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Peer-peer and Application-level Networking CS 218 Fall 2003

Peer-peer and Application-level Networking CS 218 Fall 2003. Multicast Overlays P2P applications Napster, Gnutella, Robust Overlay Networks Distributed Hash Tables (DHT) Chord CAN Much of this material comes from UMASS class slides. Resilient Overlay Networks. Overlay network:

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Peer-peer and Application-level Networking CS 218 Fall 2003

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  1. Peer-peer and Application-level NetworkingCS 218 Fall 2003 • Multicast Overlays • P2P applications Napster, Gnutella, Robust Overlay Networks • Distributed Hash Tables (DHT) Chord CAN Much of this material comes from UMASS class slides

  2. Resilient Overlay Networks Overlay network: • applications, running at various sites • create “logical” links (e.g., TCP or UDP connections) pairwise between each other • each logical link: multiple physical links, routing defined by native Internet routing • let’s look at an example:

  3. Internet Routing • BGP defines routes between stub networks Internet 2 Berkeley.net UMass.net C&W Mediaone UCLA Noho.net

  4. Internet Routing • BGP defines routes between stub networks Internet 2 Berkeley.net UMass.net C&W Mediaone Noho-to-UMass UCLA Noho.net

  5. Internet Routing • BGP defines routes between stub networks Internet 2 Berkeley.net UMass.net C&W Mediaone Noho-to-Berkeley UCLA Noho.net

  6. Internet Routing Congestion or failure: Noho to Berkely BGP-determined route may not change (or will change slowly) Internet 2 Berkeley.net UMass.net C&W Mediaone Noho-to-Berkeley UCLA Noho.net

  7. Internet Routing Noho to UMass to Berkeley • route not visible or available via BGP! • MediaOne can’t route to Berkeley via Internet2 Congestion or failure: Noho to Berkely BGP-determined route may not change (or will change slowly) Internet 2 Berkeley.net UMass.net C&W Mediaone Noho-to-Berkeley UCLA Noho.net

  8. RON: Resilient Overlay Networks Premise: by building application overlay network, can increase performance, reliability of routing application-layer router Two-hop (application-level) noho-to-Berkeley route

  9. RON Experiments • Measure loss, latency, and throughput with and without RON • 13 hosts in the US and Europe • 3 days of measurements from data collected in March 2001 • 30-minute average loss rates • A 30 minute outage is very serious! • Note: Experiments done with “No-Internet2-for-commercial-use” policy

  10. Loss Rate RON Better No Change RON Worse 10% 479 57 47 20% 127 4 15 30% 32 0 0 50% 20 0 0 80% 14 0 0 100% 10 0 0 An order-of-magnitude fewer failures 30-minute average loss rates 6,825 “path hours” represented here 12 “path hours” of essentially complete outage 76 “path hours” of TCP outage RON routed around all of these! One indirection hop provides almost all the benefit!

  11. RON Research Issues • How to design overlay networks? • Measurement and self-configuration • Understanding performance of underlying net. • Fast fail-over. • Sophisticated metrics. • application-sensitive (e.g., delay versus throughput) path selection. • Effect of RON on underlying network • If everyone does RON, are we better off?

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