Glossary F

E1: Generally used in Europe, a wide-area digital transmission scheme carrying data at 2.048Mbps. E1 transmission lines are available for lease from common carriers for private use.
E.164: (1) Evolved from the standard telephone numbering system, the standard recommended by ITU-T for international telecommunication numbering, particularly in ISDN, SMDS, and BISDN. (2) Label of a field in an ATM address containing numbers in E.164 format.
E channel: echo channel: A 64Kbps ISDN control channel used for circuit switching. Specific description of this channel can be found in the 1984 ITU-T ISDN specification, but was dropped from the 1988 version. Compare to: B channel, D channel, and H channel.
edge device: A device that enables packets to be forwarded between legacy interfaces (such as Ethernet and Token Ring) and ATM interfaces based on information in the Data Link and Network layers. An edge device does not take part in the running of any Network layer routing protocol; it merely uses the route description protocol in order to get the forwarding information required.
EEPROM: electronically erasable programmable read-only memory: Programmed after their manufacture, these non-volatile memory chips can be erased if necessary by using electric power and reprogrammed. Compare to: EPROM and PROM.
EFCI: Explicit Forward Congestion Indication: A congestion feedback mode permitted by ABR service in an ATM network. The EFCI can be set by any network element that is in a state of immediate or certain congestion. The destination end-system is able to carry out a protocol that adjusts and lowers the cell rate of the connection based on value of the EFCI. See also: ABR.
EIGRP: See: Enhanced IGRP.
EIP: Ethernet Interface Processor: A Cisco 7000 series router interface processor card, supplying 10Mbps AUI ports to support Ethernet Version 1 and Ethernet Version 2 or IEEE 802.3 interfaces with a high-speed data path to other interface processors.
ELAN: Emulated LAN: An ATM network configured by using a client/server model in order to emulate either an Ethernet or Token Ring LAN. Multiple ELANs can exist at the same time on a single ATM network and are made up of a LAN Emulation Client (LEC), a LAN Emulation Server (LES), a broadcast and unknown server (BUS), and a LAN Emulation Configuration Server (LECS). ELANs are defined by the LANE specification. See also: LANE, LEC, LECS, and LES.
ELAP: EtherTalk Link Access Protocol: In an EtherTalk network, the link-access protocol constructed above the standard Ethernet Data Link layer.
enable packets: Packets that complete the flow cache. After the MLS-SE determines that the packet meets enable criteria, such as source MAC (SMAC) address and destination IP, the flow cache is established and subsequent packets are layer 3 switched. See also: MLS-SE and MLS-RP.
encapsulation: The technique used by layered protocols in which a layer adds header information to the Protocol Data Unit (PDU) from the layer above. As an example, in Internet terminology, a packet would contain a header from the Physical layer, followed by a header from the Network layer (IP), followed by a header from the Transport layer (TCP), followed by the application protocol data.
encryption: The conversion of information into a scrambled form that effectively disguises it to prevent unauthorized access. Every encryption scheme uses some well-defined algorithm, which is reversed at the receiving end by an opposite algorithm in a process known as decryption.
end-to-end VLAN: VLAN that spans the switch-fabric from end to end; all switches in end-to- end VLANs understand about all configured VLANs. End-to-end VLANs are configured to allow membership based on function, project, department, and so on.
Enhanced IGRP (EIGRP): Enhanced Interior Gateway Routing Protocol: An advanced routing protocol created by Cisco, combining the advantages of link-state and distance-vector protocols. Enhanced IGRP has superior convergence attributes, including high operating efficiency. See also: IGP, OSPF, and RIP.
Enhanced Image: An Enhanced Image runs on certain Catalyst 2950 switches and supports all features of the Standard Image, plus extra QoS, security, and traffic management. See also: Standard Image.
enterprise network: A privately owned and operated network that connects most major locations in a large company or organization.
enterprise services: Services provided to all users on the internetwork. Layer 3 switches or routers are required in this scenario because the services must be close to the core and would probably be based in their own subnet. Examples of these services include Internet access, e-mail, and possibly videoconferencing. If the servers that host these enterprise services were placed close to the backbone, all users would have the same distance to them, but this also means that all users' data would have to cross the backbone to get to these services.
EPROM: erasable programmable read-only memory: Programmed after their manufacture, these non-volatile memory chips can be erased if necessary by using high-power light and reprogrammed. Compare to: EEPROM and PROM.
error correction: A process that uses a checksum to detect bit errors in the data stream.
ESF: Extended Superframe: Made up of 24 frames with 192 bits each, with the 193rd bit providing other functions including timing. This is an enhanced version of SF. See also: SF.
Ethernet: A baseband LAN specification created by the Xerox Corporation and then improved through joint efforts of Xerox, Digital Equipment Corporation, and Intel. Ethernet is similar to the IEEE 802.3 series standard and, using CSMA/CD, operates over various types of cables at 10Mbps. Also called 'DIX (Digital/Intel/Xerox) Ethernet.' Compare to: FastEthernet. See also: IEEE.
excess rate: In ATM networking, traffic exceeding a connection's insured rate. The excess rate is the maximum rate less the insured rate. Depending on the availability of network resources, excess traffic can be discarded during congestion episodes. Compare to: maximum rate.
expansion: The procedure of directing compressed data through an algorithm, restoring information to its original size.
expedited delivery: An option that can be specified by one protocol layer, communicating either with other layers or with the identical protocol layer in a different network device, requiring that identified data be processed faster.
explorer packet: An SNA packet transmitted by a source Token Ring device to find the path through a source-route-bridged network.
extended IP access list: IP access list that filters the network by logical address, protocol field in the Network layer header, and even the port field in the Transport layer header.
extended IPX access list: IPX access list that filters the network by logical IPX address, protocol field in the Network layer header, or even socket number in the Transport layer header.
Extended Setup: Used in setup mode to configure the router with more detail than Basic Setup mode. Allows multiple-protocol support and interface configuration.
external route processor: A router that is external to the switch. An external layer 3 routing device can be used to provide routing between VLANs.

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