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GLOSSARY
Symbols
See APS.
1+1 APS
10-Mbps baseband Ethernet specification using two pairs of twisted-pair cabling (Category 3, 4, or 5):
10BASE-T
one pair for transmitting data and the other for receiving data. 10BASE-T, which is part of the IEEE
802.3 specification, has a distance limit of approximately 328 feet (100 meters) per segment. See also
IEEE 802.3 and Ethernet.
100-Mbps baseband Fast Ethernet specification using UTP wiring. Like the 10BASE-T technology on
100BASE-T
which it is ba
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Glossary A 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:the convergence sublayer and the segmentation and reassembly sublayer. Four types of AAL recommended by the ITU-T are AAL1, AAL2, AAL3/4, and AAL5; the Cisco uBR10012 uses AAL5. Access list List kept by routers to control access to or from the router
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Glossary B Backplane The circuit board at the back of the chassis that all components plug into. It provides the physical connection between an interface processor or line card, and the data and power distribution buses inside a chassis. Bellcore Bell Communications Research. Former name of the organization that performs research and development on behalf of the Regional Bell Operating Companies (RBOCs). Bellcore is now called Telcordia. BER Bit error rate. The ratio of received bits that c
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Glossary 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. Command Line See CLI. Interface Console Data terminal equipment (DTE) through which commands are entered into a host. Critical alarm An alarm condition that might affect most or all subscribers that connect to the reporting node. To obtain more information about a problem, use the show facility-alarm status command. See als
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Glossary E 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. Compare with T1; see also DS1. Edge Services See ESR. Router See EMI. Electromagnetic interference Electrostatic See ESD. discharge Electromagnetic interference. Interference by electromagnetic signals that can cause reduced data EMI integrity and increased error rates on transmission channels. Electromagnetic
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Glossary Frame Relay Industry-standard, switched data link layer protocol that handles multiple virtual circuits using HDLC encapsulation between connected devices. Frame Relay is more efficient than X.25, the protocol for which it is generally considered a replacement. FRU Field replaceable unit. A component that can be removed from a network device and replaced in the field. Line cards, power modules, and fan modules are typically FRUs. G GBIC Gigabit Ethernet converter. An interface module
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Glossary IOS Internet Operating System. See Cisco IOS. 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. Defined in RFC 791. IP multicast Routing technique that allows IP traffic to be propagated from one source to a number of destinations or from many sources to many destinations. Rather than sending one packet to each
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Glossary M M13 Generic term for equipment that multiplexes DS1s into DS3s. Sometimes used to describe a specific DS3 multiplex format. Some standards use this term to describe a synchronous multiplexing format also know as SYNTRAN. In many cases M13 does not refer to the SYNTRAN format, but instead refers to the format also known as M23. M23 A method of multiplexing four DS1 signals into a DS2 signal, then multiplexing seven DS2 signals into a DS3 signal. MAC Media Access Control. Lower of
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Glossary Multicast Single packets copied by the network and sent to a specific subset of network addresses. These addresses are specified in the Destination Address field. Compare with Broadcast and Unicast. Multilink See MLP. Point-to-Point Multimode fiber See MMF. Multiplexing An activity in which multiple logical signals are transmitted simultaneously across a single physical channel. Multiprotocol Label See MPLS. Switching N NEBS Network Equipment Building Systems. The Telcordia (formerly
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Glossary Optical carrier See OC. Optical fiber See Fiber-optic cable. P Packet Logical grouping of information that includes a header containing control information and (usually) user data. Packets are most often used to refer to network layer units of data. The terms datagram, frame, message, and segment are also used to describe logical information groupings at various layers of the OSI reference model and in various technology circles. Packet Over SONET See POS. Packet switching Networking
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Glossary PRE Performance routing engine. The central routing unit for the Cisco uBR10012 universal broadband router. The PRE performs all Layer 2 and Layer 3 packet manipulation related to routing and forwarding through the Cisco uBR10012 routers. Use dual PREs in a single chassis for redundancy. See also PXF Network Processors. PXF Network Parallel eXpress Forwarding network processors. A pair of programmable ASICs that perform parallel Processors processing to support high performance Laye
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Glossary S SAR Segmentation and reassembly. One of the two sublayers of the AAL common part convergence sublayer, responsible for dividing (at the source) and reassembling (at the destination) the protocol data units (PDUs) passed from the convergence sublayer. The SAR sublayer takes the PDUs processed by the convergence sublayer and, after dividing them into 48-byte pieces of payload data, passes them to the ATM layer for further processing. See also AAL. SFP small formfactor pluggable (mod
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Glossary T3 Digital WAN carrier facility. T3 transmits DS3-formatted data at 44.736 Mbps through the telephone switching network. TAC A Cisco Technical Assistance Center. There are four TACs worldwide. TACACS Terminal Access Controller Access Control System. Authentication protocol, developed by the DDN community, that provides remote access authentication and related services, such as event logging. User passwords are administered in a central database rather than in individual routers, prov
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Glossary U UBR See Universal Broadband Router. Unchannelized DS3 See Clear channel DS3. Unicast A message sent to a single network destination. Compare with Broadcast and Multicast. Universal A Cisco Cable Modem Termination System (CMTS) and carrier-class router that provides broadband Broadband Router high-speed data, broadband entertainment, and IP telephony solutions over a coaxial cable network. Utility Card Another name used in the software screens for the Timing, Communication, and Cont
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Glossary Wide-area network See WAN. WRED Weighted Random Early Detection. RED uses an algorithm to randomly discard packets.The result of the drop is that the source detects the dropped traffic and slows its transmission. WRED combines the capabilities of the 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 differen
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Glossary Cisco uBR10012 Universal Broadband Router Hardware Installation Guide GL-16 78-11450-03 Rev.B0
