Chapter 9 Voice
The response to the request goes to all the proxy servers through which the request passed, in reverse sequence. Once the session is set up, session traffic is sent between the UAs directly, bypassing all the proxy servers in between.
The following figure shows the SIP and session traffic flow between the user agents (UA 1 and UA 2) and the proxy servers (this example shows two proxy servers, PROXY 1 and PROXY 2).
Figure 99 SIP Call Through | Proxy Servers | ||||
PROXY 1 |
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SIP | SIP |
SIP & RTP
UA 1 | UA 2 |
The following table shows the SIP call progression.
Table 65 SIP Call Progression
UA 1 |
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| PROXY 1 |
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| PROXY 2 |
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| UA 2 |
Invite |
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| Invite |
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| 100 Trying |
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| Invite |
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| 100 Trying |
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| 180 |
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| Ringing |
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| Ringing |
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| Ringing |
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ACK |
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| 200 OK |
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RTP |
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| RTP |
200 OK |
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| BYE |
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222 |
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