Re: [sipcore] draft-ietf-sipcore-location-conveyance-04
"James M. Polk" <jmpolk@cisco.com> Fri, 29 October 2010 00:49 UTC
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Date: Thu, 28 Oct 2010 19:51:43 -0500
To: "Elwell, John" <john.elwell@siemens-enterprise.com>, Anders Kristensen <ankriste@cisco.com>, "sipcore@ietf.org" <sipcore@ietf.org>
From: "James M. Polk" <jmpolk@cisco.com>
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Subject: Re: [sipcore] draft-ietf-sipcore-location-conveyance-04
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At 05:38 AM 10/28/2010, Elwell, John wrote: >Yes, 4 looks good, but I could live with 1. I think this has become #1 of two major open issues to address in Beijing (along with the supported and unsupported URI schemes and their respective possible error codes, as 2a and 2b). James >John > > > -----Original Message----- > > From: sipcore-bounces@ietf.org > > [mailto:sipcore-bounces@ietf.org] On Behalf Of Anders Kristensen > > Sent: 28 October 2010 05:53 > > To: sipcore@ietf.org > > Subject: Re: [sipcore] draft-ietf-sipcore-location-conveyance-04 > > > > I haven't really followed the discussion closely but I'll say this > > anyway. Many header fields are of a form similar to Geolocation, > > essentially lists of URI, and allow for parameters. But I think the > > parameters are pretty much always associated with individual > > entries in > > the list and may be present for more than one. > > > > From what I can tell, in the case of Geolocation, the > > routing-allowed > > param is not really attached to any particular entry in the list > > suggesting that maybe it doesn't belong in the same header field. I > > think that's the thinking that lead Paul to options 4 or 5 which seem > > much preferable to me. That allows Geolocation to fit the text in RFC > > 3261 that talks about combining header fields: > > > > Specifically, any SIP > > header whose grammar is of the form > > > > header = "header-name" HCOLON header-value *(COMMA > > header-value) > > > > allows for combining header fields of the same name into a comma- > > separated list. > > > > Granted, there's no rule that says that header fields with > > comma-separated values *must* fit the above grammar but ISTM > > that it's a > > pretty established pattern which is worth observing. > > > > Thanks, > > Anders > > > > On 10/27/2010 9:10 PM, James M. Polk wrote: > > > At 06:50 PM 10/27/2010, Paul Kyzivat wrote: > > >> I have a bunch inline here. > > > > > > I'll say ;-) > > > > > >> This supersedes my earlier suggested ABNF change. > > > > > > ack > > > > > > > > >> On 10/27/2010 2:32 PM, James M. Polk wrote: > > >>> Paul > > >>> > > >>> in-line > > >>> > > >>> At 08:36 PM 10/26/2010, Paul Kyzivat wrote: > > >>>> I took a quick look at the new version, and it seems to > > have cleanup a > > >>>> lot. But there *still* seems to be a problem with the syntax. > > >>>> (Interplay between ABNF and text.) From the text, I find: > > >>>> > > >>>> The placement of the "routing-allowed" header field parameter, > > >>>> strongly encouraged by [RFC5606], is outside the > > locationValue, and > > >>>> MUST always be last in the header field value. The > > routing-allowed > > >>>> parameter MUST be present, even when no locationValue is present. > > >>>> > > >>>> This is questionably supported by the ABNF: > > >>>> > > >>>> Geolocation-header = "Geolocation" HCOLON Geolocation-value > > >>>> Geolocation-value = ( locationValue [ COMMA locationValue ] ) > > >>>> / routing-param > > >>> > > >>> the above, I believe - but am open to be corrected by > > those better at > > >>> ABNF syntax that I, says > > >>> > > >>> - the Geolocation header can optionally have one or more > > locationValues > > >>> - which are where the location URIs go > > >> > > >> The above says *a* Geolocation header can have > > >> - one or two locationValues > > >> - OR one routing-param > > >> > > >> (The slash means