|1+1||A method of protecting traffic in which a protection channel exists for each working
traffic channel. For optical systems, the protection channel fibers can be routed over
a path separate from the working fibers. The traffic signal is bridged to both the
working and protection transmitters so the protection signal can be selected quickly
if the working channel fails.
|1:n||A method of protecting traffic in which one protection channel exists for n traffic
channels. Only one traffic channel can be switched to the protection channel at any
|1G mobile network||First generation mobile network. Refers to the initial category of mobile wireless
networks that use analog technology only. Advanced Mobile Phone Service (AMPS)
is an example of a 1G mobile network standard.
|10Base2||10-Mbps baseband Ethernet specification using 50-ohm thin coaxial cable. 10Base2,
which is part of the IEEE 802.3 specification, has a distance limit of 606.8 feet
(185 meters) per segment. See also Cheapernet, EtherChannel, IEEE 802.3, and
|10Base5||10-Mbps baseband Ethernet specification using standard (thick) 50-ohm baseband
coaxial cable. 10Base5, which is part of the IEEE 802.3 baseband physical layer
specification, has a distance limit of 1640 feet (500 meters) per segment. See also
EtherChannel and IEEE 802.3.
|10baseF||10-Mbps baseband Ethernet specification that refers to the 10BaseFB, 10BaseFL, and
10BaseFP standards for Ethernet over fiber-optic cabling. See also 10BaseFB,
10BaseFL, 10BaseFP, and EtherChannel.
|10baseFB||10-Mbps baseband Ethernet specification using fiber-optic cabling. 10BaseFB is part
of the IEEE 10BaseF specification. It is not used to connect user stations, but instead
provides a synchronous signaling backbone that allows additional segments and
repeaters to be connected to the network. 10BaseFB segments can be up to 1.24 miles
(2000 meters) long. See also 10BaseF and EtherChannel.
|10BaseFL||10-Mbps baseband Ethernet specification using fiber-optic cabling. 10BaseFL is part
of the IEEE 10BaseF specification and, although able to interoperate with FOIRL, is
designed to replace the FOIRL specification. 10BaseFL segments can be up to 3280
feet (1000 meters) long if used with FOIRL, and up to 1.24 miles (2000 meters) if
10BaseFL is used exclusively. See also 10BaseF, EtherChannel, and FOIRL.
|10BaseFP||10-Mbps fiber-passive baseband Ethernet specification using fiber-optic cabling.
10BaseFP is part of the IEEE 10BaseF specification. It organizes a number of
computers into a star topology without the use of repeaters. 10BaseFP segments can
be up to 1640 feet (500 meters) long. See also 10BaseF and EtherChannel.
|10BaseT||10-Mbps baseband Ethernet specification using two pairs of twisted-pair cabling
(Categories 3, 4, or 5): one pair for transmitting data and the other for receiving data.
10BaseT, which is part of the IEEE 802.3 specification, has a distance limit of
approximately 328 feet (100 meters) per segment. See also EtherChannel and IEEE
|10Broad36||10-Mbps broadband Ethernet specification using broadband coaxial cable.
10Broad36, which is part of the IEEE 802.3 specification, has a distance limit of 2.24
miles (3600 meters) per segment. See also EtherChannel and IEEE 802.3.
|100BaseFX||A 100-Mbps baseband Fast Ethernet specification using two strands of multimode
fiber-optic cable per link. To guarantee proper signal timing, a 100BaseFX link
cannot exceed 1312 feet (400 meters) in length. Based on the IEEE 802.3 standard.
See also 100BaseX, Fast Ethernet, and IEEE 802.3.
|100BaseT||100-Mbps baseband Fast Ethernet specification using UTP wiring. Like the 10BaseT
technology on which it is based, 100BaseT sends link pulses over the network
segment when no traffic is present. However, these link pulses contain more
information than those used in 10BaseT. Based on the IEEE 802.3 standard. See also
10BaseT, Fast Ethernet, and IEEE 802.3.
|100BaseT4||100-Mbps baseband Fast Ethernet specification using four pairs of Categories 3, 4, or
5 UTP wiring. To guarantee the proper signal timing, a 100BaseT4 segment cannot
exceed 328 feet (100 meters) in length. Based on the IEEE 802.3 standard. See also
Fast Ethernet and IEEE 802.3.
|100BaseTX||100-Mbps baseband Fast Ethernet specification using two pairs of either UTP or STP
wiring. The first pair of wires receives data; the second transmits data. To guarantee
the proper signal timing, a 100BaseTX segment cannot exceed 328 feet (100 meters)
in length. Based on the IEEE 802.3 standard. See also 100BaseX, Fast Ethernet, and
|100BaseX||100-Mbps baseband Fast Ethernet specification that refers to the 100BaseFX and
100BaseTX standards for Fast Ethernet over fiber-optic cabling. Based on the
IEEE 802.3 standard. See also 100BaseFX, 100BaseTX, Fast Ethernet, and IEEE
|100VG-AnyLAN||100-Mbps Fast Ethernet and Token Ring media technology using four pairs of
Categories 3, 4, or 5 UTP cabling. This high-speed transport technology, developed
by Hewlett-Packard, can operate on existing 10BaseT Ethernet networks. Based on
the IEEE 802.12 standard. See also IEEE 802.12.
|1000Base-F||A 1-Gbps IEEE standard for Ethernet LANs.
|2B1Q||2 binary 1 quaternary. An encoding scheme that provides a 2 bits per baud, 80-kbaud
per second, 160-kbps transfer rate. The most common signaling method on ISDN U
interfaces. The 1988 ANSI spec T1.601 defines this protocol in detail.
|2G mobile network||second generation mobile network. Refers generically to a category of mobile
wireless networks and services that implement digital technology. GSM is an
example of a 2G mobile network standard.
|2G+ mobile network||second generation plus mobile network. Refers generically to a category of mobile
wireless networks that support higher data rates than 2G mobile networks. GPRS is
an example of a 2G+ mobile network standard.
|24th channel signaling||See 2G mobile network.
|3G mobile network||third generation mobile network. Refers generically to a category of next-generation
mobile networks, such as UMTS and IMT-2000.
|370 block mux channel||See block multiplexer channel.
|4B/5B local fiber||4-byte/5-byte local fiber. Fiber channel physical media used for FDDI and ATM.
Supports speeds up to 100 Mbps over multimode fiber. See also TAXI 4B/5B.
|6BONE||The Internets experimental IPv6 network.
|8B/10B local fiber||8-byte/10-byte local fiber. Fiber channel physical media that supports speeds up to
149.76 Mbps over multimode fiber.
|802.x||A set of IEEE standards for the definition of LAN protocols.
|822||The short form of RFC 822. Refers to the format of Internet-style e-mail as defined
in RFC 822.
|1822||A historic term that refers to the original ARPANET host-to-IMP interface. The
specifications are in BBN report 1822. See also host and IMP.
|A&B bit signaling||Procedure used in T1 transmission facilities in which each of the 24 T1 subchannels
devotes 1 bit of every sixth frame to the carrying of supervisory signaling
information. Also called 24th channel signaling.
|A/D||analog to digital conversion.
|AAA||authentication, authorization, and accounting. Pronounced triple a.
|ATM adaptation layer (AAL)||ATM adaptation layer. Service-dependent sublayer of the data link layer. The AAL
accepts data from different applications and presents it to the ATM layer in the form
of 48-byte ATM payload segments. AALs consist of two sublayers: CS and SAR.
AALs differ on the basis of the source-destination timing used (CBR or VBR) and
whether they are used for connection-oriented or connectionless mode data transfer.
At present, the four types of AAL recommended by the ITU-T are AAL1, AAL2,
AAL3/4, and AAL5. See also AAL1, AAL2, AAL3/4, AAL5, ATM, ATM layer, CS, and
|ATM adaptation layer 1 (AAL1)||ATM adaptation layer. One of four AALs recommended by the ITU-T. AAL1 is used
for connection-oriented, delay-sensitive services requiring constant bit rates, such as
uncompressed video and other isochronous traffic. See also AAL.
|ATM adaptation layer 2 (AAL2)||ATM adaptation layer 2. One of four AALs recommended by the ITU-T. AAL2 is
used for connection-oriented services that support a variable bit rate, such as some
isochronous video and voice traffic. See also AAL.
|ATM adaptation layer 3/4 (AAL3/4)||ATM adaptation layer 3/4. One of four AALs (merged from two initially distinct
adaptation layers) recommended by the ITU-T. AAL3/4 supports both connectionless
and connection-oriented links but is used primarily for the transmission of SMDS
packets over ATM networks. See also AAL.
|ATM adaptation layer 5 (AAL5)||ATM adaptation layer 5. One of four AALs recommended by the ITU-T. AAL5
supports connection-oriented VBR services and is used predominantly for the
transfer of classical IP over ATM and LANE traffic. AAL5 uses SEAL and is the least
complex of the current AAL recommendations. It offers low bandwidth overhead and
simpler processing requirements in exchange for reduced bandwidth capacity and
error-recovery capability. See also AAL and SEAL.
|AppleTalk Address Resolution Protocol (AARP)||AppleTalk Address Resolution Protocol. A protocol in the AppleTalk protocol stack
that maps a data-link address to a network address.
|AARP probe packets||Packets transmitted by AARP that determine whether a randomly selected node ID is
being used by another node in a nonextended AppleTalk network. If the node ID is
not being used, the sending node uses that node ID. If the node ID is being used, the
sending node chooses a different ID and sends more AARP probe packets. See also
|ABCD signaling||4-bit telephony line signaling coding in which each letter represents 1 of the 4 bits.
This often is associated with CAS or robbed-bit signaling on a T1 or E1 telephony
|ABM||1. Asynchronous Balanced Mode. HDLC (and derivative protocol) communication
mode supporting peer-oriented, point-to-point communications between two stations,
where either station can initiate the transmission.
2. Accunet Bandwidth Manager.
|ABR||1. available bit rate. QoS class defined by the ATM Forum for ATM networks. ABR
is used for connections that do not require timing relationships between source and
destination. ABR provides no guarantees in terms of cell loss or delay, providing only
best-effort service. Traffic sources adjust their transmission rate in response to
information they receive describing the status of the network and its capability to
successfully deliver data. Compare with CBR, UBR, and VBR.
