The part of your network that ties different departmental networks into a single whole. The backbone carries the bulk of the network traffic and must be designed accordingly.
Graphic B-1. Two types of backbone: distributed and collapsed.
How It Works
Backbones are primarily used in medium to large-sized networks, such as those occupying a building or a group of buildings on a campus. These backbones generally fall into two basic categories:
Distributed backbone: Refers to using cabling to join different departmental networks in a bus topology or mesh topology. This cabling is referred to as backbone cabling, and it connects the hubs, switches, or routers of each network into a single whole. In a typical scenario, each floor or building might have a local area network (LAN) and wiring closet containing, among other things, a main hub or router. Backbone cabling is then run between floors or buildings, connecting the main hub or router for each department into a bus-style network (see illustration).
Collapsed backbone: Refers to using cabling to directly join each departmental network’s main hub or router using backbone cabling to a central hub, switch, or router in a star topology (see illustration). The central unit is often referred to as the collapsed backbone, although this term properly describes the entire configuration. The central unit can be located in the building’s main equipment room or, in a campus scenario, in the IS department’s building.
Distributed backbones generally have a greater degree of fault tolerance than collapsed ones, because the collapsed backbone unit forms a single point of failure. However, collapsed backbones usually have better traffic flow than distributed backbones because of the underlying star topology. Collapsed backbones generally offer better performance because of the reduced number of hops that traffic must make when passing between departmental LANs. Collapsed backbones are also easier to manage because they bring all the backbone switching and routing equipment into a single room or building. Collapsed backbones are used frequently for connecting departmental LANs within a single building, but less often for connecting building LANs across a campus network because of the increased distances and cabling costs.
Backbone cabling should have the highest bandwidth of any cabling in your network, since backbones are used to join together hubs, switches, and routers, linking departmental LANs or subnetworks into building-wide or campus-wide internetworks. In buildings, backbone cabling often refers to the vertical cabling running through the rises or elevator shafts that connects the hubs and switches in each floor’s wiring closet. Depending on performance requirements, anticipated growth, and cost, any of the following might be suitable for backbone cabling:
Cat5 UTP cable
Type 1A STP cable
Thinnet coaxial cabling
Multimode fiber-optic cabling
Single-mode fiber-optic cabling
NOTE
The term “backbone” is also used to refer to the collection of networking components (cabling, hubs, switches, and routers) that form the supporting network into which workgroup and departmental LANs are connected and joined together. A mesh topology is often used for network backbones to provide fault tolerance for critical high-speed data paths.
TIP
You should put considerable thought and planning into the design and implementation of your network’s backbone, as the overall performance of networking services is largely dependent on the bandwidth and reliability of the backbone. Design your backbone with network expansion in mind. Planning for growth is especially important if the cable reinstallation cost is high. Fiber-optic cabling is preferred for most network backbones because of its high bandwidth, security, and resistance to electromagnetic interference.
See also collapsed backbone
A router that is used to connect autonomous systems in a large internetwork such as the Internet.
Graphic B-2. Backbone router.
How It Works
Autonomous systems are large portions of an internetwork that fall under the administration of a single authority. In an autonomous system, routers exchange information with each other using routing protocols called Interior Gateway Protocols (IGPs), such as the Routing Information Protocol (RIP) and the Open Shortest Path First (OSPF) Protocol. Backbone routers are then used to connect the various autonomous systems into a single internetwork. Backbone routers also exchange information using Exterior Gateway Protocols (EGPs), such as the Border Gateway Protocol (BGP).
Backbone routers must have high performance and reliability because they are typically used to aggregate and route traffic from dozens or hundreds of physical local area network (LAN) segments and to maintain routing information for thousands of machines. Backbone routers can cost from $10,000 to $100,000 each, or more. They come with dedicated operating systems, such as Cisco Systems’ Internetwork Operating System (IOS).
See also routing
The process that enables the transmission of messages between similar messaging systems by making use of a different type of intermediate messaging system. For example, Microsoft Exchange Server can use an existing public or private backbone messaging system to implement an Exchange Server–based messaging system. Exchange Server can also be used for linking other mail systems such as legacy Microsoft Mail networks.
Graphic B-3. Backboning.
How It Works
A simple backboning example is the connecting of two or more Lotus cc:Mail postoffices using an Exchange Server organization as the messaging backbone. By installing the cc:Mail Connector on Exchange Server, messaging connectivity can be established with connected cc:Mail postoffices. Messages can then be routed from one postoffice through the Exchange organization to other postoffices on the network.
Another example of backboning is the connecting of different sites in an Exchange Server organization using a public or private messaging network. Here are two possible scenarios:
Using Simple Mail Transfer Protocol (SMTP) hosts on the Internet to connect Exchange sites. To do this, the Internet Mail Service can be installed on appropriate Exchange servers.
Using a public or private X.400 messaging system for connecting Exchange sites using the X.400 Connector.
NOTE
The term “backboning” is sometimes used to describe the core messaging paths set up for a large Exchange organization, regardless of whether messaging systems other than Exchange are involved.
TIP
When using a public messaging backbone (or a private one owned by a different company) for connecting your Exchange sites, you should consider the following:
Installing and configuring appropriate messaging connectors on suitable messaging bridgehead servers
Establishing and maintaining directory replication between Exchange sites
Handling background traffic from other users of the backbone
Tuning messaging performance to optimize use of the backbone
Implementing a suitable topology for the messaging backbone
For very large Exchange organizations, use a hub and spoke topology instead of a mesh topology. Hub and spoke topologies have less redundancy and fault tolerance, but mesh topologies have routing tables that grow exponentially with the number of sites involved. Mesh topologies for large organizations can lead to routing tables that are so large they degrade the performance of the message transfer agents, even on high-performance servers.
Any program that runs while the user performs another task on the system—for example, a spreadsheet (background program) that calculates data while the user types a letter using a word processor (foreground program).
Operating systems usually assign fewer CPU resources to background programs than to foreground ones. In Microsoft Windows NT, the System utility in Control Panel allows you to boost the performance of the foreground application over any background applications running. Setting the performance boost to None gives both foreground and background applications equal processor time, while setting it to Maximum gives foreground applications greater priority.
In Windows 2000, the System utility in Control Panel offers you one of the following options for optimizing performance:
Applications: Provides more CPU resources to the foreground program and allocates short, variable quanta to running applications
Background Services: Divides CPU resources equally among the foreground program and any running background programs and allocates long, fixed-length quanta to applications
TIP
Select None for a performance boost on Windows NT servers. This will optimize the performance of the server for servicing network requests. Select Maximum on Windows NT workstations to optimize responsiveness for user applications.
See Microsoft BackOffice
A copy of important data. Performing regular backups is one of the main components of a company’s disaster recovery policy, and the importance of doing so cannot be stressed enough. Various occurrences can lead to data loss on a corporate network:
Disk failures caused by hardware failure, power outages, or improper use
Network problems leading to lost packets that are not acknowledged because of router congestion or other situations
Virus infection, resulting in corrupted files
Sabotage by hackers or disgruntled employees, resulting in erased data
Theft of hardware from the premises
To guard against these occurrences—or rather, to prepare for them, since they are, to a certain extent, inevitable—establish a disaster recovery policy that includes a reliable backup plan. In today’s business world, where data is the lifeblood of the enterprise, a comprehensive plan is essential. The following steps are recommended when creating such a plan:
Decide what kind of backup storage devices to use. Options range from small digital audio tape (DAT) drive units capable of backing up several gigabytes of data, to large automated tape libraries capable of handling terabytes of centralized data storage. Other backup options include optical storage libraries and removable disks such as Iomega’s Zip drive disks or Imation SuperDisk disks.
Decide whether to back up servers with dedicated, locally connected storage devices or over the network to centralized backup libraries. Network backup systems suffer from a single point of failure (the network itself) but are simpler to administer than a multitude of individual backup units.
Decide whether individual users’ workstations should also be backed up. A more cost-effective option is to educate users to always save their work on a network share located on a server that is regularly backed up.
Decide how to secure the storage of backup tapes and other media. Will duplicate copies be stored both on site (for easy access if a restore is needed) and off site (in case the company’s building burns down)? Make sure the storage facilities are climate controlled and secure.
Decide what kind of backup strategy to employ. A backup strategy is a combination of a backup schedule and various backup types, including normal, copy, incremental, differential, and daily copy backup types. Also consider whether you will verify all tapes immediately after each backup is performed.
Assign various aspects of the backup procedure to the responsible party. One option some companies now use is to back up data over the Internet to a third-party backup service provider that stores and maintains the backed-up data. This method involves issues of trust and of the Internet connection as a point of failure.
Test backups periodically to ensure that they are actually readable. Nothing is worse than thinking you have a backup when in fact it is unreadable.
To enable administrators to perform regular backups, Microsoft includes backup utilities with all versions of Microsoft Windows, such as the Backup tool in Windows 2000.
See also backup strategy, backup type, tape backup, Windows Backup
See Microsoft Backup, Windows Backup
A service that can be installed on a server or workstation to allow files and folders on the computer to be backed up remotely over the network to a tape backup unit or another form of backup storage media. Instead of installing a tape backup unit on each server and backing it up locally, you can use a backup agent to back up multiple servers on the network, centrally. Centralized tape backup libraries are expensive but simpler to administer than a multitude of individual tape drives.
How It Works
Microsoft Windows 95 and Windows 98 include two backup agents that allow centralized, network backup of users’ workstations:
Backup Exec Agent from Seagate (now Veritas)
ARCServe Agent from Cheyenne
To use either of these agents, you must install the agent on each computer you want to back up, and your system administrator must purchase and install the corresponding server-based network backup software from the same company and install it on the server to which a tape drive is attached. Once this is done, your administrator uses the server-based backup software to schedule frequency of backups, and the users of the computers being backed up can specify which files to back up by configuring the Properties of the installed backup agent on their computers.
A computer running Microsoft Windows NT involved in supporting the functions of the Computer Browser service.
How It Works
A backup browser is a machine that obtains a copy of the browse list from the master browser. The browse list contains information about which shared resources are available to client machines on the network and about which domains are on the network. Backup browsers automatically contact the master browser every 12 minutes to request a copy of the browse list. If the contact is successful, the master browser issues the list to the backup browser. If the backup browser cannot contact the master browser, it starts a browser election to force a new master browser to be selected.
