Supercharged File Sharing
Cooperating with file-sharing networks could avert congestion.Technology Review
15 December 2008
By Kurt Kleiner
Internet service providers (ISP) struggle with increasing traffic from
peer-to-peer file-sharing networks, some have resorted to simply
throttling this data, attracting ire from both users and regulators.
Under a scheme that should be rolled out early next year, some ISPs
plan to take a different approach: cooperating with file-sharing
networks so that they share data more effectively.
scheme is called Provider Portal for Applications (P4P), and it's a
voluntary, open standard that requires ISPs to share some information
about how their networks are laid out. Initial tests have shown that
the P4P framework can dramatically speed up download times for file
sharers while also reducing the bandwidth costs for ISPs.
file sharing has exploded over the past decade, driven by increasing
consumer bandwidth and growing demand for large amounts of data. Rather
than serve files from a centralized location, file-sharing networks
scatter pieces of among thousands of individual computers and help
users find and download this data. File sharing now accounts for about
70 percent of all network traffic, and some ISPs have found it hard to
deal with the increased load. In August, Comcast was rebuked by the
Federal Communications Commission for trying to throttle peer-to-peer
traffic on its network.
The new protocol reduces file-trading
traffic by having ISPs reveal some internal network information to
peer-to-peer "trackers"--servers that are used to locate files for
downloading. Trackers can then use this network information to arrange
file sharing more efficiently, by connecting computers that are nearer
and sharing files at the lowest resource cost to the ISPs involved. As
an example, suppose someone running a BitTorrent client tries to
download an MP3. As it stands, the file might come from a computer
halfway around the world, even if someone next door also happens to
have a copy. By using P4P, the tracker knows to connect computers that
are closer together, requiring bits to travel less distance.
knew, as a peer-to-peer company, that in order for peer to peer to
become successfully commercialized, network operators had to be
cooperative," says Robert Levitan, CEO of Pando Networks, a company
that offers commercial peer-to-peer content delivery services. "Instead
of blocking traffic, they had to get involved in it."
Pando is a
founding member of the P4P Working Group, a consortium set up in 2007
to develop and test new technologies to make P2P more efficient.
Members include the ISPs Verizon and Comcast, the peer-to-peer software
business BitTorrent, the network equipment manufacturer Cisco Systems,
and academic institutions including Yale and Washington University.
tests conducted in March by Yale researchers, Pando, Verizon, and
Telefonica Group suggest that the system could cut the average distance
that data has to travel from 1,000 miles to 160 miles, and reduce the
number of connections that have to be made through major hubs from 5.5
to 0.69. This would help ISPs avoid the costs incurred when information
is handed between major networks. The approach could also benefit
users, by increasing download speeds by an average of 20 percent,
according to the same tests.
A more recent study carried out
this fall with Comcast, Verizon, and AT&T showed that peer-to-peer
download speeds could increase 50 to 150 percent using the technology.
And the amount of content that is delivered entirely within each ISP
should increase from 14 percent to as much as 89 percent.
the P4P approach is not without its challenges. The protocol depends on
ISPs calculating and making available "p-distance values" to
peer-to-peer trackers, to tell them how best to connect different file
sharers. There are also legal questions. Because many files traded on
peer-to-peer networks violate copyright, ISPs will want to make sure
cooperating with P2P networks won't make them responsible.
Richard Woundy, senior vice president for software and applications
with Comcast, admits that the idea is appealing. "The ISP benefits
because traffic isn't going over as much infrastructure," he says.
"It's staying within a metro area, or at least staying within the ISP.
It's not going over a transit link to an upstream provider."
Pasko, principal member of the technical team at Verizon, says that
Pando and Verizon have plans to roll out a P4P implementation soon,
possibly by the end of January. The P4P working group has also
submitted an application with the Internet Engineering Task Force to
seek official approval for the P4P standard. And Pasko doesn't think
that legal problems are likely. "P4P itself doesn't increase our legal
exposure," he says. "That's because we're offering optimization
guidance. We don't have any information on what that content is."
is also interested in implementing the technology, says Barry Tishgart,
vice president for Internet services for the company. "Our inclination
is, we want to do it. The results of our trial are very positive," he
says. But the tests carried out so far have been relatively small: the
one performed this fall shared a single 21-megabyte video file, which
was downloaded 15,000 times. So Tishgart wants to see what happens when
larger file sizes and large swarms of peers try to download a popular
Finally, the success of the scheme depends on the thousand
or more peer-to-peer trackers that currently exist agreeing to use the
P4P protocol. Tishgart says that they tend to be suspicious of the
ISP's motives. But if they see performance gains for their users and no
downside, then they may be much more likely to cooperate.