2. area border router. Router located on the border of one or more OSPF areas that
connects those areas to the backbone network. ABRs are considered members of both
the OSPF backbone and the attached areas. They therefore maintain routing tables
describing both the backbone topology and the topology of the other areas
|ABRD||automatic baud rate detection.
|ABS||application bridge server. Software module that allows the ICM to share the
application bridge interface from an Aspect ACD with other applications.
|Abstract Syntax Notation One (ASN.1)||Abstract Syntax Notation One. OSI language for describing data types independent
of particular computer structures and representation techniques. Described by ISO
International Standard 8824. See also BER, basic encoding rules.
|access device||The hardware component used in the signaling controller system: access server or
|access list||A list kept by routers to control access to or from the router for a number of services
(for example, to prevent packets with a certain IP address from leaving a particular
interface on the router).
|access method||1. Generally, the way in which network devices access the network medium.
2. Software within an SNA processor that controls the flow of information through a
|access server||Communications processor that connects asynchronous devices to a LAN or WAN
through network and terminal emulation software. Performs both synchronous and
asynchronous routing of supported protocols. Sometimes called a network access
server. See also communication server.
|access unit (AU)||access unit. A device that provides ISDN access to PSNs. See also PSN.
|Access-Accept||Response packet from the RADIUS server notifying the access server that the user is
authenticated. This packet contains the user profile, which defines the specific AAA
functions assigned to the user.
|Access-Challenge||Response packet from the RADIUS server requesting that the user supply additional
information before being authenticated.
|Access-Request||Request packet sent to the RADIUS server by the access server requesting
authentication of the user.
|accounting management||One of five categories of network management defined by ISO for the management
of OSI networks. Accounting management subsystems are responsible for collecting
network data relating to resource usage. See also configuration management, fault
management, performance management, and security management.
|ACD||1. automatic call distributor. Programmable device at a call center that routes
incoming calls to targets within that call center. After the ICM determines the target
for a call, the call is sent to the ACD associated with that target. The ACD must then
complete the routing as determined by the ICM.
2. automatic call distribution. Device or service that automatically reroutes calls to
customers in geographically distributed locations served by the same CO. See also
|ACELP||algebraic code excited linear prediction.
|Advanced Communications Function (ACF)||Advanced Communications Function. A group of SNA products that provides
distributed processing and resource sharing. See also ACF.
|Advanced Communications Function/Network Control Program (ACF/NCP)||Advanced Communications Function/Network Control Program. The primary SNA
NCP. ACF/NCP resides in the communications controller and interfaces with the
SNA access method in the host processor to control network communications. See
also ACF and NCP.
|acknowledgment (ACK)||Notification sent from one network device to another to acknowledge that some event
occurred (for example, the receipt of a message). Sometimes abbreviated ACK.
Compare to NAK.
|alarm cutoff (ACO)||alarm cutoff. Feature that allows the manual silencing of the office audible alarm.
(Subsequent new alarm conditions might reactivate the audible alarm.)
|ACOM||Term used in G.165, General Characteristics of International Telephone
Connections and International Telephone Circuits: Echo Cancellers. ACOM is the
combined loss achieved by the echo canceller, which is the sum of the echo return
loss, echo return loss enhancement, and nonlinear processing loss for the call.
|ACR||allowed cell rate. A parameter defined by the ATM Forum for ATM traffic
management. ACR varies between the MCR and the PCR, and is controlled
dynamically using congestion control mechanisms. See also MCR and PCR.
|ACS||asynchronous communications server.
|association control service element (ACSE)||association control service element. The OSI convention used to establish, maintain,
or terminate a connection between two applications.
|Activation||The process of enabling a subscriber device for network access and privileges on
behalf of a registered account.
|active discovery packet||The type of packet used by PPPoE during the discovery stage.
|active hub||A multiported device that amplifies LAN transmission signals.
|active monitor||The device responsible for managing a Token Ring. A network node is selected to be
the active monitor if it has the highest MAC address on the ring. The active monitor
is responsible for such management tasks as ensuring that tokens are not lost, or that
frames do not circulate indefinitely. See also ring monitor and standby monitor.
|active nonvolatile memory (ANVM)||active nonvolatile memory. Memory that contains the software currently used by the
|ActiveX||Microsofts Windows-specific non-Java technique for writing applets. ActiveX
applets take considerably longer to download than the equivalent Java applets;
however, they more fully exploit the features of Windows 95. ActiveX sometimes is
said to be a superset of Java. See also applet and Java.
|ACU||automatic calling unit.
|ACUTA||Association of College and University Telecomm Administrators.
|AD||administrative domain. A group of hosts, routers, and networks operated and
managed by a single organization.
|adaptive differential pulse code modulation||See ADP.
|adaptive routing||See dynamic routing.
|ADC||analog to digital converter.
|ADCCP||Advanced Data Communications Control Protocol. ANSI standard bit-oriented data
link control protocol.
|Add Path request||A request made by the network to add a path using the Add Path packet, which
establishes a multi-hop path between two network nodes. Although the two nodes are
usually the source and destination nodes of a VWP, there are cases in which other
nodes might want to establish a path between them. Unlike the Restore Path request,
the Add Path request is never flooded; it is instead forwarded using information
carried in the path itself (source routing).
|add/drop multiplexer (ADM)||add/drop multiplexer. Digital multiplexing equipment that provides interfaces
between different signals in a network.
|address||آدرس||Data structure or logical convention used to identify a unique entity, such as a
particular process or a network device.
|address mapping||A technique that allows different protocols to interoperate by translating addresses
from one format to another. For example, when routing IP over X.25, the IP addresses
must be mapped to the X.25 addresses so that the IP packets can be transmitted by
the X.25 network. See also address resolution.
|address mask||A bit combination used to describe which part of an address refers to the network or
the subnet and which part refers to the host. Sometimes referred to simply as mask.
See also subnet mask.
|address resolution||Generally, a method for resolving differences between computer addressing schemes.
Address resolution usually specifies a method for mapping network layer (Layer 3)
addresses to data link layer (Layer 2) addresses. See also address mapping.
|Address Resolution Protocol (ARP)||Address Resolution Protocol. Internet protocol used to map an IP address to a MAC
address. Defined in RFC 826. Compare with RARP. See also proxy ARP.
|address translation gateway (ATG)||address translation gateway. Cisco DECnet routing software function that allows a
router to route multiple, independent DECnet networks and to establish a
user-specified address translation for selected nodes between networks.
|addressed call mode||A mode that permits control signals and commands to establish and terminate calls
in V.25bis. See also V.25bis.
|ADF||adapter description file.
|adjacency||A relationship formed between selected neighboring routers and end nodes for the
purpose of exchanging routing information. Adjacency is based upon the use of a
common media segment.
|adjacent channel||A channel or frequency that is directly above or below a specific channel or
|adjacent nodes||1. In SNA, nodes that are connected to a given node with no intervening nodes.
2. In DECnet and OSI, nodes that share a common network segment (in Ethernet,
FDDI, or Token Ring networks).
|ADMD||Administration Management Domain. X.400 Message Handling System public
carrier. The ADMDs in all countries worldwide together provide the X.400 backbone.
See also PRMD.
|administrative distance||Rating of the trustworthiness of a routing information source. Administrative
distance often is expressed as a numerical value between 0 and 255. The higher the
value, the lower the trustworthiness rating.
|Administrative Domain||See adapter.
|administrative weight||See AW and PTSP.
|administrator||The person who queries the User Registrar to analyze individual subscriber status and
problems and to generate aggregate statistics.
|admission control||See traffic profile.
|admissions confirmation||An RAS message sent as an admissions confirmation.
|ADP||automatic data processing.
|ADPCM||adaptive differential pulse code modulation. The process by which analog voice
samples are encoded into high-quality digital signals.
|ADSL||asymmetric digital subscriber line. One of four DSL technologies. ADSL is designed
to deliver more bandwidth downstream (from the central office to the customer site)
than upstream. Downstream rates range from 1.5 to 9 Mbps, whereas upstream
bandwidth ranges from 16 to 640 kbps. ADSL transmissions work at distances up to
18,000 feet (5,488 meters) over a single copper twisted pair. See also HDSL, SDSL,
|ADSP||AppleTalk Data Stream Protocol.
|ATM data service unit (ADSU)||ATMDSU. Terminal adapter used to access an ATMnetwork via an HSSI-compatible
device. See also DSU.
|ADTS||automated digital terminal system.
|Advanced CoS Management||advanced class of service management. Essential for delivering the required QoS to
all applications. Cisco switches contain per-VC queuing, per-VC rate scheduling,
multiple CoS queuing, and egress queuing. This enables network managers to refine
connections to meet specific application needs. Formerly called FairShare and
|Advanced Data Communications Control Protocol||See AEP.
|Advanced Intelligent Network (AIN)||Advanced Intelligent Network. In SS7, an expanded set of network services made
available to the user, and under user control, that requires improvement in network
switch architecture, signaling capabilities, and peripherals. See also SS7.
|Advanced Peer-to-Peer Networking (APPN)||Advanced Peer-to-Peer Networking. Enhancement to the original IBM SNA
architecture. APPN handles session establishment between peer nodes, dynamic
transparent route calculation, and traffic prioritization for APPC traffic. Compare
with APPN+. See also APPC.
|Advanced Program- to-Program Communication (APPN)||Advanced Program-to-Program Communication. IBM SNA system software that
allows high-speed communication between programs on different computers in a
distributed computing environment. APPC establishes and tears down connections
between communicating programs. It consists of two interfaces: programming and
data-exchange. The programming interface replies to requests from programs
requiring communication; the data-exchange interface establishes sessions between
programs. APPC runs on LU 6.2 devices. See also LU 6.2.
|Advanced Research Projects Agency (ARPANET)||Advanced Research Projects Agency Network. Landmark packet-switching network
established in 1969. ARPANET was developed in the 1970s by BBN and funded by
ARPA (and later DARPA). It eventually evolved into the Internet. The term
ARPANET was retired officially in 1990. See also ARPA, BBN, DARPA, and Internet.
|advanced voice busyout (AVBO)||advanced voice busyout. The local voice busyout feature that provides a way to busy
out a voice port or a DS0 group (time slot) if a state change is detected in a monitored
network interface (or interfaces). When a monitored interface changes to a specified
state, to out-of-service, or to in-service, the voice port presents a seized/busyout
condition to the attached PBX or other customer premises equipment (CPE). The
PBX or other CPE can then attempt to select an alternate route. AVBO adds the
following functionality to the local voice busyout feature:
For Voice over IP (VoIP), monitoring of links to remote, IP-addressable
interfaces by the use of a real time reporter (RTR).
