage technologies, and Iron Mountain, a global leader in records management services. Using UltraNet, CNT's storage networking solution, a company can e-vault information incrementally to Iron Mountain's tape vaulting sites.
Notes
E-vaulting can also be used to back up data directly to mirror servers running at remote locations controlled either by the company itself or by storage service providers. This form of e-vaulting is more properly called mirroring.
See Also backup ,disaster recovery ,mirroring
Stands for electronic mail; any system for electronically sending and receiving messages.
Overview
E-mail is arguably the technology that has had the greatest impact on how companies conduct businesses in modern times. E-mail has become the lifeblood of business, with some analysts estimating that fully one-third of all business-related information resides on mail servers, users' personal folders, and mail archiving systems.
E-mail is used for virtually every type of business communication, including marketing, invoicing, and customer service. E-mail saves businesses millions of dollars through the elimination of costly paper contracts, invoices, and receipts. E-mail also costs businesses millions of dollars in wasted time dealing with spam (unsolicited commercial e-mail) and undoing the effects of e-mail viruses. Despite these negative aspects, however, most companies would be at a standstill if their e-mail systems went down.
Estimates suggest that the number of commercial and private e-mail mailboxes globally was more than 500 million in 1999 and may well top 1 billion by the end of 2002. With the advent of wireless messaging, this figure may increase much more rapidly in the next few years. E-mail today is what the telephone was at the beginning of the century-a technology that shaped the evolution of business and commerce worldwide.
History
While e-mail had its roots in the early 1970s with the UNIX community and ARPANET, the first widely- used commercial e-mail system was the IBM mainframe host-based system called PROFS. Early e-mail systems were purely text-based and were expensive to deploy and complex to maintain, but they had an immediate impact on business.
With the move from mainframe systems to a client/server environment in the 1980s, a new breed of e-mail system arose called workgroup mail or LAN mail. Notable products in this area included Microsoft Mail, Lotus cc:Mail, and Novell GroupWise. Over time, these were replaced with collaborative systems that allowed users to exchange not only messages but also schedule and task information. Popular examples of these third- generation systems included Microsoft Exchange and Lotus Notes.
While these developments were occurring, efforts were under way to develop global standards for electronic messaging. These efforts resulted in two main systems: Simple Mail Transfer Protocol (SMTP), developed by the Internet community, and X.400, developed by the International Telecommunication Union (ITU). X.400 rapidly became a popular messaging format that is still used in parts of Europe, but SMTP mail, which was developed in the United States as part of the ARPANET project, eventually superseded X.400 and now enjoys worldwide popularity and acceptance as the universal e-mail system. Messaging and collaboration platforms, such as Microsoft Exchange, now support SMTP by default.
Implementation
Early local area network (LAN) mail systems such as Microsoft Mail and Lotus cc:Mail were essentially passive systems where the mail server was nothing more than a set of folders for containing users' mail. It was up to the mail client to deliver messages to the server and retrieve waiting messages. All processing was thus done by the client, which would periodically poll the server to see if any mail was waiting for it to download. These systems were cheap and easily set up and maintained, but they scaled poorly and had difficulty supporting more than a few hundred users effectively.
The next evolution of e-mail was client/server messaging. Here the passive mail server was replaced by an active server that contacted the client when mail was ready to be picked up. This push model of message delivery was more effective than the old pull model of constant server polling by the client, and it also made messaging more secure. In a client/server system, the client and the server both share the processing and transport of messages.
The X.400 messaging standards introduced a set of standard terminology and concepts into the messaging arena. The most notable of these new terms was MTA (message transport agent or mail transport agent), which was responsible for routing, or forwarding, messages across the network to its destination mail server. A complex messaging system would have a number of MTAs handling mail delivery. In the UNIX world where SMTP mail was born, a popular MTA was developed called Sendmail, which is still widely used on the Internet. Early UNIX mail clients such as Pine and Elm soon became popular, especially at universities and among government researchers. To augment the functionality of SMTP mail, a number of other Internet mail protocols were developed, including Post Office Protocol (POP) and Internet Message Access Protocol (IMAP), which enabled individual mailboxes to be assigned to users, and Multipurpose Internet Mail Extensions (MIME), which made it possible for text-based e-mail to contain binary information such as multimedia files and executables. SMTP itself was extended through SMTP Service Extensions and e-mail was made secure with such new technologies as Pretty Good Privacy (PGP) and Secure MIME (S/MIME).
Marketplace
For corporate messaging and collaboration, the market leader today is probably Microsoft Exchange 2000, a powerful platform that supports a host of features and can be deployed in a wide range of environments, from workgroups to enterprises to service providers. On the Internet, however, Sendmail is still the most popular program for forwarding SMTP mail.
Web-based e-mail allows users to access their personal mailboxes from anywhere on the Internet using a PC with a Web browser and a modem. Microsoft Exchange 2000 Server includes a feature called Outlook Web Access (OWA) that supports this kind of e-mail, as do Lotus iNotes R5, Novell GroupWise 5.5e, Imail Server from Ipswitch, and InScribe Internet Messaging Server Web Mail from Critical Path.
In the wireless messaging arena, a major player is Research In Motion (RIM) with its BlackBerry messaging system. The BlackBerry server application works with Microsoft Exchange or Lotus Notes mail servers and allows messages to be relayed to BlackBerry handheld devices. This allows mobile professionals such as IT (information technology) administrators, to be alerted when systems go down, and it is a more effective way of communicating than using simple pagers. BlackBerry is also a very secure messaging platform because it uses Triple Data Encryption Standard (Triple DES) for encrypting all transmissions.
Service providers, too, now offer various commercial e-mail services to businesses. For businesses that need to send out mass mailings and do not want to overwhelm their mail servers with these duties, companies such as BoldFish offer server software that simplifies the creation and transmission of large volumes of e-mail. Businesses can also outsource this activity to service providers.
Issues
The greatest obstacle to wider use of e-mail in business has been security. Traditionally, SMTP mail has been transmitted in clear text across the Internet, a notoriously unsafe place for such an action to be performed. The slow evolution toward universally trusted public key infrastructure (PKI) systems has hindered the widespread deployment of encrypted messaging and has led to other solutions such as PGP being adopted by some businesses in the meantime. Another solution called Privacy Enhanced Mail (PEM) was developed by the Internet Engineering Task Force (IETF) and is commercially offered by vendors such as RSA Data Security and Trusted Information Systems.
Besides the encryption issue, the last few years have seen the proliferation of what many thought could never occur: e-mail viruses. Some of these viruses have wreaked terrific havoc on corporate and commercial messaging systems around the world. The first such instance was the Internet worm developed by Robert Morris in 1988, which took advantage of a weakness in Sendmail to bring down 6,000 SMTP mail servers around the globe in only 24 hours. More recent examples include the Melissa and LoveLetter viruses, which exploited enhanced collaboration features of Microsoft Outlook to crash mail servers at major Internet service providers (ISPs) and large corporations.
The growing trend toward Hypertext Markup Language (HTML) mail instead of plaintext messaging has also had its associated issues. For example, some marketing companies now send out their HTML messages with a tiny 1-pixel scripted image called a bug in them. The result is that when a user opens the message to read it in his mail program, information such as his Internet Protocol (IP) address and Web site visiting habits is collected from his machine and transmitted to the company. Some companies deal with such issues by simply disabling HTML mail altogether or preventing scripts from running on mail clients, but this seriously hinders the collaborative power of modern mail applications.
Prospects
E-mail continues to gain ground in the business world through such innovative technologies as Web-based messaging, which allows a user to access his personal mailbox from any Internet-enabled PC that has a Web browser on it, and wireless messaging, the "next big thing," is starting to make big inroads in the enterprise through BlackBerry and Personal Digital Assistants (PDAs) Palm and PocketPC.
On the other hand, the next big thing may be the legal issues associated with the growing mountain of old e-mail residing on mail servers in back rooms of corporate networks. In regulated industries such as banking and securities trading, the law requires that all documents relating to business activity be retained for a number of years. Companies often archive old mail in user folders to file servers, but this makes it difficult to search for specific messages when required. In several instances, companies that were sued have been forced to settle because it was simply not cost-feasible for them to search through hundreds of millions of old e-mail messages for documentation that could have won their case. It is important for companies to develop digital records management policies that articulate how old e-mail should be handled and to enforce these policies to limit their legal liability when challenged in court.
Even from a business point of view, having so much critical information stored in nonrelational database management system (RDBMS) systems such as mail servers means that executives and management sometimes lack the information necessary to make truly informed decisions. The emergence of Enterprise Knowledge Portals (EKPs) is one bright spot here, as these systems are designed in part to help tap the unrealized potential of business information stored in old e-mail.
See Also ESMTP ,Exchange Server Internet Mail Access Protocol version 4 (IMAP4), Multipurpose Internet Mail Extensions (MIME), Post Office Protocol version 3 (POP3), Pretty Good Privacy (PGP), Privacy Enhanced Mail (PEM), Secure/Multipurpose Internet Mail Extensions (S/MIME), Simple Mail Transfer Protocol (SMTP), X.400
Any address that ensures that an e-mail message reaches its intended recipient.
Overview
An e-mail address must contain sufficient information so that the message can be routed to its specific recipient. There are various kinds of e-mail address formats depending on the e-mail system in use. Address formats typically include at least two parts:
User portion: This indicates the name or alias of the user to whom the mail is directed.
Routing portion: This indicates the information needed to route the message to the particular mail system where the user's mailbox resides.
The following table shows some examples of e-mail address formats.
Type of Address | Example |
SMTP (Internet) | JeffS@Northwind.Microsoft.com |
Microsoft Mail | Northwind/MICROSOFT/JEFFS |
Lotus cc:Mail | JeffS at Northwind |
X.400 | C=US;a=SPRINT;p=Microsoft; o=Northwind;s=JeffS |
Any type of small-footprint specialized computer system used in industrial, commercial, and consumer applications.
Overview
An embedded system is essentially a way of making ordinary industrial and consumer devices "smart" by embedding computer technology in them. An embedded system typically consists of a single microprocessor, a small amount of memory, a specialized operating system, and applications. These applications are used to control and manage certain functions of the device that contains the embedded system. Typical uses for embedded systems are control and monitoring of industrial machinery and automated management of plant and assembly line operations.
Embedded systems typically have limited processing power and task-specific applications that are used to control and manage larger systems. They may be responsive to environmental or user-controlled conditions and may operate alone or be networked to other systems by wireline or wireless networks, including the Internet.
Examples of embedded systems abound, including
Industrial sensors and control equipment
Automobile antilock brake systems
Automobile Global Positioning Systems (GPSs)
DVD and VCR players
Digital cameras
Microwave ovens
Some analysts estimate there are over 5 billion embedded systems in operation today in industrial, commercial, and consumer devices.
Marketplace
In the 1980s and 1990s, most embedded systems were variants on the 8086 and 8088 processors and used DOS as their operating system platform. In recent years the market has opened up, and a number of vendors are competing in the embedded operating systems marketplace. Big players include
Microsoft Corporation, with its Windows CE and Embedded NT operating systems platforms. Microsoft's embedded operating systems have the advantages of having mature integrated development environments (IDEs) that allow developers to quickly create and deploy applications for embedded systems, and support Transmission Control Protocol/Internet Protocol (TCP/IP) networking, Internet, and wireless networking application programming interfaces (APIs) for building distributed networks of smart devices.
Sun Microsystems, with its Java 2 Micro Edition (J2ME). J2ME exploits the ease of development of the Java platform and has a moderate memory footprint (128 kilobytes [kB] or higher). Third-party vendor Metrowerks has an IDE for J2ME called CodeWarrior that allows embedded J2ME applications to be developed rapidly and easily. Because of the sandbox implementation of the Java VM, however, J2ME is considered by some analysts to be unsuitable for time-sensitive deterministic embedded systems such as microprocessor control systems for spacecraft or automobiles.
Red Hat Linux, with its Linux for Embedded Developers, offers the advantages of Linux's stability and small-footprint operation (32 KB or more).
Wind River Systems, whose VxWorks embedded operating system has been used in devices as diverse as digital cameras, Hewlett-Packard printers, and the Mars Lander space vehicle built for the National Aeronautics and Space Administration (NASA).
