GLOSSARY First Published: January 2, 2008 Last Updated: January 2, 2008 A ADM AFI ANSI ASCII ATM Add/drop multiplexer. Authority and format identifier. American National Standards Institute. American Standard Code for Information Interchange. 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. B BAI BCD BX.25 Backup Active Interface. Binary Coded Decimal. AT&T Bell Laboratories variation of the ITU X.25 standard. C CCITT CDR CE CLEC CLNP CMTS CO Consultative Committee for International Telegraph and Telephone. Call detail record, which is used to create a telephone bill. Customer edge router. Competitive local exchange carrier. Connectionless Network Protocol. The OSI network layer protocol that does not require a circuit to be established before data is transmitted. Centralized maintenance test system. Central office. GL-1
CPU CTS CUD Central processing unit. Clear To Send signal is used in EIA/TIA-232 communication to indicate to the modem that it can send data to the peer modem. This is the input signal. Usually, RTS output signal of the peer modem is connected to CTS and is used for flow control. Call User Data. D DCC DCE DCN DCS DFI DIS DLCI DNS DRM DSLAMs DSP DSR (RING) DTE DTR Data communications channel. Data communications equipment (EIA expansion); data circuit-terminating equipment (ITU-T expansion). Data communications network. Digital cross-connect system. Domain specific part format identifier. Designated Intermediate System. Data-link connection identifier. Domain Name System. Lucent Distinctive Remote Module. Digital subscriber line access multiplexers. A device that connects many digital subscriber lines to a network by multiplexing the DSL traffic onto one or more network trunk lines. Domain Specific Part. Data Set Ready signal is used in EIA/TIA-232 communication to indicate to the modem that the peer modem wants to dial in. This is the input signal and is typically connected to DTR output of the peer modem. Data terminal equipment. Data Terminal Ready signal is used to indicate to the peer modem that this modem wants to dial in to the peer modem. This is the output signal. E EB EDAS EIA/TIA Echo Back. Engineering Data Acquisition System. Electronic Industries Alliance/Telecommunications Industry Alliance. GL-2
EMM EOR ES ESH Element Mediation Module. End of record. End system. End System Hello. F FTAM File Transfer, Access, and Management. G GNE GRE GUI Gateway network element. A gateway refers to a special-purpose device that performs an application-layer conversion of information from one protocol stack to another. 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 internetwork. By connecting multiprotocol subnetworks in a single-protocol backbone environment, IP tunneling using GRE allows network expansion across a single-protocol backbone environment. Graphical user interface. I IDI IDP IECs IEEE IETF I-Frame IIH ILEC IS ISH IS-IS Initial domain identifier. Initial Domain Part. Inter-exchange carriers. Institute of Electrical and Electronics Engineers. Internet Engineering Task Force. Information Frame. IS-IS Hello message. Incumbent local exchange carrier. Intermediate System. Intermediate System Hello. Intermediate System-to-Intermediate System. OSI protocol that specifies how routers communicate with routers in different domains. GL-3
ISL ISO CLNS ISO DCC ISO/IEC ISO-IGRP ITU IXC Inter-Switch Link. Cisco-proprietary protocol that maintains VLAN information as traffic flows between switches and routers. International Standards Organization Connectionless Network Service. Data Country Code. International Organization for Standardization/International Electrotechnical Commission. Interior Gateway Routing Protocol developed by Cisco for ISO CLNS. International Telecommunication Union. Inter-exchange carriers. L LAPB LCI LCN LDB LDP LECs LSP LSR Link Access Procedure, Balanced. Data link layer protocol in the X.25 protocol stack. LAPB is a bit-oriented protocol derived from HDLC. Logical channel identifier. Logical channel number. Loop detection buffer. Label Distribution Protocol. Local exchange carriers. Line-state packet; link-state packet; label-switched path. Label/tag switch router, which is a P router. M MAC M-bit MIB modem MPLS Media Access Control. More data bit. Management Information Base. modulator-demodulator. Device that converts digital and analog signals. At the source, a modem converts digital signals to a form suitable for transmission over analog communication facilities. At the destination, the analog signals are returned to their digital form. Modems allow data to be transmitted over voice-grade telephone lines. Multiprotocol Label Switching. MPLS supports multiple transport protocols such as IP and IPX, and can be transported over multiple Layer 2 protocols such as Frame Relay, ATM, Ethernet, or FDDI. GL-4
