Yealink SIP-T48G [424/465] Unsuccessful call setup called user does not answer

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

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.