In response to Pasi's tsvarea talk on where to go next with DCCP, I
would like to offer two ideas for future DCCP work that could increase
the its likelihood becoming widely used for something.
1. Get involved in the nascent multipath TCP work and develop a way to
use DCCP as a better subflow layer, as an alternative to the
compatibility "base case" of using legacy TCP connections as
subflows. This way DCCP could become a basic part of a multipath TCP
and could get automatically and transparently used to provide the
congestion control for standard TCP applications. For more details
see our draft for the upcoming mptcp BOF tomorrow morning (http://tools.ietf.org/html/draft-ford-mptcp-multiaddressed
). Personally I see this by far the most promising potential use for
DCCP, but I admit some bias. :)
2. In the interest of addressing the comment after Pasi's talk about
both DCCP and its potential applications wanting to have "control"
over congestion control... Part of the problem seems to be that
typical multimedia applications operate at only certain "quantified"
bitrates: for example if an application tries 128Kbps but DCCP
throttles it due to congestion, it has to cut all the way down to its
next lower speed of, say, 64Kbps and stay there, even if say 100Kbps
is actually available. The problem is if the application keeps just
sending 64Kbps, DCCP's congestion control will not try to probe for
bandwidth and the application will never know when it can move back up
to 128Kbps. So solve this by developing an extension to DCCP's
congestion control mechanisms an a corresopnding API allowing
applications to maintain a standing "request" for more bandwidth than
they're actually using at the moment, and to notify the application
when the full amount of requested bandwidth appears to be available.
That should allow media applications to follow DCCP's congestion
control decisions without giving up the control they need in order to
utilize available bandwidth dynamically. There are several
alternative ways to achieve this at the congestion control level, at
least one of which might even be reasonably safe and efficient; I'll
try to write it up in a follow-on E-mail shortly.
Thanks,
Bryan
- [dccp] DCCP work ideas Bryan Ford
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