Configuration by voice class to simplify and speed up the configuration of voice
busyout on multiple voice ports.
Local voice busyout is supported on analog and digital voice ports using
channel-associated signalling (CAS).
|advertising||The router process in which routing or service updates are sent at specified intervals
so that other routers on the network can maintain lists of usable routes.
|AppleTalk Echo Protocol (AEP)||AppleTalk Echo Protocol. Used to test the connectivity between two AppleTalk
nodes. One node sends a packet to another node and receives a duplicate, or echo, of
|alignment error rate monitor (AERM)||SS7 MTP 2 function that provides monitoring of link alignment errors.
|AFC||See admissions confirmation.
|AFCEA||Armed Forces Communications and Electronics Association.
|affinity||Requirements of an MPLS traffic engineering tunnel on the attributes of the links it
will cross. The tunnels affinity bits and affinity mask bits of the tunnel must match
the attribute bits of the various links carrying the tunnel.
|AFI||authority and format identifier. The part of an NSAP-format ATM address that
identifies the type and the format of the IDI portion of an ATM address. See also IDI
|AFNOR||Association Francaise de Normalisation.
|AppleTalk Filing Protocol (AFP)||AppleTalk Filing Protocol. Presentation-layer protocol that allows users to share data
files and application programs that reside on a file server. AFP supports AppleShare
and Mac OS File Sharing.
|AFS||Andrew File System.
|agent||1. Generally, software that processes queries and returns replies on behalf of an
2. In NMSs, a process that resides in all managed devices and reports the values of
specified variables to management stations.
|aggressive mode||The connection mode that eliminates several steps during IKE authentication
negotiation (phase 1) between two or more IPSec peers. Aggressive mode is faster
than main mode but not as secure.
|AH||Authentication Header. A security protocol that provides data authentication and
optional anti-replay services. AH is embedded in the data to be protected (a full IP
|AHT||average handle time. The average time it takes for calls to a service or a skill group
to be handled. Handle time includes talk time plus after-call work time.
|AI||1. ??? ??????||1. artificial intellegence.
2. access interface.
|AIM||asynchronous interface module.
|AIP||ATM Interface Processor. ATM network interface for Cisco 7000 series routers
designed to minimize performance bottlenecks at the UNI. The AIP supports AAL3/4
and AAL5. See also AAL3/4 and AAL5.
|Airline Control Protocol||Data link layer polled protocol that runs in full-duplex mode over synchronous serial
(V.24) lines and uses the binary-coded decimal (BCD) character set.
|Airline Product Set (ALPS)||airline product set. A tunneling mechanism that transports airline protocol data across
a Cisco router-based TCP/IP network to an X.25-attached mainframe. This feature
provides connectivity between agent set control units (ASCUs) and a mainframe host
that runs the airline reservation system database.
|airline protocol||Generic term that refers to the airline reservation system data and the protocols, such
as P1024B (ALC), P1024C (UTS), and MATIP, that transport the data between the
mainframe and the ASCUs.
|Airline X.25 (AX.25)||X.25 implementation based on a CCITT 1984 recommendation using permanent
virtual circuits (PVCs) only. There is one nonstandard aspect of this protocol: packets
can be sent with the m-bit set, but the size of the packet is less than the maximum
packet size for the virtual circuit.
|AIS||1. alarm indication signal. In a T1 transmission, an all-ones signal transmitted in lieu
of the normal signal to maintain transmission continuity and to indicate to the
receiving terminal that there is a transmission fault that is located either at, or
upstream from, the transmitting terminal. See also T1.
2. automatic intercept system.
|AIX||advanced interface executive.
|alarm||Notification that the traffic signal has degraded or failed or equipment is
malfunctioning. An SNMP message notifying an operator or an administrator of a
network problem. See also event and trap.
|alarm indication signal||See ALS.
|a-law||ITU-T companding standard used in the conversion between analog and digital
signals in PCM systems. A-law is used primarily in European telephone networks and
is similar to the North American mu-law standard. See also companding and mu-law.
|algorithm||Well-defined rule or process for arriving at a solution to a problem. In networking,
algorithms commonly are used to determine the best route for traffic from a particular
source to a particular destination.
|Alien Port Adapter||A dual-wide port adapter for the Cisco 7200 router. The Alien Port Adapter is
ABR-ready and supports traffic shaping.
|alignment error||In IEEE 802.3 networks, an error that occurs when the total number of bits of a
received frame is not divisible by eight. Alignment errors usually are caused by frame
damage due to collisions.
|A-link||SS7 access link. A dedicated SS7 signaling link not physically associated with any
particular link carrying traffic.
|allowed cell rate||See ACOM.
|all-rings explorer packet||See local explorer packet.
|all-routes explorer packet||An explorer packet that traverses an entire SRB network, following all possible paths
to a specific destination. Sometimes called all-rings explorer packet. See also
explorer packet, local explorer packet, and spanning explorer packet.
|at-least-once transaction (ALO transaction)||An ATP transaction in which the request is repeated until a response is received by
the requester or until a maximum retry count is reached. This recovery mechanism
ensures that the transaction request is executed at least once. See also ATP.
|ALPS circuit||A communication path across a TCP connection between a host reservation system
and an ASCU. When MATIP encapsulation is used on an ALPS circuit, it is
equivalent to a MATIP session.
|ALPS Tunneling Protocol (ATP)||ALPS Tunneling Protocol. A protocol used to transport ALPS data across a TCP/IP
network between an ALC/UTS router and an AX.25/EMTOX router. It consists of a
set of messages (or primitives) to activate and deactivate ALPS ATP circuits and to
|ALS||active line state.
|alternate mark inversion (AMI)||alternate mark inversion. Line-code type used on T1 and E1 circuits. In AMI, zeros
are represented by 01 during each bit cell, and ones are represented by 11 or 00,
alternately, during each bit cell. AMI requires that the sending device maintain ones
density. Ones density is not maintained independently of the data stream. Sometimes
called binary coded alternate mark inversion. Compare with bipolar 8-zero
substitution. See also ones density.
|amplitude modulation (AM)||amplitude modulation. A modulation technique whereby information is conveyed
through the amplitude of the carrier signal. Compare with FM and PAM. See also
|AMA||Automatic Messaging Accounting. In OSS, the automatic collection, recording, and
processing of information relating to calls for billing purposes.
|AMADNS||AMA Data Networking System. In OSS, the next generation (formerly Bellcore)
system for the collection and the transport of AMA data from central office switches
to a billing system. See also AMA.
|AMATPS||AMA Teleprocessing System. In OSS, the Bellcore legacy system for collecting and
transporting AMA data from central office switches to a billing system. The
AMATPS consists of an AMA transmitter and a collector. See also AMA.
|American National Standards Institute||See ANP.
|American Standard Code for Information Interchange (ASCII)||American Standard Code for Information Interchange. 8-bit code for character
representation (7 bits plus parity).
|amplitude||The maximum value of an analog waveform or a digital waveform. The magnitude or
strength of a varying waveform. Typically represented as a curve along the x-axis of
|AMRL||adjusted main ring lenth.
|analog signal||The representation of information with a continuously variable physical quantity,
such as voltage. Because of this constant changing of the wave shape with regard to
its passing a given point in time or space, an analog signal might have a virtually
indefinite number of states or values. This contrasts with a digital signal that is
expressed as a square wave and therefore has a very limited number of discrete states.
|analog transmission||Signal transmission over wires or through the air in which information is conveyed
through the variation of some combination of signal amplitude, frequency, and phase.
|ANI||automatic number identification. SS7 (signaling system 7) feature in which a series
of digits, either analog or digital, are included in the call, identifying the telephone
number of the calling device. In other words, ANI identifies the number of the calling
party. See also CLID.
|anonymous FTP||Allows a user to retrieve documents, files, programs, and other archived data from
anywhere on the Internet without having to establish a userid and password. By using
the special userid of anonymous, the network user bypasses local security checks and
can access publicly accessible files on the remote system. See also FTP.
|ANP||automatic numbering plan.
|ANSI||American National Standards Institute. A voluntary organization composed 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. See also IEC and ISO.
|ANSI X3T9.5||See X3T9.5.
|answer supervision template||The sequence of autonomous responses to the detection of specific signaling events
for outbound calls from the Cisco VCO/4K switch. See also inpulse rule, outpulse
|answer-mode||Specifies that the router should not attempt to initiate a trunk connection, but should
wait for an incoming call before establishing the trunk.
|antenna||A device for transmitting or receiving a radio frequency (RF). Antennas are designed
for specific and relatively tightly defined frequencies and are quite varied in design.
An antenna for a 2.5 GHz (MMDS) system does not work for a 28 GHz (LMDS)
|antenna gain||The measure of an antenna assembly performance relative to a theoretical antenna,
called an isotropic radiator (radiator is another term for antenna). Certain antenna
designs feature higher performance relative to vectors or frequencies.
|anti-replay||Security service where the receiver can reject old or duplicate packets in order to
protect itself against replay attacks. IPSec provides this optional service by use of a
sequence number combined with the use of data authentication.
|anycast||In ATM, an address that can be shared by multiple end systems. An anycast address
can be used to route a request to a node that provides a particular service.
|AOW||Asia and Oceania Workshop. One of the three regional OSI Implementors
Workshops. See also EWOS.
|AP||1. application process.