Prospects
An impetus has been given to the embedded systems market in recent times through the widespread availability of the Internet. Most analysts expect that the greatest growth of embedded systems in the next few years will be in the area of small Internet appliances such as Web- enabled Personal Digital Assistants (PDAs) and cell phones. The continuing advancements in processor technology that have led to continually more powerful chips for continually lower prices have also provided impetus to the growth of the embedded sector.
For More Information
Visit Microsoft's embedded systems site at www.microsoft.com/embedded.
See Also Java ,Linux ,Windows CE
A feature of the Microsoft Windows .NET Server family that allows servers to run in headless operation.
Overview
Traditionally, UNIX enterprise systems have been configurable for headless operation-that is, running servers without a keyboard, mouse, or video card. Such headless servers are typically used for greater security and are run behind closed doors. Administrators manage these systems by using Telnet to connect to them over the network and issue administrative commands.
Windows .NET Server supports headless operation through its Emergency Management Services (EMS) feature. EMS allows a Windows .NET server to be run in headless mode and managed using a Telnet-based administration console. All management instructions are sent to the headless server using text-based commands.
Implementation
To implement a headless server, you must first enable EMS on the server, either through selecting this option during setup or by configuring the boot loader file afterward. A null modem is then used to connect the headless system through its serial port to VT100 terminal emulation software on a client machine. If the hardware supports it, the VT100 client can also manage the headless server through the universal serial bus (USB) port or over an Ethernet network using an RJ-45 jack.
Notes
To run Windows .NET Server in headless mode, the system's basic input/output system (BIOS) must allow operation without a video card, keyboard, or mouse.
See Also Telnet ,terminal emulator ,Windows .NET Server
A Microsoft Windows 2000 recovery tool for repairing missing or corrupt files and restoring the registry.
Overview
In Windows NT, the emergency repair disk (ERD) was a valuable recovery tool for restoring the registry or replacing boot files on a corrupted system. The Windows NT ERD contained compressed versions of registry hive, default user profile, setup.log, and other system configuration files, and it could be created from the command line using the Rdisk command.
In Windows 2000, the ERD is a little different. Instead of containing registry hives, it contains only boot files and some pointers to operating system files. When a Windows 2000 system is first installed, the registry hives are backed up to \Winnt\repair directory. Also, the ERD is created by selecting an option in the Windows 2000 Backup tool. When the Backup tool is used to back up the registry, this backup is placed in \Winnt\repair\regback.
You can use the ERD to restore a corrupted master boot record (MBR), restore missing or corrupted boot files such as Ntldr, or restore the registry from backup. However, when ERD is used to restore the registry, it does so from \Winnt\repair instead of \Winnt\repair\regback, using the pristine form of the registry that is backed during the initial installation. For more fine-grained control of restoring the registry, use the new Recovery Console tool of Windows 2000 instead of the ERD.
Having a current copy of the ERD for each server on your network is a critical part of preparing for disaster recovery. Always create a new ERD after installing new services or software or upgrading hardware or device drivers on a system.
Uses
To perform a system recovery on a machine running Windows 2000, try booting to Safe Mode first by pressing the F8 function key during startup. If this fails or if the system cannot be repaired, boot the system using the four boot floppies, select the Repair option by pressing the R key when prompted, and then either use the ERD to attempt a repair or press C to open the Recovery Console. The Recovery Console is a powerful command-line interface to the operating system designed for use only by advanced administrators.
Notes
If you cannot find your four Windows 2000 boot floppies, insert the Windows 2000 compact disc and a blank floppy into any machine running MS-DOS or Windows, click Start, select Run, and enter the following path into the Run box:
<cdrom_drive>\bootdisk\makeboot a:
In Windows XP and Windows .NET Server, ERD is being replaced by a feature called Automated System Recovery (ASR).
See Also Automatic System Recovery (ASR)
A floppy disk created during the setup process for Microsoft Windows 98 and Windows Millennium Edition (Me) that can be used to troubleshoot boot problems.
Overview
The emergency startup disk contains files necessary to load a command-line version of Windows, plus other useful system-recovery utilities, including a real-mode registry editor. When you insert an emergency startup disk into your computer and reboot, the computer starts from the disk instead of from the hard drive.
Having a current copy of the emergency startup disk for each machine running Windows 98 or Windows Me on your network helps with disaster recovery if these machines fail to boot properly. You should create a new emergency startup disk whenever you make a configuration change to a machine running Windows-for example, when you install new hardware or update device drivers.
Stands for electromagnetic interference, electrical noise induced in cabling by the presence of nearby electrical equipment such as motors, air conditioners, fluorescent lights, and power lines.
See Also electromagnetic interference (EMI)
Stands for Emergency Management Services, a feature of the Windows .NET Server family that allows a server to run in headless operation.
See Also Emergency Management Services (EMS)
Any process by which one device mimics the functions of another device.
Overview
In computer networks, emulation usually refers to protocol conversion, a process by which a device that understands one protocol can speak with a device that understands a different, incompatible protocol. The environment in which emulation is chiefly used is mainframe computing, where asynchronous terminal emulators are used to emulate and replace more expensive synchronous terminals. For example, a PC with a modem and VT100 terminal emulation software can replace a synchronous VT100 terminal, eliminating the need for a dedicated serial connection between the mainframe and the terminal.
Common types of mainframe terminal emulators include
3270: The 3270 synchronous protocol is used by IBM mainframe hosts that use the Systems Network Architecture (SNA).
5250: The 5250 synchronous protocol is used in the IBM S-series mainframe environment and in AS/400 midframe environments.
See Also 3270 ,5250
A protocol in the IPsec suite of protocols that handles encryption.
Overview
IPsec is actually a suite of protocols that consists of two main protocols:
Authentication Header (AH): This protocol ensures that IPsec packets have not been altered during transmission and to verify the sender's identity. AH is included in IPsec to provide authenticity.
Encapsulating Security Payload (ESP): This protocol ensures that IPsec packets cannot be read except by their intended recipients. ESP is included in IPsec to provide privacy.
ESP is generally used in conjunction with AH to provide maximum security and integrity for IPsec transmissions. However, either ESP or AH can be used alone if sufficient for the intended purposes.
By default, ESP uses the symmetric encryption algorithm Data Encryption Standard (DES) to encrypt the payload of an IPsec packet. ESP can also be configured to use Triple DES, depending upon encryption export restrictions of the business involved.
See Also Authentication Header (AH) ,Internet Protocol Security (IPsec)
Generally, the process of enclosing one type of data packet using another type of data packet.
Overview
Encapsulation occurs when a lower-layer protocol receives data from a higher-layer protocol and then places the data into the data portion of its packet format. Encapsulation at the lowest levels of the Open Systems Interconnection (OSI) reference model is usually referred to as framing. Examples of different types of encapsulation include
An Ethernet frame that encapsulates an Internet Protocol (IP) packet, which itself encapsulates a Transmission Control Protocol (TCP) packet, which then encapsulates the actual data being transmitted over the network
An Ethernet frame encapsulated in an Asynchronous Transfer Mode (ATM) frame for transmission over an ATM backbone
The data-link layer (Layer 2) of the OSI networking model is responsible for encapsulating or framing data for transmission over the physical medium. In local area network (LAN) technologies, this is usually Carrier Sense Multiple Access with Collision Detection (CSMA/CD) for Ethernet networks. For wide area network (WAN) technologies, the data-link protocols used depend on whether the communications are point-to- point or multipoint:
For point-to-point communications, possible WAN data-link protocols include Point-to-Point Protocol (PPP) and High-level Data Link Control (HDLC) protocol.
For multipoint communications, possible WAN data-link protocols include frame relay, ATM, Switched Multimegabit Data Services (SMDS), and X.25.
See Also frame ,Open Systems Interconnection (OSI) reference model
A feature of Microsoft Windows 2000, Windows XP, and Windows .NET Server that allows files stored on NTFS file system (NTFS) volumes to be secured through encryption.
Overview
Encrypting File System (EFS) is designed to protect data on NTFS volumes from local access by unauthorized user EFS which does not work on FAT or FAT32 volumes encrypts information in files at the bit level so that if a hard drive is stolen from a user's system and placed in another system, the information on the drive will be unreadable. In this way, EFS ensures the privacy of a user's information stored on disk and finds particular application with systems vulnerable to theft, such as laptop computers.
EFS is integrated in the NTFS used by Windows 2000, Windows XP, and Windows .NET Server; it is not available for older forms of NTFS, such as the one used in Windows NT 4. EFS operates transparently from the point of view of users: files are automatically encrypted when they are created or moved to encrypted folders and are automatically decrypted when the user needs to access the information stored within them.
EFS also includes a Data Recovery System that employs a trusted recovery agent (usually the Administrator account) that can decrypt any user's encrypted files in an emergency.
The following EFS features have been added to Windows XP Professional and Windows .NET Server editions:
Additional users can be authorized to access encrypted files.
Offline files can now be encrypted.
Data recovery agents are recommended options.
The Triple-DES encryption algorithm can be used to replace DESX.
A password reset disk can be used to safely reset a user's password.
Encrypted files can be stored in Web folders.
Implementation
EFS employs a combination of private and public key cryptography schemes. When EFS receives a request to encrypt a file, a secret (private) key is automatically generated in the form of a random number string. This secret key is called the File Encryption Key (FEK) and is generated using a modified version of the Data Encryption Standard (DES). The FEK itself is secured by encrypting it using the user's private key-a public/private key pair is automatically generated for each user and stored in Active Directory directory service. The encrypted FEK is stored on disk with the user's encrypted files.
The advantage of using this combination of two encryption schemes is that the faster symmetric encryption scheme is used for actual encryption and decryption of file data and the slower public key scheme is used only to protect the user's own private key from theft and misuse. Although EFS employs public key encryption, it does not require a certificate authority (CA) to issue public/private key pairs. Instead, EFS automatically generates these key pairs for individual users and for trusted recovery agents.
Notes
If you are working with applications that create temporary files, you might want to enable encryption at the folder level instead of the file level to guard against unauthorized access to your temporary files. With folder-level encryption, all files in the folder are encrypted.
See Also encryption ,encryption algorithm
The process of rendering information unreadable to all but the intended recipients, who have the ability to decrypt it.
Overview
Cryptography is the science of creating workable procedures for encrypting and decrypting messages. Encrypting messages and transmissions ensures their
Privacy: No one can read an encrypted message other than its intended recipients.
Integrity: An encrypted messages that is intercepted in transit and modified generally becomes garbage when received by its intended recipient-a simple test of whether the message has been tampered with.
Authenticity: A good encryption scheme will help you verify that the message was indeed sent by the person it says it is from by authenticating the identity of the sender.
Cryptography's goal is to ensure that an encrypted message intercepted by a distrusted user cannot be decrypted in a feasible amount of time. Encryption is synonymous with cryptography and has been the basis of all secure communications since ancient times. With the rapid growth in recent years of the Internet as the de facto medium for businesses and consumers to exchange information, encryption has taken on new importance resulting in an explosion of cryptographic technologies and standards has resulted.
Uses
Symmetric key encryption is widely used for securing digital transmission of information. For example, the DES encryption scheme used by the U.S. government since 1974 is a symmetric key encryption algorithm, as is its recent successor, the Advanced Encryption Standard (AES). Symmetric key encryption is also employed in the Windows NT LAN Manager (NTLM) authentication scheme of Microsoft Windows NT and in Kerberos, the default authentication scheme of Microsoft Windows 2000, Windows XP, and Windows .NET Server.
Asymmetric or public key encryption, on the other hand, is widely used on the Internet in the form of the SSL protocol discussed previously. Public key encryption was developed by Whitefield Diffie and Martin Hellman in 1976, and it was made popular by Phil Zimmerman with his Pretty Good Privacy (PGP) encryption scheme for e-mail messaging, which was first released in 1991.
Asymmetric encryption is much slower than symmetric encryption, so many encryption technologies use a combination of the two. In SSL, for example, asymmetric encryption is used during SSL session initialization to securely exchange a secret key between users so that the remaining encryption performed during the session is done using the much faster symmetric encryption scheme.
