Subject: [Sip] Additional uses of INFO

From: "Drage, Keith (Keith)" <[email-masked]>
Date: Wed, 14 Jun 2006 10:36:15 +0100

Within the SIP protocol we have done a lot of tidying up as to how extensions are made to the SIP protocol.

In particular RFC 3968 and RFC 3969 set up various registries for the session initiation protocol, and RFC 3427 defines rules for definition of headers and event packages.

Both within IETF, and in discussions outside IETF, we still see proposals to use the INFO method (RFC 2976) for various purposes, and we have no really clear statements on whether INFO method can be applied to new applications, or not, and if so, who should document those new applications. This is probably complicated by the fact that the INFO RFC

http://www.ietf.org/internet-drafts/draft-rosenberg-sip-hitchhikers-guide-00.txt currently lists RFC 2976 under the PSTN interworking specifications, and that is currently the only defined IETF usage, and also indicates under the general infrastructure section:

RFC 2976: The INFO Method (S) RFC 2976 [39] was defined as an
      extension to RFC 2543.  It defines a method, INFO, used to
      transport mid-dialog information that has no impact on SIP itself.
      Its driving application was the transport of PSTN related
      information when using SIP between a pair of gateways.  Though
      originally conceived for broader use, it only found standardized
      usage with SIP-T [33].  It has been used to support numerous
      proprietary and non-interoperable extensions due to its poorly
      defined scope.

My question is whether it is appropriate to provide some means of clarifying other usages of the INFO method, and who should document them. Should that occur in:

i)	An update or revision to RFC 2976
ii)	An update to RFC 3427
iii)	Anywhere else

regards

Keith

Keith Drage
[email-masked]
tel: +44 1793 776249

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 14 Jun 2006 12:02:31 -0400

Well, my opinion on INFO is that its an exceptionally poor vehicle for
doing extensions. A long while back, I wrote an I-D called "INFO
considered harmful" which summarized my thinking on this:

http://www.jdrosen.net/papers/draft-rosenberg-sip-info-harmful-00.txt

The conclusion of the document is that we should limit INFO to its only
defined usage - for ISUP transport - and I still think this conclusion 
makes sense.

Thanks,
Jonathan R.

Drage, Keith (Keith) wrote:

> In particular RFC 3968 and RFC 3969 set up various registries for the
> session initiation protocol, and RFC 3427 defines rules for
> definition of headers and event packages.
> 
> Both within IETF, and in discussions outside IETF, we still see
> proposals to use the INFO method (RFC 2976) for various purposes, and
> we have no really clear statements on whether INFO method can be
> applied to new applications, or not, and if so, who should document
> those new applications. This is probably complicated by the fact that
> the INFO RFC
> 
> http://www.ietf.org/internet-drafts/draft-rosenberg-sip-hitchhikers-guide-00.txt
> currently lists RFC 2976 under the PSTN interworking specifications,
> and that is currently the only defined IETF usage, and also indicates
> under the general infrastructure section:
> 
> extension to RFC 2543.  It defines a method, INFO, used to transport
> mid-dialog information that has no impact on SIP itself. Its driving
> application was the transport of PSTN related information when using
> SIP between a pair of gateways.  Though originally conceived for
> broader use, it only found standardized usage with SIP-T [33].  It
> has been used to support numerous proprietary and non-interoperable
> extensions due to its poorly defined scope.
> 
> My question is whether it is appropriate to provide some means of
> clarifying other usages of the INFO method, and who should document
> them. Should that occur in:
> 
> i)	An update or revision to RFC 2976 ii)	An update to RFC 3427 iii)
> Anywhere else
> 
> regards
> 
> Keith
> 
> Keith Drage [email-masked] tel: +44 1793 776249
> 
> _______________________________________________ Sip mailing list
> https://www1.ietf.org/mailman/listinfo/sip This list is for NEW
> development of the core SIP Protocol Use
> [email-masked] for questions on current sip Use
> [email-masked] for new developments on the application of sip
> 

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

---

From: Dean Willis <[email-masked]>
Date: Wed, 14 Jun 2006 11:31:38 -0500

And now, for a view from the other side of the peanut gallery:

I think INFO is potentially a great mechanism for exchanging  
structured data  within dialog-bounded applications (perhaps not  
extensions -- I don't agree that every new application should require  
a new extension), but that we've harnessed the power of that  
mechanism poorly.

Currently, we lack both a mechanism for describing the usage of INFO,  
and a mechanism for negotiating that usage between nodes. If we were  
to do anything further with it, it might make sense to emulate the  
model of event packages, which so far seems to have worked well enough.

I proposed this in:

http://www.softarmor.com/wgdb/docs/draft-willis-sip-infopackage-00.txt

I personally think it's a really BAD idea to keep introducing new SIP  
extensions that just shuttle blobs of stuff between UAs. We need only  
one extension for this, and a way of cleanly declaring what the stuff  
is and what should be done with it and of finding out whether a  
correspondent would understand that declaration. And yes, I think  
MESSAGE is pretty much just INFO with its name changed to protect the  
innocent.

--
Dean

On Jun 14, 2006, at 11:02 AM, Jonathan Rosenberg wrote:

> defined usage - for ISUP transport - and I still think this  
> conclusion makes sense.
>
>