Well, maybe management of overlays works and also maybe it makes economic sense (for who?). This would have to be proven however not in papers, but in running systems as well in market for acceptance. Too bad the Skype and Bittorrent folks who have proven both do not care to participate in this debate. As an engineer, I may be excused for not believing in p2p management, until I see the measurements and numbers.
> no one knows what happens if the overlay population exceeds some large > number, say >100M, sinces no overlays have been deployed or simulated at that > size - does it degrade >gracefully or become inoperable My Skype panel shows right now 16,659,464 people on line and I believe they have 400 million subscribers. Skype works exceedingly well for our daily family a/v sessions, coast to coast. Does Skype have network management agreements with all the ISPs their p2p is crossing? :-) >but depending on user expectations for service quality and willingness to pay This alone is worth a good beer BOF. Let's plan for one. Henry On 3/18/09 11:01 AM, "John Buford" <[email protected]> wrote: 2009/3/16 Henry Sinnreich [email protected] I fully agree, since some naïve folks out there (including me) think that: 1. p2p is self organizing - not managed - unless fixing node software is called management. 2. p2p works across the Internet and crosses many ISP networks, several times even for any one ISP. The p2p operator may not even be in friendly relations with some the ISPs and compete with them. Henry, Current overlays have limitations. Here's a partial list of problems, I expect others on this list can add more: - potentially long delays to respond to and correct from network partitions - inability to detect and correct load imbalance, such as flash crowd effect - inability to detect and respond to DDOS attacks - inability to enforce different classes of service for different peers - overlay instability at high churn rates, that might be caused by increases in the number of mobile peers - no one knows what happens if the overlay population exceeds some large number, say 100M, sinces no overlays have been deployed or simulated at that size - does it degrade gracefully or become inoperable While there are some research proposals to address some of these problems individually, it is safe to say that no single design covers all of them. In general as long as there are overlay algorithm performance areas which can not be automatically detected and corrected by self-organizing algorithms, then there is a need for management agent(s) to be able to monitor and intervene. Sure this boundary is likely to shift over time as algorithms get better. And monitoring the overlay can help the development of better algorithms. Here's a detailed discussion of the limits of today's P2P systems w.r.t. self-organization: B. Biskupski, J. Dowling, and J. Sacha, Properties and mechanisms of self-organizing MANET and P2P systems, ACM Trans. Auton. Adapt. Syst. 2, 1 (March 2007), 34 pp. Here's a look at how overlay management might work: J. Buford, Management of peer-to-peer overlays, International J. of Internet Protocol Technology, Special Issue on Management of IP Networks and Services, Vol. 3, No.1, 2008, 2-12. Bottom line, ideally P2P doesn't need to be managed, but depending on user expectations for service quality and willingness to pay, there could be deployments with overlay operators who provide this for users by managing the overlay. John
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