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A ns2-based simulation framework for performance evaluation of overlay networks Michele Amoretti Mauro Andreolini Francesco Zanichelli Riccardo Lancellotti Universit di Parma Universit di Modena e Reggio Emilia FIRB Web-Minds, Genova

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FIRB Web-Minds, Genova 27-28 Ottobre 2006 1

A ns2-based simulation framework for performance evaluation of overlay networks

Mauro Andreolini Riccardo Lancellotti Università di Modena e Reggio Emilia Michele Amoretti Francesco Zanichelli Università di Parma

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Peer-to-peer systems

Increasing number of P2P-based

applications

– Streaming – Filesystems – ...

Need for tools to evaluate performance of
verlay networks and routing algorithms

– Prototypes → too many nodes required – Analytical models → may be too complex – Simulation

Need for simulators of overlay networks

– Already validated models and tools

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ns-2 Network simulator

Standard “de facto” in network simulation

– Widely adopted in scientific community

Little support for overlay (P2P) networks

– Some P2P feature in code for ad-hoc networks

(specific for message routing in wireless links)

– Gnutella sim

(support only for Gnutella v0.4, requires patches and is not maintained) Need of ns-2 extensions for overlay networks

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Proposal

Simulation framework for overlay networks

– Based on widely-accepted ns-2 simulator – Focus on performance evaluation

Elements of the framework

– Overlay routing algorithms (C++ classes) – Topology generators (TCL scripts) – Data analysis tools

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Overlay routing algorithms

Flexible base class

hierarchy

Object-oriented design:

key classes

– Support classes – Transport-level data – Logging facility – P2P routing

Easy to extend

– New algorithm

→ New class (+ TCL binding)

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Available algorithms

Unstructured networks

– Flood-based – Probabilistic flood – Random Walker

Semi-structured networks

– Support for supernodes – JXTA

– Pastry

Novel algorithms

– Halo – Fuzzy-DHT

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Logging facility

Separate logfile for P2P network operations
Reports routing events:

– Hits – Miss – Query drop

For each event logs additional information

such as:

– Simulation time of the event – Query TTL – Query key – Additional information (algorithm-supplied)

Log file easy to parse (regexp-friendly)

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TCL scripts

Library of TCL scripts for the simulation

– Definition of Physical topology – Construction of overlay network

Logging of generated topologies

– Population of overlay network (resources) – Setup of log files – Generation of queries

Multiple available functions for each phase
TCL support for algorithms parameters
TCL support for command-line options

– Sensitivity analysis can be carried out without

changing C++ and TCL code

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Physical network topologies

Star topology
Real Network model

(UniPR)

Hierarchical topologies

(Brite generated)

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Overlay network topologies

Neighborhood

relationships

Available topologies

– Poisson networks – Scale Free networks – Seeded networks – Locally preferential

networks

– JXTA growth

(JXTANetMap)

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TCL support for resources and queries

Trace-driven simulation

– Repeatable simulation – Support for multiple RNG seeds

Traces for resources

– Distribution of resources over nodes

Traces for queries

– Sequence of keys to search in the network – Support for “wildcard searches” – Queries can have different “selectivity” σ – Allows to evaluate overlay routing algorithms

performance as a function of σ

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Data collection and analysis tools

Automated analysis of logfile

– Perl-based log parser – P2P logs – Standard ns-2 logs – Topology logs

Automatic statistic extraction

– Histograms – Cumulative distribution

Automatic plotting

– Template gnuplot files

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Available analyses

Hit rate (# of hits/theoretical max)

– Exact searches – Wildcard-based searches

TTL of hits
Time of hits
Overhead (# of pkts per query)
Topology of overlay network

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Experimental testbed

CASPUR Cluster

– 40 Nodes, dual AMD 64 CPU, 8GB RAM,

SUSE Linux

– OpenPBS batch scheduler

WebLAB Cluster

– 20 Nodes, Intel Xeon CPU, 1GB RAM, Debian

Linux

UniPR Cluster

– 7 Nodes, Intel Pentium IV, 1GB RAM,

Ubuntu Linux

Simulator compiles and runs correctly in

every environment (including 64 bit)

Simulation of up to 4000 Nodes

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Publications

M. Andreolini, R. Lancellotti P. S. Yu, “A flexible and

efficient lookup algorithm for Peer-to-Peer systems”, Submitted for publication, 2006

M. Amoretti, F. Zanichelli, G. Conte, “Performance

evaluation of advanced routing algorithms for unstructured Peer-to-peer Networks”, ValueTools 2006

M. Amoretti “Peer-to-peer based Grid architectures”

Ph.D. thesis, 2006

M. Andreolini, R. Lancellotti P. S. Yu, “Analysis of peer-

to-peer systems: workload characterization and effects

n traffic cacheability” MASCOTS 2004

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