Implementation
The basic element that makes possible both encryption and decryption is the key. A key is typically a numeric value that is employed in a mathematical procedure called an encryption algorithm to convert ordinary text (plaintext) into encrypted text (ciphertext) and vice versa (encryption algorithms are discussed separately in the corresponding article in this chapter). The number of keys used and the details of how they are employed distinguishes two basic types of encryption, namely symmetric and asymmetric (public) key encryption.
Encryption. The public key encryption method.
Symmetric key encryption uses a secret key known only to the sender and the recipient of the message (and perhaps to others whom they trust). The secret key is used to encrypt the message when it is sent and to decrypt it when it is received. The actual encryption process involves mathematically combining (hashing or transforming) the message and the key in some complex fashion that is virtually impossible to undo unless the recipient also has the key. Symmetric key encryption is very secure, but suffers from one problem-if you want to send a message to someone who does not have your key, you must also find a way to securely transmit a copy of the key. This difficulty makes symmetric key encryption generally unworkable for electronic communication over a network or telecommunications service, except where only the original sender and recipient will need the key. For example, symmetric key encryption works in cellular phone communication when only the subscriber and the service provider need a copy of the user's key. Symmetric key encryption is the oldest form of encryption, dating from at least Roman times.
Asymmetric or public key encryption is a newer method that is becoming widely used in many computer networking and telecommunications systems. For example, public key encryption is employed by the Secure Sockets Layer (SSL) protocol used for transmitting sensitive information such as credit card numbers over the Internet. SSL establishes a secure communications session over the Internet by using public key encryption, which provides every participating user with a public key and a private key. Users are the only ones who know their private keys, whereas their public keys are generally available to anyone who wants them. Remember that if a message is encrypted with a user's public key, it can be decrypted only with the same user's private key, and vice versa.
For example, in public key encryption, if user A wanted to send an encrypted message to user B, it would typically work like this:
User A requests user B's public key or obtains this key from a certificate authority (CA) that both users trust.
User A encrypts his message using user B's public key and sends the encrypted message to user B.
User B receives the encrypted message from user A and decrypts it with user B's private key.
The preceding approach outlines the steps used for encrypting and decrypting the actual message being transmitted during a secure communication session. A different approach, called a digital signature, is used to confirm the sender's authenticity and the message's integrity. Digital signatures are encrypted in a reverse fashion to the message itself. Specifically, if user A wants to send his digital signature to user B, then
User A creates a hash of his message using a hashing algorithm. This hash forms the basis of the digital signature, which user A then encrypts using his own private key.
User A appends the encrypted digital signature and his own public key to the message, which is then encrypted using user B's public key.
User B receives the message and attachments, decrypts its contents using her own private key, and uses user A's public key to decrypt the digital signature that he attached to the message. User B then generates a hash of the received message and compares this to the digital signature that user A sent. If the two are identical, it is unlikely that the message has been tampered with in transit.
Issues
Export of encryption technology is controlled by U.S. law. Certain encryption schemes can be exported only to trusted nations and might require a government review before such export is allowed.
See Also Advanced Encryption Standard (AES) , Data Encryption Standard (DES) , Pretty Good Privacy (PGP), public key cryptography, Secure Sockets Layer (SSL)
A mathematical procedure for encrypting data using a key.
Overview
Encryption algorithms form the basis by which encryption can take place and are fundamental to cryptography. Encryption algorithms generally use some kind of mathematical key (chosen from a large set of available keys) to transform plaintext (the data being encrypted) into ciphertext (the resulting encrypted data). An encryption algorithm must be reversible so that the recipient can use another mathematical key to decrypt the data. A good encryption algorithm should be difficult to decrypt if you do not know the decrypting key, and the only method that should be possible to force decryption should be the brute force method of simply trying every possible decryption key (in other words, there must be no shortcuts or back doors for decryption). If an encryption algorithm is really good, it would take massively parallel computers centuries, or even eons, of intense processing, trying all possible keys, to decrypt a single message if they do not know the specific decryption key.
Implementation
Encryption algorithms typically perform their encryption process on multibyte segments of data instead of on one byte at a time. Such an algorithm is known as a block cipher because it encrypts data one block at a time. For example, the Data Encryption Standard (DES) algorithm, a 56-bit key algorithm used for many years by the U.S. government, encrypts data 64 bytes at a time.
Encryption algorithms employ mathematical procedures called hash functions, which are repeatedly applied to plaintext to scramble it into ciphertext. The combination of a hash function and a key form the basis for the encryption process.
Examples
Encryption algorithms are of two basic types: symmetric and asymmetric.
Symmetric algorithms employ the same key, called a secret key, for both encryption and decryption of a message. This process is also known as asymmetric or secret key cryptography. Examples of symmetric algorithms include
DES: This uses a 56-bit key and was the U.S. government standard for encryption until 2001, when it was replaced by the Advanced Encryption Standard (AES). DES is no longer considered secure and was first cracked in 1997.
AES: This can use keys up to 256 bits in length, and it has replaced DES as the official U.S. government encryption standard.
Asymmetric algorithms employ a different key for encrypting and decrypting data. The two keys are mathematically related and are called a key pair, with the private key used for encrypting the message and the public key used for decrypting it. Examples of asymmetric algorithms include
Diffie-Hellman: Developed by Whitefield Diffie and Martin Hellman in 1976, this is the original public key encryption algorithm and is used in the Secure Sockets Layer (SSL) protocol on the Internet for securely exchanging secret keys between remote systems.
Rivest-Shamir-Adelman (RSA): Developed in 1997 by the Ron Rivest, Adi Shamir, and Leonard Adelman, this algorithm can be used both for encryption and secure authentication. It is used in SSL, Transport Layer Security (TLS), and IPsec communications in virtual private networks (VPNs) and over the Internet.
See Also Advanced Encryption Standard (AES) , Data Encryption Standard (DES) , public key cryptography
A type of contract between a computer software publisher and the purchaser of the software that outlines the various rights granted to the purchaser for legal use of the software.
Overview
The End-User License Agreement (EULA) for a software product is usually found on a separate piece of paper accompanying the product, inside the front cover of the user manual, or onscreen prior to installing the software. You should read and become familiar with the terms of your EULA for the software you purchase. Failure to follow the terms of the EULA might expose you or your company to prosecution for software piracy.
You can access the EULA for Microsoft Windows Millennium Edition (Me) by opening the text file License.txt. It is located in the \Windows folder. In Windows 2000, Windows XP, and Windows .NET Server, the file is called eula.txt and is located in the \System32 folder.
For More Information
Visit Microsoft Corporation's antipiracy site at www.microsoft.com/piracy.
See Also license
Also known simply as Cat5e, a recently ratified standard for structured local area network (LAN) wiring.
Overview
Enhanced Category 5 (Cat5e) cabling is the only ratified cabling standard that is capable of supporting transmission speeds faster that 100 megabits per second (Mbps), although Category 6 (Cat6) and Category 7 (Cat7) specifications have been proposed. Supporting frequencies up to 350 megahertz (MHz) or higher, Cat5e cabling is typically four-pair solid conductor 24-gauge unshielded twisted-pair (UTP) cabling that has a low capacitance in the range of 13 to 14 pF/foot, as compared with regular Category 5 (Cat5) cabling that has a capacitance of around 17 pF/feet. The impedance of Cat5e cabling is 100 ohms, the same as for regular Cat5 cable.
Other specifications of Cat5e include
Attenuation less than 22 decibels (dB) at 100 MHz (same as Cat5)
Near-end crosstalk (NEXT) less than 35.3 dB (3 dB higher than Cat5)
Power-sum NEXT (PS-NEXT) less than 32.3 dB (unspecified for Cat5)
Return loss less than 20.1 dB (unspecified for Cat5)
Uses
The electrical characteristics of Cat5e cabling make it the recommended type of cabling for most new installations of structured wiring, especially companies planning an eventual migration from Fast Ethernet to 1000BaseTX Gigabit Ethernet (GbE). Cat5e cabling can be used for Ethernet, Integrated Services Digital Network (ISDN) wiring, and 155-Mbps Asynchronous Transfer Mode (ATM) networks.
If you plan to use Cat5e cabling in your network, you should ensure that all your other wiring components match these specifications. This means purchasing and installing enhanced Cat5 patch panels, wall plates, and other components. Also, be sure to strictly follow wiring guidelines because improper installation of Cat5e cabling will result in loss of potential bandwidth. The real key to operating a successful high- speed UTP wiring system is careful installation.
See Also cabling ,Category 5 (Cat5) cabling ,premise cabling ,structured wiring
A third-generation (3G) upgrade for the 2.5G General Packet Radio Service (GPRS).
Overview
Enhanced Data Rates for Global Evolution (EDGE) was designed as a way of easily upgrading certain second- generation (2G) cellular systems to 3G systems with little additional cost. EDGE can be used to upgrade both Time- Division Multiple Access (TDMA) systems such as AT&T Wireless and Global System for Mobile Communications (GSM), which are also based on TDMA technologies. EDGE cannot be used to upgrade Code- Division Multiple Access (CDMA) systems. The official 3G upgrade for CDMA systems is instead the International Telecommunication Union's (ITU) Wideband CDMA (W-CDMA) standard. EDGE is designed to provide mobile users with wireless roaming data services of up to 400 kilobits per second (Kbps).
EDGE comes in two flavors:
Enhanced Circuit-Switched Data (ECSD): This is EDGE technology applied to circuit-switched GSM systems, which provide direct connection to the Public Switched Telephone Network (PSTN) backbone.
Enhanced GPRS (EGPRS): This is EDGE technology applied to packet-switched General Packet Radio Services (GPRS) systems, which routes Internet Protocol (IP) packets over the Internet.
Implementation
EDGE works by modifying the physical layer of GSM and GPRS to increase data transmission rates threefold. This is accomplished by replacing the Gaussian Minimum Shift Keying (GMSK) encoding mechanism of GSM and GPRS, which only allows one bit of information to be encoded per symbol, to 8-bit Phase Shift Keying (8-PSK), which encodes 3 bits per symbol. The result is that the theoretical transmission speed of GPRS is raised from 171 Kbps to 513 Kbps, with similar effect for GSM (these theoretical speeds are not realized in practice due to bandwidth being used for error correction).
Above the physical layer, EDGE uses the same technologies as GSM and GPRS. Existing GSM and GPRS cellular networks are easy to upgrade to EDGE, because the same equipment can be used for both the older 2G services and the newer 3G EDGE (though some hardware and software upgrades are required). In addition, costs remain low because no additional frequency licenses are required for EDGE. Although the 400- Kbps data rates offered by EDGE fall short of the envisioned 2-megabit-per-second (Mbps) speeds for 3G cellular systems, EDGE has been ratified as an official 3G system by the ITU in its IMT-2000 specifications.
Marketplace
In North America, EDGE will soon be deployed by AT&T, the major Time Division Multiple Access (TDMA) cellular provider. This will be done in stages, first by upgrading the TDMA system to GSM together with an overlay of GPRS to support data rates of 144 Kbps. The GSM/GPRS system will then be upgraded to EDGE to provide data rates of 384 Kbps. Further 3G upgrades are likely down the road, pushing speeds to 2 Mbps.
Prospects
Although EDGE is an official standard, it is not likely to be supported in many areas outside North America because most other countries having 2G TDMA systems are likely to upgrade them to W-CDMA instead, which is incompatible with EDGE.
See Also 2G ,2.5G ,3G ,General Packet Radio Service (GPRS) ,Global System for Mobile Communications (GSM) ,Time Division Multiple Access (TDMA)
A popular interior routing protocol developed by Cisco Systems.
Overview
Enhanced Interior Gateway Routing Protocol (EIGRP) is a proprietary interior routing protocol developed by Cisco to overcome certain weaknesses of IGRP (Interior Gateway Routing Protocol), an earlier proprietary routing protocol also developed by Cisco. EIGRP is a reliable, efficient dynamic routing protocol that converges quickly and avoids routing loops. EIGRP is intended for classless routing within an autonomous system (AS) and provides a way for routers within an AS to exchange routing table information with each other.
EIGRP is a hybrid protocol that employs features of both distance vector and link state routing protocols. EIGRP is similar to IGRP in several ways:
EIGRP is a classless interior routing protocol used inside an autonomous system.
EIGRP uses a distance vector algorithm for calculating route metrics based on link characteristics instead of hops.
