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B


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.

BGP
Border Gateway Protocol - Interdomain routing protocol that replaces Exterior Gateway Protocol (EGP). BGP exchanges reachability information with other BGP systems. It is defined by RFC 1163.

BOOTP
Bootstrap Protocol - A protocol used by a network node to determine the IP address of its Ethernet interfaces, in order to affect network booting.

BRI
Basic Rate Interface

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C


CAR
Committed access rate - A tool for managing bandwidth by controlling transmission rates into the network when traffic is congested. Using CAR, the network operator allocates minimum and maximum bandwidth values to categories of traffic such as voice grade, premium IP data, best effort, and so on.

CAS
Channel Associated Signalling - CAS voice switching allows PBXs with T1 trunks the ability to have their voice calls routed over the company's Frame Relay/ATM data network.

CBAC
Context-Based Access Control - A method for managing different types of traffic on a single network. CBAC allows an intelligent network to recognize a given type of traffic and prioritize its movement over the network. For example, voice will have greater priority over data because voice is more sensitive to delays and dropouts.

CBWFQ
Class-Based Weighted Fair Queuing - Allows the user to define traffic classes based on customer-defined match criteria such as access control lists (ACLs), input interfaces, protocol, and quality-of-service (QoS) label. For example, a class might consist of a team working on a certain project or a class can be created for the important mission-critical applications; for example, enterprise resource planning (ERP). When the traffic classes have been defined, they can be assigned a bandwidth, queue limit, or drop policy such as Weighted Random Early Detection (WRED).

CCIE®
Cisco Certified Internetwork Expert

CCO
Cisco Connection Online

CDP
Cisco Discovery Protocol (CDP) - Used primarily to obtain protocol addresses of neighboring devices and discover the platform of those devices. CDP can also be used to show information about the interfaces the router uses. CDP is media and protocol independent, and runs on all Cisco manufactured equipment including routers, bridges, access servers, and switches.

CEF
Cisco Express Forwarding - Increases performance by adopting a new caching mechanism that optimizes Internet traffic and enhances network scalability.

CGMP
Cisco Group Management Protocol - A Cisco developed protocol that allows Catalyst Switches to take advantage of Internet Group Management Protocol (IGMP) information on Cisco routers to make Layer 2 Forwarding decisions. Cisco Group Management Protocol (CGMP) has to be configured both on the multicast routers and the Layer 2 switches. The net result is that with CGMP, IP multicast traffic is delivered only to those Catalyst Switch ports that are interested in the traffic. All other ports that have not explicitly requested the traffic will not receive it.

CHAP
Challenge Handshake Authentication Protocol - A security feature supported on lines using Point-to-Point Protocol (PPP) encapsulation that prevents unauthorized access. CHAP does not itself prevent unauthorized access; it merely identifies the remote end. The router or access server then determines whether that user is allowed access.

CIR
Committed information rate - The rate at which a Frame Relay network agrees to transfer information under normal conditions, averaged over a minimum increment of time. Measured in bits per second, CIR is one of the key negotiated tariff metrics.

CLI
Command-line interface - Interface that allows the user to interact with the operating system by entering commands and optional arguments.

CLNP
Connectionless Network Protocol

CODECS
Compression/decompression algorithms

CPU
Central Processing Unit - A central processing unit is an older term for processor and microprocessor, the central unit in a computer containing the logic circuitry that performs the instructions of a computer's programs.

CRTP
Compressed Real-Time Protocol - Compressed RTP (CRTP), or Real-Time Protocol (RTP) header compression, is a method for making the voice-over-IP (VoIP) packet headers smaller to regain some of the "lost" bandwidth. CRTP compresses the IP/UDP/RTP header in an RTP data packet from 40 bytes to approximately 2 to 5 bytes.

CSE
Customer Support Engineering

Cisco IOS Software
Cisco IOS Software, the leading and most widely deployed network system software, delivers intelligent network services on a flexible networking infrastructure that enables the rapid deployment of Internet applications.

Codec
Coder/decoder. A software algorithm used to compress/decompress speech or audio signals.

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D


DECnet
Digital Equipment Corporation Network - Group of communications products (including a protocol suite) developed and supported by Digital Equipment Corporation.

DES
Data Encryption Standard - Standard cryptographic algorithm for virtual private networks (VPNs).

DFP
Dynamic Feedback Protocol - The protocol that allows servers to provide input into IP load-balancing decisions. Input includes the level of CPU utilization, the application, and the identity of the user.

DHCP
Dynamic Host Configuration Protocol - A protocol that allows a server to dynamically assign IP addresses to nodes (workstations) on the fly so that addresses can be reused when hosts no longer need them.

