Administrator’s Guide for SIP-T4X IP Phones
410
The following figure illustrates the scenario of an unsuccessful call caused by the called
user’s no answering. In this scenario, the two end users are User A and User B. User A
and User B are located at Yealink SIP IP phones.
The call flow scenario is as follows:
1.
User A calls User B.
2.
User B does not answer the call.
3.
User A hangs up.
The call cannot be set up successfully.
User A
Proxy Server
User B
F1. INVITE B
F2. INVITE B
F3. 180 Ringing
F4. 180 Ringing
F8. 200 OK
F7. 200 OK
F5. CANCEL
F6. CANCEL
Step
Action
Description
F1
INVITE—User A to Proxy
Server
User A sends an INVITE message to a
proxy server. The INVITE request is an
invitation to User B to participate in a
call session.
In the INVITE request:
The IP address of User B is inserted
in the Request-URI field.
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.
Summary of Contents for SIP-T4X
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