Cisco 7960 Administrator's Manual page 197

Glossary
P
PDU
Protocol data units used by bridges to transfer connectivity information.
POTS
Plain old telephone service. Basic telephone service supplying standard single line telephones, telephone
lines, and access to the PSTN.
Proxy Server
An intermediary program that acts as both a server and a client for the purpose of making requests on
behalf of other clients. Requests are serviced internally or by passing them on, possibly after translation,
to other servers. A proxy interprets, and, if necessary, rewrites a request message before forwarding it.
PSTN
Public switched telephone network. PSTN refers to the local telephone company.
R
Redirect Server
A redirect server is a server that accepts a SIP request, maps the address into zero or more new addresses
and returns these addresses to the client. It does not initiate its own SIP request nor accept calls.
Registrar
A registrar is a server that accepts REGISTER requests. A registrar is typically co-located with a proxy
or redirect server and MAY offer location services.
RAS
Registration, admission, and status protocol. This is the protocol that is used between endpoints and the
gatekeeper to perform management functions.
RBS
Robbed bit signaling.
Cisco SIP IP Phone 7960 Administrator Guide
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