IETF wants to improve the routing of P2P data traffic

An Internet Engineering Task Force (IETF) working group has recently started to look into improving the routing of Peer-to-Peer (P2P) data traffic. At the first official meeting of the ALTO working group (Application-Layer Traffic Optimization) in Minneapolis last week, several developer groups proposed ways of locating the nearest P2P host. Internet service providers (ISPs) and carriers want to avoid unnecessary and expensive P2P data traffic "diversions" across network boundaries. This would save money for providers and downloading time for users.

"The drafts mainly differ in where they provide the routing information", explained Anja Feldmann, professor of the T-Lab institute at Berlin University of Technology, on the fringe of the meeting. Feldmann and her group have developed a draft which recommends providing information about the P2P topology at the ISP. "Every ISP would operate an 'oracle' or ALTO server", explained Feldmann. This could be used to request information about P2P hosts in the vicinity. One advantage of having the providers present the server information is that the servers can also be used to support a provider's potential traffic management measures, she said. However, Feldmann believes that many providers may be reluctant to pass on information about their network topologies to third parties.

By contrast, a group organised by US provider Comcast proposes to pass the peering information on to the application providers. In a joint draft by Comcast and BitTorrent, the former rivals also explain how ISPs are to export the information to the application providers. Feldmann said that Comcast's proposal – which aims at providing more information at the host – is also an effort to compensate for the former policy of blocking P2P traffic.

A draft by Qualcomm supports a "co-operative" strategy. It proposes to supply the information for optimising P2P routing both at the network providers and the application providers. The draft said that unilateral routing recommendations – that is, either purely network related information that benefits ISPs, or purely application related information that disregards the network's topology – are unattractive to the respective other party.

The potential savings make a future ALTO standard attractive to providers. In Minneapolis, Comcast's Rich Woundy presented the results PDF of a trial run between 2nd and 17th July. During this time, Pando Networks shared a file of 21MB in size among its users, and the distribution of this file across four different networks was subsequently measured. The first ever test for a cable network resulted in the inbound inter-domain data traffic at Comcast being reduced by 34 per cent, the outbound traffic by 80 per cent. However, the trial also exposed a number of limitations, said Woundy. The so-called P4P model does not solve the problem of a weak last mile. In addition, P4P can't be used for unmanaged content data traffic, which constitutes the majority of data traffic.