Subject: [MMUSIC] BUNDLE: meaning of "unspecified" when describing "bundle-only"

From: Adam Roach <[email-masked]>
Date: Thu, 29 Dec 2016 15:15:52 -0600

We've recently come across an issue with the way the "bundle-only" 
attribute is described in the current document. The current language 
regarding port handling reads:

    The usage of the 'bundle-only' attribute is only defined for a
    bundled "m=" line with a zero port value, within an offer. Other
    usage is unspecified.

Usually, when we have this kind of language, we still ensure that 
behavior is well defined, to help avoid unnecessary interop failures. I 
see a couple of different options here:

 1. Remove the final sentence and add language saying that creators of
    SDP MUST NOT include a "bundle-only" attribute in an m-section that
    has a non-zero port, and that recipients of such SDP {SHOULD,MUST}
    reject it; or

 2. Retain language saying that including a "bundle-only" attribute in a
    non-zero m-section is unspecified, but add normative language along
    the lines of: "implementations that receive an m-section with a
    non-zero port that also contains a 'bundle-only' attribute MUST
    ignore the {attribute,port}."

I don't have a preference between these choices, but I think we do need 
clarity. To be absolutely clear, this feedback is based on actual 
implementation interop failures in the field. This problem is not 
theoretical.

/a