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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

OverQoS: Offering QoS using Overlays

Lakshmi

Sahara Retreat, 2003


What is overqos
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


How does overqos work

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


How does overqos work1

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!


Controlled loss virtual link clvl

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


Overqos services customers
OverQoS Services, Customers

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




Conclusions
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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