RE: [Sip] Question on RFC3840/3841

"Christer Holmberg" <christer.holmberg@ericsson.com> Thu, 10 January 2008 14:42 UTC

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Subject: RE: [Sip] Question on RFC3840/3841
Date: Thu, 10 Jan 2008 15:42:14 +0100
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Thread-Topic: [Sip] Question on RFC3840/3841
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From: "Christer Holmberg" <christer.holmberg@ericsson.com>
To: "Paul Kyzivat" <pkyzivat@cisco.com>, "Mahesh Anjanappa" <mahesha@samsung.com>
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Paul,

Regarding the matching, are you saying that reading RFC3840 is enough to
understand how the matching is done in a "SIP environment"? Or, do I
also need to read RFC2533?

I have some questions on the matching, but I will come back to them
later. I still have some reading to do.

Regards,

Christer

 

> -----Original Message-----
> From: Paul Kyzivat [mailto:pkyzivat@cisco.com] 
> Sent: 10. tammikuuta 2008 16:21
> To: Mahesh Anjanappa
> Cc: Christer Holmberg; sip@ietf.org
> Subject: Re: [Sip] Question on RFC3840/3841
> 
> 
> 
> Mahesh Anjanappa wrote:
> > Yes the ';' is a mistake. But i'm not sure if  each Contact should 
> > contain "alice@atlanta.com"
> 
> Well, it has to have a URI to be syntactically correct.
> 
> Your problem is that you are trying to express something that 
> cannot be expressed with the callee caps syntax. It only maps 
> to a subset of the syntax supported by RFC 2533.
> 
> > because the predicate that i'm trying to represent is as follows 
> > meanig to say alice supports a communication which whose 
> capability is 
> > Duplex Audio + One Way Video.
> 
> You just can't say that. Sorry.
> 
> A little history may help you to understand, though it won't 
> solve your
> problem:
> 
> The initial draft for callerprefs came out a very long time 
> ago. (The earliest draft I have is -03 which came out in 
> november of 2000.) It set the basic syntax and the initial 
> set of capabilities.
> 
> It was however very weak on the semantics of matching. I 
> eventually got involved because I was interested in it and 
> identified many of the semantic issues. Jonathan and I worked 
> on it for a long time. 
> Eventually, because of some review comments I think, Jonathan 
> tried to define the semantics using RFC 2533 because it was a 
> standard that seemed to be at least partially suitable to the 
> task. (In retrospect this may not have been such a good idea, 
> since it adds an additional layer of complexity.)
> 
> RFC 2533 syntax is much richer. But it was not a goal to 
> provide that richness. (Mapping that all onto SIP header 
> syntax would be awful.) It was only used as an intermediate 
> form to define the semantics of the SIP headers.
> 
> Its understood that there are lots of things one might want 
> to express that you can't express.
> 
> If you aren't already aware of it, you might want to look at 
> RFC 4596 (Guidelines for Usage of the Session Initiation 
> Protocol (SIP) Caller Preferences Extension).
> 
> 	Paul
> 
> > If each of the COntact contains alice@atlanta.com wouldnt it be 
> > interpreted as " alice supports duplex audio and oneway video 
> > separatley and not both at the same time".
> > Actually i'm not quite sure how to represesnt the predicate in the 
> > Contact header correctly, hence my Queries. It all stems from the 
> > statement which you too noted " There MUST only be one 
