Cisco Systems IP phone 7960 manual Step Action

Appendix B SIP Call Flows

Call Flow Scenarios for Successful Calls

Step Action Description

1INVITE—Cisco SIP IP phone A Cisco SIP IP phone A sends a SIP INVITE request to the

	to SIP proxy server		SIP proxy server. The INVITE request is an invitation to
			User B to participate in a call session.
			In the INVITE request:
			• The phone number of User B is inserted in the
			Request-URI field in the form of a SIP URL. The SIP
			URL identifies the address of User B and takes a form
			similar to an email address (user@host where user is
			the telephone number and host is either a domain name
			or a numeric network address). For example, the
			Request-URI field in the INVITE request to User B
			appears as “INVITE sip:555-0002@companyb.com;
			user=phone.” The “user=phone” parameter
			distinquishes that the Request-URI address is a
			telephone number rather than a user name.
			• Cisco SIP IP phone A is identified as the call session
			initiator in the From field.
			• A unique numeric identifier is assigned to the call and
			is inserted in the Call-ID field.
			• The transaction number within a single call leg is
			identified in the CSeq field.
			• The media capability User A is ready to receive is
			specified.
2	INVITE—SIP proxy server to		SIP proxy server sends the SIP INVITE request to the SIP
	SIP redirect server		redirect server.
3	300 Multiple Choices—SIP		SIP redirect server sends a SIP 300 Multiple choices
	redirect server to SIP proxy		message to the SIP proxy server. The message indicates
	server		that User B can be reached either at SIP phone B or Cisco
			SIP IP phone C.
4	INVITE—SIP proxy server to		SIP proxy server sends a SIP INVITE request to Cisco SIP
	Cisco SIP IP phone B		IP phone B. The INVITE request is an invitation to User B
			to participate in a call session.
5	180 Ringing—Cisco SIP IP		Cisco SIP IP phone B sends a SIP 180 Ringing response to
	phone B to SIP proxy server		the SIP proxy server.
		Cisco SIP IP Phone 7960 Administrator Guide
	B-50		78-10497-02