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Glossary

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IP unnumbered

Cisco proprietary protocol that allows two point-to-

point links to communicate without an IP address.

IPX

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.

IPXCP

IPX Control Program: The protocol used to establish and configure

IPX over PPP. See also: IPX and PPP.

IPX spoofing

Provides IPX RIP/SAP traffic without requiring a connec-

tion to the opposing network. This allows a per-minute tariffed link, such as
ISDN or analog phone, to support IPX without requiring the link to remain
active.

IPXWAN

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.

IRDP

ICMP Router Discovery Protocol: Allows hosts to use the Internet

Control Message Protocol (ICMP) to find a new path when the primary
router becomes unavailable. IRDP is an extension to the ICMP protocol and
not a dynamic routing protocol. This ICMP extension allows routers to
advertise default routes to end stations.

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.

ISL routing

Inter-Switch Link routing is 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.

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