1.3 Overview

This protocol specifies the authentication extensions to Session Initiation Protocol (SIP). This protocol defines NT LAN Manager (NTLM), Kerberos, and Transport Layer Security with Derived Session Key (TLS-DSK) authentication schemes based on the general authentication framework described in [RFC3261], where the authentication mechanism is extended as described in Protocol Overview (section 3.1). This protocol also specifies the details and extensions for the Asserted Identity mechanism, which is based on [RFC3325], and the Referred-By mechanism, which is based on [RFC3892].