Once the backup browser has the browse list, it caches the list and distributes it to any client that requests it. To request the browse list from a backup browser, a client calls the NetServerEnum application programming interface (API) on the backup browser.
NOTE
There will be one backup browser for every 32 systems in a given domain or workgroup on the network. The Computer Browser service determines the number of backup browsers necessary to ensure that clients can have efficient access to network resources.
Graphic B-4. Backup browser.
See also Computer Browser service, domain master browser, master browser, potential browser
A representation of the results of performing a backup of servers on a network. Backup software such as the Microsoft Windows NT administrative tool Windows NT Backup and Backup in Windows 2000 create catalogs so that backed up files are documented and can be found when performing a restore. Windows NT Backup stores its catalogs on the backup storage media themselves. These catalogs are then loaded into memory when the program is run. Catalogs can also be saved to disk and can be printed for documentation purposes.
Example
On the Windows NT platform, the administrative tool Windows NT Backup creates two different types of backup catalogs:
Tape catalog: Lists the details of all backup sets that have been stored on the tape. If a backup operation spans several tapes, the tape catalog is located on the last tape of the series, because it is created at the end of the backup operation.
Backup set catalog: Lists the details of files and folders included in a specific backup set. A backup set catalog is saved at the end of each backup set on the tape. This catalog is used by the Windows NT Backup program to store a summary of the file and directory information for the backup set, the number of tapes in the backup set, and the date on which the backup was performed.
TIP
If a backup operation spans several tapes and the last tape is missing or damaged, the tape catalog will not be available. However, you can still obtain a complete list of the various backup sets on the tapes by running Windows NT Backup from the command line using the ntbackup command with the /missingtape switch.
See also backup set
A Microsoft Windows NT domain controller containing a read-only copy of the master domain directory database located on the primary domain controller (PDC). A Windows NT domain can have zero or more backup domain controllers (BDCs) for load balancing and redundancy. The BDCs periodically undergo directory synchronization in a Windows NT domain by retrieving a copy of the directory database from the PDC. A BDC can perform logon validation and authentication like a PDC, but it cannot manage accounts—for example, it cannot change user passwords.
Graphic B-5. Backup domain controller (BDC).
NOTE
The placement of BDCs in wide area networks (WANs) that are based on Windows NT is an important issue. In a master domain model scenario, user accounts are centralized in a master domain located at company headquarters, while users and shared network resources are distributed in resource domains located at branch offices in different locations. The users in this scenario must log on to the master domain in order to access resources in the enterprise. There are two ways of facilitating this:
Locate all BDCs belonging to the master domain at headquarters. Unfortunately, when users at the branch offices want to log on, they will have to use the relatively slow WAN link to do so. The additional logon traffic can cause congestion on the WAN link, particularly at certain times of the day.
Locate one or more BDCs belonging to the master domain at each branch office (resource domain). This will facilitate logons by users located at branch offices, since they can log on to one of these BDCs locally instead of being validated over the relatively slow WAN link by a domain controller at headquarters. However, directory replication traffic between the BDCs located at the branch offices and the PDC at headquarters can cause congestion over the WAN links. To make directory synchronization more efficient over the WAN link, registry parameters such as ReplicationGovernor and ChangeLogSize can be adjusted, and batch files can be scheduled using the at command to configure different replication rates at different times of the day.
TIP
Every Windows NT network should have at least one BDC for fault tolerance. If the PDC fails, the BDC can be promoted to take its place. One BDC can support approximately 2000 users on a network, but many factors can affect this figure.
See also domain controller, primary domain controller (PDC)
In Microsoft Windows NT, users who are assigned the responsibility to back up and restore servers on a network. To make an individual a Backup Operator, simply make him or her a member of the Backup Operators group. Backup Operators can exist on Windows NT domain controllers, on member servers, and on workstations. In Windows 2000, Backup Operators are members who have a similar function and belong to the built-in group called the Backup Operators built-in group.
Backup Operators have the preassigned right to log on locally to a computer and to back up and restore files and directories on the system. Backup Operators also have the right to shut down the system. Backup Operators do not need permissions assigned to them in order to back up a particular file or directory—they have a broad system right to do so.
TIP
Backup Operators should be assigned only in enterprise-level networking environments. In small to medium-sized networking environments, backing up and restoring servers is often the responsibility of the administrator.
See also Backup Operators built-in group
In Microsoft Windows NT, a built-in group existing on all Windows NT–based servers and workstations whose members have the right to back up and restore files on the computer regardless of the permissions protecting those files. In Windows 2000, a built-in group existing on all Windows 2000–based servers and workstations. The Backup Operators built-in group is a local group with the following preassigned rights:
Log on locally
Back up files and directories
Restore files and directories
Shut down the system
TIP
If you want a user to be able to back up files and directories on any domain controller in a domain, place the user in the Backup Operators group on any domain controller. Since all domain controllers share the same directory database, the user will be a member of the Backup Operators built-in group for all domain controllers. However, if you want a user to be able to back up a member server, place the user in the Backup Operators built-in group that is a local group on that particular member server.
See also built-in group, built-in local group
A collection of files and folders on a backup tape that were saved in a single Microsoft Windows NT Backup operation. (Windows 2000 Backup can back up files to other media types, such as hard disks.)
You have several options for creating backup sets:
Multiple backup sets can be saved on a single backup tape by appending each new set to the last one.
A backup set can span multiple tapes if you have a large quantity of information to back up.
Tapes can be overwritten so that a new backup set replaces the old.
Graphic B-6. Backup set.
Windows NT Backup creates a backup set catalog for each backup set. This catalog lists the various files and directories that have been backed up, and it can be used for restoring individual files or directories, or printed for documentation purposes. The backup set catalog is saved at the end of each backup set on the tape. A backup set map at the end of the tape locates all backup sets on the tape.
NOTE
A copy of the local system’s registry can also be included in the backup set for a Windows NT system. Backup sets are described with friendly names up to 32 characters long.
See also backup catalog
A Microsoft Message Queue (MSMQ) Server that contains a read-only copy of the primary site controller (PSC) or primary enterprise controller (PEC) database. MSMQ sites do not require backup site controllers (BSCs), but at least one backup site controller should be installed in each MSMQ site for load balancing and failure recovery. A PSC or PEC must be installed before you can install any backup site controllers. The BSC also functions as an MSMQ Routing Server. In this capacity, the BSC provides intermediate store-and-forward message queuing services and dynamic routing. BSCs must be installed on computers running Microsoft Windows NT Server, Enterprise Edition.
A plan for performing backups to ensure against data loss. Backup strategies should take the following into account:
The various backup types that can be performed
The need to archive tapes for long-term data security
The time needed to perform backups and restores
The cost of tapes
The cost of losing data
There is no one right way to implement a backup strategy for resources on a network of computers. To select the best backup strategy for your network, you must consider each of the items in the preceding list and balance them against each other. Your strategy should be simple, efficient, and reliable. The following table shows some examples of backup strategies.
Possible Backup Strategies
| Backup Strategy | Advantages | Disadvantages |
| Normal backups Monday through Friday. | Most secure—every tape contains all backed up files | Longest time to back up |
| Normal backup Monday; differential backups Tuesday through Friday. | Less time to restore | More time to back up |
| Normal backup Monday; incremental backups Tuesday through Friday. | Less time to back up | More time to restore |
| Use a separate tape for each weekday, and archive Monday’s full backup tape weekly or monthly. | Less chance of data loss | Higher cost, since more tapes are needed |
| Use the same tape for each weekday, and archive the tape each week or month. | Cheaper—only one tape required per week or month | Greater chance of data loss, since using only one tape |
See also backup, backup type
A particular method for performing a backup of files and directories. Each type of backup has a different function in an overall backup plan. Most network backup software (such as Microsoft Windows NT Backup and Windows 2000 Backup) supports five backup methods:
Normal backup: Backs up everything that is selected to be backed up. Normal backups are the fastest and easiest to restore. Normal backups are sometimes referred to as “full backups.” Use a normal backup when you want to ensure that all your critical system and data files are backed up in a single operation. If your backup cycle consists only of normal backups and you need to perform a restore, you need to use only the most recent normal backup to do so.
Copy backup: Primarily used to produce an additional copy of a backup—for example, a copy to send to the accounting department for monthly archiving and reporting. While a copy backup backs up the same files as a normal backup, there is a difference between the two operations. Performing a normal backup clears the archive bit on each backed up file and marks them as having been backed up. A copy backup, however, does not modify the archive bit on the files backed up. In other words, you can perform a copy backup at any time in a backup cycle without interrupting the cycle in any way—the copy backup is distinct from the backup cycle and is not required when a restore is performed from the cycle’s set of tapes.
Incremental backup: Backs up only files that have been created or modified since the last normal or incremental backup. Files that are backed up in an incremental backup have their archive attributes cleared to indicate that they have been backed up. Using a combination of normal and incremental backups takes less time and uses less storage space than performing only normal backups. However, if you need to perform a restore, you typically need to use the normal backup plus every incremental backup from the current backup cycle to do so.
Differential backup: Copies those files that have been created or changed since the last normal or incremental backup. Files that are backed up by a differential backup do not have their archive attributes cleared, which means that these files will be backed up again in any succeeding differential backups. Differential backups are cumulative with regard to changes—that is, each differential backup in a given backup cycle contains all the files from the last differential backup, plus any files that have been modified since the last differential backup. Thus, if you need to perform a restore, you will typically need to use only the normal backup and the most recent differential backup from the current backup cycle to do so.
Daily copy backup: Copies all files that have been modified on the day the daily copy backup is performed. This method is sometimes used to make a copy of all files a user worked on in a day so that he or she can take them home to work on. Like a copy backup, the daily copy backup does not modify the archive bit of the files backed up; therefore, the daily copy backup does not interrupt the backup cycle in any way.
