<%@LANGUAGE="VBSCRIPT" CODEPAGE="1252"%> Satcom Services VSAT Services, Transponder Capacity, Communication
View our new website
Back to VPN

VPN Acronyms 

A  B  C  D  E  F  G  H  I  L  M  N  O  P  Q  R  S  T  U  V  W

Triple DES


Authentication, authorization, and accounting

ATM Adaptation Layer

ATM adaptation layer 5 - One of four ATM adaption layers (AALs) recommended by the ITU-T. AAL5 supports connection-oriented, variable-bit-rate (VBR) services, and is used predominantly for the transfer of classical IP over ATM and LAN emulation (LANE) traffic.

Access control list - A roster of users and groups of users kept by routers to control access to or from the router for a number of services.

- A proprietary local area network protocol developed by Apple Computer, Inc. for communication between Apple products (e.g. Macintosh) and other computers.

Autonomous System

Asynchronous Transfer Mode - International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. An internationally standardized implementation of cell-relay technology, ATM represents the first worldwide standard to be embraced by the computer, communications, and entertainment industry. ATM is a high-bandwidth, low-delay, connection-oriented, packet-like switching and multiplexing technique for data transmission that communicates all types of information (traditionally data, burst data, voice, video, image, and cell) over a common backbone using fixed cell lengths. ATM uses a 53-byte cell format that includes a 5-byte header and 48 bytes of payload. Because of the architecture, ATM has the capability to run from 45 Mbps using a DS3 to 2.5 Gbps using an OC-48.

Architecture for Voice and Video Integrated with Data

Up  Back to top


Backward explicit congestion notification - Bit set by a Frame Relay network in frames traveling in the opposite direction of frames encountering a congested path.

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.

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

Basic Rate Interface

Up  Back to top


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.

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.

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.

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).

Cisco Certified Internetwork Expert

Cisco Connection Online

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.

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

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.

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.

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.

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

Connectionless Network Protocol

Compression/decompression algorithms

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.

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.

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.

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

Up  Back to top


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

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

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.

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.

Direct Inward Dialing

Dynamic InterSwitch Link

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.

Dense Mode

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

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).

Differentiated Services

Up  Back to top


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.

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.

Early Deployment

Exterior Gateway Protocol

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.

End of Life

End of Sales

Up  Back to top


Fast Simple Server Redundancy Protocol

First Commercial Shipment

Forwarding Information Base

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).

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.

Frame Relay Fragmentation 9

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.

Field Support Offices

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

Foreign exchange office

Foreign exchange station

Up  Back to top


General Deployment

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.

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.

Up  Back to top


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.

Hashing Message Authentication

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.

Hypertext Transfer Protocol

Up  Back to top


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.

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

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.

Interior Gateway Protocol

Group Management Protocol

Interior Gateway Routing Protocol

Inverse Multiplexing over ATM

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.

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

IP Security

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

Internet Protocol Version 4

IP Version 6

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

Implement Supply-Chain Management Systems

Internet Service Provider

Integrated Services

Internet Protocol v6

Up  Back to top


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

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.

Local Area Network

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.

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.

Up  Back to top


Multimedia Conference Manager

Message Digest 5

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.

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

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).

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.

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.

Microsoft Point-to-Point Encryption

Multicast Routing Monitor

Multilayer Switch Feature Cards

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

Multiple Virtual Storage

Up  Back to top


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.

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.

Nonfacility Associated Signaling

Network Time Protocol

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.

Up  Back to top


Open Systems Interconnection

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.

Up  Back to top


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.

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.

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

Pragmatic General Multicast

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.

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).

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

Primary Rate Interface

Public Switched Telephone Network

Permanent Virtual Circuits

Up  Back to top


QoS Policy Propagation over BGP

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.

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.

Up  Back to top


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.

Route Bridge Encapsulation

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.

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

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.

Rendezvous Point

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.

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

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.

Response Time Reporter

Up  Back to top


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.

Subnet Bandwidth Manager

Supply-Chain Management

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.

Secure Hash Algorithm

SHA:Secure Hash Algorithm

Session Initiation Protocol

Stock Keeping Unit

Service-level agreement

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

Sparse Mode

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

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

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.

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

Shortest Path First

Shortest Path Tree

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

Service Selection Gateway

Source Specific Multicast

Switched Virtual Circuits

Up  Back to top


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.

Technical Assistance Center

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.

Transmission Control Protocol

Transmission Control Protocol/ Internet Protocol

Time Division Multiplexing

Tunnel endpoint discovery

Type of service

Up  Back to top


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.

Up  Back to top


Variable Length Subnet Mask

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

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

Virtual Terminal Protocol

Voice over ATM

Voice over Frame Relay

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

Up  Back to top


Wide Area Network

Web Cache Control Protocol - The protocol that provides for Web content caching and retrieval by using a cache engine. This process improves download time for the user and reduces bandwidth use on the network.

Weighted Fair Queuing - Ensures that queues do not starve for bandwidth, and that traffic gets predictable service. Low-volume traffic streams - which comprise most traffic-receive preferential service, transmitting their entire offered loads in a timely fashion. High-volume traffic streams share the remaining capacity proportionally between them.

Web Replication and Caching

Weighted Random Early Detection - Combines the capabilities of the Random Early Detection (RED) algorithm with IP Precedence. This combination provides for preferential traffic handling for higher-priority packets. It can selectively discard lower-priority traffic when the interface starts to get congested and provide differentiated performance characteristics for different classes of service.