2. application processor.
|APA||all points addressable.
|APAD||asynchronous packet assembler/disassembler.
|APaRT||automated packet recognition/translation. Technology that allows a server to be
attached to CDDI or FDDI without requiring the reconfiguration of applications or
network protocols. APaRT recognizes specific data link layer encapsulation packet
types and, when these packet types are transferred from one medium to another,
translates them into the native format of the destination device.
|APC||adjacent point code. The point code of the next hop in the system for the bearer
channels; usually it is the STP (signal transfer point).
|APDU||application protocol data unit.
|application programming interface (API)||application program interface. The means by which an application program talks to
communications software. Standardized APIs allow application programs to be
developed independently of the underlying method of communication. A set of
standard software interrupts, calls, and data formats that computer application
programs use to initiate contact with other devices (for example, network services,
mainframe communications programs, or other program-to-program
communications). Typically, APIs make it easier for software developers to create the
links that an application needs to communicate with the operating system or with the
|APN||access point name. Identifies a PDN that is configured on and accessible from a
GGSN in a GPRS network.
|APNIC||Asia Pacific Network Information Center. Nonprofit Internet registry organization for
the Asia Pacific region. The other Internet registries are currently IANA, RIPE NCC,
|Apollo Domain||Proprietary network protocol suite developed by Apollo Computer for
communication on proprietary Apollo networks.
|applet||A small program, often used in the context of a Java-based program, that is compiled
and embedded in an HTML page. See also ActiveX and Java.
|AppleTalk||A series of communications protocols designed by Apple Computer consisting of two
phases. Phase 1, the earlier version, supports a single physical network that can have
only one network number and be in one zone. Phase 2 supports multiple logical
networks on a single physical network and allows networks to be in more than one
zone. See also zone.
|AppleTalk Remote Access (ARA)||AppleTalk Remote Access. A protocol that provides Macintosh users direct access to
information and resources at a remote AppleTalk site.
|AppleTalk Transaction Protocol (ATP)||AppleTalk Transaction Protocol. A transport-level protocol that provides a
loss-free transaction service between sockets. The service allows exchanges between
two socket clients in which one client requests the other to perform a particular task
and to report the results. ATP binds the request and the response together to ensure
the reliable exchange of request-response pairs.
|AppleTalk Update-Based Routing Protocol (AURP)||AppleTalk Update-Based Routing Protocol. A method of encapsulating AppleTalk
traffic in the header of a foreign protocol, allowing the connection of two or more
discontiguous AppleTalk internetworks through a foreign network (such as TCP/IP)
to form an AppleTalk WAN. This connection is called an AURP tunnel. In addition
to its encapsulation function, AURP maintains routing tables for the entire AppleTalk
WAN by exchanging routing information between exterior routers. See also AURP
and exterior router.
|AppleTalk zone||See zone.
|application||A program that performs a function directly for a user. FTP and Telnet clients are
examples of network applications.
|application layer||Layer 7 of the OSI reference model. This layer provides services to application
processes (such as e-mail, file transfer, and terminal emulation) that are outside 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 an agreement on the
procedures for error recovery and the control of data integrity. Corresponds roughly
with the transaction services layer in the SNA model. See also data-link layer,
network layer, physical layer, PQ, session layer, and transport layer.
|APPN+||Next-generation APPN that replaces the label-swapping routing algorithm with
source routing. Also called high-performance routing. See also APPN.
|automatic protection switching (APS)||automatic protection switching. A method that allows transmission equipment to
recover automatically from failures, such as a cut cable.
|APSB||automatic protection switching byte (failure-condition code).
|AR||Access Registrar. Provides RADIUS services to DOCSIS cable modems for the
deployment of high-speed data services in a one-way cable plant requiring
telco-return for upstream data.
|ARC||ATM Research Consortium.
|Archie||A system that provides lists of anonymous FTP archives. See also Gopher, WAIS, and
World Wide Web.
|architecture||The overall structure of a computer or communication system. The architecture
influences the capabilities and limitations of the system.
|Attached Resource Computer Network (ARCnet)||Attached Resource Computer Network. 2.5-Mbps token-bus LAN developed in the
late 1970s and early 1980s by Datapoint Corporation.
|area||A logical set of network segments (CLNS-, DECnet-, or OSPF-based) and their
attached devices. Areas usually are connected to other areas via routers, making up a
single autonomous system. See also autonomous system.
|ARIN||American Registry for Internet Numbers. A nonprofit organization established for the
purpose of administrating and registrating IP numbers to the geographical areas
currently managed by Network Solutions (InterNIC). Those areas include, but are not
limited to, North America, South America, South Africa, and the Caribbean.
|ARL||adjusted ring length.
|asynchronous response mode (ARM)||asynchronous response mode. HDLC communication mode involving one primary
station and at least one secondary station, where either the primary or one of the
secondary stations can initiate transmissions. See also primary station and secondary
|Advanced Research Projects Agency (ARPA)||Advanced Research Projects Agency. Research and development organization that is
part of DoD. ARPA is responsible for numerous technological advances in
communications and networking. ARPA evolved into DARPA, and then back into
ARPA again (in 1994). See also DARPA.
|automatic repeat request (ARQ)||automatic repeat request. A communication technique in which the receiving device
detects errors and requests retransmissions.
|ARU||alarm relay unit.
|autonomous system (AS)||A collection of networks under a common administration sharing a common routing
strategy. Autonomous systems are subdivided by areas. An autonomous system must
be assigned a unique 16-bit number by the IANA. Sometimes abbreviated as AS. See
also area and IANA.
|ASA||average speed of answer. Average answer wait time for calls to a service or a route.
|ASAM||ATM subscriber access multiplexer. A telephone central office multiplexer that
supports SDL ports over a wide range of network interfaces. An ASAM sends and
receives subscriber data (often Internet services) over existing copper telephone lines,
concentrating all traffic onto a single high-speed trunk for transport to the Internet or
the enterprise intranet. This device is similar to a DSLAM (different manufacturers
use different terms for similar devices).
|ASBR||autonomous system boundary router. ABR located between an OSPF autonomous
system and a non-OSPF network. ASBRs run both OSPF and another routing
protocol, such as RIP. ASBRs must reside in a nonstub OSPF area. See also ABR,
nonstub area, and OSPF.
|ASCU||agent-set control unit.
|ASD||automated software distribution.
|ASE||1. amplified spontaneous emissions. Noise that is added to an optical signal when it
is amplified. This noise (or ASE) accumulates and builds in optical spans that have
multiple optical amplifiers between regenerators.
2. application service element.
|ASI||ATM Service Interface.
|ASIC||application-specific integrated circuit.
|ASIST||Application Software Integration Support Tools. A set of C-language application
development tools designed to facilitate the creation of host-controlled applications
by Cisco VCO/4K customers.
|ASN||auxiliary signal network.
|ASP||1. AppleTalk Session Protocol. A protocol that uses ATP to provide session
establishment, maintenance, and teardown, as well as request sequencing. See also
2. Auxiliary signal path. In telecommunications, link between TransPaths that allows
them to exchange signaling information that is incompatible with the PSTN backbone
network; used to provide feature transparency.
|ASPI||advanced ssci programming interface.
|assigned numbers||RFC [STD2] documents the currently assigned values from several series of numbers
used in network protocol implementations. This RFC is updated periodically, and
current information can be obtained from the IANA. If you are developing a protocol
or an application that requires the use of a link, a socket, a port, a protocol, and so on,
contact the IANA to receive a number assignment. See also IANA and STD.
|associative memory||Memory that is accessed based on its contents, not on its memory address. Sometimes
called content addressable memory (CAM).
|automatic spanning tree (AST)||automatic spanning tree. A function that supports the automatic resolution of
spanning trees in SRB networks, providing a single path for spanning explorer frames
to traverse from a given node in the network to another. AST is based on the IEEE
802.1 standard. See also IEEE 802.1 and SRB.
|ASTA||Advanced Software Technology and Algorithms. Component of the HPCC program
intended to develop software and algorithms for implementation on
high-performance computer and communications systems. See also HPCC.
|async||Subset of tty.
|asynchronous time-division multiplexing (ATDM)||asynchronous time-division multiplexing. A method of sending information that
resembles normal TDM, except that time slots are allocated as needed rather than
preassigned to specific transmitters. Compare with FDM, statistical multiplexing, and
|Asynchronous Transfer Mode (ATM)||Asynchronous Transfer Mode. The international standard for cell relay in which
multiple service types (such as voice, video, or data) are conveyed in fixed-length
(53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby
reducing transit delays. ATM is designed to take advantage of high-speed
transmission media, such as E3, SONET, and T3.
|asynchronous transmission||Term describing digital signals that are transmitted without precise clocking. Such
signals generally have different frequencies and phase relationships. Asynchronous
transmissions usually encapsulate individual characters in control bits (called start
and stop bits) that designate the beginning and the end of each character. Compare
with isochronous transmission, plesiochronous transmission, and synchronous
|ATB||all trunks busy. The state of a trunk group when all trunks are in use. The trunk group
cannot accept any new inbound or outbound calls in this state. The ICM tracks the
amount of time during which all trunks in a trunk group are busy.
|ATCP||AppleTalk Control Protocol. The protocol that establishes and configures AppleTalk
over PPP, as defined in RFC 1378. See also PPP.
|ATM ARP server||A device that provides address-resolution services to LISs when running classical IP
over ATM. See also LIS.
|ATM edge LSR||A router that is connected to the ATM-LSR cloud through LSC-ATM interfaces. The
ATM edge LSR adds labels to unlabeled packets and strips labels from labeled
|ATM endpoint||The point in an ATM network where an ATM connection is initiated or terminated.
ATM endpoints include ATM-attached workstations, ATM-attached servers,
ATM-to-LAN switches, and ATM routers.
|ATM Forum||International organization jointly founded in 1991 by Cisco Systems,
NET/ADAPTIVE, Northern Telecom, and Sprint that develops and promotes
standards-based implementation agreements for ATM technology. The ATM Forum
expands on official standards developed by ANSI and ITU-T, and develops
implementation agreements in advance of official standards.
|ATM network interface card||ESP card that is used as the OC-3 interface to the BPXs BXM.
|ATM layer||Service-independent sublayer of the data link layer in an ATM network. The ATM
layer receives the 48-byte payload segments from the AAL and attaches a 5-byte
header to each, producing standard 53-byte ATM cells. These cells are passed to the
physical layer for transmission across the physical medium. See also AAL.
|ATM Lite||Entry-level port adapter (higher performance than the AIP) for Cisco 7500 and 7200
routers. The Cisco ATM Lite port adapter does not support traffic shaping or ABR.
|ATM management (ATMM)||ATM management. A process that runs on an ATM switch that controls VCI
translation and rate enforcement. See also ATM and VCD.
|ATM network||Traditional Cisco ATM network built around BPX switches.
|ATM NIC||See ATM network interface card.
|ATM service interface||See ASCU.
|ATM UNI||See UNI.
|ATM user-user connection||A connection created by the ATM layer to provide communication between two or
more ATM service users, such as ATMM processes. Such communication can be
unidirectional, using one VCC, or bidirectional, using two VCCs. See also ATM
layer, ATMM, and VCC.
|ATM-LSR||A label switch router with several LSC-ATM interfaces. The router forwards the cells
among these interfaces using labels carried in the VPI/VCI field of the cells.
|ATP||1. ALPS Tunneling Protocol. A protocol used to transport ALPS data across a TCP/IP
network between an ALC/UTS router and an AX.25/EMTOX router. It consists of a
set of messages (or primitives) to activate and deactivate ALPS ATP circuits and to
2. AppleTalk Transaction Protocol. A transport-level protocol that provides a
loss-free transaction service between sockets. The service allows exchanges between
two socket clients in which one client requests the other to perform a particular task
and to report the results. ATP binds the request and the response together to ensure
the reliable exchange of request-response pairs.
|attachment unit interface (AUI)||attachment unit interface. IEEE 802.3 interface between an MAU and a NIC. The
term AUI also can refer to the rear panel port to which an AUI cable might attach.
