a flexible overlay network simulation framework

Institute of Telematics

OverSimA Flexible Overlay Network Simulation

Framework

Ingmar Baumgart, Bernhard Heep, Stephan Krause

IEEE Global Internet Symposium 2007, Anchorage, AK, USA

OverSim, GI07, Anchorage, AK, USAStephan Krause Institute of TelematicsUniversität Karlsruhe (TH) www.tm.uka.de

1

Requirements

OverlayFlexibility Scalability

UnderlayHeterogeneityTerminal MobilityBackbone simulation


2

Additional Requirements

InteroperabilityPlanetLabexperimentsNetwork emulation

Debugging and Overlay visualization


3

State of the Art

No established standard overlay simulatorMost promising: P2PSim, OverlayWeaver and PlanetSimP2PSim (http://pdos.csail.mit.edu/p2psim/)☺ Many implemented overlay protocols

No real world interconnection, no visualizationOverlayWeaver (http://overlayweaver.sourceforge.net/)☺ Real world interconnection

No simulation of underlying network, not scalablePlanetSim (http://planet.urv.es/planetsim/)☺ Flexible and scalable

Only very simplistic model of underlying network


4

Outline

How to implement all required features?Overlay layer: Flexibility, scalabilityUnderlay model: Heterogeneity, terminal mobility, backbone simulationInteroperability, network emulationDebugging and overlay visualization

Featured Overlays and Applications

Performance Evaluation and Validation


5

Flexibility

Modular architectureBased on OMNeT++

Layered architectureUnderlying networkOverlay layerApplication layer

Consistent interfacesbetween layers

UDP between network and overlayCommon API between overlay and applicationExchange of one component is transparent to all

other components

Application Layer

Common API Interface

Overlay Layer

UDP Interface

Underlying Network


6

Scalability

Tradeoff: Level of detail vs. simulation speedMaximum scalability SimpleUnderlayPackets are exchanged directly between nodes

Minimizes number of eventsSimple scenario: Constant delayFor more realistic delays:

Place nodes in Euclidian spaceDelay is proportional to distanceNo additional events needed Still scalable


7

Heterogeneity and Mobility

Extension of the synthetic coordinate modelNodes are assigned to an “access net” with specific bandwidth and delay characteristicsCalculated packet delay:

Mobility: Move node to new coordinate, change access net characteristics and IP address

A

p

bl

Ae dd += ddA

p

bl

Ae ++= 2|||| BAc −⋅A

p

bl

Ae dd ++=B

p

bl

Bd ++BAc −⋅ 2||||

A B


8

Backbone Simulation

For detailed simulation of the underlying network: INETUnderlayBased on INET framework for OMNeT++Simulates a complete IP backboneAccess routers attached to backbone routers

Simulates all effects of heterogeneous access networks

Bandwidth, Delay, Packet loss, Queuing effects

Mobility is simulated by moving a node from one access router to another


9

Interoperation

For PlanetLab experiments and interconnecting with real world implementations:Emulated nodes inreal networks Event scheduler runs at real timeLinux TUN device forexchanging packetswith a real networkExternal applications canbe connected to the simulation


10

Network Emulation

For demonstrational purposes:Real nodes in emulated networksEmulate overlay networkwith INETUnderlayAdd a gateway node

This router features a TUN interface

External devices can communicate with simulated overlay


11

Visualization and Debugging

Topologyvisualization

Messagevisualization

Node statedebugging


12

Overlay Protocols

Implemented overlay protocolsStructured: Chord, Pastry, Koorde, BrooseUnstructured: GIAGaming protocols/Multicast: VAST

Base class for structured overlays to facilitate implementation of new overlay protocols

Overlay message handling (RPC, statistics)Generic lookup functionBootstrapping supportOverlay topology visualization


13

OverSim Performance Evaluation

Compare simulation speed with P2PSimUnderlay model:

P2PSim and OverSim/SimpleUnderlay:Constant delay of 50 msec

OverSim/INETUnderlay:Randomly generated backbone (40 routers)

Number of nodes: 1,000, 10,000 and 100,000Simulated time period: 1,000 secondsOverlay: Chord

Stabilize interval: 20 secFix fingers interval: 120 secEach node sends a query every 10 sec


14

Performance Evaluation Results

OverSim is faster even with greater level of detail


15

Validation: Chord Results

Simulation results are comparable to P2PSim’s


16

Conclusion & Future Work

OverSim is a new, modular overlay simulatorFocus on scalability and flexibilityVarious underlay models for maximum speed, maximum precision or real network useMany implemented overlay protocolsEasily extendable

Future work:New overlay protocols and applications

Kademlia, Scribe, i3, P2PSIPImport models from topology generatorsImport datasets from internet latency measurements

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a flexible overlay network simulation framework

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