> instance of any 
> > feature tag in feature-param." in RFC 3840
> > 
> > 
> > Predicate:
> > ------------
> > & ( & (sip.audio) (sip.duplex=full) )
> >    (  & (sip.video) (sip.duplex=receive-only) )
> > 
> > regards
> > Mahesh
> > ----- Original Message ----- From: "Christer Holmberg" 
> > <christer.holmberg@ericsson.com>
> > To: "Mahesh Anjanappa" <mahesha@samsung.com>om>; "Paul Kyzivat" 
> > <pkyzivat@cisco.com>
> > Cc: <sip@ietf.org>
> > Sent: Thursday, January 10, 2008 11:30 AM
> > Subject: RE: [Sip] Question on RFC3840/3841
> > 
> > 
> > 
> > Shouldn't each Contact also contain "alice@atlanta.com"?
> > 
> > Also, why do you have ";" at the end of each Contact?
> > 
> > Regards,
> > 
> > Christer
> > 
> > 
> > 
> >> -----Original Message-----
> >> From: Mahesh Anjanappa [mailto:mahesha@samsung.com]
> >> Sent: 10. tammikuuta 2008 6:16
> >> To: Paul Kyzivat
> >> Cc: sip@ietf.org; Christer Holmberg
> >> Subject: Re: [Sip] Question on RFC3840/3841
> >>
> >> hi Paul,
> >> Sorry there is a mistake in Contact header i
> >> described.Following is what i wanted to:
> >> Contact:sip:alice@atlanta.com;
> >> Contact:audio;duplex=full;
> >> Contact:video;duplex=recieve-only;
> >>
> >> Thanks
> >> Mahesh
> >> ----- Original Message -----
> >> From: "Mahesh Anjanappa" <mahesha@samsung.com>
> >> To: "Paul Kyzivat" <pkyzivat@cisco.com>
> >> Cc: <sip@ietf.org>rg>; "Christer Holmberg"
> >> <christer.holmberg@ericsson.com>
> >> Sent: Wednesday, January 09, 2008 10:48 PM
> >> Subject: Re: [Sip] Question on RFC3840/3841
> >>
> >>
> >> > Thanks Paul.
> >> > So would it be right if i have a Contact Headers describing
> >> Duplex Audio &
> >> > one-way Video Capabilities as follows?
> >> >
> >> >    Contact:sip:alice@atlanta.com;
> >> >    Contact:sip:audio;duplex=full;
> >> >    Contact:sip:video;duplex=recieve-only;
> >> >
> >> > NOTE: The Predicate(for above) for which i'm attempting is
> >> > & ( & (sip.audio) (sip.duplex=full) )
> >> >    (  & (sip.video) (sip.duplex=receive-only) )
> >> >
> >> > regards
> >> > Mahesh
> >> >
> >> > ----- Original Message ----- > From: "Paul Kyzivat" 
> >> <pkyzivat@cisco.com>
> >> > To: "Mahesh Anjanappa" <mahesha@samsung.com>
> >> > Cc: "Christer Holmberg" <christer.holmberg@ericsson.com>om>;
> >> <sip@ietf.org>
> >> > Sent: Wednesday, January 09, 2008 7:55 PM
> >> > Subject: Re: [Sip] Question on RFC3840/3841
> >> >
> >> >
> >> >>
> >> >>
> >> >> Mahesh Anjanappa wrote:
> >> >>> hi
> >> >>> That is my understanding as well. But if that is the case
> >> then it should
> >> >>> apply to Contact header as well
> >> >>> when describing Capabilities using Feature parameters in
> >> Contact Header.
> >> >>> But i'm not sure if it applies the same way. I had posted
> >> this question
> >> >>> long ago but didnt get any comments on it.
> >> >>
> >> >> The rule forbidding multiple instances of a parameter
> >> applies to all
> >> >> headers, so it applies to Contact.  E.g. the following 
> is illegal:
> >> >>
> >> >> Contact:sip:alice@atlanta.com;methods="INVITE";methods="CANCEL"
> >> >>
> >> >> Paul
> >> >
> >> >
> >> >
> >> > _______________________________________________
> >> > Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
> >> > This list is for NEW development of the core SIP Protocol
> >> > Use sip-implementors@cs.columbia.edu for questions on current sip
> >> > Use sipping@ietf.org for new developments on the 
> application of sip
> >>
> >>
> > 
> > 
> 


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