Re: [sipcore] draft-ietf-sipcore-location-conveyance-04
Paul Kyzivat <pkyzivat@cisco.com> Wed, 27 October 2010 01:34 UTC
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Date: Tue, 26 Oct 2010 21:36:02 -0400
From: Paul Kyzivat <pkyzivat@cisco.com>
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Cc: SIPCORE <sipcore@ietf.org>
Subject: Re: [sipcore] draft-ietf-sipcore-location-conveyance-04
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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 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. 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. 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 ... 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. ISTM that in reality its only *required* if the is a locationValue present, and is otherwise optional. 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. I have never understood why the routing-param is required to be last. And as my examples show, its difficult/impossible to enforce this in ABNF. Thanks, Paul
- 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