Metrics can be based on values of bandwidth, route latency, reliability, and load.
But EIGRP also differs from IGRP in many ways, and most of these differences involve the incorporation of features common to link state routing protocols. For example:
EIGRP includes a mechanism for automatically discovering neighboring routers using HELLO packets and downloading necessary routing information from these neighbors.
Instead of using periodic broadcasts of entire routing tables, which consumes valuable network bandwidth, EIGRP sends out only incremental updates for routing tables and only when a change in the tables requires such updates.
Routing table information is contained within a topology database similar to that used by link state routing protocols. Only information about adjacent routers is kept in the database, not the routing table for the entire network. This helps keep the topology database small and efficient for fast routing and helps an EIGRP router to recover quickly after a failure.
Other features of EIGRP include
Diffusing Update Algorithm (DUAL): This complex routing algorithm that is similar to Dijkstra's algorithm provides fast convergence and avoids routing loops.
Reliable Transport Protocol (RTP): This protocol guarantees delivery of EIGRP packets to neighboring routers.
Protocol-dependent modules: This feature allows an EIGRP router to support multiple network protocols including Internet Protocol (IP), Internetwork Packet Exchange (IPX), and AppleTalk.
MD5 authentication: Each EIGRP packet contains an MD5 checksum to secure routing communications from outside monitoring.
Notes
Although EIGRP and IGRP share some characteristics and can work together, they are essentially different protocols (by contrast, RIPv2 is simply Routing Information Protocol [RIP] with a few added features). EIGRP can also work seamlessly with IGRP to allow routing information to be shared across boundaries of autonomous systems, which simplifies the setup and configuration of EIGRP routers considerably.
See Also autonomous system (AS) ,classless routing protocol ,dynamic routing protocol ,Interior Gateway Routing Protocol (IGRP) ,routing protocol
A large, geographically distributed company with a high number of users.
Overview
In a computer networking context, an enterprise-level network of computers refers to the network belonging to an enterprise; that is, a network that typically consists of thousands of computers distributed across several geographically remote locations and connected by wide area network (WAN) links.
Enterprise-level networks generally use Transmission Control Protocol/Internet Protocol (TCP/IP) and are divided into a number of smaller networks called subnets, which are linked by routers. Enterprise-level networks are often heterogeneous networks consisting of different protocols and operating systems such as Microsoft Windows NT, Windows 2000, Windows XP, Windows .NET Server, Novell NetWare, and varieties of UNIX, all interoperating to various degrees. Enterprise-level networks can include legacy mainframe and minicomputer systems as well.
This mixture of systems and protocols can make it challenging to administer and manage an enterprise- level network and offers a strong argument for upgrading legacy systems to newer, standardized ones. Companies can save considerable costs in the long run by upgrading their networks to secure, reliable, scalable network operating systems such as Windows NT, Windows 2000, Windows XP, or Windows .NET Server. The initial cost of upgrades and training are quickly recouped through lower maintenance and administration costs, the result of migrating an enterprise's heterogeneous combination of systems and protocols to a homogeneous network consisting of computers running Windows NT, Windows 2000, Windows XP, or Windows .NET Server and running TCP/IP.
A built-in group for the Microsoft Windows 2000 and Windows .NET Server operating system platforms.
Overview
Enterprise Admins is one of four global groups that Windows 2000 and Windows .NET Server create by default to help administrators organize users in their network. The other three groups are Domain Users, Domain Guests, and Domain Admins.
Although Domain Admins are users who can perform administrative tasks on any computer belonging to the domain, the Enterprise Admins group is intended to have an even larger scope. Enterprise Admins must be able to perform administrative tasks on any computer in the enterprise.
A Windows 2000- or Windows .NET Server-based enterprise can consist of a number of domains interconnected in a domain tree, or even several domain trees connected into a domain forest. Enterprise Admins can administer the entire network for the enterprise.
Just as with the Domain Admins group, the Enterprise Admins group has one initial member: the Administrator user account that belongs to the domain. The Enterprise Admins group exists only in the root domain of the forest.
See Also built-in group
A business software system used to provide a single point of access to information stored in different corporate databases.
Overview
Enterprise Information Portals (EIPs) are an evolution of corporate intranets that apply portal technologies to help manage the flood of information that fuels business. Although the intranet revolutionized the way businesses handled information by providing a standard interface (the Web browser) for accessing such information, portals provide other tools such as user profiles, personalization services, workgroup and collaboration tools, automatic indexing, and push/pull information delivery that help manage large amounts of information residing in the diverse data sources of a typical enterprise.
EIPs are simply a wedding of these two technologies, turning corporate intranets into collaborative tools that deliver personalized business information to users as they need it. EIPs generally focus on managing structured information found in databases of two common types of business applications: enterprise resource planning (ERP) and customer relationship management (CRM) applications. EIPs excel in helping users identify, analyze, and present useful information mined from diverse databases used by businesses, and are in many ways simply an extension of data warehousing (DW) and data mining (DM) technologies with an additional emphasis on integrated content management (CM) technologies. EIPs generally excel in bringing together data found in structured data sources such as structured query language (SQL)- and open database connectivity (ODBC)-compliant databases. A further evolution of these systems called Enterprise Knowledge Portals (EKPs) can also mine unstructured sources such as e-mail message repositories and document management systems.
Marketplace
Many new players have appeared since the EIP market exploded in 1999. Some of the early pioneers that have gained significant market share with their packaged EIP offerings include HummingBird International, Epicentric, and Plumtree Software. Some examples of popular EIP offerings in the marketplace include Brio.Portal from Brio Technology, Corporate Portal from Plumtree, DataChannel server from DataChannel, Freedom from InfoImage, iPlanet Portal server from Sun-Netscape Alliance, and many others.
Major operating system and business applications vendors such as IBM, Oracle Corporation, Microsoft Corporation, and Sun Microsystems also offer suites of business applications that can be used to help build EIP solutions for corporate customers. Some EIP applications are more focused on providing corporate users with workgroup tools for collaborative use, and others focus more on enabling decision-makers in a company to access the information they need to map their company's future.
Prospects
The EIP market, which started in 1998, has grown to a multibillion-dollar industry and is expected to rival the traditional ERP and CRM markets in the next few years in scope and deployment.
See Also Enterprise Knowledge Portal (EKP) ,enterprise resource planning (ERP) intranet, portal
A Java-based technology from Sun Microsystems for building e-commerce systems.
Overview
Enterprise Java Beans (EJB) is a set of Java specifications that can be used for building Web-based distributed transactional applications typical of e-commerce and e-business solutions. EJB is a core component of Java 2 Enterprise Edition (J2EE) and works with Java Server Pages (JSP) technologies to provide tools for developers to meet the needs of businesses in today's Internet economy. EJB is particularly popular in the UNIX environment as an alternative to Common Gateway Interface (CGI) solutions based on PERL and C/C++, but EJB applications can run on any Java- supporting platform, including Linux, Solaris, AIX, Windows NT and Windows 2000.
EJB was developed under the umbrella of the Java Community Process, and its current version 1.1 is being revised toward version 2.
Implementation
EJB is implemented as an object-oriented component programming model based on the Java programming language. As a result, EJB is a platform-independent and vendor-neutral solution for building transactional applications. EJB supports both stateful and stateless transactions through its different types of session beans. It can be used to build scalable, distributed applications that run on farms of application servers, and its component-based technology speeds and simplifies the development process to gain better time-to-market advantage.
EJB operates as a server-side component technology. It includes a number of services that make it easy for developers to write middleware supporting distributed transactional processing over the Internet. These services include database connectivity, support for distributed transactions, and security functions.
Marketplace
IBM and Inprise/Borland Corporation both offer EJB server platforms for building e-business solutions. Another company that is a popular player in this market is BEA Systems. The open-source movement is contributing its own EJB server platform, called jBoss, as well.
See Also Java
A business software system that couples knowledge management tools with an Enterprise Information Portal (EIP) to provide a powerful way of handling the flood of information that characterizes large businesses today.
Overview
Information is at the center of today's business, but this information is typically stored in diverse places, such as:
Structured data sources: This includes information in enterprise resource planning (ERP), customer relations management (CRM), and various structured query language (SQL) and open database connectivity (ODBC) databases scattered on servers throughout an enterprise.
Unstructured data sources: This includes e-mail, scheduling, and journaling information stored on mail servers and groupware servers, document management systems that include file servers and document archive systems, and Web-based information repositories such as intranets, extranets, and public Web sites.
Legacy data sources: This covers all forms of data stored on legacy systems such as IBM mainframe and AS/400 systems.
Enterprise Knowledge Portals (EKPs) are systems that gather all these sources of information and allow corporate users to locate, analyze, deliver, and present personalized information through a single point of access. Using the simple Web browser as the universal front end for these systems, users can pull useful information from these sources to help them make informed business decisions or have this information pushed out to them on a regular basis using automatic search engines that parse the data sources using intelligent criteria to determine what users might need. User profiles allow EKPs to personalize the information delivered to users to present what they need, when they need it, and how they need it.
Implementation
EKPs work by combining two technologies:
Enterprise Information Portals (EIPs): These systems are essentially portals to corporate intranets and provide features such as user profiles, personalization services, single sign-on, customizable interface, automatic indexing, and push/pull delivery of information to basic Web-based intranet systems.
Knowledge Management (KM): These tools enable useful information to be combined and mined from sources as diverse as SQL databases, Word documents, spreadsheets, slide-show presentations, text files, and e-mail repositories.
By combining these two kinds of tools, EKP allows information of every form within a company to be unlocked and made available for making informed business decisions.
Advantages and Disadvantages
Although an EKP's advantages are clear in that it provides a unified single point of access to a company's varied sources of business information, the disadvantages are also clear, in that EKP systems are costly to set up and complex to implement. In particular, building an EKP into a company's varied sources of data could require months, or even years, to implement fully, with much of that time spent on custom development work. On the other hand, once these systems are fully implemented, they are easy to maintain and they bring significant long-term cost savings by enabling faster, more informed decision-making and improved communications among corporate users.
Marketplace
A number of companies are offering turnkey EKP solutions that can fit the needs of medium-sized companies without much development work. Portal-in-a-Box from Autonomy Corporation is one example of a turnkey EKP system that automatically classifies, links, and personalizes information and then delivers it to users as they need it.
Big players such as Lotus Development Corporation and OpenText Corporation also offer EKP systems that focus more on the collaborative aspect of business decision-making. And major business application vendors such as Microsoft Corporation, IBM, Sun Microsystems, and Oracle Corporation offer their own suites of applications that can be used to build EKP systems for large enterprises.
See Also Enterprise Information Portal (EIP) ,enterprise resource planning (ERP) intranet, portal
A term describing software systems for managing a broad scope of an enterprise's business functions.
Overview
Enterprise resource planning (ERP) includes tasks such as planning, purchasing, tracking orders, supplying customers, managing inventory, servicing customer requests, producing financial reports, and bookkeeping. ERP software is modular software designed to integrate these various business functions and simplify their management.
ERP software typically consists of an integrated suite of tools for performing standard line-of-business functions such as payroll, accounting, inventory management, and order entry. ERP software is used in transportation and automotive businesses, industrial environments, and other large industrial settings. ERP software lets these businesses manage diverse business resources across the enterprise to plan more effectively for growth and expansion.
History
ERP has its roots in the software-controlled inventory control systems developed and used by large companies in the 1960s. These systems evolved in the 1970s to include scheduling features for automating procurement for assembly-line systems and were then called Material Requirement Planning (MRP) systems. During the 1980s, MRP systems continued to evolve to include distribution and shop floor control and management capabilities and became known as Manufacturing Resources Planning (MRP-II) systems. In the 1990s, these systems were further extended to include the full gamut of business functions, including project planning, engineering, finance, and human resources. The term enterprise resource planning emerged at this time to represent the wider scope of these large software systems.
Marketplace
The three big players in the traditional ERP marketplace are Oracle Corporation, PeopleSoft, and SAP. The biggest of these vendors is Germany's SAP AG, which has an estimated 35 percent share of the ERP market, mainly with its SAP R/3 suite of ERP applications. Another big player is Baan, which has both a traditional ERP offering and an initiative to integrate Extensible Markup Language (XML)- ERP platform through their Baan OpenWorld Integration Framework.
