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OverQoS: Offering QoS using Overlays

OverQoS: Offering QoS using Overlays. Lakshmi Sahara Retreat, 2003. What is OverQoS?. Embed QoS functionality in Internet via overlays Overlay nodes implement QoS functions No support needed from IP routers Challenges Nodes not connected to congested points,

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OverQoS: Offering QoS using Overlays

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  1. OverQoS: Offering QoS using Overlays Lakshmi Sahara Retreat, 2003

  2. What is OverQoS? • Embed QoS functionality in Internet via overlays • Overlay nodes implement QoS functions • No support needed from IP routers • Challenges • Nodes not connected to congested points, • have no control over cross-traffic • cannot avoid losses (reducing sending rate doesn’t help!) • Why Overlays? • Previous QoS architectures have yet to be deployed • Overlay-model empowers third-party providers to provide some form of QoS

  3. N-TCP pipe Entry Node Exit Node Overlay Traffic Redundant Traffic • Step 2: Distribute bandwidth and loss amongst flows Flow 1 Scheduler Rate Ctrl Flow 2 How does OverQoS work? • Step 1: Aggregate Loss and Bandwidth Control

  4. Flow 1 Overlay Node Overlay Node Overlay Node Flow 2 Flow 3 How does OverQoS work? • Step 3: Provide QoS guarantees (bandwidth,loss) to a • flow by “stitching” guarantees on overlay links. • Step 4: How to perform QoS-routing of multiple flows • with different requirements on an overlay network? • Challenge: Links with varying bandwidth, loss • Ongoing work!

  5. c(t), q Buffer mgmt & Scheduling & Traffic regulator De- coder Coder control plane CLVL Controlled-Loss Virtual Link (CLVL) • Two parameters: • Statistical bound on loss rate, q (<= p; typically << p) • Capacity, c(t), possibly time-varying • Can prove: if offered load < c(t), then loss rate < q • How is c(t) determined? • Given f(t) to be the redundancy factor: c(t) = b(t)( 1- f(t)) Flow 1 b(t), p(t) Flow 2 Flow n OverQos Node

  6. OverQoS Services, Customers OverQoS Customers: Streaming media server, Leasing overlay networks, Pipe abstraction for large institutions

  7. Extractable Bandwidth

  8. What bandwidth guarantees?

  9. Conclusions • Inferences from our study: • FEC+ARQ has better overhead characteristics than FEC-based CLVL implementation • Loss recovery is not possible during large periods of bursts • OverQoS can be used to provide some form of statistical bandwidth guarantees • Limitations: • Need more statistical measurements across overlay links • Many overlay links (except cable modems) are not lossy.

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