See
See Internet Assigned Numbers Authority (IANA)
See Internet Authentication Service (IAS)
See Independent Computing Architecture (ICA)
See Internet Corporation for Assigned Names and Numbers (ICANN)
See Internet Control Message Protocol (ICMP)
See integrated communications provider (ICP), Internet Cache Protocol (ICP)
A program that enables users to locate other ICQ users on the Internet and communicate with them in real time. ICQ, which homophonically stands for “I seek you,” lets you search for users currently online on ICQ networks and alerts you when friends go online. You can use ICQ to send real-time messages to other users, have group chat sessions, send e-mail, transfer files and URLs, play games, and so on. ICQ can even function as a universal platform for launching any peer-to-peer application, such as Microsoft NetMeeting.
How It Works
When you install ICQ and begin the registration process, you are connected to an ICQ server that belongs to a network of such servers distributed across the Internet. During registration, you are given a unique number called an ICQ#, which identifies you to all other users on the ICQ network. You use your ICQ# to register your presence with the ICQ network when you go online and start ICQ, and to allow other ICQ users to recognize when you are online so that they can contact you. You can specify a list of ICQ friends, and an ICQ server will alert you when any of these friends go online.
On the Web
•
ICQ Inc. : http://www.icq.com
See Internet Database Connector (IDC)
See Internet Data Query (IDQ)
See Microsoft Internet Explorer
See Internet Explorer Administration Kit (IEAK)
See Institute of Electrical and Electronics Engineers (IEEE)
An Institute of Electrical and Electronics Engineers (IEEE) standard for a parallel interface developed by Hewlett-Packard that is used for connecting computers to measurement sensors and test equipment for automatic data acquisition in a laboratory or industrial setting. Examples of such equipment include signal generators, frequency counters, voltmeters, and temperature sensors.
How It Works
IEEE 488, also known as the General-Purpose Interface Bus (GPIB), provides high-speed parallel communication using a 24-pin connector. An IEEE 488 cable generally has eight single wires for data transfer, eight twisted-pairs for interface handshaking and management, and a drain (ground) wire, all enclosed in an insulating protective jacket. This configuration provides eight bidirectional channels for transmitting 1 byte (8 bits) of information at a time, at a maximum bus speed of 1 Mbps using tristate drivers. You can chain together up to 15 devices for a total length of 20 meters, with no more than three connectors stacked and no more than 2 meters between adjacent devices. The master device acts as a controller that determines which device can transmit data over the bus at any given time, while the other devices are placed in standby mode. Only one device can transmit signals on the bus at any given time, but multiple devices can receive those signals.
TIP
If your industrial environment is dusty or has high levels of electromagnetic interference (EMI) from motors, generators, or other heavy equipment, you can obtain special shielding covers to protect your IEEE 488 connectors. You can use switchboxes to alternate several industrial sensors on a single IEEE 488 cable.
See Project 802
An Institute of Electrical and Electronics Engineers (IEEE) standard for high-speed bidirectional parallel communication. IEEE 1284 defines the high-speed printer interface called the Enhanced Parallel Port (EPP), which is compatible with the Centronics port used for connecting parallel port printers to computers. IEEE 1284 enables bidirectional communication between computers and attached printers. It also enables computers to spool jobs to printers at more than 10 times the speed of a traditional parallel port interface.
How It Works
To make bidirectional printing work using IEEE 1284, you need the following:
A print device that supports bidirectional printing.
A printer driver that supports bidirectional printing.
A correctly configured parallel port on the connected computer (print server). For example, if the parallel port is configured as AT-compatible, change it to PS/2 mode.
An IEEE 1284–compliant cable.
For example, Microsoft Windows 98 can detect plug and play print devices by communicating with them. The bidirectional communication allows the print device to return information to the computer that queried it for hardware information. This information can include IEEE 1284 device ID values, printer memory, installed fonts, and other information that the printer driver on the server can use to install and configure the printer. Bidirectional communication also allows the print device to send status messages (such as an “out of paper” message) to the server.
IEEE 1284 specifies two electrical interfaces:
Level I interface, which functions at a lower speed and provides only reverse-mode capabilities
Level II interface, which functions at a higher speed and provides bidirectional communication
The connectors for the IEEE 1284 interface also come in several types:
Type A connectors, which are standard 25-pin DB25 connectors
Type B connectors, which are 36-pin centerline Champ connectors with bale locks to hold the cable in place for physical security
Type C connectors, which are 36-pin centerline miniconnectors with clips for physical security
TIP
An IEEE 1284 cable typically has “IEEE 1284” printed on its insulating jacket. IEEE 1284 cables are commonly used for connecting laser printers, scanners, tape drives, and portable storage devices (such as Iomega Zip drives) to a computer; these cables have a DB25 male connector on one end and a Centronics 36 male connector on the other. You can obtain cables for converting the IEEE 1284 parallel interface to the universal serial bus (USB) interface to connect print devices with a Centronics connector to a computer with a USB connector. Special signal-powered IEEE 1284 cables can allow printers to be located up to 100 feet from the connected computer and still maintain reliable communication. Adapters are available for connecting 36-pin and DB25 connectors.
See FireWire
See Internet Engineering Task Force (IETF)
See Internet Group Management Protocol (IGMP)
See Interior Gateway Protocol (IGP)
See Internet Information Services (IIS)
A cache maintained by Internet Information Services (IIS) that stores file objects that are frequently requested by the World Wide Web (WWW), File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP) services and by Active Server Pages (ASP) applications. The IIS Object Cache contains handles for open file objects, directory listings, and other frequently used file system objects. The cache runs within the main inetinfo.exe process and provides improved performance for IIS services and ASP applications.
TIP
For performance reasons, you should keep the IIS Object Cache in the working set of the IIS process in RAM. Be sure that you have sufficient RAM to do this. If you don’t have enough RAM, the IIS Object Cache will be paged to disk and performance will be impaired. You can observe the performance of the cache by using Performance Monitor. Look for counters relating to cache hits and cache misses for each IIS service.
See Internet Locator Service (ILS)
See Internet Mail Access Protocol version 4 (IMAP4)
In physics, the measure of resistance to the flow of electric current. Impedance to signal flow within a transmission line has three components: a resistive component, a capacitative component, and an inductive component. The value for each component varies with the frequency of the current, which means that the overall impedance of a transmission line also varies with frequency. A perfect transmission would have an impedance that does not change with frequency.
Characteristic impedance is the measure of resistance of a transmission line (such as a cable) calculated with the assumption that the cable is of infinite length. It is represented by the symbol Z0 . Each type of network cabling has its own characteristic impedance. Twisted-pair cabling can have a relatively constant impedance by virtue of its design and dimensional characteristics. The EIA/TIA wiring standards, specifically EIA/TIA 568-A (Commercial Building Telecommunications Cabling Standard), mandate that category 5 cabling should have an impedance of 100 ohms, plus or minus 15 percent, up to a frequency of 100 MHz. It is important that cabling meet these standards because networking equipment, such as hubs, switches, and routers, is designed to match this impedance value. If wiring with a different impedance is used with such equipment, reflections of signals can occur that can distort signals, create signal loss, and degrade network communications—or even render them impossible.
NOTE
Impedance is an issue only with copper cabling and is not a relevant physical characteristic for fiber-optic cabling.
Generally, a mechanism for supporting client/server communication. In Microsoft Windows NT and Windows 2000, impersonation is a method that a server uses to determine whether a client has sufficient rights to access a resource.
How It Works
Impersonation involves temporarily altering the security context of the server so that it matches that of the client. When the client attempts a connection to a resource on the server, it tells the server the impersonation level that the server can use to service the client’s request. The client can offer four impersonation levels:
Anonymous: The server does not receive any information about the security context of the client.
Identification: The server can authenticate the client but cannot use the security context of the client for performing access checks.
Impersonation: The server can both authenticate the client and use the client’s security context to perform access checks.
Delegation: The server authenticates the client and passes the client’s security context to a remote server on the client’s behalf. Delegation is not supported by the NTLM authentication method of Windows NT Server, but delegation is supported by the Kerberos authentication method of Windows 2000.
An example of impersonation occurs when anonymous access is enabled on a Web site hosted on Internet Information Services (IIS). Anonymous access uses the IUSR_ComputerName anonymous account on the IIS server, which is part of the Guests local group. If an IIS machine receives a Hypertext Transfer Protocol (HTTP) request from a remote Web browser, IIS impersonates the IUSR_ComputerName account so that it can allow the remote client to access the requested files or run the requested application. This prevents access to system files on the IIS machine by the remote client.
A computer running Microsoft Windows 2000 Server, Windows 2000 Professional, or Windows NT, to which directories and files are imported from a Windows NT–based server that is running the Directory Replicator Service. The import server contains a replica of the directory tree that is received from an export server by the Directory Replicator Service.
You configure an import server using the Replication button in Server Manager, which you access from the Server icon in Control Panel or from the Start menu’s list of administrative tools. To do this, you must specify the following:
The location to which you want to import the exported directory tree. The default tree is %SystemRoot%\System32\Repl\Import.
The domains or computer names from which you want to import the tree.
See also Directory Replicator Service
See International Mobile Telecommunications-2000 (IMT-2000)
See inverse multiplexer (IMUX)
A special domain in the Domain Name System (DNS) that is used for inverse queries. Using the in-addr.arpa domain, a resolver can submit a request to a name server to resolve an IP address into its corresponding fully qualified domain name (FQDN).
How It Works
The in-addr.arpa domain contains nodes whose names are based on IP addresses with octets in the reverse order. For example, a host with the IP address 172.16.8.44 would be represented in the in-addr.arpa domain by 44.8.16.172.in-addr.arpa. Resource records for the in-addr.arpa domain are called pointer (PTR) records and are contained within a type of zone file called a reverse lookup file.
See also DNS namespace, DNS query, Domain Name System (DNS)
Generally, any signaling transmission that takes place within a range of frequencies that are normally used only for data transmission. Instead of using separate control and data channels, control information is transmitted using a portion of the data channel. If a separate control channel is used, the service is called out-of-band signaling.
For example, in-band signaling is used in switched 56 services, in which a 64-Kbps digital communication link has 8 Kbps set aside for control signaling. This is sometimes referred to as “robbed-bit signaling” because the 8-Kbps bandwidth is “robbed” from the data channel for handling control functions such as wide area network (WAN) link synchronization. T1 lines that use switched channels also use in-band signaling techniques.
Graphic I-1. Comparison with out-of-band signaling.
A tool included with Microsoft Exchange Server that you can use to check and repair problems with personal folders and offline storage files in a messaging system that uses Microsoft Windows messaging clients (such as Microsoft Outlook). The Inbox Repair Tool is installed on clients that have Outlook installed. It is also included on the Windows 98 CD as the utility scanpst.exe.
How It Works
When you run the Inbox Repair Tool, it analyzes the .pst file’s directory structure and item headers and tries to recover all the folders and all the items in those folders. If it finds any errors, it attempts to recover the damaged items. It also creates a log file of the actions it has performed, which you can examine later for further information. The tool creates a new set of empty Outlook folders along with a Lost And Found folder that contains any folders and items it recovered from the .pst file. You can then create a new .pst file and drag the recovered folders and items to your new Personal Folders entry in your Outlook profile.
A backup type in which only selected files and folders that have changed since the last normal backup are backed up and the archive attribute is marked for each file and folder. You can use incremental backups in conjunction with normal backups to simplify and speed up the backup process. If you do a normal backup on one particular day of the week, you can perform incremental backups on the remaining days to back up only the files that have changed during each day of the backup schedule. Incremental backups are faster than normal backups and use less tape.
NOTE
Incremental backups are not cumulative, as differential backups are, so when you need to perform a restore, you need the normal backup and all incremental backups since the normal backup was done. Incremental backups are faster to perform but take longer to restore from.
See also backup type, differential backup
A method of updating zone information in newer implementations of the Domain Name System (DNS).
How It Works
Incremental zone transfer is a more efficient method of propagating zone updates than the earlier standard DNS method of transferring the entire zone file using the AXFR request. Incremental zone transfer is defined in Request for Comments (RFC) 1995 and uses the IXFR request to transfer only the minimal information needed to keep the DNS servers within a given zone of authority in synchronization.
In incremental zone transfer, every primary or master DNS server maintains a full copy of the up-to-date zone file plus an additional version history that records any changes to resource records that occurred during recent updates of the zone file. When a secondary DNS server makes an IXFR request to a primary or master DNS server, the master server compares the zone version number of the secondary server’s zone to its own current version number. The zone version number is the serial number stored in the start of authority (SOA) record of the DNS server. If the master server has a newer version number and incremental zone transfers are supported, the master server sends to the secondary server only those changes to resource records that have occurred in the time interval between the two version numbers. If the version numbers of the master and secondary servers match, no zone transfer takes place. And if incremental zone transfer is not supported, the normal full zone transfer takes place instead.
NOTE
Incremental zone transfers are supported as part of the dynamic update features of Microsoft Windows 2000.
A general-purpose presentation services protocol for Microsoft Windows operating system platforms. The Independent Computing Architecture (ICA) protocol was developed by Citrix for Citrix Winframe to run on Windows NT Server, and is implemented in Windows NT Server, Terminal Server Edition. ICA lets the user interface of an application run with minimal consumption of resources on a client device while the actual application logic executes on an ICA-enabled server. In this respect, ICA is similar to the X Windows protocol for UNIX platforms. The only data transferred between the server and the client device over the network are the user interface, keystrokes, and mouse movements. This results in minimal resource requirements for the client, allowing the use of a “thin client.” ICA also provides location independence because it runs the Windows NT Server operating system and application program at a centralized location while displaying the user interface on any supporting client.
The ICA protocol runs over most industry-standard networking protocols, such as TCP/IP, NetBEUI, IPX/SPX, and Point-to-Point Protocol (PPP). It also runs over transport protocols such as Integrated Services Digital Network (ISDN), frame relay, and Asynchronous Transfer Mode (ATM). Users can access standard Windows applications running on a remote ICA-based server over dial-up, local area network (LAN), wide area network (WAN), or Internet connections. Applications can be launched from Web pages or from Windows desktops, making the ICA protocol a platform-independent solution.
A database object in relational databases that enables efficient and rapid access to data in the rows of a database table using key values. Indexes are created on columns in a Microsoft SQL Server database and provide a way to logically order rows in a database table. Because databases without indexes take much longer to query, planning and implementing indexes is an essential part of database design.
Indexes can also be used to enforce the uniqueness of rows in a database table by building the index on a key value.
