[ NNSquad ] Re: News: Comcast to end P2P interference

[John Pettitt <jpp@cloudview.com>]

Nick Weaver wrote:
> Also, the lack of topological awareness does hurt BitTorrent, as well
> as the lack of cacheability.  If the ISP is able to say that
> a)  BitTorrent-type protocols can stay in my local loop and
> b)  These flows are ones I CAN cache without being sued
>
> BitTorrent type flows become far less objectionable.
>
>   
There are a lots of issues in that short text.   Topology is relatively 
easy - bittorrent clients are introduced to each other by a tracker and 
there is no reason why the tracker shouldn't make an effort to introduce 
neighbors based on shortest prefix or AS number.     You can't do that 
for all connection because it would break the graph and lead to 
fractured subnets but a smart tracker will make a difference (although 
peer exchange between clients complicates this).

Discovering what is and is not "safe to cache" is a can of worms 
technically and legally.  In theory, if everybody played nice, you could 
use the infohash and look up the stream to see if it's known to be not 
pirate.      However this doesn't work in practice because firstly it's 
not the data that determines legitimacy it's the user and you can't tell 
if I have a license from looking at the connection.   Secondly just 
looking at the infohash is subject to spoofing (wrap the real data 
inside a fake infohash header) assuming both clients know of the spoof 
they just strip the fake header and proceed.   Then there is encryption 
to complicate things further.  Legally once you start inspecting for 
contraband you run the risk of falling out of the DMCA safe harbor 
provisions and becoming liable for the stuff you miss

John