Table of Contents

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

Glossary

10-Mbps baseband Ethernet specification for using two pairs of twisted-pair cabling (Category 3, 4, or 5): one pair for transmitting data and one pair for receiving data. 10BaseT, which is part of the IEEE 802.3 specification, has a distance limit of approximately 100 meters per segment.

100-Mbps baseband Fast Ethernet specification for unshielded twisted-pair wiring. Based on the IEEE 802.3 standard.

A

Authentication, authorization, and accounting.

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, whether they use CBR or BVR, and whether they are used for connection-oriented or connectionless mode data transfer. See AAL5.

ATM adaptation layer 5. One of four AALs recommended by the ITU-T, AAL5 supports connection-oriented, VBR services, and is used primarily for the transfer of classical IP over ATM and LANE traffic.

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.

Automatic protection switching. SONET switching mechanism that routes traffic from working lines to protect them in case of a line card failure or fiber cut.

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. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is used in high-speed transmission media such as E3, SONET, and T3.

B

The difference between the highest and lowest frequencies available for network signals. The term is also used to describe the rated throughput capacity of a given network medium or protocol.

Bell Communications Research, Inc. Organization that performs research and development on behalf of the RBOCs and sets telephony standards (in the United States).

Separate Flash memory device used primarily to store the IOS boot helper image, operational IOS images, and system configuration information.

Minimum-function IOS image that serves only to boot the full-function, operational IOS image. Also referred to as "rxboot."

Bootstrap protocol. Protocol used by a network node to determine the IP address of its Ethernet interfaces, so that network booting can proceed.

C

Cisco Connection Online.

Cisco 6400 universal access concentrator. An ATM-based multilayer switch/router optimized for aggregating and managing access shelves.

Cisco IOS software allows centralized, integrated, and automated installation and management of internetworks and ensures support for a wide variety of protocols, media, services, and platforms.

Command-line interface. An interface that allows you to interact with the operating system by entering commands and optional arguments. Compare with GUI.

Central Office. Local telephone company office to which all local loops in a given area connect and in which circuit switching of subscriber lines occurs.

D

Dynamic Host Configuration Protocol. Provides a mechanism for allocating IP addresses dynamically so that addresses can be reused when hosts no longer need them.

Direct memory access. DMA transfers data into memory at high speeds with no processor overhead.

Dialed number identification service. Method for delivery of automatic number identification that uses out-of-band signaling

Domain name server. The part of the distributed database system for resolving a fully qualified domain name into the four-part IP (Internet Protocol) number used to route communications across the Internet.

Dynamic random access (read/write) memory.

Digital signal level 3. Framing specification used for transmitting digital signals at 44.736-Mbps on a T3 facility.

Digital subscriber loop. A public network technology that delivers high bandwidth over conventional copper wiring at limited distances. There are four types of DSL: ADSL, HDSL, SDSL, and VDSL. All are provisioned via modem pairs, with one modem located at a Central Office and the other at the customer site. Because most DSL technologies don't use the whole bandwidth of the twisted pair, there is room left for a voice channel.

Data terminal equipment. Device at the user end of a user-network interface that serves as a data source, destination, or both. DTE includes such devices as computers, protocol translators, and multiplexers.

E

Enhanced high system availability. This processor redundancy scheme reduces switchover time by requiring that the redundant processor be running in hot standby mode.

Electronic Industries Association. Group that specifies electrical transmission standards. The EIA and TIA have developed numerous well-known communications standards, including EIA/TIA-232 and EIA/TIA-449. See also TIA.

Baseband LAN specification originated by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps. Ethernet is similar to the IEEE 802.3 series of standards. See also 10BaseT and Fast Ethernet.

European Telecommunications Standards Institute.

F

Any of a number of 100-Mbps Ethernet specifications. Fast Ethernet offers a speed ten times that of the 10BaseT Ethernet specification, while preserving frame format, MAC mechanisms, and MTU. Based on an extension of the IEEE 802.3 specification. See also 100BaseT.

File Transfer Protocol. The set of standards that allow you to exchange complete files across different computer hosts. Using an FTP client, you can search for files and retrieve them from software archives on the Internet.

Field-replaceable unit. Term applied to the Cisco 6400 components that can be replaced in the field, including the NLC, NSP, NRP, and PME units, plus the blower fans.

G

Graphical user interface. User environment that uses pictorial as well as textual representation of the input and output of applications and the data structure in which information is stored. Conventions such as buttons, icons, and windows are typical, and many actions are performed by means of a pointing device (such as a mouse).

H

A router or access server that terminates L2F tunnels and PPP sessions.

I

Internet Control Message Protocol. Network layer Internet protocol that reports errors and provides other information relevant to IP packet processing. Documented in RFC 792.

Interim Interswitch Signaling Protocol. Formerly known as PNNI Phase 0, IISP is an ATM signaling protocol for interswitch communication by means of manually configured prefix tables. In the Cisco 6400, the software image can be configured to use IISP (C6400-WI-M) or PNNI (C6400-WP-M) for signaling connections.