DID
Direct Inward Dialing

DISL
Dynamic InterSwitch Link

DLSw+
Data-Link Switching Plus - Cisco implementation of the data-link switching (DLSw) standard for Systems Network Architecture (SNA) and NetBIOS traffic forwarding. DLSW+ goes beyond the standard to include the advanced features of the current method of bridging, and provides additional functionality to increase the overall scalability of data-link switching.

DM
Dense Mode

DSCP
Differentiated service code point - Six bits in the type-of-service (ToS) field.

DSL
Digital subscriber line - Another term denoting xDSL; a family of technologies transmitting digital information (and sometimes plain old telephone service [POTS]) over existing copper-wire pairs for limited distances or over fiber-optic cables. The "x" in xDSL stands for any number of letters denoting the xDSL family members, commonly ISDN DSL (IDSL), single-line DSL (SDSL), high-data-rate DSL (HDSL), asymmetric DSL (ADSL), and very-high-data-rate DSL (VDSL).

DiffServ
Differentiated Services

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E


E&M
Receive and transmit - E&M is a common trunk-signaling technique used on telephony switches and PBXs. The signaling and voice trunks in E&M are separated.

E1
Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 2.048 Mbps. E1 lines can be leased for private use from common carriers.

ED
Early Deployment

EGP
Exterior Gateway Protocol

EIGRP
Enhanced Interior Gateway Routing Protocol - Advanced version of Interior Gateway Routing Protocol (IGRP) developed by Cisco. Provides superior convergence properties and operating efficiency, and combines the advantages of link-state protocols with those of distance-vector protocols.

EOL
End of Life

EOS
End of Sales

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F


F-SSRP
Fast Simple Server Redundancy Protocol

FCS
First Commercial Shipment

FIB
Forwarding Information Base

FRF.11
Frame Relay Fragmentation.11 - FRF.11-based voice over Frame Relay (VoFR) allows for vendor interoperability by specifying the frame format and coder types to use when transmitting voice traffic through a Frame Relay network. FRF.11 allows up to 255 subchannels to be multiplexed onto a single Frame Relay data-link connection identifier (DLCI).

FRF.12
Frame Relay Fragmentation.12 - Frame Relay Fragmentation based upon FRF.12 was developed in conjunction with FRF.11 (voice over Frame Relay) to allow long data frames to be fragmented into smaller pieces and interleaved with real-time voice frames or other delay-sensitive traffic. In this way, real-time traffic, such as voice, and non-real-time data traffic can be carried together on shared permanent-virtial-circuit (PVC) connections without causing excessive delay to the real-time traffic. FRF.12 can be used in conjunction with FRF.11 or it can be used independently. It enables end-to-end fragmentation on a per-PVC basis and allows fragment size to be configurable on a per-PVC basis. FRF.12 currently uses Weighted Fair Queuing (WFQ). Voice over Frame Relay frames cannot be fragmented, but voice-over-IP frames may be fragmented because they are treated as data frames at the Frame Relay level.

FRF.9
Frame Relay Fragmentation 9

FRTS
Frame Relay Traffic Shaping (FRTS) - Provides parameters that are useful for managing network traffic congestion. These include committed information rate (CIR), forward and backward explicit congestion notification (FECN/BECN), and the discard-eligibility (DE) bit.

FSO
Field Support Offices

FTP
File Transfer Protocol - An application protocol, part of the TCP/IP protocol stack, used for transferring files between network nodes.

FXO
Foreign exchange office

FXS
Foreign exchange station

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G


GD
General Deployment

GRE
Generic routing encapsulation - Tunneling protocol developed by Cisco that can encapsulate a wide variety of protocol packet types inside IP tunnels, creating a virtual point-to-point link to Cisco routers at remote points over an IP network.

GTS
Generic traffic shaping (GTS) - Provides a mechanism to control the traffic flow on a particular interface. It reduces outbound traffic flow to avoid congestion by constraining specified traffic to a particular bit rate (also known as the token bucket approach), while queuing bursts of the specified traffic. Thus, traffic adhering to a particular profile can be shaped to meet downstream requirements, eliminating bottlenecks in topologies with data-rate mismatches.

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H


H.323
An extension of International Telecommunication Union Telecommunication Standardization Sector (ITU-T) standard H.320; H.323 is a specification for transmitting audio, video, and data across an IP network, including the Internet.

HMAC
Hashing Message Authentication

HSRP
Hot Standby Router Protocol - Provides high network availability and transparent network topology changes. HSRP creates a hot standby router group with a lead router that services all packets sent to the hot standby address. Other routers in the group monitor the lead router, and if it fails, one of these standby routers inherits the lead position and the hot standby address.

