Header field          where   PRACK
___________________________________
Accept                  R       o
Accept                 2xx      -
Accept                 415      c
Accept-Encoding         R       o
Accept-Encoding        2xx      -
Accept-Encoding        415      c
Accept-Language         R       o
Accept-Language        2xx      -
Accept-Language        415      c
Alert-Info              R       -
Alert-Info             180      -
Allow                   R       o
Allow                  2xx      o
Allow                   r       o
Allow                  405      m
Authentication-Info    2xx      o
Authorization           R       o
Call-ID                 c       m
Call-Info                       -
Contact                 R       -
Contact                1xx      -
Contact                2xx      -
Contact                3xx      o
Contact                485      o
Content-Disposition             o
Content-Encoding                o
Content-Language                o
Content-Length                  t
Content-Type                    *
CSeq                    c       m
Date                            o
Error-Info           300-699    o
Expires                         -
From                    c       m
In-Reply-To             R       -
Max-Forwards            R       m
Min-Expires            423      -
MIME-Version                    o
Organization                    -