Traditional ERP systems are expensive and often take years to implement fully for large enterprises. In the last few years, a flood of new companies entered the marketplace offering applications that would provide Web- based front ends for traditional ERP software to Internet- enable this software for simplifying enterprise business management. One example of this is the Online Information System (OIS) from Impress Software, which uses the application programming interfaces (APIs) from the big three ERP software vendors to provide businesses access to their SAP R/3 manufacturing systems and other enterprise applications over the Internet. OIS has support for both XML and electronic data interchange (EDI) information exchange, and it is available for diverse platforms, including Windows NT, UNIX, and Linux.
With the proliferation of third-party solutions, the big three have also moved recently to Internet-enable their traditional ERP offerings to make them more competitive. An example is mySAP from SAP AG, which integrates customer relations management (CRM) functions with ERP and provides a portal front end. Although previously most ERP deployments were performed by consulting companies, the Big Three have moved recently to offer their professional services.
Prospects
The most obvious trend in the ERP market is the continuing effort to fully Internet-enable ERP systems and processes. Although early attempts at this represented no more than embedding legacy client ERP interfaces within Web browsers, ERP systems continue to evolve to make their Web-based interface friendlier and easier to use.
ERP was more than a $20-billion market in 2000 and is expected to grow over the next few years. A large portion of this represents planning, consulting, licensing, and maintenance fees for such systems. One recent development is Enterprise Information Portals (EIPs), which provide a new and innovative way of managing the flood of business data that traditional ERP applications expose. EIPs integrate the functions of ERP, CRM, and SCM (supply-chain management) systems into a single Web-based system. Many analysts believe that traditional ERP implementations are on their way out and more sophisticated and powerful EIP systems will grow rapidly, but because of the huge investment most large enterprises have put into ERP systems and the ongoing costs of maintaining them, ERP is likely to be with us for many years.
See Also Enterprise Information Portal (EIP)
A designated server running Microsoft Windows NT, Windows 2000, or Windows .NET Server in an enterprise, which is used as a central repository for software licensing information regarding Windows NT, Windows 2000, Windows .NET Server, and Microsoft BackOffice.
Overview
In Windows NT networks an enterprise server is typically a primary domain controller (PDC), yet can also be a stand-alone server that is not part of any domain in the enterprise. All PDCs in the enterprise replicate their licensing information with the enterprise server, so the enterprise server contains a master database of this information. If there is only one domain in the enterprise, the PDC for that domain is the master licensing server. If there are several domains, each domain's PDC keeps track of licenses for that domain, and all PDCs then replicate their licensing information to the specifically designated enterprise server. Stand-alone member servers that are not part of any domain also must replicate their licensing information with the enterprise server.
They can be more than one enterprise server in an enterprise, but it is simplest to have only one because enterprise servers cannot replicate with each other.
See Also license
Components of Microsoft Windows NT, Windows 2000, Windows XP, and Windows .NET Server that support the running of applications from different operating system architectures.
Overview
Environmental subsystems provide the necessary "environment" in which these applications can run. They are an essential part of the Windows NT operating system that enables cross-platform support for applications written for different operating systems. Windows NT, Windows 2000, Windows XP, and Windows .NET Server include the following environmental subsystems:
Win32 subsystem for running 32-bit Windows applications
OS/2 subsystem for running OS/2 1.X character-based applications (does not support the OS/2 Presentation Manager GUI or Warp versions)
POSIX subsystem for running POSIX.1-compliant applications
Notes
MS-DOS-based applications run on Windows NT, Windows 2000, Windows XP, and Windows .NET Server in the context of a Win32 application called a Virtual DOS Machine (VDM) that emulates an MS-DOS environment.
String variables containing information that an operating system uses to control services and applications.
Overview
Environment variables have been used in Microsoft operating systems since MS-DOS, where the PATH and TEMP variables used in the Autoexec.bat file were early examples. Microsoft Windows NT, Windows 2000, Windows XP, and Windows .NET Server offer a far more extensive selection of environment variables, including the following types:
System (predefined) environment variables such as USERNAME, USERDOMAIN, WINDIR, and HOMEPATH. These variables are set on the system no matter who logs on and cannot be changed by any user. They specify particular parameters pertaining to the system itself, such as the location of the operating system files. They can be used in logon scripts because they are always present when any user logs on.
User (user-defined) environment variables, such as the path to application files. User environment variables take precedence over system environment variables when the two conflict.
Autoexec.bat environment variables, such as those used in path statements.
You can view and specify environment variables in Windows NT, Windows 2000, Windows XP, and Windows .NET Server by using the System utility in Control Panel. Environment variables may be used in logon scripts by enclosing them within percent symbols; for example, %USERNAME% contains the currently logged-on user name.
Notes
The System utility in Control Panel shows only a portion of the system environment variables defined on a system running Windows NT, Windows 2000, Windows XP, or Windows .NET Server.
Stands for emergency repair disk, a Microsoft Windows 2000 recovery tool for repairing missing or corrupt files and restoring the registry.
See Also emergency repair disk (ERD)
Stands for enterprise resource planning, software systems for managing a broad scope of business functions for an enterprise.
See Also enterprise resource planning (ERP)
Stands for SMTP Service Extensions, a set of extensions to the Simple Mail Transfer Protocol (SMTP) protocol.
Overview
ESMTP provides a series of enhancements to SMTP, including authentication between SMTP hosts, the ability to resume a connection that is interrupted without having to begin all over again (called checkpointing), and the ability to transmit multiple SMTP messages at once (called pipelining).
The ESMTP standard is defined in RFC 1869.
Implementation
ESMTP works by enabling the receiving host in an SMTP transmission to inform the sending host of what extensions it supports. Instead of beginning the session with the HELO command, the receiving host issues the EHLO command. If the sending host accepts this command, the receiving host then sends it a list of SMTP extensions it understands, and the sending host then knows which SMTP extensions it can use to communicate with the receiving host.
Implementing ESMTP requires no modification of the SMTP configuration of either the client or the mail server. Most modern SMTP mail systems, including Microsoft Exchange, support ESMTP.
See Also Simple Mail Transfer Protocol (SMTP)
Stands for Encapsulating Security Payload, a protocol in the IPsec suite of protocols that handles encryption.
See Also Encapsulating Security Payload (ESP)
A Competitive Local Exchange Carrier (CLEC) offering metropolitan optical Ethernet services to businesses.
See Also metropolitan Ethernet
The most popular network architecture for local area networks (LANs).
Overview
Ethernet is a baseband networking technology that sends its signals serially 1 bit at a time. In its most basic form, Ethernet operates in half-duplex mode, in which a station can either transmit or receive but cannot do both simultaneously. Another form of Ethernet is full-duplex Ethernet, which uses two pairs of wires with Ethernet switches to allow stations to send and receive data simultaneously without collisions.
Ethernet specifications define the functions that occur at the physical layer and data-link layer of the Open Systems Interconnection (OSI) reference model and package data into frames for transmission on the wire. It is available in three speeds:
10 megabits per second (Mbps), which is simply called Ethernet
100 Mbps, which is called Fast Ethernet
1000 Mbps or 1 gigabit per second (Gbps), which is called Gigabit Ethernet (GbE)
Because of its simplicity and reliability, Ethernet is by far the most popular networking architecture used today.
History
Ethernet was originally developed by Xerox Corporation in the 1970s and was proposed as a standard by Xerox, Digital Equipment Corporation (DEC), and Intel Corporation in 1980. A separate standardization process for Ethernet technologies was established in 1985 in the Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard known as Project 802. The IEEE standard was then adopted by the International Organization for Standardization (ISO), making it a worldwide standard for networking.
Ethernet in its original form, called Standard Ethernet (or 10Base5 or thicknet), was first commercially available in 1981 and standardized as 10Base5 in 1984. A version running on thinner coaxial cable called thinnet (or 10Base2) emerged in 1985 for workgroup LAN deployments, while thicknet remained the providence of campus backbones. The first commercial Ethernet bridges also appeared about 1985.
The next major advance was deploying Ethernet over unshielded twisted-pair (UTP) cabling. This occurred in 1990 with the standardization of 10BaseT Ethernet. A fiber version called 10BaseF was developed in 1993 but never really caught on as advances in technology allowed the speed of Ethernet to be increased tenfold two years later with the development of Fast Ethernet or 100BaseT. Meanwhile, in 1992 the first commercial full-duplex Ethernet products appeared in the marketplace.
The next advance was another tenfold increase in speed to 1000 Mbps or 1 Gbps. This was standardized in 1998 as GbE or 1000BaseX, which initially ran only over fiber but was extended in 1999 to run over copper as well in the form 1000BaseT.
Other significant advances in Ethernet technologies in the last decade include
Auto-negotiation: This was developed in 1996 to support hybrid 10/100 Mbps Ethernet gear and has been extended to 10/100/1000 Mbps as well.
Ethernet switching: The first Layer-2 switches became available in 1992, and VLAN (virtual LAN) features were added in 1998.
Architecture
Ethernet uses the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) media-access control method for determining which station can transmit at a given time over the shared medium. In an Ethernet network, each station (computer) listens to the network and transmits data only if no other station is using the network. If the wire is free of signals, any station can contend (try to take control of) the network to transmit a signal. Ethernet networks are thus based on the concept of contention and operate on a first-come, first-served basis, rather than relying on a master station that controls when other stations can transmit. If two stations try to transmit data at the same time, a collision occurs, and both stations stop transmitting. They wait a random interval of time (measured in milliseconds) and then try again. The more stations on an Ethernet network, the higher the number of collisions, and the worse the network's performance. Typical performance of a 10-Mbps Ethernet network with 100 stations will support a bandwidth of only about 40 to 60 percent of the expected value of 10 Mbps. One way of solving the collision problem is to use Ethernet switches to segment an Ethernet network into smaller-collision domains.
Ethernet. The Ethernet II frame format.
Ethernet stations transmit data over the wire in packages called frames. An Ethernet frame has a minimum size of 64 bytes and a maximum size of 1518 bytes. A total of 18 bytes are used for information such as source and destination addresses, network protocol being used, and other frame overhead. Thus, the maximum payload size (amount of data carried) for an Ethernet frame is 1500 bytes. Ethernet packages data into a frame by four different Ethernet encapsulation methods:
Ethernet II, used for Transmission Control Protocol/Internet Protocol (TCP/IP)
Ethernet 802.3, called Raw 802.3 in Novell networking and used for connectivity with NetWare 3.11 and earlier
Ethernet 802.2, also called Ethernet 802.3/802.2 without subnetwork access protocol (SNAP) and used for connectivity with NetWare 3.12 and later
Ethernet SNAP, also called Ethernet 802.3/802.2 with SNAP and created for compatibility with Macintosh and TCP/IP systems
Implementation
Ethernet can use virtually any physical networking topology and cabling system (medium). Although a star topology (stations that are wired in a star-like configuration to a central hub) is often used from the physical point of view, all Ethernet networks are logical bus-topology networks at heart. One station places a signal on the bus, and that signal travels to every other station along the bus.
Ethernet is available in three speeds and can be further differentiated by media and other considerations, as shown in the table.
Speed | Type of Ethernet | IEEE Standards | IEEE Specs |
10 Mbps | Ethernet | 10Base2 10Base5 10BaseF 10BaseT | 802.3 |
100 Mbps | Fast Ethernet | 100BaseFX 100BaseT 100BaseT4 100BaseTX | 802.3u |
1000 Mbps or 1 Gbps | GbE | 1000BaseCX 1000BaseLX 1000BaseSX 1000BaseT | 802.3z |
Ethernet media specifications such as 10BaseT may seem strange and obscure but can be easily interpreted. For example, 10BaseT means 10 -Mbps baseband transmission over Twisted-pair cabling media.
Prospects
The prospects for the continuing evolution of Ethernet look strong. On the horizon is 10 GbE (10 Gbps Ethernet), which will probably become the next upgrade for enterprise network backbones. Another advance is the recent incorporation of Quality of Service (QoS) features into Ethernet using the 802.1p standard, making Ethernet more suitable for carrying delay-sensitive traffic such as voice an area that until now has been dominated by Asynchronous Transfer Mode (ATM).