HTTP
Hypertext Transfer Protocol

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I


IEEE
Institute of Electrical and Electronics Engineers - Engineers professional organization whose activities include the development of communications and network standards. IEEE LAN standards are the predominant LAN standards today.

IETF
Internet Engineering Task Force - A task force consisting of over 80 working groups responsible for developing Internet standards.

IGMP
Internet Group Management Protocol

IGMP Snooping
Internet Group Management Protocol Snooping - Requires the LAN switch to examine, or "snoop" some Layer 3 information in the Internet Group Management Protocol (IGMP) packets sent between the hosts and the router. When the switch hears the IGMP Host Report from a host for a particular multicast group, the switch adds the host port number to the associated multicast table entry. When the switch hears the IGMP Leave Group message from a host, it removes the host port from the table entry. Because IGMP control messages are transmitted as multicast packets, they are indistinguishable from multicast data at Layer 2. A switch running IGMP snooping must examine every multicast data packet to see if it contains any pertinent IGMP control information.

IGP
Interior Gateway Protocol

IGPM
Group Management Protocol

IGRP
Interior Gateway Routing Protocol

IMA
Inverse Multiplexing over ATM

IP
Internet Protocol - Network-layer protocol in the TCP/IP stack offering a connectionless internetwork service. IP provides features for addressing, type of service specification, fragmentation and reassembly, and security.

IPCP
IP Control Protocol - A protocol for transporting IP traffic over a Point-to-Point Protocol (PPP) connection.

IPSec
IP Security

IPX
Internet Packet Exchange - NetWare network-layer (Layer 3) protocol used for transferring data from servers to workstations.

IPv4
Internet Protocol Version 4

IPv6
IP Version 6

ISDN
Integrated Services Digital Network - A communication protocol, offered by telephone companies, that permits telephone networks to carry data, voice, and other source traffic.

ISMS
Implement Supply-Chain Management Systems

ISP
Internet Service Provider

IntServ
Integrated Services

Ipng
Internet Protocol v6

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L


L2F
Layer 2 Forwarding - A protocol that supports the creation of secure virtual private dialup networks (VPDNs) over the Internet.

L2TP
Layer 2 Tunneling Protocol - This Internet Engineering Task Force standard (RFC 2661) is a means of providing secure, high-priority, temporary paths through the Internet.

LAN
Local Area Network

LFI
Link fragmentation and interleaving (LFI) - Reduces delay and jitter on slower-speed links by breaking up large datagrams and interleaving low-delay traffic packets with the resulting smaller packets.

LLQ
Low--latency queuing (LLQ) - Brings strict priority queuing to Class-Based Weighted Fair Queuing (CBWFQ). Strict priority queuing allows delay-sensitive data such as voice to be de-queued and sent first (before packets in other queues are de-queued), giving delay-sensitive data preferential treatment over other traffic.

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M


MCM
Multimedia Conference Manager

MD5
Message Digest 5

MDRR
Modified Deficit Round Robin (MDRR) - A variant of Deficit Round Robin (DRR). Regular DRR selects packets from each virtual output queue in a regular round-robin mechanism, thus providing every class-of-service (CoS) queue equal scheduling into the fabric. In MDRR, all queues are also serviced in a round-robin fashion, with the exception of one of the queues.

MGCP
Media Gateway Control Protocol - A protocol designed to bridge between current circuit-based Public Switched Telephone Networks (PSTNs) and emerging IP technology-based networks.

MIB
Management Information Base - A database of network-management information that is used and maintained by a network-management protocol such as Simple Network Management Protocol (SNMP) or Common Management Information Protocol (CMIP).

MNLB
MultiNode Load Balancing - A forwarding agent that redirects traffic to the load balancer. MNLB distributes load-balancing decisions across any number of routers and switches, making possible the highest levels of availability of server applications.

MPLS
Multiprotocol Label Switching (MPLS) - Provides the mechanisms to perform "label switching," which is an innovative new technique for high-performance packet forwarding that assigns "labels" to packets for transport across packet- or cell-based networks. It is based on the concept of "label swapping," in which units of data (for example, a packet or a cell) carry a short, fixed-length label that tells switching nodes how to process the data.

MPPE
Microsoft Point-to-Point Encryption

MRM
Multicast Routing Monitor

MSFC
Multilayer Switch Feature Cards

MTU
Maximum transmission unit - Maximum packet size, in bytes, that a particular interface can handle.

MVS
Multiple Virtual Storage

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N


NAT
Network Address Translation (NAT) - Mechanism for reducing the need for globally unique IP addresses. NAT allows an organization with addresses that are not globally unique to connect to the Internet by translating those addresses into globally routable address space.