TIP
Although using indexes generally speeds queries, it is not a good idea to have an index for every column because building the index takes time and requires additional disk space, plus modifying the contents of the database causes modifications to the index. You should only create indexes for the following:
Primary and foreign keys
Data on which you frequently issue search queries
Columns that are often retrieved in a sorted order or are used in joins
See also Index Tuning Wizard
An optional component of the Microsoft Windows 2000 Server operating system platform that enables the indexing of contents and properties of documents on Internet or intranet sites hosted using Internet Information Services (IIS). On the earlier Windows NT Server platform, this component was called Index Server and was included as part of the Windows NT Option Pack. The features of the Indexing Service include the following:
Support for indexing of multiple IIS servers, Windows NT and Windows 2000 file servers, and Novell NetWare file servers
Extensible support for multiple file formats, including ASCII text, Hypertext Markup Language (HTML), Microsoft Word, Microsoft Excel, Microsoft PowerPoint, and third-party file formats that use content filters
Multiple-language support for both indexing and querying, including language shifts within a document
Support for indexing newsgroup content on an IIS 4 server running the NNTP Service
Zero-maintenance design, including automatic reindexing and error detection and recovery
How It Works
Indexing Service (which runs as the Content Index service in Windows NT) automatically indexes new documents as you add them to your Web sites on IIS. It begins by scanning the new documents and using content filters to generate a stream of text from them. Then it enlists word breakers to divide the text stream into words, after which the normalizer removes noise words and punctuation. It compiles the resulting words into word lists, which it merges into persistent indexes. Finally, it conducts a master merge to create a master index, which it stores in an Indexing Service catalog. The master index is the most efficient way to store indexing information.
Administrators can use the Indexing Service snap-in for the Microsoft Management Console (MMC) to view the status of the indexing process and to configure catalogs. Although the entire indexing process runs automatically, administrators can use the MMC to force a scan or a merge if necessary.
You can create and configure an HTML query form to issue queries against Indexing Service catalogs by using one of the following:
Internet Data Query (IDQ) files and HTML Extension (HTX) files
Active Server Pages (ASP) scripting
SQL queries that use Microsoft ActiveX Data Objects (ADO)
A wizard in Microsoft SQL Server version 7 that you can use to select and create an optimal set of indexes and statistics for a database. The Index Tuning Wizard lets you optimize your database’s indexes even if you do not understand the structure of the database or the internal workings of SQL Server.
How It Works
The wizard uses a workload to build a recommended optimal set of indexes for your database. A workload is a SQL script or a trace created using SQL Server Profiler. It contains SQL batch or remote procedure call (RPC) event classes and data columns called Event, Class, and Text. The workload profiles the normal activity of your database and allows the wizard to analyze it to determine which index configuration will optimize performance of your database. The result of running the wizard is a set of Structured Query Language (SQL) statements that you can use to create new indexes and remove existing ones. You can implement these recommendations immediately, save them to a SQL script for later use, or schedule their execution as a SQL Server job.
The wizard can recommend the best set of indexes to use for a given workload, recommend how you can tune your database for a small group of problem queries, and let you analyze the effects of proposed alterations, such as distributing queries among different tables.
NOTE
If you don’t have enough data in your database tables or if your existing set of indexes is optimal, the Index Tuning Wizard cannot produce a recommendation for you.
One of the four core components of Microsoft Exchange Server. The information store consists of two databases that store Exchange messaging content:
The public information store, which stores content for public folders hosted on the server
The private information store, which stores users’ mail folders, messages, and attachments for users whose home directories are on the server
The information store is implemented as a Microsoft Windows NT service or a Microsoft Windows 2000 service and can be accessed by
Messaging clients based on Microsoft Messaging Application Programming Interface (MAPI), such as Microsoft Outlook
Post Office Protocol version 3 (POP3) clients, such as Microsoft Outlook Express
Network News Transfer Protocol (NNTP) clients, such as Outlook Express
The information store stores its message content using the Exchange message database encoding format (MDBEF). MAPI clients can access this format directly, but non-MAPI clients require conversion of MDBEF format information to their own messaging format—such as Simple Mail Transfer Protocol (SMTP) or X.400.
TIP
An Exchange Server can have a private information store, a public information store, or a private and a public information store. This provision for creation or deletion of information stores allows you to load-balance demand on servers by creating dedicated messaging or dedicated public folder servers in your sites.
An international consortium of hardware and software manufacturers that creates and promotes interoperable solutions for infrared (IR) data networking for computer networks, communication, and other networking applications. The Infrared Data Association (IrDA), which was formed in 1993, has over 150 members from hardware, software, and communication sectors. It has developed and agreed on standard formats for communication between computers and infrared devices to ensure interoperability between different systems, platforms, and devices. The IrDA also schedules meetings, conferences, and other events relating to infrared networking technologies. IrDA standards include the IrDA Data and IrDA Control infrared communication standards.
On the Web
•
IrDA home page : http://www.irda.org
See also infrared transmission, IrDA Control, IrDA Data
A Microsoft Windows 98 utility for managing a computer’s connectivity to devices that use infrared (IR) communication technology. To activate Infrared Monitor on your system, use the Infrared utility in Control Panel or the icon in the system tray of the taskbar when you use an infrared device. You can use Infrared Monitor for the following tasks:
Determining which infrared devices are within the range of your system
Determining which infrared devices are currently in communication with your system and the status of those communications
Reporting on the status of infrared activity and all connected infrared devices
Enabling or disabling infrared services on a serial port
Configuring the maximum transmission speed to tune performance
Configuring sounds for signaling different infrared device status situations
TIP
By limiting the maximum transmission speed for infrared communication, you might be able to improve communication between your system and its infrared-enabled peripherals. Try a connection speed of 19.2 Kbps and gradually work upward.
See also Infrared Data Association (IrDA), infrared transmission
The transmission of data or voice information over infrared (IR) light. Infrared data transmission is often used to connect laptops or Personal Digital Assistants (PDAs) to peripherals (such as printers) or to desktop computers for synchronizing work files. The most popular computer industry standard for infrared transmission is the IrDA Data standard developed by the Infrared Data Association (IrDA).
How It Works
IR is light that is beyond the red end of the visible spectrum. Wavelengths in the range of 770 to 1400 nanometers are called the near infrared region of the electromagnetic spectrum, while longer wavelengths are called the far infrared. An IR transducer consists of a driver and an IR emitter that can both transmit and receive infrared transmissions. The transducer is connected to an encoder/decoder that interfaces with the computer or peripheral’s universal asynchronous receiver-transmitter (UART) for asynchronous serial transmission between the devices.
IrDA devices that use the IrDA Data protocol suite initiate a connection using the discovery functions of the Infrared Link Management Protocol (IrLMP) and establish the primary and secondary stations using the Infrared Link Access Protocol (IrLAP). The secondary station then adjusts its data speed to match the primary station and establishes a serial communication link.
TIP
Remember that IrDA devices have severe distance limitations and require a direct line of sight between them in order to communicate, and that outdoor communication can be adversely affected by fog and other bad weather.
A feature in the security framework of Microsoft Windows NT and Windows 2000 that allows the access control entry (ACE) for an object whose security settings are being configured to be propagated to other objects that are beneath it in the file system or directory hierarchy. In Windows NT, inheritance is used in the NTFS file system for propagating the permissions assigned to a folder to the files and folders within that folder. In Windows 2000, inheritance also applies to Active Directory and allows permissions assigned to a container or an organizational unit (OU) within Active Directory to be propagated further down the directory tree. Inheritance also appears in other directory-based systems such as Microsoft Exchange Server, in which Exchange administrative permissions assigned to a container in the Exchange directory that is based on the Lightweight Directory Access Protocol (LDAP) can be applied to leaf objects and other containers within that container.
Inheritance simplifies the administration of hierarchical file systems and directories by allowing administrators to configure ACEs globally and then modify them on an exception basis, rather than configure ACEs individually for each object in the system.
See also delegation, discretionary access control list (DACL), permissions
A series of initialization files used in Microsoft Windows 3.1 and Windows for Workgroups that store configuration information about hardware, devices, and services on the computer. These text files, which have the extension .ini, include
WIN.INI, which stores information about the desktop environment, fonts, and printers, as well as other settings
SYSTEM.INI, which stores boot settings and information specific to running in Standard and 386 Enhanced modes
CONTROL.INI, which maintains the Windows color schemes
PROGMAN.INI, which stores information about program groups
WINFILE.INI, which stores status information for File Manager
In addition, individual applications often create their own INI files during installation to store application-specific settings.
NOTE
Instead of using INI files, Windows 95, Windows 98, Windows NT, and Windows 2000 store all configuration settings in the registry. Most of these files are also included in these operating systems to provide backward compatibility for running 16-bit Windows programs, because such programs were designed to save their settings in INI files and cannot access the registry.
A particular occurrence of a Microsoft Windows NT Performance Monitor (System Monitor in Windows 2000) counter. For example, if the %Privileged Time counter is being monitored for the Processor object on a symmetric multiprocessing (SMP) machine with four processors, individual instances of that counter are instances 0, 1, 2, and 3. By using instances, you can monitor the performance of processes, threads, and devices on a per-instance basis for detailed understanding of their resource use on a machine. Individual instances of a given counter can be displayed in the usual way using charts and graphs.
An Internet technology for sending short messages to other users who are online. The concept of instant messaging started in early networked UNIX environments; users who were logged on could use commands such as talk, write, and finger to determine who else was logged on and to send them messages. However, the term “instant messaging” now generally applies to a technology popularized by America Online (AOL) and supported by Microsoft and other companies.
How It Works
AOL users can send instant messages to other AOL users online by using client software called AOL Instant Messenger (AIM). To use AIM, a user signs on at an AOL central server, indicating that he or she is online and can receive instant messages from other users. The central server records the user’s IP address for that session. (The user’s IP address is assigned by Dynamic Host Configuration Protocol [DHCP] and can vary from session to session.) Other users can then send instant messages to that user via the server. The user’s AIM client sends the server a copy of the user’s “buddy list” (a list of other users that he or she frequently exchanges messages with), and the server responds by telling the user which buddies are currently online and can receive messages. The user can select a buddy from the list and submit a message to the server, which forwards the message to the buddy.
Graphic I-2. The instant messaging system used by AOL.
NOTE
Microsoft has an instant messaging client called MSN Messenger Service. An Internet Engineering Task Force (IETF) working group is developing a standard for an Instant Messaging and Presence Protocol (IMPP) to make sure that instant messaging offerings from different vendors are fully compatible with each other. Microsoft plans to ensure that its instant messaging clients and servers support IMPP.
A worldwide nonprofit association of technical professionals that promotes the development of standards and acts as a catalyst for new technology in all aspects of the engineering industry, including computer networking, telecommunications, electric power, aerospace, and consumer electronics. The Institute of Electrical and Electronics Engineers (IEEE) has more than 330,000 individual members in 150 countries. Its activities include standards committees, technical publishing, and conferences.
A major contribution of the IEEE in the field of computer networking is Project 802, a collection of standards for local area network (LAN) architectures, protocols, and technologies. These standards continue to evolve under the auspices of various IEEE working groups and committees.
On the Web
•
IEEE home page : http://www.ieee.org
A telecommunications service provider that offers one-stop shopping for voice and data telecommunications through a single integrated architecture. Use of an integrated communications provider (ICP) can save companies a considerable amount of money compared to leasing the services separately from Regional Bell Operating Companies (RBOCs), competitive local exchange carriers (CLECs), or incumbent local exchange carriers (ILECs).
How It Works
The main difference between an ICP and a traditional carrier service provider is that an ICP generally installs a single, all-in-one integrated access device (IAD) at the customer premises that enables voice and data traffic to be serviced over a single line. This provides for easier management than using multiple lines with different technologies and devices. The IAD connects to the provider by using an Asynchronous Transfer Mode (ATM) connection over a single T1 line or Digital Subscriber Line (DSL) circuit at the local loop. (About 80 percent of the customer cost for ICP services is for the ICP’s rental of local loop access from an RBOC). At the provider end, many ICPs are building their own integrated ATM backbone networks so that they can better control the services they offer.
TIP
While the cost of using an ICP might be less than that of using an RBOC or a CLEC, the ICP might not offer some services, such as toll-free long distance and DSL services. You should also be sure that you understand how the various services are billed before you sign a contract.
Some ICPs use time-division multiplexing (TDM) to allow a single T1 line to carry voice, data, and video over 24 DS0 (Digital Signal Zero) channels. In this scenario, you might be paying for bandwidth that you are not using, because TDM dedicates slots of bandwidth to services whether or not data is being carried in these slots. You can generally get better value from ICPs that use ATM circuits between the subscriber and provider because ATM can use statistical multiplexing, which allocates bandwidth dynamically between voice and data. However, the disadvantage of the ATM approach is that if the line goes down, all voice and data transmission is interrupted, while with the TDM approach, customers might still have access to analog phone lines if such lines are used.
Graphic I-3. Integrated communications provider (ICP).
A digital communication service provided by telcos. Integrated Services Digital Network (ISDN) is an all-digital dial-up (on-demand) service that can simultaneously carry high-quality voice, data, and video transmissions over existing Plain Old Telephone Service (POTS) telephone wires of the subscriber’s local loop connection at speeds of 128 Kbps or higher. Even higher speeds can be reached using data compression.
How It Works
ISDN is supplied to the customer premises over standard POTS 4-wire twisted-pair wiring and uses time-division multiplexing (TDM) to send three channels of data (two B channels and one D channel) over a single communication line (two copper wires). Up to eight data terminal devices (such as computers, telephones, and fax machines) can be connected to a single ISDN line. You can set up different data rates based on your local telephone company’s services.
ISDN has its own framing or encapsulation format called V.120, which is the international standard for synchronous ISDN data stream framing. ISDN frames are 48 bits long and are transmitted at 4000 frames per second. Each ISDN frame contains two 8-bit slots for the B1 channel and two 8-bit slots for the B2 channel, which alternate with each other and with one 1-bit D channel slot after each B channel slot. Each B channel thus provides a data transfer rate of 2 x 8 bits x 4000 Hz = 64 Kbps, while the D channel has a bandwidth of 4 x 1 bits x 4000 Hz = 16 Kbps. The remainder of the frame is used for line balancing, echo detection, activation, and padding.
The two basic types of channels in an ISDN service are
B (bearer) channels, which are used for carrying either voice or data. The data transmission can be either packet-switched (such as X.25) or circuit-switched (telco) services. Each B channel in an ISDN service is completely separate, but you can use a protocol called Bandwidth On Demand Interoperability Group (bonding) to dynamically join the two B channels in a typical Basic Rate Interface ISDN (BRI-ISDN) service using inverse multiplexing to produce a single 128-Kbps data channel.
