ADTRAN Atlas 550 User Manual page 248

Appendix G. Glossary
Packet Endpoint
A virtual port within the ATLAS 550 that a specified physical port terminates its data into for further
routing by the system.
Packet Switching
A method of routing packets that avoids congestion and minimizes delivery time.
PBX
Private branch exchange. A telephone system usually owned by the customer that serves a particular
location. It provides connections from one phone extension to another and connects to the external
telephone network.
PCM
Pulse Code Modulation. The most common method for encoding analog voice into a digital bit stream.
PIV
Port/PVC Interval. Think of this as a resource meter. The ATLAS 550 can track up to 10,000 PIVs. The
PIV is derived from the Max Number of Days and Max Number of Intervals selected by the user.
Changing one affects the other.
PRI
Primary Rate ISDN. An ISDN service that provides 23 B (bearer) channels (64 kbps each) and 1 D
(data) channel (64 kpbs). The combined capacities are equivalent to one T1 channel.
PVC
Permanent Virtual Circuit. Virtual circuit within the frame relay network that has all bandwidth
parameters permanently defined upon ordering the circuit.
QOS
Quality of service. A means of guaranteeing available bandwidth under normal operating conditions.
Quad BRI/U Module
One of the ATLAS 550 option modules. The Quad BRI/U Module provides four basic rate ISDN U
interfaces, each capable of operating in NT or LT mode.
Remote Access
The ability to connect to non-local communications equipment.
RIP
Routing Information Protocol. A protocol used to exchange routing information among a set of com-
puters connected by a LAN. RIP uses hop count as a routing metric.
robbed bit signaling
A type of in-band signaling used with voice transmissions for multiplexing multiple voice circuits
onto a T1.
Router
An interface which finds the best path between two networks. Routers forward packets from one net-
work to another, based on network layer information.
Routing Metric
The method by which a routing algorithm determines that one route is better than another. This infor-
mation is stored in routing tables. Such tables include reliability, delay bandwidth, load, MTUs, com-
munication costs, and hop count.
G-8 ATLAS 550 User Manual 61200305L1-1