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Re: Can P2P applications learn to play fair on networks?
- From: Rich Groves
- Date: Mon Oct 22 16:08:45 2007
I'm a bit late to this conversation but I wanted to throw out a few bits of
info not covered.
A company called Oversi makes a very interesting solution for caching
Torrent and some Kad based overlay networks as well all done through some
cool strategically placed taps and prefetching. This way you could "cache
out" at whatever rates you want and mark traffic how you wish as well. This
does move a statistically significant amount of traffic off of the upstream
and on a gigabit ethernet (or something) attached cache server solving large
bits of the HFC problem. I am a fan of this method as it does not require a
large foot print of inline devices rather a smaller footprint of statics
gathering sniffers and caches distributed in places that make sense.
Also the people at Bittorrent Inc have a cache discovery protocol so that
their clients have the ability to find cache servers with their hashes on
I am told these methods are in fact covered by the DMCA but remember I am no
Feel free to reply direct if you want contacts
From: "Sean Donelan" <[email protected]>
Sent: Sunday, October 21, 2007 12:24 AM
To: <[email protected]>
Subject: Can P2P applications learn to play fair on networks?
Much of the same content is available through NNTP, HTTP and P2P. The
content part gets a lot of attention and outrage, but network engineers
seem to be responding to something else.
If its not the content, why are network engineers at many university
networks, enterprise networks, public networks concerned about the impact
particular P2P protocols have on network operations? If it was just a
single network, maybe they are evil. But when many different networks
all start responding, then maybe something else is the problem.
The traditional assumption is that all end hosts and applications
cooperate and fairly share network resources. NNTP is usually considered
a very well-behaved network protocol. Big bandwidth, but sharing network
resources. HTTP is a little less behaved, but still roughly seems to
share network resources equally with other users. P2P applications seem
to be extremely disruptive to other users of shared networks, and causes
problems for other "polite" network applications.
While it may seem trivial from an academic perspective to do some things,
for network engineers the tools are much more limited.
User/programmer/etc education doesn't seem to work well. Unless the
network enforces a behavor, the rules are often ignored. End users
generally can't change how their applications work today even if they
Putting something in-line across a national/international backbone is
extremely difficult. Besides network engineers don't like additional
in-line devices, no matter how much the sales people claim its fail-safe.
Sampling is easier than monitoring a full network feed. Using netflow
sampling or even a SPAN port sampling is good enough to detect major
issues. For the same reason, asymetric sampling is easier than requiring
symetric (or synchronized) sampling. But it also means there will be
a limit on the information available to make good and bad decisions.
Out-of-band detection limits what controls network engineers can implement
on the traffic. USENET has a long history of generating third-party cancel
messages. IPS systems and even "passive" taps have long used third-party
packets to respond to traffic. DNS servers been used to re-direct
subscribers to walled gardens. If applications responded to ICMP Source
Quench or other administrative network messages that may be better; but