Incumbent Local Exchange Carrier. The traditional local telephone service provider in the United States.

Interim Local Management Interface. ATM specification for incorporating network-management capabilities into the ATM UNI.

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. Documented in RFC 791.

Suite used to send IP datagram packets between nodes on the Internet.

Integrated routing and bridging.

International Telecommunications Union Telecommunication Standardization Sector. International body that develops worldwide standards for telecommunications technologies. The ITU-T carries out the functions of the former CCITT.

L

Layer 2 Forwarding Protocol. Protocol that supports the creation of secure virtual private dial-up networks over the Internet.

Layer 2 Tunneling Protocol. Protocol allowing PPP sessions to be tunnelled across an arbitrary media to a home gateway at an ISP or corporation. The Cisco 6400 aggregates user PPP sessions into L2TP tunnels.

L2TP (or local) access concentrator. Aggregates user PPP sessions into L2TP tunnels for transport to upstream LNS.

Local exchange carrier. Local or regional telephone company that owns and operates a telephone network and the customer lines that connect to it.

L2TP Network Server. Device at the ISP or corporation terminating the L2TP tunnels and PPP sessions. May be an NRP or equivalent.

M

Media Access Control. Lower of the two sublayers of the data link layer defined by the IEEE. The MAC sublayer handles access to shared media.

Management Information Base. Database of network management information that is used and maintained by a network management protocol such as SNMP.

N

Network address server. An L2F access concentrator that aggregates user PPP sessions into L2F tunnels for transport to upstream home gateway.

Network Equipment Building Systems. A standard set of physical and electrical requirements for telecommunications equipment intended for installation in the telephone company Central Office environment. NEBS requirements are specified in various Bellcore documents.

Node line card. One of the component cards used in the Cisco 6400 UAC. These cards provide the interfaces for moving data into and out of the Cisco 6400 system. They can be used as either uplink or downlink interfaces. Different types of line cards support different transmission protocols and data rates.

Network Management Ethernet. The local area network used to control and manage equipment in a Central Office and branch locations. The NME connection on the Cisco 6400 is an RJ-45 connector for a 10BaseT port on the NSP module.

Node route processor. One of the component modules used in the Cisco 6400 UAC. This module is the Layer 3 element for the Cisco 6400 responsible for implementing the routing function.

Node switch processor. One of the component modules used in the Cisco 6400 UAC. This module is responsible for all ATM switching and control functions within the Cisco 6400.

Nonvolatile RAM. RAM that retains its contents when a unit is powered off.

O

Optical carrier. A series of physical protocols (OC-1, OC-2, OC-3, and so on), defined for SONET optical signal transmissions. OC signal levels put STS frames onto multimode fiber-optic lines at a variety of speeds. The base rate is 51.84 Mbps (OC-1). See also SONET, STS-1, and STS-3c.

P

Personal Computer Memory Card International Association. Refers to a standard used for credit-card sized computer peripherals. Type I devices are very thin memory cards: Type 2 devices include most modems and interfaces; and Type 3 devices are used for disk drives and thicker components.

Power entry module. The PEM converts the -48 VDC power voltage into the voltages used internally by the Cisco 6400. The Cisco 6400 is designed to operate on one or two PEM units.

Packet internet groper. ICMP echo message and its reply. Often used in IP networks to test whether a network device destination can be reached from the source.

1. Private Network-Network Interface. ATM Forum specification for distributing topology information between switches and clusters of switches that is used to compute paths through the network. The specification is based on well-known link-state routing techniques and includes a mechanism for automatic configuration in networks in which the address structure reflects the topology.

2. Private Network Node Interface. ATM Forum specification for signaling to establish point-to-point and point-to-multipoint connections across an ATM network. The protocol is based on the ATM Forum UNI specification with additional mechanisms for source routing, crankback, and alternate routing of call setup requests.

Point of presence. Physical location within a LATA where a long distance carrier or cellular provider interfaces with the network of the local exchange carrier (LEC), also called the local telephone company.

Point-to-Point Protocol. Provides host-to-network and switch-to-switch connections over synchronous and asynchronous circuits, allowing one or more user sessions to be tunnelled across a medium. Includes provisions for security and protocol negotiation.

Point-to-Point Protocol over Ethernet. Encapsulation of PPP packets over Ethernet that provides the ability to extend a PPP session from a remote access concentrator to an Ethernet attached host.

Permanent virtual circuit. PVCs save bandwidth associated with circuit establishment and
tear-down in situations where certain virtual circuits must exist all the time. Sometimes called a permanent virtual connection in ATM terminology.

Q

Quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability.

R

Remote Dial-In User Service. Database for authenticating dial-in connections and for tracking connection time.

Regional Bell operating company. One of the regional phone companies that resulted from the breakup of the old AT&T. The RBOCs are still primarily limited to providing local access, although this is changing.

