Linksys SPA9000 Administration Manual page 133

SIP UA
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RTP
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SIP UA
In this manual, the term client station is used to describe any SIP UA
Note
(including IP phones) that registers with the SPA9000.
In a SIP VoIP network, when the SIP proxy receives a request from a client station (UAS) for a
connection and it does not know the location of the UAC, it forwards the message to another
SIP proxy in the network. Once the UAC is located and the response is routed back to the UAS, a
direct peer-to-peer session is established between the two UAs. The actual voice traffic is
transmitted between UAs over dynamically assigned ports using the Real-time Protocol (RTP).
In Figure A-2, UserA and UserB are client stations (UAs) that register over the local area network
to which the SPA9000 PBX is connected. When UserA calls UserB, the SPA9000 acts as a SIP
proxy and establishes a session between the two UAs. After the session is established, RTP
traffic flows directly between the two client stations.
Linksys Voice System Administration Guide
Figure A-1 SIP Requests and Responses
SIP Proxy
SIP Proxy
Technology Background
SIP Proxy
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