By: Art Reisman
Art Reisman is the CTO of APconnections. He is Chief Architect on the NetGladiator and NetEqualizer product lines.
I live in a nice suburban neighborhood with both DSL and Cable service options for my Internet. My speed tests always show better than 10 megabits of download speed, and yet sometimes, a basic YouTube or iTunes download just drags on forever. Calling my provider to complain about broken promises of Internet speed is futile. Their call center people in India have the patience of saints; they will wear me down with politeness despite my rudeness and screaming. Although I do want to believe in some kind of Internet Santa Claus, I know first hand that streaming unfettered video for all is just not going to happen. Below I’ll break down some of the limitations for video over the Internet, and explain some of the seemingly strange anomalies for various video performance problems.
The factors dictating the quality of video over the Internet are:
1) How many customers are sharing the link between your provider and the rest of the Internet
Believe it or not, your provider pays a fee to connect up to the Internet. Perhaps not in the same exact way a consumer does, but the more traffic they connect up to the rest of the Internet the more it costs them. There are times when their connection to the Internet is saturated, at which point all of their customers will experience slower service of some kind.
2) The server(s) where the video is located
It is possible that the content hosted site has overloaded servers and their disk drives are just not fast enough to maintain decent quality. This is usually what your operator will claim regardless if it is their fault or not. :)
3) The link from the server to the Internet location of your provider
Somewhere between the content video server and your provider there could be a bottleneck.
4) The “last mile” link between you and your provider (is it dedicated or shared?)
For most cable and DSL customers, you have a direct wire back to your provider. For wireless broadband, it is a completely different story. You are likely sharing the airwaves to your nearest tower with many customers.
So why is my video slow sometimes for YouTube but not for NetFlix?
The reason why I can watch some NetFlix movies, and a good number of popular YouTube videos without any issues on my home system is that my provider uses a trick called caching to host some content locally. By hosting the video content locally, the provider can insure that items 2 and 3 (above) are not an issue. Many urban cable operators also have a dedicated wire from their office to your residence which eliminates issues with item 4 (above).
Basically, caching is nothing new for a cable operator. Even before the Internet, cable operators had movies on demand that you could purchase. With movies on demand, cable operators maintained a server with local copies of popular movies in their main office, and when you called them they would actually throw a switch of some kind and send the movie down the coaxial cable from their office to your house. Caching today is a bit more sophisticated than that but follows the same principles. When you watch a NetFlix movie, or YouTube video that is hosted on your provider’s local server (cache), the cable company can send the video directly down the wire to your house. In most setups, you don’t share your local last mile wire, and hence the movie plays without contention.
Caching is great, and through predictive management (guessing what is going to be used the most), your provider often has the content you want in a local copy and so it downloads quickly. However, should you truly surf around to get random or obscure YouTube videos, your chances of a slower video will increase dramatically, as it is not likely to be stored in your provider’s cache.
Try This: The next time you watch a (not popular) YouTube video that is giving your problems, kill it, and try a popular trending video. More often than not, the popular trending video will run without interruption. If you repeat this experiment a few times and get the same results, you can be certain that your provider is caching some video to speed up your experience.
In case you need more proof that this is “top of mind” for Internet Providers, check out the January 1st 2012, CED Magazine article on the Top Broadband 50 for 2011 (read the whole article here). #25 (enclosed below) is tied to improving video over the Internet.
#25: Feeding the video frenzy with CDNs
So everyone wants their video anywhere, anytime and on any device. One way of making sure that video is poised for rapid deployment is through content delivery networks. The prime example of a cable CDN is the Comcast Content Distribution Network (CCDN), which allows Comcast to use its national backbone to tie centralized storage libraries to regional and local cache servers.
Of course, not every cable operator can afford the grand-scale CDN build-out that Comcast is undertaking, but smaller MSOs can enjoy some of the same benefits through partnerships. – MR
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