Subject: RE: [Sip] CSCF - 3GPP IMS question about unknown header

From: "Drage, Keith (Keith)" <[email-masked]>
Date: Sat, 7 Sep 2002 00:08:07 +0100

Depending on whose storyline you read 3GPP CSCFs are either proxies, or B2BUAs, or some horrible and illegal mismash of both. Different types of CSCFs fall into different categories. 

As Dean says, proxies relay unknown headers from one side to the other.

RFC 3261 does not define the transfer characteristics of B2BUAs. While UASs are required to ignore unrecognized headers received in requests, this appears to be specified such that the request gets processed by the UAS despite the header. It would therefore appear to be legal to pass the unrecognized header to the B2B UAC for transmission at the outgoing side. For responses I guess similar arguments would apply.

So in summary, those 3GPP entities that behave as proxies will pass on; those 3GPP entities that behave as B2BUAs may (and in practice probably will); those that are argued to be neither one or the other will do one or the other.

Note that the sipchanges draft says that there is no such thing as a company defined proprietary header. All proprietary headers are defined in internet drafts --> informational RFCs. Therefore by a stroke of publication they will all cease to exist!

Keith

Keith Drage
Lucent Technologies
Tel: +44 1793 776249
Email: [email-masked] 

> -----Original Message-----
> From: Dean Willis [mailto:[email-masked]]
> Sent: 06 September 2002 21:10
> To: 'e e'; [email-masked]
> Subject: RE: [Sip] CSCF - 3GPP IMS question about unknown header
> 
> 
> 
> This would properly be a question for 3GPP, not IETF.
> 
> SIP proxies compliant to RFC 3261 will pass the unknown header along
> unmodified.
> 
> Whether or not the 3GPP x-CSCFs will be RFC3261 compliant proxies or
> some kind of user agent will be determined by 3GPP. 
> 
> My initial guess at a response might be "it depends -- which 
> x-CSCF are
> you talking about, and in which operator's network?"
> 
> --
> dean
> 
> > -----Original Message-----
> > From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of e e
> > Sent: Friday, September 06, 2002 9:43 AM
> > To: [email-masked]
> > Subject: [Sip] CSCF - 3GPP IMS question about unknown header
> > 
> > 
> > 
> > Hello to everybody,
> > I need some help.
> > Does anyone know which is the behaviour of CSCF (P-CSCF, 
> > I-CSCF and S-CSCF) 
> > of 3GPP IMS when these entities try to process an unknown 
> > header (e.g. a 
> > proprietary header specified by a company) ?
> > Do they threat such messages just ignoring the header and 
> > proceeding in the 
> > standard way?
> > 
> > Thank you in advance,
> > 
> > Peter
> > 
> > 
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