Also called transceiver cable. See also IEEE 802.3, MAU, and NIC.
|attenuation||Loss of communication signal energy.
|attribute||Form of information items provided by the X.500 Directory Service. The directory
information base consists of entries, each containing one or more attributes. Each
attribute consists of a type identifier together with one or more values.
|AUP||acceptable use policy. Many transit networks have policies that restrict the use to
which the network can be put. The enforcement of AUPs varies with the network.
|AURP tunnel||A connection created in an AURP WAN that functions as a single, virtual data link
between AppleTalk internetworks physically separated by a foreign network (a
TCP/IP network, for example). See also AURP.
|AUSM||ATM user service module.
|authentication||In security, the verification of the identity of a person or a process.
|authority zone||Associated with DNS, an authority zone is a section of the domain-name tree for
which one name server is the authority. See also DNS.
|authorization||The method for remote access control, including one-time authorization or
authorization for each service, per-user account list and profile, user group support,
and support of IP, IPX, ARA, and Telnet.
|Automated Packet Recognition||Translation
|automatic call reconnect||Feature permitting automatic call rerouting away from a failed trunk line.
|Automatic Routing Management||Formerly AutoRoute. The connection-oriented mechanism used in Cisco WAN
switches to provide connectivity across the network. Switches perform a connection
admission control (CAC) function on all types of connections in the network.
Distributed network intelligence enables the CAC function to route and reroute
connections automatically over optimal paths while guaranteeing the required QoS.
|autonomous confederation||A group of autonomous systems that rely on their own network reachability and
routing information more than they rely on that received from other autonomous
systems or confederations.
|autonomous switching||Feature on Cisco routers that provides faster packet processing by allowing the
ciscoBus to switch packets independently without interrupting the system processor.
|autonomous system boundary router||See ASAM.
|autoreconfiguration||The process performed by nodes within the failure domain of a Token Ring network.
Nodes automatically perform diagnostics in an attempt to reconfigure the network
around the failed areas. See also failure domain.
|availability||The amount of time that a telephone system or other device is operationalthat is,
how long it is processing telephone calls or other transactions. Availability is
represented as the ratio of the total time a device is operational during a given time
interval to the length of that interval. Compare with reliability.
|average rate||Average rate, in kilobits per second (kbps), at which a given virtual circuit can
|AVM||ATM voice multiplexer.
|AW||1. administrative weight. The value set by the network administrator to indicate the
desirability of a network link. One of four link metrics exchanged by PTSPs to
determine the available resources of an ATM network.
2. admin workstation. A personal computer used to monitor the handling of calls in
the ICM system. The AW also can be used to modify the system configuration or
|bearer channel (B channel)||Bearer channel. DS0 time slot that carries analog voice or digital data over ISDN. In ISDN, a full-duplex, 64-kbps channel used to send user data. Compare with D channel, E channel, and H channel.
|binary 8-zero substitution (B8ZS)||binary 8-zero substitution. Line-code type, used on T1 and E1 circuits, in which a special code is substituted whenever eight consecutive zeros are sent over the link. This code then is interpreted at the remote end of the connection. This technique guarantees ones density independent of the data stream. Sometimes called bipolar 8-zero substitution. Compare with AMI. See also ones density.
|back end||Node or software program that provides services to a front end. See also client, FRF.11, and server.
|back pressure||Propagation of network congestion information upstream through an internetwork.
|backbone||Part of a network that acts as the primary path for traffic that is most often sourced from, and destined for, other networks.
|backhaul||A scheme where telephony signalling is reliably transported from a gateway to a Media Gateway Controller across a packet-switched network.
|backhauling||A scheme, also called signal tunneling, where telephony signals are passed from a gateway to a separate control for processing. The gateway need not interpret the
|backoff||The (usually random) retransmission delay enforced by contentious MAC protocols
after a network node with data to transmit determines that the physical medium is
already in use.
|backplane||The physical connection between an interface processor or card and the data buses
and the power distribution buses inside a chassis.
|backward explicit congestion notification (BECN)||backward explicit congestion notification. Bit set by a Frame Relay network in
frames traveling in the opposite direction of frames encountering a congested path.
DTE receiving frames with the BECN bit set can request that higher-level protocols
take flow control action as appropriate. Compare with FE.
|backward indicator bit (BIB)||Part of an SS7 MSU that when toggled signals a negative acknowledgment by the
remote signaling point.
|backward learning||Algorithmic process used for routing traffic that surmises information by assuming
symmetrical network conditions. For example, if node A receives a packet from
node B through intermediate node C, the backward-learning routing algorithm
assumes that A can reach B through C optimally.
|backward sequence number (BSN)||Part of an SS7 MSU that acknowledges the receipt of signal units by the remote
signalling point. Contains the sequence number of the signal unit being
|BAF||Bellcore AMA Format. System of abstract syntax and semantics that supports coding
of AMA data into records.
|balanced configuration||In HDLC, a point-to-point network configuration with two combined stations.
|balanced, unbalanced (balun)||balanced, unbalanced. Device used for matching impedance between a balanced and
an unbalanced line, usually twisted-pair and coaxial cable.
|bandwidth||The difference between the highest and lowest frequencies available for network
signals. The term also is used to describe the rated throughput capacity of a given
network medium or protocol. The frequency range necessary to convey a signal
measured in units of hertz (Hz). For example, voice signals typically require
approximately 7 kHz of bandwidth and data traffic typically requires approximately
50 kHz of bandwidth.
|bandwidth allocation||See bandwidth reservation.
|bandwidth reservation||The process of assigning bandwidth to users and applications served by a network.
Involves assigning priority to different flows of traffic based on how critical and
delay-sensitive they are. This makes the best use of available bandwidth, and if the
network becomes congested, lower-priority traffic can be dropped. Sometimes called
bandwidth allocation. See also call leg.
|Banyan VINES||See VINES.
|Bay Area Regional Research Network (BARRNet)||Bay Area Regional Research Network. Regional network serving the San Francisco
Bay Area. The BARRNet backbone is composed of four University of California
campuses (Berkeley, Davis, Santa Cruz, and San Francisco), Stanford University,
Lawrence Livermore National Laboratory, and NASA Ames Research Center.
BARRNet is now part of BBN Planet. See also BBN Planet.
|baseband||Characteristic of a network technology where only one carrier frequency is used.
Ethernet is an example of a baseband network. Also called narrowband. Contrast with
|baseline report||Compares two similar time ranges in a report format. A baseline time range is
protected against purge action so that baseline data is available at report time. The
baseline time range can be 1 to 30 days
|bash||Bourne-again shell. Interactive UNIX shell based on the traditional Bourne shell, but
with increased functionality. See also root account.
|Basic Rate Interface (BRI)||Basic Rate Interface. ISDN interface composed of two B channels and one D channel
for circuit-switched communication of voice, video, and data. Compare with PRI. See
also BISDN, ISDN, and N-ISDN.
|Basic Research and Human Resources (BRHR)||Basic Research and Human Resources. Component of the HPCC program designed
to support research, training, and education in computer science, computer
engineering, and computational science. See also HPCC.
|Bolt, Beranek, and Newman, Inc. (BBN)||Bolt, Beranek, and Newman, Inc. High-technology company located in
Massachusetts that developed and maintained the ARPANET (and later, the Internet)
core gateway system. See also BBN Planet.
|BBN Planet||Subsidiary company of BBN that operates a nationwide Internet access network
composed in part by the former regional networks BARRNet, NEARNET, and
SURAnet. See also BARRNet, BBN, NEARNET, and SURAnet.
|Bc||committed burst. Negotiated tariff metric in Frame Relay internetworks. The
maximum amount of data (in bits) that a Frame Relay internetwork is committed to
accept and transmit at the CIR. See also Be and CIR.
|BCP||Best Current Practices. The newest subseries of RFCs that are written to describe
BCPs in the Internet. Rather than specifying a protocol, these documents specify the
best ways to use the protocols and the best ways to configure options to ensure
interoperability between various vendors products.
|BDCS||Broadband Digital Cross-Connect System. SONET DCS capable of cross-connecting
DS-3, STS-1 and STS-3c signals. See also DCS.
|Be||excess burst. Negotiated tariff metric in Frame Relay internetworks. The number of
bits that a Frame Relay internetwork attempts to transmit after Bc is accommodated.
Be data, in general, is delivered with a lower probability than Bc data because Be data
can be marked as DE by the network. See also Bc and DE.
|beacon||Frame from a Token Ring or FDDI device indicating a serious problem with the ring,
such as a broken cable. A beacon frame contains the address of the station assumed
to be down. See also failure domain.
|Because Its Time Network (BITNET)||Because Its Time Networking Services. Low-cost, low-speed academic network
consisting primarily of IBM mainframes and 9600-bps leased lines. BITNET is now
part of CREN. See also CREN.
|Bell Communications Research (Bellcore)||Bell Communications Research. Organization that performs research and
development on behalf of the RBOCs.
|Bell operating company (BOC)||Bell operating company. Twenty-two local phone companies formed by the breakup
of AT&T. See also RBOC.
|Bellman-Ford routing algorithm||See distance vector routing algorithm.
|BER||1. bit error rate. Ratio of received bits that contain errors.
