Appendix B SIP Call Flows
Call Flow Scenarios for Successful Calls
Step | Action | Description |
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8 | Cisco SIP IP phone B sends a SIP INVITE request to Cisco | |
| to Cisco SIP IP phone C | SIP IP phone C. The INVITE request is an invitation to |
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| User C to participate in a call session. |
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9 | 180 | Cisco SIP IP phone C sends a SIP 180 Ringing response to |
| phone C to Cisco SIP IP phone B | Cisco SIP IP phone B. |
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10 | 200 | Cisco SIP IP phone C sends a SIP 200 OK response to |
| to Cisco SIP IP phone B | Cisco SIP IP phone B. The 200 OK response notifies Cisco |
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| SIP IP phone B 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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11 | Cisco SIP IP phone B sends a SIP ACK to Cisco SIP IP | |
| Cisco SIP IP phone C | phone C. The ACK confirms that Cisco SIP IP phone B has |
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| received the 200 OK response from Cisco SIP IP phone C. |
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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 C. If |
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| the message body of the ACK is empty, Cisco SIP IP phone |
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| C uses the session description in the INVITE request. |
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A
12 | The call continues and then User B hangs up. Cisco SIP IP | ||||
| Cisco SIP IP phone C | phone B sends a SIP BYE request to Cisco SIP IP phone C. | |||
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| The BYE request indicates that User B wants to release the | |
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| call. | |
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13 | 200 | Cisco SIP IP phone C sends a SIP 200 OK message to | |||
| to Cisco SIP IP phone B | Cisco SIP IP phone B. The 200 OK response notifies Cisco | |||
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| SIP IP phone B that the BYE request has been received. | |
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| The call session between User A and User B is now | |
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| terminated. | |
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The RTP channel between Cisco SIP IP phone B and Cisco SIP IP phone C is torn down. | |||||
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| Cisco SIP IP Phone 7960 Administrator Guide | ||
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