According to RFC 3261, the following is stated in section 12.2.1.1:
A UAC SHOULD include a Contact header field in any target refresh requests
within a dialog, and unless there is a need to change it, the URI SHOULD be
the same as used in previous requests within the dialog.  If the "secure"
flag is true, that URI MUST be a SIPS URI.As discussed in Section 12.2.2, a
Contact header field in a target refresh request updates the remote target
URI.  This allows a UA to provide a new contact address, should its address
change during the duration of the dialog.

This seems to indicate that including the Contact header in a target refresh
request (ie, Re-INVITE or UPDATE) is only a strong recommendation (ie,
"SHOULD" vs "MUST").

However, table 3 in section 20 of RFC3261 seems to contradict this, as it
lists the Contact header as "m":
Header field              where       proxy ACK BYE CAN INV OPT REG
___________________________________________________________________
Contact                      R                      o       -      -
m     o      o

Also, table 1 in section 8 of RFC3311 lists the Contact header as "m" for
the UPDATE request.

Is there any consensus as to which is considered the correct statement? MUST
the Contact header be included in target refresh requests(as indicated by
the header tables in RFC3261 and RFC3311)? Or, SHOULD the Contact header be
included in the target refresh request(as indicated by section 12.2.1.1 of
RFC3261)?

Thanks in advance for any input, insight, or clarification.
John D. Roan
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