Networking Concepts and Definitions PDF

#DOM A predefined keyword that is prefixed with a #. The #DOM is an LMHOSTS keyword and facilitates domain activity such as logon validation over a router or account sychronization and browsing. #PRE An LMHOSTS file keyword that defines which entries should be initially preloaded as permanent e...

#DOM A predefined keyword that is prefixed with a #. The #DOM is an LMHOSTS keyword and facilitates domain activity such as logon validation over a router or account sychronization and browsing. #PRE An LMHOSTS file keyword that defines which entries should be initially preloaded as permanent entries in the name cache. The preloaded entries can reduce network broadcasts, because the names will be resolved from cache rather than making a broadcast. Any entries with a #PRE tag get loaded automatically during initialization. 16-bit Application An application that has been written using the 16 bit length for communicating data. 32-bit Application An application that has been written using the 32 bit length for communicating data. 64-bit Application An application that has been written using the 64 bit length for communicating data. 802.1x 802.1x is a networking protocol that defines how to support EAP (Extensible Authentication Protocol) over a wired or wireless LAN. A.ADM file Template files that Internet Explorer and its Profile Manager use to create system policy files that control the IE options that are available to network users. Accepted domains Accepted domains identify the domains for which the organization is solely responsible and the SMTP domains from which the server will accept messages. There are three types of accepted domains in Exchange 2007: Authoritative is the domain over which the Exchange server has sole responsibility. In a typical environment, the organization will have an e-mail domain of "company.com" which is hosted by the company's e-mail server. If another e-mail system or domain exists in the environment, internal and external relays are employed. An internal relay is an e-mail domain that is hosted by another Active Directory Forest within the Exchange organization. This system uses different e-mail addresses, but all incoming mail goes through the Exchange organization. An external relay accepts e-mail for an external organization and then delivers it to an external entity such as the Internet via the Edge Transport server. Access Control List (ACL) A list that contains information on allowed and denied access to folders and files. Access token A grouping of information used to control a user's access to network resources. After the logon process, the access token is used to control access to all secured objects. An access token includes the user's SID (security ID), ID of users' group memberships, and rights assigned to the user. The access token is generated during the logon process and is not updated while the user is logged on. Account lockout A mechanism to lock out accounts after multiple failed logon attempts. This reduces the chance of an unauthorized person gaining access to the network. Account Operator A specific user who has been designated an Account Operator can create, delete, and modify user accounts, global and local groups, and set account policies. Account policy Determines the characteristics of passwords for user accounts. The policy sets requirements for password age, length, and uniqueness. ACL (Access Control List) A list that contains information on allowed and denied access to folders and files. Active Desktop A feature of Microsoft Internet Explorer that lets you display content from Web pages on the computer desktop, using Dynamic HTML, Webcasting, and active channels. Active Directory The new Windows 2000 directory service. It stores information about all the network resources such as user accounts, computers, printers, servers, and so on. Active Directory makes it easy for administrators to manage the network resources, and makes it easy for users to locate and use the resources. Active Directory Sites and Services Snap-In A Microsoft Management Console (MMC) snap-in that lets you create and work with the configuration partition of an Active Directory database. Active Server Pages (ASP) Microsoft's answer to the slower and more limited performance of CGI scripts written in Perl. They combine HTML pages, scripts, programming objects, and ActiveX components to create dynamic Web pages. ActiveX A set of programming tools based on the Component Object Model (COM), which provides the low-level services that allow programming objects to communicate with each other. ActiveX is used for Internet applications that need to be optimized for speed and size. AD (Advertised Distance) The Advertised Distance (AD) is the cost to the destination network as reported by the neighbor router. The AD is also called the reported distance (RD). Ad hoc A wireless networking architecture topology that does the following: Works in peer-to-peer mode without a WAP (the wireless NICs in each host communicate directly with one another) Uses a physical mesh topology Cheap and easy to set up but cannot handle more than four hosts Requires special modifications to reach wired networks Adapter card The physical interface between the computer and the network cable. An adapter card communicates with the computer's hardware, firmware, and software to allow the computer to communicate with the local area network. Also called a network adapter card, network card, or NIC. Adapter teaming Adapter teaming is the use of two or more adapter cards in a system to eliminate a network adapter as a single point of failure. In adapter teaming: Up to four adapter teams can be supported with two to four adapters in each team. Each adapter is connected to the same network segment via a network switch or hub. Address family An address family is a group of network protocols whose network addresses share a common format. Address Resolution Protocol (ARP) A protocol that maps an IP address to the Media Access Control (MAC) address of a computer on a network. Adjacency An adjacency is the connection that is established when neighboring routers transfer packets. ADMD (Administration Management Domain) An ADMD is a public operating agency that controls an X.400 management domain. These domains are the backbone for transferring electronic messages. ADMDs handle messages sent between PRMDs. Administration Management Domain (ADMD) An ADMD is a public operating agency that controls an X.400 management domain. These domains are the backbone for transferring electronic messages. ADMDs handle messages sent between PRMDs. Administrative distance The administrative distance is a metric used to show how trustworthy a router deems information from a specific protocol. Administrative distances are as follows: 0= Connected interface 0= Static route out of an interface 1= Static route to a next-hop address 5= EIGRP summary route 20= External BGP 90= Internal EIGRP 100= IGRP 110= OSPF 115= IS-IS 120= RIPv1 and RIPv2 140= EGP 160= ODR 170= External EIGRP 200= Internal EIGRP 255= Unknown Protocols with lower administrative distances are considered more trustworthy. Administrative share Windows 2000 provides share names that are used for administration. These names are C$, D$, E$, etc. and Admin$.The $ hides the shared folder from a user who browses the computer. Administrative shares are used to remotely connect to a computer to perform administrative tasks. Administrative template A group of registry settings stored in a file (Registry.pol). Adminstrative templates can be distributed using Active Directory-based Group Policy Objects (GPOs). Administrator A user who is granted rights to create, delete, or modify user accounts. They also have rights to create user policies, move folders, add and remove hardware from the computer, and access the file system. Administrators A built-in group in Windows 2000. Members of the Administrators group have full administrative capabilities (see Administrator). ADSI Edit A graphical Windows 2000 support tool that lets you view, edit, and create objects and attributes in the Active Directory database. Advanced Research Projects Agency (ARPA) The first group to conduct packet-switching network experiments. Advanced Research Projects Agency Network (ARPANET) In the late 1960s and early 1970s, the United States Department of Defense sponsored this project to create a network between government and research institutions. The project became the foundation for what is now known as the Internet. Advanced RISC Computing (ARC) naming convention The syntax used for recovering data in a secondary partition. ARC paths specify the hardware adapter and disk controller, the numbers of the hardware adapter, the SCSI bus, the disk, and the partition. Advertised Distance (AD) The Advertised Distance (AD) is the cost to the destination network as reported by the neighbor router. The AD is also called the reported distance (RD). AH (Authentication Header) Authentication Header (AH) is one of two services comprising IPSec, Encapsulating Security Payload (ESP) being the other. AH is used primarily for authenticating the two communication partners of an IPSec link. The AH provides message integrity through authentication, verifying that data are received unaltered from the trusted destination. AH provides no privacy however, and is often combined with ESP to achieve integrity and confidentiality. Alert An action, defined by an administrator, that takes place in response to an administrator-specified event. The action can be the execution of a job, or e-mailing/paging a particular operator. American National Standards Institute (ANSI) A standards body that provides computing standards. It is a voluntary organization comprised of corporate, government, and other members that coordinates standards-related activities, approves U.S. national standards, and develops positions for the United States in international standards organizations. ANSI helps develop international and U.S. standards relating to, among other things, communications and networking. ANSI is a member of the IEC and the ISO. American Wire Gauge (AWG) A U.S. standard set of wire sizes that apply to copper wires, including household electrical wiring and telephone lines. The higher the number, the thinner the wire. ANDing process The internal process used by TCP/IP to determine whether a packet is destined for a host on a local or remote network. TCP/IP performs the function of ANDing the host's IP address with its subnet mask. When a packet is sent on the network, the destination IP address is ANDed with the same subnet mask. Anonymous authentication An authentication method that does not require the user to enter a username and password to gain access to resources such as Web sites. Some anonymous access methods (like FTP) require an e-mail address as a username, but this is not a secure solution because a fake e-mail address can be used. ANSI (American National Standards Institute) A standards body that provides computing standards. It is a voluntary organization comprised of corporate, government, and other members that coordinates standards-related activities, approves U.S. national standards, and develops positions for the United States in international standards organizations. ANSI helps develop international and U.S. standards relating to, among other things, communications and networking. ANSI is a member of the IEC and the ISO. Answer file A script file that you use to automate Windows installations by supplying answers to questions that you would normally have to answer yourself. You can modify the sample Unattend.txt file or use Setup Manager to create a new answer file. API (Application Programming Interface) The API can be provided by any vendor to provide functionality to an application or operating system. Each vendor publishes its API's so that developers can code to that application's APIs. APIPA (Automatic Private IP Addressing) APIPA is a Microsoft implementation of automatic IP address assignment without a DHCP server. Using APIPA, hosts assign themselves an IP address on the 169.254.0.0 network (mask of 255.255.0.0). With APIPA: The host is configured to obtain IP information from a