D (delta) channels, which are control channels for setting up connections and for other signaling purposes. For example, ISDN voice communication uses D channels to implement call forwarding and call display services. The D channel uses a completely separate telco communication network called the Signaling System 7, or SS7. This out-of-band telco network is used exclusively for system overhead signaling for ISDN and digital data service (DDS) services, and it makes possible the low latency of ISDN dial-up connections. For example, it takes only 1 to 2 seconds for an ISDN dial-up connection to be established, compared to 15 to 45 seconds for a typical analog modem. D channels can also be used to connect to an X.25 network.
The two most common ISDN interfaces or service types available from local carriers are
Basic Rate Interface (BRI), which consists of two 64-Kbps B channels and one 16-Kbps D channel. BRI is also referred to as 2B+D service. This is the most common configuration and provides up to 128 Kbps data throughput in dial-up connections to a switch or ISDN Private Branch Exchange (PBX) at the telco’s central office (CO).
Primary Rate Interface (PRI), which consists of twenty-three 64-Kbps B channels and one 64-Kbps D channel. PRI is also referred to as 23B+D service and is analogous to T1 services in carrying capacity.
ISDN lines terminate at the customer premises using an RJ-45 connector in a configuration called a U interface, which is usually connected to a Network Termination Unit (NTU). The NTU can then directly connect to special ISDN phones or network interface cards (NICs) in computers using the standard ISDN S/T interface. Alternatively, the U interface on the ISDN line can be connected directly to an ISDN terminal adapter, which interfaces the ISDN line with non-ISDN computer equipment and POTS telephones or fax machines. ISDN terminal adapters are sometimes called ISDN modems, but they are not really modems because ISDN is an end-to-end digital communication service.
Graphic G-4. Integrated Services Digital Network (ISDN).
NOTE
You can use the ISDN Configuration Wizard in Microsoft Windows 98 to configure your ISDN hardware. Some telcos provide only 56-Kbps B channels instead of 64 Kbps for ISDN, and ISDN is not always available in rural areas. ISDN charges usually include both monthly fees and usage charges per minute, although usage charges are sometimes waived.
TIP
Plug your ISDN network termination device into an uninterruptible power supply (UPS) so that you can use the phone during a power failure and so that your wide area network (WAN) link doesn’t go down. If you have a large company and expect a lot of local telephone calls within your organization, you can sometimes obtain a Centrex ISDN service in which local calls have no usage charges. The Windows NT, Windows 2000, Windows 98, and Windows 95 operating systems have built-in support for ISDN.
Tips for Troubleshooting ISDN
| Problem | Suggestions |
| ISDN router or terminal adapter fails to dial | Check the cabling, the line signal, and the dialer map on the router. |
| Dial fails to go through on a BRI line | Be sure that you are using a straight-through RJ-45 cable. Check other cables, make sure the speed is set correctly to 56 or 64 Kbps as necessary, verify the phone number and service profile identifier (SPID) assigned by the service provider, and check the router hardware. |
| Dial fails to go through on a PRI line | Be sure that you are using a straight-through DB15 cable and that the speed is set correctly to 56 or 64 Kbps as necessary. Check the dialer map on the router, the phone number of the remote PRI, and the status lights and framing on the Channel Service Unit (CSU). Power-cycle the CSU. |
| Dial is successful but cannot ping the remote router | Check the Point-to-Point Protocol (PPP) configuration (if used). Check the routing table and add a static route if necessary. Check that the dialer map has the correct remote router specified, and have the telco check the remote router configuration. |
See Windows NT Challenge/Response Authentication
See x86 platform
A hub that is enabled for remote monitoring and management through Simple Network Management Protocol (SNMP). An intelligent hub contains Management Information Base (MIB) information that specifies which conditions can be monitored and which functions can be managed. These functions can include the following:
Setting alerts on problem conditions such as excessive collisions
Isolating and disconnecting problem computers
Providing network statistics to remote management consoles
Intelligent hubs are usually managed using in-band signaling methods, but they usually offer out-of-band management functions as well, such as being managed by a remote Telnet connection. Some stackable hubs have separate SNMP modules that you can purchase and install to provide manageability.
See also hub
A hardware architecture developed by a consortium led by Intel that improves the input/output (I/O) performance of systems by relieving the central processing unit (CPU) of interrupt-intensive I/O tasks. Intelligent Input/Output (I2O) also provides a way of standardizing I/O device drivers across different operating systems and hardware platforms.
How It Works
I 2O makes use of a separate I2O processor such as the Intel i960 series of processors. This enables the CPU to offload interrupts received from peripherals to the I2O processor for handling. This scheme can improve the performance of servers by as much as 30 percent.
I2O also standardizes device drivers by dividing them into two components:
A Hardware Device Module (HDM), which directly interfaces with the peripheral being managed
An Operating System Service Module (OSM), which interfaces with the operating system on the machine
In addition, an intermediate layer between the HDM and OSM provides independence between them by providing standard communication mechanisms that allow any HDM for any peripheral to interoperate with any OSM for any operating system.
NOTE
The Windows 2000 operating system supports I2O.
On the Web
•
I2O Special Interest Group (SIG) home page : http://www.i2osig.org
A set of management technologies native to Microsoft Windows 2000 that simplifies the task of configuring and maintaining applications, settings, and data at the client and server level. IntelliMirror provides a distributed replication service that lets clients and servers “intelligently mirror” and share information stored on local and distributed file systems. IntelliMirror mirrors the workstation environment on the network server so that the environment can be easily managed. IntelliMirror also offers full roaming support by allowing a user to log on to any client machine and access his or her software, settings, and data. IntelliMirror is designed to simplify network administration and eliminate the need for administrators to “visit” desktop clients to upgrade operating systems and applications.
IntelliMirror uses Remote Installation Services to enable authorized clients to download fully configured operating systems, applications, and data from remote servers, thus performing unattended installations on the clients. IntelliMirror technologies will significantly reduce the total cost of ownership (TCO) of PC-based networks.
A built-in identity in Microsoft Windows 2000 and Windows NT that includes any user who has successfully logged on to the local server console. The operating system uses this group to enable the user who is logged on locally to access resources on the computer. The name “Interactive” stems from the idea that the user who belongs to this group is “interacting” with the local computer through the console.
As with all system groups, administrators cannot directly modify membership in the Interactive group or the rights of the Interactive group.
See also built-in identities
A logon process whereby the user gains access to the network by entering a username and password in response to a dialog box on the local console. This is in contrast to a remote logon, which occurs when a user who is already logged on locally tries to make a network connection to a remote computer—for example, using the net use command at the command prompt. Interactive logons are supported by all versions of Microsoft Windows.
In a Windows 2000 or Windows NT network, the information that the user must specify during an interactive logon depends on the network’s security model, as described in the following table. After successfully logging on interactively, the user is granted an access token that is assigned to the initial process created for him or her.
Required Logon Information for Security Models
| Security Model | What the User Must Specify |
| Workgroup | Username and password |
| Domain | Username and password |
| Domain with a trust relationship trusting other domains | Username, password, and domain |
NOTE
When trust relationships are configured between Windows 2000 and Windows NT domains, the interactive logon dialog box allows the user to select a logon domain—that is, the domain in which the user’s user account is located. In contrast, the Windows 95 and Windows 98 logon domains are hard-coded using Client for Microsoft Networks and offer only one domain to choose from at logon time.
See also automatic logon
A telco that mainly provides long-distance communication services. Inter-exchange carriers (IXCs) own or share the various high-bandwidth, fiber-optic trunk lines that cross the country and provide high-speed switched digital services for voice, data, and video communication. About 90 percent of the U.S. long-distance communication market is controlled by the IXCs AT&T, MCI WorldCom, and Sprint.
Local telephone service to subscribers is primarily the domain of local exchange carriers (LECs) such as the Regional Bell Operating Companies (RBOCs). However, the Telecommunications Act of 1996 has opened up the market so that LECs can compete in long-distance markets by leasing services from IXCs, and IXCs can compete in local markets by leasing local loop connections from LECs. Some companies have also gained access to each other’s services by merging. Other emerging competitors for IXCs are cable television companies, who have customer premises installations in most U.S. residences and who are upgrading their networks for bidirectional communication.
In networking and communication, a standard or mechanism for transferring data from one device to another. An interface specifies the nature of the boundary between two devices and determines the procedures and protocols that make it possible for the devices to exchange data.
Graphic I-5. An example of an interface between DTE and DCE devices.
The two main types of networking and communication interfaces are as follows:
Serial interfaces, which transfer data one bit at a time. The most common serial interface is the RS-232 interface.
Parallel interfaces, which transfer data several bits at a time, usually one or more bytes at a time. The most common parallel interface is the one used for connecting printers to computers, which uses a female DB-25 or 36-pin Centronics connector.
The following table shows some common examples of serial interfaces used in networking. Serial interfaces are commonly used for connecting data terminal equipment (DTE), such as computers or routers, to data communications equipment (DCE), such as modems or CSU/DSUs (Channel Service Unit/Data Service Units).
Serial Interfaces for Networking
| Serial Interface | Description |
| RS-232 | A common interface for communication over unbalanced lines. Uses DB-9 or DB-25 connectors. |
| RS-422/485 | For communication over balanced lines. More suitable than RS-232 for environments with significant electromagnetic interference (EMI) or with DB-9 or DB-37 connectors. |
| V.35 | A high-speed serial interface for data transmission at 48 Kbps. Combines balanced lines with unbalanced lines and is used in Integrated Services Digital Network (ISDN) and frame relay connections. Uses a 24-pin block connector. |
| X.21 | A high-speed serial interface that uses the International Telecommunication Union (ITU) standard for connecting DCE and DTE for synchronous communication. Uses a DB-15 connector. |
NOTE
The type of interface a device uses is related to the kind of connector or cable used to connect to the device, but not in a one-to-one fashion. For example, you could say that a device has an RS-232 serial interface, but it is incorrect to say that you use an RS-232 connector or an RS-232 cable to connect to that device. RS-232 specifies the interface, but several cabling options can support it, such as a cable terminated with a DB-9 or a DB-25 male connector.
The term “interface” is also used in routing terminology, in which it describes the connection between a router and an attached network.
See also connector (device)
Any card that you plug into the motherboard of a computer to support connectivity between the main system bus and the external serial or parallel bus. Computers usually come with installed serial/parallel interface cards for connecting modems, printers, and other devices to your system, but in certain situations you might want to purchase a separate interface card. These situations include
When you have an older computer whose serial interface card cannot support the newer fast 56-Kbps V.90 modems or whose parallel interface card cannot support IEEE 1284 bidirectional print devices such as the newer Hewlett Packard LaserJet print devices
When you need a different serial interface such as RS-422/485 to connect your machine to special networking or industrial measurement equipment
Many different kinds of interface cards are available, including the following:
RS-232 high-speed serial input/output (I/O) cards with 16550 universal asynchronous receiver-transmitter (UART) chips for connecting to high-speed modems and Integrated Services Digital Network (ISDN) terminal adapters. These cards can be either Industry Standard Architecture (ISA) or Peripheral Component Interconnect (PCI) bus cards and can support transfer speeds of up to 460.8 Kbps—much higher than the 115.2-Kbps rate supported by standard RS-232 interfaces.
Enhanced Capabilities Port (ECP)/Enhanced Parallel Port (EPP) high-speed parallel I/O cards that support up to 2.5-Mbps transfer speeds.
RS-422/485 interface cards for connecting to industrial sensor and measuring equipment. These cards can support up to 31 separate devices that can be located up to 4000 feet from the computer. Data transfer speeds are up to 460.8 Kbps.
Any device that converts one hardware interface to another. These devices are generally stand-alone, powered devices for midline use or rack-mounted devices for use in wiring closets. There are interface converters for serial and parallel interfaces, asynchronous and synchronous communication, half-duplex and full-duplex communication, single-node and host converters, copper and fiber-optic converters, AC-powered or interface-powered devices, and so on. Examples of interface converters include the following:
Graphic I-6. A network that uses an interface converter to convert between RS-232 and V.35.
RS-232 to RS-422 serial interface converters for directly connecting the RS-232 serial interface of a computer to an RS-422 programmable logic controller for synchronous data transmission. If handshaking is required, you should use an RS-232 to RS-422/449 serial interface converter instead.
RS-232 to RS-422/485 serial interface converters that allow RS-422/485 data collection equipment or industrial measurement devices to be connected to a computer using its built-in RS-232 serial interface. Alternatively, you can install an interface card in the computer to allow it to connect directly with the RS-422/485 device.
RS-232 to V.35 serial interface converters for connecting RS-232 devices to V.35 lines.
V.35 to G.703 or X.21 serial interface connectors for use in Europe.
Small Computer System Interface (SCSI) to parallel converter for connecting SCSI peripherals to an Enhanced Capabilities Port (ECP)/Enhanced Parallel Port (EPP) parallel port.
See electromagnetic interference (EMI)
A type of routing protocol used for distributing routing information within autonomous systems in large internetworks based on the TCP/IP protocol (such as the Internet).
How It Works
Interior Gateway Protocols (IGPs) specify how routers within an autonomous system (AS) exchange routing information with other routers within the same autonomous system. This is in contrast to Exterior Gateway Protocols (EGPs), which facilitate the exchange of routing information between different autonomous systems.
Examples of IGPs for TCP/IP internetworks include the following:
Routing Information Protocol (RIP) for Internet Protocol (IP), which is based on the distance-vector algorithm. RIP is a popular protocol for small to medium-sized internetworks.
Open Shortest Path First (OSPF) Protocol, which is based on the link-state algorithm. OSPF is used mainly on medium to large-sized internetworks.
Interior Gateway Routing Protocol (IGRP), a distance-vector protocol developed by Cisco Systems.
Graphic I-7. A network using IGP to route information within an autonomous system and EGP to route information between autonomous systems.
NOTE
Microsoft Windows NT version 4 with the Routing and Remote Access Service (RRAS) installed and Windows 2000 with Routing and Remote Access installed support RIP for IP and for OSPF.
Any networking device positioned between a Remote Access Service (RAS) server and a RAS client. Intermediary devices are third-party devices for performing security-related tasks such as authentication, encryption, and other functions. RAS on Microsoft Windows NT Server and on Windows 2000 Server supports intermediary devices.
How It Works
An intermediary device such as a security host can be positioned between a RAS server and its modem pool. Clients connecting to the modem pool must be authenticated by the security host before they can establish a connection with the RAS server. The security host thus provides an extra layer of security for remote access to the network. The security host might prompt the user for credentials, or the user might be required to use a security card to gain access to the network.
Graphic I-8. A security host as an intermediary device between a RAS server and a client.
