Yealink SIP-T58V/A

Appendix
805
Step
Action
Description
 User 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 port on which User B is prepared
to receive the RTP data is specified.
F2
INVITE—Proxy Server to User B
The proxy server maps the SIP URI in the To
field to User B. The proxy server sends the
INVITE message to User B.
F3
302 Move Temporarily—User B to
Proxy Server
User B sends a SIP 302 Moved Temporarily
message to the proxy server. The message
indicates that User B is not available at SIP
phone B. User B rewrites the contact-URI.
F4
ACK—Proxy Server to User B
The proxy server sends a SIP ACK to User B,
the ACK message notifies User B that the
proxy server has received the 302 Move
Temporarily message.
F5
302 Move Temporarily—Proxy
Server to User A
The proxy server forwards the 302 Moved
Temporarily message to User A.
F6
ACK—User A to Proxy Server
User A sends a SIP ACK to the proxy server.
The ACK message notifies the proxy server
that User A has received the 302 Move
Temporarily message.
F7
INVITE—User A to Proxy Server
User A sends a SIP INVITE request to the
proxy server. In the INVITE request, a
unique Call-ID is generated and the
Contact-URI field indicates that User A
requested the call.
F8
INVITE—Proxy Server to User C
The proxy server maps the SIP URI in the To
field to User C. The proxy server sends the
SIP INVITE request to User C.
F9
180 Ringing—User C to Proxy
User C sends a SIP 180 Ringing response to
the proxy server. The 180 Ringing response