[Make-wifi-fast] [Codel] fq_codel_drop vs a udp flood
chromatix99 at gmail.com
Sun May 1 14:20:10 EDT 2016
> On 1 May, 2016, at 20:59, Eric Dumazet <eric.dumazet at gmail.com> wrote:
> fq_codel_drop() could drop _all_ packets of the fat flow, instead of a
> single one.
Unfortunately, that could have bad consequences if the “fat flow” happens to be a TCP in slow-start on a long-RTT path. Such a flow is responsive, but on an order-magnitude longer timescale than may have been configured as optimum.
The real problem is that fq_codel_drop() performs the same (excessive) amount of work to cope with a single unresponsive flow as it would for a true DDoS. Optimising the search function is sufficient.
- Jonathan Morton
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