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Selfish DTN capacity Experimental estimation

Selfish DTN capacity Experimental estimation. Dagstuhl Seminar DTN II February 2009. Joint work of PU Tournoux, V. Conan, J. Crowcroft, J. Leguay, F. Benbadis, M De Amorim. DTN performance. Measured in terms of packet delivery ratio, packet delay for non-congested networks

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Selfish DTN capacity Experimental estimation

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  1. Selfish DTN capacityExperimental estimation Dagstuhl Seminar DTN II February 2009 Joint work ofPU Tournoux, V. Conan, J. Crowcroft, J. Leguay, F. Benbadis, M De Amorim

  2. DTN performance • Measured in terms of packet delivery ratio, packet delay for non-congested networks • Performance is limited by: • Storage constraints • Transmission constraints • Node selfishness

  3. The problem For a given traffic pattern, what is the maximum total demand that can be achieved before the network becomes saturated, either in link capacity or in storage capacity?

  4. Capacity estimation • Use traces of node contacts as input • Consider fixed demands • One demand = transfer x Kbits from node s to node d injected at time t • Traffic is routedat Wardrop equilibrium • Increase x for all demands • Stop when storage/transmission overload increasesfaster than load

  5. Wardrop equilibrium • The journey times (or costs) in all routes actually used are equal and less than those which would be experienced by a single vehicle (or message) on any unused route. • For additive and separable positive and continuous cost functions the Wardrop equilibrium is a convex minimization problem. The equilibrium is unique, and may be obtained by running the Frank-Wolfe algorithm

  6. Time Discretized Graph

  7. Transmission capacities of connections Example

  8. Weight on delay = 1Weight on transmission cost = 1 Fastest route • Delay is costly: the fastest route is chosen

  9. Weight on delay = 1Weight on transmission cost = 30 Costly transmissions • Increasing transmission cost forces usage of slower routes

  10. Weight on delay << 1Weight on transmission cost = 30 More delay • Allowing for more delay forces usage of even more slow routes

  11. Infocom data set Weight on delay • Capacity increases with delay tolerance 0.10.0001 1 0.5

  12. Conclusions • Delay-tolerance helps increase capacity. • Routing protocols should be multi-dimensional. • Selfishness makes network engineering challenging.

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