NOTE
Different types of backup operations have different effects on the archive attributes of the files and directories they back up. A backup operation marks the archive attribute by clearing it to indicate that the file has been backed up. If the file is later modified in some way, its archive attribute is set (unmarked). This next table shows what each type of backup operation does to the archive attribute:
Effects of Backup Operations on the Archive Attribute
| Backup Type | Archive Attribute |
| Normal | Cleared |
| Copy | No effect |
| Incremental | Cleared |
| Differential | No effect |
| Daily copy | No effect |
See also backup, backup strategy
A wizard that is part of the Backup tool in Windows 2000 that can be used to perform a backup. The Backup Wizard starts by letting you choose among the following:
Backing up all files on the computer on which it is running.
Backing up files and folders that you specify. These files and folders can be either on the local computer or on any shared location on the network.
Backing up Active Directory and the registry on the computer on which the wizard is running. Active Directory can be backed up only on a domain controller.
The wizard then leads you through the process of specifying a backup location and other advanced backup options, such as verification, compression, and remote storage. You can also schedule a backup job to run unattended at a later time when users have stopped working and all files are closed.
NOTE
The Microsoft Backup tool for Windows 98 also includes a Backup Wizard with similar capabilities.
An electrical cable consisting of pairs of conductors that have identical electrical characteristics with respect to each other and with respect to ground. The typical example in computer networking is the twisted-pair cabling used in 10BaseT Ethernet networks.
How It Works
In a balanced line, both of the two wires are carrying current at any given instant. However, at any particular moment, the directions of the current in the wires are opposite each other. This condition is also described by saying that the currents in the wires are 180 degrees out of phase with each other at any given moment. Both wires have voltages that are above ground potential, but the potentials of the wires are different with respect to ground, resulting in a flow of current. The wire pair is twisted in order to ensure that the electromagnetic radiation produced by both wires is effectively canceled out, reducing the overall electromagnetic interference (EMI) produced by the wires and reducing their sensitivity to induced currents from external sources of EMI.
TIP
A balun can be used to connect a balanced line to an unbalanced line.
See also balun, unbalanced line
Stands for bal anced un balanced. A device used to connect balanced lines and unbalanced lines. Balanced and unbalanced lines have different electrical characteristics. A balun matches these characteristics by providing impedance transformation between the two different lines. Baluns can be used for various types of connections between different wiring systems:
Graphic B-7. Balun.
Twisted-pair cabling to coaxial cabling: Typically used for connecting 10BaseT networks with 3270 equipment running on coax or twinax networks
Twisted-pair cabling to token ring cabling: Used for matching token ring Type 1 cabling to standard unshielded twisted-pair (UTP) cabling to connect 10BaseT or faster hubs or adapters with RJ-45 ports into a token ring network
Asynchronous Transfer Mode (ATM) cabling to token ring cabling: Used for connecting token ring networks to high-speed ATM hubs in campus backbone networks
See also balanced line, unbalanced line
In general, the difference between the highest and lowest frequencies in a given range of frequencies for an analog signal. For example, if the lowest and highest frequencies a telephone line can carry are 300 Hz and 3300 Hz, the telephone line can accommodate a bandwidth of 3300 – 300 = 3000 Hz, or 3 kHz.
In computer networking with digital signals, bandwidth is the capacity of a communication channel for carrying signals. The greater the bandwidth, the more data can be transferred in a given time. Bandwidth is sometimes referred to as “throughput,” and for digital communication, it is usually measured in bits per second (bps) or a multiple thereof (Kbps, Mbps, Gbps, and so on).
NOTE
For fiber-optic cabling, the bandwidth is usually expressed in units of MHz-km. For example, a cable rated at 500 MHz-km could carry 500 Mbps of data a distance of 1 kilometer, 250 Mbps of data a distance of 2 kilometers, 100 Mbps of data a distance of 5 kilometers, and so on.
A multilink remote access protocol supported by Microsoft Windows 2000 that dynamically controls how bandwidth can be allocated for multilink connections using the Point-to-Point Protocol (PPP). Bandwidth Allocation Protocol (BAP) makes multilink connections more efficient by allocating lines only as required, thus eliminating wasted bandwidth. This is especially useful if the telecommunications carrier being used for the PPP connection charges by the amount of bandwidth being utilized by the customer.
BAP allows the administrator to configure the PPP server to specify which particular Multilink PPP (MPPP) lines can be added or dropped. The administrator also specifies which bandwidth thresholds must be crossed before additional lines are added or existing ones are dropped. BAP is especially useful over Integrated Services Digital Network (ISDN) connections, because these dial-up services can almost instantly add or drop lines.
BAP is provided in Windows 2000 as an additional enhancement to the Routing and Remote Access Service (RRAS) of Windows NT 4.0. BAP is defined in Request for Comments (RFC) number 2125.
Any telecommunications technology that provides both a permanent, dedicated connection and the capability of quickly increasing bandwidth when needed by users. Many telecommunications devices incorporate bandwidth-on-demand features of various types. For example, some Integrated Services Digital Network (ISDN) devices used for Basic Rate Interface ISDN (BRI-ISDN) can be configured to use the second ISDN B channel only when the utilization of the first channel exceeds a certain threshold. If this threshold is exceeded for a specified period of time, the second B channel automatically opens up to facilitate and speed data transfer. Once the data rate has dropped below the threshold, the second B channel shuts down until it is needed again. The ISDN technology for accomplishing this combining of channels is called bonding. Many Asynchronous Transfer Mode (ATM) products also support various bandwidth-on-demand features.
Bandwidth-on-demand technologies are typically used in bursty networking situations in which high transmission speeds and capacities are required for transporting video, voice, and data on common networking circuits. Bandwidth-on-demand configurations often involve a mix of leased-line services and circuit-switched telecommunications services, and they can save users money by opening additional circuits only on an as-needed basis. Networks that make use of bandwidth on demand can be designed to supply additional bandwidth under conditions such as
Exceeding a specified threshold of network traffic
Scheduling for expected peak periods of the day
Failover in case the permanent link goes down
Generally, any networking technology that controls the amount of network bandwidth used by servers, applications, or network communication paths. In the context of Microsoft Internet Information Services (IIS), for example, bandwidth throttling is a technique for controlling the amount of network bandwidth used by individual Web sites hosted on the server. Bandwidth throttling can be used to prevent hits on a popular site from overwhelming the server and preventing other sites hosted on the server from being accessed by clients.
For example, if five Web sites are being hosted on a single machine running IIS but one of them is extremely popular, the other sites might get starved for bandwidth and users might have difficulty connecting to them. In order to rectify this situation, a specific maximum bandwidth level can be allocated to the popular site with the Internet Services Manager snap-in used for administering IIS using the Microsoft Management Console (MMC). If this maximum bandwidth is exceeded, no further connections to that site are allowed until the bandwidth utilization level drops below the threshold. This allows the unallocated bandwidth to be shared among the remaining less popular sites so that users can connect to them.
Stands for Banyan Virtual Integrated Network Service, a network operating system (NOS) for building enterprise-level networks. VINES was originally based on a proprietary family of protocols that was derived from the Xerox Network Systems (XNS) protocol. VINES uses a client/server distributed networking architecture for allowing clients to access network resources on servers over the network. VINES includes such features as
Basic file and print sharing
A distributed directory service called StreetTalk for managing networks
Support for the TCP/IP protocol
Graphical administration tools
Support for Simple Network Management Protocol (SNMP) management
VINES includes clients for MS-DOS, OS/2, Microsoft Windows, and Macintosh platforms as well as optional applications for integrating Windows NT, AppleTalk, Novell, and UNIX networks into existing VINES-based networks.
How It Works
VINES is built on a client/server model in which clients can make requests for services from servers on the network. The VINES protocol stack consists of five basic layers that map to the seven-layer Open Systems Interconnection (OSI) reference model as follows:
Physical and data-link layers: VINES can operate over Ethernet, token ring, X.25, and other types of networking architectures.
Network layer: The main protocol here is the VINES Internetwork Protocol (VIP), which is similar in function to the Internet Protocol (IP) of the TCP/IP protocol suite. VIP encapsulates data and addresses it using a 48-bit address that contains a 32-bit network number and a 16-bit host number. Dynamic address assignment and address resolution are performed using VINES servers, which are referred to as service nodes. VINES clients obtain their addresses dynamically from the nearest server on the network. Multihomed servers function as routers, and routing tables are maintained by periodic announcements from clients and servers. Other network layer protocols include an Address Resolution Protocol (ARP), an Internet Control Protocol (ICP), and a Routing Table Protocol (RTP).
Transport layer: For reliable delivery of data using acknowledgments and sequence numbers, VINES uses its Reliable Message Service. Another service, the Unreliable Datagram Service, supports only best-effort delivery of packets. Finally the Data Stream Service can be used to transmit large amounts of data using virtual circuits with flow-control mechanisms.
Session and presentation layers: VINES implements the standard remote procedure call (RPC) mechanism for enabling communication between VINES client and server components on different stations on the network.
Application layer: VINES supports standard file and print services, directory services (StreetTalk), and a number of other application layer services and protocols.
TIP
When connecting Windows 95 or Windows 98 clients to a VINES-based network, use the 32-bit client for Windows that comes with VINES instead of the 16-bit VINES client included with Windows 95 and Windows 98.
On the Web
•
Banyan home page : http://www.banyan.com
See Bandwidth Allocation Protocol (BAP)
A signaling technology that sends digital signals over a single frequency as discrete electrical pulses. The entire bandwidth of a baseband system carries only one data signal and is generally less than the amount of bandwidth available on a broadband transmission system. The baseband signal is bidirectional so that a baseband system can both transmit and receive signals simultaneously. Baseband signals can be regenerated using repeaters in order to travel longer distances before weakening and becoming unusable because of attenuation. Baseband transmission technologies do not use modulation, but they can use time-division multiplexing (TDM) to accommodate multiple channels over a single baseband transmission line.
Common local area network (LAN) networking technologies such as Ethernet use baseband transmission technology. All stations on a baseband network share the same transmission medium, and they use the entire bandwidth of that medium for transmission. As a result, only one device on a baseband network can transmit at a given instant, resulting in the need for a media access control method to handle contention.
