Appendix B SIP Call Flows
Call Flow Scenarios for Successful Calls
Step | Action | Description |
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3 | 200 | Cisco SIP IP phone B sends a SIP 200 OK response to |
| to Cisco SIP IP phone A | Cisco SIP IP phone A. The 200 OK response notifies Cisco |
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| SIP IP phone A that the connection has been made. |
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| If Cisco SIP IP phone B supports the media capability |
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| advertised in the INVITE message sent by Cisco SIP IP |
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| phone A, it advertises the intersection of its own and Cisco |
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| SIP IP phone A’s media capability in the 200 OK response. |
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| If Cisco SIP IP phone B does not support the media |
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| capability advertised by Cisco SIP IP phone A, it sends |
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| back a 400 Bad Request response with a 304 Warning |
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| header field. |
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4 | Cisco SIP IP phone A sends a SIP ACK to Cisco SIP IP | |
| Cisco SIP IP phone B | phone B. The ACK confirms that Cisco SIP IP phone A has |
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| received the 200 OK response from Cisco SIP IP phone B. |
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| The ACK might contain a message body with the final |
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| session description to be used by Cisco SIP IP phone B. If |
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| the message body of the ACK is empty, Cisco SIP IP phone |
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| B uses the session description in the INVITE request. |
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A
5 |
| Cisco SIP IP phone C sends a SIP INVITE request to Cisco | ||||
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| to Cisco SIP IP phone B | SIP IP phone B. The INVITE request is an invitation to | |||
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| User B to participate in a call session. | |
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6 |
| 180 | Cisco SIP IP phone B sends a SIP 180 Ringing response to | |||
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| phone B to Cisco SIP IP phone C | Cisco SIP IP phone C. | |||
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7 |
| Cisco SIP IP phone B sends a | ||||
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| to Cisco SIP IP phone A | SIP IP phone A with new SDP session parameters | |||
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| (IP address), which are used to place the call on hold. | |
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| Call_ID=1 | |
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| SDP: c=IN IP4 0.0.0.0 | |
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| The c= SDP field of the SIP INVITE contains 0.0.0.0. This | |
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| places the call in limbo. | |
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8 |
| 200 | Cisco SIP IP phone A sends a SIP 200 OK response to | |||
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| to Cisco SIP IP phone B | Cisco SIP IP phone B. | |||
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| Cisco SIP IP Phone 7960 Administrator Guide | ||
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