Transcript ns-3 tutorial - Tom Henderson

Network Simulation and Emulation
in a Testbed Era
Tom Henderson
University of Washington
The Boeing Company
UW EE Colloquium
February 24, 2009
UW EE Colloquium Feb. 2009
1
Boeing Research & Technology organization
Engineering, Operations & Technology | Boeing Research & Technology
Networked Systems Technology
Networked Systems Technology
Information
Assurance
• Development of high assurance
multi-level security technologies
– EAL7 common criteria
evaluation experience
– Formal methods in support
of EAL 7 evaluation
• High assurance guard solutions
for edge, core, & tactical
environments
• Security modeling & formal
method analysis of end to end
systems
• Policy-based secure computing
– Systems of Systems
IA approach
• Intrusion detection correlation
technologies
• Secure workflow and SOA
technologies
• Information operations
• System security engineering
• Advanced trusted system
implementations
• Text analysis for information
assurance
• Proprietary program support in IA
technologies
• Secure RFID infrastructure
• Anti-tampering technologies
Digital
Communications &
Network Technology
• Phased array antennas
• Free air laser
communications
• High capacity RF
communications
• Bandwidth efficient
modulation
• On board wireless
communications
• Network processors
• AFRL RAPID
• Integrated communications
systems
• MANET protocols
• Reliable routing
• Network management for
tactical environments
• Auto-configuration
• Network gateways
• End to end QoS
• Network security
• UAV network router
Home
organization
Copyright © 2009 Boeing. All rights reserved.
Information
Management and
Transformation
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Data & Text Mining
Human Language technologies
Decision support information
Information visualization
Machine translation
Knowledge representation
Data integration
Simulation visualization
3D visualization
Model-based collaboration
Social networks analysis
Intelligent graphics & docs.
Collab. human robot systems
Autonomous systems
– Architectures
– World modeling
– Multi-vehicle behaviors
Reasoning
Adaptive planning
Learning
Distributed multi-agents
Global information sharing
RFID info. mgmt. services
Adaptive intelligent info. integration
Semantic modeling, ontologies,
adaptive workflow modeling
Quality of Service info. algorithms
Wireless mobile dynamic info. mgmt.
Sensor networks
Data & information fusion
Info. assessment aids
Trends analysis/intent inferencing
Situation assessment
Resource allocation techniques
Deconfliction algorithms
Course of action analysis/generation
Applied
Mathematics
• Variation analysis & reduction
• Reliability & time dependent data
analysis
• Analysis of large datasets
• Financial modeling & decisions
• Survey & test design
• Statistical training
• Quality assurance & Lean+
• Design of Experiments
• Computer-aided geometric design
• Numerical optimization
• Design space exploration
• Multidisciplinary Design
Optimization
• Geometric modeling
• Multivariate data fitting
• Optimal control
• Engineering modeling & analysis
• Computational mechanics
• Sensor Fabric design & operation
• System dynamics & control
modeling
• Data structures for complex
product families
• Kalman filter applications
• Operations research
• Systems of Systems modeling &
analysis
• Discrete/network/stochastic/
Systems of Systems optimization
• Data fusion
• Discrete-event simulation
• Transportation, manufacturing,
business, communication &
military system modeling
Architecture and
Networked Systems
Technology
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
UML architecting
Arch. analysis
CONOPS development
System requirements
NR-KPP compliance
SoSE
Systems engineering
NCO demo.
LVC technologies
LVC tools
DIS router
Data link translation
Gateways
Networked manufacturing
Location services
Planning / visibility tools
Functional integration
High performance computing
GRID computing
Resource management
Functional integration
CINS lab
System/network mgmt.
QoS
Mobile agents
Situation awareness
Reconfigurable computing
S/W architecture
S/W processes
Arch. evaluation (ATAM)
Performance assessment
(PAPM)
• QoS
Contract Research
and Development
Programs
• Real-time system development
• Tactical info. mgmt. with an
emphasis in C2/tactical
collaboration
• Quality of Service network
utilization
• Software enabled control for
UAV automation
• Dynamic network management
• Affordable validation &
verification of flight critical
software & systems
• Collaborative anticipatory
systems
• Cyberwarfare / Cybercraft
• Effects-based operations
• System & vehicle health
management
• Diagnostics
• InfoCenter & information
management
• Database technology &
implementation
• Distributed sensor system
technology
What is a network simulator?
