I could justify declaring such traffic an attack and blocking the source as malicious.
From: George Skorup (Cyber Broadcasting) Sent: Sunday, April 26, 2015 4:30 PM To: [email protected] Subject: Re: [AFMUG] 450SM sustain bucket throttle not working.. Yep, I see this all the time and Ken is exactly right. The Canopy QoS works exactly as designed, the AP is definitely not delivering more than the sustained rate, but is instead discarding the extra 50%. I've tested this situation thoroughly. Stick a MT simple queue in at the upstream router and the 2X rate traffic stops hitting the AP's ethernet interface, but it's still coming in at double the sustained rate farther upstream. There's no way around it except throwing bandwidth at it. This is CDN traffic. And when the customer thinks they can install one of those "internet download managers" to speed up their connection. The only thing it does is screw with TCP acks or window sizes or something which just puts more traffic on your transit just to be discarded at the congestion point (SM, queue, Procera, whatever). Gotta love it. You'd think with 70% of the internets being streaming video they'd think hmm.. maybe we can cut down on the peering congestion by NOT doing this crap. But no. On 4/26/2015 11:01 AM, Ken Hohhof wrote: Sorry to answer a question with a question, but are you measuring at the SM, or at some upstream router? The reason I ask, is I have seen some CDN traffic that does not seem to follow traditional TCP congestion control. It will send at twice the rate limit, causing 50% packet loss to its own traffic and everything else to that same subscriber. Evidently some TCP geniuses have decided to use latency rather than packet loss as the indicator of congestion, and that the objective is goodput not throughput. Works for last mile technologies like T1 and DSL with big buffers at the head end of the fixed speed serial connection, not so good with the type of rate limit queues we tend to use unless we can provision the queues with big buffers. Probably not your problem, but I thought I’d bring it up just in case. From: Kurt Fankhauser Sent: Sunday, April 26, 2015 10:50 AM To: [email protected] Subject: [AFMUG] 450SM sustain bucket throttle not working.. I have a 450 SM that is rate limited in the SM to 1500kbps download on the sustain side. I noticed last night that this customer was pulling a steady almost 3mbps download for several hours on end. How is this possible? Is there a problem with 13.2 firmware? Its a 3.65ghz SM. see attached. Kurt Fankhauser Wavelinc Communications P.O. Box 126 Bucyrus, OH 44820 http://www.wavelinc.com tel. 419-562-6405 fax. 419-617-0110
