Yeah, but I think we do have to recognize there really are use cases that are simply wrong to do using INFO. There's nothing the IETF or anyone can do to stop people from doing them (there's no RFC interpol), but that doesn't mean we should give them explicit blessing either, and a draft such as Eric's really is the best we can do if we can't find legitimate use cases. That's why I like Jonathan's proposal for finding good use-cases, which is what I wanted to say at the mic at the end of that debate.
There is, though, another aspect to this. As we all know, interoperability is a major SIP issue, and even if we discourage INFO use we know it will be used. So an unresolved question in my mind is whether we should define at least how such proprietary use can be signaled, to avoid vendor-specific static configuration profile proliferation making interop harder. In other words: not accept draft proposals for INFO use, not be bothered with repeating these discussions anymore in the IETF, etc.; but at least give them a standardized way to negotiate it so their UAs can interoperate with legitimate IETF-following UAs without needing configuration. -hadriel > -----Original Message----- > From: Christer Holmberg [mailto:[EMAIL PROTECTED] > Sent: Thursday, December 06, 2007 8:22 PM > To: Ganesan Sam-W00184; Hadriel Kaplan; [email protected] > Subject: VS: [Sip] INFO use-cases > > Hi, > > Use-case 1: > ----------------- > > One use-case is the transport of user-to-user information, and the reasons > people don't think it's feasible to establish a media plane connection for > this are (at least): > > 1. The information will not be sent for every call, and when sent the > amount of information is relatively small > 2. In interworking cases the information may be received out-of-band from > the "other side", so it is seen as unfeasible to send it down to the MG - > in some cases the interworking may even be performed without a MG. > > > Use-case 2: > ----------------- > > Pretty much the same arguments are also used for sending DTMF out-of-band. > In addition there may be intermediate entities, without media access, > which are interested in the DTMF information. > > > (I hope we have understood the arguments why people want to use INFO > instead of SUB/NOT, so I will not go into that again.) > > Regards, > > Christer > > ________________________________ > > Lähettäjä: Ganesan Sam-W00184 [mailto:[EMAIL PROTECTED] > Lähetetty: pe 7.12.2007 1:46 > Vastaanottaja: Hadriel Kaplan; [email protected] > Aihe: RE: [Sip] INFO use-cases > > > I also know of a use case where video npt bookmarks are sent over INFO > across the SIP path while using SIP for video stream set up. Tispan 3 is > actually writing specs on this and so is ATIS... > > > Sam > > ________________________________ > > From: Hadriel Kaplan [mailto:[EMAIL PROTECTED] > Sent: Thu 12/6/2007 6:38 PM > To: [email protected] > Subject: [Sip] INFO use-cases > > > > Howdy, > Jonathan asked for use-cases for what types of things would need an in- > dialog SIP message for user-user communication, vs. should be done either > out of dialog or in the media plane. If the only use-case is DTMF, then > we could just document the DTMF negotiation/use only and not have to > create a general info-events framework. That seems a very reasonable > argument to me. I also don't want to do work for no use. > > There is a counter-argument that there are proprietary uses of INFO in the > wild, and that a framework for negotiation at least removes the manual > configuration of vendor-specific profiles, which is a problem of interop > today - even if the IETF should not bless/document the specific use cases > themselves. But that would make the draft a very different one than it > currently is as well, and I will ask that in a separate email thread. > > The chairs have asked for 3 use cases, and I assume they mean 3 NEW use > cases (we already have 3 RFCs which use INFO, as well as DTMF). I am not > sure if they mean potential future use-cases, or current use-cases (i.e., > already implemented). Can I get a clarification on that? > > So anyway, taking the shot-gun approach, here's a first go at some use- > cases, and my personal take on whether they should be in INFO vs. SUB/NOT > vs. media-plane, FWIW. > [apologize for formatting ugliness] > > /*************** > * Already standardized use-cases: > ***************/ > 1) SIP-T/ISUP/QSIG/PSTN > -Documented in RFC 3372 and RFC 4497. > > 2) ECMA TR/87 uaCSTA > -Uses INFO to send ECMA-323 XML for monitoring and controlling > phones from a PC. > > 3) Sending media server control commands. > -Documented in RFC4722 MSCML. > > > /**************** > * Use-cases that I think are potentially/possibly valid for INFO: > ****************/ > 1) Sending a vcard asynchronously. Alice calls Bob, Alice says "can you > send me John's vcard?", Bob clicks something and voila it's sent. > -Alternatives: send a re-Invite or Update with a Call-Info, with > either a URL reference, data URI, or MIME and CID URL. > -Counter-argument: IMO this type of data really belongs in MIME > for a number of reasons, including length is less restricted for mime > attachments; one AD has said the Data URL may be deprecated. And sending > a re-Invite for this purpose seems odd. > > -Also, the Call-Info header is really about the caller or callee, > and thus Bob shouldn't be sending me John's vcard info in it technically. > That may sound like a nit, but UA's may well store the call-info vcards > into their address-books