IRTF P2PRG A. Brown
Internet Draft Stirling
Expires: July 26, 2006 M. Kolberg
Stirling
January 27, 2006
Tools for Peer-to-Peer Network Simulation
draft-irtf-p2prg-core-simulators-00.txt
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Abstract
Due to the extremely large scale of P2P overlay networks, complexity
has become a major issue. With the number of connected nodes reaching
into the millions, a platform which can accurately simulate an
overlay network is important. Many freely available network
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simulators exist, ranging from modelling networks at the packet level
to concentrating purely on the overlay network. The following
document provides an overview of these simulators, documenting the
maximum number of simulated nodes achieved in experiments, the P2P
overlay architectures modelled and the chosen implementation
language.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [1].
Table of Contents
1. Introduction...................................................2
2. Overlay Network Simulators.....................................3
2.1. Narses....................................................3
2.2. 3LS.......................................................4
2.3. NeuroGrid.................................................4
2.4. PeerSim...................................................5
2.5. P2PSim....................................................5
3. Packet level Network Simulators................................6
3.1. Omnet++...................................................6
3.2. NS2.......................................................6
3.3. SSFNet....................................................7
4. Summary........................................................8
5. Security Considerations........................................9
6. References....................................................10
6.1. Normative References.....................................10
6.2. Informative References...................................10
Author's Addresses...............................................11
Intellectual Property Statement..................................11
Disclaimer of Validity...........................................12
Copyright Statement..............................................12
Acknowledgment...................................................12
1. Introduction
To support the performance work of service overlays to be undertaken
by the P2PRG CORE subgroup, we are examining existing simulation
tools for suitability. This document summarizes information we have
collected to date, covering only freely available simulation tools.
Simulating Peer-to-Peer (P2P) overlay networks is a common problem
for researchers/developers. Firstly, P2P overlay networks need to be
scalable (Kazaa has more than 4 million simultaneous users) and
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creating a simulation for such a large network is difficult due to
memory constraints using even the most powerful machines. However,
some tools allow a simulation to be distributed over a set of
machines.
Additionally, it may be desirable that a simulation behaves in
accordance to a physical network (packet delay, traffic and network
congestion, bandwidth limitations etc). These considerations also
increase the overhead on the host machine. Subsequently, when
choosing a network simulation tool for a given network, a distinction
must be made between simulation tools which are suitable for low
level networks and those which are suitable for P2P overlay networks.
In respect to this decision, this document is split into two further
sections. The first section describes simulation tools which are
suitable for overlay networks, boasting scalability and small memory
footprints. The second section describes some of the heavier network
simulators, which boast an array of Internet models and are deemed
more suitable for lower level network simulation.
2. Overlay Network Simulators
2.1. Narses
The Narses simulator is a flow-based network simulator designed to
avoid the overhead of packet level simulators [2] [3]. Narses is
written in Java and achieves high levels of scalability by simulating
aggregate flows rather than individual packets. By simulating a chunk
of bytes and not individual packets, Narses reduces the number of
events and subsequently the amount of memory used in the simulation.
To further reduce memory requirements, Narses assumes that transfers
between two end users are limited to the bandwidth allocated on the
first link to the network. This ensures there is no need for
intermediate routers and reassessment of link bandwidth, hence
further reducing the number of events in the simulation.
By taking such measures, Narses trades detail of the underlying
network for decreased runtimes and a lower memory footprint. Of the
models of Narses, the largest is the bandwidth-share model. This TCP
like model tries to replicate the sharing of link bandwidth between
independent flows. This model was tested in a network consisting of
600 nodes transmitting 200KB flows of data. Narses was reported to be
45 times faster and consumed 28% of the memory of NS2. There is no
evidence of existing simulations of overlay networks for Narses.
Download Simulator: http://sourceforge.net/projects/narses/
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2.2. 3LS
3LS (3-Level-Simulator) is a Java based simulator for overlay
networks that uses a central step clock [3]. The system is separated
into three models:
1. Networked
2. Protocol
3. User
The network model is described in terms of distance between nodes in
a 2D space. The protocol model is simply the P2P protocol being used.
The user model generates input from users using a GUI or file.
Communication can only be achieved between directly connected layers.
When running the simulator it is possible to either create the models
for each of the three described levels or to select existing models
from a library. As the simulation runs, each event is displayed on
the screen. Once completed, the simulation data is stored to a file
and this data is accessed by a visualisation tool named AiSee [15].
Currently, an implementation of Gnutella 0.4 exists and has been
tested on a small network of fewer than 20 nodes.
Download Simulator: Please e-mail the creators Nyik San Ting and
Ralph Deters (nyt431@mail.usask.ca, deters@cs.usask.ca) at the
University of Saskatchewan for a copy.
Documentation: [3]
2.3. NeuroGrid
NeuroGrid [5][6] is a Java based network simulator designed for
comparisons between file sharing P2P systems such as Gnutella,
Freenet and other NeuroGrid systems. The NeuroGrid simulator is a
single-threaded event simulator and uses a configuration file to
define the protocol to simulate and the network properties. These
properties include the number of nodes and queries to execute.