See also broadband transmission
A set of data that indicates normal usage of monitored network resources. The Microsoft Windows NT administrative tool Performance Monitor and the Microsoft Windows 2000 snap-in called System Monitor can be used to collect data for the present performance of your network to establish a baseline. Then, if you upgrade hardware or add new users, the performance of the network can be measured again and compared with the baseline to determine trends, identify bottlenecks, and measure capacity.
How It Works
Creating a baseline for server and network activity begins with the process of identifying which server and network resources should be systematically measured. Generally, you always want to measure at least the following four resources: memory, processor, disk, and network subsystems. Using Performance Monitor or System Monitor, you should collect data for the objects shown in the table.
Resources and Corresponding Performance Objects to Monitor Performance
| Resource | Objects to Collect |
| Memory | Memory, cache |
| Processor | Processor, system, server work queues |
| Disk | Logical disk, physical disk |
| Network | Server, network interface, network segment |
These performance objects should be regularly captured for a period of time in order to collect the data needed to establish the baseline. Generally, you should append each log file collected to a master log file using relogging. Focus on periods of peak server and network activity, and collect at least a week of measurements to establish your baseline.
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If you want to collect disk subsystem data, first enable disk objects using the diskperf command. Make sure you use a computer that is not being monitored to create your measurement baseline log files so that the activity of the computer doing the monitoring will not affect the data being collected.
Also called “Clear-Text Authentication,” an authentication method that passes a user’s credentials over a network of computers in an unencrypted form. Basic Authentication is not a secure authentication scheme, since anyone who can intercept network traffic and read it using a protocol analyzer can obtain the user’s credentials.
Basic Authentication is one of three authentication schemes available on Microsoft Internet Information Services (IIS). Basic Authentication is often used in a UNIX environment for authenticating remote HTTP users. Basic Authentication is discussed in Request for Comments (RFC) numbers 1945, 2068, and 2069.
NOTE
Basic Authentication encodes a user’s credentials using a well-known public encoding algorithm known as uuencoding. Because the algorithm is well known, it is easy to decode uuencoded text.
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Enable Basic Authentication on IIS to restrict access when you have clients that do not support Microsoft Windows NT Challenge/Response Authentication, or to support authentication through a firewall or proxy server. Note that for Basic Authentication to work on IIS, the users being authenticated must have the right to Log On Locally to the IIS server. Make sure that you use the NTFS file system to secure files on your system. To make Basic Authentication more secure, implement the Secure Sockets Layer (SSL) protocol.
See also anonymous access, Windows NT Challenge/Response Authentication
In Microsoft Windows 2000, a physical disk that can contain primary partitions, extended partitions, and logical drives. Basic disks can be accessed by MS-DOS and legacy Windows platforms. Basic disks can also contain volumes created using Windows NT version 4.0 or earlier, such as spanned volumes (volume sets), striped volumes (stripe sets), mirrored volumes (mirror sets), and RAID-5 volumes (stripe sets with parity).
Basic disks are the default type of disk in Windows 2000. All disks are basic disks unless you convert them to dynamic disks. Basic disks can have two kinds of partitions:
Primary partitions: Basic disks support up to four primary partitions, only one of which can be marked as active.
Extended partitions: Basic disks support only one extended partition, which can be further subdivided into logical drives or logical volumes.
NOTE
You can create only basic volumes on basic disks. You cannot create new simple, spanned, striped, mirrored, or RAID-5 volumes on basic disks.
See also dynamic disk
A standard form of communication on Integrated Services Digital Network (ISDN) communication systems. Basic Rate Interface ISDN (BRI-ISDN) connections consist of two B channels and one D channel. The B channels carry the voice or data between the customer premises and the telco’s central office (CO), while the D channel is used for establishing connections and signaling. BRI-ISDN is often referred to as 2B+D because of the channels that it uses.
The bandwidth of each B channel is 64 Kbps, so the total bandwidth of BRI-ISDN is twice that, 128 Kbps. This bandwidth can be used as two separate communication links of 64 Kbps each, or it can be combined using bonding into a single 128-Kbps communication link. The bandwidth of the D channel is 16 Kbps.
BRI-ISDN connections at customer premises can be connected directly to a switch at the telco’s central office, an ISDN call controller that is linked to the CO, an ISDN Private Branch Exchange (PBX), or some other signaling and communication equipment.
See also Integrated Services Digital Network (ISDN), Primary Rate Interface ISDN (PRI-ISDN)
A type of volume in Microsoft Windows 2000. A basic volume can be created only on a basic disk and can be
A primary partition, extended partition, or logical drive that was created using the Disk Management portion of the Computer Management tool
A volume set, mirror set, stripe set, or stripe set with parity that was created using Windows NT version 4.0 or earlier
See also dynamic volume
A special set of commands that are generally found only in batch files and enable special actions such as conditional processing. Any command supported by an operating system can be included in a batch file, but the commands listed in the table that follows are generally found only in batch files. These commands are all supported by Microsoft Windows 2000, while earlier versions of Windows might support only a subset of them.
Batch File Commands
| Command | Description |
| call | Calls one batch program from another while allowing the calling program to continue running |
| echo | Toggles command-echoing on or off |
| endlocal | Restores environment variables set by a setlocal command |
| for | Used to run a specified command for each file in a set of files |
| goto | Jumps to a specific line that is labeled in a batch file |
| if | Used to perform conditional processing of commands |
| pause | Suspends processing of the batch file and waits for the user to respond |
| rem | Used to insert remarks (comments) in a batch file for documentation purposes |
| setlocal | Initiates localization of environment variables in a batch file |
| shift | Used to change the position of replaceable parameters in a batch file |
Also called a batch program, an ASCII file with the extension .bat or .cmd containing a series of commands. These commands are executed sequentially when the batch file is invoked at the command prompt or in a logon script. Batch files are used primarily to simplify the execution of routine or repetitive administrative tasks such as mapping drives, synchronizing system clocks, or performing backups.
Batch files trace their origin to MS-DOS (the autoexec.bat file is the most well-known example), but they are still used by administrators for logon and installation scripts in Microsoft Windows NT and Windows 2000 and for other administrative purposes. With the advent of the Windows Script Host (WSH)—which is included in Windows 98, Windows 2000, and the Windows NT Option Pack and which allows administrative scripts to be written in higher-level scripting languages such as Microsoft Visual Basic Scripting Edition (VBScript) and JavaScript—the old batch file paradigm might finally be about to disappear.
Example
If you want to control the rate at which directory information is replicated between a backup domain controller (BDC) and a primary domain controller (PDC) on a Windows NT–based network, you can create a batch file that will change the value of the ReplicationGovernor parameter on the BDC. First create a script that has the full path to this parameter in the registry along with the value you want to assign to it, and then create the following simple batch file:
regini <Script_Name> net stop netlogon net start netlogon
Two different scripts and batch files can be created for different times of the day, and the at command can be used to schedule the execution of each batch file at the appropriate time. This illustration is especially useful if directory replication must occur over a slow WAN link, and it can be used to ensure that most replication traffic occurs during off hours.
Stands for bearer channel, a circuit-switched channel for carrying voice or data in Integrated Services Digital Network (ISDN) services. These channels are called bearer channels because they “bear,” or carry, the actual information being communicated between the customer premises and the telco’s central office (CO). B channels are standard, bidirectional, digital telephone channels that can carry digital information at a rate of 64 Kbps. Users with greater bandwidth needs can combine several B channels into larger data-carrying pipes. The two most common configurations are
2B+D: Combines two B channels to form a single data pipe with a total bandwidth of 128 Kbps
23B+D: Combines 23 B channels to form a high-speed data pipe equivalent to a T1 line with a total bandwidth of 1.438 Mbps
NOTE
B channels carry voice or data only, not signaling information. D channels carry information for establishment and control of ISDN connections.
See also Integrated Services Digital Network (ISDN)
A command-line tool for Microsoft SQL Server that can be used to export and import data between SQL Server and other database servers or files. The format of the foreign data source is specified by the administrator. The bcp (“bulk copy program”) utility is typically used for such purposes as
Transferring data between mainframe databases and SQL Server
Transferring large quantities of data to or from computers running SQL Server
Importing or exporting data in ASCII format
How It Works
The bcp utility uses a two-step process for transferring data—the data is transferred first to a file, and then to the server. The different transfer modes available to the bcp utility include
Native mode: Used for transferring data between computers running SQL Server
Character mode: Generates tab-delimited text files for importing into spreadsheets or other database management systems
Format file: Used to transfer specific columns of data
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An advantage of using the bcp utility is the capability of using it in a batch file for automating transfer of data between different platforms.
See backup domain controller (BDC)
A technique used on token-passing networks for monitoring the status of the token-passing process. Beaconing is used in token ring and Fiber Distributed Data Interface (FDDI) networks to ensure that token passing is functioning properly.
How It Works
On a token-passing network such as FDDI, every station is responsible for monitoring the status of the token-passing process. If a station detects that a fault has occurred, it starts placing beacons onto the ring. When the next station on the ring detects a beacon, it in turn starts placing beacons on the ring, and the first station stops transmitting them. This process will continue until the station immediately upstream of the fault location is the only station sending beacons. This allows administrators to quickly locate the fault and repair it. Once the fault is fixed, the station emitting the beacon detects its own beacon returning to it after traveling around the ring, and the station stops beaconing.
A computer operating system developed by Be, Inc., a company that was founded in 1990 by Jean-Louis Gassée, a former president of Apple’s product division. BeOS is a preemptive multitasking operating system with symmetric multiprocessing (SMP) support and an object-oriented set of application programming interfaces (APIs) optimized for real-time digital multimedia and communication functions. Because of this, BeOS is sometimes called a “media OS” to emphasize its multimedia capabilities. BeOS runs on Intel-based platforms and certain PowerPC-based hardware, and it includes basic TCP/IP support and services. On a PowerPC, you can even run the MacOS as a shell within the BeOS desktop interface.
On the Web
•
The Be, Inc., home page : http://www.be.com
See Border Gateway Protocol (BGP)
Stands for Berkeley Internet Name Domain, a popular software tool for administering and maintaining the Domain Name System (DNS) on UNIX platforms. BIND was originally written for BSD UNIX and is currently maintained by the Internet Software Consortium. Because most versions of UNIX include some port of BIND, it is the most popular DNS server used by Internet service providers (ISPs) for administering and maintaining the DNS for the Internet. The DNS server services on Microsoft Windows NT and Windows 2000 are RFC-compliant implementations of DNS and are compatible with BIND.
