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International Code Designator: Adapted from the subnetwork model of addressing, this assigns the mapping of Network layer addresses to ATM addresses. HSSI is one of two ATM formats for addressing created by the ATM Forum to be utilized with private networks. See also: DCC.
Internet Control Message Protocol: Documented in RFC 792, it is a Network layer Internet protocol for the purpose of reporting errors and providing information pertinent to IP packet procedures.
Institute of Electrical and Electronics Engineers: A professional organization that, among other activities, defines standards in a number of fields within computing and electronics, including networking and communications. IEEE standards are the predominant LAN standards used today throughout the industry. Many protocols are commonly known by the reference number of the corresponding IEEE standard.
The IEEE specification for STP (Spanning Tree Protocol). The STP uses SPA (Spanning Tree Algorithm) to find and prevent network loops in bridged networks.
The IEEE committee specification that defines Ethernet 10BaseT. Ethernet is a LAN protocol that specifies physical layer and MAC sublayer media access. IEEE 802.3 uses CSMA/CD to provide access for many devices on the same network. FastEthernet is defined as 802.3u, and Gigabit Ethernet is defined as 802.3q. See also: CSMA/CD.
IEEE committee that defines Token Ring media access.
Internet Group Management Protocol: Employed by IP hosts, the protocol that reports their multicast group memberships to an adjacent multicast router.
Interior Gateway Protocol: Any protocol used by the Internet to exchange routing data within an independent system.
(Interior Gateway Routing Protocol) A distance-vector routing protocol from Cisco Systems for use in large heterogeneous networks.
Integrated (or Interim) Local Management Interface. A specification created by the ATM Forum, designated for the incorporation of network-management capability into the ATM UNI. Integrated Local Management Interface cells provide for automatic configuration between ATM systems. In LAN emulation, ILMI can provide sufficient information for the ATM end station to find an LECS. In addition, ILMI provides the ATM NSAP (network service access point) prefix information to the end station.
In-band management is the management of a network device “through” the network using Simple Network Management Protocol (SNMP) or Telnet.
In an ATM network, it is the largest, temporarily permitted data burst exceeding the insured rate on a PVC and not tagged by the traffic policing function for being dropped if network congestion occurs. This insured burst is designated in bytes or cells.
A very efficient system, IVR allows information to be retrieved via telephone lines without anyone on the other end of the line.
Routing between two or more logical areas. Contrast with: intra-area routing. See also: area.
Any of several processor modules used with Cisco 7000 series routers. See also: AIP, CIP, EIP, FEIP, HIP, MIP, and TRIP.
The global “network of networks,” whose popularity has exploded in the last few years. Originally a tool for collaborative academic research, it has become a medium for exchanging and distributing information of all kinds. The Internet’s need to link disparate computer platforms and technologies has led to the development of uniform protocols and standards that have also found widespread use within corporate LANs. See also: TCP/IP and MBONE.
Before the rise of the Internet, this lowercase form was shorthand for “internetwork” in the generic sense. Now rarely used. See also: internetwork.
Any protocol belonging to the TCP/IP protocol stack. See also: TCP/IP.
Any group of networks interconnected by routers and other mechanisms, typically operating as a single entity.
Broadly, anything associated with the general task of linking networks to each other. The term encompasses technologies, procedures, and products. When you connect networks to a router, you are creating an internetwork.
Routing that occurs within a logical area. Contrast with: interarea routing.
(IDS) A software package designed to detect specific actions on a network that are typical of an intruder or that might indicate an act of corporate espionage.
An IDS package monitors the network or the server for specific “attack signatures” that might indicate an active intruder is attempting to gain access to the network; such actions are carefully documented by the system.
Specific actions, such as opening or renaming certain important files, opening specific applications, downloading large amounts of data from key documents, or sending classified documents out as e-mail attachments, are also monitored by the IDS software.
Inverse Address Resolution Protocol: A technique by which dynamic routes are constructed in a network, allowing an access server to locate the network address of a mechanism affiliated with a permanent virtual circuit (PVC).
