This document describes how to construct and interpret certain
information in a PKIX-compliant (Public Key Infrastructure using
X.509) certificate for use in a Session Initiation Protocol (SIP)
over Transport Layer Security (TLS) connection. More specifically,
this document describes how to encode and extract the identity of a
SIP domain in a certificate and how to use that identity for SIP
domain authentication. As such, this document is relevant both to
implementors of SIP and to issuers of certificates. [STANDARDS-TRACK]