Performance metrics for resilient networks
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Performance Metrics for Resilient Networks. Michael Menth , Jens Milbrandt, Rüdiger Martin, Frank Lehrieder, Florian Höhn. This work was in cooperation with Infosim GmbH & CoKG and supported by the Bavarian Ministry of Economic Affairs. Outline. Motivation

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Performance Metrics for Resilient Networks

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Performance metrics for resilient networks

Performance Metrics for Resilient Networks

Michael Menth, Jens Milbrandt, Rüdiger Martin,

Frank Lehrieder, Florian Höhn

This work was in cooperation with Infosim GmbH & CoKG and supported by the Bavarian Ministry of Economic Affairs


Outline

Outline

  • Motivation

  • Unavailability of the network for end-to-end (e2e) aggregates

    • Calculation

    • Illustration of results

  • Overload probability for links

    • Calculation

    • Illustration of results

  • Summary & outlook


Motivation

Availability of the network

Link failures

Node failures

Link overload

Redirected traffic due to failures

More traffic due to increased user activity (hot spots)

More traffic due to interdomain rerouting

Tool for the assessment of network resilience

Network availability

Overload probability

Why is it useful?

Early discovery of risks

Support of intentional overprovisioning

Evaluation of potential upgrade strategies

New routing

More bandwidth, new links or nodes

New customers or SLAs

Motivation


Key ideas

Key Ideas

  • Network elements can fail

    • Failure probability

    • Independent failures

    • Correlated failures modelled by virtual element

  • Traffic matrices can vary

    • Example: additional interdomain traffic, hot spots

    • Traffic matrix probability

    • Independent of network failures

  • Definition: scenario = set of network failures and traffic matrix

    • Scenarios determine unavailability / overload

    • Derive scenario probability

    • Take all scenarios for the analysis with probability larger than pmin

    • Definition: set of considered scenarios S


Calculation of network un availability

Calculation of Network (Un)Availability

  • Problem: multiple failures can compromise connectivity

  • Loss of connectivity for e2e aggregate between node v and w in special scenario s?

    • Disconnected(v,w,s)  {0, 1}

    • Analysis of routing in scenario s

  • Conditional probability for loss of connectivity

    • Estimate for unavailability: not all possible scenarios respected in S

    • Upper and lower bounds available


European nobel test network

European Nobel Test Network


Network unavailability for madrid s aggregates

Network Unavailability for Madrid‘s Aggregates

of Madrid‘s Aggregates


Average network unavailability for routers

Average Network Unavailability for Routers


Network unavailability for overall traffic

Network Unavailability for Overall Traffic

C


Calculation of link overload

Calculation of „Link Overload“

  • Problem: redirected and extra traffic leads to overload

  • Link utilization ρ(l,s) of link l in special scenario s?

    • Analysis of routing and traffic matrix in special scenario s

  • Probability to have utilization U(l) larger than x on link l

    • Complementary cumulative distribution function (CCDF)

    • Calculate ρ(l,s) for all considered scenarios sS

    • Sum all probabilities p(s) of scenario with ρ(l,s)>x

  • Comments

    • Intelligent data structures and efficient algorithms required

    • Only estimate, but upper and lower bounds available


Impact of probability limit p max for failure scenarios

pmin=10-8

Impact of Probability Limit pmax for Failure Scenarios

pmin=10-6


Which link is most at risk

Which Link is Most at Risk?


Link rankings

Link Rankings

  • Utilization threshold uc

  • Utilization percentile q

  • Appropriate weighted integral based on utilization distribution


Graphical presentation

Graphical Presentation


Summary conclusion

Summary & Conclusion

  • Tool for assessment of network resilience

    • Network availability

    • „Overload“ probability

    • Useful for planning and operation of networks

  • Achievements

    • Fast algorithms (Java)

    • Visualization of

      • Unavailabilty

      • „Overload“

  • Outlook: interdomain resilience


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