Optical Ethernet is a new development that sees carriers such as Yipes extend high-speed Ethernet metropolitan area network (MAN) and wide area network (WAN) connections to businesses in metropolitan areas, eliminating the need for costly Ethernet-to-ATM/Synchronous Optical Network (SONET) access devices and turning corporate WANs into large Ethernet local area networks (LANs).
Another amazing development is that Ethernet is being considered in some quarters as a bus technology to replace PCI for computer system buses. One company involved in this development is Performance Technologies.
Where Ethernet will finally hit the wall and be replaced by some other technology is anyone's guess. In the past 20 years, Ethernet has delivered all but knockout blows to its competitors in the LAN arena, including Token Ring, Fiber Distributed Data Interface (FDDI), and ATM. Whether it can do the same in the WAN arena reamins still in question, but it is bound to be an exciting fight.
Notes
The various Ethernet framing formats are incompatible, so if you have a heterogeneous Ethernet network, you must specify the correct frame type to allow machines running Microsoft Windows NT to see your Novell NetWare servers. Windows NT allows you to select Auto Detect from the Frame Type drop-down list on the NWLink IPX/SPX-Compatible Transport protocol configuration property sheet if you do not know what frame type your NetWare servers are using. (In Windows 2000, Windows XP, and Windows .NET Server, select the check box next to Auto Frame Type Detection in the NWLink IPX/SPX/NetBIOS- Compatible Transport protocol configuration property sheet.) You might also need to configure your routers for the proper frame type. Older Cisco routers running Internetwork Operating System (IOS) version 10 or earlier do not support Ethernet 802.3/802.2 with SNAP.
The table shows some troubleshooting tips for Ethernet media problems.
Problem | Suggestion |
No link integrity | Check that you have not mismatched 10BaseT and 100BaseT (or 100BaseTX and 100BaseT4) cables, hubs, or network interface cards; that ensure no crossover cables are used for station-to-hub cable connections. |
Too much noise | Check for damaged cables; ensure you are using Category 5 (Cat5) cabling (or enhanced Cat5 [Cat5e] cabling for 100BaseT) and that all your cabling interface components (patch panels, wall plates, terminal blocks, and so on) are Cat5 certified. |
Too many collisions (greater than 0.1 percent of total frames on the network) | Check for unterminated cables using a time-domain reflectometer; use a protocol analyzer to look for a jabbering transceiver (a network interface card that is continually broadcasting); and ensure that cables exceed the maximum specified length. |
For More Information
Visit Charles Spurgeon's Ethernet Web site at www.ots.utexas.edu/ethernet.
See Also 10Base2 , 10Base5 ,10BaseF ,10BaseT ,10G Ethernet ,100BaseFX ,100BaseT ,100BaseT4 ,100BaseTX ,1000BaseCX ,1000BaseLX ,1000BaseSX ,1000BaseT , Fast Ethernet, Gigabit Ethernet (GbE)
A unique 6-byte (48-bit) address that is usually permanently burned into a network interface card (NIC) or other physical-layer networking device and that uniquely identifies the device on an Ethernet-based network.
See Also MAC address
A new standard that allows Ethernet and Transmission Control Protocol/Internet Protocol (TCP/IP) to be used for automation networks within industrial plants.
Overview
The Ethernet Industrial Protocol (Ethernet/IP) was developed by the Open DeviceNet Vendor Association, spearheaded by Rockwell Automation. Ethernet/IP is designed to allow commodity Ethernet equipment and TCP/IP software to be used for connecting industrial controllers and automation devices on factory floors. For example, using Ethernet/IP, a programmable logic controller and sensor can be used to remotely control an assembly-line robot tool using IP running over a switched Ethernet network. Other devices that might be used on an Ethernet/IP network include bar-code readers, automated weigh scales, stepping motors, and so on. More generally, Ethernet/IP can be used to tie in a company's industrial control network with its corporate business network, thus automating the exchange of information between inventory control systems and shipping systems for assembly-line processes.
Ethernet/IP is designed to replace an existing industrial controller network protocol called ControlNet, which was developed some years ago by Rockwell Automation and has found widespread acceptance in robotic and industrial environments.
Implementation
Ethernet/IP works by encapsulating messages from two industrial automation protocols, ControlNet and DeviceNet. Ethernet/IP employs the same application layer protocol as these two protocols, namely Control and Information Protocol (CIP). The CIP protocol runs on top of the network layer protocols TCP (used for explicit messaging between controllers and devices) and User Datagram Protocol (UDP) (used for implicit messaging). Ethernet/IP supports both real-time and asynchronous messaging as well as client/server and peer-to-peer messaging.
Ethernet/IP is usually implemented as a switched Ethernet fabric using full-duplex communications. This is necessary because the latency caused by contention in traditional Ethernet networks can have a detrimental effect on time-sensitive industrial assembly-line processes.
Advantages and Disadvantages
The advantage of Ethernet/IP over traditional automation networks is that cost savings can be achieved by running both the corporate network and the automation network using the same technology, namely Ethernet. Ethernet/IP allows control messages to be delivered across a plant floor using off-the-shelf Ethernet gear and without the need to develop custom Ethernet-to- ControlNet gateways. This helps industrial businesses leverage Ethernet's low cost, proven operation, and high bandwidth.
Special training in automation protocols is not required, and only one set of gear needs to be deployed and kept in stock.
Marketplace
Some of the bigger vendors that offer Ethernet/IP- enabled controllers and interfaces are Rockwell, MicroLogix Information Systems, and FLEX I/O.
For More Information
Visit the Open DeviceNet Vendor Association at www.odva.org
See Also Ethernet
Stands for Ethernet Industrial Protocol, a new standard that allows Ethernet and Transmission Control Protocol/Internet Protocol (TCP/IP) to be used for automation networks within industrial plants.
See Also Ethernet Industrial Protocol (Ethernet/IP)
A multiport device based on bridging technologies that is mainly used to segment Ethernet networks.
Overview
Often simply called switches (when referring implicitly to Ethernet networking), these devices are used to enhance the performance of Ethernet networks. An Ethernet switch basically resembles a hub, and consists of a box with a number of RJ-45 jacks on the front to provide ports for network connections. Inside, however, are advanced electronics that generally make switches more costly than hubs.
In a hub, a packet entering one port is regenerated and forwarded to every other port. While the packet is being forwarded, no other port can receive packets, so a hub can be thought of as a shared-media device in which all ports are connected using a shared bus. If a collision occurs on a hub-based Ethernet network, no port on the hub can receive traffic until the collision is resolved. The set of stations connected to a hub is thus called a collision domain. On the average, if a 10-megabits-per- second (Mbps) Ethernet hub has 10 ports, each port effectively gets one-tenth of the total bandwidth, or 1 Mbps. In reality this can be much worse, however, for a single station actively transferring files can consume a large percentage of the available 10 Mbps bandwidth of the hub, leaving other stations starved for bandwidth for their communications. Hub-based Ethernet networks are thus based on contention in which every station must fight for its share of bandwidth.
If you connect several hubs and their networks by uplinking them to a main hub, the situation only gets worse because the new larger network remains a single collision domain. With the increased number of nodes on the network, however, more collisions are likely to occur and network traffic congestion can result, slowing the network to a crawl.
The solution to this congestion problem is to strategically use Ethernet switches in place of, or in addition to, hubs. When a packet enters a port of an Ethernet switch, the switch looks at the frame's destination address, compares it to a table of address-to-port mappings maintained internally by the switch, internally establishes a temporary internal logical connection between the incoming port where the packet arrived and the outgoing port where the packet is destined, and forwards the packet along this internal connection to its destination. Only the port where the packet arrived and the destination port are involved in this process; all other ports on the switch have no part in the connection.
The result of this process is that each port on the switch corresponds to an individual collision domain, and network congestion is therefore avoided. Thus, if a 10-Mbps Ethernet switch has 10 ports, each port effectively gets the entire bandwidth of 10 Mbps, and to an incoming packet the switch's port appears to provide a dedicated connection to the destination node on the network.
In other words, replacing switches with hubs does not add bandwidth to your network. Instead, it reduces the size of collision domains to allow bandwidth to be used more efficiently. If 12 stations are connected to a 12- port 10 Mbps hub, the maximum bandwidth any one station can theoretically use is 10 Mbps, but if a station were actually using this much bandwidth, all remaining stations connected to the hub (except for the station being communicated with) would have zero bandwidth available to them. If a 12-port, 10 Mbps switch were used instead of the hub, however, all 12 stations could participate in 10 Mbps conversations simultaneously, which means the switching fabric supports 12 ports = 6 communications x 2 ports/communication = 6 x 10 Mbps = 60 Mbps throughput. However, the total bandwidth available to any one station is still only 10 Mbps, no more than for the hub. The difference is that this 10 Mbps bandwidth is guaranteed to be always available for each station!
Architecture
A basic Ethernet switch operates at Layer 2 (the data link layer) of the Open Systems Interconnection (OSI) model. Like a bridge, an Ethernet switch is a smart device that can learn the media access control (MAC) address of each connected station by listening to network traffic. The switch builds an internal table listing the MAC address of each port and consults this table when it needs to forward incoming packets.
Ethernet switch. Comparison between how a hub and an Ethernet switch work.
When an Ethernet frame arrives at a port, the destination MAC address is read from the first 64 bits of the frame. This destination address is then found in the switch's internal address table to determine the correct destination port for the frame. Once this is determined, the switching fabric (a mesh-like connection) inside the switch establishes a temporary logical connection between the incoming and destination ports, forwards the frame, and then tears down the connection. Ethernet switches are also capable of establishing multiple internal logical connections simultaneously between different pairs of ports. The result is that each port receives the switch's full dedicated bandwidth at all times, giving Ethernet switches intrinsically much more bandwidth than shared hubs.
The actual mechanism by which switching (the forwarding of the packet between the ports) occurs divides Ethernet switches into two general device classes:
Store-and-forward switches: This type waits until the entire incoming frame arrives, buffers the frame, reads the destination address from the buffered frame, performs cyclical redundancy check (CRC) error checking to verify that the frame is valid, and either forwards the frame to the destination port using the switching fabric or drops the frame if it represents a runt, jabber, or some other invalid frame. Store-and-forward is the same method by which most bridges work. The advantages of this method are that bad frames are eliminated and collisions are handled well, while the disadvantage is that it suffers from high latency (delay) because the frame must be entirely read and buffered before being processed. Nevertheless, most switches used today are of the store-and-forward type, and Transmission Control Protocol/Internet Protocol (TCP/IP) is generally well able to handle any additional latency that arises in networks due to use of these switches.
Cut-through switches: This type reads the frame as it comes into the receiving port, and after the source and destination addresses are read from the first 64 bits, the switch then checks the internal address table and immediately forwards the frame to the correct destination port. Error checking is not performed by cut-through switches, since to perform this check the CRC byte would have to be read first, and this is located at the end of the frame. As a result of not performing error checking, cut-through switches reduce latency and accelerate performance over store-and-forward switches, but the result is that collisions can affect overall communications and bad frames are passed rather than dropped. The earliest Ethernet switches were of the cut-through type and found particular application in NetWare 3.x networks where Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) was less tolerant to delay than Internet Protocol (IP). Limitations in bridging electronics also made cut-through switching appealing in the earliest implementations, but advances in electronics have made store- and-forward switching more appealing. The first commercial Ethernet switches were cut-through switches developed in 1990 by Kalpana, which is now a subsidiary of Cisco Systems.
Implementation
Ethernet switching (or switched Ethernet) can be implemented in various ways depending on the OSI layers at which the switches operate. These include
Layer-2 switch: This basic Ethernet switch operates at the OSI data-link layer (Layer 2) and is based on bridging technologies as explained above. Layer-2 switches establish logical connections between ports based on MAC addresses and are generally used for segmenting an existing network into smaller collision domains to improve performance.
Layer-3 switch: This type operates at the OSI network layer (or Layer 3) and is based on routing technologies. Layer-3 switches establish logical connections between ports based on network addresses such as IP addresses. You can use Layer-3 switches instead of routers for connecting different networks into an internetwork, and they generally perform better than routers due to their enhanced electronics. Layer-3 switches are sometimes called routing switches, multilayer switches, or sometimes simply routers.
