Bufferbloat in 3G/4G

Stephen Hemminger shemminger at vyatta.com
Mon Dec 17 13:55:05 EST 2012


Injong Rhee pointed me to this paper published at IMC.
  http://research.csc.ncsu.edu/netsrv/sites/default/files/p329.pdf

Interesting tidbit is yet another hack to avoid bufferbloat.

"Our investigation into the open source Android
platform reveals that a small untold trick has been
applied to mitigate the issue: the maximum TCP receive
buffer size parameter (tcp rmem max) has been set to a relatively
small value although the physical buffer size is much
larger. Since the advertised receive window (rwnd) cannot
exceed the receive buffer size and the sender cannot send
more than what is allowed by the advertised receive window,
the limit on tcp rmem max effectively prevents TCP
congestion window (cwnd) from excessive growth and controls
the RTT (round trip time) of the flow within a reasonable
range. However, since the limit is statically configured,
it is sub-optimal in many scenarios, especially considering
the dynamic nature of the wireless mobile environment.

They propose doing receiver adjustment which might help avoid
the "big buffer is at my stupid ISP" problem.

"In this paper, we propose dynamic receive
window adjustment (DRWA), a light-weight, receiver-based
solution that is cheap to deploy. Since DRWA requires modifications
only on the receiver side and is fully compatible
with existing TCP protocol, carriers or device manufacturers
can simply issue an over-the-air (OTA) update to smart
phones so that they can immediately enjoy better performance
even when interacting with existing servers.

Is anyone interested in integrating and testing this?



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