Re: [sipcore] Content-Length in multipart body parts

Hadriel Kaplan <HKaplan@acmepacket.com> Mon, 02 April 2012 22:21 UTC

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From: Hadriel Kaplan <HKaplan@acmepacket.com>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>, "Dale R (Dale) Worley" <dworley@avaya.com>
Thread-Topic: [sipcore] Content-Length in multipart body parts
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Date: Mon, 02 Apr 2012 22:21:38 +0000
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Subject: Re: [sipcore] Content-Length in multipart body parts
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Ugh.  Yeah, that's not good for examples to show.
So what's the solution?  Errata?

-hadriel
p.s. I like the "Suspicious Line" thing - all RFC lines are suspicious! ;)


On Apr 2, 2012, at 2:12 PM, Paul Kyzivat wrote:

> [reposting with a subject line]
> 
> On 4/2/12 6:53 PM, Worley, Dale R (Dale) wrote:
>> 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.  MIME does not define the meaining of such header fields, as the MIME
>> framing of body parts is done by the boundary markers.
>> 
>> As Dale Moberg has pointed out, these header fields might not be truly incorrect
>> but merely redundant or "to be ignored".
>> 
>> 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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>> 
> 
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