OR) > > >> > > >> But it doesn't state that the Geolocation header itself can appear > > >> only once. And obviously if the goal is to have a > > locationValue AND a > > >> routing-param in the message, then with the above syntax > > at least TWO > > >> Geolocation headers will be required. > > >> > > >>> - but that the Geolocation header *will* have a routing-param > > >>> - which is the "routing-allowed" paramter that RFC 5606 > > wanted included > > >> > > >> Since the slash means OR, it doesn't mean it *will*. > > >> > > >>> The text of the ID then says that only zero, one or two > > locationValues > > >>> are allowed, which we all agreed to in Maastricht (in SIPCORE and > > >>> ECRIT/GEOPRIV). > > >>> > > >>>> locationValue = LAQUOT locationURI RAQUOT > > >>>> *(SEMI geoloc-param) > > >>>> locationURI = sip-URI / sips-URI / pres-URI > > >>>> / http-URI / HTTPS-URI > > >>>> / cid-url ; (from RFC 2392) > > >>>> / absoluteURI ; (from RFC 3261) > > >>>> geoloc-param = generic-param; (from RFC 3261) > > >>>> routing-param = "routing-allowed" EQUAL "yes" / "no" > > >>>> > > >>>> It only works if you presume that there are separate > > occurrences of > > >>>> GeoLocation-header in the message, one with just > > locations, another > > >>>> with just the routing-param. > > >>> > > >>> I don't get that part of your point, but I guess Martin's > > next message > > >>> says I need to add a "COMMA" after the ']' but before the > > ')'. Would > > >>> this satisfy your issue? > > >> > > >> Adding the COMMA and removing the slash would require the > > >> routing-param, and would separate it from the > > location-value. But then > > >> if you only wanted the routing-param without any locationValues you > > >> would have to write: > > >> > > >> Geolocation:,routing-allowed=no > > >> > > >> which is at least a bit weird, which I think is what Martin meant. > > >> > > >>>> The routing-param certainly can't be "last in the header > > field value" > > >>>> except in the degenerate sense, since it must be first > > and only in a > > >>>> Geolocation-header. > > >>> > > >>> If the routing-param was intended to be first, wouldn't > > it appear first > > >>> on this line? > > >> > > >> My point was that the syntax as written only allows > > routing-param by > > >> itself in a geolocation-header. E.g. > > >> > > >> Geolocation:routing-allowed=no > > >> > > >> It can't share a single Geolocation header with a > > locationValue. Hence > > >> it is *both* first and last in that header. > > >> > > >>>> Geolocation-value = ( locationValue [ COMMA locationValue ] ) > > >>>> / routing-param > > >>> > > >>> but it doesn't, so I'm confused. > > >> > > >> Again, the slash means OR. So you have: > > >> > > >> Geolocation-value = ( locationValue [ COMMA locationValue ] ) > > >> OR > > >> Geolocation-value = routing-param > > >> > > >> (Though you can't write it that way in ABNF. > > >> > > >>>> Below are some specific cases - both valid and invalid. > > In each case I > > >>>> show some headers bracketed by "...". That is intended > > to mean other > > >>>> headers in a message, but all in the same message. (And > > when I show > > >>>> multiple headers, there could be other non-geoloc > > headers interleaved.) > > >>>> > > >>>> * The following are legal according to the above, and > > probably within > > >>>> expected usage: > > >>>> > > >>>> ... > > >>>> Geolocation: cid:foo@example.com > > >>>> Geolocation: routing-allowed=yes > > >>>> ... > > >>>> > > >>>> ... > > >>>> Geolocation: cid:foo@example.com,cid:bar@example.com > > >>>> Geolocation: routing-allowed=yes > > >>>> ... > > >>>> > > >>>> ... > > >>>> Geolocation: routing-allowed=no > > >>>> ... > > >>>> > > >>>> * IIUC the following are allowed by the above both > > syntactically and > > >>>> according to the text, but is presumably not *intended* > > to be valid. > > >>>> (Its legal because the in each instance of Geolocation-header its > > >>>> last.) > > >>>> > > >>>> ... > > >>>> Geolocation: routing-allowed=no > > >>>> Geolocation: routing-allowed=yes > > >>>> ... > > >>>> > > >>>> The following is also allowed - I don't know if its > > intended or not: > > >>>> > > >>>> ... > > >>>> Geolocation: routing-allowed=yes > > >>>> Geolocation: cid:foo@example.com,cid:bar@example.com > > >>>> ... > > >>>> > > >>>> * The following is allowed by the ABNF though disallowed > > by the text: > > >>>> > > >>>> ... > > >>>> Geolocation: cid:foo@example.com,cid:bar@example.com > > >>>> Geolocation: cid:baz@example.com > > >>>> ... > > >>>> > > >>>> * The following is *not* allowed by the ABNF. I suspect > > it might be > > >>>> intended to be valid, but I'm far from sure about it: > > >>>> > > >>>> ... > > >>>> Geolocation: cid:foo@example.com,routing-allowed=yes > > >>>> ... > > >>> > > >>> to get this above example "allowed", would I correct the > > existing ABNF > > >>> to be > > >>> > > >>>> Geolocation-value = ( locationValue [ COMMA > > locationValue ] COMMA ) > > >>>> / routing-param > > >>> > > >>> ? > > >> > > >> No. *That* would allow all of the following but not the > > example above: > > >> > > >> Geolocation: cid:foo@example.com, > > >> Geolocation: cid:foo@example.com,cid:bar@example.com, > > >> Geolocation: routing-allowed=yes > > >> > > >>>> In addition to that, the text is very explicit that: > > >>>> > > >>>> The routing-allowed > > >>>> parameter MUST be present, even when no locationValue is present. > > >>>> > > >>>> but then it says: > > >>>> > > >>>> If no routing-allowed parameter > > >>>> is present in a SIP request, a SIP intermediary MAY insert this > > >>>> value with a RECOMMENDED value of "no" by default. > > >>>> > > >>>> So its required, but we have rules to follow if its > > missing. But I > > >>>> don't understand how it *can* be required, since the > > sender of the > > >>>> request may not understand/support Geolocation and so > > won't include it. > > >>> > > >>> What we're trying to do here is explicitly give > > instructions to SIP > > >>> intermediary implementers to include the routing-allowed > > parameter if > > >>> one isn't present, with a default value of =no. > > >> > > >> I went back and reread the section containing this text. It is in a > > >> section explicitly about this header. So on reflection I > > suppose the > > >> "MUST be present" was intended to imply "in the > > Geolocation *header". > > >> I took it to mean "in the request". > > >> > > >> Requiring it to be in the header only makes sense if there > > can be at > > >> most one header. And then it only makes sense if the > > syntax is altered > > >> to allow both the routing-parameter and the locationValue > > in the same > > >> header. > > >> > > >>>> ISTM that in reality its only *required* if the is a > > locationValue > > >>>> present, and is otherwise optional. > > >>> > > >>> which is how most would read it if ... > > >>> > > >>>> If no routing-allowed parameter > > >>>> is present in a SIP request, a SIP intermediary MAY insert this > > >>>> value with a RECOMMENDED value of "no" by default. > > >>> > > >>> ... weren't present in the document. But, there is no > > permission to > > >>> allow SIP intermediaries to add the routing-allowed > > parameter, which we > > >>> wanted to cover. > > >> > > >> I'm still confused. Let me state what I think you are after: > > >> > > >> - a request may or may not contain a Geolocation header > > >> - a request may not contain more than one Geolocation header > > > > > > of what you have, this one is one I hadn't considered > > important, but if > > > that gets everything aligned, then I'm all for adding it in. > > > > > >> - a Geolocation header MUST contain a routing-param > > >> - a Geolocation header Must contain zero, one, or two > > locationValues > > >> - you prefer the routing-param to be the last field in the header > > >> - a proxy MAY add a Geolocation header if