Chapter 21 Voice
186
1
A
sends a SIP INVITE request to
B
. This message is an invitation for
B
to participate in a SIP
telephone call.
2
B
sends a response indicating that the telephone is ringing.
3
B
sends an OK response after the call is answered.
4
A
then sends an ACK message to acknowledge that
B
has answered the call.
5
Now
A
and
B
exchange voice media (talk).
6
After talking,
A
hangs up and sends a BYE request.
7
B
replies with an OK response confirming receipt of the BYE request and the call is terminated.
SIP Call Progression Through Proxy Servers
Usually, the SIP UAC sets up a phone call by sending a request to the SIP proxy server. Then, the
proxy server looks up the destination to which the call should be forwarded (according to the URI
requested by the SIP UAC). The request may be forwarded to more than one proxy server before
arriving at its destination.
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.
3. OK
4. ACK
5.Dialogue (voice traffic)
6. BYE
7. OK
Table 104
SIP Call Progression (continued)
A
B
Summary of Contents for Movistar GPT-2541GNAC
Page 47: ...Chapter 4 LAN 47 Figure 25 LAN Setup...
Page 99: ...Chapter 11 DNS 99 Figure 62 DNS Server...
Page 144: ...Chapter 20 Wireless 144 Figure 92 Wireless Security...
Page 166: ...Chapter 21 Voice 166...
Page 196: ...Chapter 21 Voice 196...
