Re: [Sipping] draft-york-sipping-p-charge-info-12: ABNF

[Dan York <[e-mail]>]

Paul,

Many thanks as always for your helpful comments.  The question seems to be that we want to define ABNF that describes an example like this:

P-Charge-Info: <sip:6835555555;npi=001;noa=3@10.10.7.21>

The optional npi and noa parameters are parameters that are on the left side of the @ symbol in a SIP URI.

In looking at the original ABNF we had in there, it does seem to me that it *was* incorrect, as it would have required a URI of something like one of these:

P-Charge-Info: <sip:6835555555@10.10.7.21;npi=001;noa=3>
P-Charge-Info: <sip:6835555555@10.10.7.21>;npi=001;noa=3

I'm guessing the former... but it's irrelevant - the point is that either of these would be wrong.  We need the ABNF to specify that THIS is the correct notation:

P-Charge-Info: <sip:6835555555;npi=001;noa=3@10.10.7.21>

So we really do want to specify somehow that "chargeparam" is part of the "userinfo" section of the SIP URI, and perhaps specifically the "user" section given these definitions:

> RFC 3261:
> 
> userinfo = ( user / telephone-subscriber ) [ ":" password ] "@"
> user = 1*( unreserved / escaped / user-unreserved )
> 
> RFC 2806:
> 
> telephone-subscriber = global-phone-number / local-phone-number


Any ABNF experts out there able to help me sort this out?  The current formal definition is:

----
   The syntax of the P-Charge-Info header is described as follows:

         P-Charge-Info = "P-Charge-Info" HCOLON (name-addr / addr-spec)
                 ; name-addr and addr-spec are specified in RFC 3261
             charge-param = npi-param / noa-param / generic-param
             npi-param = ";npi" EQUAL npi-value
                 ; generic-param is specifed in RFC 3261
             npi-value = 3DIGIT
             noa-param = ";noa" EQUAL noa-value
             noa-value = gen-value

   The SIP URI is the billing indicator that is passed between the
   parties.

   charge-param is used as a userinfo parameter in P-Charge-Info.
----

Thanks,
Dan

On Nov 29, 2011, at 8:59 PM, Paul Kyzivat wrote:

