This document is ready from an ART perspective as it just updates the SIP Identity header field. 

Minor issues:
idnits calls out RFC 3375 as a downref.
The I-D's short title is "RFC4916 Update"; however, there is no mention of updating RFC 4916 in the document or in the document metadata. Is this intentional?

Nits:
I picked some nits (comma fixes, consistent use of "header field", etc. See https://github.com/ajeanmahoney/draft-ietf-stir-rfc4916-update/pull/2/files) and also converted the XML to v3. These updates can be found here if you would like to use them:  https://github.com/ajeanmahoney/draft-ietf-stir-rfc4916-update

Thanks!
Jean