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Glossary

holddown

The state a route is placed in so that routers can neither adver-

tise the route nor accept advertisements about it for a defined time period.
Holddown is used to surface bad information about a route from all routers
in the network. A route is generally placed in holddown when one of its
links fails.

hop

The movement of a packet between any two network nodes. See also:

hop count.

hop count

A routing metric that calculates the distance between a

source and a destination. RIP employs hop count as its sole metric. See
also: hop and RIP.

host address

Logical address configured by an administrator or server on

a device. Logically identifies this device on an internetwork.

HSCI

High-Speed Communication Interface: Developed by Cisco, a single-

port interface that provides full-duplex synchronous serial communications
capability at speeds up to 52Mbps.

HSRP

Hot Standby Router Protocol: A protocol that provides high net-

work availability and provides nearly instantaneous hardware fail-over
without administrator intervention. It generates a Hot Standby router
group, including a lead router that lends its services to any packet being
transferred to the Hot Standby address. If the lead router fails, it will be
replaced by any of the other routers--the standby routers--that monitor it.

HSSI

High-Speed Serial Interface: A network standard physical connector

for high-speed serial linking over a WAN at speeds of up to 52Mbps.

hubs

Physical-layer devices that are really just multiple port repeaters.

When an electronic digital signal is received on a port, the signal is reampli-
fied or regenerated and forwarded out all segments except the segment from
which the signal was received.

ICD

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.

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