Layer-4 switch: This is basically an enhanced Layer-3 switch that has the additional capability of examining the source and destination ports of Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) connections and making forwarding decisions based on this information. They are called Layer-4 switches because they examine OSI transport layer (Layer 4) information within frames and determine how to forward the frames based on this information.
Layer-7 switch: In this type of device the entire frame is unpackaged to determine OSI application layer (Layer 7) information such as what application layer protocol is being used, such as Hypertext Transfer Protocol (HTTP) or File Transfer Protocol (FTP). Frames can then be forwarded or dropped based on this information.
Multilayer switch: This is simply a switch that uses unpackaged frame information from several OSI layers to determine how to forward frames. For example, most Layer-4 switches are actually Layer-3/4 switches since they operate at both layers.
Ethernet switches are also distinguished in other ways, such as by the number of ports they have, whether they operate in half-duplex or full-duplex mode, their transmission speed (for example, 10 Mbps, 1/100 Mbps, or 100/1000 Mbps), ports for connectivity with high-speed Fiber Distributed Data Interface (FDDI) backbones, and so on. Advanced features can include Simple Network Management Protocol (SNMP), out-of-band management (OBM), and custom packet filtering.
Uses
Ethernet switches have two basic uses: segmenting networks to improve performance and interconnecting networks of different speeds. The most common use is network segmentation, and introducing Ethernet switches will provide the most obvious benefit for parts of your network where the most contention occurs. For example, if you have several heavily used servers on the same hub-based local area network (LAN) as clients, the clients have to contend for use of the servers and the result is poor performance. To improve things, segment your LAN into several collision domains, one for each hub and one for each group of clients, as shown in the figure. Now several clients can connect to different servers simultaneously and receive the full throughput of those servers. A good rule of thumb for deciding whether to use switches to segment your existing network is that switches can improve your network's performance if the current network utilization level is higher than 35 percent or if collisions are running at more than 10 percent.
Ethernet switch. Improving performance of a hub-based LAN by using an Ethernet switch.
The second main use for switches is to connect fast workgroup hubs to slower hubs on a network. Again, the main hub is replaced by an Ethernet switch, typically 10/100 or 100/1000 Mbps, and the performance of stations on the fast hub is no longer hindered by the presence of the slower parts of the network. Another related use for Ethernet switches is to connect 100-Mbps Ethernet "islands" to an existing 10-Mbps Ethernet LAN. Simply use a 10/100-Mbps Ethernet switch with two ports to connect them. You can also connect two LANs several kilometers apart by using two Ethernet switches, both having one 100BaseT port and one 100BaseFX port. Connect the switches to the LANs, and then connect a fiber-optic cable between the FX ports.
If users in a department have high bandwidth needs, such as those running computer-aided design (CAD) or multimedia applications, consider replacing their workgroup hub with an Ethernet switch, or if the number of users is small, connect their stations directly to the main Ethernet switch.
When purchasing Ethernet switches, make sure they have Remote Monitoring (RMON) agents built into each port, which will considerably ease remote network troubleshooting.
Marketplace
Ethernet switches are made all shapes and sizes from dozens of different vendors. They vary from small 12-port 10/100 workgroup switches to modular 1 Gbps backbone switches supporting Asynchronous Transfer Mode (ATM) and Synchronous Optical Network (SONET) connectivity. Probably the most popular 10/100 Ethernet switches are those of the Cisco Catalyst 3500 Series XL, which by some counts are deployed twice as often as any other type of similar switch from other vendors. A popular enterprise switch used for collapsed backbones is the Big Iron 4000 switch from Foundry Networks. Another widely deployed backbone switch is the Hewlett-Packard 9304.
Issues
Although Ethernet switches relieve traffic congestion by segmenting collision domains, they do have some disadvantages:
They are generally several times more expensive than hubs of the same speed.
Networks involving switches are more difficult to monitor and troubleshoot.
Ethernet switches should generally be implemented judiciously within Ethernet networks. Simply replacing every hub with a switch is an unnecessary expense that brings negligible performance enhancement over just replacing a few key hubs with switches.
See Also Ethernet ,hub
Stands for Extended Turn, an enhancement for Simple Mail Transfer Protocol (SMTP) to enable SMTP hosts to initiate mail transfers with one another.
See Also Extended Turn (ETRN)
A type of contract between a computer software publisher and the purchaser of the software that outlines the various rights granted to the purchaser for the legal use of the software.
See Also End-User License Agreement (EULA)
Stands for electronic tape vaulting, the practice of backing up data directly to a remote backup facility.
See Also electronic tape vaulting
Any operating system or software condition that is logged by the Event Logging service of Microsoft Windows 2000, Windows XP, and Windows .NET Server.
Overview
You can view events by using the administrative tool called Event Viewer. There are five basic types of events:
Errors: These events represent a significant problem that can lead to loss of data or functionality in the operating system, such as failure of a service to start upon reboot. The corresponding symbol in the system or application log is a red stop sign.
Warnings: These events indicate some impending problem such as low remaining disk space. The corresponding symbol in the system or application log is an exclamation point superimposed on a yellow circle.
Information: These events indicate that a significant system operation has successfully occurred for example, a service has started. The corresponding symbol in the system or application log is an information sign-that is, the letter i superimposed on a blue circle.
Successes: These events are recorded only in the security log and represent auditing information concerning the successful completion of attempts to access secured resources, such as when a user logs on to the network.
Failures: These events are recorded only in the security log and represent auditing information concerning failed attempts to access secured resources, such as when a user attempts to access a shared folder and fails.
A system group existing on all Microsoft Windows NT, Windows 2000, Windows XP, and Windows .NET Server servers and workstations.
Overview
The Everyone group is one of seven (additional new groups exist on Windows XP and Windows .NET Server) built-in system groups that are defined on networks based on the Windows 2000, Windows XP, and Windows .NET Server operating system and includes all local and remote users. This includes users from distrusted domains and non-Windows networks. By default, the Everyone system group has the sole preassigned system right "Access this computer from network." You can grant additional rights to this group if desired. You cannot modify the membership of system groups such as the Everyone group directly.
Notes
When you share a folder on a server running Windows 2000 or Windows .NET Server, or on a workstation running Windows XP, full control permission is initially assigned to the Everyone group. It is advisable to remove this group and assign appropriate permissions to other groups, such as Administrators and Users.
Be careful about assigning additional permissions to the Everyone group. If you allow users who do not have valid user accounts to access the network using the Guest account, they will gain any permissions and rights assigned to the Everyone group.
See Also built-in group ,special identity
Microsoft Exchange Server 2000 is Microsoft Corporation's premier messaging and collaboration solutions- building platform for Windows 2000. Exchange 2000 is part of the Microsoft BackOffice suite of server applications. Exchange Server is designed for mission-critical enterprise-level messaging solutions and includes such features as
Intelligent message rerouting
Transaction-based directory services
Fault-tolerant message store
Built-in server and link monitoring tools
Connectors and gateways for connectivity with foreign mail systems
Exchange 2000 can coexist with most popular and legacy mail systems and can be used for messaging connectivity with the following:
Microsoft Mail
Internet mail (Simple Mail Transfer Protocol [SMTP])
X.400
Lotus cc:Mail
IBM PROFS and SNADS
Exchange 2000 supports all key industry messaging standards, including:
Internet messaging standards such as SMTP, Post Office Protocol 3 (POP3), Internet Message Access Protocol 4 (IMAP4), Lightweight Directory Access Protocol (LDAP), Hypertext Transfer Protocol (HTTP), Network News Transfer Protocol (NNTP), Secure Sockets Layers (SSL), Multipurpose Internet Mail Extensions (MIME), and Secure/Multipurpose Internet Mail Extensions (S/MIME)
X.400 messaging standards
Microsoft's Messaging Application Programming Interface (MAPI)
The Microsoft Outlook 2000 client software, part of the Microsoft Office 2000 suite of business productivity tools, complements Exchange Server by providing users with a full desktop information-management tool for managing messages, appointments, tasks, and contacts. Although the preferred client for Exchange 2000 is Outlook 2000, Exchange clients are available for all the popular operating systems, including MS- DOS, Windows 3.x , Windows 95, Windows 98, Windows NT, Windows 2000, Apple Macintosh, UNIX, and OS/2. Note that the features supported by different clients vary with the platform used.
History
Exchange 4 replaced Microsoft Mail 3.51 in 1996 as Microsoft's client/server messaging and collaboration system. Exchange 4 employed an X.500-based directory and natively supported the SMTP, MIME, MAPI, and X.400 messaging standards, with X.400 being the underlying message transport protocol. In 1997, Exchange 5 was released, which supported additional Internet standards such as POP3 for mailbox access, NNTP for Usenet newsgroups, LDAP for X.500 directory access, HTTP and HTML for Web browser access, and SSL for secure authentication and encryption. Later in 1997 Exchange Server 5.5 added support for Microsoft Cluster Server, IMAP4 and S/MIME protocols, Key Management services, Virtual Organizations, and unlimited message store size.
Exchange 2000 was a radical departure from early versions because it eliminated the proprietary Exchange directory and instead tightly integrated Exchange with Windows 2000's Active Directory directory service. Exchange 2000 includes the Web Storage System, which provides a hierarchical data storage mechanism that incorporates Extensible Markup Language (XML) as part of its specification. Exchange 2000 also tightly integrates with Internet Information Services (IIS), Microsoft's Web services platform and uses IIS as its Internet messaging protocol handler. Exchange 2000 is available in several editions and can be deployed in various ways, including as a messaging system for small companies, a platform for building collaborative workflow applications for large enterprises, Internet mail servers for Internet service providers (ISPs), and hosted messaging and collaboration services offered by Application Service Providers (ASPs).
For More Information
Find our more about Exchange 2000 at www.microsoft.com/exchange.
See Also BackOffice ,
A modern term used to describe applications that have an interface designed for the user.
Overview
The term experience has recently come into common use in programming parlance to describe any application that has a customizable user interface. Developers who work on client software are thus "developing experiences" for the users of their software.
The term experience is also used in the discussion of Microsoft Corporation's .NET platform to mean the delivery of integrated functionality to users through Web services. The .NET platform is designed to allow developers to build compelling user experiences that will provide sets of targeted functionality to bring about the next phase of the Internet's evolution. Some of the pieces already in place to provide this experience include
bCentral, a resource for small businesses
MSN (the Microsoft Network), targeted for consumers
Microsoft Office, aimed at knowledge works
Visual Studio.NET, targeted for developers
Notes
The term user experience is also commonly used to describe the visual appearance and interactivity of software for the Apple Macintosh platform, particularly Aqua in Mac OS X.
See Also .NET platform
A physical disk partition on which a series of logical drives can be created.
Overview
You can create an extended partition on a disk to overcome the limitation of having only four partitions per disk. Information about the various partitions on a disk is stored in a structure called the partition table. The partition table is 64 bytes in size and is located on cylinder 0, head 0, sector 1 of your hard drive, in the same sector as the Master Boot Record. The partition table has the same format no matter what operating system is used on the disk. Up to four partitions can be created on a disk, but only one partition can be extended per disk. In Microsoft Windows 2000, Windows XP, and Windows .NET Server, you can create an extended partition using Disk Management console. For earlier Windows platforms, use the fdisk utility.
Notes
In Windows 2000 and Windows XP, and Windows .NET Server, extended partitions can be created only on basic disks.
See Also partition (disk)
An enhancement for Simple Mail Transfer Protocol (SMTP) to enable SMTP hosts to initiate mail transfers with one another.
Overview
SMTP hosts were originally envisioned as machines that always had to be connected to the Internet using dedicated connections such as leased lines. In this scenario, when a host must send mail to another host on the Internet, it simply does so, assuming the other host is there and is listening to receive any mail forwarded to it.
With the advent of companies wanting to connect their SMTP hosts to the Internet using dial-up connections to save money over leased lines, some mechanism had to be developed to allow a host to tell other hosts that it was online and ready to receive mail. Extended Turn (ETRN) was developed for this purpose. For example, a company may configure its SMTP host to dial up to the company's Internet service provider (ISP) and issue an ERTN command to the ISP's remote host to deliver mail queued on the remote host.
