The SIP REFER method is described in RFC 3515 which says in part:
This document defines the REFER method. This Session Initiation Protocol (SIP) extension requests that the recipient REFER to a resource provided in the request. It provides a mechanism allowing the party sending the REFER to be notified of the outcome of the referenced request. This can be used to enable many applications, including call transfer.
In addition to the REFER method, this document defines the refer event package and the Refer-To request header.
SIP Refer is used for call transfers, for example, the Asterisk Call Transfer command uses SIP Refer.
Resources
- Draft RFC Session Initiation Protocol Call Control – Transfer – Documents SIP Transfer Call Flows
- RFC 5359 “Session Initiation Protocol Service Examples” – Documents SIP call flows including transfer
- RFC 4488 “Suppression of Session Initiation Protocol (SIP) REFER Method Implicit Subscription”
- A VoIP Emergency Services Architecture and Prototype – Discusses using SIP REFER for call handling
December 2, 2021
Phone System 