2. basic encoding rules. Rules for encoding data units described in the ISO ASN.1
standard. See also ASN.1.
|Berkeley Internet Name Domain (BIND)||Berkeley Internet Name Domain. Implementation of DNS developed and distributed
by the University of California at Berkeley (United States). Many Internet hosts run
BIND, which is the ancestor of many commercial BIND implementations.
|Berkeley Standard Distribution (BSD)|| Berkeley Standard Distribution. A term used to describe any of a variety of
UNIX-type operating systems based on the UC Berkeley BSD operating system.
|bit error rate tester (BERT)||bit error rate tester. Device that determines the BER on a given communications
channel. See also BER (bit error rate).
|best-effort delivery||Describes a network system that does not use a sophisticated acknowledgment system
to guarantee reliable delivery of information.
|Border Gateway Protocol (BGP)||Border Gateway Protocol. Interdomain routing protocol that replaces EGP. BGP
exchanges reachability information with other BGP systems. It is defined by
RFC 1163. See also BGP4 and EGP.
|BGP4||BGP Version 4. Version 4 of the predominant interdomain routing protocol used on
the Internet. BGP4 supports CIDR and uses route aggregation mechanisms to reduce
the size of routing tables. See also BGP and CIDR.
|BIA||burned-in MAC address.
|BIC||International Telecommunication Union Telecommunication Standardization Sector
(ITU-T) standard that defines the protocols and procedures needed for establishing,
maintaining, and terminating broadband switched virtual connections between public
networks. Also abbreviated BICI.
|BICI||Broadband Inter-Carrier Interface. ITU-T standard that defines the protocols and
procedures needed for establishing, maintaining, and terminating broadband
switched virtual connections between public networks. See also BIC.
|bidirectional PIM (bidir-PIM)||A variant of the Protocol Independent Multicast (PIM) suite of routing protocols for
IP multicast. In PIM, packet traffic for a multicast group is routed according to the
rules of the mode configured for that multicast group.
|Bus Interface Gate Array (BIGA)||Bus Interface Gate Array. Technology that allows the Catalyst 5000 to receive and
transmit frames from its packet-switching memory to its MAC local buffer memory
without the intervention of the host processor.
|big-endian||Method of storing or transmitting data in which the most significant bit or byte is
presented first. Compare with little-endian.
|binary||Numbering system characterized by ones and zeros (1 = on, 0 = off).
|binary coded alternate mark inversion||See AMI.
|Binary Synchronous Communication Protocol (bisync)||Binary Synchronous Communication Protocol. Character-oriented data-link protocol
for applications. Contrast with Synchronous Data Link Control (SDLC).
|BinHex||Binary Hexadecimal. A method for converting binary files into ASCII for
transmission by applications, such as e-mail, that can handle only ASCII.
|bit interleaved parity (BIP)||bit interleaved parity. In ATM, a method used to monitor errors on a link. A check bit
or word is sent in the link overhead for the previous block or frame. Bit errors in the
payload then can be detected and reported as maintenance information.
|biphase coding||Bipolar coding scheme originally developed for use in Ethernet. Clocking
information is embedded into and recovered from the synchronous data stream
without the need for separate clocking leads. The biphase signal contains no direct
|bipolar||Electrical characteristic denoting a circuit with both negative and positive polarity.
Contrast with unipolar.
|bipolar violation (BPV)||bipolar violation. A one (1) in a bipolar signal that has the same polarity as the
preceding one. See also coding violation.
|Broadband ISDN (BISDN)||Broadband ISDN. ITU-T communication standards designed to handle
high-bandwidth applications, such as video. BISDN currently uses ATM technology
over SONET-based transmission circuits to provide data rates from 155 to 622 Mbps
and beyond. Contrast with N-ISDN. See also BRI, ISDN, and PRI.
|bit||Binary digit used in the binary numbering system. Can be 0 or 1.
|bit rate||Speed at which bits are transmitted, usually expressed in bits per second.
|BITNET III||Dial-up service providing connectivity for members of CREN. See also CREN.
|bit-oriented protocol||Class of data link layer communication protocols that can transmit frames regardless
of frame content. Unlike byte-oriented protocols, bit-oriented protocols provide
full-duplex operation and are more efficient and reliable. Compare with byte-oriented
|building integrated timing supply (BITS)||building integrated timing supply. A clock in a central office that supplies DS1 and/or
composite clock timing references to all synchronous network elements in that office.
|bits per second||Abbreviated bps. See also bit rate.
|black hole||Routing term for an area of the internetwork where packets enter, but do not emerge,
due to adverse conditions or poor system configuration within a portion of the
|block multiplexer channel||IBM-style channel that implements the FIPS-60 channel, a U.S. channel standard.
This channel also is referred to as OEMI channel and 370 block mux channel.
|block serial tunnel||See BSS.
|blocking||In a switching system, a condition in which no paths are available to complete a
circuit. The term also is used to describe a situation in which one activity cannot
begin until another is completed.
|blower||An internal cooling fan used in larger router and switch chassis.
|BLSR||bidirectional line switch ring. SONET ring architecture that provides working and
protection fibers between nodes. If the working fiber between nodes is cut, traffic is
routed automatically onto the protection fiber. See also SONET.
|BNC connector||The standard connector used to connect IEEE 802.3 10Base2 coaxial cable to an
|Broadband Network Interface (BNI)||Broadband Network Interface.
|Broadband Network Module (BNM)||Broadband Network Module.
|boundary network node (BNN)||boundary network node. In SNA terminology, a subarea node that provides boundary
function support for adjacent peripheral nodes. This support includes sequencing,
pacing, and address translation. Also called boundary node.
|break-out/break-in (BOBI)||break-out/break-in. VNS feature that allows interworking between Euro-ISDN
(ETSI) and other VNS-supported signaling variants, such as DPNSS and QSIG.
|boot helper||Minimum-function Cisco IOS image that serves only to boot the full-function,
operational Cisco IOS image. Also known as rxboot.
|boot programmable read-only memory (boot PROM)||boot programmable read-only memory. A chip mounted on a printed circuit board
used to provide executable boot instructions to a computer device.
|bootflash||Separate Flash memory device used primarily to store the Cisco IOS boot helper
image, operational Cisco IOS images, and system configuration information.
|Bootstrap Protocol (BOOTP)||Bootstrap Protocol. The protocol used by a network node to determine the IP address
of its Ethernet interfaces to affect network booting.
|border gateway||A router that communicates with routers in other autonomous systems.
|border node||Node in one zone that connects with one or more nodes in other zones.
|boundary function||Capability of SNA subarea nodes to provide protocol support for attached peripheral
nodes. Typically found in IBM 3745 devices.
|boundary node||See BNN.
|Bridge Protocol Data Unit (Bpdu)||Bridge Protocol Data Unit. Spanning-Tree Protocol hello packet that is sent out at
configurable intervals to exchange information among bridges in the network. See
|BPI||baseline privacy interface.
|bps||bits per second.
|BPX Service Node||Closely integrated BPX switch, AXIS interface shelf, and extended services
processor designed to support ATM and Frame Relay switched virtual circuits, as
well as traditional PVCs.
|BRA||basic rate access. Two 64 kbps B channels + one 16 kbps D channel (2B + D),
carrying user traffic and signaling information respectively to the user via twisted
pair local loop.
|BRF||bridge relay function.
|bridge||Device that connects and passes packets between two network segments that use the
same communications protocol. Bridges operate at the data link layer (Layer 2) of the
OSI reference model. In general, a bridge filters, forwards, or floods an incoming
frame based on the MAC address of that frame. See also relay.
|bridge forwarding||A process that uses entries in a filtering database to determine whether frames with a
given MAC destination address can be forwarded to a given port or ports. Described
in the IEEE 802.1 standard. See also IEEE 802.1.
|bridge group||A bridging feature that assigns network interfaces to a particular spanning-tree group.
Bridge groups can be compatible with the IEEE 802.1 or the DEC specification.
|bridge number||A number that identifies each bridge in an SRB LAN. Parallel bridges must have
different bridge numbers.
|bridge static filtering||The process in which a bridge maintains a filtering database consisting of static
entries. Each static entry equates a MAC destination address with a port that can
receive frames with this MAC destination address and a set of ports on which the
frames can be transmitted. Defined in the IEEE 802.1 standard. See also IEEE 802.1.
|bridge virtual interface (BVI)||Bridge Group Virtual Interface. Logical Layer 3only interface associated with a
bridge group when IRB is configured.
|bridge-group||A group of interfaces bridged together to emulate a multiport bridge.
|broadband||Describes facilities or services that operate at the DS3 rate and above. For example,
a Broadband DCS makes cross-connections at the DS3, STS-1, and STS-Nc levels.
Similarly, Broadband ISDN provides about 150 Mb/s per channel of usable
|broadband||1. Transmission system that multiplexes multiple independent signals onto one cable.
2. Telecommunications terminology: Any channel having a bandwidth greater than a
voice-grade channel (4 kHz).
3. LAN terminology: A coaxial cable on which analog signaling is used. An RF
system with a constant data rate at or above 1.5 Mbps. Also called wideband. Contrast
|broadband inter-carrier interface||See BIC.
|broadband switch module (BXM)||Broadband Switch Module. ATM port card for the Cisco BPX switch.
|broadcast||Data packet that are sent to all nodes on a network. Broadcasts are identified by a
broadcast address. Compare with multicast and unicast. See also broadcast.
|broadcast address||A special address reserved for sending a message to all stations. Generally, a
broadcast address is a MAC destination address of all ones. Compare with multicast
address and unicast address. See also broadcast.
|broadcast and unknown server (BUS)||broadcast and unknown server. Multicast server used in ELANs that is used to flood
traffic addressed to an unknown destination and to forward multicast and broadcast
traffic to the appropriate clients. See also ELAN.
|broadcast domain||Set of all devices that receive broadcast frames originating from any device within
the set. Broadcast domains typically are bounded by routers because routers do not
forward broadcast frames.
|broadcast search||The propagation of a search request to all network nodes if the location of a resource
is unknown to the requester. See also directed search.
|broadcast storm||An undesirable network event in which many broadcasts are sent simultaneously
across all network segments. A broadcast storm uses substantial network bandwidth
and, typically, causes network time-outs.
|brouter||Concatenation of bridge and router. Used to refer to devices that perform both
bridging and routing functions.
|browser||GUI-based hypertext client application, such as Internet Explorer, Mosaic, and
Netscape Navigator, used to access hypertext documents and other services located
on innumerable remote servers throughout the WWW and Internet. See also
hypertext, Internet, Mosaic, and WWW.
|BSC||1. binary synchronous communication. Character-oriented data link layer protocol
for half-duplex applications. A form of telecommunication line control that uses a
standard set of transmission control characters and control character sequences, for
the binary synchronous transmission of binary-coded data between stations.