DHCP server (this is the default configuration). If a DHCP server can't be contacted, the host uses APIPA to assign itself an IP address. The host only configures the IP address and mask. It does not assign itself the default gateway and DNS server addresses. For this reason, APIPA can only be used on a single subnet. Apple MacOS The proprietary Macintosh operating system used by Apple computers. Applet A small application built into another application or an operating system. The programs in the Windows Control Panel are applets. Also called programs in Microsoft documentation. AppleTalk The set of network protocols native to Apple computers. Application A software program that performs a specific function for the user or another program. For example, word processors, database programs, spreadsheets, and graphics packages are applications. Application files Files necessary for an application to run, such as.EXE,.DLL, and other files. Application Layer (OSI model) Layer 7 of the OSI reference model. This layer provides services to application processes (such as electronic mail, file transfer, and terminal emulation) that are outside of the OSI model. The application layer identifies and establishes the availability of intended communication partners (and the resources required to connect with them), synchronizes cooperating applications, and establishes agreement on procedures for error recovery and control of data integrity. Corresponds roughly with the transaction services layer in the SNA model. See also data link layer, network layer, physical layer, presentation layer, session layer, and transport layer. Application log An Event Viewer file containing application events such as file errors. Application developers determine the events that their applications write to the application log. Application Programming Interface (API) The API can be provided by any vendor to provide functionality to an application or operating system. Each vendor publishes its API's so that developers can code to that application's APIs. Application Server Application servers run certain software applications that can be accessed by users. ARC (Advanced RISC Computing) naming convention The syntax used for recovering data in a secondary partition. ARC paths specify the hardware adapter and disk controller, the numbers of the hardware adapter, the SCSI bus, the disk, and the partition. Archive Bit An archive bit is a file attribute that indicates whether a file was backed up since it was modified. ARIN A Windows Socket specification using Visual Basic. ARP (Address Resolution Protocol) A protocol that maps an IP address to the Media Access Control (MAC) address of a computer on a network. ARP cache A portion of memory that is used to store a hardware address and IP address. The ARP cache is always checked for an IP address/hardware address mapping before an ARP request broadcast is initiated. ARPA (Advanced Research Projects Agency) The first group to conduct packet-switching network experiments. ARPANET (Advanced Research Projects Agency Network) In the late 1960s and early 1970s, the United States Department of Defense sponsored this project to create a network between government and research institutions. The project became the foundation for what is now known as the Internet. AS (Autonomous System) An Autonomous System (AS) is a set of routers under a common administration and with common routing policies. Each Autonomous System (AS) in BGP appears to other autonomous systems to have a single coherent interior routing plan. AS path The AS path (type code 2) is a well-known mandatory BGP attribute that lists the different autonomous systems to reach a network. ASBR (Autonomous System Boundary Router) An Autonomous System Boundary Router (ASBR) is a router that has an interface to an external autonomous system (e.g. RIP or EIGRP). ASBRs can import and export non-OSPF network information to and from the OSPF network. ASP (Active Server Pages) Microsoft's answer to the slower and more limited performance of CGI scripts written in Perl. They combine HTML pages, scripts, programming objects, and ActiveX components to create dynamic Web pages. Attenuation The loss of signal strength over distance. Attribute version number A counter that identifies how many times the value for an Active Directory attribute has changed. During replication, attribute values with higher version numbers override values of the same attribute with lower version numbers. Audit log A file containing information about events you have chosen to monitor, such as logging on and logging off, accessing files and objects, and system shutdowns. You may want to save auditing logs to help you track trends. Tracking trends helps you plan for growth and detect unauthorized use of resources. For more accurate trend information, it is better to view logs that are kept over a few months. Authentication The process of supplying a valid user name and password in order to access resources on a network or computer. Authentication Header (AH) Authentication Header (AH) is one of two services comprising IPSec, Encapsulating Security Payload (ESP) being the other. AH is used primarily for authenticating the two communication partners of an IPSec link. The AH provides message integrity through authentication, verifying that data are received unaltered from the trusted destination. AH provides no privacy however, and is often combined with ESP to achieve integrity and confidentiality. Authoritative domain A domain is considered authoritative if your organization hosts mailboxes for recipients within the domain. Authoritative restore A restoration method which uses the Backup utility to return Active Directory database to the state it was in before the backup, then uses NTDSUTIL to mark an object as the most current. Most current objects will not be overwritten with the data from the server's replication partners during Windows 2000 replication. Use the authoritative restore when an object is deleted after the last backup. Restore the database with the last backup file, then update all the data modified after the last backup, except the one you marked with NTDSUTIL. Authoritative Server An authoritative server is a DNS server that has a full, complete copy of all the records for a particular domain. Autodiscover service The Autodiscover service in Exchange 2007 is designed to make it easier for users to set up their profiles in Outlook or for their Exchange Active Sync devices. The Autodiscover service automatically adds the following information to a user's profile: The server on which the user's mailbox resides The user's display name Separate connection settings for internal and external connectivity The URLs for Exchange features associated with the user Outlook Anywhere server settings Automatic Private IP Addressing (APIPA) APIPA is a Microsoft implementation of automatic IP address assignment without a DHCP server. Using APIPA, hosts assign themselves an IP address on the 169.254.0.0 network (mask of 255.255.0.0). With APIPA: The host is configured to obtain IP information from a DHCP server (this is the default configuration). If a DHCP server can't be contacted, the host uses APIPA to assign itself an IP address. The host only configures the IP address and mask. It does not assign itself the default gateway and DNS server addresses. For this reason, APIPA can only be used on a single subnet. Autonomous System (AS) An Autonomous System (AS) is a set of routers under a common administration and with common routing policies. Each Autonomous System (AS) in BGP appears to other autonomous systems to have a single coherent interior routing plan. Autonomous System Boundary Router (ASBR) An Autonomous System Boundary Router (ASBR) is a router that has an interface to an external autonomous system (e.g. RIP or EIGRP). ASBRs can import and export non-OSPF network information to and from the OSPF network. Autosummarization Autosummarization transpires when a router that uses a classful routing protocol sends and update about a subnet of a classful network across an interface belonging to a different classful network and assumes that the remote router will use the default subnet mask for that class of IP address. The following protocols use autosummarization: RIP EIGRP BGP AWG (American Wire Gauge) A U.S. standard set of wire sizes that apply to copper wires, including household electrical wiring and telephone lines. The higher the number, the thinner the wire. B Back end The server where database operations occur. The back end fulfills client requests by receiving structured requests from the client, processing the requests, and returning the results. It is usually more powerful than the client. Backbone area A backbone area acts as a hub for inter-area transit traffic and the distribution of routing information between areas. All OSPF networks have at least one backbone area, also known as an area 0. Backbone router A backbone router is located in the perimeter of the backbone area. Backbone routers: Maintain OSPF routing information using the same procedures and algorithms as internal routers. Have at least one interface that is connected to area 0. Backup Designated Router (BDR) On each subnet, a single OSPF router is identified as the Backup Designated Router (BDR). The BDR becomes the Designated Router (DR) if the DR becomes unavailable. Backup Domain Controller (BDC) A server containing a replicated copy of the domain database. Each Windows NT domain will have one PDC (Primary Domain Controller) with zero or more BDCs (backup domain controllers). Backup log A text file that records backup operations. The log is helpful when restoring data. You can print it or read it in a text editor. Backup marker Windows Backup can set a backup marker, also known as the archive attribute, indicating that the file has been backed up. Backup Operators A group that has permission to perform backups on a system. This group should have only sufficient rights to perform a backup. They typically use the Windows backup software. Backup set A term used to describe a group of files or folders on a single volume from a single backup operation. A group of tapes is called a family set. Baseband Baseband signalling allows one signal at a time on the network medium (cabling). Baseline A server baseline is a snapshot of the performance statistics of your server that is used as a logical basis for future comparison. Server baselines enable you to effectively monitor the performance of your system to determine when changes negatively impact performance or when systems need upgrading or replacing. Baselining Documenting a network's average performance statistics over time. Basic authentication An authentication method that requires the user to enter a valid username and password for a Windows user account. This information passes between the server and client in clear text. Basic disk A physical disk containing primary partitions, extended partitions, or logical drives. Using Windows NT 4.0 or earlier, you can create RAID-5 volumes for basic disks; they can also be spanned, mirrored, or part of a stripe set. MS-DOS can access basic disks. Compare dynamic disk. Basic multicast Basic multicast supports multicast applications within an enterprise campus. It is an interactive, intra-domain form of multicast that provides integrity within a network when combined with a reliable multicast transport such as PGM. Batch file A set of commands used to perform a specific operation on a computer. Baud rate The number of bits per second that are physically signaled over a communication medium. The term "baud" originally referred to the number of dots per second that could be signaled using Morse code over particular telegraph systems. The unit of measure was named after J.M.E. Baudot, the developer of the first printer for telegraph systems. BDC (Backup Domain Controller) A server containing a replicated copy of the domain database. Each Windows NT domain will have one PDC (Primary Domain Controller) with zero or more BDCs (backup domain controllers). BDR (Backup Designated Router) On each subnet, a single OSPF router is identified as the Backup Designated Router (BDR). The BDR becomes the Designated Router (DR) if the DR becomes unavailable. Best information Using the split horizon method (also called best information), routers keep track of where the information about a route came from. Routers do not report route information to the routers on that path. In other words, routers do not report information back to the router from which their information originated. BGP (Border Gateway Protocol) Border Gateway Protocol (BGP) is a policy-based, interautonomous system routing protocol that exchanges reachability information with other BGP systems. BGP Address Family Identifier (AFI) The Cisco BGP Address Family Identifier (AFI) model was introduced with multiprotocol BGP. It is designed to be scalable and modular, and to support multiple AFI and Subsequent Address Family Identifier (SAFI) configurations. BGP attributes BGP attributes are used to select the best path to be entered into the routing table and propagated to the BGP neighbors. BGP attributes can be well-known mandatory, well-known discretionary, optional transitive, or optional nontransitive. The following definitions are used to define BGP attributes: Well-known attributes are standard. All implementations of BGP support standard attributes. Well-known mandatory attributes have to be present in all implementations of BGP. Well-known discretionary attributes are implemented according to the needs of individual implementations of BGP. Optional attributes are non-standard, meaning they are specific to particular implementations of BGP. Optional transitive attributes are transmitted between two or more autonomous systems. Optional nontransitive attributes remain in a single autonomous system. BGP peer A BGP peer (also called a neighbor) is a BGP speaker that is configured to form a neighbor relationship with another BGP speaker. Neighbor relationships allow BGP speakers to directly exchange BGP routing information with one another. BGP peer group A BGP peer group consists of the neighbors of a router that is being configured. All routers in a BGP peer group have the same update policies; thus allowing updates to be generated only once for the entire peer group. BGP speaker A BGP speaker is any router that runs BGP. BGP synchronization rule The BGP synchronization rule states that a BGP router cannot use or advertise a route that it has learned from internal BGP (iBGP) to an external neighbor unless it has also been established through an internal gateway protocol, such as RIP or OSPF. Bidirectional PIM Bidirectional PIM explicitly builds shared bi-directional trees. Bidirectional PDM: Never builds a shortest path tree. May have longer end-to-end delays than PIM-SM. Is scalable because it needs no source-specific state. Binary compatible An application that runs on any Windows-supported platform, not only on the hardware for which it was originally compiled. Binary Synchronous Communications Protocol (BISYNC) A Data Link layer protocol for synchronous communication devices. Bindery The system that networks running Novell NetWare use to validate user accounts and passwords. It is the equivalent of the directory database in Windows NT. Binding The process of assigning services to network components. BISYNC (Binary Synchronous Communications Protocol) A Data Link layer protocol for synchronous communication devices. Bit The smallest unit of data a computer uses. A bit is a binary value, either a 0 or a 1. Bluetooth A proposed standard of the IEEE 802.15 committee, designed to allow people to connect in PAN (personal area network) configurations using cell phones, PDAs (personal digital assistants), printers, mice, keyboards and other Bluetooth equipped devices. B-node A type of broadcast used by NetBIOS over TCP/IP. The B-node uses UDP datagrams to broadcast for name registration and resolution. B-node broadcasts are usually not forwarded by routers, and only computers on the local network can respond. Body parts Body parts are the codes for the text, data, and other information included in an e-mail message. Boot disk A floppy disk containing an operating system that is used to boot up a PC in the absence of the PC's operating system. Boot partition The partition on a hard drive where the Windows operating system files reside. Boot.ini A file that builds the Boot Loader Operating System Selection menu. The screen that is displayed is known as the boot loader screen and allows a user to select an operating system from the screen. If no selection is made, NTLDR loads the operating system specified by the default parameter in the Boot.ini file. To change the default entry, you must edit the Boot.ini file. BootP (Bootstrap Protocol) BootP is used to discover the IP address of a device with a known MAC address. BootP is an enhancement to RARP, and is more commonly implemented than RARP. As its name implies, BootP is used by computers as they boot to receive an IP address from a BootP server. The BootP address request packet sent by the host is answered by the server. Bootstrap Protocol (BootP) BootP is used to discover the IP address of a device with a known MAC address. BootP is an enhancement to RARP, and is more commonly implemented than RARP. As its name implies, BootP is used by computers as they boot to receive an IP address from a BootP server. The BootP address request packet sent by the host is answered by the server. Bootstrap Router (BSR) A Bootstrap Router (BSR) is a capability that was added in PIM version 2 to automate and simplify the Auto-RP process. It is enabled by default in Cisco IOS releases supporting PIMv2. Border Gateway Protocol (BGP) Border Gateway Protocol (BGP) is a policy-based, interautonomous system routing protocol that exchanges reachability information with other BGP systems. Bottleneck A bottleneck is a point in a system of processes that does not have the capacity to perform the functions required of it. This lack of processing capacity impedes overall information flow and negatively impacts the performance of the whole system. Changes in the system, including increased volume, can cause bottlenecks. Bounce The longest acceptable round-trip time for a test message to travel between the monitor's home server and the target server. Boundary layer Parts of the network architecture that provide a common programming interface. Programmers can use these components to create independently-coded drivers and other programs which extend the operating system's abilities. Boundary layers in Windows include the Transport Driver Interface (TDI) and the Network Device Interface Specification (NDIS) 4.0. Bridge A data forwarding device that provides data transfer at the data link layer in the OSI model. A bridge is not used as much in networks because routers have assumed the responsibility for routing data at the network layer of the OSI model. Bridgehead server A domain controller that participates in intersite replication. Broadband Broadband signalling divides the network medium (cabling) into multiple channels, allowing several signals to traverse the medium at the same time. Broadcast In broadcast transmission, a single device transits a message to all of the other devices in a given address range. Broadcast messages can be received by all hosts on the subnet, all subnets, or all hosts on all subnets. Broadcast domain The portion of the network that can receive a broadcast. Not all routers have the capability to forward broadcasts. Those that do usually disable this feature and keep the broadcast on the local network. Broadcast storm A broadcast storm occurs when so many messages are broadcast across the network at the same time that they exceed the network's bandwidth. Broadcasts A request from the source host for a name query request on the local network. Each computer on the local network receives the broadcast and checks its local NetBIOS table to see if it owns the requested name. Brouter A device that combines the features of a bridge and a router. For data packets that use a non-routable network/transport protocol, a brouter acts like a bridge. For data packets that use a routable network/transport protocol, a brouter acts like a router. Browser A software application you use to display pages from the World Wide Web. BSR (Bootstrap Router) A Bootstrap Router (BSR) is a capability that was added in PIM version 2 to automate and simplify the Auto-RP process. It is enabled by default in Cisco IOS releases supporting PIMv2. Built-in account A built-in account is an account already created by Windows. The Guest account and the Administrator account are built-in accounts. Built-in capabilities Built-in groups are predefined groups that have predetermined set of user rights. Bus Bus is a network topology that consists of a trunk cable with nodes either inserted directly into the trunk, or nodes tapping into the trunk using offshoot cables called drop cables. Byte A unit of information made up of eight bits. Usually, a byte represents a character. C.CDF file Channel Definition Format files. Text files that contain a personalized index for a Web site, so you can download only the content that interests you. Using a.CDF converts a Web site into a channel..CHK file Exchange 2007's database engine is referred to as the Extensible Storage Engine (ESE). ESE is a transactional database that writes information into RAM memory and into a log file. Once it is in the log file, it will be written to disk. There are a number of files used to store information: An.edb file is located in the actual database itself. All of a user's messages, folders, public folders, contacts, appointment information, etc. is all stored on the.edb file. An.edb file size can exceed multiple GB. A.log file is an ESE transaction log file. All.log files are 1 MB. A.jrs file is a reserve log file which is used to commit any transactions that are still in memory in the event of the server running out of disk space. All.jrs files are 1 MB. A.chk file is used to identify which log files have been committed to the database. The size of.chk file varies from 2-3 KB. The ESE takes the following steps to write information into database files: The ESE writes a message into memory RAM when it arrives at the server. At the same time that information is written to RAM, it's written into the current.log file. All current log files are named E00.log. The information is written in a sequential format until the log file is full. When the log file is full, it will be renamed. Once it has been committed to the log file, the information is written to the.edb file. The checkpoint file is updated to indicate that the transaction log that has been committed to the database..CSV file A comma-delimited text file. Cache A file that contains host information needed to resolve names outside of authoritative domains. It also contains names and addresses of root name servers. Cache Manager A part of the I/O Manager that improves a computer's performance by temporarily storing files in memory instead of reading and writing them to the hard disk. The Cache Manager uses virtual address space to cache data. CAL (Client Access License) A client access license permits a client to connect to a Windows 2000 server. Callback A remote access server configuration that provides network security by restricting network access to a specified list of phone numbers. When a client calls the server, the server hangs up, then calls the client back at the appropriate phone number. Canonical Name (CNAME) record Enables you to associate more than one host name with an IP address. This concept is also referred to as aliasing. Carrier Sense Media Access/Collision Avoidance (CSMA/CA) CSMA/CA is the technology used by Ethernet and wireless networks to control media access and avoid (rather than detect) collisions. CSMA/CD works as follows: If a host detects traffic on the network, it experiences a longer back-off time than hosts on a wired network before attempting to transmit again. Every transmission must be acknowledged. As every frame is acknowledged by the receiving host, other hosts receive a message indicating that they must wait to transmit. Carrier Sense Multiple Access with Collision Detection (CSMA/CD) CSMA/CD is the technology used by Ethernet. CSMA/CD works as follows: The system listens for traffic, if