Huawei BM2022, Руководство пользователя

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Chapter 10 The VoIP Account Screens
BM2022 Users Guide
165
1
A sends a SIP INVITE request. This message is an invitation for B to participate in a SIP telephone
call. As INVITE specifies a SE of 60 seconds.
2 As request arrives at P but is below the minimum allowed value of 3600, so it is rejected with a 422
message, which contains the MSE of 3600.
3
A sends an ACK to acknowledge the message was received.
4 A retries the INVITE request with SE of 3600 and MSE of 3600.
5
The SE in the new INVITE is acceptable so P forwards it to B.
6 B receives the INVITE.
7
B responds with an OK message which includes the SE of 3600.
8
P forwards the OK message to A.
9
A receives the OK.
10
A then sends an ACK message to acknowledge that the call is established completely.
11
The proxy server forwards the ACK message to B.
12
Now A and B exchange voice media (talk).
13 After around half of the SE time period is reached, or 1800 seconds in this case, A sends an UPDATE
request to refresh the session.
13. UPDATE
SE: 3600
------------------>
14. UPDATE
SE:3600
-----------------------> -------------------->
<----------------------
15. OK
SE: 3600
<-------------------
16. OK
SE: 3600
<------------------
17. BYE
------------------>
18. OK
<-------------------
Table 72 SIP Call Progression (continued)
A P B