TIP
Once you have configured RAS on Windows NT Server to work with intermediary devices such as third-party security hosts, you must then configure the client to work with the device. You can typically do this by activating terminal mode on the client so that it can respond to the special prompts issued by the device.
An initiative of the International Telecommunication Union (ITU) to create a global standard for wireless data networks. The goal of International Mobile Telecommunications-2000 (IMT-2000) is to support data transmission rates of up to 2 Mbps for fixed stations and 384 Kbps for mobile stations. Note that the “2000” in the term “International Mobile Telecommunications-2000” refers to the transmission speed (approximately 2000 Kbps), not the deployment date (which might be several years beyond the year 2000).
IMT-2000 consists of several sets of standards, including the following:
CDMA2000: A proposed hardware upgrade to the existing Code Division Multiple Access (CDMA) cellular phone systems used in the United States and in some parts of Asia
W-CDMA: A proposed upgrade to Global System for Mobile Communications (GSM) networks that provides an alternative air interface to CDMA2000 for upgraded CDMA systems in Europe and Japan
Universal Mobile Telecommunications System (UMTS): A standard for 3G (third-generation) wireless networks proposed by the European Telecommunications Standards Institute (ETSI)
Universal Wireless Communications (UWC-136): A standard for 3G wireless networks proposed by the Telecommunications Industry Association (TIA)
Because of the fundamental inoperability between the two major types of cellular communication technologies—Time Division Multiple Access (TDMA) and CDMA—the ITU hopes that this initiative will unify wireless mobile communication worldwide by upgrading both TDMA and CDMA systems to a single global standard. However, the IMT-2000 initiative will not immediately result in a single worldwide air interface for wireless communication.
The upgrade for CDMA bearers will be simpler and will move them directly from the current IS-95a standard called CDMAone (the brand name used by the vendor consortium called the CDMA Development Group for existing data transmission at 16 Kbps) to the proposed CDMA2000. The upgrade for TDMA bearers can take several different paths—for example, from TDMA to General Packet Radio Service (GPRS) to Enhanced Data Rates for Global Evolution (EDGE) to UMTS. Some industry watchers predict that GPRS and IMT-2000 will be widely adopted worldwide in the next five years, which will give Europe and Asia an edge in high-speed wireless data communication over the United States, where as many as five competing systems might be deployed widely.
NOTE
3G wireless communication systems are those that provide transmission quality similar to Integrated Services Digital Network (ISDN) phone systems. First-generation systems are the analog cellular phone systems such as the Advanced Mobile Phone Service (AMPS) in North America, and second-generation systems are widely used digital cellular phone systems such as the Digital Advanced Mobile Phone Service (D-AMPS), CDMA systems, TDMA systems, and GSM.
On the Web
•
IMT-2000 home page : http://www.itu.int/imt/
See also CDMA2000, Universal Mobile Telecommunications System (UMTS), Universal Wireless Communications (UWC-136)
A nongovernmental organization based in Geneva, Switzerland, that has representatives from about 130 countries and is responsible for developing a variety of international standards in science and engineering. The International Organization for Standardization (ISO), established in 1947, runs almost 3000 different working groups and committees covering a broad range of standards issues. The ISO’s goals are to develop cooperation in scientific, technological, intellectual, and economic activities and to facilitate the international exchange of goods and services. The ISO includes member agencies in more than 30 countries. These member agencies include the American National Standards Institute (ANSI) and the European Computer Manufacturers Association (ECMA).
ISO standards include the following:
Open Systems Interconnection (OSI) reference model for networking
ISO/IEC SQL-92 standard for the transact-SQL language
ISO codes for photographic film speeds
ISO 9000 framework for business-management and quality-assurance standards
ISO 216 international standard paper sizes
Standards for telephone and bank cards
ISO international country codes and currency codes
TIP
If you plan to modify the schema of Active Directory for Microsoft Windows 2000 and create new classes or attributes, you must obtain a unique object identifier for your enterprise to ensure that your new classes and attributes do not conflict with those defined by other directory services. This is especially important in a heterogeneous networking environment with multiple interoperating directory services such as Active Directory, Novell Directory Services (NDS), an X.500-based directory service, or Simple Network Management Protocol (SNMP). You can contact the ISO to receive an object identifier for your organization and then subdivide your object identifier space as you desire and assign object identifiers to your new classes and attributes.
An international organization headquartered in Geneva, Switzerland, that coordinates global telecommunications networks and services with governments and the private sector. Known until 1993 as the International Telegraph and Telephone Consultative Committee (CCITT), the International Telecommunication Union (ITU) is responsible for a number of important international networking and communication standards, including the following X series and V series standards:
X.25 packet-switching network standard
V.90 56-Kbps modem standard
X.400 message-handling system (MHS) standard
X.435 standard for electronic data interchange (EDI) over X.400
X.500 directory service recommendations
X.509 digital certificate and authentication standard
The ITU also hosts important study groups, meetings, and conferences and is a leading publisher of information on telecommunications technology and standards. The section of the ITU that is concerned with developing international standards for telecommunications is called the ITU Telecommunications Standardization Sector, or ITU-T.
On the Web
•
ITU home page : http://www.itu.int
The global TCP/IP public internetwork that originated in the ARPANET project of the U.S. Department of Defense in the 1970s. The original purpose of ARPANET was to create a wide area network (WAN) that would allow researchers at various defense and civilian research agencies to communicate with each other and to collaborate on projects. When ARPANET grew larger and an increasing number of civilian agencies such as universities and networking companies wanted access to it, administration of the network (now called the Internet) was given to the National Science Foundation (NSF) and then to Internet Network Information Center (InterNIC).
The backbone networks that make up the Internet are owned and managed by private companies, including MCI WorldCom and Sprint. These companies often share physical lines and often lease lines from Regional Bell Operating Companies (RBOCs). Backbone lines on the Internet are linked at points called Network Access Points (NAPs), where Internet service providers (ISPs) can exchange traffic. Examples of NAPs include MCI WorldCom’s “MAE West” NAP in San Jose, California, and the company’s “MAE East” NAP in Washington, D.C. An ISP leases a point of presence (POP) connection to a backbone’s network in order to supply individual users and companies with Internet services. See the Web link in this entry for topological and descriptive views of the architecture of the Internet.
The Internet is not owned by any one group; it is a collection of networks and gateways that run a common TCP/IP protocol and that all evolved from ARPANET. Nevertheless, various administrative bodies oversee various aspects of the Internet. These groups include the following:
Internet Society (ISOC), which coordinates a number of other bodies and gives advice and direction to them.
Internet Architecture Board (IAB), which is responsible to the ISOC and oversees the architecture of the Internet.
Internet Engineering Task Force (IETF), which is responsible to the IAB and develops Internet protocols that define the TCP/IP protocol suite, the Domain Name System (DNS), and so on.
Internet Assigned Numbers Authority (IANA), which is soon to be replaced by the Internet Corporation for Assigned Names and Numbers (ICANN). IANA is responsible for coordinating the registration of DNS names and assigning IP addresses.
Although a large number of Internet protocols currently support applications for users of the Internet, these services are constantly evolving, and many are rapidly disappearing as new services emerge. By far the most popular business uses of the Internet are the World Wide Web (WWW) and e-mail. Usenet newsgroups and Internet Relay Chat (IRC) are also popular.
On the Web
•
Atlas of Cyberspaces : http://www.cybergeography.org/atlas/atlas.html
A project of the University Corporation for Advanced Internet Development (UCAID) to develop a high-speed network for research and collaboration and for developing innovative applications for education. Internet2 is supported by more than 150 universities in the United States.
The Internet2 project is designed to create a leading-edge network for developing and testing new Internet applications for researchers. Its members consist of a collection of national, regional, and campus organizations whose networks are linked by new technologies and common research goals. Internet2 is not a successor to the present Internet, but rather new technologies to be used as part of the Internet. Internet2 is being developed by a consortium of institutions working to improve on existing Internet technologies. The knowledge and new technologies developed using Internet2 will be made available to the broader Internet community as they emerge.
Some of the potential benefits of new Internet technologies include advances in areas such as telemedicine, digital libraries, and virtual laboratories. Internet2 will also provide researchers with a test bed for developing new networking technologies, such as the following:
Broadband networking
Quality of service (QoS) networking technologies
IPv6, the new 128-bit version of the Internet protocol
Multicasting technologies
NOTE
Other groups are working toward similar goals in cooperation with Internet2. Examples include the federally led NGI (Next Generation Internet) initiative, the National Science Foundation’s High Performance Connections program, and the MCI WorldCom vBNS network service.
On the Web
•
Internet2 home page : http://www.internet2.edu
A technical advisory group for the Internet Society (ISOC). The Internet Architecture Board (IAB) oversees the evolution of Internet protocols and standards. It was established in 1983 and currently consists of 13 voting members, 6 of whom are nominated by the Internet Engineering Task Force (IETF) and approved by the ISOC. IAB members are part-time volunteers who provide the IETF community with advice and support. The IAB’s functions include the following:
Overseeing the evolution of protocols for the architecture of the Internet
Overseeing the process for developing Internet standards and for managing and publishing the Request for Comments (RFC) series of standards documents
Providing guidance to the ISOC on technical and procedural matters relating to the Internet
Selecting and appointing the chair of the IETF and candidates for the Internet Engineering Steering Group (IESG) and the Internet Assigned Numbers Authority (IANA)
On the Web
•
IAB home page : http://www.iab.org
A U.S. government–funded organization that coordinates the assignment of unique Internet protocol parameters such as the IP address space and the Domain Name System (DNS). The Internet Assigned Numbers Authority (IANA) also delegates authority to other organizations and companies to grant users unique IP address blocks and register domain names. IANA is the ultimate authority for managing the root name servers that maintain the central database of information for the DNS. IANA also controls the assignment of TCP/IP protocol identifiers and numbers for autonomous systems on the Internet.
IANA operates under the auspices of the Internet Society (ISOC). It is also considered part of the Internet Architecture Board (IAB). IANA delegates the responsibilities for managing IP and DNS space to three regional bodies:
The American Registry for Internet Numbers (ARIN), which manages North America, South America, and sub-Saharan Africa
Réeseaux IP Européens (RIPE), which manages Europe and North Africa
The Asia Pacific Network Information Center (APNIC), which manages Asia and Australia
A new international nonprofit organization called the Internet Corporation for Assigned Names and Numbers (ICANN) will eventually take over the responsibilities of IANA because of the increasingly international and commercial nature of the Internet. ICANN will open up the registration and management of the DNS to commercial companies.
NOTE
Actual registration of IP addresses and DNS names is performed by network information centers, of which there are currently four in the United States:
Internet Network Information Center (InterNIC), which has exclusive authority over registering .com, .org, .net, .gov, and .edu top-level domains
The U.S. Domain Registration Service, which administers the .us top-level domain
The U.S. Department of Defense Network Information Center, which manages the .mil top-level domain
The .int top-level domain registry in Marina del Ray, California
On the Web
•
IANA home page : http://www.iana.org
A service included with Internet Connection Services for Microsoft Remote Access Service (RAS) that ships with Microsoft Windows NT 4.0 Option Pack and Microsoft Windows 2000. The Internet Authentication Service (IAS) provides authentication and authorization services for remote users who connect to their corporate network. System administrators can also use IAS to monitor connection usage for corporate accounting and billing purposes. IAS can record each authentication request and response, client logon time, client logoff time, and connection speed. This information can be stored and transferred to a database.
Graphic I-9. Internet Authentication Service (IAS).
How It Works
IAS uses the Remote Authentication Dial-In User Service (RADIUS) protocol, which allows a network access server (NAS) to forward requests for authentication over the Internet. In a typical implementation, a remote user dials in to a NAS at the user’s Internet service provider (ISP) using the Point-to-Point Protocol (PPP). The NAS receives the authentication request packets from the remote user, packages them into RADIUS packets, and forwards them to an IAS server on the private corporate network. The IAS server maintains the actual database of users who are allowed to log on to the company network remotely or uses the Security Accounts Manager (SAM) database on a corporate domain controller. Communication between the NAS and IAS servers involves a unique password called a “shared secret,” which secures the exchange of information between them and guarantees its integrity. If the user is authenticated by the IAS server, a packet is sent to the NAS to indicate this, and the NAS allows the user to establish a remote connection to the private corporate network.
IAS supports the Password Authentication Protocol (PAP), Challenge Handshake Authentication Protocol (CHAP), and Microsoft Challenge Handshake Authentication Protocol (MS-CHAP) methods for authentication through PPP.
A protocol developed in 1995 to allow arrays of proxy servers to communicate and work together over a network. Internet Cache Protocol (ICP) lets individual proxy servers query neighboring proxy servers to try to locate cached copies of requested objects. If these queries fail, the object is requested from the Internet. ICP has some inherent drawbacks:
ICP arrays use queries to determine the location of cached information, a process that generates additional network traffic.
ICP arrays have negative scalability—the more proxy servers in the array, the more query traffic is generated.
ICP arrays tend to become highly redundant, with each cache containing similar information (the URLs of the most frequently visited sites).
Microsoft’s solution to these problems is the Caching Array Routing Protocol (CARP), which it developed for Microsoft Proxy Server version 2.
A Microsoft Windows NT Option Pack add-on for Windows NT that corporations and Internet service providers (ISPs) can use to build comprehensive Internet access solutions such as dial-up virtual private networks (VPNs). Internet Connection Services for Microsoft Remote Access Service (RAS) can provide subscribers with seamless connections, global dial-up, and secure communication over the Internet to private networks. Internet Connection Services for RAS consists of three components:
Connection Manager Administration Kit (CMAK), which is used to configure Microsoft Connection Manager (CM)
Connection Point Services (CPS), which administrators can use to centrally manage network access phone book distribution
Internet Authentication Service (IAS), which allows users to be authenticated by the Windows NT Security Accounts Manager (SAM) database using the Remote Authentication Dial-In User Service (RADIUS) protocol
Using Internet Connection Services for RAS, you can
Provide secure remote access to a corporate private network using a Windows NT–based server that has Point-to-Point Tunneling Protocol (PPTP) enabled
Provide a seamless connection experience for users connecting to the Internet or a VPN
Provide global dial-up networking services
Administer access to network access servers from a central location using RADIUS
A wizard included with Microsoft Windows and Microsoft Internet Explorer that makes it easy for users to connect their computers to the Internet. If you do not yet have an account with an Internet service provider (ISP), you can use the Internet Connection Wizard to select an ISP, sign up, and configure your computer for a new Internet account via modem. If you already have an account, the wizard can help you configure your account so that you can connect through a modem or a local area network (LAN).
Graphic I-10. Internet Connection Wizard.