the line is clear it begins transmitting. During the transmission, the system listens for collisions. If no collisions are detected, the communication succeeds. If collisions are detected, an interrupt jam signal is broadcast to stop all transmissions. Each system waits a random amount of time before starting over at step 1. CAS (Client Access server) Client Access server role is required in every Exchange 2007 organization because it supports the client applications Outlook Web Access and Exchange ActiveSync and also the Post Office Protocol version 3 (POP3), and Internet Message Access Protocol version 4rev1 (IMAP4) protocols. Cascading physical star A logical ring topology created with the FDDI standard. In this topology, single-attachment hubs connect single-attachment stations to a network. Case sensitive All capital and lower-case characters must be typed exactly as they appear. For example, if the password was "Himalayas" and you typed "himalayas," you would not be allowed to log on. CCR (Local Continuous Replication) Cluster Continuous Replication (CCR) combines the asynchronous log shipping and replay technology of Exchange 2007 with the failover and management features provided by the Microsoft Windows Cluster service. CCR does not have a single point of failure and provides high availability by replicating data on a passive node, so the clustered Mailbox server can operate on either node at any time. CD File System (CDFS) A read-only file system for CD-ROMs, supported by Windows 2000. CDFS (CD File System) A read-only file system for CD-ROMs, supported by Windows 2000. Central Processing Unit (CPU) The logic circuitry that responds to instructions and runs the computer. Also called a processor. Centralized computing A configuration in which all the data and applications are stored and executed on a mainframe computer. The terminals act only to accept keystrokes on the keyboard and display data from the mainframe computer. Centralized network administration The ability to manage network resources from a centralized database location. The Windows 2000 directory service provides the capability to manage resources centrally. Certificate A digitally signed statement issued by a Certification Authority (CA). It contains a public key and certifies that a specific person, organization, device, or service is the only holder of the corresponding private key. Certificates commonly use the ITU-T X.509 international standard. Certificate authority A certificate authority (CA) is the component of the public key infrastructure entrusted to issue, store, and revoke certificates. A certificate authority accepts certificate requests, verifies the information provided by the requester, creates and digitally signs the certificate, and issues the certificate to the requester. It also revokes certificates and publishes a certificate revocation list (CRL). Certificate Revocation List (CRL) Digital certificates usually expire after one year, but CAs can revoke certificates earlier for various reasons. All revoked certificates are stored in the certification revocation list, which is open to all users. This allows users to check the list to verify whether a given certificate is valid. Certificate Services The Microsoft Windows 2000 component that lets a system administrator create a certificate authority to issue, revoke, and manage digital certificates as part of a public key infrastructure. Certification Authority server A Certification Authority server creates new encryption keys for clients and publishes public keys for users. The Exchange KM Server is a Certification Authority server. CGI (Common Gateway Interface) A software program that allows Web servers to send data to an application and receive information back from the application, regardless of the operating system the application is running under. CGMP(Cisco Group Management Protocol) Cisco Group Management Protocol (CGMP) is a Cisco proprietary protocol that works between the router and the switch. In CGMP, the switch only allows multicast traffic to flow through specific ports according to client data from the router instead of flooding data across all ports. CGMP: Enables routers to inform each of their directly-connected switches of IGMP registrations from hosts accessible through the switch. Forwards multicast traffic only to ports on which the requesting routers are located. Is the most common multicast switching solution. Is based on a client/server model in which the router acts as a server and the switch acts as a client. Challenge Handshake Authentication Protocol (CHAP) CHAP is an authentication encryption protocol designed to protect passwords while in transit from a client to the logon server. CHAP periodically verifies the identity of a peer using a three-way handshake. CHAP ensures that the same client or system exists throughout a communication session by repeatedly and randomly re-testing the validated system. This test involves the security server sending a challenge message to the client. The client then performs a one-way hash function on the challenge and returns the result to the security server. The security server performs its own function on the challenge and compares its result with that received from the client. If they don't match the session is terminated. Channel Service Unit/Data Service Unit (CSU/DSU) A hardware device that converts a digital data frame from a LAN format into a WAN format and vice versa. Channels Web sites that you can customize with a.CDF file to give you only the information that you want to see. When you subscribe to a channel, Internet Explorer monitors the Web sites included in the channel and downloads only the information that fits the channel's parameters. CHAP (Challenge Handshake Authentication Protocol) CHAP is an authentication encryption protocol designed to protect passwords while in transit from a client to the logon server. CHAP periodically verifies the identity of a peer using a three-way handshake. CHAP ensures that the same client or system exists throughout a communication session by repeatedly and randomly re-testing the validated system. This test involves the security server sending a challenge message to the client. The client then performs a one-way hash function on the challenge and returns the result to the security server. The security server performs its own function on the challenge and compares its result with that received from the client. If they don't match the session is terminated. Character set A set of 256 letters, digits, and symbols specific to a country or language. The character set selected during SQL installation specifies the characters SQL Server will recognize in the various data types. The first 128 values are called printable characters, and the last 128 values are called extended characters. Printable characters are the same for each set; extended characters vary from set to set. See also Unicode characters. Checkpoint A marked point in a SQL transaction log. It represents a point at which completed transactions and modified database pages were written to disk. Chkdsk An MS-DOS utility you can use to scan and repair both FAT and Windows NT NTFS volumes. CIDR (Classless Inter-Domain Routing) A technique used to collapse Class C entries into a single entry corresponding to all the Class IDs that are being used by that organization. This allows companies to use many Class C addresses rather than requesting a Class B address, since the availability of IP addresses is scarce. Circuit Switching A circuit switched network uses a dedicated connection between sites. Circuit switching is ideal for transmitting data that must arrive quickly in the order it is sent, as is the case with real-time audio and video. Circuit-level Gateway A circuit-level gateway monitors traffic between trusted hosts and un-trusted hosts via virtual circuits or sessions. A circuit-level gateway: Verifies sequencing of session packets. Hides the private network from the public network. Does not filter packets. Rather it allows or denies sessions. Circular logging Circular logging is a logging method in which older logs are overwritten with new logging information. This method saves disk space but does not provide as much fault tolerance. Cisco Group Management Protocol (CGMP) Cisco Group Management Protocol (CGMP) is a Cisco proprietary protocol that works between the router and the switch. In CGMP, the switch only allows multicast traffic to flow through specific ports according to client data from the router instead of flooding data across all ports. CGMP: Enables routers to inform each of their directly-connected switches of IGMP registrations from hosts accessible through the switch. Forwards multicast traffic only to ports on which the requesting routers are located. Is the most common multicast switching solution. Is based on a client/server model in which the router acts as a server and the switch acts as a client. Class A address An IP address range that is assigned to networks with very large numbers of hosts. The Class A address assigns the high order bit to zero. The next seven bits complete the network ID portion of the address. The remaining 24 bits make up the host ID. The address range for the first octet (8 bits) is 1-126. Class B address An IP address range that is assigned to networks with medium to large networks. The Class B address assigns the two high order bits to binary 1 0. The next 14 bits complete the network ID. The last 16 bits are used for the host ID. The address range for the first octet (8 bits) is 128 B 191. Class C address An IP address range that is used for small local area networks. The Class C address assigns the three high order bits to binary 1 1 0. The next 21 bits are used to complete the network ID. The last 8 bits are used to represent the network ID. The address range for the first octet (8 bits) is 192 B223. Classful IP addresses Classful addresses are IP addresses that use the default subnet mask. Classful routing protocols Classful routing protocols do not include default subnet mask information in routing updates. The default subnet mask is used to identify the network and host portions of the address. Classful routing protocols are: Interior Gateway Routing Protocol (IGRP) Routing Information Protocol version 1(RIPv1) Classless Inter-Domain Routing (CIDR) A technique used to collapse Class C entries into a single entry corresponding to all the Class IDs that are being used by that organization. This allows companies to use many Class C addresses rather than requesting a Class B address, since the availability of IP addresses is scarce. Classless IP addresses Classless addresses are IP addresses that use a custom mask value to separate network and host portions of the IP address. Classless routing protocols Classless routing protocols use a custom mask value to separate network and host portions of the IP address. They are considered to be second-generation protocols because they improve on the limitations of classful protocols. The most common routing protocols are: Enhanced Interior gateway Routing Protocol (EIGRP) Intermediate System-to-Intermediate System (IS-IS) Open Shortest Path First (OSPF) Routing Information Protocol version 2 (RIPv2) Client A computer that uses files and resources from another computer on a network. Also called a workstation. Client Access License (CAL) A client access license permits a client to connect to a Windows 2000 server. Client Access server (CAS) Client Access server role is required in every Exchange 2007 organization because it supports the client applications Outlook Web Access and Exchange ActiveSync and also the Post Office Protocol version 3 (POP3), and Internet Message Access Protocol version 4rev1 (IMAP4) protocols. Client Service for NetWare (CSNW) A service included with Windows 2000 that allows a Windows workstation to use file and print resources residing on NetWare servers. Client-based administration tools Tools that allow you to perform several network administration tasks from a Windows 95/98 or Windows 2000 Professional workstation, such as creating users and groups, sharing folders, and assigning permissions to access resources. ClipBook Viewer A Windows shared resource that