Subject: [Iptel] Re: draft-ietf-iptel-trunk-group-03

From: Paul Kyzivat <[email-masked]>
Date: Wed, 16 Feb 2005 19:26:05 -0500

One thing concerns me in this draft:

You are requiring use of the phone-context parameter, even with global 
numbers, such as:

	tel:+15555551212;phone-context=telco.example.com;tgrp=tg55

Now this may be debatable, but I believe that usage is currently invalid 
according to RFC3966. (Phone-context is only valid with a local-number.) 
Here is some of the ABNF from 3966:

    telephone-uri        = "tel:" telephone-subscriber
    telephone-subscriber = global-number / local-number
    global-number        = global-number-digits *par
    local-number         = local-number-digits *par context *par

    context              = ";phone-context=" descriptor

    par                  = parameter / extension / isdn-subaddress
    extension            = ";ext=" 1*phonedigit
    isdn-subaddress      = ";isub=" 1*uric

    parameter            = ";" pname ["=" pvalue ]
    pname                = 1*( alphanum / "-" )

Its arguable because "phone-context" can be parsed as both a 'context' 
and a 'parameter'. But I think it is pretty clear that isn't the intent. 
(And if it was, then semantically it would just be a parameer, not a 
context.)

So I think you need to make a *change* rather than just an *extension* 
to 3966 if you want to use phone-context with global numbers.

	Paul

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