2. base station controller. In wireless, provides the control functions and physical
links between the MSC and BTS in a GSM mobile wireless network. The BSC
controls the interface between the SGSN and the BTS in a GPRS network. The BSC
is a high-capacity telephony switch that provides handsoff functions and cell
configuration data, and controls radio frequency power levels in BTSs. The combined
functions of the BSC and the BTS are referred to as the BSS.
|BSS||base station subsystem. Refers to the radio-related functions provided by the BTS and
BSC in a GSM mobile wireless network.
|BSTUN||Block Serial Tunnel.
Note: Do not use bisync serial tunnel or BSC tunnel as synonyms.
|burst tolerance (BT)||burst tolerance. A parameter defined by the ATM Forum for ATM traffic
management. For VBR connections, BT determines the size of the maximum burst of
contiguous cells that can be transmitted. See also VBR.
|BTA||Basic Trading Area. An area or footprint in which an entity is licensed to transmit
their frequencies. BTAs were established by Rand McNally and are defined as county
lines. Rand McNally licensed their mapping data to the FCC for ease of designation
for site licenses.
|BTS||base transceiver station. A land-based station in a GSM mobile wireless network that
consists of transceivers and antennas, which handle the radio interface to a mobile
station. A BSC controls one or more BTSs. The combined functions of the BTS and
the BSC are referred to as the BSS.
|BTU||British thermal units.
|BTW||by the way. One of many short-hand phrases used in chat sessions and e-mail
conversations. See also IMHO.
|buffer||A storage area used for handling data in transit. Buffers are used in internetworking
to compensate for differences in processing speed between network devices. Bursts
of data can be stored in buffers until they can be handled by slower processing
devices. Sometimes referred to as a packet buffer.
|build||To create flat files that are ready for use by the signaling controller database.
|burst||In data communications, a sequence of signals counted as one unit in accordance with
some specific criterion or measure.
|bursty traffic||A data communications term referring to an uneven pattern of data transmission.
|bus||1. Common physical signal path composed of wires or other media across which
signals can be sent from one part of a computer to another. Sometimes called a
2. See bus topology.
|bus and tag channel||IBM channel, developed in the 1960s, incorporating copper multiwire technology.
Replaced by the ESCON channel. See also ESCON channel and parallel channel.
|bus topology||Linear LAN architecture in which transmissions from network stations propagate the
length of the medium and are received by all other stations. Compare with ring
topology, star topology, and tree topology.
|BX.25||AT&T implementation of X.25. See also X.25.
|bypass mode||The operating mode on FDDI and Token Ring networks in which an interface has
been removed from the ring.
|bypass relay||Allows a particular Token Ring interface to be shut down and thus effectively
removed from the ring.
|byte||A term used to refer to a series of consecutive binary digits that are operated upon as
a unit (for example, an 8-bit byte).
|byte reversal||The process of storing numeric data with the least-significant byte first. Used for
integers and addresses on devices with Intel microprocessors.
|byte-oriented protocol||A class of data-link communications protocols that use a specific character from the
user character set to delimit frames. These protocols largely have been replaced by
bit-oriented protocols. Compare with bit-oriented protocol.
|C/N||Difference in amplitude between the desired radio frequency (RF) carrier and the noise in a portion of the spectrum. See carrier-to-noise.
|CA||1. certification authority. Entity that issues digital certificates (especially X.509
certificates) and vouches for the binding between the data items in a certificate.
2. Telecommunications: call appearance.
|CA certificate||[Digital] certificate for one CA issued by another CA.
|cable||Transmission medium of copper wire or optical fiber wrapped in a protective cover.
|cable modem||Modulator-demodulator device that is placed at subscriber locations to convey data
communications on a cable television system.
|cable range||Range of network numbers that is valid for use by nodes on an extended AppleTalk
network. The cable range value can be a single network number or a contiguous
sequence of several network numbers. Node addresses are assigned based on the cable
|cable router||Modular chassis-based router optimized for data-over-CATV hybrid fiber-coaxial
|cable television (CATV)||cable television. A communication system where multiple channels of programming
material are transmitted to homes using broadband coaxial cable. Formerly called
Community Antenna Television.
|CAC||connection admission control. Set of actions taken by each ATM switch during
connection setup to determine whether a connections requested QoS will violate the
QoS guarantees for established connections. CAC also is used when routing a
connection request through an ATM network.
|caching||A form of replication in which information learned during a previous transaction is
used to process later transactions.
|CAF||controllable ATM fabric.
|cage||A piece of hardware into which cards are installed.
|calculated planning impairment factor||See ICPIF.
|California Education and Research Federation Network (CERFnet)||California Education and Research Federation Network. TCP/IP network, based in
Southern California, that connects hundreds of higher-education centers internationally
while also providing Internet access to subscribers. CERFnet was founded
in 1988 by the San Diego Supercomputer Center and General Atomics, and is funded
by the NSF.
|call||An attempted connection between a remote system and LAC, such as a telephone call
through the PSTN. An incoming or outgoing call that is established successfully
between a remote system and LAC results in a corresponding L2TP session within a
previously established tunnel between the LAC and the LNS.
|call admission precedence||An MPLS traffic engineering tunnel with a higher priority will, if necessary, preempt
an MPLS traffic engineering tunnel with a lower priority. Tunnels that are harder to
route are expected to have a higher priority and to be able to preempt tunnels that are
easier to route. The assumption is that a lower-priority tunnel can find another path.
|call agent||Intelligent entity in an IP telephony network that handles call control in an MGCP
model voice over IP network. Also known as a Media Gateway Controller (MGC).
|call detail record (CDR)||call detail record.
1. A record written to a database for use in postprocessing activities. CDR files
consist of several CDBs. These activities include many functions, but primarily are
billing and network analysis. Cisco CallManager writes CDR records to the SQL
database as calls are made in a manner consistent with the configuration of each
individual Cisco CallManager.
2. Used in the original telephony networks, and now extended to mobile wireless
network calls, the CDR contains billing information for charging purposes. In a GPRS
network, the charging gateway sends the billing information within a CDR to the
network service provider for that subscriber.
3. VNS record of voice or data SVCs, which includes calling and called numbers,
local and remote node names, data and time stamp, elapsed time, and Call Failure
4. WirelessUsed in the original telephony networks and now extended to mobile
wireless network calls. The CDR contains billing information for charging purposes.
In a GPRS network, the charging gateway sends the billing information within a CDR
to the network service provider for that subscriber.
|call leg||Discrete segment of a call connection. A call leg is a logical connection between the
router and either a telephony endpoint over a bearer channel, or another endpoint
using a session protocol.
|call priority||Priority assigned to each origination port in circuit-switched systems. This priority
defines the order in which calls are reconnected. Call priority also defines which calls
can or cannot be placed during a bandwidth reservation. See also bandwidth
|call reference value||call reference value. Number carried in all Q.931 (I.451) messages that provides an
identifier for each ISDN call.
|call setup time||The time required to establish a switched call between DTE devices.
|caller ID (CLID)||calling line ID. Information about the billing telephone number from which a call
originated. The CLID value might be the entire phone number, the area code, or the
area code plus the local exchange. Also known as Caller ID.
|calling line identification||See CLID.
|CAM||content-addressable memory. See associative memory. See also CAM means "Cisco Access Manager" as in the Cisco Systems Terms and Acronyms.
|Canadian Standards Association (CSA)||Canadian Standards Association. Canadian agency that certifies products that
conform to Canadian national safety standards.
|CAP||Competitive Access Provider. An independent company providing local
telecommunications services mainly to business customers in competition with an
areas BOC or IOC. Teleport and MFS are the two major CAPs operating in major
metropolitan areas in the United States. See also BOC and IOC.
|CAR||1. committed access rate. The CAR and DCAR (distributed CAR) services limit the
input or output transmission rate on an interface or subinterface based on a flexible
set of criteria.
2. Cisco Access Registrar. Provides RADIUS services to DOCSIS modems for the
deployment of high-speed data services in a one-way cable plant requiring
telco-return for upstream data.
|carrier||An electromagnetic wave or alternating current of a single frequency, suitable for
modulation by another, data-bearing signal. See also modulation.
|Carrier Detect (CD)||Carrier Detect. A signal that indicates whether an interface is active. Also, a signal
generated by a modem indicating that a call has been connected.
|Carrier Identification Code||See CIC.
|carrier sense multiple access collision detect||See CSI.
|CAS||channel associated signaling. The transmission of signaling information within the
voice channel. CAS signaling often is referred to as robbed-bit signaling because user
bandwidth is being robbed by the network for other purposes.
|Category 1 cabling||One of five grades of UTP cabling described in the EIA/TIA-586 standard. Category 1
cabling is used for telephone communications and is not suitable for transmitting
data. Compare with Category 2 cabling, Category 3 cabling, Category 4 cabling, and
Category 5 cabling. See also EIA/TIA-586 and UTP.
|Category 2 cabling||One of five grades of UTP cabling described in the EIA/TIA-586 standard. Category 2
cabling is capable of transmitting data at speeds up to 4 Mbps. Compare with
Category 1 cabling, Category 3 cabling, Category 4 cabling, and Category 5 cabling.
See also EIA/TIA-586 and UTP.
|Category 3 cabling||One of five grades of UTP cabling described in the EIA/TIA-586 standard. Category 3
cabling is used in 10BaseT networks and can transmit data at speeds up to 10 Mbps.
Compare with Category 1 cabling, Category 2 cabling, Category 4 cabling, and
Category 5 cabling. See also EIA/TIA-586 and UTP.
|Category 4 cabling||One of five grades of UTP cabling described in the EIA/TIA-586 standard. Category 4
cabling is used in Token Ring networks and can transmit data at speeds up to
16 Mbps. Compare with Category 1 cabling, Category 2 cabling, Category 3 cabling,
and Category 5 cabling. See also EIA/TIA-586 and UTP.
|Category 5 cabling||One of five grades of UTP cabling described in the EIA/TIA-586 standard. Category 5
cabling can transmit data at speeds up to 100 Mbps. Compare with Category 1
cabling, Category 2 cabling, Category 3 cabling, and Category 4 cabling. See also
EIA/TIA-586 and UTP.
|catenet||A network in which hosts are connected to diverse networks, which themselves are
connected with routers. The Internet is a prominent example of a catenet.
|cause codes||Code that indicates the reason for ISDN call failure or completion.
|Context-based Access Control (CBAC)||Context-based Access Control. Protocol that provides internal users with secure
access control for each application and for all traffic across network perimeters.
