Re: [MMUSIC] Changes for draft-ietf-mmusic-trickle-ice-sip-14 - ABNF

[Christer Holmberg <[e-mail]>]

Hi,


Hi Thomas,



I hope Paul can jump in on this one too, since it's ABNF related :)



However, I think there are some issue with the ABNF (not related to Adam¹s

issue).



For example, the syntax says:



  ice-pwd-attribute      = %s"a" "=" ice-pwd-att



Then the draft says:



  with ice-pwd-attribute from [I-D.ietf-mmusic-ice-sip-sdp],



which says



ice-pwd-att           = "ice-pwd:" password

i.e. doesn't introduce a second a=



First, I think the structure in draft-ice-sip-sdp is wrong. It shall be something like:



      Attribute Name: ice-pwd



      Attribute Value: ice-pwd-att



      Usage Level: media



      Charset Dependent: No



      Mux Category: TBD



    The Augmented BNF syntax [RFC5234] for the attribute is:



      ice-pwd-att = password

      password = blah blah...



Now, whether we should use that syntax also in trickle-ice I don't know. I would like to hear Paul's opinion.
You are mixing up the ABNF syntax and the IANA registration template.

The ABNF syntax in section 5.4 of draft-ietf-mmusic-ice-sip-sdp-16 and also section 15.4 of RFC 5245
both define the ABNF grammar as



  ice-pwd-att           = "ice-pwd" ":" password



That is the "old" way of defining attributes. My example above is according to the "new" way, that has been used lately (and, no, I didn't mix up the ABNF syntax and the IANA reg).



Another example is in section 6 of draft-bundle (with the corresponding IANA reg in section 16.3).



That's a bad example since a=bundle-only doesn't have a value.

A better example is the tls-id attribute, defined in Section 4 of https://www.ietf.org/id/draft-ietf-mmusic-dtls-sdp-32.txt.

I'd rather prefer ( just personal preference ) the style of https://tools.ietf.org/html/draft-ietf-mmusic-rid-14, where the registration in section 11 refers to the grammar in section 10.

The ABNF is not according to the new style.

And, just to clarify, my comments are not based on my personal preference, but on my understanding of how SDP attributes are to be defined nowadays.

Nevertheless, the only thing I care about is that we don't confuse the reader by having two conflicting definitions of the token ice-pwd-att in RFC5245 and draft-ietf-mmusic-ice-sip-sdp. If you want to do changes in the grammar, use a distinct token.

No matter how the grammar in draft-ietf-mmusic-ice-sip-sdp eventually will look like (that discussion anyway doesn't belong to this thread), I still think we should just reference it from this draft.

Regards,

Christer