For Internet Explorer 5.0, the Internet Connection Wizard is by default located in the Communications program group. From the Start menu choose Accessories, Communications, and then Internet Connection Wizard.
A TCP/IP network layer protocol used by routers and TCP/IP hosts for building and maintaining routing tables, adjusting data flow rates, and reporting errors and control messages for TCP/IP network communication. Internet Control Message Protocol (ICMP) is defined in Request for Comments (RFC) 792.
How It Works
ICMP uses connectionless Internet Protocol (IP) datagrams of various types for communicating control messages between hosts and routers on a TCP/IP network. The more common ICMP packets include the following:
Echo Reply (ICMP type 0): The ping command uses this packet type to test TCP/IP connectivity.
Destination Unreachable (ICMP type 3): Indicates that the destination network, host, or port cannot be reached.
Source Quench (ICMP type 4): Routers send this packet type when they cannot process IP traffic as fast as it is sent. A Source Quench message essentially means, “Slow down!” A Microsoft Windows NT or Windows 2000 host can respond to a Source Quench message by slowing down its rate of data transmission.
Redirect Message (ICMP type 5): Used to redirect the host to a different network path. This message essentially tells the router to override the entry in its internal routing table for this packet.
Echo Request (ICMP type 8): The ping command uses this packet type to test TCP/IP connectivity.
Time Exceeded (ICMP type 11): Indicates that the Time to Live (TTL) has been exceeded because of too many hops. The tracert command uses this message to test a series of routers between the local and remote hosts.
NOTE
When a multihomed machine running Windows NT is used as a router, it does not send Source Quench messages to the transmitting hosts if data is being received too quickly. Instead, it simply discards packets that can’t be buffered and processed.
TIP
ICMP redirects can modify a router’s routing table, so sometimes hackers try to subvert routers by issuing forged ICMP redirects in order to perform a denial of service attack. ICMP redirects are usually sent by routers only if all the following conditions occur:
The router is configured to generate ICMP redirects.
The incoming router interface for the packet is the same as the outgoing router interface.
The subnet of the source IP address is identical to the next-hop IP address.
The IP datagram is not source routed.
A nonprofit corporation that will take over the functions of the Internet Assigned Numbers Authority (IANA) and some other Internet-management organizations. The Internet Corporation for Assigned Names and Numbers (ICANN) will be responsible for such functions as
Allocating portions of the IP address space
Managing the Domain Name System (DNS), including developing new top-level domains and managing root name servers
Assigning Internet Protocol (IP) parameters
Until now, the U.S. company Network Solutions has exclusively managed the registration of domain names and has maintained the DNS database. ICANN will open up the process and allow competition in the DNS registration arena by creating guidelines for determining the following:
Who can function as a domain name registry
Policies on fees and privacy rights for domain name registries
How disputes will be resolved between domain name registries
What new top-level domain names will be allowed
On the Web
•
ICANN home page : http://www.icann.org
•
ICANNWatch : http://www.icannwatch.com
A Microsoft technology for linking database content to Web pages that predates the development of Microsoft Active Server Pages (ASP) technology. The Internet Database Connector (IDC) is typically used on Internet Information Services (IIS) to allow clients to use Web browsers to access data stored in a Microsoft SQL Server database.
How It Works
The IDC is a legacy solution for enabling Web browsers to access, read, and modify information in databases, but it is still viable for small environments with limited requirements. The IDC provides excellent performance using open database connectivity (ODBC) versions 3 and later.
The IDC itself is implemented on IIS as an Internet Server API (ISAPI) dynamic-link library (DLL) called Httpodbc.dll that uses ODBC to gain access to SQL databases. To use IDC, you must create the following:
A query file (.idc file) that specifies the data source name (DSN) of the SQL database to be connected to, the username and password that the client Web browser should use to connect and log on to the database, the template file to be used for formatting the results, the particular Structured Query Language (SQL) statements to be executed in the query, and so on.
A template or HTML Extension (HTX) file (.htx file) that specifies the Hypertext Markup Language (HTML) format in which database queries are to be returned to the client and that in effect creates the HTML results page from the result set of the SQL query that is performed.
TIP
Be sure that you have the DSN of the SQL database being accessed by the Internet Database Connector configured in ODBC as a System DSN, because the Internet Database Connector typically runs not as a user but as part of the operating system. Be sure that execute permissions are configured on the virtual directory where the .idc file is stored on IIS.
A text file with the extension .idq that defines the basic parameters for a Microsoft Index Server query. These parameters include the scope of the query and its restrictions (the words being searched for). The Internet Data Query (IDQ) file is the handler for the Hypertext Markup Language (HTML) query form used to issue the query. The result set generated by the IDQ file is formatted into HTML using an HTML Extension (HTX) file (.htx file) and returned to the user. Developing a query or search page for a Web site that can use Index Server involves creating three files:
The HTML form that presents the search page to the user
The IDQ form handler that executes the query
The HTX file that formats the results returned to the user
TIP
Although you can use Active Server Pages (ASP) scripting to issue and format Index Server queries, IDQ/HTX files offer better performance.
See also HTML Extension (HTX)
An international community of networking engineers, network administrators, researchers, and vendors whose goal is to ensure the smooth operation and evolution of the Internet. The Internet Engineering Task Force (IETF) receives its charter from the Internet Society (ISOC), and its daily operations are overseen by the Internet Architecture Board (IAB).
The work of the IETF is performed by a number of working groups who are dedicated to such aspects of the Internet as routing, operations and management, transport, security, applications, and user services. These working groups interact primarily through mailing lists and are managed by area directors who belong to the Internet Engineering Steering Group (IESG). Some working groups develop extensions and newer versions of familiar protocols such as Hypertext Transfer Protocol (HTTP), Lightweight Directory Access Protocol (LDAP), Network News Transfer Protocol (NNTP), Point-to-Point Protocol (PPP), and Simple Network Management Protocol (SNMP). Others develop new protocols such as the Common Indexing Protocol, Internet Open Trading Protocol, and the Internet Printing Protocol.
The working groups produce documents called Internet Drafts, which have a life span of six months, after which they must be deleted, updated, or established as a Request for Comments (RFC) document.
On the Web
•
IETF home page : http://www.ietf.org
See Microsoft Internet Explorer
A tool for preconfiguring and customizing Microsoft Internet Explorer version 4 and deploying it throughout an enterprise. The main component of the Internet Explorer Administration Kit (IEAK) is the IEAK Configuration Wizard, which is used to download, configure, and package Internet Explorer 4 components for distribution to users in the enterprise. Some of the features of the kit include
Automatic Version Synchronization (AVS) for notifying administrators when software updates for Internet Explorer 4 become available. Administrators can download these updates and distribute them to users.
Profile Manager for centrally managing user desktop settings after deployment of Internet Explorer 4.
Wizard-based configuration for determining which portions of Internet Explorer 4 will be deployed and how they will be configured.
The IEAK also supports deployment methods such as Microsoft Systems Management Server (SMS), e-mail, Web sites, floppy disks, and CDs.
How It Works
You first decide how you want to distribute your custom package for Internet Explorer: CD, floppy disks, or an Internet Uniform Resource Locator (URL) for users to download the package. You use the IEAK Configuration Wizard to build custom packages that include Internet Explorer, its related components, and up to 10 other custom components.
Once you create your package, you can distribute it using the appropriate method for the type of package: locate it on an Internet or file server, or give users copies of CDs or floppy disks. Users can then run the Setup program to install Internet Explorer and the additional components on their systems. You can also use the IEAK Configuration Wizard to do the following:
Create silent installation packages that don’t allow users to change the configuration settings you have specified.
Create branded packages that customize users’ browsers using a company-specific logo, title bar text, toolbar background bitmap image, or channel title bar for Internet Explorer.
Create packages with preconfigured browser settings such as a Start page, Search page, Support page, default favorites, welcome page, desktop wallpaper, Active Channels, and proxy settings.
A TCP/IP network layer protocol used for informing routers of the availability of multicast groups on the network.
How It Works
In a multicasting environment, Internet Group Management Protocol (IGMP) is used to exchange information on the status of membership in multicast groups between routers on the network. In other words, once a router becomes aware that there are hosts on a locally attached network that are members of a particular multicast group, it advertises this information to other routers on the internetwork so that multicast messages are forwarded to the appropriate routers.
To join a multicast group, a host must report its request for membership to nearby routers. These routers periodically poll the hosts in their locally attached networks to check on their membership status. When a host first joins a multicast group, it sends an IGMP message called a Host Membership Report that is directed to the multicast address 244.0.0.1 containing the multicast address that identifies the group it wants to join. Routers connected to that host’s local network then advertise to other routers throughout the internetwork that the particular network has hosts belonging to that multicast group. The routers poll the hosts regularly by sending Host Membership Query messages to determine whether any of them are still members of that group. If no hosts on the network belong to that group any longer, the router stops advertising the information to other routers on the internetwork so that multicast messages directed to that group are no longer forwarded to it.
NOTE
IGMP is used in Microsoft Windows NT and Windows 2000 only when the Windows Internet Naming Service (WINS) is installed. At startup, a WINS server sends IGMP packets to the multicast address 224.0.1.24 to seek out possible WINS replication partners on the network.
See IUSR_ComputerName
The service integrated into the Microsoft Windows 2000 Server operating system platform that provides support for application-layer Internet protocols. In the earlier Windows NT Server platform, IIS stood for “Internet Information Server” and was an optional component of Windows NT Server. Internet Information Services (IIS) is also the foundational component for a wide variety of Microsoft Internet and intranet solution platforms, including Microsoft Site Server, Microsoft Commercial Internet System (MCIS), and other Microsoft BackOffice products.
IIS has evolved since it was first released for Windows NT 3.51 into its current version 5.0 for the Windows 2000 platform. The highest version available for the Windows NT platform is version 4.01, which was included as part of the Windows NT Option Pack. Both IIS versions 4.01 and 5.0 support the following features:
Fully integrated with Windows NT security and the version of NTFS used in Windows NT
Full support for version 1.1 of Hypertext Transfer Protocol (HTTP)
Support for File Transfer Protocol (FTP)
Limited support for Simple Mail Transfer Protocol (SMTP)
Support for Network News Transfer Protocol (NNTP)
Support for advanced security using the Secure Sockets Layer (SSL) and related protocols
Provides a platform for deploying scalable Web server applications using Active Server Pages (ASP); Internet Server API (ISAPI); Common Gateway Interface (CGI); Microsoft Visual Basic, Scripting Edition (VBScript); JScript; and other installable scripting languages such as Perl
Allows Web applications to be run as isolated processes in separate memory spaces to prevent one application crash from affecting other applications
Integrates with Microsoft Transaction Server (MTS) and Microsoft Message Queue (MSMQ) Server for deploying transaction-based Web applications
Can be managed using the Microsoft Management Console (MMC), through a standard Web browser such as Microsoft Internet Explorer, or by running administrative scripts using the Windows Scripting Host (WSH)
Includes domain blocking for allowing/granting access on the basis of IP address or domain
Allows IIS activity to be logged in various formats including IIS, World Wide Web Consortium (W3C), National Computer Security Association (NCSA), and open database connectivity (ODBC) logging
Allows Web site operators to be assigned for limited administration of each Web site
Bandwidth throttling to prevent one Web site from monopolizing a server’s available bandwidth
NOTE
IIS 4 offers only Microsoft Personal Web Server (PWS) for Windows NT Workstation, Windows 95, or Windows 98.
A Lightweight Directory Access Protocol (LDAP) directory service running on a server that lets users of Microsoft NetMeeting locate and contact other NetMeeting users to conference and collaborate over the Internet or over a private TCP/IP internetwork. The Internet Locator Service (ILS) replaces the earlier User Locator Service (ULS) technology.
How It Works
Microsoft Commercial Internet System (MCIS) has an ILS service that functions as a memory-resident database for storing dynamic directory information about NetMeeting users. This information, which includes a user’s name, company, and IP address, is stored in an Active Directory Global Catalog and can be accessed by any LDAP client, such as NetMeeting. Clients periodically refresh the information in the ILS database. Users can access the ILS using LDAP to place a call to other NetMeeting users and to determine which NetMeeting users are currently logged on to the ILS. Using Active Server Pages (ASP), you can design a customizable Web interface that displays who is currently online and allows users to search for other users and initiate NetMeeting sessions with them.
An Internet standard protocol for storing and retrieving messages from Simple Mail Transfer Protocol (SMTP) hosts. Internet Mail Access Protocol version 4 (IMAP4) provides functions similar to Post Office Protocol version 3 (POP3), with additional features as described in this entry.
How It Works
SMTP provides the underlying message transport mechanism for sending e-mail over the Internet, but it does not provide any facility for storing and retrieving messages. SMTP hosts must be continuously connected to one another, but most users do not have a dedicated connection to the Internet.
IMAP4 provides mechanisms for storing messages received by SMTP in a receptacle called a mailbox. An IMAP4 server stores messages received by each user until the user connects to download and read them using an IMAP4 client such as Microsoft Outlook 2000 or Microsoft Outlook Express.
IMAP4 includes a number of features that are not supported by POP3. Specifically, IMAP4 allows users to
Access multiple folders, including public folders
Create hierarchies of folders for storing messages
Leave messages on the server after reading them so that they can access the messages again from another location
Search a mailbox for a specific message to download
Flag messages as read
Selectively download portions of messages or attachments only
Review the headers of messages before downloading them
To retrieve a message from an IMAP4 server, an IMAP4 client first establishes a Transmission Control Protocol (TCP) session using TCP port 143. The client then identifies itself to the server and issues a series of IMAP4 commands:
LIST: Retrieves a list of folders in the client’s mailbox
SELECT: Selects a particular folder to access its messages
FETCH: Retrieves individual messages
LOGOUT: Ends the IMAP4 session
NOTE
IMAP4 is supported by Microsoft Exchange Server. Because IMAP4 clients can allow read messages to remain on the IMAP4 server, IMAP4 is especially useful for mobile users who dial up and access their mail from multiple locations. The downside is that IMAP4 servers require more resources than POP3 servers because users tend to leave large numbers of messages on the server.
TIP
To troubleshoot problems with remote IMAP4 servers, use Telnet to connect to port 143. Then try issuing various IMAP4 commands such as the ones described in this entry and examine the results.
A component of Microsoft Exchange Server that enables Exchange to send and receive Simple Mail Transfer Protocol (SMTP) mail to foreign SMTP mail systems such as the Internet. Post Office Protocol version 3 (POP3) clients can use Internet Mail Service to send and receive e-mail.
Internet Mail Service can use the SMTP backbone of the Internet for connecting Exchange sites. Many sites have existing Internet connections that can be used for this purpose. One advantage of Internet Mail Service over Site Connector is that you can schedule Internet Mail Service to route messages at different times or intervals. One disadvantage is that this routing can produce a bottleneck because all messaging traffic flows through one server in each site.
