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Glossary
ISDN
Integrated Services Digital Network: Offered as a service by tele-
phone companies, a communication protocol that allows telephone net-
works to carry data, voice, and other digital traffic. See also: BISDN, BRI,
and PRI.
IS-IS
Intermediate System-to-Intermediate System: An OSI link-state
hierarchical routing protocol.
ISL routing
Inter-Switch Link routing: A Cisco proprietary method of
frame tagging in a switched internetwork. Frame tagging is a way to identify
the VLAN membership of a frame as it traverses a switched internetwork.
isochronous transmission
Asynchronous data transfer over a synchro-
nous data-link, requiring a constant bit rate for reliable transport. Compare
with: asynchronous transmission and synchronous transmission.
ITU-T
International Telecommunication Union-Telecommunication Stan-
dardization Sector: This is a group of engineers that develops worldwide
standards for telecommunications technologies.
Kerberos
An authentication and encryption method that can be used by
Cisco routers to ensure that data cannot be "sniffed" off of the network.
Kerberos was developed at MIT and was designed to provide strong security
using the Data Encryption Standard (DES) cryptographic algorithm.
LAN
local area network: Broadly, any network linking two or more com-
puters and related devices within a limited geographical area (up to a few
kilometers). LANs are typically high-speed, low-error networks within a
company. Cabling and signaling at the Physical and Data Link layers of the
OSI are dictated by LAN standards. Ethernet, FDDI, and Token Ring are
among the most popular LAN technologies. Compare with: MAN.
LANE
LAN emulation: The technology that allows an ATM network to
operate as a LAN backbone. To do so, the ATM network is required to pro-
vide multicast and broadcast support, address mapping (MAC-to-ATM),
SVC management, in addition to an operable packet format. Additionally,
LANE defines Ethernet and Token Ring ELANs. See also: ELAN.
LAN switch
A high-speed, multiple-interface transparent bridging mecha-
nism, transmitting packets between segments of data links, usually referred
to specifically as an Ethernet switch. LAN switches transfer traffic based on
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