OverQoS: Offering QoS using Overlays

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OverQoS Offering QoS using Overlays

• Lakshmi
• Sahara Retreat, 2003

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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
  doesnt help!)
• Why Overlays?
• Previous QoS architectures have yet to be
  deployed
• Overlay-model empowers third-party providers to
  provide some form of QoS

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How does OverQoS work?

• Step 1 Aggregate Loss and Bandwidth Control

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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!

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Controlled-Loss Virtual Link (CLVL)

• Two parameters
• Statistical bound on loss rate, q (lt p
  typically ltlt p)
• Capacity, c(t), possibly time-varying
• Can prove if offered load lt c(t), then loss rate
  lt 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
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OverQoS Services, Customers
OverQoS Customers Streaming media server,
Leasing overlay networks, Pipe abstraction for
large institutions
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Extractable Bandwidth
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What bandwidth guarantees?
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Conclusions

• Inferences from our study
• FECARQ 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.