A cooperative venture between Network Solutions, Inc. (NSI) and the U.S. government. Network Solutions is the agency currently responsible for coordinating registration of domain names within the Domain Name System (DNS). Internet Network Information Center (InterNIC) is responsible for registering and maintaining the top-level domains .com, .edu, .net, .gov, and .org. InterNIC itself is a registered service mark of the U.S. Department of Commerce. InterNIC acts as both a registry that maintains a database of top-level domain information and a registrar that provides name registration services and other value-added services.
A new nonprofit agency called Internet Corporation for Assigned Names and Numbers (ICANN) will soon open up the registration and management of the DNS to companies other than NSI.
On the Web
•
InterNIC home page : http://www.internic.net
A component of Microsoft Exchange Server that enables Exchange users to access Usenet newsgroups as public folder content and make public folder content available as Usenet newsgroups. The Internet News Service governs newsgroup messaging between Exchange servers and Usenet hosts and enables Network News Transfer Protocol (NNTP) clients to download lists of newsgroups and read or post messages. It can also be used as a method for replicating public folder content between Exchange organizations.
TIP
If you plan to host Usenet newsgroups, be sure that you have adequate disk space to accommodate the large daily feed.
A TCP/IP network layer protocol for addressing and routing packets of data between hosts on a TCP/IP network. Internet Protocol (IP) is a connectionless protocol that provides best-effort delivery using packet-switching services.
How It Works
IP does not guarantee delivery of data. The responsibility for guaranteeing delivery and sending acknowledgments lies with the higher transport-level protocol Transmission Control Protocol (TCP).
The structure of an IP packet is shown in the following diagram. Some of the more important header fields include
Source IP address: The IP address of the host transmitting the packet.
Destination IP address: The IP address of the host to which the packet is being sent, a multicast group address, or the broadcast IP address 255.255.255.255.
Header checksum: A mathematical computation used for verifying that the packet was received intact.
Time to Live (TTL): The number of router hops that the packet can make before being discarded.
Fragment offset: The position of the fragment if the original IP packet has been fragmented (for example, by a router). This information enables the original packet to be reconstructed.
IP packets are routed in the following fashion:
If IP determines that the destination IP address is a local address, it transmits the packet directly to the destination host.
If IP determines that the destination IP address is a remote address, it examines the local routing table for a route to the destination host. If a route is found, it is used; if no route is found, IP forwards the packet to the default gateway. In either case, the packet destined for a remote address is usually sent to a router.
At the router, the TTL is decreased by 1 or more (depending on network congestion), and the packet might be fragmented into smaller packets if necessary. The router then determines whether to forward the packet to one of the router’s local network interfaces or to another router. This process repeats until the packet arrives at the destination host or has its TTL decremented to 0 (zero) and is discarded by a router.
Graphic I-11. The structure of an IP packet.
A term that generally refers to application-layer TCP/IP protocols commonly used over the Internet. The following table shows many of the standard Internet protocols in use today. Some of these protocols, such as Gopher, are rapidly waning in popularity. To access a protocol such as Hypertext Transfer Protocol (HTTP) with a Web browser such as Microsoft Internet Explorer, you would use a Uniform Resource Locator (URL) beginning with http://.
Standard Internet Protocols
| Protocol | Protocol Name | Description |
| http | Hypertext Transfer Protocol | Used for Web pages that contain text, graphics, sound, and other digital information stored on a Web server on the World Wide Web |
| ftp | File Transfer Protocol | Transfers files between two computers over the Internet |
| gopher | Gopher protocol | Displays information stored on a network of Gopher servers |
| wais | WAIS protocol | Used for accessing a Wide Area Information Servers database |
| file | File protocol | Opens a file on a local hard disk or a network share |
| https | Secure Hypertext Transfer Protocol | Establishes an encrypted HTTP connection using the Secure Sockets Layer (SSL) protocol |
| mailto | MailTo protocol | Starts a Simple Mail Transfer Protocol (SMTP) e-mail program to send a message to the specified Internet e-mail address |
| news | News protocol | Opens a Network News Transfer Protocol (NNTP) newsreader and the specified Usenet newsgroup |
| nntp | Network News Transfer Protocol | Performs the same function as the News protocol |
| mid | Musical Instrument Digital Interface (MIDI) protocol | Plays MIDI sequencer files if the computer has a sound card |
| telnet | Telnet protocol | Starts a Telnet terminal emulation program |
| rlogin | Rlogin protocol | Starts an Rlogin terminal emulation program |
| tn3270 | TN3270 protocol | Starts a TN3270 terminal emulation program |
| pnm | RealAudio protocol | Plays RealAudio streaming audio from a RealAudio server |
| mms | Microsoft Media Server (MMS) protocol | Plays .asf streams from a Microsoft NetShow server |
A protocol for negotiating and controlling the security of transmissions over a TCP/IP internetwork. Internet Protocol Security (IPSec) defines standards for data encryption and data integrity at the level of Internet Protocol (IP) datagrams and can be used to encrypt transmission of data and ensure that the data originated from the sender and was not modified in transit. IPSec encrypts data at the IP level and uses tunneling to securely send information over the Internet and between intranets. IPSec is an emerging Internet Engineering Task Force (IETF) standard and is implemented in the Microsoft Windows 2000 operating system.
How It Works
IPSec is implemented at the transport layer of the Open Systems Interconnection (OSI) reference model and protects IP and higher protocols using security policies that can be configured to meet the needs of securing users, sites, applications, or the enterprise in general. IPSec essentially resides as an additional layer under the TCP/IP protocol stack and is controlled by security policies installed on each machine and by an encryption scheme negotiated between the sender and the receiver. These security policies consist of a collection of filters with associated behaviors. When the IP address, port number, and protocol of an IP packet match a particular filter, the corresponding behavior is applied to the packet.
In Windows 2000, these security policies are created and assigned at the domain level or for individual hosts using the IPSec Management snap-in for the Microsoft Management Console (MMC). IPSec policies consist of rules that specify the security requirements for different forms of communication. These rules are used to initiate and control secure communication based on the nature of the IP traffic, the source of the traffic, and its destination. These rules specify authentication and negotiation methods, tunneling attributes, and connection types.
To establish a security association (secure communication session) between two computers, a protocol framework called ISAKMP/Oakley is used. ISAKMP/Oakley includes a set of cryptographic algorithms but is also extensible to support user-defined encryption algorithms. During the negotiation process, agreement is reached on the authentication and security methods to be used, and a shared key is generated for data encryption. IPSec supports two different kinds of security associations:
Authentication Header (AH) protocol: Provides user authentication and protection from replay attacks and supports data authentication and integrity functions. AH enables the recipient to be sure of the identity of the sender and that the data has not been modified during transmission. AH does not provide any encryption of the data itself. AH information is embedded in the IP packet’s header and can be used alone or with the Encapsulating Security Payload (ESP) protocol.
Encapsulating Security Payload (ESP) protocol: Encapsulates and encrypts user data to provide full data confidentiality. ESP also includes optional authentication and protections from replay attacks and can be used either by itself or with AH. ESP information is also embedded in the IP packet’s header.
Devices and software configured to support IPSec can use either public key encryption using keys supplied by certificate authorities (CAs) or preshared keys for private encryption.
A technology for using the Internet to send real-time, text-based messages. Internet Relay Chat (IRC) is defined in Request for Comments (RFC) 1459.
How It Works
IRC is a client/server technology in which users employ IRC client software to connect to an IRC server or hub. Clients can then connect to an existing chat group (also called chat room or channel) and type messages to other users currently in that group. Chat groups are identified using a pound sign (#) prefix. Messages are transmitted in real time and can appear character by character on the recipients’ client software if the person sending the message types slowly enough.
Depending on how the chat server is configured, users might be able to create their own chat rooms and hold private discussions. Some chat servers require that you register once to obtain a unique nickname, while others allow you to select a nickname for the current session only. Some Web sites also offer Web-based interfaces to their chat servers.
Microsoft Exchange Server version 5.5 includes an IRC-based chat server that you can use to set up public or private IRC sites.
On the Web
•
IRC.NET : http://www.irc.net
An umbrella organization for several long-term research groups that focus on standards for Internet protocols, architecture, applications, and technologies. Internet Research Task Force (IRTF) research groups include
The End-to-End (E2E) group, which is concerned with end-to-end services and protocols implemented in hosts
The Information Infrastructure Architecture group, which works to articulate a common information infrastructure for the Internet to support greater interoperability between applications
The Internet Resource Directory group, which develops models for resource description on the Internet, including mechanisms for querying, indexing, and retrieval
The Network Management group, which is concerned with issues relating to the management of the Internet from the perspectives of high-level management domains and customer-oriented services
The Services Management group, which is concerned with the convergence of networking technologies relating to the Internet
The IRTF is overseen by the Internet Architecture Board (IAB).
On the Web
•
IRTF home page : http://www.irtf.org
A Microsoft set of standard application programming interfaces (APIs) for developing extensions to Internet Information Services (IIS). Internet Server API (ISAPI) provides developers with a powerful way to extend the functionality of IIS to provide better performance than Active Server Pages (ASP) or the Common Gateway Interface (CGI) and to provide low-level access to all Microsoft Win32 API functions. Of course, since ISAPI dynamic-link libraries (DLLs) are generally written in a high-level programming language such as C or C++, they are usually more difficult to develop than ASP-based or CGI-based solutions and might not scale as well.
There are two kinds of ISAPI DLLs, which have different uses on IIS:
ISAPI extensions: Run-time DLLs that can run either in process or out of process on IIS. ISAPI extensions provide extended functionality to IIS.
ISAPI filters: Used to preprocess packets of data before they enter or leave the IIS main process. An example of an ISAPI filter is the Secure Sockets Layer (SSL) protocol component on IIS 4.
TIP
You can create ISAPI extensions easily using the ISAPI Extension Wizard in Microsoft Visual C++.
A company that provides individual users and businesses with connectivity to the Internet. Internet service providers (ISPs) also provide clients with access to Internet services such as Web hosting, Simple Mail Transfer Protocol (SMTP) mail, Usenet newsgroups, Internet Relay Chat (IRC), and downloadable Internet software.
ISPs come in various shapes and sizes, from volunteer-run freenets to local, regional, and national service providers such as America Online. Many smaller ISPs, especially those that originated in a university environment, still use freely available software such as Linux, Apache’s Web server, and Sendmail for providing services to customers. Larger ISPs often use a heterogeneous network in which Internet Information Services (IIS) and Microsoft Exchange Server play an essential role by providing core Web and mail services, as well as support for advanced Web and e-commerce applications for business and corporate clients.
Any of a number of technologies for making information accessible to users over the Internet. Each Internet service is defined by a protocol, such as Hypertext Transfer Protocol (HTTP), and is enabled using client/server applications, such as Web browsers and Web servers. Internet protocols are defined in the Request for Comments (RFC) documents published by the Internet Engineering Task Force (IETF).
Internet services include Telnet, File Transfer Protocol (FTP), Gopher, Wide Area Information Server (WAIS), Archie, Veronica, Simple Mail Transfer Protocol (SMTP), Network News Transfer Protocol (NNTP), and Internet Relay Chat (IRC). Some of these services have remained popular (such as NNTP), while others have faded in popularity (such as Gopher). The most popular Internet service by far is the relatively new World Wide Web (WWW), which is based on HTTP.
The main administrative tool for Internet Information Services (IIS) on Microsoft Windows 2000 platforms. This tool is called Internet Service Manager in Windows NT. Internet Service Manager is implemented as a separate application in IIS versions 3.0 and earlier, but with IIS 4.0, it is implemented as a snap-in for the Microsoft Management Console (MMC). In IIS 5.0 on the Windows 2000 platform, this snap-in is simply called Internet Information Services, and its shortcut in the Administrative Tools program group is called Internet Services Manager.
Using Internet Services Manager, you can
Create and delete virtual servers (Web sites) and virtual directories
Configure the properties of virtual servers, virtual directories, and individual files
Create and configure File Transfer Protocol (FTP) sites
Configure the Simple Mail Transfer Protocol (SMTP) and Network News Transfer Protocol (NNTP) services
Configure security settings and levels
Start, stop, and pause virtual servers
A professional society founded in 1992 that provides leadership for the development and evolution of the Internet. The Internet Society (ISOC) comprises over 150 individual organizations, including government agencies and private companies, and is an umbrella organization for other Internet groups, including the Internet Engineering Task Force (IETF) and the Internet Architecture Board (IAB).
The ISOC has more than 6000 individual members in more than 100 countries. It is governed by a board of trustees elected from its membership. The ISOC hosts conferences and issues publications related to the development and management of the Internet. The ISOC has taken the lead in promoting the formation of a nonprofit constituency for the new Internet Corporation for Assigned Names and Numbers (ICANN), which oversees the Internet Domain Name System (DNS). The ISOC essentially functions as a legal umbrella for the standardization processes managed by the IETF and the IAB.
On the Web
•
ISOC home page : http://www.isoc.org
A network, usually TCP/IP, consisting of multiple networks joined by routers. More generally, an internetwork is any network consisting of smaller networks joined in any fashion using bridges, switches, routers, and other devices. For example, an Internet Protocol (IP) internetwork could consist of a mix of Microsoft Windows NT or Windows 2000 and UNIX machines distributed over different subnets, connected with standard IP routers from Cisco Systems or another vendor. An Internetwork Packet Exchange (IPX) internetwork could be a set of networks using Novell NetWare clients and servers running IPX that are connected using IPX-enabled routers.
Internetworking is the process of planning, implementing, and maintaining an internetwork. For IP internetworks, this involves such tasks as
Determining which IP address classes and network IDs to use
Dividing the internetwork into different subnets using a custom subnet mask
Managing host IP address information using the Dynamic Host Configuration Protocol (DHCP)
Configuring dynamic routers for efficient exchange of routing information
Acquiring tools and skills for troubleshooting internetwork problems
An operating system developed by Cisco Systems for its line of routers and access servers to provide a standard way to configure these devices.
How It Works
The Internetwork Operating System (IOS) is usually stored as a system image within a router’s flash memory. The startup configuration file called startup-config is stored in nonvolatile RAM, and the actual operating configuration of the router (its routing tables, queues, and so on) are stored in ordinary RAM. Cisco routers can typically run in three different operating environments:
ROM monitor: Also called the bootstrap program, this environment is accessed through the console port. The ROM monitor initiates the bootstrap process and can be used to run diagnostics, recover lost passwords, and recover from system failures.
