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

[Brett Tate <[e-mail]>]

> Do you have a suggestion for how I would change this 
> to a more limited parameter within the ABNF?  

See http://www.ietf.org/mail-archive/web/sipping/current/msg17796.html for more information.

The following is a potential change for RFC 3966's Telephone-Subscriber.  There is no need to add a new expandable parameter; Telephone-Subscriber already has "parameter".  Any new ones should comply with "parameter"; this includes npi-param and noa-param.

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

       npi-param = ";npi" EQUAL npi-value
       npi-value = p-value
       noa-param = ";noa" EQUAL noa-value
       noa-value = p-value

The Telephone-Subscriber's par is expanded to include two new values: npi-param and noa-param.  The following is the resulting ABNF; I don't recall if currently requires IANA registration:

par = parameter / extension / isdn-subaddress / npi-param / noa-param


The following is the recommended change for user; don't do it. :)  However if you need to do it and remain consistent with the "historic" nature of the draft (i.e. not indicating user=phone) or if need to avoid RFC 3966 non compliance, you have a few options although not sure if any would actually pass SIPCORE scrutiny.

1) You can indicate that user=phone (instead of user=ip) is the default for a P-Charge-Info SIP-URI.  Thus, it can be decoded as a Telephone-Subscriber even though user=phone was not added.  This is similar to RFC 3261 section 19.1.1 snippet.

         "The set of valid telephone-subscriber strings is a subset of
         valid user strings.  The user URI parameter exists to
         distinguish telephone numbers from user names that happen to
         look like telephone numbers.  If the user string contains a
         telephone number formatted as a telephone-subscriber, the user
         parameter value "phone" SHOULD be present.  Even without this
         parameter, recipients of SIP and SIPS URIs MAY interpret the
         pre-@ part as a telephone number if local restrictions on the
         name space for user name allow it."


2) You can indicate that user=pci (instead of user=ip) is the default for a P-Charge-Info SIP-URI.

userinfo         =  ( user / telephone-subscriber / p-ci) [ ":" password ] "@"
p-ci = user *charge-param ; not sure if good enough
charge-param = npi-param / noa-param / parameter

user-param        =  "user=" ( "phone" / "ip" / "pci" / other-user)

3) You can indicate that the P-Charge-Info SIP-URI user can be parsed as p-ci when user=ip (i.e. the default).

userinfo         =  ( user / telephone-subscriber) [ ":" password ] "@"
p-ci = user *charge-param ; not sure if good enough
charge-param = npi-param / noa-param / parameter