On the Web
•
Internet Software Consortium home page : http://www.isc.org
In Novell’s NetWare version 3. x and earlier networking operating systems, the database containing network security information (users, groups, rights, and so on) for a particular server. Each NetWare 3. x server has its own bindery for controlling access to that server’s file and print resources. In version 4. x and later, the bindery is replaced by the Novell Directory Services (NDS), although 4. x servers are also capable of running in bindery emulation mode.
Microsoft’s optional service called Gateway Services for NetWare (GSNW) for the Windows NT Server and Windows 2000 Server platforms can be used to implement gateways to resources located on NetWare file and print servers that are using bindery security. This allows Windows users to access volumes, directories, and print queues on NetWare servers without requiring NetWare client software to be installed on them. Client Services for NetWare (CSNW) can also be installed on client machines running Windows NT Workstation or Windows 2000 Professional to enable them to directly access bindery-based NetWare 2. x , 3. x , or 4. x servers that are running in bindery emulation mode.
A mechanism for linking together network interface card (NIC) drivers, network protocols (such as TCP/IP), and networking services (such as Workstation service). Microsoft Windows operating systems allow you to optimize network communication by selectively enabling, disabling, and modifying the order of the bindings between different networking components. Windows NT supports network driver interface specification (NDIS) 4.0, which allows multiple protocols to be independently bound to multiple network interface cards, while Windows 2000 supports the newer NDIS 5.0 specification with enhanced functionality.
How It Works
To configure bindings for Windows NT, Windows 95, or Windows 98, use the Network utility in Control Panel. To configure bindings in Windows 2000, choose Advanced Settings from the Advanced menu of the Network And Dial-Up Connections window, which is also accessed from Control Panel. Bindings can be easily enabled, disabled, or reordered and can also be displayed in different ways, depending on the version of Windows involved. For example, in Windows NT bindings can be displayed as
Connections from services to protocols and then to adapters
Connections from protocols to services
Connections from adapters to protocols and then to services
In Windows 95 and Windows 98, bindings are shown in one list and cannot be reordered. In Windows 2000, bindings are displayed as a single hierarchical list and can be reordered.
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To optimize network performance, disable any unnecessary bindings on your workstations.
Graphic B-8. The Bindings tab shows connections between the network cards, protocols, and services on a particular computer.
See also broadband ISDN (B-ISDN)
A unit used for measuring the speed of transmission of data on a network of computers—that is, the amount of information sent or received in a given amount of time. A bit is a single unit of digital information, represented by either a 1 or a 0. The total number of bits per second (bps) that can be transmitted over a network link represents the bandwidth of that link. Because most network communication takes place at thousands or millions of bits per second, the following related units are commonly used:
Kbps = kilobits per second (103 bps)
Mbps = megabits per second (106 bps)
Gbps = gigabits per second (109 bps)
In an internetwork, a black hole is a router that goes down and whose absence from the network is not detected by other routers. Packets that are forwarded to the black hole are dropped; they never reach their destination, and they give no indication to the stations sending them that this is the case—therefore, the data is lost.
Normally, a router will issue an “ICMP Destination Unreachable” message when it cannot forward a packet. However, with a black hole, these messages are not generated, so the user doesn’t know that data is being permanently lost.
If static routing is being used, a black hole persists until the affected router is brought back on line or until other static routers have their routing tables reconfigured to take the downed router into account. If dynamic routing is used, other routers soon detect the presence of the black hole and adjust their routing tables accordingly to favor other paths.
In Microsoft Windows platforms, a blue screen on a user’s monitor indicates that something has gone seriously wrong with the system. In Windows 2000, this screen is usually called a Stop screen, and it contains complex information that qualified support technicians can use to diagnose the problem. A reboot might get the system going again, but the blue screen might reappear if the problem is not resolved. The problem causing the blue screen to appear can be either hardware-related or software-related, but the blue screen itself is generated by the operating system in response to the underlying problem.
In Windows 95 and Windows 98, the blue-colored screen normally appears when parity errors or memory violations occur. The Windows 98 blue screen requests that you either shut down the offending application or restart your system using Ctrl+Alt+Delete.
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Parity errors can indicate that your system RAM has mismatched single inline memory modules (SIMMs) on your motherboard—for example, RAM with different speeds or a mix of parity and nonparity RAM. Also, systems from some manufacturers require special proprietary RAM in order to function. You should consult the documentation from your computer’s manufacturer or your RAM’s manufacturer to ensure that you have the correct type of RAM in each slot.
An open specification for short-range wireless transmission of voice and data that is currently under development. Bluetooth provides a simple, low-cost method of linking Personal Digital Assistants (PDAs), cellular phones, laptops, and other information appliances. Bluetooth can be used for bridging data networks, connecting peripherals to devices, and forming ad hoc connections between groups of information appliances. Bluetooth is the initiative of a consortium called the Bluetooth Special Interest Group (SIG), whose original members include industry leaders Ericsson, IBM, Intel, Nokia, and Toshiba. More than 850 vendors support it.
How It Works
Bluetooth supports transmission of voice and data over 2.4-GHz radio frequencies, which is the unlicensed Industrial-Scientific-Medical (ISM) band, using a frequency-hopping scheme with a maximum of 1600 hops per second, resulting in a new frequency being used to transmit each packet. This scheme allows for smooth operation—in spite of fading due to reflecting obstacles or excessive distance, and in spite of noise due to electromagnetic interference (EMI), such as that generated by microwave ovens. In addition, Bluetooth uses short packets and fast acknowledgments to increase reliability and employs forward error correction to reduce the effects of random noise.
The range of transmission for Bluetooth is typically between 0.1 and 10 meters but can be as much as 100 meters using higher transmission power. The system’s automatic power adaptation adjusts transmission power to the minimum needed for reliable transmission in any given situation, which reduces the chance of eavesdropping. Bluetooth also includes encryption and authentication mechanisms. The entire Bluetooth technology is implemented in a single 9-millimeter-by-9-millimeter chip.
Bluetooth data transmission normally takes place over an asynchronous channel that provides 721 Kbps in the forward direction and 57.6 Kbps in the return direction, but synchronous data transmission at 432.6 Kbps in both directions is also supported. Time-division duplexing (TDD) is employed to alternate transmission between the two directions and thus provide full-duplex communication. Each TDD slot normally carries one packet, but packets can be spread across up to five slots. Signaling is baseband and uses a binary FM scheme. Channels can be routed by using a combination of circuit switching and packet switching.
Bluetooth voice transmission can use up to three concurrent synchronous 64-Kbps voice-only channels or one channel that simultaneously supports both asynchronous data and synchronous voice transmission. The voice channels use the continuous variable-slope delta modulation coding scheme.
Bluetooth supports concurrent connections among up to eight devices, forming what is called a piconet. Each device is temporarily assigned a unique 3-bit MAC address for the duration of the connection. A master/slave relationship exists between one device and all other devices for the duration of the connection for the purpose of establishing clocking and the hopping sequence. In all other respects, the devices operate as peers during a connection. Unconnected devices are in standby mode and listen for connection attempts every 1.28 seconds on each of 32 preassigned hopping frequencies. Link setup and authentication is performed using the Link Manager Protocol (LMP), which uses the link controller services built into the chip. Connections between devices can be either point-to-point or point-to-multipoint, and piconets can be joined, with each piconet having a different hopping sequence.
On the Web
•
Bluetooth SIG home page : http://www.bluetooth.com
See also wireless networking
A series of connectors used for connecting thinnet coaxial cabling to various networking components. BNC connectors use a twist-and-lock mechanism that provides a secure connection between network cabling and components. BNC connectors are typically used on 10Base2 Ethernet networks. The different types of BNC connectors include the following:
BNC cable connector: Soldered or crimped to the ends of a thinnet cable
BNC T-connector: Used to connect a network interface card (NIC) to a thinnet cable segment
BNC barrel connector: Used to connect two pieces of thinnet cable
BNC terminator: Provides a 50-ohm termination for the free end of a thinnet cable
See also connector (device), terminator
A NetBIOS name resolution method in which broadcast messages are used for name registration and resolution. B-node is one of the NetBIOS name resolutions supported by Microsoft Windows NT and Windows 2000.
How It Works
Name resolution is the process of converting the name of a host on the network into a network address (such as an IP address). Name resolution must be performed in order to establish communication over a network in Windows. B-node is one of four basic methods supported by Windows for resolving NetBIOS host names—that is, computer names—into IP addresses.
If a computer running Windows is configured as a B-node machine, it always uses broadcasts to resolve names of other hosts on the network. For example, if a B-node machine wants to communicate with another machine with the NetBIOS name SERVER7 (for example, if it wants to connect to a shared resource on SERVER7), the B-node machine broadcasts a packet containing a NetBIOS name query request. If SERVER7 receives the packet, it responds by returning a frame containing its IP address. If SERVER7 is off line or fails to return a response, the B-node client will be unable to establish a connection with SERVER7.
As a name resolution method, B-node is flawed in two ways:
Since broadcast packets are used, B-node consumes network bandwidth and can degrade overall network communication in a busy network.
Since routers are usually configured to not forward broadcast packets, B-node clients can resolve only the NetBIOS names of hosts on the client’s local subnet.
A better approach to NetBIOS name resolution on Windows networks is to configure clients as H-node machines and use a WINS server. H-node is a NetBIOS name resolution method that combines B-node and P-node.
See also H-node, M-node, NetBIOS name resolution, P-node
In Integrated Services Digital Network (ISDN) and T-series transmission technologies, a way of combining multiple DS0 channels from different circuits into a single, faster data transmission channel. Bonding involves inverse multiplexing and techniques for resolving timing differences among the different circuits.
Bonding is used in Basic Rate Interface ISDN (BRI-ISDN) for combining the two 64-Kbps B channels into a single 128-Kbps data transmission channel. Several different bonding protocols can be implemented for BRI-ISDN services, a common one being Multilink PPP (MPPP) for asynchronous bonding.