ROM Monitor.

S

Segmentation and reassembly. One of the two sublayers of the AAL CPCS, responsible for dividing (at the source) and reaassembling (at the destination) the PDUs passed from the CS. The SAR sublayer takes the PDUs processed by the CS and, after dividing them into 48-byte pieces of payload data, passes them to the ATM layer for further processing.

Synchronous Digital Hierarchy. European standard that defines a set of rate and format standards that are transmitted using optical signals over fiber. SDH has a basic rate of 155.52 Mbps, designated as STM-1.

Single in-line memory module. Used for Flash internal memory in the Cisco 6400.

An optical fiber that provides a transmission medium for one primary light wave mode.

Serial Line Internet Protocol. A version of IP that runs over serial links, allowing IP communications over the administrative interface.

Switched Multimegabit Data Service. One type of B-ISDN (Broadband ISDN) service based on the SONET optical fiber network. It uses cell relay based on fixed-length cells.

Simple Network Management Protocol. Network management protocol used almost exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices, and to manage configurations, statistics collection, performance, and security. See also SNMP2.

SNMP Version 2. SNMP2 supports centralized as well as distributed network management strategies, and includes improvements in the SMI, protocol operations, management architecture, and security.

Synchronous Optical Network. A family of fiber-optic transmission rates from 51.84 Mbps to 13.22 Gbps, created to provide the flexibility needed to transport many digital signals with different capacities, and to provide a design standard for manufacturers. SONET is an optical interface standard that allows interworking of transmission products from multiple vendors.

Synchronous Transport Module level 1. One of a number of SDH formats that specifies the frame structure for the 155.52-Mbps lines used to carry ATM cells.

Synchronous Transport Signal level 1. Basic building block of SONET, operating at 51.84 Mbps.

Synchronous Transport Signal level 3, concatenated. SONET format that specifies the frame structure for the 155.52-Mbps lines used to carry ATM cells.

Switched virtual circuit. Virtual circuit that is dynamically established on demand and is torn down when transmission is complete. Called a switched virtual connection in ATM terminology.

T

Terminal Access Controller Access Control System. Authentication protocol that provides access authentication and related services. User passwords are administered in a central database rather than in individual routers, providing an easily scalable network security solution.

Abbreviation for telephone company.

Standard terminal emulation protocol in the TCP/IP protocol stack. Telnet is used for remote terminal connections, enabling users to log into remote systems and use resources as if they were connected to a local system.

Trivial File Transfer Protocol. Simplified version of FTP that allows files to be transferred from one computer to another over a network.

Telecommunications Industry Association. Organization that develops standards relating to telecommunications technologies. See also EIA.

Physical and logical connection between two switches across which network traffic travels. A backbone is composed of a number of trunks.

Architecture that is designed to provide the services necessary to implement any standard point-to-point encapsulation scheme.

U

Universal access concentrator.

User-Network Interface. ATM Forum specification that defines an interoperability standard for the interface between ATM-based products (a router or an ATM switch) located in a private network and the ATM switches located within the public carrier networks. Also used to describe similar connections in Frame Relay networks. UNI versions include UNI3.0, UNI3.1, and UNI4.0.

A network connection between the Cisco 6400 system chassis and a WAN. Also known as a trunk.

V

Virtual circuit. Logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (PVC) or switched (SVC). In ATM, a virtual circuit is sometimes called a virtual channel.

Virtual channel identifier. 16-bit field in the header of an ATM cell. The VCI, together with the VPI, is used to identify the next destination of a cell as it passes through a series of ATM switches.

Instance of a unique virtual interface that is created dynamically and exists temporarily. Virtual access interfaces can be created and configured differently by different applications, such as virtual profiles and virtual private dialup networks.Virtual access interfaces are cloned from virtual template interfaces.

A logical interface configured with generic configuration information for a specific purpose or configuration common to specific users, plus router-dependent information. The template takes the form of a list of Cisco IOS interface commands that are applied to virtual access interfaces, as needed.

Virtual Private Dial-Up Networking. A system that permits dial-in networks to exist remotely to home networks, while giving the appearance of being directly connected. VPDNs use L2TP and L2F to terminate the Layer 2 and higher parts of the network connection at the home gateway, instead of the NAS.

Virtual path identifier. An 8-bit field in the header of an ATM cell. The VPI, together with the VCI, is used to identify the next destination of a cell as it passes through a series of ATM switches. The function of the VPI is similar to that of the DLCI in Frame Relay.

W

Wide-area network. Data communications network that serves users across a broad geographic area and often uses transmission devices provided by common carriers.

A graphical user interface (GUI) application that communicates with the system by translating HTML pages into Cisco IOS commands.

X

Various types of digital subscriber lines. Examples include ADSL, HDSL, and VDSL.

Posted: Mon Nov 15 12:41:51 PST 1999
Copyright 1989-1999©Cisco Systems Inc.