By Phil, SamKnows Broadband
Jul 28, 2008

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P2P (peer to peer) traffic is seldom out of the news either because its most popular use is for pirating copyright material or because ISPs are throttling it to reduce the impact on their network.

In the USA a bit of deep academic thinking has gone into seeking ways of addressing the traffic issue, while potentially increasing the efficiency and speed of the P2P networks themselves. Calling itself "P4P" the new approach involves managing P2P traffic in order to make maximum use of local peers rather than the apparently more random selection of peers usually experienced. In effect the P2P protocols are steered to select peers on the same network so that a large ISP can avoid a lot of P2P traffic going over their peering arrangements to other ISPs.

This approach may not work too well in the current BT Wholesale architecture where the system bottlenecks are the "BT Central" connections between ISPs and the BT network. The BT IPStream system was built as a "point to multipoint" arrangement, traffic carried over ATM between two customers of the same ISP has to transit twice over the BT Central to the ISP and back out again.

However as BT Wholesale based ISPs move towards the IP based 21CN architecture there may be increased opportunity to localise traffic perhaps around the 10 major BT interconnect nodes. The P4P approach may also benefit LLU operators who tend to have IP architecture already and could in principle localise at least part of their P2P traffic at an exchange or regional centre.

In the USA Comcast and Verizon have said that they will use the P4P approach and not need to throttle P2P traffic. During the P2P test involving Pando Networks the amount of P2P content delivered to Verizon subscribers from inside its network grew from 2 percent to 50 percent.

The original concept of Bittorrent was to use free or underutilised network capacity at the downloaders end to redistribute files to other downloaders. Effectively this moves the cost (and control) of distribution servers and bandwidth from the original publisher over to the recipients. The service providers who receive a fixed fee from their customers then find they are handling large traffic flows to publish someone else's content. Perhaps the P4P approach will moderate the cost impact on ISPs and restore the balance a little so that P2P doesn't become "protocol non grata" on ISP networks.
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