nanog mailing list archives
Re: TCP congestion control and large router buffers
From: Sam Stickland <sam_mailinglists () spacething org>
Date: Tue, 21 Dec 2010 19:21:58 +0000
On 21 Dec 2010, at 07:18, Mikael Abrahamsson <swmike () swm pp se> wrote: On Mon, 20 Dec 2010, Jim Gettys wrote: Common knowledge among whom? I'm hardly a naive Internet user. Anyone actually looking into the matter. The Cisco "fair-queue" command was introduced in IOS 11.0 according to < http://www.cisco.com/en/US/docs/ios/12_2/qos/command/reference/qrfcmd1.html#wp1098249> to somewhat handle the problem. I have no idea when this was in time, but I guess early 90:ties? 200ms is good; but it is often up to multiple *seconds*. Resulting latencies on broadband gears are often horrific: see the netalyzr plots that I posted in my blog. See: I know of the problem, it's no news to me. You don't have to convince me. I've been using Cisco routers as a CPE because of this for a long time. Interestingly I've just tried to enable WRED on a Cisco 877 (advsecurity 15.1) and the random-detect commands are missing. Cisco's feature navigator says it's supported though. Weird. Also, there doesn't appear to be a way to enable fair-queue on the wireless interface. Is fair-queue seen as a bad strategy for wireless and it's varying throughput/goodput rates? And finally it doesn't support inbound shaping so I can't experience with trying to build the queues on it rather than the DSLAM. I'm a little nonplussed to be honest. However, I did notice the output queue on the dialler interface defaults to 1000 packets. (Perhaps that's a hangover from when it had to queue packets whilst dialling? I've come too late to networking to know). Reducing that number to 10 (~60ms @ 1500 bytes @ 8Mbps) has noticeably increased the latency response and fairness of the connection under load. Sam
Current thread:
- TCP congestion control and large router buffers Vasil Kolev (Dec 09)
- Re: TCP congestion control and large router buffers Mikael Abrahamsson (Dec 09)
- Message not available
- Re: TCP congestion control and large router buffers Mikael Abrahamsson (Dec 13)
- Message not available
- Re: TCP congestion control and large router buffers Mikael Abrahamsson (Dec 14)
- RE: TCP congestion control and large router buffers George Bonser (Dec 14)
- RE: TCP congestion control and large router buffers Mikael Abrahamsson (Dec 14)
- Message not available
- Re: TCP congestion control and large router buffers Mikael Abrahamsson (Dec 09)
- Re: TCP congestion control and large router buffers Jim Gettys (Dec 20)
- Re: TCP congestion control and large router buffers Mikael Abrahamsson (Dec 20)
- Re: TCP congestion control and large router buffers Sam Stickland (Dec 21)
- Re: TCP congestion control and large router buffers Fred Baker (Dec 21)
- Re: TCP congestion control and large router buffers Jim Gettys (Dec 22)
- Re: TCP congestion control and large router buffers Fred Baker (Dec 22)
- RE: TCP congestion control and large router buffers George Bonser (Dec 22)
- Re: TCP congestion control and large router buffers Carsten Bormann (Dec 23)
- <Possible follow-ups>
- TCP congestion control and large router buffers Jim Gettys (Dec 14)