[Sip-implementors] Credentials in ACK

[Arunachalam Venkatraman]

In section 22.1 (page 194) of RFC3261, it is stated --   UACs creating an ACK message will duplicate all of the Authorization and Proxy-Authorization    header field values that appeared in the INVITE to which the ACK corresponds.   Q1: When a proxy sends an ACK to a non-2xx final response from a UAS, is it required for it to duplicate the mentioned headers from the INVITE? Since the proxy is playing the role of a UAC when sending an ACK, I would say yes.   Q2: Why is the language here not normative? Should it say "MUST duplicate" rather than "will duplicate"?