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Service Composition: Breakout Session Summary

Service Composition: Breakout Session Summary

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Service Composition: Breakout Session Summary

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  1. Service Composition: Breakout Session Summary Randy Katz David Culler Summary: Bhaskaran Raman

  2. Discussion topics • Background • Emerging Internet service model • Confederated vs. Overlay model • Issues: • Granularity of composition • Growth trends: copious bandwidth • Service economics

  3. Background • Emerging Internet service model • Structure-less cloud  Structured, with Internet data centers • Portal service built out of pieces • Portal  Appln infra service  Appln specific servers  Overlay networks  Physical topology • Confederated vs. Overlay model • At the network layer • At the service layer

  4. Granularity of services • Heavy-weight pieces • E.g., search engines • Light-weight pieces • E.g., transformation agents • Yahoo portal is an example of heavy-weight composition • Ninja paths: light-weight composition

  5. Composition: beyond functionality • Service composition: flexibile • Can a composed service be robust? • Can we build in a negative feedback loop into the system? • With an event queue based approach to composition? • Can such a mechanism work across machines, across the network? • How to compute reliability of a composed service? • Who to blame when something breaks? • SLAs for services: complex • Yahoo/Google have legal SLA document

  6. Design for decomposition • Design for decomposition: how to design a service so that it can be built from pieces meaningfully • End-2-End argument in service composition: • If we want to have admission control at the end, how to effect this when the bottleneck is in the middle? • How to design protocols to allow for composition? • Expose more information • E.g., HTTP/1.0 has little support for caches, HTTP/1.1 has a lot of support

  7. Internet Growth Trends • Optical technology being deployed in a big way • 1.6 Tb/s – 24 Tb/s in the backbone • Where to place services, and how many service instances? • Does it matter, if backbone bandwidth is free and infinite? • What about the people cost of managing distributed instances? • In storage management, people cost is 3-4 times more than system cost • Network access cost dropping: can buy optical link for $2K a month

  8. Service distribution vs. Centralization • Might depend on granularity • Hard to distribute search engine • Easier to distribute Akamai servers: soft-state • People cost: • HP: 50,000 node computer network • $10K per server • One person can manage 10 servers • Service in the telephone network are distributed • Might be related to the way the telephone network evolved, and its architecture

  9. Service distribution vs. Centralization • Latency/server-load might be a reason to distribute a service • There are congested parts of the Internet today • Trans-oceanic links • Public-peering points • Distribution: • Over-provisioning may be easier if there are many sites

  10. Service Economics • Composition: economics meets engineering • SLAs are an important part • Trust relations • Management tools for services • What are the ones required for composed services • Diagnose and isolate problems • Composition by user (dynamic) vs. composition by service providers (less dynamic)