Header                    Where    SUB NOT
------                    -----    --- ---
Accept                      R       o   o
Accept                     2xx      -   -
Accept                     415      o   o
Accept-Encoding             R       o   o
Accept-Encoding            2xx      -   -
Accept-Encoding            415      o   o
Accept-Language             R       o   o
Accept-Language            2xx      -   -
Accept-Language            415      o   o
Alert-Info                  R       -   -
Alert-Info                 180      -   -
Allow                       R       o   o
Allow                      2xx      o   o
Allow                       r       o   o
Allow                      405      m   m
Authentication-Info        2xx      o   o
Authorization               R       o   o
Call-ID                     c       m   m
Contact                     R       m   m
Contact                    1xx      o   o
Contact                    2xx      m   o
Contact                    3xx      m   m
Contact                    485      o   o
Content-Disposition                 o   o
Content-Encoding                    o   o
Content-Language                    o   o
Content-Length                      t   t
Content-Type                        *   *
CSeq                        c       m   m
Date                                o   o
Error-Info               300-699    o   o
Expires                             o   -
Expires                    2xx      m   -
From                        c       m   m
In-Reply-To                 R       -   -
Max-Forwards                R       m   m
Min-Expires                423      m   -
MIME-Version                        o   o
Organization                        o   -
Priority                    R       o   -
Proxy-Authenticate         407      m   m
Proxy-Authorization         R       o   o
Proxy-Require               R       o   o
RAck                        R       -   -
Record-Route                R       o   o
Record-Route           2xx,401,484  o   o
Reply-To                            -   -
Require                             o   o
Retry-After        404,413,480,486  o   o
Retry-After              500,503    o   o
Retry-After              600,603    o   o
Route                       R       c   c
RSeq                       1xx      o   o
Server                      r       o   o
Subject                     R       -   -
Supported                   R       o   o
Supported                  2xx      o   o
Timestamp                           o   o
To                         c(1)     m   m
Unsupported                420      o   o
User-Agent                          o   o
Via                         c       m   m
Warning                     R       -   o
Warning                     r       o   o
WWW-Authenticate           401      m   m