uses OLE to store up to 127 pieces of information, each called a ClipBook Viewer Page. Users can create and share these pages for use in OLE applications. CLNS (Connectionless Network Service) Connectionless Network Service (CLNS) is an address family that is used to identify routing sessions for protocols that use standard network service access point (NSAP) address prefixes, such as BGP. Cluster Continuous Replication (CCR) Cluster Continuous Replication (CCR) combines the asynchronous log shipping and replay technology of Exchange 2007 with the failover and management features provided by the Microsoft Windows Cluster service. CCR does not have a single point of failure and provides high availability by replicating data on a passive node, so the clustered Mailbox server can operate on either node at any time. Clustering A situation in which groups of independent computers work together as a single system. CNAME (Canonical Name) record) Enables you to associate more than one host name with an IP address. This concept is also referred to as aliasing. Coaxial Cable Coaxial cable is a type of network transmission media. It is an older technology that is usually implemented with a bus topology. It is not suitable for ring or star topologies because the ends of the cable must be terminated. It is composed of two conductors, which share a common axis, within a single cable. Cold Site A cold site is a fault tolerant strategy which provides a redundant work location. If a disaster renders a work site unusable, the effected organization may have a cold site in which to relocate. Cold sites have the following characteristics: This is the least ready of alternative site types, but it is probably the most common. The site is ready for equipment to be brought in during an emergency because there is no hardware on site. The site might have electrical power and HVAC, but it may or may not have communication links. A cold site is low cost, and may be better than nothing. A cold site often offers a false sense of security. The actual amount of work involved in getting a cold site up and running might be more than expected and might take too long to adequately keep the business running. Cold Spare A cold spare is a component that sits on the shelf until there is a failure. Cold spares obviously need more time to implement recovery, but they don't have the maintenance requirements of hot spares. COM (Component Object Model) A method that allows objects to communicate with each other. It is the basis for both OLE and ActiveX. Command line switches Codes you can use at the command prompt when starting an application or installation program to customize the way the program runs. Command prompt The 32-bit Windows command-line interface similar to the MS-DOS prompt. You can use it to start programs and type Windows commands. Common Gateway Interface (CGI) A software program that allows Web servers to send data to an application and receive information back from the application, regardless of the operating system the application is running under. Community A community is a group that contains hosts that are running the SNMP service. These communities are identified by a community name and provide the first level of security and context checking for agents. Community attribute The community (type code 8) is an optional BGP transitive attribute that filters incoming or outgoing routes. BGP communities are routes that share some common properties and policies, which allows routers to act on the community as a whole rather than on individual routes. Complete trust domain model In this Windows NT network model, every domain on the network trusts every other domain. No single domain has control over the other domains. The complete trust model distributes administration of users, groups, domains, and resources among different departments rather than using a centralized approach. Component Object Model (COM) A method that allows objects to communicate with each other. It is the basis for both OLE and ActiveX. Computer account An account entry in the local SAM database or the Active Directory domain database that identifies a computer (workstation) as part of a domain. Configuration container The configuration container is used to store information about the configuration of the Active Directory environment in Exchange 2007, such as site configuration and areas of optimal connectivity. When AD is employed over a WAN, a site for each end of the WAN link is defined along with the site link that represents the WAN connection. Exchange 2007 uses this site information to route messages within the environment. The configuration container also contains additional Exchange configuration such as the definition of the connectors within the environment, the accepted domains, and which servers hold which roles. Configuration partition An Active Directory partition that stores the domain, site, and replication structure of a Windows 2000 network. Connection object An Active Directory object that represents a uni-directional connection between a source and target replication partner over which Active Directory data is replicated. Connectionless communication Connectionless communications assume an existing link between devices and allow transmission without extensive session establishment. Connectionless communications use no error checking, session establishment, or acknowledgements. Connectionless protocols allow quick, efficient communication at the risk of data errors and packet loss. Connectionless protocols are a good choice where speed is important and smaller chunks of data are being sent. Connectionless Network Service (CLNS) Connectionless Network Service (CLNS) is an address family that is used to identify routing sessions for protocols that use standard network service access point (NSAP) address prefixes, such as BGP. Connection-oriented communication Connection-oriented communication does not assume that there is an existing link between devices. Connection-oriented communications use error detection/correction, session establishment, or acknowledgements, and, if necessary, retransmission. Connection-oriented communication provides a more reliable communication when are delivery is more important than speed and is a good method to use when larger chunks of data are being sent. Console The Microsoft Management Console (MMC) is a graphical interface for the administration of Windows 2000 and some earlier Microsoft operating systems. It accommodates various "snap-in" tools. Console tree The left pane of the Microsoft Management Console (MMC). It shows a hierarchical structure of functions and/or objects. Control Panel A Windows utility that displays other utilities that are used to manage the local computer. Convergence A routing metric is a value used by routing protocols to determine the length of paths within a network. Different routing protocols use various measurements to calculate metrics, such as: Bandwidth Network delay Hop count Interface speed Path cost Load MTU Reliability Communication cost Cookie Marker downloaded from Internet servers and stored on the hard drives of client computers. Cookies store information about your preferences, browser settings, location, and so on. They identify you (or your browser) to Web sites. Cooperative multitasking A system in which each application currently running a process voluntarily passes control of the CPU to another application between processes. It is also called non-preemptive multitasking. Copy backup A specific type of backup that backs up selected files and folders but does not mark their archive attributes. CPU (Central Processing Unit) The logic circuitry that responds to instructions and runs the computer. Also called a processor. CRC (Cyclic Redundancy Checking) Cyclic redundancy checking is a method used to verify correct transmission and reception of data that has been sent across a network. Creator Owner A built-in group that is used for network administration. It includes the user that created or took ownership of a resource. CRL (Certificate Revocation List) Digital certificates usually expire after one year, but CAs can revoke certificates earlier for various reasons. All revoked certificates are stored in the certification revocation list, which is open to all users. This allows users to check the list to verify whether a given certificate is valid. Crossover cable A cable connecting one hub with another hub or with a repeater in a network. CSMA/CA (Carrier Sense Media Access/Collision Avoidance) CSMA/CA is the technology used by Ethernet and wireless networks to control media access and avoid (rather than detect) collisions. CSMA/CD works as follows: If a host detects traffic on the network, it experiences a longer back-off time than hosts on a wired network before attempting to transmit again. Every transmission must be acknowledged. As every frame is acknowledged by the receiving host, other hosts receive a message indicating that they must wait to transmit. CSMA/CD (Carrier Sense Multiple Access with Collision Detection) CSMA/CD is the technology used by Ethernet. CSMA/CD works as follows: The system listens for traffic, if the line is clear it begins transmitting. During the transmission, the system listens for collisions. If no collisions are detected, the communication succeeds. If collisions are detected, an interrupt jam signal is broadcast to stop all transmissions. Each system waits a random amount of time before starting over at step 1. CSNW (Client Service for NetWare) A service included with Windows 2000 that allows a Windows workstation to use file and print resources residing on NetWare servers. CSR subsystem The Windows subsystem that supports 32- and 16-bit Windows and MS-DOS applications within Windows 2000. Also called the Win32 subsystem, client/server subsystem, or CSRSS. CSU/DSU (Channel Service Unit/Data Service Unit) A hardware device that converts a digital data frame from a LAN format into a WAN format and vice versa. Custom subnet mask A subnet mask that is defined by a network administrator. Each host on a TCP/IP network requires a subnet mask. If a custom subnet mask is not used, then a default subnet mask is automatically used. Cyclic Redundancy Checking (CRC) Cyclic redundancy checking is a method used to verify correct transmission and reception of data that has been sent across a network. D Daily copy backup A specific backup type that copies only files and folders that have changed during that day. It does not mark their archive attributes. DARPA (Department of Defense Advanced Research Projects Agency) The agency of the U.S. Department of Defense which created the industry-standard TCP/IP suite of protocols based on packet-switching network experiments conducted in the late 1960's and 1970's. Data definition The process of creating a database and associated objects, such as tables, indexes, constraints, defaults, rules, procedures, triggers, and views. Data Encryption Standard (DES) Data Encryption Standard is a common symmetric cryptography method. It was created in 1972 and re-certified in 1993. DES has a limitation of 56-bit keys and offers little encryption security since it can be easily broken. Data Link Control (DLC) A non-routable protocol. Windows NT computers use DLC to connect to IBM mainframes via 3270 terminal emulators and to connect to IBM AS/400 computers via 5250 emulators. Microsoft SNA Server for Windows NT uses DLC to communicate with mainframes on a token ring network. DLC is also used with some HP print devices that are attached to the network through a built-in adapter card. Data Link Layer (OSI model) Layer 2 of the OSI reference model. This layer provides reliable transit of data across a physical link. The data link layer is concerned with physical addressing, network topology, line discipline, error notification, ordered delivery of frames, and flow control. The IEEE has divided this layer into two sublayers: the MAC sublayer and the LLC sublayer. Sometimes simply called link layer. Roughly corresponds to the data link control layer of the SNA model. See also application layer, MAC address, network layer, physical layer, presentation layer, session layer, and transport layer. Data redundancy Creating