NBAR
Network-based application recognition (NBAR) - A new classification engine that can recognize a wide variety of application-level protocols, including HTTP via Universal Resource Locator/Multipurpose Internet Mail Extensions (URL/MIME) type and protocols that utilize dynamic port assignments. When the traffic is classified by NBAR, appropriate quality-of-service (QoS) policies can be applied to the traffic classes using existing Cisco IOS QoS features.

NFAS
Nonfacility Associated Signaling

NTP
Network Time Protocol

NetBIOS
Network Basic Input/Output System - An application programming interface (API) used by applications on an IBM LAN to request services from lower-level network processes. These services can include session establishment and termination, and information transfer.

Network Time Protocol
Network Time Protocol (NTP) - A protocol designed to time-synchronize a network of machines.

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O


OSI
Open Systems Interconnection

OSPF
Open Shortest Path First - Link-state, hierarchical Interior Gateway Protocol (IGP) routing algorithm proposed as a successor to Routing Information Protocol (RIP) in the Internet community. OSPF features include least-cost routing, multipath routing, and load balancing.

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P


PAT
Port Address Translation - A feature that lets you number a local-area network (LAN) with inside local addresses and filter them through one globally routable IP address.

PBR
Policy-based routing - Routing scheme that forwards packets to specific interfaces based on user-configured policies. Such policies might specify that traffic sent from a particular network should be forwarded out one interface, while all other traffic should be forwarded out another interface.

PBX
Private branch exchange - Digital or analog telephone switchboard located on the subscriber premises and used to connect private and public telephone networks.

PGM
Pragmatic General Multicast

PIM
Protocol Independent Multicast (PIM) - PIM gets its name from the fact that it is IP routing protocol independent. PIM can take advantage of whichever unicast routing protocols are used to populate the unicast routing table, including Enhanced Interior Gateway Routing Protocol (EIGRP), Open Shortest Path First (OSPF), Border Gateway Protocol (BGP), or static routes. PIM uses this unicast routing information to perform the multicast forwarding function; therefore, it is IP protocol independent. Although PIM is called a multicast routing protocol, it actually uses the unicast routing table to perform the Reverse-Path-Forwarding (RPF) check function instead of building up a completely unrelated multicast routing table. PIM does not send and receive multicast routing updates between routers like other routing protocols.

PPP
Point-to-Point Protocol - A protocol that provides router-to-router and host-to-network connections over synchronous and asynchronous circuits. A successor to Serial Line Internet Protocol (SLIP), which was designed to work with IP, PPP is designed to work with several network-layer protocols such as IP and Internetwork Packet Exchange (IPX).

PPTP
Point-to-Point Tunneling Protocol - A protocol that enables virtual private networking by providing secure remote access to corporate networks over the Internet.

PRI
Primary Rate Interface

PSTN
Public Switched Telephone Network

PVC
Permanent Virtual Circuits

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Q


QPPB
QoS Policy Propagation over BGP

QSIG
QSIG, a European Computer Manufacturers Association (ECMA) telephony signaling standard, provides an enabling technology to fuel the migration of legacy voice systems to intelligent "multiservice" networks. Originally standardized in the European Integrated Digital Services Network (ISDN) market, QSIG has quickly found worldwide acceptance for private and public applications.

QoS
Quality of service (QoS) - The goal of QoS is to provide better and more predictable network service by providing dedicated bandwidth, controlled jitter and latency, and improved loss characteristics. QoS achieves these goals by providing tools for managing network congestion, shaping network traffic, using expensive wide-area links more efficiently, and setting traffic policies across the network.

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R


RADIUS
Remote Authentication Dial-In User Service - A popular security system that has become an accepted standard. RADIUS, a client/server-based authentication software system, supports remote-access applications that allow an organization to maintain user profiles in a centralized database. This database resides on an authentication server that can be shared by multiple remote-access servers.

RBE
Route Bridge Encapsulation

RED
Random Early Detection - This class of algorithms is designed to avoid congestion in internetworks before it becomes a problem. RED works by monitoring traffic load at points in the network and stochastically discarding packets if the congestion begins to increase. The result of the drop is that the source detects the dropped traffic and slows its transmission. RED is designed to work primarily with TCP in IP internetwork environments.

RFC
Request for Comment - A document series used as the primary means for communicating information about the Internet, such as industry standards and protocol specifications. An RFC progresses through several development stages, under the control of the Internet Engineering Task Force (IETF), until it is finalized or discarded.

