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Any of a number of 100Mbps Ethernet specifications. Fast Ethernet offers a speed increase 10 times that of the 10BaseT Ethernet specification while preserving such qualities as frame format, MAC mechanisms, and MTU. Such similarities allow the use of existing 10BaseT applications and network management tools on Fast Ethernet networks. Based on an extension to the IEEE 802.3 specification. 

fiberoptic connector. 

frame check sequence. Extra characters added to a frame for error control purposes. Used in HDLC, Frame Relay, and other data link layer protocols. 

flash file system. 

Industrystandard, packetswitched data link layer protocol that handles multiple virtual circuits between connected devices. 

gateway IP address 

Standard for a highspeed Ethernet, approved by the IEEE (Institute of Electrical and Electronics Engineers) 802.3z standards committee in 1996. 

HighLevel Data Link Control. Bitoriented synchronous data link layer protocol developed by ISO. Derived from SDLC, HDLC specifies a data encapsulation method on synchronous serial links using frame characters and checksums. 

In computer science, hexadecimal (also called base 16) is a numbering system with a base of 16. It uses 16 distinct symbols: 0–9 to represent values zero to nine, and A, B, C, D, E, and F to represent values 10 to 15. 

Internet Assigned Numbers Authority. Organization operated under the auspices of the ISOC as a part of the IAB. IANA delegates authority for IP addressspace allocation and domainname assignment to the InterNIC and other organizations. IANA also maintains a database of assigned protocol identifiers that is used in the TCP/IP stack, including autonomous system numbers. 

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

Internet Control Message Protocol version 4. 

Internet Control Message Protocol version 6 is the implementation of ICMP for IPv6. It is defined in RFC 4443. 

The IEEE 802.1Q specification establishes a standard method for tagging Ethernet frames with VLAN membership information and defines the operation of VLAN bridges that permit the definition, operation, and administration of VLAN topologies within a bridged LAN infrastructure. 

IEEE LAN protocol that specifies an implementation of the LLC sublayer of the data link layer. IEEE 802.2 handles errors, framing, flow control, and the network layer (Layer 3) service interface. Used in IEEE 802.3 and IEEE 802.5 LANs. 

IEEE LAN protocol that specifies an implementation of the physical layer and the MAC sublayer of the data link layer. IEEE 802.3 uses CSMA/CD access at various speeds over a variety of physical media. Extensions to the IEEE 802.3 standard specify implementations for Fast Ethernet. Physical variations of the original IEEE 802.3 specification include 10BASE2, 10BASE5, 10BASEF, 10BASET, and 10BROAD36. Physical variations for Fast Ethernet include 100BASET, 100BASET4, and 100BASEX. 

interior gateway protocol. Internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include IGRP, OSPF, and RIP. 

Internet Header Length. Name of an IP header field. 

Internet Network Information Center. Organization that serves the Internet community by supplying user assistance, documentation, training, registration service for Internet domain names, and other services. Formerly called NIC. 

IP Security. A framework of open standards that provides data confidentiality, data integrity, and data authentication between participating peers. IPsec provides these security services at the IP layer. IPsec uses IKE to handle the negotiation of protocols and algorithms based on local policy and to generate the encryption and authentication keys to be used by IPsec. IPsec can protect one or more data flows between a pair of hosts, between a pair of security gateways, or between a security gateway and a host. 

Intermediate SystemtoIntermediate System. OSI linkstate hierarchical routing protocol based on DECnet Phase V routing, whereby ISs (routers) exchange routing information based on a single metric to determine network topology. 

InterSwitch Link. Cisco proprietary protocol that maintains VLAN information as traffic flows between switches and routers. 

Internet service provider. Company that provides Internet access to other companies and individuals. 

integrated services router. An ISR specifies the elements to guarantee QoS on networks. For example, an ISR can be used to allow video and sound to reach the receiver without interruption. Every application that requires some kind of guarantee has to make an individual reservation. 

Latin American and Caribbean Network Information Center. 

local connector. 

local Internet registry. 

Link Layer Discovery Protocol. 

linkstate advertisement. A broadcast packet used by linkstate protocols that contains information about neighbors and path costs. LSAs are used by the receiving routers to maintain their routing tables. Sometimes called an LSP. 

a standardized data link layer address that is required for every port or device that connects to a LAN. Other devices in the network use these addresses to locate specific ports in the network and to create and update routing tables and data structures. A MAC address is 6 bytes long and is controlled by the IEEE. It is also known as a hardware address, MAC layer address, and physical address. 

Message Digest 5. A oneway hashing algorithm that produces a 128bit hash. Both MD5 and Secure Hash Algorithm (SHA) are variations on MD4 and are designed to strengthen the security of the MD4 hashing algorithm. Cisco uses hashes for authentication within the IPsec framework. Also used for message authentication in SNMP v.2. MD5 verifies the integrity of the communication, authenticates the origin, and checks for timeliness. 

media interface connector. MIC is the FDDI de facto standard connector. 

multimode fiber. An optical fiber supporting the propagation of multiple frequencies of light. 

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