and maintaining multiple copies of the same data. Database A collection of information, tables, and other objects organized and presented to serve a specific purpose, such as facilitating searching, sorting, and recombining data. Databases are stored in files. Database replication The process by which a WINS server can resolve NetBIOS names of hosts registered with another WINS server. For example, if a host on subnet A is registered with a local WINS server, but wants to communicate with a host on subnet B where the host is registered with a different WINS server, the NetBIOS name cannot be resolved unless the two WINS servers have replicated their databases with each other. Datagram Another term used to describe a packet. The term is also used to describe the Internet protocol known as the User Datagram Protocol, a connectionless protocol that does not guarantee delivery of datagrams. DCOM (Distributed Component Object Model) A method of configuring a client/server application so that several computers can use it at the same time. DCOM uses remote procedure calls (RPCs) to allow applications to interoperate and communicate with each other. DDE (Dynamic Data Exchange) A system by which applications can share data and commands. Both applications must support DDE. DDS (Digital Data Service) Digital lines to which a computer can connect using a channel service unit/digital service unit (CSU/DSU). These kinds of lines carry 99 percent error-free digital signals at speeds ranging from 2.4 to 56 kilobits per second. DDS lines are normally leased lines rather than on-demand. An exception is Switched 56, which is a system of on-demand (dial-up) 56 Kbps DDS lines. DEC (Digital Equipment Corporation) A computer manufacturing company that makes RISC-based processors such as Alpha. Default An action that a system performs, or a characteristic that it displays unless explicitly instructed otherwise. Default gateway The gateway you always want to use to communicate with a host on a different network. It receives packets from the local network and transfers them to another gateway on the other network. You specify a default gateway when you configure TCP/IP. Default route If a default route is configured, the router will send packets via that route in cases where a dynamic route is not provided. This can be used to create sufficient reachability, especially for route between an edge and the core. Default routes also reduce the burden on network resources caused by dynamic routing. Default subnet mask A subnet mask that is used on TCP/IP networks that are not divided into subnets. All TCP/IP hosts require a subnet mask even if the network is a single segment. Demand paging A Windows process that moves data between the computer's RAM and a paging file on the hard drive. Demilitarized Zone (DMZ) DMZ (Demilitarized Zone) is a buffer subnet. A DMZ should only contain servers that are to be accessed by external visitors. Often it is assumed that any server placed in the DMZ will be compromised. Thus, no mission critical or sensitive systems are located in a DMZ. A domain controller may appear in a DMZ when the DMZ is an entire isolated domain, however this is not common. User workstations are never located in a DMZ. Backup servers, unless specifically deployed for just the DMZ, are never located in a DMZ. Department of Defense Advanced Research Projects Agency (DARPA) The agency of the U.S. Department of Defense which created the industry-standard TCP/IP suite of protocols based on packet-switching network experiments conducted in the late 1960's and 1970's. DES (Data Encryption Standard) Data Encryption Standard is a common symmetric cryptography method. It was created in 1972 and re-certified in 1993. DES has a limitation of 56-bit keys and offers little encryption security since it can be easily broken. Designated Router (DR) A Designated Router (DR) is a router in a PIM-Sparse Mode tree that initiates the Join/Prune message cascade upstream in response to the IGMP membership information that is received from IGMP hosts. Destination replication partner A replication partner that receives updates from a source replication partner. Also called a target replication partner. Device driver A software component that allows a hardware device to communicate with the operating system of a computer. DFS (Distributed File System) A file management system that lets users and administrators create a virtual file structure such that a folder or hierarchy of folders appear to contain a collection of files that are, if fact, located on multiple computers or drives connected at various physical locations on the network. A Dfs directory tree helps users to browse through, search for, and access data on the network. DHCP (Dynamic Host Configuration Protocol) A protocol that dynamically assigns IP addresses to each computer on a network. DHCP discover A message that makes a request for an IP lease. The message contains the client's hardware address and computer name, so that DHCP servers know which client sent the request. DHCP Manager A Microsoft utility used to manage DHCP servers. DHCP offer All DHCP servers that have valid IP addressing information available send a DHCP offer to the client when the client makes a request. DHCP request The client will initialize TCP/IP and broadcasts a request for the location of a DHCP server and IP addressing information. DHCP scope The ability to set a start and end range for the assignment of IP addresses using DHCP. Addresses can also be excluded from the available addresses as well. The scope is set using the DHCP Console. Dial-up Networking A software program that allows a client computer to connect to an external or remote network via modem. It is the client version of RAS. Examples of dial-up networking include connecting from home to a computer at work over the phone lines or connecting with an internet service provider by modem. Differential backup A backup process that copies to tape only those files that have not been marked by previous backups. A differential backup does not mark the files after backing them up. Diffuse Mode (Scatter Mode) One mode that an infrared device operates in is diffuse mode (also called scatter mode), which operates by broadcasting a large beam of light rather than a narrow beam. It does not require line-of-sight connections. Diffusing Update Algorithm Link-state (DUAL) Diffusing Update Algorithm Link-state (DUAL) technology makes decisions concerning EIGRP routing computations and guarantees freedom from routing loops. DUAL tracks all routes advertised by neighbors, and uses metrics (also called cost) to select the best path and a second best path to reach a destination. Dig Dig is the Linux preferred tool for testing name resolution. Dig resolves (looks up) the IP address of a host name. Displays other name resolution-related information such as the DNS server used for the lookup request. Digital certificates Encoded computer information that provides verification of the identity of a client or server. These certificates include encoded information that identifies a particular person, company, or computer, and are often used to distribute public encryption keys to recipients. Digital Data Service (DDS) Digital lines to which a computer can connect using a channel service unit/digital service unit (CSU/DSU). These kinds of lines carry 99 percent error-free digital signals at speeds ranging from 2.4 to 56 kilobits per second. DDS lines are normally leased lines rather than on-demand. An exception is Switched 56, which is a system of on-demand (dial-up) 56 Kbps DDS lines. Digital envelope A method of hiding the content of a message from anyone but the recipient. The sender uses the recipient's public key to encrypt the contents of the message. The recipient uses her own private key to decrypt and read the message. Digital Equipment Corporation (DEC) A computer manufacturing company that makes RISC-based processors such as Alpha. Digital Network Architecture (DNA) In the mid-1970s, Digital Equipment Corporation developed a protocol suite known as Digital Network Architecture (DNA). It is also known as DECnet. The Physical and Data Link layers of DNA were the predecessors of the Ethernet IEEE 802.3 standard. Digital signature A method of verifying the sender of a message, but does not encrypt the message itself. The sender uses his own private key to encrypt a digital signature attached to a message. The recipient uses the sender's public key to decrypt the signature and verify the sender's identity. Digital Subscriber Line (DSL) DSL or Digital Subscriber Line is a form of high-speed dial-up connection used to connect remote systems to the Internet. DSL operates over existing copper phone lines and is an economical choice for homes and small businesses. Digital Volt Meter (DVM) An electrical device that you can use to diagnose cable problems. A DVM can determine if there is a break or short in the cable by testing the resistance (measured in ohms) of the network cable. Direct Memory Access (DMA) Direct Memory Access (DMA) channels are conduits used by high-speed devices to communicate directly with RAM, bypassing the CPU. Directory replication Directory replication is the process of sharing directory information between servers inside and between sites. Directory Service Agent (DSA) A process that runs on a domain controller and provides access to the Active Directory database. Directory Services Restore Mode A special safe mode you use to restore the system state data on a domain controller. Direct-Sequence Spread Spectrum (DSSS) A type of signalling method, used by a wireless networking architecture, where the transmitter breaks data into pieces and sends the pieces across multiple frequencies in a defined range. DSSS is more susceptible to interference and less secure then other forms of signalling, such as Frequency Hopping Spread Spectrum (FHSS). DirectX APIs A low-level API that provides fast response to user input. Microsoft designed DirectX specifically to run graphically-intensive computer games. DirectX components are Microsoft DirectDraw, Microsoft DirectPlay, and Microsoft DirectSound. Disk partition Also called a partition. A portion of the free space on a hard disk that you format with a file system. Partitions can be either primary or extended. Distance Vector Multicast Routing Protocol (DVMRP) Distance Vector Multicast Routing Protocol (DVMRP) is a protocol that shares information between routers to transport IP Multicast packets among networks. Distance vector routing protocol Class of routing algorithms that iterate on the number of hops in a route to find a shortest-path spanning tree. Distance vector routing algorithms call for each router to send its entire routing table in each update, but only to its neighbors. Distance vector routing algorithms can be prone to routing loops, but are computationally simpler than link state routing algorithms. Also called Bellman-Ford routing algorithm. See also link state routing algorithm. Distribute list A distribute list is a type of access list that is applied to routing updates. Unlike normal access lists, distribute lists can control routing updates no matter their origin. Distributed applications Applications that split processing tasks between a client (front-end) and a server (back-end). Distributed Component Object Model (DCOM) A method of configuring a client/server application so that several computers can use it at the same time. DCOM uses remote procedure calls (RPCs) to allow applications to interoperate and communicate with each other. Distributed File System (DFS) A file management system that lets users and administrators create a virtual file structure such that a folder or hierarchy of folders appear to contain a collection of files that are, if fact, located on multiple computers or drives connected at various physical locations on the network. A Dfs directory tree helps users to browse through, search for, and access data on the network. Distributed Management Interface (DMI) The Distributed Management Interface (DMI) is a standard for organizing information about desktop, notebook, and server computers. DMI is part of the System Management BIOS (SMBIOS) specification which