• A software tool and set of models used to
evaluate computer network behavior
• A discrete-event network simulator
describes networks in terms of a sequence
of discrete events
– The simulation kernel temporally orders and
dispatches events to models
– Models generate output or more events
– Time advances in discrete steps
UW EE Colloquium Feb. 2009
The basic model
Application
Application
Packet
Protocol
stack
Application
Application
Channel
Node
Protocol
stack
Node
NetDevice
NetDevice
NetDevice
Simul
UW EE Colloquium Feb. 2009
4
The basic model
// Define your topology
Node n0 = new Node;
Node n1 = new Node;
AddInternetStack (n0, n1);
Channel c0 = new Channel;.
Connect (n0, n1, c0);
Application a0 = new TrafficGenerator;
// Configure things
a0.SetDataRate (1Mb/s);
a0.Start (10.0 seconds);
// Define outputs
WriteTraceFile (“outfile”);
// Run the simulator
Simulator::Run();
UW EE Colloquium Feb. 2009
Network simulation remains popular
• Many commercial products
– e.g. OPNET, QualNet, Shunra VE, Matlab Simulink,
OMNet++, NCTUns, SSFNet, Extend
• A few free, open source projects
– ns-2 is the most widely used such tool
– roughly 10,000 downloads/month
• Widely used in research
Source: Search of ACM Digital Library papers citing simulation, 2001-04
UW EE Colloquium Feb. 2009
6
Skepticism in the research community
“For years, the community had to rely on
simulators, which now seem a little dated,
and it’s not clear who was convinced to
adopt anything new based on ns2
simulations;”
Nick McKeown, VINI public review, ACM Sigcomm 2006
UW EE Colloquium Feb. 2009
7
What has changed?
• Simulators have historically been used for
experiments in place of real machines
– A tradeoff of realism for scale
But now...
• Cost of test hardware has plummeted
• Virtualization technologies proliferate
UW EE Colloquium Feb. 2009
Emulab (University of Utah)
• Source: http://www.emulab.net
UW EE Colloquium Feb. 2009
Emulab
• Original Emulab allowed experiments of roughly
~100 nodes
– FreeBSD Dummynet and VLANs to interconnect the
nodes
• Emulab now offers virtualization
– Experiments of up to ~2000 (virtual) nodes
– Requires new approaches for experimental
configuration
• Also, some 802.11 wireless nodes
Source: M. Hibler et al., “Large-scale Virtualization in the Emulab
Network Testbed,” Proc. 2008 Usenix Technical Conference.
UW EE Colloquium Feb. 2009
PlanetLab: Global-scale Internet testbed
PlanetLab “slices”
• Source: http://www.planet-lab.org
UW EE Colloquium Feb. 2009
PL-VINI and Trellis
• PL-VINI adds virtual networking
capabilities (via network overlay) to
PlanetLab
– A. Bavier et al, “In VINI Veritas: Realistic and
Controlled Network Experimentation,” Proc. ACM
Sigcomm, 2006
• Trellis is a kernel-based implementation of
the same concept
– S. Bhatia et al, “Trellis: A Platform for Building
Flexible, Fast Virtual Networks on Commodity
Hardware,” ROADS Workshop, Dec. 2008
UW EE Colloquium Feb. 2009
ORBIT (Rutgers WINLAB)
• 802.11a/b/g radios
• Bluetooth
• GNU/USRP radios
• Noise generators
• Source: http://www.winlab.rutgers.edu/docs/focus/ORBIT.html
UW EE Colloquium Feb. 2009
Simulation “out of the loop”
• Source: NSF GENI project:
http://www.geni.net/docs/GENIOvrvw092908.pdf
UW EE Colloquium Feb. 2009
14
Skepticism in the research community
“For years, the community had to rely on
simulators, which now seem a little dated,
and it’s not clear who was convinced to
adopt anything new based on ns2
simulations;”
Nick McKeown, VINI public review, ACM Sigcomm 2006
UW EE Colloquium Feb. 2009
15
Overheard* on e2e-interest mailing list
“...Tragedy of the Commons...”
