T-Lib-Initiated MakeCall re-INVITE

Description

UA1 calls UA2. If the UA1 endpoint does not support the REFER method, then the re-INVITE mechanism could be used. The main disadvantages of re-INVITE are:

• The phone may not reflect the real call progress unless early media is activated between both endpoints.
• Re-INVITE makes it next to impossible for third-party switches to track call topology and accumulate accurate call detail records (CDR).

Diagram