Cisco Systems IP phone 7960 manual To reestablish the call between phone a and phone B

Appendix B SIP Call Flows

Call Flow Scenarios for Successful Calls

Step	Action	Description
8	INVITE—Cisco SIP IP phone B	Cisco SIP IP phone B sends a mid-call INVITE to Cisco
	to Cisco SIP IP phone A	SIP IP phone A with the same call ID as the previous
		INVITE and new SDP session parameters (IP address),
		which are used to reestablish the call.
		Call_ID=1
		SDP: c=IN IP4 181.23.250.2
		To reestablish the call between phone A and phone B, the
		IP address of phone B is inserted into the c= SDP field.
9	200 OK—Cisco SIP IP phone A	Cisco SIP IP phone A sends a SIP 200 OK response to
	to Cisco SIP IP phone B	Cisco SIP IP phone B.
10	ACK—Cisco SIP IP phone B to	Cisco SIP IP phone B sends a SIP ACK to Cisco SIP IP
	Cisco SIP IP phone A	phone A. The ACK confirms that Cisco SIP IP phone B has
		received the 200 OK response from Cisco SIP IP phone A.

A two-way RTP channel is reestablished between IP phone A and IP phone B.

Cisco SIP IP Phone-to-Cisco SIP IP Phone Call Hold with Consultation

Figure B-5 illustrates a successful call between Cisco SIP IP phones in which one of the participants places the other on hold, calls a third party (consultation), and then returns to the original call. In this call flow scenario, the end users are User A, User B, and User C. They are all using Cisco SIP IP phones, which are connected via an IP network.

The call flow scenario is as follows:

1.User A calls User B.

2.User B answers the call.

3.User B places User A on hold.

4.User B calls User C.

5.User B disconnects from User C.

6.User B takes User A off hold.

7.The original call continues.

	Cisco SIP IP Phone 7960 Administrator Guide
B-20	78-10497-02