one is not present > > >> (in which case it MUST include a routing-param) > > >> - a proxy MAY add a locationValue to an existing Geolocation header > > >> if it doesn't already have two locationValues. (And I guess it > > >> could add two if there initially were none.) > > >> > > >> And you would like ABNF that is consistent with the above. > > > > > > with the one caveat, yes. > > > > > > > > >> I'm going to give you some alternatives that should all be > > >> syntactically correct. I'll give you one that meets the above, and > > >> some others that may be more appealing variations. Then we can see > > >> which people prefer. > > >> > > >> 1) The following tries to meet the requirements I spelled > > out above: > > >> > > >> Geolocation-header = "Geolocation" HCOLON Geolocation-value > > >> Geolocation-value = locationValue [ COMMA locationValue] > > >> COMMA routing-param > > >> / routing-param > > > > > > I hadn't even thought that was possible, but seeing it, I'm amazed I > > > didn't try it > > > > > > (i.e., it's another classic "I could've had a v8" moment)... > > > > > > I'm not as smart as you, Paul <:-| > > > > > >> locationValue = LAQUOT locationURI RAQUOT > > >> *(SEMI geoloc-param) > > >> locationURI = sip-URI / sips-URI / pres-URI > > >> / http-URI / HTTPS-URI > > >> / cid-url ; (from RFC 2392) > > >> / absoluteURI ; (from RFC 3261) > > >> geoloc-param = generic-param; (from RFC 3261) > > >> routing-param = "routing-allowed" EQUAL "yes" / "no" > > >> > > >> This must be accompanied by text stating that there MUST be at most > > >> one Geolocation-header in a request. > > > > > > you've sold me on this one (and yes, I examined all the > > others before > > > jumping on this first one!). Do others have strong opinions > > about why > > > not #1? > > > > > > thank you for this! > > > > > > James > > > > > > > > >> 2) The following is similar to (1), but allows more than two > > >> 'locationValue's > > >> > > >> Geolocation-header = "Geolocation" HCOLON Geolocation-value > > >> Geolocation-value = *(locationValue COMMA) routing-param > > >> locationValue = LAQUOT locationURI RAQUOT > > >> *(SEMI geoloc-param) > > >> locationURI = sip-URI / sips-URI / pres-URI > > >> / http-URI / HTTPS-URI > > >> / cid-url ; (from RFC 2392) > > >> / absoluteURI ; (from RFC 3261) > > >> geoloc-param = generic-param; (from RFC 3261) > > >> routing-param = "routing-allowed" EQUAL "yes" / "no" > > >> > > >> The same wording is required with it > > >> > > >> 3) The following is a copy from my earlier posting: > > >> > > >> Geolocation-header = "Geolocation" HCOLON Geolocation-value > > >> *( COMMA Geolocation-value) > > >> Geolocation-value = locationValue / routing-param > > >> locationValue = LAQUOT locationURI RAQUOT > > >> *(SEMI geoloc-param) > > >> locationURI = sip-URI / sips-URI / pres-URI > > >> / http-URI / HTTPS-URI > > >> / cid-url ; (from RFC 2392) > > >> / absoluteURI ; (from RFC 3261) > > >> geoloc-param = generic-param; (from RFC 3261) > > >> routing-param = "routing-allowed" EQUAL "yes" / "no" > > >> > > >> The above is overly forgiving, in that it permits zero or more > > >> locationURIs and zero or more routing-params. That then needs to be > > >> tightened up with text. I think the text needs to say, > > more or less: > > >> > > >> - if there are any locationURIs in a sip request, > > >> then a routing-param MUST be present in the request > > >> - there MUST NOT be more than one routing-param present in a > > >> sip request. > > >> - there MUST NOT be more than two locationURIs in a sip request > > >> (if there is really a reason for such a restriction) > > >> > > >> 4) The following is a more radical change: > > >> > > >> Geolocation-header = "Geolocation" HCOLON locationValue > > >> [ COMMA locationValue ] > > >> locationValue = LAQUOT locationURI RAQUOT > > >> *(SEMI geoloc-param) > > >> locationURI = sip-URI / sips-URI / pres-URI > > >> / http-URI / HTTPS-URI > > >> / cid-url ; (from RFC 2392) > > >> / absoluteURI ; (from RFC 3261) > > >> geoloc-param = generic-param; (from RFC 3261) > > >> > > >> Georouting-header = "Geolocation-Routing" HCOLON > > >> ( "yes" / "no" / gen-value ) > > >> > > >> This one needs to be accompanied by text stating that each of > > >> Geolocation-header and Georouting-header may appear at most once > > >> in a request, and that if Georouting-header is absent it defaults > > >> to "no". > > >> > > >> 5) A more lenient variant on (4): > > >> > > >> Geolocation-header = "Geolocation" HCOLON locationValue > > >> *( COMMA locationValue ) > > >> locationValue = LAQUOT locationURI RAQUOT > > >> *(SEMI geoloc-param) > > >> locationURI = sip-URI / sips-URI / pres-URI > > >> / http-URI / HTTPS-URI > > >> / cid-url ; (from RFC 2392) > > >> / absoluteURI ; (from RFC 3261) > > >> geoloc-param = generic-param; (from RFC 3261) > > >> > > >> Georouting-header = "Geolocation-Routing" HCOLON > > >> ( "yes" / "no" / gen-value ) > > >> > > >> This one needs to be accompanied by text stating that > > >> Georouting-header may appear at most once in a request, and that > > >> if Georouting-header is absent it defaults to "no". > > >> > > >> (The Geolocation-header can appear zero or more times.) > > >> > > >> This is only preferred to (4) if more than two locationValues > > >> are acceptable. ISTM that once we allowed two, allowing more > > >> makes sense, with the same limitations imposed with two - that > > >> its up to the recipient to figure out which to use. > > >> > > >> Of the above, I technically and esthetically prefer (5) - or (4) if > > >> the limitation to two URIs is important. I see no reason > > to *require* > > >> the routing-param if the default is understood to be "no". > > >> > > >> Pragmatically I think I prefer (1) - its the least > > variation from what > > >> has been recently discussed that, IMO, makes any sense. > > >> > > >> > > >>>> In that case, an intermediary that adds a locationValue > > not only MAY, > > >>>> but presumably MUST add a missing routing-param if it adds a > > >>>> locationValue. > > >>> > > >>> We can get there (i.e., allow this) without stating this > > is a MUST, > > >>> can't we? > > >> > > >>>> I have never understood why the routing-param is > > required to be last. > > >>> > > >>> maybe it doesn't need to be, but it certainly is easier for > > >>> monitoring/reading human to find if it is last when > > looking at a decode. > > >>> > > >>>> And as my examples show, its difficult/impossible to > > enforce this in > > >>>> ABNF. > > >>>> > > >>>> Thanks, > > >>>> Paul > > >>> > > > > > > _______________________________________________ > > > sipcore mailing list > > > sipcore@ietf.org > > > https://www.ietf.org/mailman/listinfo/sipcore > > > > > _______________________________________________ > > sipcore mailing list > > sipcore@ietf.org > > https://www.ietf.org/mailman/listinfo/sipcore > > >_______________________________________________ >sipcore mailing list >sipcore@ietf.org >https://www.ietf.org/mailman/listinfo/sipcore
- Re: [sipcore] draft-ietf-sipcore-location-conveya… Paul Kyzivat
- Re: [sipcore] draft-ietf-sipcore-location-conveya… Thomson, Martin
- Re: [sipcore] draft-ietf-sipcore-location-conveya… Paul Kyzivat
- Re: [sipcore] draft-ietf-sipcore-location-conveya… James M. Polk
- Re: [sipcore] draft-ietf-sipcore-location-conveya… James M. Polk
- Re: [sipcore] draft-ietf-sipcore-location-conveya… James M. Polk
- Re: [sipcore] draft-ietf-sipcore-location-conveya… Paul Kyzivat
- Re: [sipcore] draft-ietf-sipcore-location-conveya… James M. Polk
- Re: [sipcore] draft-ietf-sipcore-location-conveya… Anders Kristensen
- Re: [sipcore] draft-ietf-sipcore-location-conveya… Elwell, John
- Re: [sipcore] draft-ietf-sipcore-location-conveya… James M. Polk
- Re: [sipcore] draft-ietf-sipcore-location-conveya… Paul Kyzivat
- Re: [sipcore] draft-ietf-sipcore-location-conveya… James M. Polk