Glossary
154 Express XL/XLT User Manual 61200.070L1-1
point-to-point protocol (PPP)
An implementation of TCP/IP which is intended for transmission using tele-
phone lines. PPP provides router-to-router and host-to-network connections
over both synchronous and asynchronous circuits.
poison routes
Routes which have an infinite metric which to other routers means the net-
work for the route is inaccessible.
PRA Primary Rate Access. Connects high-capacity CPE, such as PBXs, to the net-
work. In the US, this is composed of twenty-three 64 kbps channels and one
64 kbps D-channel. Also known as Primary Rate Interface (PRI).
RIP Routing Information Protocol. A protocol used to exchange routing informa-
tion among a set of computers connected by a LAN. RIP uses hop counts as a
routing metric.
router An interface which finds the best route between two networks. Routers for-
ward packets from one network to another, based on network layer informa-
tion.
routing metric
The method by which a routing algorithm determines one route is better than
another. This information is stored in routing tables. Such tables include reli-
ability, delay bandwidth, load, MTUs, communication costs, and hop count.
RS-232-C
An EIA-specified physical interface with associated electrical signalling be-
tween DCE and DTE. The most commonly employed interface between com-
puter devices and modems.
RTMP Routing Table Maintenance Protocol. The AppleTalk protocol used to estab-
lish and maintain the routing information that is required by internet routers
in order to route datagrams from any source socket to any destination socket
in the internet. Using RTMP, internet routers dynamically maintain routing
tables to reflect changes in internet topology.
service advertising protocol (SAP)
An IPX protocol through which network resources such as servers become
known to clients.