The Session Initiation Protocol (sip) Referred-by Mechanism

Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract The Session Initiation Protocol (SIP) REFER method provides a mechanism where one party (the referrer) gives a second party (the referee) an arbitrary URI to reference. If that URI is a SIP URI, the referee will send a SIP request, often an INVITE, to that URI (the refer target). This document extends the REFER method, allowing the referrer to provide information about the REFER request to the refer target using the referee as an intermediary. This information includes the identity of the referrer and the URI to which the referrer referred. The mechanism utilizes S/MIME to help protect this information from a malicious intermediary. This protection is optional, but a recipient may refuse to accept a request unless it is present. The SIP REFER method [2] provides a mechanism where one party (the referrer) provides a second party (the referee) with an arbitrary URI to reference. If that URI is a SIP URI, the referee will send a SIP request, often an INVITE, to that URI (the refer target). Nothing provided in [2] distinguishes this referenced request from any other request the referee might have sent to the refer target.