Interior Border Gateway Protocol. IBGP is the BGP version used within an AS.


Independent Basic Service Set (see BSS). An IBSS is the 802.11 term for an ad-hoc network. See ad-hoc mode.


Internet Control Message Protocol. ICMP is the part of the TCP/IP protocol that allows generation of error messages, test packets, and operating messages. For example, the ping command allows you to send ICMP echo messages to a remote IP device to test for connectivity. ICMP also supports traceroute, which identifies intermediate hops between a given source and destination.


ICV (Integrity Check Value) is a 4-byte code appended in standard WEP to the 802.11 message. Enhanced WPA inserts an 8-byte MIC just before the ICV. (See WPA and MIC.)


Institute of Electrical and Electronic Engineers. This technical professional society fosters the development of standards that often become national and international standards. The organization publishes a number of journals and has many local chapters and several large societies in special areas.


Internet Engineering Task Force. The IETF is a large, open, international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. The technical work of the IETF is done in working groups, which are organized by topic.


Internet Group Management Protocol. Hosts use IGMP to inform local routers of their membership in multicast groups. Multicasting allows one computer on the Internet to send content to multiple other computers that have identified themselves as interested in receiving the originating computer's content. When all hosts leave a group, the router no longer forwards packets that arrive for the multicast group.

IGMP snooping

This provides a method for intelligently forwarding multicast packets within a Layer 2 broadcast domain. By “snooping” the IGMP registration information, the device forms a distribution list that determines which endstations receive packets with a specific multicast address. Layer 2 switches listen for IGMP messages and build mapping tables and associated forwarding filters. IGMP snooping also reduces IGMP protocol traffic.


Interior Gateway Protocol. IGP refers to any protocol used to exchange routing information within an AS. Examples of Internet IGPs include RIP and OSPF.

inline power

According to IEEE 802.3 af, inline power refers to providing an AC or DC power source through the same cable as the data travels. It allows phones and network devices to be placed in locations that are not near AC outlets. Most standard telephones use inline power.

infrastructure mode

An 802.11 networking framework in which devices communicate with each other by first going through an access point. In infrastructure mode, wireless devices can communicate with each other or can communicate with a wired network. (See ad-hoc mode and BSS.)

intermediate certificate

A certificate in the middle of a certificate chain, that bridges the trust relationship between the server certificate and the trusted certificate.


Internet Protocol. The communications protocol underlying the Internet, IP allows large, geographically diverse networks of computers to communicate with each other quickly and economically over a variety of physical links; it is part of the TCP/IP suite of protocols. IP is the Layer 3, or network layer, protocol that contains addressing and control information that allows packets to be routed. IP is the most widely used networking protocol; it supports the idea of unique addresses for each computer on the network. IP is a connectionless, best-effort protocol; TCP reassembles the data after transmission. IP specifies the format and addressing scheme for each packet.


Interprocess Communication. A capability supported by some operating systems that allows one process to communicate with another process. The processes can be running on the same computer or on different computers connected through a network.


Internet Protocol security (IPSec) Internet Protocol security.
Encapsulating Security Payload (IPsec-ESP) The encapsulating security payload (ESP) encapsulates its data, enabling it to protect data that follows in the datagram.
Internet Protocol security Authentication Header (IPsec-AH) AH protects the parts of the IP datagram that can be predicted by the sender as it will be received by the receiver.

IPsec is a set of protocols developed by the IETF to support secure exchange of packets at the IP layer. IPsec has been deployed widely to implement Virtual Private Networks (VPNs).

IPsec supports two encryption modes: Transport and Tunnel. Transport mode encrypts only the data portion (payload) of each packet, but leaves the header untouched. The more secure Tunnel mode encrypts both the header and the payload. On the receiving side, an IPSec-compliant device decrypts each packet.

For IPsec to work, the sending and receiving devices must share a public key. This is accomplished through a protocol known as Internet Security Association and Key Management Protocol/Oakley (ISAKMP/Oakley), which allows the receiver to obtain a public key and authenticate the sender using digital certificates.


Internet Protocol version 6. IPv6 is the next-generation IP protocol. The specification was completed in 1997 by IETF. IPv6 is backward- compatible with and is designed to fix the shortcomings of IPv4, such as data security and maximum number of user addresses. IPv6 increases the address space from 32 to 128 bits, providing for an unlimited (for all intents and purposes) number of networks and systems; IPv6 is expected to slowly replace IPv4, with the two existing side by side for many years.

IP address

IP address is a 32-bit number that identifies each unique sender or receiver of information that is sent in packets; it is written as four octets separated by periods (dotted-decimal format). An IP address has two parts: the identifier of a particular network and an identifier of the particular device (which can be a server or a workstation) within that network. You may add an optional sub-network identifier. Only the network part of the address is looked at between the routers that move packets from one point to another along the network. Although you can have a static IP address, many IP addresses are assigned dynamically from a pool. Many corporate networks and online services economize on the number of IP addresses they use by sharing a pool of IP addresses among a large number of users. (The format of the IP address is slightly changed in IPv6.)


Internal Protocol television. IPTV uses a digital signal sent via broadband through a switched telephone or cable system. An accompanying set top box (that sits on top of the TV) decodes the video and converts it to standard television signals.


Internal router. In OSPF, IR is an internal router that has all interfaces within the same area.


Internet Router Discovery Protocol. Used with IP, IRDP enables a host to determine the address of a router that it can use as a default gateway. In Extreme Networks implementation, IP multinetting requires a few changes for the IRDP.


This abbreviation is commonly used for the International Organization for Standardization, although it is not an acronym. ISO was founded in 1946 and consists of standards bodies from more than 75 nations. ISO had defined a number of important computer standards, including the OSI reference model used as a standard architecture for networking.


Isochronous data is data (such as voice or video) that requires a constant transmission rate, where data must be delivered within certain time constraints. For example, multimedia streams require an isochronous transport mechanism to ensure that data is delivered as fast as it is displayed and to ensure that the audio is synchronized with the video. Compare: asynchronous processes in which data streams can be broken by random intervals, and synchronous processes, in which data streams can be delivered only at specific intervals.


An Internet Service Provider is an organization that provides access to the Internet. Small ISPs provide service via modem and ISDN while the larger ones also offer private line hookups (T1, fractional T1, etc.). Customers are generally billed a fixed rate per month, but other charges may apply. For a fee, a Web site can be created and maintained on the ISP's server, allowing the smaller organization to have a presence on the Web with its own domain name.


International Telecommunication Union-Telecommunication. The ITU-T is the telecommunications division of the ITU international standards body.


Initialization Vector. Part of the standard WEP encryption mechanism that concatenates a shared secret key with a randomly generated 24-bit initialization vector. WPA with TKIP uses 48-bit IVs, an enhancement that significantly increases the difficulty in cracking the encryption. (See WPA and TKIP.)