allows data about a system to be stored in the individual system's BIOS. Management software interfaces with the BIOS on a monitored system to gather this information and assemble it into an administrator-specified format such as a report or a database. Distributed Parity Distributed parity is a method of data protection used in a RAID 5 configuration. Duplicate data (parity) is placed on multiple disks (distributed) to protect against data loss in the event of a storage disk failure. Distributed processing A technique of using both the client and server's processors to complete a task. The client or "front end" accepts input and runs simple calculations, while the server or "back end" handles processes that require more processing power. Distribution group A distribution group is a universal group that has been mail-enabled, such as a security group. A distribution group can be used to send an e-mail to a large number of people in an Exchange organization, such as entire departments or groups. Distribution list A distribution list contains addresses for individual users, public folders, and other distribution lists. They allow each member to receive a copy of a message sent to the entire list. Applications use distribution lists. Distribution tree A distribution tree shows the source of multicast information and the path that multicast traffic use across the network infrastructure. DLC (Data Link Control) A non-routable protocol. Windows NT computers use DLC to connect to IBM mainframes via 3270 terminal emulators and to connect to IBM AS/400 computers via 5250 emulators. Microsoft SNA Server for Windows NT uses DLC to communicate with mainframes on a token ring network. DLC is also used with some HP print devices that are attached to the network through a built-in adapter card. DMA (Direct Memory Access) Direct Memory Access (DMA) channels are conduits used by high-speed devices to communicate directly with RAM, bypassing the CPU. DMI (Distributed Management Interface) The Distributed Management Interface (DMI) is a standard for organizing information about desktop, notebook, and server computers. DMI is part of the System Management BIOS (SMBIOS) specification which allows data about a system to be stored in the individual system's BIOS. Management software interfaces with the BIOS on a monitored system to gather this information and assemble it into an administrator-specified format such as a report or a database. DMZ (Demilitarized Zone) DMZ (Demilitarized Zone) is a buffer subnet. A DMZ should only contain servers that are to be accessed by external visitors. Often it is assumed that any server placed in the DMZ will be compromised. Thus, no mission critical or sensitive systems are located in a DMZ. A domain controller may appear in a DMZ when the DMZ is an entire isolated domain, however this is not common. User workstations are never located in a DMZ. Backup servers, unless specifically deployed for just the DMZ, are never located in a DMZ. DNA (Digital Network Architecture) In the mid-1970s, Digital Equipment Corporation developed a protocol suite known as Digital Network Architecture (DNA). It is also known as DECnet. The Physical and Data Link layers of DNA were the predecessors of the Ethernet IEEE 802.3 standard. DNS (Domain Name Server) A server that maintains a database of IP address/computer name mappings. A DNS server can run on Windows NT, Unix, or NetWare (5). The DNS has the responsibility to resolve fully qualified domain names and other host names to IP addresses. In DNS, the clients are called resolvers and the servers are called name servers. DNS (Domain Name System) A hierarchical client/server-based database management system that translates computer names into IP addresses. DNS maps to the application layer and uses UDP and TCP as the underlying protocols. Clients, known as resolvers, contact name servers for the IP address they are seeking. DNS Domain A domain that defines different levels of authority in a hierarchical structure. The highest level is called the root domain. The other levels of domains are currently defined as com, edu, org, net, gov, mil, num, and arpa. Second level domains are any domains defined by companies such as Microsoft.com or Novell.com. DNS Service Discovery (DNS-SD) A service location feature used in Zeroconf networking implementation. DNS-SD allows IP hosts to automatically find available services, such as file servers, printers, and routers. DNS-SD is a Mac OS related feature. DNS-SD (DNS Service Discovery) A service location feature used in Zeroconf networking implementation. DNS-SD allows IP hosts to automatically find available services, such as file servers, printers, and routers. DNS-SD is a Mac OS related feature. Domain A logical grouping of computers and users. In a domain, all users have access to a central directory database that stores security and user account information for the domain. Domain Admins A built-in global group that is added automatically to the Administrators local group, making all members of Domain Admins group domain administrators. Domain controller Windows 2000 domain controllers contain copies of the Active Directory database. They provide a centralized approach to administration and account maintenance. Domain Dfs A configuration of Dfs in which Active Directory stores the information about the virtual file structure. Advantages include fault-tolerance. Domain Guests A built-in global group in which the Guest user account is a member. Domain Name A domain name locates entities (for example, websites) on the Internet. Domain names are managed within a domain name system (DNS), which is a hierarchy that is made up of the following components:. (dot) domain (also called the root domain) Top Level Domains (TLDs) such as.com,.edu,.gov Additional domains such as yahoo.com, microsoft.com, etc. Domain Name Server (DNS) A server that maintains a database of IP address/computer name mappings. A DNS server can run on Windows NT, Unix, or NetWare (5). The DNS has the responsibility to resolve fully qualified domain names and other host names to IP addresses. In DNS, the clients are called resolvers and the servers are called name servers. Domain Name System (DNS) A hierarchical client/server-based database management system that translates computer names into IP addresses. DNS maps to the application layer and uses UDP and TCP as the underlying protocols. Clients, known as resolvers, contact name servers for the IP address they are seeking. Domain partition An Active Directory partition that stores objects, attribute, and attribute values for a particular domain. Each domain in Active Directory has its own domain partition. Domain user accounts User name and password information stored in the Active Directory database on the domain controllers. Domain Users Any user account created in a Windows domain is a domain user. Domain Users is a global group. DOS See MS-DOS. DR (Designated Router) A Designated Router (DR) is a router in a PIM-Sparse Mode tree that initiates the Join/Prune message cascade upstream in response to the IGMP membership information that is received from IGMP hosts. Drive mapping A specific letter used to map a drive or volume on a workstation or server. DROTHER Any other router that is not a DR or a BDR is called a DROTHER. This is simply a term used to describe a non-DR or non-BDR router. It is not technically an OSPF router role. DSA (Directory Service Agent) A process that runs on a domain controller and provides access to the Active Directory database. DSL (Digital Subscriber Line) DSL or Digital Subscriber Line is a form of high-speed dial-up connection used to connect remote systems to the Internet. DSL operates over existing copper phone lines and is an economical choice for homes and small businesses. DSSS (Direct-Sequence Spread Spectrum) A type of signalling method, used by a wireless networking architecture, where the transmitter breaks data into pieces and sends the pieces across multiple frequencies in a defined range. DSSS is more susceptible to interference and less secure then other forms of signalling, such as Frequency Hopping Spread Spectrum (FHSS). DUAL (Diffusing Update Algorithm Link-state) Diffusing Update Algorithm Link-state (DUAL) technology makes decisions concerning EIGRP routing computations and guarantees freedom from routing loops. DUAL tracks all routes advertised by neighbors, and uses metrics (also called cost) to select the best path and a second best path to reach a destination. Dual Ring A dual ring is an enhanced version of the ring networking topology. A dual ring network includes two rings; the primary and secondary rings, which increase performance and fault tolerance. A break in one ring in a dual ring configuration has no effect on communications. A decrease in bandwidth might result, but data can be sent on the other ring. Dual Stack A method used to allow concurrent support for both IPv4 and IPv6 within the same network. Dual-boot The ability to boot a computer with either one of two operating systems. Both operating systems must be loaded on the computer. At bootup a menu prompts the user to load the operating system the computer should use. Duplex (Simplex) Simplex and duplex are methods of communication transmission. Simplex is the one-way transmission of a signal across a medium. Duplex is the two-way transmission of a signals across a medium. There are two types of duplex transmission; half-duplex and full-duplex. Half-duplex allows transmission of signals, one party at a time. Full-duplex allows transmission and reception of signals to occur concurrently. DVM (Digital Volt Meter) An electrical device that you can use to diagnose cable problems. A DVM can determine if there is a break or short in the cable by testing the resistance (measured in ohms) of the network cable. DVMRP (Distance Vector Multicast Routing Protocol) Distance Vector Multicast Routing Protocol (DVMRP) is a protocol that shares information between routers to transport IP Multicast packets among networks. Dynamic Data Exchange (DDE) A system by which applications can share data and commands. Both applications must support DDE. Dynamic disk A disk device managed by Windows 2000 Disk Management. Dynamic disks do not contain partitions or logical drives. They can contain only dynamic volumes created with Disk Management. They cannot be accessed by earlier version of Windows or by MS-DOS. Dynamic distribution group A dynamic distribution group is an Exchange distribution group whose membership is defined by the results of a query which is executed every time a message is sent to the group. This is optimal for environments in which people move groups or buildings often and e-mail groups need to be able to accommodate changes as they occur. Dynamic Host Configuration Protocol (DHCP) A protocol that dynamically assigns IP addresses to each computer on a network. Dynamic routing Dynamic routing is an addressing method that senses changes in the network topology and responds accordingly without administrator involvement. Dynamic routers: Propagate changes and shifts in the network topology to each router in the network, causing the routing tables on each router to always be up to date. Are responsible for all networks to which they are connected. Employ additional processes or services to exchange routing information between routers. E.EDB file Exchange 2007's database engine is referred to as the Extensible Storage Engine (ESE). ESE is a transactional database that writes information into RAM memory and into a log file. Once it is in the log file, it will be written to disk. There are a number of files used to store information: An.edb file is located in the actual database itself. All of a user's messages, folders, public folders, contacts, appointment information, etc. is all stored on the.edb file. An.edb file size can exceed multiple GB. A.log file is an ESE transaction log file. All.log files are 1 MB. A.jrs file is a reserve log file which is used to commit any transactions that are still in memory in the event of the server running out of disk space. All.jrs files are 1 MB. A.chk file is used to identify which log files have been committed to the database. The size of.chk file