Boot ROM: This environment is used mainly to upgrade to new versions of IOS by loading a new image of IOS into flash memory.
Cisco IOS: This is the normal operating environment, in which you can enter commands to configure and troubleshoot the operation of your router. For example, you can enter the show version command to determine which version of IOS your router is running.
The normal IOS operating environment itself can run in four different modes:
User EXEC mode: This mode is enabled by default when you connect to a router using a command-line console (for example, using a Telnet connection). Using EXEC, the IOS system command interpreter, you can type commands using a command-line interface. User EXEC mode supports a subset of IOS commands for performing basic actions such as configuring terminal settings, running tests, and displaying configuration information.
Privileged EXEC mode: This mode lets you do everything you can do in User EXEC mode and more, including running the setup command to enter configuration information, running the configure command to modify configuration information, and running the debug command to display event messages. Enter Privileged EXEC mode by typing the enable command.
Configuration mode: This mode lets you configure your router’s settings. You enter this mode by typing the configure terminal command.
Setup mode: This mode is used to create new configuration files that enable features such as addressing, routing, and security.
NOTE
Although IOS was originally designed as a monolithic, “router-centric” operating system, it has evolved into a modular operating system composed of different subsystems that can easily be upgraded and that support complex distributed networking functions.
TIP
You can quickly tell which command mode of IOS you are running by looking at your command prompt. The following table shows the various IOS command modes.
Privileged EXEC mode should always be password protected because it lets you reconfigure key operating system parameters. Don’t run the debug command when you are connected to the network unless absolutely necessary because this increases the load on the processor. Type a question mark (?) at a prompt to determine which commands are available in the currently enabled IOS mode.
IOS Command Modes
| Prompt | IOS Mode |
| Router> | User EXEC |
| Router# | Privileged EXEC |
| Router(config)# | Configuration |
| (A series of dialog box prompts) | Setup |
On the Web
•
Cisco IOS Software : http://www.cisco.com/warp/public/732/index.html
A Novell NetWare protocol used for routing packets from one network node to another throughout an internetwork. Internetwork Packet Exchange (IPX) is a network layer protocol and provides connectionless datagram services for Ethernet, Token Ring, and other common data-link layer protocols. IPX is the commonly used local area network (LAN) protocol on legacy NetWare-based LANs but has recently been replaced with TCP/IP for NetWare 5.x.
How It Works
IPX packets use 32-bit (4-byte) network numbers to uniquely identify each data link (connected network) in an IPX internetwork. The administrator of each network assigns these network numbers, which must be unique for each connected network; all nodes on a connected network must have the same network number. Nodes discover their network number by communicating with routers attached to the local network. Routers use these network numbers to route IPX packets from one network to another within an internetwork. IPX is thus a routable protocol. The structure of an IPX packet is shown in the following diagram.
IPX also uses 48-bit (6-byte) addresses for each node within a given network. An entire IPX network address is thus 4 + 6 = 10 bytes long. IPX packets are assigned a 16-bit (2-byte) socket number to identify the networking service they are communicating with—for example, Network Control Protocol (NCP), Service Advertising Protocol (SAP), or Routing Information Protocol (RIP). Thus, the following 12-byte triple completely identifies the networking service that a packet is communicating for:
{network number, node address, socket number} When an IPX client is booted on a NetWare internetwork using IPX-enabled routers, the client broadcasts a Get Nearest Server (GSN) request message to its locally connected network in order to locate the nearest NetWare server. If a NetWare server can’t be located on the connected network, the router informs the client of the nearest available server based on the cost of the connection. The router is familiar with this information because NetWare servers using IPX periodically notify the network of their presence using SAP, which allows IPX routers to construct server tables based on SAP numbers.
Graphic I-12. The structure of an IPX packet.
IPX is a connectionless protocol that works at the network layer of the Open Systems Interconnection (OSI) reference model, and IPX packets are connectionless datagrams. To function within connected networks, IPX works with a transport layer protocol called the Sequenced Packet Exchange (SPX) protocol. SPX is responsible for generating acknowledgments for IPX packets received over the network to ensure that no packets were lost during transport.
TIP
On Ethernet networks, NetWare clients and servers can communicate with each other using IPX only if they use compatible frame types (encapsulation formats). The terminology used to describe these frame types depends on whether you’re discussing Novell NetWare clients and servers or IPX-enabled routers from Cisco Systems. The following table illustrates these differences.
Ethernet_II is the default frame type for NetWare version 3.x and earlier, while NetWare 4.x uses the Ethernet_802.2 frame type.
Frame Type Terminology
| Common Terminology | Novell Terminology | Cisco Terminology |
| Ethernet | Ethernet_II | arpa |
| raw | Ethernet_802.3 | novell-ether |
| 802.3 | Ethernet_802.2 | sap |
| snap | Ethernet_SNAP | snap |
See Internet Network Information Center (InterNIC)
A mechanism for establishing a connection between processes, running on two computers or on a single multitasking computer, to allow data to flow between those processes. Interprocess communication (IPC) mechanisms are commonly used in client/server environments and are supported to various degrees by the different Microsoft Windows operating systems.
How It Works
A networked IPC generally consists of the following two components:
An application programming interface (API) that defines the standard set of functions that can be called when software tries to use an IPC.
A protocol that specifies the format in which the information is transmitted using the IPC. When IPCs are passed over the network, the format specified is the format of the packet or frame transmitted between the computers.
The following table lists some IPC mechanisms and the platforms that support them.
IPC Mechanisms Supported on Windows Platforms
| Process | Windows NT | Windows 95 | Windows 98 | Windows 2000 |
| Named pipes | x | x | x | x |
| Mailslots | x | x | x | x |
| NetBIOS | x | x | x | x |
| Windows Sockets | x | x | x | x |
| Remote procedure call (RPC) | x | x | x | x |
| Network Dynamic Data Exchange (NetDDE) | x | x | x | x |
| Distributed Component Object Model (DCOM) | x | x | x |
A private TCP/IP internetwork within an organization that uses Internet technologies such as Web servers and Web browsers for sharing information and collaborating. Intranets can be used to publish company policies and newsletters, provide sales and marketing staff with product information, provide technical support and tutorials, and just about anything else you can think of that fits within the standard Web server/Web browser environment.
Internet Information Services (IIS), with its support for Active Server Pages (ASP), is an ideal platform for building intranet applications that can be accessed using a standard Web browser such as Microsoft Internet Explorer.
Also called an IMUX, a device that can perform inverse multiplexing of digital telecommunication channels. A typical IMUX might be capable of inverse multiplexing together four Basic Rate Interface ISDN (BRI-ISDN) lines, two T1 lines, or four T1 lines to provide a throughput of 512 Kbps or 5.888 Mbps, respectively. This saves the expense of having to purchase or lease equipment to individually terminate each Integrated Services Digital Network (ISDN) or T1 line, and it provides an efficient way to increase wide area network (WAN) speed for high-bandwidth uses such as videoconferencing, T1 backup, or large file transfers. IMUXes can include built-in CSU/DSU (Channel Service Unit/Data Service Unit) functionality, they have a 34-pin built-in V.35 LAN (data) interface, and they have an RJ-45 or DB25 connector for the line interface. They often feature load-sharing functions so that if one ISDN or T1 line goes down, no delays occur. IMUXes usually include diagnostic and loopback functions for both local and remote troubleshooting.
A networking and telecommunications technique of combining the bandwidths of a number of digital lines into a single virtual pathway for high-speed communication. Inverse multiplexing is the opposite of multiplexing, which combines data transmissions from multiple pieces of data terminal equipment (DTE) into a single digital communication channel.
How It Works
You can connect a device called an inverse multiplexer, or IMUX, to the termination of several leased digital lines to create a single virtual connection with a bandwidth equal to the sum of the bandwidths of the individual lines. Inverse multiplexing can be used to aggregate the bandwidth of digital data service (DDS), switched 56, Integrated Services Digital Network (ISDN), or T1 and higher T-carrier services into a single high-bandwidth DTE interface. You can then connect this DTE interface to customer premises equipment such as routers or CSU/DSUs (Channel Service Unit/Data Service Units), which are connected to the customer’s network.
Graphic I-13. Inverse multiplexing.
Inverse multiplexing requires an IMUX at both the customer premises and the telco central office (CO). When several ISDN subchannels are multiplexed into a single high-speed channel, a connection is initiated when the customer’s IMUX dials a number to establish a connection with the CO IMUX. Once a single ISDN subchannel is established, the customer IMUX dials the remaining numbers and establishes the additional ISDN subchannels. Once all the subchannels are up, a protocol called Bandwidth On Demand Interoperability Group (bonding) establishes synchronization between the two stations using a handshaking mechanism to resolve any delays between the subchannels. These delays are primarily the result of the different circuit-switched communication subchannels having physical paths of different lengths, even though they have the same two endpoints. The bonding protocols also ensure that data sent over each subchannel arrives at its destination in the correct order.
The main advantage of inverse multiplexing is that it is often less expensive to lease several low-speed digital lines and inverse multiplex them together than to lease a single high-speed digital line with the same aggregate bandwidth. Inverse multiplexing is also useful in areas where high-speed digital services such as T1 are not readily available.
See also multiplexing
A Domain Name System (DNS) query in which a resolver contacts a name server to perform a reverse name lookup, requesting a host name for a given IP address. An inverse query is the opposite of the usual DNS query—that is, given a host’s fully qualified domain name (FQDN), it determines the host’s IP address.
Because of the hierarchical structure of the namespace of the DNS, inverse queries normally have to search all domains to resolve the IP address. To circumvent this, a special domain called in-addr.arpa exists for reverse name lookups. The nodes in this domain are named after the IP addresses of hosts but with the octets in reverse order to facilitate searching. However, inverse queries can take place only on the name server queried and cannot be forwarded to another name server. Because individual name servers manage only a small portion of the entire DNS namespace, there is no guarantee that a given inverse query issued against a specific name server will meet with a successful response.
NOTE
Most names used on Internet servers are configured for reverse name lookups to avoid the extra overhead required. However, if you need to use the DNS troubleshooting utility nslookup, you should configure the in-addr.arpa domain on name servers to support inverse queries. Otherwise, there is no need to configure this inverse domain.
See also iterative query, recursive query
A component of Microsoft Windows NT executive running in kernel mode that is responsible for all Windows NT input/output functions. The I/O Manager integrates various networking components, including the following:
File system drivers
Networking protocols
Network adapter card drivers
How It Works
The I/O Manager is modular or layered in design. It consists of the three networking component layers listed in this entry separated by two boundary layers, the Transport Driver Interface (TDI) layer and the network driver interface specification (NDIS) layer. The I/O Manager receives a request for shared network resources and determines whether the requested resource is local or remote. If the request is for a remote resource, it is forwarded to the appropriate redirector.
Graphic I-14. I/O Manager.
See also kernel mode, network driver interface specification (NDIS), Transport Driver Interface (TDI), Windows NT executive
See Internetwork Operating System (IOS)
See Internet Protocol (IP)
A 32-bit logical address for a host on a TCP/IP network. Each host on a TCP/IP network needs a unique IP address for communication to take place reliably on the network.
How It Works
IP addresses are usually expressed in four-octet, dotted-decimal form—w.x.y.z—in which each octet ranges in value from 0 to 255 (with some restrictions). The IP address of a host is partitioned by the network’s subnet mask into two parts, a network ID and a host ID.
IP addresses belong to certain classes according to their first octet, as defined in the following table. The actual distinguishing feature of each class is the pattern of high-order bits in the first octet, but it is easier to remember these classes by their first octet decimal numbers.
IP Address Classes
| IP Address Class | Possible First Octet | Used For |
| Class A | 1–126 | Very large networks |
| Class B | 128–191 | Medium to large networks |
| Class C | 192–223 | Small networks |
| Class D | 224–239 | Multicasting |
| Class E | 240–255 | Reserved (experimental) |
IP addresses whose first octet is 127 represent the loopback address and are used for troubleshooting purposes only, not for naming hosts.
NOTE
Networks that are directly connected to the Internet must have their IP addresses assigned by the Internet Network Information Center (InterNIC) or some other authority. Businesses usually obtain these addresses through their local Internet service provider (ISP). However, firewall and proxy server combinations, which are popular on today’s networks, hide a network’s IP addresses from other hosts on the Internet. These private networks can use any IP addresses they choose, although InterNIC recommends the following IP address blocks for private networks:
Class A networks: 10.x.y.z
Class B networks: 172.16.y.z through 172.31.y.z
Class C networks: 192.168.0.z through 192.16.255.z
TIP
Note the following considerations for valid IP addressing:
The network ID cannot be 127.
The network ID and host ID cannot both be 255.
The network ID and host ID cannot both be 0.
The host ID must be unique for a given network ID.
See also subnetting
See interprocess communication (IPC)
A TCP/IP utility that displays the current TCP/IP configuration settings for each network interface card (NIC) on a Microsoft Windows NT or Windows 2000 system. The ipconfig command is often one of the first commands you use to check the status of the connection when you experience communication problems on a TCP/IP network.
How It Works
When you type ipconfig at a command prompt, the following information is displayed for each NIC:
IP address
Subnet mask
Default gateway
You can display additional information, including the host name, physical address, and Dynamic Host Configuration Protocol (DHCP), Windows Internet Name Service (WINS), and Domain Name System (DNS) configuration, using ipconfig /all.
You can release and renew IP addresses obtained by DHCP using ipconfig /release and ipconfig /renew.
See IPv6
See Internet Protocol Security (IPSec)
An umbrella term for technologies that allow the transmission of voice and video over TCP/IP internetworks instead of the traditional Public Switched Telephone Network (PSTN). Many vendors have produced platforms and software for IP telephony, but the technology is still in its growth stage and standards are not yet clearly established.
The advantage of IP telephony is that it allows voice communication to be closely integrated with data transmission over corporate networks and allows long-distance communication to be established over the Internet instead of through private long-distance carriers such as Sprint and MCI WorldCom. The primary difficulty with IP telephony is that the existing Internet Protocol (IP) internetwork is connectionless and suffers from latency that can cause annoying glitches (pauses) in voice and video transmission over IP packets. This happens because TCP/IP was not originally designed as a connection-oriented service capable of specific levels of quality of service (QoS), whereas the PSTN, with its circuit-switched connections, provides just that.
See also H.323, Voice over IP (VoIP)
The current 32-bit IP addressing scheme used on TCP/IP networks worldwide. Because the number of hosts connecting to the Internet has skyrocketed in recent years, unique IP addresses are gradually running out. A new scheme called IPv6 has been proposed and is currently under review by the Internet community. However, with most corporate networks now hiding their networks behind firewalls, the pressure to move to IPv6 has lessened because companies can choose any network ID they want for their private network. The only assigned IP addresses they require from their Internet service provider (ISP) are for the public interfaces on their firewall machines. At this point, IPv4 seems to be firmly entrenched in the networking world for at least the next few years.
