Polycom MGC Administrator, Administrator'S Manual

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MGC Administrator’s Guide
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transferred directly between the User Agents. SIP User Agents in most cases
use URIs (Uniform Resource Identifiers) to contact each other. The SIP
proxy, retrieves the current location of the invited endpoint. It then proceeds
to insert the location in the Invite and forward the Invite to its final
destination.
The SIP proxy can also function as an Outbound proxy. All messages from
the MCU and Registrar are sent to the Outbound proxy, which forwards them
to their destination according to the address included in the message header.
It should be noted that proxy servers do not initiate sessions, but forward the
Invites from parties that are allowed to do so.
Registrar (Registration Server)
A registrar is logical entity that is part of the SIP server. User agents (UAs)
upon initialization and at periodic intervals send Register messages to the
registrar. The registrar accepts these Register messages and associates the
UA’s URI, e.g. sip:dan@polycom.com, with the device this UA is currently
logged on. The registrar writes this association, also called ‘binding’, to a
database (Location Server), which is accessed by other SIP servers in the
same administrative domain to locate registered UAs. One URI can be
assigned to several IP addresses, so if a user is away, another device can be
used for connection.
The registration server is typically co-located with either a proxy or redirect
server.
Redirect Server
A redirect server is logical entity that is part of the SIP server. A redirect
server is a SIP server that responds by providing the current address of the
requested endpoint which is retrieved from the location service database.
Unlike the proxy which actually inserts the final destination’s address in the
H.323 SIP
N/A Optional
(Recommended)
H.323 SIP
N/A Optional