varies from 2-3 KB. The ESE takes the following steps to write information into database files: The ESE writes a message into memory RAM when it arrives at the server. At the same time that information is written to RAM, it's written into the current.log file. All current log files are named E00.log. The information is written in a sequential format until the log file is full. When the log file is full, it will be renamed. Once it has been committed to the log file, the information is written to the.edb file. The checkpoint file is updated to indicate that the transaction log that has been committed to the database. EAP (Extensible Authentication Protocol) EAP is an authentication protocol (an extension of PPP). It is a set of interface standards that provide various authentication methods (smartcards, biometrics, and digital certificates), define access definitions, providing protection mechanisms and custom solutions, and does not maintain a database of user accounts and passwords. EAPoL (Extensible Authentication Protocol over LAN) The Extensible Authentication Protocol over LAN is used for authentication of 802.1X port access control over either wired or wireless LANs. Eavesdropping Eavesdropping is the act of capturing and examining traffic on a network cable. Eavesdropping is the primary security vulnerability of networking systems using 802.11 technology. On wireless networks, eavesdropping is made more difficult by using WEP keys. Fiber optic cable is the most resistant to tapping and eavesdropping. Fiber optic cable transmits light pulses rather than electricity to communicate. Thus, it is not susceptible to most forms of interference or wire tapping technologies. ThickNet (10Base5 coax), 10Base2 (ThinNet coax), and 10BaseT (STP and UTP) are very susceptible to tapping and eavesdropping. EBGP (External BGP) External BGP (EBGP) is used by BGP to route information between autonomous systems. Edge Rules agent Transport policy agents apply transport policies to e-mails within an Exchange organization. There are two types of transport policy agents in Exchange 2007: A Transport Rules agent runs on a Hub Transport server and implements policies set by administrators to all e-mail that travels in and out of an Exchange organization. An Edge Rules agent runs on an Edge Transport server and helps control spam and unwanted mail flow within an organization. Edge Transport server The Edge Transport server handles all Internet-facing mail flow and provides Simple Mail Transfer Protocol (SMTP) relay and smart host services for the Exchange 2007 organization. EDirectory NetWare 4.x and higher uses a directory service called eDirectory (formerly called Novell Directory Services (NDS)). User accounts are configured in the directory. eDirectory can also run on other servers such as Windows and Linux. Effective permission The combined rights a user has to perform specific network functions and access network resources. EGP (Exterior Gateway Protocol) Exterior Gateway Protocol (EGP) is a routing protocol that exchanges routing information between autonomous systems. BGP is the most common EGP protocol. EIDE (Enhanced Integrated Drive Electronics) A standard electronic interface that allows a computer to communicate with a storage device such as the hard drive or a CD-ROM drive. EISA (Extended Industry Standard Architecture) A 32-bit I/O bus slot providing compatibility with 386 through Pentium machines. EISA buses: Have a maximum throughput rate of 33 MB/s. Offer bus mastering which is a mini-processor on the expansion card. The mini-processor assumes the task from the CPU of transferring data to and from memory. Offer a second row of pins to a standard ISA bus. Provide backward compatibility with ISA cards. Allow EISA cards to take advantage of both rows of pins (the 32-bit data path) to improve transfer rates and increase addressable memory. Allow for automatic configuration of system resources (addresses, DMA channels and IRQs). Support sharing of system resources. Allow multiple EISA cards to share the same interrupt. EISA supports multiprocessing by allowing more than one CPU to share the bus. Are usually black, though they are sometimes white. Electromagnetic Interference (EMI) The disruption of one electronic device, caused by an electromagnetic field (in the radio frequency spectrum) generated by another electronic device. E-mail Address policies E-mail Address policies are used to generate e-mail addresses for Exchange recipients within an Exchange 2007 organization. Policies can be used to generate e-mail addresses for a number of environments, such as SMTP, X400, Lotus Notes, or Novell GroupWise. E-mail client An e-mail client is a software application that supports specific protocols and provides the user with an interface to a server. Emergency Repair Disk (ERD) A backup disk that can provide the necessary files to bring back the Windows operating system in the case of a disk disaster running the Windows operating system. You create an ERD using Windows 2000. EMI (Electromagnetic Interference) The disruption of one electronic device, caused by an electromagnetic field (in the radio frequency spectrum) generated by another electronic device. Encapsulating Security Payload (ESP) Encapsulating Security Payload (ESP) is one of two services comprising IPSec. ESP supports both authentication of the sender and is used primarily to encrypt and secure the data transferred between IPSec partners. Encapsulation The process of adding an additional header to a packet before transporting the packet onto the network. For example, NetBIOS can be encapsulated with an IP header. Encryption A security technique that uses a cryptographic algorithm to encode information so that only someone with the proper key can unencode it. Enhanced Integrated Drive Electronics (EIDE) A standard electronic interface that allows a computer to communicate with a storage device such as the hard drive or a CD-ROM drive. Enhanced Small Device Interface (ESDI) A type of hard disk that uses CHS addressing and has a 1024 cylinder limitation. ESDI hard disks are predecessors of the newer IDE disks. ERD (Emergency Repair Disk) A backup disk that can provide the necessary files to bring back the Windows operating system in the case of a disk disaster running the Windows operating system. You create an ERD using Windows 2000. ErrorControl levels The values Windows uses to determine what to do in case of an error in loading or initializing drivers. The levels are 0x0 (ignore the error), 0x1 (display an error message then ignore the error), 0x2 (use the LastKnownGood control set and restart), 0x3 (stop the boot sequence and display an error message). ESDI (Enhanced Small Device Interface) A type of hard disk that uses CHS addressing and has a 1024 cylinder limitation. ESDI hard disks are predecessors of the newer IDE disks. ESE (Extensible Storage Engine) Exchange 2007's database engine is referred to as the Extensible Storage Engine (ESE). ESE is a transactional database that writes information into RAM memory and into a log file. Once it is in the log file, it will be written to disk. There are a number of files used to store information: An.edb file is located in the actual database itself. All of a user's messages, folders, public folders, contacts, appointment information, etc. is all stored on the.edb file. An.edb file size can exceed multiple GB. A.log file is an ESE transaction log file. All.log files are 1 MB. A.jrs file is a reserve log file which is used to commit any transactions that are still in memory in the event of the server running out of disk space. All.jrs files are 1 MB. A.chk file is used to identify which log files have been committed to the database. The size of.chk file varies from 2-3 KB. The ESE takes the following steps to write information into database files: The ESE writes a message into memory RAM when it arrives at the server. At the same time that information is written to RAM, it's written into the current.log file. All current log files are named E00.log. The information is written in a sequential format until the log file is full. When the log file is full, it will be renamed. Once it has been committed to the log file, the information is written to the.edb file. The checkpoint file is updated to indicate that the transaction log that has been committed to the database. ESP (Encapsulating Security Payload) Encapsulating Security Payload (ESP) is one of two services comprising IPSec. ESP supports both authentication of the sender and is used primarily to encrypt and secure the data transferred between IPSec partners. Ethernet One of the major families of network architectures. The structure of all Ethernet networks is based on the bus topology. Most Ethernet networks use baseband signaling and CSMA/CD as a media access method. Event ID The identification for the event that displays in the Event Detail window in the Event Viewer. Event log Any of three log files in which Windows records monitored events such as errors, warnings, and the success or failure of tasks. Event logs include the system, security, and application logs. You can view these logs in the Event Viewer. Event Viewer An administration tool that provides information about such events as errors, warnings, and the success or failure of tasks. Everyone A special group or identity that includes all users and can be used to assign permissions that all users in a domain hold in common, including guests and users from other domains. Exchange 2007 Management Console The Exchange 2007 Management Console is a graphic interface used to manage an Exchange environment. It has been simplified from previous versions of Exchange so it now focuses only on the most commonly executed tasks. Additional tasks that could traditionally only be performed in REGEDIT or ADSIEDIT were also added to the Exchange Management Console to improve ease of use. In Exchange 2003, the information shown in the tree-pane was dependent on the configuration of your Exchange Server. This pane is now static in Exchange 2007 Management Console so no matter how many servers you have, what options have been chosen, or what has been installed, the tree-pane will always be the same. Exchange ActiveSync Exchange ActiveSync is a protocol used by Internet-enabled mobile devices to send and retrieve Exchange data. Exchange Management Console The Exchange Management Console is the graphical administration tool. It is comprised of a three-paned view that includes a tree view, results, and an actions pane. It cannot perform many of the administrative tasks that can be performed in the Exchange Management Shell. Exchange Management PowerShell The Exchange 2007 Management Shell environment allows administrators to perform all of their tasks from a command line environment, thus making it easier to automate tasks. The PowerShell must be installed before Exchange 2007 is fully installed, then extensions are installed to the PowerShell during Exchange 2007 installation to create the Exchange 2007 PowerShell environment. The PowerShell uses with verb/noun-based syntax and is the primary platform for all administration; the graphical interface is simply running atop of the command shell. Exchange Management Shell The Exchange 2007 Management Shell environment allows administrators to perform all of their tasks from a command line environment, thus making it easier to automate tasks. The PowerShell must be installed before Exchange 2007 is fully installed, then extensions are installed to the PowerShell during Exchange 2007 installation to create the Exchange 2007 PowerShell environment. The PowerShell uses with verb/noun-based syntax and is the primary platform for all administration; the graphical interface is simply running atop of the command shell. Exchange PowerShell Microsoft Exchange Management Shell (Windows PowerShell) is a command line environment designed for automating administration and maintenance. The Exchange Management Shell is the primary management interface of 2007. Exchange storage group A Microsoft Exchange storage group is a collection of Exchange stores (databases). A Recovery Storage Group (RSG) is a special storage group used for recovering Mailbox stores. Executive Service