Session Initiation Protocol (SIP) Extension Header Field for Service Route Discovery During Registration

Abstract

This document defines a Session Initiation Protocol (SIP) extension header field used in conjunction with responses to REGISTER requests to provide a mechanism by which a registrar may inform a registering user agent (UA) of a service route that the UA may use to request outbound services from the registrar's domain.

Guidelines for Using the Privacy Mechanism for SIP

“…Service-Route headers [RFC3608] appear only in 200 OK responses to REGISTER requests and contain information about the registrar. The purpose of the privacy mechanism defined in RFC 3323 is to secure the user's privacy, so the case where a registrar sets a Privacy header is not considered here.…”

Obtaining and Using Globally Routable User Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)

“…If the user agents support the service-route mechanism [23], the registrar can implement it and return a service route that points to the authoritative proxy. This will cause requests originated by the user agent to pass through the authoritative proxy.…”

Addressing Record-Route Issues in the Session Initiation Protocol (SIP)

“…The serious drawbacks of the rewriting technique explain why the double Record-Routing solution has consequently been recommended in SIP extensions like [RFC3486] or [RFC3608].…”

“…- [RFC3608], Section 6.2, recommends the usage of double RecordRouting instead of the rewriting solution described in [RFC3261] for "Dual-homed" proxies. Those are defined as "proxies connected to two (or more) different networks such that requests are received on one interface and proxied out through another network interface".…”

“…The observed interoperability problems can be explained by the fact that, despite these multiple documents, the RFC 3261 description has not been changed, and many implementations don't support extensions like Service-Route ( [RFC3608]) or SIGCOMP ( [RFC3486]). …”