Cisco 7960G Administration Manual page 132

Call Flow Scenarios for Successful Calls
Figure B-11 Network Call Forwarding (Unconditional)
SIP IP
Phone
User A
2-way RTP channel
Step Action
INVITE—Phone A to SIP proxy
1.
server
INVITE—SIP proxy server to
2.
SIP redirect server
Cisco Unified IP Phone 7960G and 7940G Administration Guide for Release 8.0 (SIP)
B-32
IP
Proxy
Server
1. INVITE B
8. 200 OK
9. ACK
Description
Phone A sends a SIP INVITE request to the SIP proxy server. The 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 e-mail 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:555-0199@companyb.com; user=phone." The "user=phone" parameter
distinquishes that the Request-URI address is a telephone number rather than
a username.
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.
•
The SIP proxy server sends the SIP INVITE request to the SIP redirect server.
IP Network
Redirect
Server
2. INVITE B
3. 302 Moved Temporarily
4. ACK
5. INVITE C
6. 180 Ringing
7. 200 OK
10. ACK
Appendix B SIP Call Flows
IP IP
SIP IP SIP IP
Phone Phone
User B User C
OL-7890-01