On Sun, 9 Feb 2014, Dave Taht wrote:
The second largest problem with original cablelabs study is that it only analyzed traffic at one specific (although common) setting for cable operators, 20Mbits down, and 5 Mbits up. A common, lower setting should be analyzed, as well as more premier services. Some tweaking of codel derived technologies (flows and quantum), and of pie (alpha and beta) are indicated both at lower and higher bandwidths for optimum results. Additionally the effects of classification, notably of background traffic, has not been explored.
Just as a data point, currently Comhem in Sweden offers a DOCSIS based cable-Internet service of up to 500/50 (500 down, 50 up).
What would be of great interest would be to test this kind of service in several modes, including having 10 of those on the same CMTS port and congesting both up and downstream of the cable system itself (because there isn't 500 megabit/s total upstream capacity to support 10 subscribers all trying to use 50 megabit/s per user. Same thing downstream. Would be very interesting to see how these users interacted with each other combined with LEDBAT and having TCP flows that didn't incur too much latency for the individual user, whilst assuring that each subscribed line got its fair share of bandwidth from the system.
**** The upload saturation problem shown in the study Bittorrent clients have evolved to where, out of the box, there is a very low rate limit set, typically in the range of 50-150KBytes/sec. This makes bittorrent uploads a non-problem for most people. Still, benchmarking each of these phases would be worthwhile. Torrent can be fixed.
Well, users still would like to set the upload rate to something close to what they have purchased, and still have it yield to other traffic that happens to need the upstream bw, so further study would be great.
Another problem with VOIP is "creeping delay", where a voip queue builds and builds and then delivers or drops a full boatload of packets to catch up. I have experienced this on multiple wifi based voip sessions where I ended up with seconds of delay on the line over time...
This was a big problem 5+ years ago, where I think the PDV (jitter) buffer just grew, and never shrunk again even if network conditions improved. I haven't experienced this lately, so for instance Skype must have fixed this.
-- Mikael Abrahamsson email: [email protected] _______________________________________________ aqm mailing list [email protected] https://www.ietf.org/mailman/listinfo/aqm
