Subject: [MMUSIC] Comments on draft-ietf-mmusic-sdp-bundle-negotiation-06

From: Paul Kyzivat <[email-masked]>
Date: Tue, 08 Apr 2014 13:42:56 -0400

Here are comments on the latest version:

Section 1:

I had trouble parsing the following:

    Once it is known that both the offerer and the answerer supports the
    BUNDLE mechanism, a BUNDLE group and the associated BUNDLE addresses
    have been negotiated, each endpoint can assign its BUNDLE address to
    each "m=" line within, and use the address to send and receive all
    media associated with, the BUNDLE group.

I suggest:

    Once it is known that both the offerer and the answerer support the
    BUNDLE mechanism, and a BUNDLE group and the associated BUNDLE
    addresses have been negotiated, each endpoint can assign its BUNDLE
    address to each "m=" line within, and use the address to send and
    receive all media associated with, the BUNDLE group.

Later in the section, in the following:

    The procedures in this specification apply to a given BUNDLE group.

I suggest a change: s/apply/apply independently/

Section 2:

In the following:

    Offerer BUNDLE address: Within a given BUNDLE group, an IP address
    and IP port combination used by an offerer to send and receive all
    media associated with each "m=" line within the BUNDLE group.

    Answerer BUNDLE address: Within a given BUNDLE group, an IP address
    and IP port combination used by an answerer to send and receive all
    media associated with each "m=" line within the BUNDLE group.

I question the "to send and" in the above. In general with O/A the 
address is only for receive - there is no promise that media will also 
be sent from that address.

Then, in the following:

    Bundled "m=" line: An "m=" line, in an SDP offer or SDP answer,
    associated with a BUNDLE group.

Is an m-line a bundled m-line if it is included in the a=group:bundle of 
the offer, but not in the answer???

IOW, for an offer do I determine if an m-line is bundled based on the 
a=group:bundle in the *offer*, or in the *answer*?

Section 5.2.1:

s/BUNDEL/BUNDLE/

Section 5.2.3:

This fits into the general format for documenting O/A. So this section 
specifically describes the processing of the first offer. (E.g., in the 
sip session.)

But this section is also used as *the* place to describe the initial 
offer that creates a BUNDLE group. That suggests that you can only 
create a bundle group within the first O/A of a sip session. Certainly 
that is not the intent. (A BUNDLE group can be first created in an offer 
that modifies an SDP session.)

I don't currently have a suggestion for how to fix this. It is hard!

Section 5.2.4.2:

In the last line of the following:

    When an answerer generates an SDP answer, it MUST select a BUNDLE
    address for the offerer, referred to as the offerer BUNDLE address.
    The answerer MUST select an address which the offerer in the
    associated SDP answer requested to be within the BUNDLE group.

s/answer/offer/

Section 5.2.6.2:

The following has some grammar problems:

    NOTE: If the offerer wants that the answerer selects the address
    associated with the added "m=" as the offerer BUNDLE address, the
    offerer suggested BUNDLE mid MUST represent the added "m=" line
    [Section 5.2.3.2].

I suggest:

    NOTE: If the offerer wants the answerer to select the address
    associated with the added "m=" as the offerer BUNDLE address, the
    offerer suggested BUNDLE mid MUST represent the added "m=" line
    [Section 5.2.3.2].

	Thanks,
	Paul