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Thread: Editorial question on MIME example




Editorial question on MIME example
country flaguser name
Sweden
2007-12-20 02:42:21
Hi,

I have an editorial (?) question on the MIME message body
example in
chapter 23.4.3 of 3261.


INVITE sip:bobbiloxi.com SIP/2.0
Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bKnashds8
To: Bob <sip:bobbiloxi.com>
From: Anonymous <sip:anonymousatlanta.com>;tag=1928301774
Call-ID: a84b4c76e66710
CSeq: 314159 INVITE
Max-Forwards: 70
Date: Thu, 21 Feb 2002 13:02:03 GMT
Contact: <sip:pc33.atlanta.com>
Content-Type:
multipart/signed;protocol="application/pkcs7-signature&
quot;;micalg=sha1;
boundary=boundary42
Content-Length: 568

--boundary42
Content-Type: application/pkcs7-mime;
smime-type=enveloped-data;name=smime.p7m
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename=smime.p7mhandling=required
Content-Length: 231

***********************************************************
* Content-Type: message/sip                               *
*                                                         *
* INVITE sip:bobbiloxi.com SIP/2.0                      
*
* Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bKnashds8 *
* To: Bob <bobbiloxi.com>                            
   *
Etc etc etc


Now, as far as I know (please correct me if I am wrong)
Content-Length
is NOT a MIME header. If so, I guess it shouldn't be used as
a MIME
header (together with Content-Type,
Content-Transfer-Encoding etc)?

Regards,

Christer


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RE: Editorial question on MIME example
country flaguser name
United States
2007-12-20 03:16:21
> Now, as far as I know (please correct me if I am wrong)
Content-Length
> is NOT a MIME header.

Right, it isn't.  It could be argued that SIP's
Content-Length was taken from
HTTP (RFC1945) rather than MIME.  It could be argued HTTP
took the idea from
email -- Content-Length used to be common in email headers a
decade or two ago
(but Content-Length didn't work too well for email for a
variety of reasons).
RFC2076 (February 1997) lists it, and says it was not a
standard email header
at the time.

> If so, I guess it shouldn't be used as a MIME
> header (together with Content-Type,
Content-Transfer-Encoding etc)?

RFC2045 does say:

   Any sort of field may be present in the header of an
entity,
   but only those fields whose names begin with
"content-" actually have
   any MIME-related meaning.

but of course Content-Length doesn't have any meaning to
MIME (neither would
Content-Crayon).  But neither of those headers do harm to a
MIME parser,
because a MIME parser ignores fields it doesn't understand.


I guess you're saying SIP should have used something like
"Length:" instead of
"Content-Length:" to avoid collision with MIME's
self-claimed ownership of all
field names that begin with "Content-"?

-d


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RE: Editorial question on MIME example
country flaguser name
Sweden
2007-12-20 03:30:20
Hi, 

>>Now, as far as I know (please correct me if I am
wrong) Content-Length

>>is NOT a MIME header.
> 
>Right, it isn't.  It could be argued that SIP's 
>Content-Length was taken from HTTP (RFC1945) rather than

>MIME.  It could be argued HTTP took the idea from email
-- 
>Content-Length used to be common in email headers a
decade or 
>two ago (but Content-Length didn't work too well for
email 
>for a variety of reasons).
>RFC2076 (February 1997) lists it, and says it was not a

>standard email header at the time.
> 
>>If so, I guess it shouldn't be used as a MIME header
(together with 
>>Content-Type, Content-Transfer-Encoding etc)?
> 
>RFC2045 does say:
> 
> Any sort of field may be present in the header of an
entity,
> but only those fields whose names begin with
"content-" 
> actually have any MIME-related meaning.
> 
>but of course Content-Length doesn't have any meaning to
MIME 
>(neither would Content-Crayon).  But neither of those
headers 
>do harm to a MIME parser, because a MIME parser ignores

>fields it doesn't understand.
> 
> 
>I guess you're saying SIP should have used something
like 
>"Length:" instead of
"Content-Length:" to avoid collision 
>with MIME's self-claimed ownership of all field names
that 
>begin with "Content-"?

No no.

I am not talking about the usage of Content-Lenght (or any
other
Content- header) in the SIP part of the message. I was
referring to the
usage of Content-Length in the MIME part of the message
body.

Regards,

Christer


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RE: Editorial question on MIME example
country flaguser name
United States
2007-12-20 11:07:02
> >I guess you're saying SIP should have used
something like 
> >"Length:" instead of
"Content-Length:" to avoid collision 
> >with MIME's self-claimed ownership of all field
names that 
> >begin with "Content-"?
> 
> No no.
> 
> I am not talking about the usage of Content-Lenght (or
any other
> Content- header) in the SIP part of the message. I was

> referring to the
> usage of Content-Length in the MIME part of the message
body.

Ah - thanks for clarifying.  So you are referring to the
second Content-Length
field in the example at http://to
ols.ietf.org/html/rfc3261#page-212 -- the
Content-Length field with the value 231.  I agree it
shouldn't be in that
example.  Looks like something to add to the Essential
Corrections.

-d


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RE: Editorial question on MIME example
country flaguser name
Sweden
2007-12-21 04:52:39
Hi, 

>>>I guess you're saying SIP should have used
something like "Length:" 
>>>instead of "Content-Length:" to avoid
collision with MIME's 
>>>self-claimed ownership of all field names that
begin with "Content-"?
>> 
>>No no.
>> 
>>I am not talking about the usage of Content-Lenght
(or any other
>>Content- header) in the SIP part of the message. I
was referring to 
>>the usage of Content-Length in the MIME part of the
message body.
> 
>Ah - thanks for clarifying.  So you are referring to the

>second Content-Length field in the example at 
>http://to
ols.ietf.org/html/rfc3261#page-212 -- the 
>Content-Length field with the value 231. 

Yes.

>I agree it shouldn't be in that example.  Looks like
something to add
to 
>the Essential Corrections.

Ok.

Thanks!

Regards,

Christer


_______________________________________________
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This list is for NEW development of the core SIP Protocol
Use sip-implementorscs.columbia.edu for questions on current
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