[MMUSIC] Bundling and QoS marking (was: Question about Bundle and Legacy Interop)

[[e-mail] (Dale R. Worley)]

> From: "Charles Eckel (eckelcu)" <[e-mail]>
> 
> > From: [e-mail]
> > 
> > I've seen some drafts claiming that Bundle would be harmful in for instance
> > cellular networks for QoS differentiation. Is that the motivation where the
> > non-Bundled RTCWeb use comes from, or are there some other good
> > reasons?
> 
> Not just for cellular but for any scenario in which QoS is based on
> using different 5-tuples for media flows for which different
> treatment is desired.

The question of QoS differentiation is interesting and probably one we
have to address, as mobile devices have bandwidth limitations.

If it's possible to mark individual packets within a transport flow
for different QoS treatments, then we need to define QoS markings as
an "application level" attribute rather than a "transport level"
attirbute.

If QoS differentiation is done entirely based on transport
associations (5-tuples), then the strategy would be to have several
bundles of m= lines, one for each QoS type.

The naive way to do this, that is, just offering two different
bundles, is suboptimal if the offerer doesn't know whether different
media types need to be in different transport flows or not, because it
prevents the answerer from arranging for all the media to be in one
bundle (using one transport association, i.e., port) if the answerer
knows that there is no QoS problem.

This is a situation where using hierarchical bundling would provide a
solution:  If the offerer does not have a need for different transport
flows for audio and video, but is concerned that the answerer might
have such a need, it builds an offer containing a master bundle that
contains two subordinate bundles, one containing (e.g.) the audio
streams and one containing the video streams.

If the answerer does not want to separate audio and video, it accepts
all the bundling, and then all media are in one transport flow.  If
the answerer wants to separate audio and video, it rejects the
top-level bundle, but accepts each subordinate bundle individually,
thus arranging for two transport flows, one containing audio and one
containing video.

Dale