automatically and so tie it to the wrong > user/call. > -Pros of using INFO: it's explicit what you're doing when you send > the vcard, and you can send it knowing the other end can accept it, and > you can send it based on user input. > > 2) Sending a user-icon jpeg/bitmap/gif. Alice calls Bob, Bob has an icon > that represents himself, sends it when he picks up the phone. > -Alternatives: send a 200ok, re-Invite, or Update with call-info, > which explicitly has a type for icon. > -Counter-argument: same as for vcard, plus with call-info there is > no way to know which picture format the far-end supports a priori. With a > supported-package negotiation one could know. > > 3) Sending a vcalendar-type invitation. Alice calls Bob, Bob says "hey > let's have a con call at time X", clicks and voila his phone sends a > vcalendar. > -Whether the vcalendar is related to the session or not and thus > whether it should be sent in an in-dialog request or not is certainly > debatable. Message method can already be used for this anyway. > > 4) Sending an HTTP URL. Alice calls Bob, a sales guy; Alice asks for more > info or a datasheet and Bob sends a URL for Alice to open with her web- > browser. > -One could also argue this is just making SIP the new SMTP, or > this should be sent using MESSAGE (which really is the new SMTP). > > 5) Sending a session traceroute. Alice calls Bob, Bob answers, Alice does > a sip-traceroute to figure out the path to Bob, by sending Info with an > incrementing max-forwards type header starting at 0 (but not really max- > forwards), with a sip-frag type response body or some such. > -It's debatable if certain types of B2BUA's (ie, SBCs) would ever > allow this type of thing to happen, due to security concerns, but I think > they may do it at domain boundary hops. I think this is a reasonable use > for INFO though, maybe. > > 6) Sending geo-location information after call establishment. Alice calls > Bob, a hotel receptionist. Alice asks for directions to hotel, clicks > button and sends him location info of her phone (or Bob clicks button and > sends her his location). > -The location conveyance draft specifically calls out INFO as > acceptable for geo-loc info. Whether this is a real use-case is > debatable, and obviously it could be done with a sub/not. > > 7) Sending softkey-labels (not digit-match maps, but rather softkey button > labels). Alice calls her vmail server. Vmail server sends softkey-labels > for the menu items available in the response, Alice presses softkeys and > sends them in INFO. > -This could (and maybe should) be done with sub/not, a la KPML, > where the vmail server sends the softkey labels in the Subscribe, UA sends > buttons pressed in Notifies. But this is similar to the DTMF use case so > may well have the same benefit of lower overhead since buttons are rarely > pressed. > > 8) Sending a screen-pop-up message, e.g., "Do you want to continue with > this session?" > -There is a patent for doing screen pop-ups using INFO. I guess > Alert-Info could be used for this, but it's not clear it should? > > > /***************** > * Use-cases which have been proposed by others or even implemented, > * which are dubious for INFO (IMHO): > *****************/ > 1) Sending RTP/RTCP statistics during call. > -There is an implementation of this, and the rationale is the > signaling plane box that wants this info is not actually the media plane > box that gets RTCP. Again this could (and IMO should) be done with > sub/not, so it can get stats after the call is over, and since it will > probably want periodic reports the overhead of the Subscribe should be > dwarfed by the number of Notifies. > > 2) Sending access-location information after call establishment. > -There is a P-Access-Network-Info header, and some have proposed > to send an update for it as a phone roams access points or cells. But I > think this is an odd thing to do inside an Invite session, vs. in a > sub/not or Register (and besides half the time the network inserts this > header, not the UA). > > 3) Sending media-control indications (ie, remote-control > "play/pause/etc.") > -This is done today by at least one vendor, but is debatable if > it's the right model. The argument is it's like SDP re-Invite for hold, > except at a media content layer above RTP, so not done in RTCP nor SDP. > > 4) Sending video fast update command > -This is an informational draft, which documents what has been > implemented, but states it should really be done in the media plane. > > 5) Sending peripheral control commands (ie, USB commands) > -There is actually a patent on this, amazingly. Someone thinks it > makes sense to create a SIP session to your laptop, or vice-versa, and > then send USB commands inside MIME in INFO messages. Methinks this should > be media-plane, if anything. > > 6) Sending charging information for a call (i.e., minutes remaining or > cost so far). > -There was a proposal to use this for Advice of Charge information > in TISPAN. IMO it should be a sub/not though, as they want this to > survive the Invite session. > > -hadriel > > > _______________________________________________ > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip > This list is for NEW development of the core SIP Protocol > Use [EMAIL PROTECTED] for questions on current sip > Use [EMAIL PROTECTED] for new developments on the application of sip > _______________________________________________ Sip mailing list https://www1.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
