[dccp] Would a DCCP flow need to send 2x its preferred rate?

[Eddie Kohler <kohler@icir.org>]

(To protect itself from "greedy TCP flows" gobbling up available
bandwidth?)

No.

TFRC exists to smooth out responses to congestion.  A single loss (such as
that caused by TCP probing) does not halve the TFRC transmit rate.  In many
cases it will cause only small changes (which, as we've discussed, the
application might be able to ignore).  In many cases it will not change the
rate at all.

If the congested link has high levels of statistical multiplexing, the TCP
flows won't likely gobble up the available bandwidth anyway -- even during
a silent period.

If the congested link has low levels of statmux -- like one DCCP flow and
one TCP flow -- then yes, the TCP would try for the available bandwidth.
And during a silent period, the TFRC flow would have to transmit something
so it wasn't crowded out entirely.  But this amount would be *half* the
nominal rate, or perhaps less.  Not twice.

Eddie

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