Q.931 CALL PROCEEDING

此 Q.931 訊息是被叫送給主叫表示已經開始建立請求的呼叫，不再接受其它呼叫建立資訊。

什麼是 call establishment information (呼叫建立資訊)？

可有下列選擇性 IE

• Channel identification：如果是回應 SETUP 的第一個訊息，在 network-to-user 是必要的，在 user-to-network 不接受 SETUP 的 B-channel 時是必要的。
• Progress indicator：interworking 提供 in-band information/patterns。在 user-to-network if Annex K is implemented or in accordance with the procedures of 5.11.3 and 5.12.3.
• Display (限 n → u)：最長 34 或 82 octets。
• Bearer capability：included when the procedures of 5.11 for bearer capability selection apply. When present, progress indication No. 5, interworking has occurred and has resulted in a telecommunication service change, shall also be present.
• High layer compatibility：included when the procedures of 5.12 for high layer compatibility selection apply. When present, progress indication No. 5, interworking has occurred and has resulted in a telecommunication service change, shall also be present.

SIP interworking

• 收到 CALL PROCEEDING (撥入都用 En bloc，全部撥號都在 SETUP，沒有撥號結束的問題。)
• 忽略？
• 送 183？會被誤認為陣鈴？如果 183 /wo SDP 呢？
• 送 CALL PROCEEDIN
• ALERTING 前，也就是收到 180 或 183 /w SDP？
• 收到 183 /wo SDP？
• 送 SIP INVITE 前？
• 認為撥號結束？

參考

1. Q.931 3.1.2