MSC GSM MUX Global System for Mobile Telecommunications mobile switching center. Multiplexer. Equipment that enables several data streams to be sent over a single physical line. It is also a function by which one connection from an (ISO) layer is used to support more than one connection to the next higher layer. A device for combining several channels to be carried by one line or fiber. N NEBS NET NFM NMA NOC NSAP Network Equipment Building Systems. Network entity title. Network Fault Management. Network Management Application from Telcordia. Network operations center. Network service access point. O OAM OAM&P OCS OSI OSS Operation, Administration, and Maintenance. Operations, Administration, Maintenance, and Provisioning. Optical convergence switch. Open System Interconnection. Operations Support Systems. OSSI Operations support system interface (DOCSIS specification). P P PAD PDN PDUs PE Provider router located in the interior of a VPN network and performs label and tag switching. Packet assembler/disassembler. A service specified for X.25 networks and standardized by ITU-Recommendations X.3, X.28,. and X.29, which define a way for asynchronous character-mode terminals (DTE-Cs) to use a packet switching network. Public data network. Protocol data units. Provider edge router that sits on the MPLS/VPN edge and performs tag binding and removal on packets from and to the CE router. GL-5
PSTN PTT PVC Public switched telephone network. Post, Telephone, and Telegraph. Permanent virtual circuit. Q Q-bit Used in an X.25 frame to differentiate control frames from data frames. Cisco s RBP Q-bit solution identifies control frames and data frames in the RBP six-byte header. R RBOC RBP RC rotary group RR RTS Regional Bell operating company. Record Boundary Preservation. Recent Change. A group of one or more lines used for incoming PAD calls. The rotary group is chosen from the subaddress portion of the destination address. Subaddresses in a range from 1 to 99 are tied to rotaries. A subaddress of zero (or trailing zeros) is accepted by the router on the first available vty line. Route reflectors, which are used in BGP to reduce ibgp peer sessions. Ready To Send signal used in EIA/TIA-232 communication to indicate to the peer modem that it can send data. This is output signal. S SABM SARTS SCC SCID SDH SLA SLM SNMP SNPA Set Asynchronous Balance Mode. Switched Access Remote Test System. Specialized common carrier. System-called identifier. Synchronous Digital Hierarchy. Service-level agreement. Synchronous Line Module. 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. Subnetwork point of attachment. GL-6
SONET STUN subaddress SVC Synchronous Optical Network. A standard format for transporting a wide range of digital telecommunications services over optical fiber. SONET is characterized by standard line rates, optical interfaces, and signal formats. Serial tunnel. Router feature allowing two SDLC- or HDLC-compliant devices to connect to one another through an arbitrary multiprotocol topology using Cisco routers rather than through a direct serial link. X.121 addresses are composed of two subfields in a Call Request packet sent when initiating a session. The second subfield currently consists of a two-character numeric value referred to as a subaddress. Permissible subaddress values range from 0 to 99 and are padded with leading zeros when necessary. Following are examples of legal subaddresses: 00, 09, 10, and 99. Either a physical port number or a numeric value for a line is used as a subaddress for PAD connections. Switched virtual circuit. Virtual circuit that is dynamically established on demand and is torn down when transmission is complete. SVCs are used in situations where data transmission is sporadic. T TARP TCP/IP TDM TDMS telco TID Target Identifier Address Resolution Protocol. In OSS, a protocol that resolves a TL-1 TID to a CLNP address (NSAP). Transmission Control Protocol/Internet Protocol. Time-division multiplexing. Traffic Data Management System. Telephone company. Target identifier. TL1 Transaction Language 1. TMN TTL Telecommunications Management Network. Time-to-Live field. U UID URC User or unique identifier. Update remote cache. GL-7
V VC VLAN VRF vty Virtual circuit; virtual connections (XOT). 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). Virtual LAN. Group of devices on one or more LANs that are configured using management software so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible. A VPN routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router. Virtual terminal. X X.121 ITU-T standard that describes an addressing scheme used in X.25 networks. X.25 ITU-T standard that defines how connections between DTE and DCE are maintained for remote terminal access and computer communications in PDNs. X.25 specifies LAPB, a data link layer protocol, and Packet Level Protocol (PLP), a network layer protocol. X.28 ITU-T standard that defines the user interface for an X.25 PAD. All user-entered commands and responses by the PAD are defined by this standard. XOT X.25 over TCP. GL-8