CBAC enhances security by scrutinizing both source and destination addresses and
by tracking each applications connection status.
|CBC||cipher block chaining. Prevents the problems associated with Electronic Codebook
(ECB), where every block of plain text maps to exactly one block of cipher text
by having each encrypted block XORed with the previous block of ciphertext. In this
way identical patterns in different messages are encrypted differently, depending
upon the difference in the previous data.
|Connectionless Broadband Data Service (CBDS)||Connectionless Broadband Data Service. European high-speed, packet-switched,
datagram-based WAN networking technology. Similar to SMDS. See also SMDS.
|Constant bit rate (CBR)||Connectionless Broadband Data Service. QoS class defined by the ATM Forum for ATM networks. CBR is used for connections that depend on precise clocking to ensure undistorted delivery.
Compare with ABR, UBR, and VBR.
|CBWFQ||class-based weighted fair queueing extends the standard WFQ functionality to
provide support for user-defined traffic classes.
|CC||1. country code. Part of a numbering plan.
2. VCScall context.
|CCB||call control block.
|CCIE||Cisco Certified Internetwork Expert.
|Consultative Committee for International Telegraph and Telephone (CCITT)||Consultative Committee for International Telegraph and Telephone. International
organization responsible for the development of communications standards. Now
called the ITU-T. See also ITU-T.
|CCN unit||continuous control node unit. Provides communication between the redundant sides
of the admin shelf.
|CCNA||Cisco Certified Network Associate.
|CCO||Cisco Connection Online. The name of Cisco Systems external Web site.
|CCOT||cross office transfer time.
|CCR||commitment, concurrency, and recovery. OSI application service element used to
create atomic operations across distributed systems. Used primarily to implement
two-phase commit for transactions and nonstop operations.
|common channel signaling (CCS)||common channel signaling. Signaling system used in telephone networks that
separates signaling information from user data. A specified channel is exclusively
designated to carry signaling information for all other channels in the system. See
|CCSRC||Cisco Subscriber Registration Center. An integrated solution for data-over-cable
service providers to configure and manage broadband modems, and enable and
administer subscriber self-registration and activation.
|CCSS7||Common Channel Signaling System 7. Protocol used by the AT&T signaling network.
The ICMs NIC receives routing requests from the CCSS7 network and returns a
routing label to the CCSS7 network.
|CDB||call detail block. Consists of several Call Data Elements. The CDB is generated at a
Certain Point in Call (PIC). For example, a CDB is generated when the call is
answered, released, and so on.
|Copper Distributed Data Interface (CDDI)||Copper Distributed Data Interface. The implementation of FDDI protocols over STP
and UTP cabling. CDDI transmits over relatively short distances (about 90 yards
[100 meters]), providing data rates of 100 Mbps using a dual-ring architecture to
provide redundancy. Based on the ANSI TPPMD standard. Compare with FDDI.
|CDE||call detail element. A data element that includes a basic information field within a
billing record. Examples of a CDE are the calling number, the called number, and
|channel definition format (CDF)||channel definition format. Technology for push applications on the World Wide
Web. CDF is an application of XML. See also XML.
|CDMA||code division multiple access. A method of dividing a radio spectrum to be shared by
multiple users through the assignment of unique codes. CDMA implements spread
|CDP||Cisco Discovery Protocol. Media- and protocol-independent device-discovery
protocol that runs on all Cisco-manufactured equipment, including routers, access
servers, bridges, and switches. Using CDP, a device can advertise its existence to
other devices and receive information about other devices on the same LAN or on the
remote side of aWAN. Runs on all media that support SNAP, including LANs, Frame
Relay, and ATM media.
|Cellular Digital Packet Data (CDPD)||Cellular Digital Packet Data. Open standard for two-way wireless data
communication over high-frequency cellular telephone channels. Allows data
transmissions between a remote cellular link and a NAP. Operates at 19.2 kbps.
|CD-ROM||compact disc read-only memory.
|CD-RW||compact disc read/write.
|cell delay variation (CDV)||cell delay variation. A component of cell transfer delay, which is induced by buffering
and cell scheduling. CDV is a QoS delay parameter associated with CBR and VBR
service. See also CBR and VBR.
|cell delay variation tolerance (CDVT)||cell delay variation tolerance. In ATM, a QoS parameter for managing traffic that is
specified when a connection is set up. In CBR transmissions, CDVT determines the
level of jitter that is tolerable for the data samples taken by the PCR. See also CBR
|CE router||customer edge router. A router that is part of a customer network and that interfaces
to a provider edge (PE) router.
|CED||caller-entered digits. Digits entered by a caller on a touch-tone phone in response to
prompts. Either a peripheral (ACD, PBX, or VRU) or the carrier network can prompt
|CEF||Cisco Express Forwarding.
|cell||The basic data unit for ATMswitching and multiplexing. Cells contain identifiers that
specify the data stream to which they belong. Each cell consists of a 5-byte header
and 48 bytes of payload. See also cell relay.
|cell loss priority (CLP)||cell loss priority. Field in the ATMcell header that determines the probability of a cell
being dropped if the network becomes congested. Cells with CLP = 0 are insured
traffic, which is unlikely to be dropped. Cells with CLP = 1 are best-effort traffic,
which might be dropped in congested conditions to free up resources to handle
|cell loss ratio (CLR)||cell loss ratio. In ATM, the ratio of discarded cells to cells that are transmitted
successfully. CLR can be set as a QoS parameter when a connection is set up.
|cell payload scrambling||A technique using an ATM switch to maintain framing on some medium-speed edge
and trunk interfaces.
|cell relay||Network technology based on the use of small, fixed-size packets, or cells. Because
cells are fixed-length, they can be processed and switched in hardware at high speeds.
Cell relay is the basis for many high-speed network protocols, including ATM, IEEE
802.6, and SMDS. See also cell.
|cell transfer delay (CTD)||cell transfer delay. In ATM, the elapsed time between a cell exit event at the source
UNI and the corresponding cell entry event at the destination UNI for a particular
connection. The CTD between the two points is the sum of the total inter-ATM node
transmission delay and the total ATM node processing delay.
|cells per second||Abbreviated cps.
|cellular radio||Technology that uses radio transmissions to access telephone-company networks.
Service is provided in a particular area by a low-power transmitter.
|CELP||code excited linear prediction compression. Compression algorithm used in low
bit-rate voice encoding. Used in ITU-T Recommendations G.728, G.729, G.723.1.
|CEN||European Committee for Standardization. CENs mission is to promote voluntary
technical harmonization in Europe in conjunction with worldwide bodies and its
partners in Europe. The organization works in partnership with CENELEC and ETSI
(European Telecommunications Standards Institute).
|CENELEC||Comite Europeen de Normalisation Electrotechnique. CENELEC is the European
Committee for Electrotechnical Standardization. It was set up in 1973 and was
officially recognised as the European Standards Organisation in its field by the
European Commission in Directive 83/189 EEC. CENELEC works with 40,000
technical experts from 19 EC and EFTA countries to publish standards for the
|central office (CO)||central office.The local telephone company office to which all local loops in a given
area connect and in which circuit switching of subscriber lines occurs.
|Centrex||LEC service that provides local switching applications similar to those provided by
an onsite PBX. With Centrex, there is no onsite switching; all customer connections
go back to the CO. See also CC and LEC.
|CEP||Certificate Enrollment Protocol. Certificate management protocol jointly developed
by Cisco Systems and VeriSign, Inc. CEP is an early implementation of Certificate
Request Syntax (CRS), a standard proposed to the Internet Engineering Task Force
(IETF). CEP specifies how a device communicates with a CA, including how to
retrieve the public key of the CA, how to enroll a device with the CA, and how to
retrieve a certificate revocation list (CRL). CEP uses Public Key Cryptography
Standard (PKCS) 7 and PKCS 10 as key component technologies. The public key
infrastructure working group (PKIX) of the IETF is working to standardize a protocol
for these functions, either CRS or an equivalent. When an IETF standard is stable,
Cisco will add support for it.
|Conférence Européenne des Postes et des Télécommunications (CEPT)||Conférence Européenne des Postes et des Télécommunications. Association of the
26 European PTTs that recommends communication specifications to the ITU-T.
|CER||cell error ratio. In ATM, the ratio of transmitted cells that have errors to the total cells
sent in a transmission for a specific period of time.
|CERN||European Laboratory for Particle Physics. Birthplace of the World Wide Web.
|CERT||Computer Emergency Response Team. Chartered to work with the Internet
community to facilitate its response to computer security events involving Internet
hosts, to take proactive steps to raise the communitys awareness of computer security
issues, and to conduct research targeted at improving the security of existing systems.
The U.S. CERT is based at Carnegie Mellon University in Pittsburgh. Regional
CERTs are, like NICs, springing up in different parts of the world.
|certificate||Digital representation of user or device attributes, including a public key, that is
signed with an authoritative private key.
|CES||circuit emulation service. Enables users to multiplex or to concentrate multiple circuit
emulation streams for voice and video with packet data on a single high-speed ATM
link without a separate ATM access multiplexer.
|CET||Cisco Encryption Technology. 40- and 56-bit Data Encryption Standard (DES)
network layer encryption available since Cisco IOS Software Release 11.2.
|CFRAD||See Cisco FRAD.
|Common Gateway Interface (CGI)||Common Gateway Interface. A set of rules that describe how a Web server
communicates with another application running on the same computer and how the
application (called a CGI program) communicates with the Web server. Any
application can be a CGI program if it handles input and output according to the CGI
|chaining||An SNA concept in which RUs are grouped together for the purpose of error recovery.
|Challenge Handshake Authentication Protocol (CHAP)||Challenge Handshake Authentication Protocol. Security feature supported on lines
using PPP encapsulation that prevents unauthorized access. CHAP does not itself
prevent unauthorized access, but merely identifies the remote end. The router or
access server then determines whether that user is allowed access. Compare with PAP.