Statistics including the number of successful queries and messages
parsed can be saved into files for later analysis. Currently there
are simulations available for Gnutella, NeuroGrid, Freenet and
Pastry.
NeruoGrid has been used to simulate networks up to 300,000 nodes on a
machine with 4GB of RAM.
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Download Simulator: http://sourceforge.net/projects/neurogrid/
Documentation: http://neurogrid.net/php/simulation.php
2.4. PeerSim
PeerSim [7] is written in Java and offers an array of predefined * protocols for P2P simulation. These include:
. OverStat: A collection of aggregation protocols. Aggregation is a
collective term for a set of functions aimed at providing
statistical information over distributed systems, such as the
average load of the nodes or the size of the network.
. SG-1: A protocol for self-organizing and maintaining a superpeer
based topology.
. T-Man: This protocol can be used to build a wide range of
different topologies using only a ranking function that defines the
preference of each node for neighbours.
PeerSim is composed of two simulation engines, one is cycle-based and
the other is event driven. This allows it to be both dynamic and
scalable. The engines consist of components which may be 'plugged in'
and use a simple ASCII file based configuration mechanism which helps
reduce the overhead. The cycle-based engine does not model the
transport layer and subsequently is more scalable. The event-based
engine is less efficient but more realistic. PeerSim can achieve a
network consisting of 10^6 nodes using the cycle-based engine.
Download Simulator: http://sourceforge.net/projects/peersim/
Documentation: http://peersim.sourceforge.net/#docs,
http://peersim.sourceforge.net/tutorial1/tutorial1.html
2.5. P2PSim
P2PSim [10] is a written in C++ and designed for the evaluation of
P2P protocols. This multi-threaded, discrete event simulator runs in
several UNIX-like operating systems. P2PSim already supports Chord,
Accordion, Koorde, Kelips, Tapestry, and Kademlia. These
implementations are specific to P2PSim and do not model all features
* Description of P2P protocols taken from [7]
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of the protocols. P2PSim has been tested with up to 3000 nodes using
the Chord implementation.
Download Simulator: http://pdos.csail.mit.edu/p2psim/
3. Packet level Network Simulators
3.1. Omnet++
OMNeT++ [8] is an open-source, component-based simulation environment
with a strong focus on supporting the user with a Graphical User
Interface (GUI). Although Omnet++ is not strictly a network
simulator, it is gaining popularity in that domain. Components
(modules) are programmed in C++ and assembled into larger components
using a high level language (NED). It is primarily used for
simulating communication networks, but can additionally be used for
protocol modelling and modelling queuing networks and
multiprocessors. Available models include but are not limited to IP,
TCP, UDP, PPP, Ethernet, MPLS with LDP and RSVP-TE signalling and
802.11. Currently there exists a P2P swarming simulation for Omnet++
[16], which has been tested on a network of up to 1000 nodes. The
overhead of modelling the transport layer in this simulation
environment will likely hinder scalability. However, Omnet++ can also
run distributed simulations over a number of machines.
Download simulator: http://www.omnetpp.org/filemgmt/
Documentation: http://community.omnest.com/doc/tictoc-tutorial/
http://www.omnetpp.org/doc/manual/usman.html,
http://www.omnetpp.org/doc/api/index.html
3.2. NS2
NS2 [9], developed at UC Berkeley, is a discrete event simulator
targeted at networking research and provides substantial support for
simulation of many Internet, routing, and multicast protocols. It can
be installed on both Windows (using Cygwin) and Linux but evidently
is more suited to Linux. NS2 is comprised of many various packages to
provide its features (e.g. compatibility with numerous protocols and
providing graphical representation of simulations etc) thus is
notoriously difficult to use.
NS2 implements a vast array of protocols including TCP and UDP,
traffic source behavior such as FTP, Telnet, VBR and CBR.
Additionally, there is router queue management mechanisms such as
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Drop Tail, RED and CBQ implemented. NS2 also implements multicasting
and some of the MAC layer protocols for LAN simulations. Currently,
there is only one P2P simulation available for NS2 (Gnutella).
Simulations in NS2 are constructed using a mixture of C++ and OTcl
(Object Orientated version of Tcl created by MIT).
Simulating in NS2 is a four step model.
1. Firstly, add a combination of C++ and OTcl code to the NS2 standard
set of libraries to implement your protocol.
2. Create the simulated network using an OTcl script (define the
nodes, links etc).
3. Run the generated scripts.
4. Analyze the trace files generated by NS2. A graphical model (NAM)
can use the trace files to show a graphical representation of the
simulation. Other tools available include graph plotting.
Due to the realistic nature of the packet level NS2 simulator,
scalability is a major issue. However, like most packet level
simulators NS2 can run in parallel with a number of other machines.
This can increase the maximum number of nodes for a given simulation
but can become difficult to manage. Subsequently, NS2 is commonly
used for simulating small networks and is generally unsuitable for
modelling overlay networks.