Issues
ERTN is a stopgap solution that was added to SMTP to work around the problem described above. ERTN has several disadvantages, including its complexity to configure and its requirement for a permanent Internet Protocol (IP) address for the dial-up server. A much better solution for downloading corporate mail from an ISP's SMTP host is to use a Post Office Protocol 3 (POP3) server instead.
See Also Post Office Protocol version 3 (POP3) ,Simple Mail Transfer Protocol (SMTP)
A general name for a class of networking devices that extend the distances over which stations (computers) can typically be connected to concentrators such as hubs and switches.
Overview
An example of an extender is a 10BaseT extender for Ethernet networks. In 10BaseT networks, stations should be located no more than 328 feet (100 meters) from a hub, but by using an extender, you can increase this to about 600 feet (183 meters). A 10BaseT extender can thus be used for connecting a remote station, such as a station located in a nearby building, to the network. Extenders are essentially a simplified form of bridge designed to support only a few remote stations. They must be installed in pairs, one at the remote location and one at the main network. Some extenders can be used to carry network data over installed phone lines, connecting remote stations without installing additional network cabling.
Extender. Using an extender to join a remote station to a local area network (LAN).
Extenders are also available for increasing the maximum connection distance for other data transmission technologies such as the Small Computer System Interface (SCSI) bus. A normal SCSI bus is limited to about 20 feet (6 meters), but a fiber-optic SCSI extender can increase this distance to 0.6 mile (1 kilometer) or more using duplex fiber-optic cable. You can use parallel extenders for directly connecting to printers located in a different building. You can use serial extenders to connect computers to remote RS-232 serial test equipment located in laboratories in different buildings.
A security enhancement of Point-to-Point Protocol (PPP).
Overview
Extensible Authentication Protocol (EAP) is an extension to PPP specified in RFC 2284. EAP allows for an arbitrary authentication method to be negotiated during initialization of a PPP session. This is accomplished during the Link Control Protocol (LCP) negotiation portion of the PPP session establishment sequence. EAP allows third-party security products to be used to provide additional security to PPP sessions using special application programming interfaces (APIs) built into operating systems whose implementation of PPP supports EAP.
EAP is designed to make remote access and virtual private network (VPN) communications more secure by allowing any kind of authentication to be used, including
Smart cards such as Fortezza, SecurID, and other token technologies.
MD5-CHAP, which provides 128-bit encryption during authentication.
Kerberos authentication, the standard authentication method for Windows 2000, Windows XP, and Windows .NET Server.
Transport Layer Security (TLS), which is implemented in Web browsers, smart cards, biometric authentication devices, and so on.
In Microsoft Windows 2000 and Windows .NET Server, EAP is supported by both the Routing and Remote Access Service (RRAS) and Internet Security and Acceleration (IAS) services and by dial-up networking (DUN). Each type of EAP authentication method allowed is implemented through specific plug-in modules designated dynamic-link libraries (DLLs) on both the client and the server. So if you purchase a smart card system from a vendor for use with Windows 2000 or Windows .NET Server remote access, you run the vendor's Setup program on both your DUN client and Remote Access Service (RAS) server to install the necessary EAP DLLs.
See Also Point-to-Point Protocol (PPP)
A new firmware standard for 64-bit Intel processors.
Overview
Extensible Firmware Interface (EFI) is a new standard for the firmware that is used to boot PCs using Intel Corporation's new 64-bit Itanium processor family. EFI is required for all Itanium-based systems that will run Microsoft's new 64-bit Windows platform because these systems cannot boot using the basic input/output system (BIOS) or System Abstraction Layer (SAL) alone. EFI will be supported in all 64-bit versions of Microsoft Windows.
For More Information
See www.microsoft.com/hwdev/EFI.
See Also 64-bit architecture ,64-bit Windows
A meta-language used as a universal standard for electronic data exchange.
See Also
XML
A cable used to extend a length of cabling.
Overview
Extension cables are available in all types with various connector devices and can be used to extend serial lines, parallel lines, network cables, power cables, and other cords.
Extending a cable using an extension cable is not always a good idea because the additional interface introduced by the connection usually results in some signal loss. Furthermore, extending network cables can cause problems if the new, longer cable exceeds the maximum length of the specifications for that type of network. For example, extending unshielded twisted-pair (UTP) cabling beyond 328 feet (100 meters) in a 10BaseT Ethernet network can result in unreliable communication between hosts on the network.
The version of Border Gateway Protocol (BGP) used for exchanging routing information between different autonomous systems.
Overview
There are two versions of BGP, the classless dynamic routing protocol used on the Internet. These versions are
Exterior Border Gateway Protocol (EBGP): This is an exterior routing protocol that is used for exchanging routing information dynamically between border routers connecting autonomous systems (ASs) on the Internet or in a large private Transmission Control Protocol/Internet Protocol (TCP/IP) internetwork. When referring simply to BGP, the variant EBGP is always implied. In other words, EBGP is usually just called BGP.
Interior Border Gateway Protocol (IBGP): This is an interior routing protocol that is used for exchanging routing information between routers within an AS.
See Also autonomous system (AS) ,Border Gateway Protocol (BGP) ,classless routing protocol ,dynamic routing
Any routing protocol used to distribute routing information between autonomous systems.
Overview
Also known as exterior routing protocols, exterior gateway protocols (EGPs) specify how different autonomous systems (ASs) within large Transmission Control Protocol/Internet Protocol (TCP/IP) internetworks such as the Internet communicate with each other to exchange routing information. EGPs facilitate the exchange of inter-autonomous-system routing information between different autonomous systems, independent of which interior gateway protocols (IGPs) are used within these autonomous systems.
There are two EGPs for IP internetworks:
Exterior Gateway Protocol (EGP): This is the original EGP developed in the early days of the Internet to facilitate the Internet's growth. Note the confusing use of the term Exterior Gateway Protocol (EGP) here-EGP stands both for the general category of inter-AS routing protocols and also for the first actual protocol developed within this category. In other words, EGP is one of two examples of an EGP! For more information, see the second article titled "Exterior Gateway Protocol (EGP)," which is the next entry in this chapter.
Border Gateway Protocol (BGP): This is a newer EGP that has replaced the Exterior Gateway Protocol for inter-AS communication on the Internet.
See Also autonomous system (AS) , Border Gateway Protocol (BGP) ,dynamic routing , interior gateway protocol (IGP), Internet, routing protocol
The original exterior routing protocol used to connect autonomous systems on the Internet.
Overview
Exterior Gateway Protocol (EGP) was the original interdomain routing protocol developed for communicating routing information between autonomous systems on the Internet. In fact, the idea of autonomous systems was developed in conjunction with EGP.
EGP was developed in 1982 for the ARPANET, the precursor to the Internet, and was conceived at a time when the Internet was envisioned as a single core network to which various other networks were connected. The developers of the Internet saw early on that scaling problems would occur as the Internet grew in size and complexity, and so the idea of apportioning the Internet into separate sections called autonomous systems (ASs), each under someone else's authority, was developed. Large private internetworks connected to the Internet were assigned autonomous system numbers (ASNs), and the core network itself was divided into several ASs.
To facilitate exchange of routing information between routers connecting these different networks, the concept of dynamic routing was introduced and two kinds of dynamic routing protocols were developed:
Interior gateway protocols (IGPs): These are used for routing within an AS and are thus intra-AS routing protocols. IGPs allow the routers within an AS to exchange routing table information with each other dynamically. Examples of IGPs include Routing Information Protocol (RIP) and Open Shortest Path First (OSPF).
Exterior gateway protocols (EGPs). These are used for routing between different ASs and are thus inter-AS or interdomain routing protocols. EGPs allow routers on the borders between different ASs to exchange routing table information with each dynamically. Examples of EGPs include Exterior Routing Protocol (EGP), from which the more general category EGP was later derived, and Border Gateway Protocol (BGP), the EGP commonly in use on the Internet today.
Implementation
Exterior Gateway Protocol, as defined in RFC 904, is based on the distance vector routing algorithm, but has the limitation that it only maintains information about a single route between two different ASs. EGP thus assumes that only a single path exists between any two ASs within the Internet, a condition that was seen early on as unrealistic. EGP also does not indicate the cost of the route between two ASs, only whether the route is reachable or unreachable. Furthermore, EGP supported only classless routing, and when it was implemented it was already obvious that the class A/B/C system of allocating Internet addresses would soon exhaust available addresses. As the Internet grew it became more complex in its structure as multipath connections between ASs began to develop. EGP's weakness was quickly realized and BGP was developed to replace it. BGP also supports Classless Interdomain Routing (CIDR), which superseded the Internet's earlier classful routing system.
Today EGP is considered a legacy routing protocol and is no longer used on the public Internet, although it is probably still used in some large private Internet Protocol (IP) internetworks that have seen no real need for upgrading to BGP. Interestingly enough, as of 2001 EGP was still being used for MILNET, the public portion of the U.S. Defense Data Network.
See Also autonomous system (AS) , autonomous system number (ASN) ,Border Gateway Protocol (BGP) ,classless interdomain routing (CIDR) ,dynamic routing protocol , interior gateway protocol (IGP), Internet, Open Shortest Path First (OSPF), Routing Information Protocol (RIP), routing protocol
Another name for an Exterior Gateway Protocol (EGP), any routing protocol used to distribute routing information between autonomous systems.
See Also Exterior Gateway Protocol (EGP)
A private Transmission Control Protocol/Internet Protocol (TCP/IP) network that securely shares information using Hypertext Transfer Protocol (HTTP) and other Internet protocols with business partners.
Overview
An extranet is basically a corporate intranet that is securely exposed over the Internet to specific groups that need access to it. Extranets are powerful tools because they let businesses share resources on their private networks over the Internet with suppliers, vendors, business partners, and wholesale customers. Extranets are typically used for supporting real-time supply chains, for enabling business partners to work together, and to share information such as catalogs with customers. Extranets basically comprise the B2B (business-to- business) portion of an e-business system, and building an extranet is an essential step for companies who want to compete in today's Internet economy.
Implementation
Extranets built on the corporate intranet model follow the client/server paradigm, with Web servers such as Microsoft Internet Information Services (IIS) functioning as the server, and Web browsers such as Microsoft Internet Explorer functioning as the client. Other extranet models exist, however, such as a peer-to-peer business connection for electronic data interchange (EDI). Peer-to-peer extranets between business partners typically use virtual private networks (VPNs) to establish secure, encrypted communication over the unsecured Internet for the transmission of sensitive business information, such as EDI between partners, or between headquarters and branch offices. These extranets act as dedicated gateways between business partners and generally do not allow private access to individual users. Peer-to-peer extranets can use Internet Protocol Security (IPsec) with a public key infrastructure (PKI) to provide IP-based authentication and encrypted transmission of information.
Client/server extranets have different requirements, however, because individual users must be authenticated before receiving secure, encrypted access to company resources. Instead of authenticating on the basis of IP addresses as in peer-to-peer extranets, users must be authenticated using user accounts or digital certificates mapped to accounts. Client/server extranets might support HTTP access only or might allow other client/server applications to run. Encryption for HTTP access is performed using the Secure Sockets Layer (SSL) protocol.
Although a basic extranet can be built easily by scripting a Web server to run as a front end for a corporate database, real-world extranets are often more complex. The difficult part is to build the extranet back into the back-end database systems and other sources of business information that business partners need to access. Virtual Private Network (VPN) and firewall technologies are commonly used to provide secure access between different partners over the Internet, and Extensible Markup Language (XML) is emerging as an essential tool for structuring business information for exchange between partners. Extranets also often need to be coupled with directory services for managing access to information through policy-based mechanisms.
Advantages and Disadvantages
The power of the extranet is that it leverages the Internet's existing technology to increase the power, flexibility, and competitiveness of businesses using well-known and easily used tools such as Web servers and Web browsers. Extranets also save companies money by allowing them to establish business-to- business connectivity over the Internet instead of using expensive dedicated leased lines. Extranets can also save money by reducing phone and fax costs.
Marketplace
A new breed of policy-based access management tools has emerged for providing the infrastructure needed to build large directory-enabled extranets. Two popular products in this arena are GetAccess from enCommerce and SiteMinder from Netegrity. The Microsoft BizTalk framework and its associated server platform is seen as a key player in the emerging XML-ization of business extranets and other B2B services.
See Also electronic data interchange (EDI)