See also Internet Protocol (IP)
A proposed new IP addressing scheme for TCP/IP networks to replace the current IPv4 scheme. Proposed features of IPv6 include the following:
128-bit IP addresses to solve the problem of the available IP address pool being depleted
A simplified header format to reduce network overhead and improve performance
Support for preallocation of network resources to enable time-dependent services such as voice and video to receive guaranteed bandwidth and quality of service (QoS)
Extensibility to account for future growth and evolution of Internet technologies and standards
IPv6 is also sometimes referred to as IPng, which stands for “IP Next Generation.” A network called the 6Bone was set up in 1995 as a testbed for IPv6 and to investigate how the Internet can be migrated from IPv4 to IPv6.
NOTE
IPv6 is currently a draft Internet Engineering Task Force (IETF) standard, Request for Comments (RFC) 2460. Many vendors, including Microsoft, are currently exploring ways to integrate IPv6 into their network products.
See Internetwork Packet Exchange (IPX)
A Microsoft Windows NT and Windows 2000 utility for viewing and modifying Internetwork Packet Exchange (IPX) routing table information when NWLink IPX/SPX-Compatible Transport is installed on machines running Windows NT and Windows 2000. You can use ipxroute to display the current IPX settings, such as frame type, IPX network numbers, and internal network number. You can also use it to display the IPX routing table, Service Advertising Protocol (SAP) table, and IPX routing statistics.
Example
The Ipxroute Table command shows the IPX routing table, while Ipxroute Config shows binding information for IPX, such as the IPX network number.
Microsoft’s version of the Novell NetWare IPX/SPX (Internetwork Packet Exchange/Sequenced Packet Exchange) protocol for Microsoft Windows 95, Windows 98, and Windows 2000. Using IPX/SPX and Client for NetWare Networks, clients running Windows 95 and Windows 98 can access shared resources on NetWare servers directly, as long as they have appropriate permissions and rights. Under Windows 2000 this protocol is part of NWLink. IPX/SPX-Compatible Protocol can also be used to access Windows NT or Windows 2000 servers running File and Printer Sharing for NetWare Networks. IPX/SPX-Compatible Protocol supports the 32-bit Windows Sockets 1.1 and NetBIOS over Internetwork Packet Exchange (IPX) programming interfaces.
NOTE
Although the Windows 95 and Windows 98 user interfaces allow you to configure multiple bindings for IPX/SPX-Compatible Protocol to multiple network interface cards (NICs), only the first binding is actually used. You cannot use IPX/SPX-Compatible Protocol for connecting to NetWare over an ARCNET network; you must install real-mode IPX drivers instead.
TIP
IPX/SPX-Compatible Protocol is set by default to autodetect the frame type used on a NetWare network. If no frame type is detected, the default 802.2 type is used. If multiple frame types are detected, the predominant one is selected.
See Internet Relay Chat (IRC)
See Infrared Data Association (IrDA)
A standard developed in 1998 by the Infrared Data Association (IrDA) for communication over IR light between in-room cordless peripheral devices and a host computer. Peripherals such as keyboards, joysticks, mouse devices, and other pointing devices can use IrDA Control for communicating with their host computer. IrDA Control is implemented using a suite of protocols that include the following:
IrDA Control PHY (physical layer), which provides for data transmission that is bidirectional and error-correcting, over IR light at speeds of up to 75 Kbps over distances of up to 5 meters.
IrDA Control MAC (media access control), which enables host devices to communicate with multiple IrDA Control peripherals and up to eight peripherals simultaneously. IrDA Control MAC offers a fast response time by using a polling interval of 13.8 meters and supports the dynamic assignment and reuse of addresses assigned to peripheral devices.
IrDA Control LLC (logical link control), which ensures proper sequencing of data and handles retransmissions when errors occur.
See also Infrared Data Association (IrDA)
A standard developed by the Infrared Data Association (IrDA) in 1994 for two-way point-to-point communication over IR light at speeds of up to 4 Mbps. IrDA Data is used for communication between palm computers, digital cameras, cellular phones, and other devices. It is implemented using a suite of protocols, including the ones listed.
IrDA Data PHY (physical layer), which provides low-level continuous bidirectional error-correcting operation from 9600 bps up to 4 Mbps over distances of at least 1 meter. Specifically, asynchronous serial transmission is supported between 9600 bps and 115.2 Kbps, synchronous serial transmission at 1.152 Mbps, and synchronous communication at 4 Mbps.
IrDA Data Infrared Link Access Protocol (IrLAP), a serial link protocol adapted by the IrDA for infrared serial communication from the High-level Data Link Control (HDLC) protocol. IrLAP provides a single serial connection between two IrDA devices and manages the device-to-device discovery, connection, and reliable data transfer functions.
IrDA Data Infrared Link Management Protocol (IrLMP), which is used for link control and multiplexing of IrDA devices. IrLMP allows multiple IrDA devices to communicate over a single infrared link and provides for protocol and service discovery through the Information Access Service (IAS).
In addition to the three mandatory IrDA Data protocols described, a number of optional protocols are available that support flow control, port emulation, object exchange services, image exchange, interfacing with telephony devices, and infrared wireless access to local area networks (LANs).
See also Infrared Data Association (IrDA)
See Internet Research Task Force (IRTF)
See Internet Server API (ISAPI)
A dynamic-link library (DLL) that runs in the same address space as the Web server running Internet Information Services (IIS) and can access all available resources on the Web server. ISAPI extensions (sometimes called ISAPI Server extensions) can run in process or out of process on IIS. These extensions are generally loaded on demand the first time a user requests them and remain in memory until the service is stopped. You can use ISAPI extensions wherever you might use Common Gateway Interface (CGI) applications, such as for a form handler for Hypertext Markup Language (HTML) forms. An ISAPI extension is generally called in a manner similar to calling a CGI application. For example, the Uniform Resource Locator (URL) shown below invokes the extension TEST.DLL on the Web site www.northwind.microsoft.com and passes it the parameters Value1 and Value2:
http://www.northwind.microsoft.com/isapie/TEST.DLL?Value1&Value2
A dynamic-link library (DLL) that is loaded into Internet Information Services (IIS) when it starts and that remains in memory until it stops. ISAPI filters provide Web servers such as IIS with the ability to preprocess or postprocess information sent between the client and server, and they have no equivalent in the Common Gateway Interface (CGI) scheme. ISAPI filters receive special filter event notifications and respond based on these notifications. You use ISAPI filters for such tasks as custom authentication, encryption, and compression schemes or for updating logging statistics on the Web server. ISAPI filters are generally called for every Uniform Resource Locator (URL) that the Web server processes instead of being explicitly invoked by a URL, as are ISAPI extensions.
Custom ISAPI filters can be designed by third-party developers for such tasks as
Custom authentication
Data encryption
Data compression
Filtering
Traffic analysis
See Integrated Services Digital Network (ISDN)
A device that allows you to back up digital data service (DDS) lines using a dial-up Integrated Services Digital Network (ISDN) line. If the DDS line experiences failure, the fallback adapter automatically kicks in the ISDN line to maintain wide area network (WAN) connectivity. Fallback adapters typically have built-in ISDN terminal adapter functionality and can sometimes provide backup support for multiple DDS lines. The fallback and restore settings are configurable using a built-in or serial-connected terminal interface. To use a fallback adapter, you connect it to the ISDN line with the RJ-45 connector and to the local area network (LAN) bridge or router and the DDS CSU/DSUs (Channel Service Unit/Data Service Units) using the V.35 or RS-232 serial interfaces.
Graphic I-15. ISDN fallback adapter.
A router with built-in hardware for connecting directly to Integrated Services Digital Network (ISDN) lines. ISDN routers—also called ISDN access routers because they provide direct connectivity to a wide area network (WAN) connection—are a popular way of providing SOHOs (Small Office/Home Offices) with 128-Kbps dial-up ISDN connectivity to the Internet or to a remote private corporate network through the industry-standard Point-to-Point Protocol (PPP). They typically support up to 10 users in a small workgroup Ethernet local area network (LAN) and might provide some firewall, network address translation (NAT), or Dynamic Host Configuration Protocol (DHCP) support.
ISDN routers include RJ-11 jacks for connecting several analog phones, fax machines, or other devices for simultaneous voice/fax/data connectivity. Built-in data compression can increase the effective bandwidth by a factor of 5 or higher. Some ISDN routers include built-in hubs for quick connectivity. Many are manageable using a remote Telnet connection or through Simple Network Management Protocol (SNMP).
A device used at the customer premises to terminate a dial-up Integrated Services Digital Network (ISDN) line and connect it to a computer or a local area network (LAN). You use a terminal adapter when you do not have dedicated ISDN telephone or computing equipment. Terminal adapters are sometimes called ISDN modems.
How It Works
A terminal adapter connects using an RJ-45 connector to the U interface of the ISDN line at the customer premises and provides electrical termination for this line. The other interface on the terminal adapter is typically an RS-232, RS-366, RS-530, or V.35 serial interface such as DB25, or a 34-pin connector for connecting the terminal adapter to a bridge, router, or computer at the customer premises. Terminal adapters can include several RJ-11 connectors for connecting an analog telephone or a fax machine so that you can transfer data, talk on the telephone, and fax documents simultaneously over one ISDN line. Some newer terminal adapters have an S/T interface for connecting to an S/T videoconferencing unit.
Graphic I-16. ISDN terminal adapter.
ISDN terminal adapters can be stand-alone AC powered devices or interface cards that you install on your computer. They can provide 128-Kbps throughput using the Bandwidth On Demand Interoperability Group (bonding) protocol for high-speed Internet and wide area network (WAN) connectivity, with higher effective data transfer rates using built-in data compression. Terminal adapters do not provide an “always on” network connection, but their latency time interval for establishing an ISDN connection is typically small (1 to 3 seconds). You can usually also configure an idle timer for dropping idle connections to save costs.
TIP
If you need more speed than ISDN but can’t afford to upgrade to T1 lines, try using an inverse multiplexer to combine several ISDN lines into one high-speed data pipe.
When you buy ISDN terminal adapters, be sure that they support the ISDN standard used by your telco. Such standards can include the National ISDN-1, ISDN-2, and ISDN-3 standards for AT&T, Northern Telecom, and Siemens. An ISDN terminal adapter with automatic service profile identifier (SPID) detection generally works with most ISDN installations.
A command-line utility in Microsoft Exchange Server for checking the consistency of the information store databases at a higher level than the eseutil utility does. The isinteg utility checks for problems relating to referential integrity of the information store databases that are preventing the information store services from starting or are preventing users from accessing their stored messages. Such a situation can arise after the information store is restored from an offline backup. You can run isinteg (which stands for the Information Store Integrity Checker) in two different modes:
Test mode, which allows you to search the information store databases for errors in tables, unreferenced objects, and incorrect reference counts. Select the Fix option in Test mode to repair any errors the utility finds.
Patch mode, which is for repairing an information store that will not start after being restored from an offline backup.
NOTE
The isinteg utility is located in the Exchsrvr\Bin directory on an Exchange server. You should not use isinteg as part of your regular Exchange server maintenance plan—it is intended only for troubleshooting use, especially in consultation with Microsoft Product Support Services.
TIP
Always back up your information store databases before running this utility!
See International Organization for Standardization (ISO)
See Internet Society (ISOC)
See Internet service provider (ISP)
A command-line version of the Microsoft SQL Server GUI-based tool ISQL/w. The ISQL utility provides a query interface for running transact-SQL queries against SQL Server and lets administrators perform system-management tasks from servers or workstations using system-stored procedures and scripts.
NOTE
In version 7 of SQL Server, the ISQL utility does not support some version 7 features because it essentially runs with version 6.5 functionality. For example, you cannot use ISQL on version 7 to retrieve Unicode ntext data. For full support of SQL Server 7 features, use the new OSQL utility.
TIP
Use ISQL when you want to create a script for automating administrative tasks.
A graphical user interface (GUI) tool in Microsoft SQL Server that lets you directly enter transact-SQL statements and system-stored procedures into SQL Server for administering the system and querying databases. ISQL/w can be used to graphically analyze transact-SQL queries.
NOTE
ISQL/w is a SQL Server 6.5 tool that is provided with SQL Server 7 for backward compatibility. With version 7, you can use the SQL Server Query Analyzer tool instead, which is integrated into the Microsoft Management Console (MMC).
A DNS query in which a name server contacts a second name server to perform a name lookup.
How It Works
In a typical Internet name lookup (for example, www.alpine.expedia.com), a resolver sends a recursive query to a locally accessible name server such as a name server maintained by your local Internet service provider (ISP). If the local name server cannot resolve the name because it is outside of its zone of authority and it is configured as a forwarder, the server performs an iterative query to a root name server, which responds with the IP address of a name server whose zone of authority includes the desired top-level domain (.com). The local name server then performs an iterative query with this top-level name server, which responds with the IP address of a second-level name server whose zone of authority includes the desired second-level domain (expedia.com). The local name server contacts this second-level name server and resolves the fully qualified domain name (FQDN) into its IP address or returns an error if the query cannot be resolved.
See also inverse query, recursive query
See International Telecommunication Union (ITU)
A Microsoft Windows NT user account created when Internet Information Services (IIS) is installed. The IUSR_ComputerName account, in which ComputerName is the NetBIOS name of the Windows NT or Windows 2000 server on which IIS is installed, is also known as the anonymous account because it is designed to allow anonymous access to World Wide Web (WWW) and File Transfer Protocol (FTP) sites on IIS.
How It Works
The IUSR_ComputerName account is given a randomly assigned password and is made a member of the Guests local group. The account is also granted the sole system right “log on locally” so that when users on the Internet try to anonymously access a WWW or FTP site on IIS, they are authenticated as if they had logged on locally to the system console (instead of being authenticated as normal network users). This secures the computer against unauthorized network access. Once a user is authenticated as an anonymous user, he or she transparently uses the IUSR_ComputerName account to gain access to files on the WWW or FTP sites of interest.
NOTE
The IUSR_ComputerName account is automatically included in the built-in Guests local group on the server on which IIS is installed, so be sure to review the permissions and rights that you have granted to the Guests group.
TIP
You can change the password of the IUSR_ComputerName account using User Manager for Domains, but if you do so you should use Internet Services Manager to ensure that this password is synchronized with the password specified for the account in the IIS property sheets. Select the Enable Automatic Password Synchronization setting in Internet Services Manager to ensure this.
See inter-exchange carrier (IXC)