Download Simulator: http://www.isi.edu/nsnam/ns/ns-build.html
Documentation: http://www.isi.edu/nsnam/ns/, http://nile.wpi.edu/NS/,
http://www.isi.edu/nsnam/ns/ns-tutorial/index.html
3.3. SSFNet
SSFNet [11] is a collection of Java and C++ based components and uses
the Domain Modelling Language (DML) to configure networks as a series
of configuration files. The principal classes in the SSF.OS Framework
(for modelling of the host and OS components) and the SSF.Net
Framework (for modelling the network connectivity) can be used to
construct virtually any Internet model. The frameworks SSF.OS and
SSF.Net hide all details of the discrete event simulator SSF API,
which allows implementation of the protocols similar to a real
operating system. This was the chosen simulator for Epichord [14].
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SSFNet simulations can be executed independently or in parallel with
other simulations running on Linux, Windows or SUN Solaris alike.
Regarding maximum network size, a network of 33,000 nodes is
achievable (on a powerful machine with 2GB of RAM). SSFNet also has
the ability to run a distributed simulation.
Download Simulator: http://www.ssfnet.org/ssfImplementations.html
Documentation: http://www.ssfnet.org/internetPage.html,
http://www.ssfnet.org/SSFdocs/ssfapiManual.pdf
4. Summary
The following tables summarizes the tools.
SIMULATOR P2P PROTOCOLS MAX NODES DISTRIBUTED
SIMULATION
Narses None 600 No
3LS Gnutella < 1,000 No
NeuroGrid Gnutella, NeuroGrid, 300,000 No
Pastry, FreeNet
PeerSim Collection of > 10^6 No
internally developed
P2P models
P2PSim Chord, Accordion, 3,000 No
Koorde, Kelips,
Tapestry, Kademlia.
Omnet++ None 1,000* Yes
NS2 Gnutella N/A Yes
SSFNet None 33,000 Yes
Table 1. Simulator Characteristics
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Max Nodes is the reported maximum based on information from the
simulation developers, and refers to number of simulated nodes per
host. This number may be hardware dependent. See the website for the
tool for more details.
P2P Protocols are those known to have modeled with the given tool and
are models available with the downloaded tool.
For Omnet++, this data was obtained from the P2P Swarming protocol
[15]. This does not mean more nodes cannot be achieved using Omnet++.
The following table shows the implementation language.
SIMULATOR LANGUAGE
Narses Java
3LS Java
NeuroGrid Java
PeerSim Java
P2PSim C++
Omnet++ C++/NED
NS2 C++/OTcl
SSFNet Java/C++/DML
Table 2. Implementation language(s) for each simulator
5. Security Considerations
There are no new security considerations in this document.
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6. References
6.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
6.2. Informative References
[2] TJ Guili and Mary Barker, Narses: A scalable flow based network
simulator, arXiv:cs.PF/0211024 v1 20 Nov 2002
[3] Narses Simulator, http://sourceforge.net/projects/narses/,
viewed January 23, 2006.
[4] Nyik San Ting, Ralph Deters, 3LS - A Peer-to-Peer Network
Simulator, Third International Conference on Peer-to-Peer
Computing (P2P 2003).
[5] NeuroGrid, http://www.neurogrid.net, viewed January 23rd, 2006
[6] Sam Joseph and T. Hoshiai. Decentralized meta-data strategies:
Effective peer-to-peer search. IEICE Transactions on
Communications, E86-B(6):1740-1753, 2003.
[7] PeerSim, http://peersim.sourceforge.net, viewed January 23,
2006.
[8] Omnet++, http://www.omnetpp.org, viewed January 23, 2006.
[9] Network Simulator 2, http://www.isi.edu/nsnam/ns/, viewed
January 23, 2006.
[10] P2PSim, http://pdos.csail.mit.edu/p2psim/, viewed January 23,
2006.
[11] Scalable Simulation Framework Net, http://www.ssfnet.org,
viewed January 23, 2006
[12] Kant, K., Iyer, R.: Modeling and simulation of ad-hoc/p2p file-
sharing networks. In proceedings of Tools 2003. (2003)
[13] Alberto Montresor, Gianni Di Caro, Poul E. Heegaard, BISON:
Architecture of the Simulation Environment, IST-2001-38923
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[14] B. Leong, B. Liskov and E. D. Demaine: EpiChord: Parallelizing
the Chord Lookup Algorithm with Reactive Routing State
Management, MIT Technical Report, Aug 2004.
[15] AbsInt. AiSee homepage. http://www.aisee.com/, viewed January
24th, 2006
[16] Omnet ++ P2P Swarming Protocol, http://me55enger.net/swarm/,
viewed January 24th, 2006.
Author's Addresses
Alan Brown
Department of Computing Science and Mathematics
University of Stirling
Stirling FK9 4LA
Scotland
Email: abr@cs.stir.ac.uk
Mario Kolberg
Room 4B60, Cottrell Building
Department of Computing Science and Mathematics
University of Stirling
Stirling FK9 4LA
Scotland
Email: mkolberg@ieee.org
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