RIP v2
Routing Information Protocol

RMON
Remote Monitoring (RMON) - Identifies activity on individual nodes and allows one to monitor all nodes and their interaction on a LAN segment. Used in conjunction with the Simple Network Management Protocol (SNMP) agent in a router, RMON allows one to view both traffic that flows through the router and segment traffic not necessarily destined for the router.

RP
Rendezvous Point

RPF
Reverse Path Forwarding - A fundamental concept in multicast routing that enables routers to correctly forward multicast traffic down the distribution tree. RPF makes use of the existing unicast routing table to determine the upstream and downstream neighbors. A router will forward a multicast packet only if it is received on the upstream interface. This RPF check helps to guarantee that the distribution tree will be loop free.

RSVP
Resource Reservation Protocol (also known as Resource Reservation Setup Protocol) - A protocol that supports the reservation of resources across an IP network.

RTP
Real-Time Transport Protocol - A host-to-host protocol used for carrying newer multimedia application traffic, including packetized audio and video, over an IP network. RTP provides end-to-end network transport functions intended for applications transmitting real-time requirements, such as audio, video, or simulation data over multicast or unicast network services. RTP header compression increases efficiency for many of the newer voice-over-IP or multimedia applications that take advantage of Real-Time Transport Protocol (RTP), especially on slow links.

RTR
Response Time Reporter

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S


SAA
Service Assurance Agent or Cisco Service Assurance Agent - The Cisco IOS Software Service Assurance Agent (SAA) is an application-aware synthetic operations agent that monitors network performance by measuring key service-level-agreement (SLA) metrics such as response time, availability, jitter (interpacket delay variance), connect time, throughput, packet loss, and application performance.

SBM
Subnet Bandwidth Manager

SCM
Supply-Chain Management

SGCP
Simple Gateway Control Protocol - A protocol that Bellcore has created to address the concept of a network that would combine voice and data on a single packet-switched IP network.

SHA
Secure Hash Algorithm

SHA:Secure Hash Algorithm


SIP
Session Initiation Protocol

SKU
Stock Keeping Unit

SLA
Service-level agreement

SLB
Server load balancing - Allows the network administrator to define a virtual server to represent a group of real servers.

SM
Sparse Mode

SMTP
Simple Mail Transfer Protocol - The TCP/IP protocol governing e-mail transmissions and receptions.

SNA
Systems Network Architecture - A large, complex, feature-rich network architecture developed in the 1970s by IBM.

SNMP
Simple Network Management Protocol - SNMP was designed as the TCP stack network-management protocol. It can now manage virtually any network type and has been extended to include non-TCP devices such as 802.1 Ethernet bridges.

SONET
Synchronous Optical Network - A standard of fiber-optic transmission rates that allows interlocking or transmission products from multiple vendors.

SPF
Shortest Path First

SPT
Shortest Path Tree

SS7
Signaling System 7 - Used to perform out-of-band signaling in the Public Switched Telephone Network (PSTN).

SSG
Service Selection Gateway

SSM
Source Specific Multicast

SVC
Switched Virtual Circuits

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T


T1
Digital WAN carrier facility. T1, as used in the United States, is a 1.544-Mbps pulse-code-modulation (PCM) system that supports 24 voice frequency (VF) input channels. On each of the 24 VF channels, a device called a coder/decoder samples the analog input and converts the analog signal into a stream of digital signals called PCM words. A time-division multiplexer (TDM) cycles through the 24 channels and combines a group of 24 PCM words into a frame for transmission over the T1 line.

TAC
Technical Assistance Center

TACACS
Terminal Access Controller Access Control System - Authentication protocol, developed by the Defense Data Network (DDN) community, that provides remote-access authentication and related services, such as event logging.

TCP
Transmission Control Protocol

TCP/IP
Transmission Control Protocol/ Internet Protocol

TDM
Time Division Multiplexing

TED
Tunnel endpoint discovery

TOS
Type of service

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U


UDP
User Datagram Protocol - Connectionless transport-layer protocol in the TCP/IP protocol stack. UDP neither guarantees delivery nor does it require a connection. As a result it is lightweight and efficient, but all error processing and retransmission must be taken care of by the application program.

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V


VLSM
Variable Length Subnet Mask

VPDN
Virtual private dialup network - A special type of virtual private network (VPN) that reduces costs by extending a VPN across dialup lines.

VPN
Virtual private network - A private communications network that enables traffic to travel securely over a shared public network.

VTP
Virtual Terminal Protocol

VoATM
Voice over ATM

VoFR
Voice over Frame Relay

VoIP
Voice over IP - A software feature that enables a router to carry voice traffic (such as telephone calls and faxes) over an IP network.

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