Bruno Chatras has pointed out that a number of examples in various SIP-related
RFCs show Content-Length header fields in the headers of body-parts of multipart
entities.  As Dale Moberg has pointed out, that might not be truly incorrect.
But given that MIME multipart already frames the body-parts, Content-Length
headers on body-parts are never necessary.

So it seems to me that we should decide on a "best practices" for the use of
Content-Length in the headers of a body part, to clarify the ambiguities in the
specifications, and to state whether it's preferable to include such a 
Content-Length
or not.

I've appended a list of all the examples carrying such Content-Length headers
that I could find by automated means.

Dale
--------------------------------------------------------------------------------------------------------
RFC 2848

                       The PINT Service Protocol:
   Extensions to SIP and SDP for IP Access to Telephone Call Services

Suspicious line at rfc2848.txt:2195:       Content-Length: 236
Suspicious line at rfc2848.txt:2209:       Content-Length:50
Suspicious line at rfc2848.txt:2268:       Content-Length: 316
Suspicious line at rfc2848.txt:2284:       Content-Length: 172
Suspicious line at rfc2848.txt:2372:    Content-Length: 325
Suspicious line at rfc2848.txt:2387:    Content-Length: 352

Several of these body-part headers are not separated from the
body-part contents by CR-LF-CR-LF.

RFC 3261

                    SIP: Session Initiation Protocol

Suspicious line at rfc3261.txt:11846:         Content-Length: 231

RFC 3892

      The Session Initiation Protocol (SIP) Referred-By Mechanism

Suspicious line at rfc3892.txt:642:       Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:687:       Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:702:       Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:879:       Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:887:       Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:938:       Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:964:       Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:972:       Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:1056:      Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:1106:      Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:1168:      Content-Length: (appropriate value)
Suspicious line at rfc3892.txt:1196:      Content-Length: (appropriate value)

RFC 3893

                   Session Initiation Protocol (SIP)
                Authenticated Identity Body (AIB) Format

Suspicious line at rfc3893.txt:249:    Content-Length: 147
(This has an extra CR-LF before the body-part headers.)
Suspicious line at rfc3893.txt:263:    Content-Length: 608

RFC 4463

                A Media Resource Control Protocol (MRCP)
              Developed by Cisco, Nuance, and Speechworks

Suspicious line at rfc4463.txt:1705:        Content-Length:176
Suspicious line at rfc4463.txt:1714:        Content-Length:104
Suspicious line at rfc4463.txt:2977:       Content-Length:176
(Also missing the CR-LF after the body part headers.)
Suspicious line at rfc4463.txt:2985:       Content-Length:104

RFC 5547

      A Session Description Protocol (SDP) Offer/Answer Mechanism
                        to Enable File Transfer

Suspicious line at rfc5547.txt:1645:    Content-Length: [length of SDP]
Suspicious line at rfc5547.txt:1670:    Content-Length: [length of image]
Suspicious line at rfc5547.txt:2093:    Content-Length: [length of SDP]
Suspicious line at rfc5547.txt:2118:    Content-Length: [length of image]

RFC 5589

       Session Initiation Protocol (SIP) Call Control - Transfer

Suspicious line at rfc5589.txt:2609:    Content-Length: 2961
(An extra CR-LF in the middle of the body part headers.)
Suspicious line at rfc5589.txt:2677:    Content-Length: 156
(An extra CR-LF in the middle of the body part headers.)
Suspicious line at rfc5589.txt:2696:    Content-Length: 2961

RFC 6086

  Session Initiation Protocol (SIP) INFO Method and Package Framework

Suspicious line at rfc6086.txt:1594:    Content-length: 59
Suspicious line at rfc6086.txt:1620:    Content-length: 59
Suspicious line at rfc6086.txt:1637:    Content-length: 59
Suspicious line at rfc6086.txt:1664:    Content-length: 59

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