Re: [sipcore] Feature-tags in the Path header field
Christer Holmberg <christer.holmberg@ericsson.com> Fri, 17 September 2010 13:18 UTC
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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Paul Kyzivat <pkyzivat@cisco.com>
Date: Fri, 17 Sep 2010 15:19:18 +0200
Thread-Topic: [sipcore] Feature-tags in the Path header field
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Cc: "sipcore@ietf.org" <sipcore@ietf.org>
Subject: Re: [sipcore] Feature-tags in the Path header field
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Hi, >Didn't somebody else already bring this up a few months ago? In that case I missed it :) >IIUC, you are asking if Path can be used with a new parameter >without any further standards action. Is that right? At this point I am asking about the usage of feature tags to indicate proxy features in general. Whether it would require some standards actions needs to be checked. >If I go back to the definition of Path in 3327, I find that >it allows multiple parameters of type "rr-param". It doesn't >define rr-param, but does say the Path header field values >must conform to the syntax of the Path element from 3261, >which defines rr-param as generic-param. > >So *syntactically* you can put whatever parameters you want >in there, and sip parsers should not be troubled. But >legalistically, new parameters can only be introduced via >standards action. Correct. >From a pure syntax perspective it is not a problem. But, for Contact, A-C, R-C and Refer-To we have defined "feature-param", which in this case would be an explicit usage of "rr-param". >I suspect the problem 3gpp is trying to address may be of >more general interest. But its hard to decipher from your >brief description. Can you provide a more complete >description of the problem and the proposed solution? For >instance, diagrams of the signaling and media paths before >and after the handoff of the call. Well, I was trying to keep the handover description as short as possible, because the intention was not to discuss it. But, for sure I can provide references if people want to read the details. The idea was to provide some background information to show that there is a problem, to avoid questions like "You have a solution - where is the problem?" :) I do, however, agree that the possibility to provide proxy features may be of more general interest, and that is also one reason I raised this issue on the list. Regards, Christer > On 9/17/2010 7:17 AM, Christer Holmberg wrote: > > Hi, > > Introduction: > > ----------------- > > 3GPP is working on solution which improves the ability to > be able to > > move an ongoing IMS call from an IP based access network to > a legacy > > CS based network without dropping the call. > > The solution requires a media anchoring proxy (called ATCF) in the > > visited network, and a signaling anchoring application > server (called > > SCC AS) in the users home network. > > Problem: > > ------------ > > The SCC AS, when it receives a REGISTER request from a UA, needs to > > know whether there is a proxy with ATCF functionaltiy in the > > registration path. The reason is that the SCC AS can then choose to > > delegate session handover functionality to the ATCF, which provides > > advantages related to voice interruption etc. > > Possible solution: > > ------------------------- > > During registration the ATCF inserts a Path header field, so a > > solution to indicate its support of the ATCF functionlaity > would be to > > insert a feature tag in the Path header field. > > However, eventhough there is no syntax issue, the usage of feature > > tags have only been specified for the Contact, Accept-Contact, > > Reject-Contact and Refer-To header fields. > > So, the question is whether there are any reasons why the > proxy could > > not use a feature tag in the Path header field for this. > Entities that > > don't support the feature will simply see it as an unsupported Path > > header field parameter, and a registrar doing normal feature tag > > matching shouldn't even look at the Path header field. And, > based on > > the feature tag definitions in RFC3840 and RFC2703, we > don't think the > > usage is necessarily limited to UAs Regards, Christer > > > > > > > > _______________________________________________ > > sipcore mailing list > > sipcore@ietf.org > > https://www.ietf.org/mailman/listinfo/sipcore >
- [sipcore] Feature-tags in the Path header field Christer Holmberg
- Re: [sipcore] Feature-tags in the Path header fie… Paul Kyzivat
- Re: [sipcore] Feature-tags in the Path header fie… Christer Holmberg
- Re: [sipcore] Feature-tags in the Path header fie… Paul Kyzivat
- Re: [sipcore] Feature-tags in the Path header fie… Christer Holmberg
- Re: [sipcore] Feature-tags in the Path header fie… Paul Kyzivat
- Re: [sipcore] Feature-tags in the Path header fie… Christer Holmberg
- Re: [sipcore] Feature-tags in the Path header fie… Paul Kyzivat
- Re: [sipcore] Feature-tags in the Path header fie… Christer Holmberg
- [sipcore] Draft new: draft-holmberg-sipcore-proxy… Christer Holmberg
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Paul Kyzivat
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Elwell, John
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Christer Holmberg
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Peter Musgrave
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Hadriel Kaplan
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Hadriel Kaplan
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Christer Holmberg
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Hadriel Kaplan
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Leis, Peter (NSN - DE/Munich)
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Christer Holmberg
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Leis, Peter (NSN - DE/Munich)
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… gao.yang2
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… DRAGE, Keith (Keith)
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… gao.yang2
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Andrew Allen
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Andrew Allen
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Dean Willis
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Dean Willis
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Christer Holmberg
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Dean Willis
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… R.Jesske
- Re: [sipcore] Draft new: draft-holmberg-sipcore-p… Christer Holmberg
- [sipcore] draft-holmberg-sipcore-proxy-feature- w… Cullen Jennings
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… Paul Kyzivat
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… Andrew Allen
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… Christer Holmberg
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… Hadriel Kaplan
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… Shida Schubert
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… Worley, Dale R (Dale)
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… Leis, Peter (NSN - DE/Munich)
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… Christer Holmberg
- Re: [sipcore] draft-holmberg-sipcore-proxy-featur… hannu.hietalahti