Hi, I did the OPS directorate review for this document.

   As far as I can tell, there are no operational or network management
   related issues with this document.

   the document normatively updates the RFC 3261, which defines the
   Session Initiation Protocol (SIP): It changes the usage of the Alert-
   Info header field defined in the RFC 3261 by additionally allowing
   its use in all provisional responses to INVITE (except the 100
   response).

   As such it specifies a URN Specification for the "alert"  Namespace Identifier
   It creates a new registry to be maintained by IANA and sets the rules for that
   registry.

Bert