Paper Group: 20 Overlay Networks 2 nd March, 2004

1. Chetan Hiremath CSE525 – Advanced Networking, Winter 2004 Oregon Graduate Institute Paper Group: 20Overlay Networks2nd March, 2004 Above papers are original works of respective authors, referenced here for academic purposes only Papers Discussed: - A Routing Underlay for Overlay networks- Topologically-Aware Overlay Construction and Server Selection- Routing in Overlay Multicast Networks

2. Paper Group Objectives • Design overlay services for making informed application specific routing decisions • Propose a binning scheme for network overlay construction and server selection • Introduce routing algorithms for overlay multicast networks & study their performance.

3. Routing Overlay Networks • Used to deploy network services that cannot leverage underlying Internet directly. • File sharing, CDN, Object Location, QoS overlays, etc. • Overlays often use “traceroute” and “ping” for network probing • Experiments have limited scalability up to 50 nodes • Architecture not scalable • Introduce Routing Underlay • Sits between overlay networks & underlying Internet

4. Routing Underlay • Goals: • Provide a graph of known network connectivity at specific resolution • Expose actual route taken by packet from SRC to DST • Report topological facts about specific paths between pair of points • Topology Probing Kernel exposed primitives • GetGraph(), GetPath(src, dst), GetDistance(target, metric) • Library of routing services • DisjointPaths(..), NearestNodes(...), BuildMesh(..) Service Overlay Networks Library of Routing Services Topology Probing Kernel Raw Topology Information Non scalability of ping and traceroute to “encourage” designers to adopt this approach

5. Performance and Observations • Finding k smallest-latency neighbors • BGP routers need to export routing tables to overlay networks • Transit AS force usage of latency probes • Discourage pushing any dynamic capability into BGP routers

6. Topologically-Aware Overlay Construction • Propose a practical and scalable method for gathering topological information • Non scalability of traceroute and ping • Scalability & Practicality more important than accuracy • Applications do not require exact topological information, but need sufficient hints on relative position of Internet hosts • Tie Overlay construction with underlying Internet topology • Latency is direct indicator of performance seen by end nodes; can be measured in light weight non intrusive manner

7. Distributed Binning • Set of nodes independently partition into disjoint “bin” • Nodes within a single bin are relatively closer to one another than to nodes not in their bin • Small set of Landmark machines geographically distributed over the Internet to “measure” latency • Check average inter-bin and intra-bin latencies to ensure binning does the job

8. Distributed Binning Example

9. Distributed Binning Example • TS-10K and TA-1K: Transit-sub topologies with 10,000 and 1000 nodes • PLRG1 and PLRG2: Power-Law Random Graphs with 1166 and 1779 nodes • NLANR: National Lab for Applied Network Research based Active Measurement Project • Consisting of 100 active monitors that exchange information

10. Distributed Binning Example • TS-10K and TA-1K: Transit-sub topologies with 10,000 and 1000 nodes • PLRG1 and PLRG2: Power-Law Random Graphs with 1166 and 1779 nodes • NLANR: National Lab for Applied Network Research based Active Measurement Project • Consisting of 100 active monitors that exchange information

11. Binning based Server Selection • If there exists one or more servers within the same bin as the client, then the client is redirected to a random server from its own bin • If no server exists within the same bin as the client, an existing server from another similar bin

12. Latency Stretch Comparison

13. Routing in Overlay Multicast Networks • Set of distributed Multicast Service Nodes (MSN), communicating with hosts or with each other over standard unicast mechanisms • Optimization of interface BW is primary focus • Balanced Compact Tree (BCT) Algorithm • New node is always attached to the tree at the point that yields smallest diameter in the resulting tree • Iterative Closest Pair (ICP) Algorithm • Select eligible pairs, for which connecting edge has minimum cost • Iterative Compact Component (ICC) Algorithm • Select eligible pairs to minimize diameter of resulting component • Iterative Compact Tree (ICT) Algorithm • Select eligible pairs, with one vertex of each pair in a single tree being constructed, other to minimize tree diameter

14. ICT Example • Geo distance as routing cost and diameter bound of 8000 Km • BDA o/p creates star topology with NY of degree 7 • In second round, degree allocation is loosened by 1, resulting in smaller diameter tree satisfying diameter bound

15. Algorithm Comparison • Geo distance as routing cost and diameter bound of 8000 Km • ICP & ICC benefit in initial rounds of degree adjustment; allowing nearby nodes to be joined together • ICT utilizes increased degree allocation at centrally located nodes and form smaller diameter trees • ICT, combined with degree loosening procedure, is more effective at producing smaller diameter trees Rejection: Session rejected if required MSN interface BW exceeds total unused BW at all MSNs

16. Simulation setup

17. Performance Results

18. Paper Group Objectives • Design overlay services for making informed application specific routing decisions • Adoption is a concern • Propose a binning scheme for network overlay construction and server selection • Binning performs similar to Hotz model; not much improvement • Introduce routing algorithms for overlay multicast networks & study their performance. • Better than above mechanisms

19. Questions ?