NOTE
Bonding must be supported by the ISDN devices at both ends of the ISDN link. Typically, one of the B channels is designated as responsible for initiating the bonding process.
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Many ISDN terminal adapters can override bonding when the user wants to place a regular Plain Old Telephone Service (POTS) phone call. For example, you might be using ISDN for high-speed Internet access with both B channels bonded to give you 128-Kbps (or 14-kilobytes/second) access. Then, if you suddenly pick up a phone connected to the terminal adapter’s POTS jack, bonding stops and the second B channel is freed up for the phone call. Once the call is complete, bonding will resume.
A term used to refer to the process of starting a computer, as in the phrase, “Please boot the computer.” The term “boot” also refers specifically to the series of steps by which a computer locates and loads the operating system once the power is turned on. This series of steps is usually referred to as the boot sequence, and it is dependent on both the type of operating system installed on the machine and the type of hardware platform (for example, x86 platform or Alpha platform).
The term “warm boot” refers to resetting the system or rebooting using Ctrl+Alt+Delete. The power to the system is not interrupted during a warm boot, but the boot process starts again from the beginning using the system BIOS.
The term “cold boot” refers to shutting down a computer and actually turning off the power source, and then turning it back on. Cold boots are sometimes necessary after installing or configuring some legacy hardware devices to ensure that the devices are properly initialized. For example, sometimes if you change the configuration parameters of an internal modem, you need to cold boot your system for these changes to take effect.
See also boot files, boot sequence
Files needed to boot an operating system on a computer. Each operating system has its own set of boot files needed to locate, load, and initialize the operating system during the boot sequence. For example, the MS-DOS and Microsoft Windows 3.x platforms use the hidden files io.sys and msdos.sys and the file command.com. Configuration information stored in the text files config.sys and autoexec.bat is also used during the process. On Windows 95 and Windows 98 platforms, the files used are io.sys, msdos.sys, and win.com, with the files config.sys and autoexec.bat used optionally to support legacy hardware.
The files needed to boot the Windows NT and Windows 2000 operating systems vary depending on whether the x86 platform or the Alpha platform is used. For example, for Windows NT on the x86 platform, the boot files include the following:
boot.ini
bootsect.dos
hal.dll
ntdetect.com
ntbootdd.sys
ntldr
ntoskrnl.exe
The boot sequence also uses various device drivers and the system hive.
See also boot sequence
A hidden, read-only text file on the root of the system partition of Microsoft Windows NT and Windows 2000 that is used to create the boot loader menu. For example, a typical boot.ini file for a default Windows NT installation might look like this:
[boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(1)\WINNT [operating systems] multi(0)disk(0)rdisk(0)partition(1)\WINNT="Windows NT Server Version 4.00" multi(0)disk(0)rdisk(0)partition(1)\WINNT="Windows NT Server Version 4.00 [VGA mode]" /basevideo /sos
A close correspondence can be seen between the appearance of the boot.ini file and the boot loader menu, which the ntldr program creates during the Windows NT boot sequence.
NOTE
You can safely modify some of the settings in this file using the System utility in Control Panel. If you need to edit the file directly, use the attrib command to first remove its read-only, system, and hidden attributes and then modify the file using a text editor such as Microsoft Notepad. Do this carefully, as an error in the boot.ini file can prevent the system from booting.
See also boot files
A menu that appears when you boot a computer with the Microsoft Windows NT operating system installed. The boot loader menu appears during the boot loader phase of Windows NT startup, and it is displayed by the Windows NT loader program called ntldr. The boot loader menu allows you to
Select the particular operating system you want to run on a dual-boot system
Boot Windows NT using optional boot-time switches for troubleshooting reasons
There are always two boot loader menu entries for each copy of the Windows NT operating system installed on a computer—for example, “Windows NT Server Version 4.0” and “Windows NT Server 4.0 [VGA mode]”.
Use the VGA mode option if you have changed your video display driver settings and cannot access the desktop after a normal boot. Once you have booted in VGA mode, reconfigure your video driver.
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The boot loader menu is created by the boot.ini file, which can be edited using a text editor such as Microsoft Notepad, but this should be done with care. A safer way of modifying boot.ini is to use the System utility in Control Panel.
See bootstrap protocol (BOOTP)
The partition of a disk on which Microsoft Windows NT or Windows 2000 installs core operating system files. These operating system files are stored in the %SystemRoot% and %SystemRoot%\system32 directories on the boot partition. The choice of boot partition is made during installation of Windows NT and cannot be changed afterward. An important consideration when installing Windows NT is designation of a boot partition that has sufficient free space to contain the operating system files together with all the optional and future components.
The boot partition can be the same as or different from the system partition, which is the partition containing the hardware-specific files for the particular hardware platform Windows NT is installed on (x86 platform or Alpha platform).
See also system partition
A hidden, read-only file on the root of the system partition of Microsoft Windows NT that is used during the boot sequence. The bootsect.dos file is included to support dual-boot installations where another operating system is installed with Windows NT. When the boot loader menu appears, the user selects the operating system he or she wants to boot. If a non–Windows NT operating system is selected, the ntldr program immediately loads bootsect.dos and turns control of the boot process over to it. Bootsect.dos contains the location of the partition boot sector that existed on the partition prior to the installation of Windows NT. Thus, bootsect.dos enables the system to locate and load the alternate operating system. Bootsect.dos is not loaded during a normal boot of the Windows NT operating system.
See also boot files
The series of steps that occurs when an operating system boots on a machine. Each operating system has its own particular boot sequence and uses its own specific set of boot files. Knowledge of the boot sequence for a particular operating system can aid in troubleshooting problems booting a machine on which that operating system is installed. For example, from messages displayed during the boot process, a technician can often determine whether a particular boot file is missing or corrupt.
The following table is a high-level illustration of the boot sequence for the Microsoft Windows NT operating system installed on an x86 platform. This boot sequence is divided into four phases, and different activities occur in each phase. For a successful boot of the system to occur, all four phases must be completed successfully.
The Four Phases of a Windows NT Boot Sequence
| Phase | Name | Description |
| 0 | Initial phase | Power-on self test (POST); locate and load ntldr |
| 1 | Boot loader phase | Black screen: hardware detection, boot loader menu, last known good option, load ntoskrnl.exe or ntkrnlmp.exe |
| 2 | Kernel phase | Blue screen: kernel initialization, create hardware hive and Clone control set, initialize devices, start services |
| 3 | Logon phase | Begin Logon dialog box |
See also boot files
A TCP/IP protocol and service that allows diskless workstations to obtain their IP address, other TCP/IP configuration information, and their boot image file from a bootstrap protocol (BOOTP) server. The network interface card (NIC) on these diskless workstations contains a programmable read-only memory (PROM) chip containing code necessary to initialize the client.
How It Works
When a BOOTP client is started, it has no IP address, so it broadcasts a message containing its MAC address onto the network. This message is called a “BOOTP request,” and it is picked up by the BOOTP server, which replies to the client with the following information that the client needs:
The client’s IP address, subnet mask, and default gateway address
The IP address and host name of the BOOTP server
The IP address of the server that has the boot image, which the client needs to load its operating system
When the client receives this information from the BOOTP server, it configures and initializes its TCP/IP protocol stack, and then connects to the server on which the boot image is shared. The client loads the boot image and uses this information to load and start its operating system.
The Dynamic Host Configuration Protocol (DHCP) was developed as an extension of BOOTP. BOOTP is defined in Request for Comments (RFC) 951 and 1084.
NOTE
The term “bootstrap protocol” (or “boot protocol”) comes from the idea of lifting yourself up by your own bootstraps—something that is obviously difficult to do. In other words, how does a client machine start up when it initially has neither an IP address nor an operating system? BOOTP makes this difficult task possible.
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Microsoft Windows NT supports DHCP but not BOOTP. Windows NT Service Pack 3 and later provides some support for BOOTP clients, as does Microsoft Windows 2000. See the readme.txt file for Service Pack 3 for more details.
In Microsoft Windows 2000, the volume that has the Windows 2000 operating system files. The boot volume can be the same as or different from the system volume, and it can be formatted in either NTFS or file allocation table (FAT).
A standard TCP/IP protocol based on the distance vector routing algorithm that enables groups of routers to share their routing information in an efficient manner. Border Gateway Protocol (BGP) version 4 is used to connect backbone routers on the Internet and is implemented by many Internet service providers (ISPs). BGP has largely superseded the earlier Exterior Gateway Protocol (EGP).
How It Works
BGP works by listening to traffic being routed and inferring information concerning the reachability of neighboring networks. BGP supports policy-based routing, which enables network traffic to be routed differently according to its cost, importance, or security needs. BGP divides an internetwork into groups of routers (called autonomous systems) that have trusted routes between them. This limits the size of the routing table in order to optimize reliability and performance on large internetworks such as the Internet.
The first update of a router’s BGP routing table includes all known routes on the network, while succeeding updates are only incremental. BGP also supports classless interdomain routing (CIDR). BGP is defined in Request for Comments (RFC) 1771 through 1774.
On the Web
•
Border Gateway Protocol (Cisco) : http://www.cisco.com/univercd/cc/td/doc /cisintwk/ito_doc/bgp.htm
•
Using BGP for Interdomain Routing (Cisco) : http://www.cisco.com/univercd/cc/td/doc/cisintwk/ics/icsbgp4.htm
•
BGP FAQ : http://info.connect.com.au/docs/routing/general/multi-faq.shtml
A bottleneck is a situation that occurs when network servers and components are unable to meet demand. The bottleneck is the particular network component or server subsystem that is causing the problem.
For example, if users on a Microsoft Windows NT or Windows 2000–based network are complaining that it takes too long to log on in the morning, the bottleneck and its potential resolution might be
Not enough domain controllers to handle logon requests (The solution: add more domain controllers)
The domain controller does not have enough memory to process large numbers of simultaneous logons (The solution: add more RAM)
Network bandwidth is saturated in the morning with directory replication traffic (The solution: reschedule directory replication or upgrade to 100-Mbps Ethernet)
The primary tool for analyzing and resolving network bottlenecks is the Windows NT administrative tool Performance Monitor (or the Performance snap-in tool for Windows 2000). To learn about how to identify and correct bottlenecks using Performance Monitor, consider taking the Microsoft Official Curriculum (MOC) course MS 689, “Supporting Microsoft Windows NT Server 4.0—Enterprise Technologies.”
