On Fri, 9 Oct 2015, Joe Touch wrote:
On 10/9/2015 5:22 PM, David Lang wrote:
You don't want to acknowlege it, but TCP is broken in the face of
excessive buffering.
Arguably, buffering was broken and failed to provide the feedback to TCP
(see next paragraph)
TCPM isn't fixing that, grassroots efforts are
developing the fixes and AQM is formalizing the results.
TCPM fixed it in 2001 by providing the flags for ECN, which was enabled
by default in Windows since 2012. ALTQ support for ECN has been around
for nearly that long.
What's changed? Not the TCP reaction (except in extreme cases such as
for datacenters) but the router algs. And getting the router algs into
routers - esp. home devices.
if ECN solved the problem, then bufferbloat would have been a non-issue. A large
percentage of the home routers are running OpenWRT or similar with ECN enabled.
That didn't solve the problem.
TCP is also broken in the face of current and within-the-next-year
future wifi technologies. AQM helps some here, and there is again
outside efforts to address the problem. TCPM hasn't done anything that
I've heard of other than possibly say that the network technology is
broken and shouldn't be used.
You might start tracking the TCPM list. We've been talking today about
how to reduce the ACKs by direct action of the source.
There are only so many lists I can track (linux kernel takes a lot of time for
example :-), I'll consider it.
The problem with proposals like that is just like RFC3449 says, the source can't
know what the network looks like to decide if there is a benefit to reducing
ACKs.
David Lang
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