Subject: RE: [MMUSIC] Re: SDP QoS Mechanism Identification

From: "Jean-Francois Mule" <[email-masked]>
Date: Fri, 26 Jan 2007 09:14:27 -0700

Gonzalo,

   The draft should make it clear that 'qos-mech-send' and
'qos-mech-recv' session and media-level attributes are not
inter-dependent: one could be used without the other. 

Gonzalo Camarillo wrote:
> 4.4.  Subsequent Offer/answer Exchanges
>
>    If, during an ongoing session that uses QoS, an endpoint receives a
>    subsequent offer that does not contain the 'qos-mech-send' and
'qos-
>    mech-recv' attributes, the endpoints SHOULD continue using the same
>    QoS mechanism or mechanisms used up to that moment.

Here are a few questions/comments on this new requirement text.
>
>    If, during an ongoing session that uses QoS, an endpoint receives a
                   ^^^^^^^         ^^^^^^^^^^^^^
s/ongoing/established?
I thought about active but you could have an established session where
the media is not active in one or both directions so that may be
confusing.

"that uses QoS" implies that QoS was successfully negotiated, this is
misleading as this requirement may apply to sessions where no QoS is in
effectively use but for which a QoS negotiation was attempted (and
potentially failed).
What qualifies this session is not that QoS is in use, but rather that a
QoS mechanism was attempted in the first O/A due to the token lists.

Suggest expanding the text to say something like: during an established
session for which the QoS mechanism(s) were previously exchanged, ...
with better wording.

>    subsequent offer that does not contain the 'qos-mech-send' and
'qos-
>    mech-recv' attributes, 

Given that those 2 attributes are not necessarily linked or
inter-dependent, it suffices that only one attribute is left out of the
subsequent offer for this requirement to be applicable. If this is true,
then this sentence should be modified (at a minimum, say "or", or
better, reword to take into account the potential asymmetries.

> the endpoints SHOULD continue using the same
>    QoS mechanism or mechanisms used up to that moment.
You may consider adding a note that QoS re-negotiations using the same
QoS mechanisms might however be required.

Jean-Francois.

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