An effect that happens to signals on a bus topology network when the ends of the bus are improperly terminated or unterminated. A signal that is placed on a bus that is unterminated will continue to reflect from the end of the bus until that signal is attenuated by the impedance of the cable. Another situation that can cause signals to bounce is a break in the cable, which essentially creates two unterminated ends for the two segments. The effect of signal bounce on baseband networks such as Ethernet is serious, since the transceivers on the network interface cards (NICs) attached to the bus interpret the problem as a collision and stop transmitting. This collision occurs because the signal is colliding with its own reflection. Once the proper termination is applied to the bus, network communication can resume.
See bits per second (bps)
A troubleshooting tool used to determine the wiring of an RS-232 interface on a networking device or computer. A breakout box can be inserted between two RS-232 devices to determine which wires are active. Breakout boxes are useful in troubleshooting RS-232 connection problems resulting from a manufacturer’s device not using standard pinning.
Breakout boxes are specific examples of a more general category of network testing equipment called “status monitors.” Status monitors are available for testing a variety of serial interfaces, including RS-232, RS-449, V.35, and X.21. They generally come with a variety of connectors and are quick and easy to use for isolating problems with serial transmission connections in networking, telecommunications, and industrial settings.
A networking component used either to extend or to segment networks. Bridges work at the OSI data-link layer. They can be used both to join dissimilar media such as unshielded twisted-pair (UTP) cabling and fiber-optic cabling, and to join different network architectures such as Token Ring and Ethernet. Bridges regenerate signals but do not perform any protocol conversion, so the same networking protocol (such as TCP/IP) must be running on both network segments connected to the bridge. Bridges can also support Simple Network Management Protocol (SNMP), and they can have other diagnostic features.
Graphic B-9. The three basic types of bridge.
Bridges come in three basic types:
Local bridges: Directly connect local area networks (LANs)
Remote bridges: Can be used to create a wide area network (WAN) link between LANs
Wireless bridges: Can be used to join LANs or connect remote stations to LANs
How It Works
Bridges operate by sensing the source MAC addresses of the transmitting nodes on the network and automatically building an internal routing table. This table is used to determine which connected segment to route packets to, and it provides the filtering capability that bridges are known for. If the bridge knows which segment a packet is intended for, it forwards the packet directly to that segment. If the bridge doesn’t recognize the packet’s destination address, it forwards the packet to all connected segments except the one it originated on. And if the destination address is in the same segment as the source address, the bridge drops the packet. Bridges also forward broadcast packets to all segments except the originating one.
TIP
Use bridges to reduce network congestion and improve performance by segmenting busy Ethernet networks into smaller collision domains. Bridges can also be used to connect segments more efficiently than repeaters and to join dissimilar networks such as Ethernet and token ring. Remote bridges can be used to create WAN links.
A poorly placed bridge can actually worsen network performance. For example, if you use a bridge to divide users who belong to the same department and frequently communicate with each other over the network, this might actually slow down communication among users by creating a bottleneck. It is better to use bridges to join separate departmental LANs together on which intradepartmental traffic is greater than interdepartmental traffic.
When using bridges to connect networks, make sure that only one path leads to any destination node on the network; otherwise, frames could become locked in loops and circle the network endlessly, causing a network storm.
See also remote bridge, wireless networking
A computer running Microsoft Exchange Server that acts as an endpoint of a connector joining two Exchange sites. A bridgehead server is responsible for routing messages through that connector. There are two different types of bridgehead servers in an Exchange organization, although a single server often functions in both roles:
Messaging bridgehead servers: Used to route recipient messages from one site to another
Directory replication bridgehead servers: Used to route directory replication messages from one site to another
TIP
Pass-through traffic consists of messages that originate in one site and are destined for another site, but in order to reach their destination site, must pass through one or more additional sites. You can reduce the effects of pass-through traffic by using dedicated messaging bridgehead servers—that is, bridgehead servers that have no mailboxes or public folders homed on them. You can also have traffic enter a site by one server and leave it by another. If you have a large number of sites, you might want to configure a given site to use a different bridgehead server to connect to each remote site for load balancing of messaging traffic. Also, you can schedule directory replication traffic to occur at slow periods during each day.
A feature of Microsoft Windows 95, Windows 98, Windows NT 4.0, and Windows 2000 that is typically used to enable mobile users to copy and synchronize files between a desktop and a portable computer so that they can easily copy and work on files at home or on the road without creating version conflicts.
Using Briefcase is simple. Create a Briefcase icon by right-clicking the desktop, choosing New from the context menu, and then choosing Briefcase. Then drag the files you want into the Briefcase folder and copy it to your laptop computer. After you modify the copies of the files in your laptop’s Briefcase folder, connect your laptop to your desktop computer and the newer versions will be copied over the old. If the original files on the desktop computer were modified while you were away, you will be prompted to specify which modified version is the correct one for each file. (Briefcase cannot merge changes in files.)
See Basic Rate Interface ISDN (BRI-ISDN)
The broadband transmission counterpart of Integrated Services Digital Network (ISDN). Broadband ISDN (B-ISDN) encompasses a set of International Telecommunication Union (ITU) standards and services designed to provide an integrated digital network for audio, video, and data transmission. Instead of using the copper media used in ordinary ISDN, broadband ISDN uses fiber-optic and radio media. Broadband ISDN is designed to use the cell-switching transport technology of Asynchronous Transfer Mode (ATM) together with the underlying physical transport mechanisms of Synchronous Optical Network (SONET). Broadband ISDN standards and technologies are an emerging option for high-speed networking that promises the capabilities of high-speed digital connectivity for homes and businesses.
A signaling technology that sends signals simultaneously over a range of different frequencies as electromagnetic waves. The bandwidth of a broadband system can usually carry multiple, simultaneous data signals. These signals are unidirectional—traveling in only one direction at a time—so a broadband system can generally either transmit or receive but cannot do both simultaneously. Broadband signals can be regenerated using amplifiers in order to travel longer distances before becoming attenuated.
How It Works
Broadband transmissions are divided into multiple bands or channels by multiplexers using a multiplexing scheme such as frequency-division multiplexing (FDM). Each channel has a carrier frequency that is modulated to carry the signal from a given source. At the receiving station, multiplexers separate the various signals. Guard bands are used to prevent interference among channels.
Broadband transmission is typically used for environments in which video, audio, and data need to be transmitted simultaneously. Cable television systems are based on broadband transmission technologies. Other examples of broadband services include T-carrier services, Asynchronous Transfer Mode (ATM), and variants of Digital Subscriber Line (DSL).
See also baseband transmission
A communication method for sending information to all components on a network of computers simultaneously.
How It Works
Broadcasts take place when broadcast packets (or broadcast frames) are sent over the network. These packets contain a special address that instructs every station on the network to accept and process the packet. Broadcasts are typically used for announcements by network services, for resolving names into addresses, and for other similar functions. Broadcasts are usually not an efficient use of network bandwidth, since only one or a few network stations might actually be interested in the information being broadcast. For this reason, directed packets are used for most network communication, which involves targeting a packet directly for the intended station. (All other stations ignore the directed packet.) An alternative is multicasting, which involves a form of limited broadcast to a select group of hosts.
Certain network conditions, such as certain types of device failure, can cause broadcast storms that can bring down a network.
See also broadcast frame, broadcast packet
In Ethernet networks, a frame that has a hexadecimal MAC address of FF-FF-FF-FF-FF-FF. This hexadecimal address is equivalent to 48 binary “ones.” The meaning of this address in Ethernet is simply that this frame is intended to be received and processed by every node on the network of computers. Broadcast frames are generated when certain network services need to make announcements to other hosts on the network. Too many broadcast frames on a network can degrade communication between nodes on the network.
NOTE
Most routers are not configured to forward broadcast frames to other subnets in an internetwork; therefore, broadcast frames used as announcements are limited in scope to the local subnet on which the broadcasting host is located.
See also broadcast
In TCP/IP, an Internet Protocol (IP) packet with the IP address 255.255.255.255. In binary notation, this represents a series of 32 binary “ones.” A broadcast packet is sent over the network of computers and picked up by all hosts on the local subnet. Broadcast packets can also be forwarded to other subnets if routers are configured to forward IP broadcasts, though this is not usually the case.
See also broadcast, directed packet
A network condition in which so many broadcasts are occurring (for example, for address verification purposes) that normal communication is disrupted.
How It Works
Broadcast storms commonly occur on Ethernet networks where baseband transmission technologies allow only one station to transmit at a time. The presence of broadcast storms often indicates that a networking component is malfunctioning and is continually sending out broadcast messages. A typical situation might be a failed transceiver on a network interface card (NIC) that is continually sending out a stream of binary “ones.” During a broadcast storm, the wire is continually busy and no other station is able to transmit information over the network—so broadcast storms essentially bring down the network. Since routers often are not configured to forward broadcast frames between subnets, broadcast storms usually are confined to a single subnet. Broadcast storms might also indicate that the bandwidth of your network is nearly saturated and needs to be upgraded.
See also broadcast
Any network device having the capabilities of both a bridge and a router. Usually, a brouter will act as a router for one protocol (for example, TCP/IP) and a bridge for all other protocols (for example, IPX/SPX). Brouters are not common in networks. Network services often send their announcements over every protocol on the network, which generates additional traffic and makes it generally disadvantageous to run more than one protocol on a single network. The solution adopted by most implementers today is to use a single protocol for all network communication on the main portion of the network, with gateways connecting to segments running other protocols. The protocol of choice for most internetworking today is TCP/IP.
The list of available shared network resources collected and distributed by the Computer Browser service on a Microsoft Windows NT or Windows 2000 network. The browse list contains all available domains and servers on the network. This list is distributed to clients who try to connect to shared resources on the network so that they can locate and connect to these resources. Essentially, when you are using Network Neighborhood, you are looking at the browse list for your network. The browse list is maintained by the master browser computer, but clients that need it obtain it from backup browsers on the network.