The International Organization for Standardization (ISO) defines the types of network management applications that reside on the NMS. Just as the seven-layer OSI model defines function but not implementation for data communications, the ISO network management model defines five areas of network management without specifying specific implementations.
Internet Protocol: Defined in RFC 791, it is a Network layer protocol that is part of the TCP/IP stack and allows connectionless service. IP furnishes an array of features for addressing, type-of-service specification, fragmentation and reassembly, and security.
When you use the ip unnumbered command, a serial interface is not on a separate network, as all router interfaces tend to be. Instead, the serial port “borrows” an IP address from another interface.
Often called an Internet address, this is an address uniquely identifying any device (host) on the Internet (or any TCP/IP network). Each address consists of four octets (32 bits), represented as decimal numbers separated by periods (a format known as “dotted-decimal”). Every address is made up of a network number, an optional subnetwork number, and a host number. The network and subnetwork numbers together are used for routing, while the host number addresses an individual host within the network or subnetwork. The network and subnetwork information is extracted from the IP address using the subnet mask. There are five classes of IP addresses (A–E), which allocate different numbers of bits to the network, subnetwork, and host portions of the address. See also: CIDR, IP, and subnet mask.
With the growth of the Internet since the early 1990s, the IETF, IANA, IAB, and many networking vendors have realized the need for an expanded IP address space. RFC 2373 defines the IP version 6 addressing architecture. IP version 6 addresses are 128 bits in length and are globally unique.
IP Control Protocol: The protocol used to establish and configure IP over PPP. See also: IP and PPP.
A broadcast-based protocol such as DHCP, DNS, and WINS that is forwarded across the router when configured with the ip helper-address command.
A Cisco IOS command for specifying that broadcast- based protocols are forwarded across the router.
A technique for routing that enables IP traffic to be reproduced from one source to several endpoints or from multiple sources to many destinations. Instead of transmitting only one packet to each individual point of destination, one packet is sent to a multicast group specified by only one IP endpoint address for the group.
(IPSec) A suite of protocols under development by the Internet Engineering Task Force (IETF) designed to add security provisions to the Internet Protocol (IP).
The Authentication Header (AH) ensures that the datagram has not been tampered with during transmission, and the Encapsulating Security Payload (ESP) defines encryption methods for IP data.
IPSec operates in two modes:
Transport mode: AH or ESP is placed immediately after the original IP datagram header and provides security between two end systems such as a server and a workstation.
Tunnel mode: The original IP datagram is placed inside a new datagram, and AH and ESP are inserted between the IP header of the new packet and the original IP datagram. The new header points to the tunnel endpoint, and the original header points to the final destination of the datagram. Tunnel mode is best suited to Virtual Private Network (VPN) use, securing remote access to your corporate network through the Internet.
Internetwork Packet Exchange: Network layer protocol (Layer 3) used in Novell NetWare networks for transferring information from servers to workstations. Similar to IP and XNS.
A logical address used to send packets through a Novell intranetwork.
IPX Control Protocol: The protocol used to establish and configure IPX over PPP. See also: IPX and PPP.
Protocol used for new WAN links to provide and negotiate line options on the link using IPX. After the link is up and the options have been agreed upon by the two end-to-end links, normal IPX transmission begins.
Integrated Services Digital Network: Offered as a service by telephone companies, a communication protocol that allows telephone networks to carry data, voice, and other digital traffic. See also: BISDN, BRI, and PRI.
Intermediate System–to–Intermediate System, or IS-IS, is an interior routing protocol or an Interior Gateway Protocol (IGP). Developed in the 1980’s, IS-IS was intended to be the routing protocol for OSI in an attempt to produce a standards protocol suite that could allow internetworks generous scalability.
Asynchronous data transfer over a synchronous data link, requiring a constant bit rate for reliable transport. Compare with: asynchronous transmission and synchronous transmission.
Also called DMZ but can be a stand-alone LAN within a campus LAN for security purposes.
International Telecommunication Union Telecommunication Standardization Sector: This is a group of engineers that develops worldwide standards for telecommunications technologies.
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