4 ms·
I think people are misunderstanding this report, which is surely their intent. This isn't a chart of how well each ISP performs in general, or even how well the
by trotsky 16y ago
I think people are misunderstanding this report, which is surely their intent. This isn't a chart of how well each ISP performs in general, or even how well they perform in relation to each other.
As a baseline, all of the ISPs on this list that I've used (ftth, coax and dsl providers) have been able to push to 90%-100% of quoted line speed 99% of the time.
What this chart shows is netflix performance, which is quite different than general network performance. What goes into netflix performance? Total netflix service load, CDN pop load, CDN circuit size, SLA/QOS terms, the choices the netflix client makes about adaptive bitrates and shaping the provider applies to the traffic.
Take a look at the US chart and note the correlations in spikes and dips across all providers at certain times - 10/21 peak, 10/23 valley, 11/13 valley etc. These are indications of aggregate stream load netflix wide and are an indication that netflix manages their peak throughput to be pretty close to their max throughput (as well they should). But it's also a strong indication that if 10% of netflix customers switched to a competitor overnight average stream performance for netflix would jump noticeably, perhaps even 10%.
How their adaptive streaming works is another huge factor. First they measure your current performance to the CDN POP and then explicitly chooses to use only 60% of that[1]. So add 40% to all the ISP numbers out of the gate. TCP+HTTP overhead is another ~4%. Downloading something else while you stream? If the streaming sees more than a few headroom faults (ie 1000ms worth of data takes more than 600ms) the system will quickly adapt down in bitrate trying to do its best to never hard fault (buffering). It likely is considerable more conservative in moving the stream speed back up. Customer using 802.11b? Max throughput there is ~5mbps, so netflix will use a max of 3mbps. In an urban area on a congested channel? You may only see 1-2mbps at times. Microwave on? etc.
Lastly, with the news that netflix is 20% of ISP traffic at night the network providers have every incentive to manage that traffic down. Look at the best US performer at ~2700kbits. The fastest HD stream is 4800kbits - Nearly twice the speed. Worst case if an ISP allowed full rate streaming they might increase their peak network load by 10% or more.
Who was it that announced netflix is now 20% of night time traffic? Our old friend sandvine, provider of the DPI gear made famous by comcast using it to throttle bittorrent. This tells us two things - 1) sandvine is on net at at least a few major broadband providers and 2) by announcing that number they are implicitly telling network managers that they can help reduce that traffic.
Netflix makes it very easy to do fine grained control on bitrates. If you are watching the HTTP headers you know exactly which customers are on which stream rate without having to count the throughput. Most users won't notice a QOE change from 4800kbits to 3200kbits. Want to cut your network traffic? Use DPI to identify the higher rates and label them bulk-toofast. Then either explicitly rate limit them, give them a low queue priority or simply route the acks through a big buffer under performing router or indirect route. Once the adaptive bitrate slows down to a rate you like switch the label. The more subtle of these methods are much, much harder to detect than the comcast RST's were, and wouldn't technically violate any net neutrality rules in place.
[1] http://www.breakingpointsystems.com/community/blog/emulating-netflix-delivering-video-through-the-cloud/ http://www.breakingpointsystems.com/community/blog/emulating...