NOTE
If a server or domain is not heard from by the master browser after three announcement periods (amounting to approximately 45 minutes), the server or domain is removed from the browse list.
See also Computer Browser service
In Microsoft Windows NT or Windows 2000, the process of selecting a new master browser from a network’s potential browsers. If a client machine is not able to locate a master browser on the network in Windows NT or Windows 2000, it initiates an election to select a new master browser. Elections are a way of ensuring that a master browser is always available on the network, as the absence of a master browser means that clients will be unable to locate and access network resources such as shared files and folders.
How It Works
If a client machine cannot locate a master browser on the network, it broadcasts an election datagram. When a machine that is a potential browser receives this datagram, it examines the election criteria in the datagram. If its election criteria are better than those of the datagram’s sender, the potential browser broadcasts its own election datagram and an election is declared to be in progress. The election criteria for becoming a master browser are a combination of factors, including the machine’s operating system, version, role, and so on. Eventually, one potential browser wins out (has superior election criteria) over other machines on the network, and the election ends.
NOTE
Elections also occur when domain controllers are restarted.
See also Computer Browser service
On a Microsoft Windows NT or Windows 2000 network, the process of locating network resources using Windows Explorer, Network Neighborhood, or another utility. Browsing is made possible by the Computer Browser service, which keeps track of all shared resources on a Windows NT network and communicates this information to clients when they need to access a resource. The Computer Browser services are at the core of the ability to locate shared file and printer resources on a network.
In relationship to the Internet, the term “browsing” refers to the process of using a Web browser such as Microsoft Internet Explorer to view and download Web pages from the Internet. The origin of the term probably stems from the idea of reading magazines, in which you pick up one magazine and skim through its contents, then go to another magazine, and so on. On the Internet, it is even easier. You don’t have to “pick up” anything; you simply keep clicking the links.
See backup site controller (BSC)
Stands for Berkeley Software Distribution UNIX, a version of UNIX that originated many common UNIX features such as the vi editor, C shell, and TCP/IP networking. BSD UNIX was developed in the 1970s at the University of California at Berkeley, which licensed the UNIX operating system from AT&T and then made a number of modifications and enhancements. BSD UNIX is one of the most popular versions of UNIX in use today, the other being UNIX System V and its variants. BSD UNIX formed the basis of the SunOS from Sun Microsystems. Sun later combined features of both BSD and System V into their popular Solaris operating system. Another variant of BSD is the FreeBSD operating system.
In Microsoft Windows NT and Windows 2000, a type of user account that is created during installation. All computers running Windows NT or Windows 2000 have two built-in user accounts:
The Administrator account: Used to provide administrative access to all features of the operating system
The Guest account: Intended to provide occasional users with access to network resources
Depending on whether the computer is a domain controller, a member server, or a workstation, built-in accounts will be either local user accounts or global user accounts. A built-in account on a domain controller is a global user account that exists everywhere within the domain. Users can log on to any machine in the domain using such an account, which provides administrators with the capability of administering a Windows NT–based or Windows 2000–based network from anywhere on the network. On a member server or workstation, the Administrator and Guest accounts are local user accounts and exist only on those machines.
TIP
Rename the Administrator built-in user account to make it more secure.
See also built-in group
Global groups in Microsoft Windows NT that are created during installation to organize common groups of users for administrative purposes. These built-in global groups are created within the Security Accounts Manager (SAM) database of the primary domain controller (PDC). Three built-in global groups exist:
Domain Admins: Initially, this group contains only the Administrator account that was created during setup. Only people with administrative responsibilities should be assigned to this group.
Domain Guests: This group contains the Guest account and is designed for organizing temporary users of network resources and granting them access.
Domain Users: When a new user account is created, it is automatically added to this group. The function of this group is to collect all ordinary users for the purpose of assigning them permissions to resources on the network.
NOTE
Windows 2000 includes a fourth type of built-in global group called Enterprise Admins, which contains users who are assigned administrative rights over the entire network. The Enterprise Admins global group should be added to the Administrators domain local group in each domain of your network. By default, the Administrator account is a member of the Enterprise Admins group.
See also built-in local group
In Microsoft Windows NT and Windows 2000, a type of group created during installation to simplify the delegation and assignment of common administrative tasks. Built-in groups have preassigned sets of user rights, and some also have preassigned members.
Windows NT contains three kinds of built-in groups:
Built-in local groups: These are used to assign predefined sets of rights and permissions to users and groups of users, and they exist on all computers running Windows NT.
Built-in global groups: These groups are used to automatically organize users into common groups for administrative purposes, and they exist only on Windows NT domain controllers.
System groups: These are used by the operating system to automatically group users for system purposes, and they exist on all computers running Windows NT.
In Windows 2000, the built-in groups are similar in function, except that a fourth type, called a domain local group, is also available. Built-in groups in Windows 2000 are also administered differently using different tools. Also, system groups in Windows 2000 are referred to as built-in identities.
NOTE
You cannot rename or delete a built-in group, and you cannot change the membership of a system group.
See also built-in global group, built-in local group
A Microsoft Windows 2000 term used to refer to what were known in Windows NT as system groups. Built-in identities can represent different subsets of users in different situations, and they do not have a specific membership that can be modified by administrators. However, you can assign built-in identities rights and permissions for accessing resources or performing system tasks. Examples of built-in identities include
Everyone: Represents all users who can be or are on the network, whether from trusted or distrusted domains.
Network: Represents all users who can access or are accessing network resources over the network. It does not include users logged on locally to a machine and accessing those resources locally.
Interactive: Represents all users who can be or are currently logged on locally to a computer to access local resources on it. It does not include users who can access or are accessing network resources over the network.
A Microsoft Windows NT local group created during installation that has preassigned rights and permissions. Built-in local groups are used to simplify the administrative task of assigning users and groups rights to perform system tasks and permissions to access network resources. There are nine different built-in local groups on computers running Windows NT:
Users: Contains the Domain Users global group and is used to assign rights and permissions to all ordinary users.
Administrators: Contains the Domain Admins global group and the Administrator account created during setup.
Guests: Contains the Domain Guests global group.
Power Users: Members have the right to share folders and printers.
Replicator: This group is used exclusively by the Directory Replicator Service.
Backup Operators: Members have the right to back up and restore servers.
Account Operators: Members have the right to administer accounts.
Server Operators: Members have the right to administer servers.
Print Operators: Members have the right to administer printers.
The following table shows which of these groups exist within the domain directory database on Windows NT domain controllers and which exist within the local directory database on Windows NT member servers and workstations:
Built-In Local Groups of Windows NT
| Built-In Local Group | Windows NT Domain Controller | Windows NT Member Server | Windows NT Workstation |
| Users | Y | Y | Y |
| Administrators | Y | Y | Y |
| Guests | Y | Y | Y |
| Power Users | N | Y | Y |
| Replicator | Y | Y | Y |
| Backup Operators | Y | Y | Y |
| Account Operators | Y | N | N |
| Server Operators | Y | N | N |
| Print Operators | Y | N | N |
NOTE
On Windows 2000 networks, there are only six built-in local groups, and these exist only on member servers or workstations. The six built-in local groups for Windows 2000 are Users, Administrators, Guests, Power Users, Replicator, and Backup Operators.
Windows 2000 also has built-in groups called “built-in domain local groups.” These groups are designed to provide users with permissions and rights on domain controllers and Active Directory. The seven built-in domain local groups in Windows 2000 are Users, Administrators, Guests, Backup Operators, Account Operators, Server Operators, and Print Operators.
See also built-in global group
See built-in account
A condition in which network activity rises suddenly for a short period of time. A burst is a transient elevation in network activity, and a network on which a lot of bursts occur is said to be “bursty.” Bursty networks have different bandwidth requirements than networks on which the traffic is steady, and they need to be designed accordingly. For example, a network on which large video files are frequently transmitted tends to be bursty in its traffic flow. A good first step in accommodating bursty conditions is to use Ethernet switches instead of hubs for concentrating your network connections.
TIP
Bursts can be indicative of a sudden increase in demand for network resources, or they can indicate hardware or software problems. Some networking components are capable of briefly sending data at speeds greater than normal transmission speeds; this is referred to as “operating in burst mode.”
Generally, a cable or wires connecting devices in a linear fashion. Examples include
System bus on a motherboard, providing a path along which data can flow
Small Computer System Interface (SCSI) bus used for chaining SCSI devices together
Thinnet or thicknet cabling connecting computers, hubs, or other networking components in a bus topology
See also terminator
A term used in writing applications for Microsoft Transaction Server (MTS) using reusable COM+ components that refers to a combination of logon verifications, policies, database lookups, validation edits, and other processes that constitute how business is done in the enterprise. The business logic of an application specifies how the programming logic of the component reflects the actual way the enterprise does business. Business logic enables consistent and logical processing of business data.
A representation of a real-world component of the enterprise’s business is called a “business object.” Examples of business objects include customers, orders, products, invoices, and anything else that can be encapsulated in an application’s business logic and manipulated by its users.
A networking topology that connects networking components along a single cable or that uses a series of cable segments that are connected linearly. A network that uses a bus topology is referred to as a “bus network.” Bus networks were the original form of Ethernet networks, using the 10Base5 cabling standard. Bus topology is used for
Small workgroup local area networks (LANs) whose computers are connected using a thinnet cable
Trunk cables connecting hubs or switches of departmental LANs to form a larger LAN
Backboning, by joining switches and routers to form campus-wide networks
Graphic B-10. Bus topology.
Bus topology is the cheapest way of connecting computers to form a workgroup or departmental LAN, but it has the disadvantage that a single loose connection or cable break can bring down the entire LAN.
NOTE
A hub or concentrator on an Ethernet network is really a collapsed bus topology. Physically, the network appears to be wired in a star topology, but internally the hub contains a collapsed bus, creating a configuration called a star-wired bus. However, in this case, a failure in one of the cables does not affect the remaining network.
TIP
Communication problems on bus networks might indicate that the bus ends are improperly terminated. A break in the cable will produce a similar result, since the ends of the break are not terminated. Use a cable tester to determine the nature and location of the problem.
See also mesh topology, ring topology, star topology