> On 11/30/11 3:38 AM, Dan York wrote:
>> Brett, (and replying from a slightly different address so that it will
>> go to the SIPPING list)
>> 
>> Thank you for the feedback and question. The ABNF in the draft has
>> evolved over the past almost-4 years as various people more literate
>> than I in ABNF have given us feedback and we've updated the draft.
>> 
>> In the ABNF section, "chargeparam" is intended to represent that you
>> could optionally have the "noa", "npi" parameters - or any other generic
>> parameters found in RFC 3261(such as "user=phone")
> 
> Including generic-param is a mechanism for making the syntax compatible with future enhancements. But allowing it syntactically doesn't specify how parameters that match generic-param are to be processed if the are present on this header. Typically you would specify in the draft that they should be ignored unless the behavior is defined by some other specification.
> 
>> Originally, the ABNF read:
>> 
>>          P-Charge-Info = "P-Charge-Info" HCOLON (name-addr / addr-spec)*
>>                  (SEMI charge-param)
>>                  ; name-addr and addr-spec are specified inRFC 3261  <http://tools.ietf.org/html/rfc3261>
>>              charge-param = npi-param / noa-param / generic-param
>> 
>> 
>> I thought that was fairly clear and made sense. However, I changed the
>> ABNF in rev -10 in October 2010 to more simply:
>> 
>>          P-Charge-Info = "P-Charge-Info" HCOLON (name-addr / addr-spec)
>>                  ; name-addr and addr-spec are specified inRFC 3261  <http://tools.ietf.org/html/rfc3261>
>>              charge-param = npi-param / noa-param / generic-param
>> 
>> 
>> after someone strongly made the case that the "* (SEMI charge-param)"
>> was not required because it was a "userinfo parameter" to the
>> name-addr/addr-spec element.
> 
> That is something very different. What you have above are *header* parameters for the P-Charge-Info header.
> 
> It sounds like you are talking about TEL-URI parameters when the tel uri has been converted to a sip URI. But if so, then you should be defining an extension to the tel-uri syntax. And then you would need to define the semantics relative to the tel-uri. (It isn't really kosher to define the parameters on the tel-uri but then only define their semantics relative to the P-Charge-Info header.)
> 
> IMO its wrong to make this change. Rather you should go back to defining these explicitly as header params for P-Charge-Info.
> 
> 	Thanks,
> 	Paul
> 
>> Unfortunately, the email exchange about
>> this seems to have NOT taken place on the mailing list but rather in a
>> private email exchange - and I no longer have access to the archives of
>> the email account where that occurred (I am no longer with Voxeo) - so I
>> don't know who it was that argued for this change.
>> 
>> I'm directly cc'ing John Haluska as he was involved in with a number of
>> those exchanges and can perhaps clarify this.
>> 
>> In reviewing section 19.1.1 of RFC 3261 (
>> http://tools.ietf.org/html/rfc3261#section-19.1.1 ) and sections 19.1.2,
>> 19.1.3, and 19.1.6 as well as the ABNF in section 25, I am guessing that
>> the rationale was because the "charge-param" does fit into the "user"
>> section of the URI.
>> 
>> So that's a roundabout way of saying that it is part of "user", as I
>> interpret the ABNF in RFC 3261.
>> 
>> Do you have suggestions for how to make this clearer in the draft? Would
>> the original ABNF be more useful to you? Should the sentence
>> "charge-param is used as a userinfo parameter in P-Charge-Info" indicate
>> that it is the "user" part of the "userinfo" field?
>> 
>> Thanks,
>> Dan
>> 
>> P.S. After not receiving any feedback for many, many months I suddenly
>> have received two email questions/comments about P-Charge-Info today. I
>> don't know if this is as a result of the mention on a mailing list that
>> Richard Shockey mentioned... but I was surprised.
>> 
>> On Nov 29, 2011, at 1:35 PM, Brett Tate wrote:
>> 
>>> Howdy,
>>> 
>>> Draft-york-sipping-p-charge-info-12 includes the following ABNF
>>> without explicitly indicating if the charge-param is part of user,
>>> telephone-subscriber, or both. I'm not sure how to interpret the
>>> charge-param statement since userinfo has no parameters (although user
>>> and telephone-subscriber can have them).
>>> 
>>> Is charge-param part of user, telephone-subscriber, or both? I
>>> recommend updating section 7 to remove the ambiguity.
>>> 
>>> Thanks,
>>> Brett
>>> 
>>> 
>>> ------
>>> 
>>> Draft-york-sipping-p-charge-info-12:
>>> 
>>> "The syntax of the P-Charge-Info header is described as follows:
>>> 
>>> P-Charge-Info = "P-Charge-Info" HCOLON (name-addr / addr-spec)
>>> ; name-addr and addr-spec are specified in RFC 3261
>>> charge-param = npi-param / noa-param / generic-param
>>> npi-param = ";npi" EQUAL npi-value
>>> ; generic-param is specifed in RFC 3261
>>> npi-value = gen-value
>>> noa-param = ";noa" EQUAL noa-value
>>> noa-value = gen-value
>>> 
>>> The SIP URI contained in the name-addr/addr-spec is the billing
>>> indicator that is passed between the parties.
>>> 
>>> charge-param is used as a userinfo parameter in P-Charge-Info."
>>> 
>>> 
>>> RFC 3261:
>>> 
>>> userinfo = ( user / telephone-subscriber ) [ ":" password ] "@"
>>> user = 1*( unreserved / escaped / user-unreserved )
>>> 
>>> RFC 2806:
>>> 
>>> telephone-subscriber = global-phone-number / local-phone-number
>>> 
>> 
>> --
>> Dan York [e-mail] <mailto:[e-mail]>
>> Phone: [phone] skype:danyork
>> http://www.danyork.com/
>> http://twitter.com/danyork
>> 
>> 
>> 
>> --
>> Dan York [e-mail] <mailto:[e-mail]>
>> http://www.danyork.com/ skype:danyork
>> Phone: [phone]
>> Twitter - http://twitter.com/danyork
>> --------------------------------------------------------
>> All comments and opinions are entirely my own and have no connection
>> whatsoever to any employer, past or present. Indeed, by tomorrow even I
>> might be disavowing these comments.
>> --------------------------------------------------------
>> 
>> 
>> 
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> 
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-- 
Dan York  [e-mail]
http://www.danyork.com/   skype:danyork
Phone: [phone]
Twitter - http://twitter.com/danyork
--------------------------------------------------------
All comments and opinions are entirely my own and have no connection whatsoever to any employer, past or present. Indeed, by tomorrow even I might be disavowing these comments.
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