[ NNSquad ] Re: Google, caching, and "network neutrality"

["Don Bowman" <don@sandvine.com>]

David Ulevitch writes:

>By bringing YouTube videos and other content physically closer to 
>end users, site operators can improve page load times for videos 
>and Web pages. In addition, these solutions help broadband providers 
>by minimizing the need to send traffic outside of their networks and 
>reducing congestion on the Internet's backbones. In fact, caching 
>represents one type of innovative network practice encouraged by the 
>open Internet.
>
>Perhaps because Mr. Whitt is a corporate executive rather than an 
>engineer, he is not aware that YouTube videos are in fact not 
>cacheable by design. As mentioned at
>
>http://wiki.squid-cache.org/ConfigExamples/DynamicContent/YouTube
>

Actually, this isn't quite true. Youtube can be effectively cached.
But it requires some slightly different techniques than typical
HTML. One has to recognise that a given URL is the same
video as another URL, and make a decision of which content flows
to the cache rather than just port-80.

We are doing this with some of our customers in conjunction with
a caching partner. Two methods are available for detecting that
url's are equivalent: inspecting within the flash meta info,
and/or a hash of the file contents. This is done using a 
combination of deep packet inspection, a policy to splice
the tcp session to the cache, and a cache device which is youtube
(flash video) aware. This is typically done in (e.g. island nations)
places with highly over-subscribed transit. It's not common practice
as far as I know in places with economical transit connections.

Simpler to peer with or add local servers, but not always feasible,
The cache is a great way to improve efficiency and internet
experience for certain content types. It's a negative to experience
if all HTTP traffic is routed through it since it increases latency
as a proxy.

--don