“...around 50% of the papers appeared to be...
bogus...”
“Who has ever validated NS2 code?”
“To be honest, I'm still not sure whether I will use a
simulation in a paper.”
“...I will have a hard time accepting or advocating
the use of NS-2 or any other simulation tool”
...
* September 2005 archives of the e2e-interest mailing list
UW EE Colloquium Feb. 2009
16
Questions
• Do we need to simulate networks anymore?
• What kind of network simulator is needed?
• Why should you believe network simulation
results?
UW EE Colloquium Feb. 2009
Why simulate?
Simulation is often an appropriate tool for the job
• Wireless
– Reproducibility
– Fidelity (especially, real-time constraints)
– Radios may not exist or be available
– Field tests in realistic conditions cost $$
• Scalability
– 10,000+ nodes?
– For smaller configurations, execution time
UW EE Colloquium Feb. 2009
Challenges for ns (and simulators)
• Align with how research is now conducted
• Improve credibility
Can a new simulator help with these problems?
UW EE Colloquium Feb. 2009
19
What is ns-3?
An open source project building a new network simulator to
replace ns-2
UW EE Colloquium Feb. 2009
20
ns-3 project goal
Develop a preferred, open simulation
environment for networking research
1) a tool aligned with the simulation needs of
modern networking research
2) an open-source project that encourages
community contribution, peer review, and
validation of the software
UW EE Colloquium Feb. 2009
21
Relationship to ns-2
ns-3 is a new simulator, without backward compatibility
Similarities to ns-2:
• C++ software core
• GNU GPLv2 licensing
• ported ns-2 models: random variables, error models,
OLSR, Calendar Queue scheduler, (more planned)
Differences:
• Python scripting (or C++ programs) replaces OTcl
• most of the core rewritten
• also based on the yans and GTNetS simulators
• new animators, configuration tools, etc. are in work
UW EE Colloquium Feb. 2009
22
Funding support
ns-3 project is supported by:
• NSF CISE CRI awards (2006-10)
– PIs: Tom Henderson and Sumit Roy (University of Washington),
George Riley (Georgia Institute of Technology)
– NSF CNS-0551686 (University of Washington)
‘
• INRIA Planete and the French government
With additional support from:
• 2008 Google Summer of Code
• University of Washington
• Georgia Institute of Technology
UW EE Colloquium Feb. 2009
23
Challenges for ns (and simulators)
• Align with how research is now conducted
• Improve credibility
UW EE Colloquium Feb. 2009
24
Test and Evaluation Options
• When mathematical analysis alone won’t do
Test and evaluation options
Pure
Simulation Virtual/Physical
Field
simulation cradles
testbeds
experiments
Live
networks
Increasing realism
Increasing complexity
Can we develop tools to span this space?
UW EE Colloquium Feb. 2009
Some ns-3 design goals
1.
2.
3.
4.
Realism
Software reuse
Emulation
Composition
UW EE Colloquium Feb. 2009
1) Attention to realism
Research should often involve a mix of simulations
and testbed or live experiments
• If the simulator cannot be made to closely model
a real system:
– hard to compare results or validate the model
– hard to reuse software between the two domains
When in doubt, do what implementations do
UW EE Colloquium Feb. 2009
27
Attention to realism (example)
An ns-3 Node is a husk of a computer to which
applications, stacks, and NICs are added
Application
Application
Application
“DTN”
UW EE Colloquium Feb. 2009
28
Realism (cont.)
• Align ns-3 to be more faithful
representation of real computers
– sockets API
– packets are “packed” binary representations
ready for direct serialization to/from network
devices
– alignment with Linux architecture
– multiple interfaces handled properly
UW EE Colloquium Feb. 2009
29
ns-3 follows a Linux architecture
• Linux corollaries
class
Ipv4Protocol
– each NetDevice is modelled
like struct net_device
– each layer-3 protocol has a
struct in_device
component for each
NetDevice
class
NetDevice
– this interface (transmit side)
is aligned with Linux
dev_queue_xmit()
– on receive side, demux is
modelled after Linux protocol
handlers
UW EE Colloquium Feb. 2009
30
2) software integration
Do not reimplement models and tools for which
open-source implementations abound
• ns-3 conforms to standard input/output formats
so that other tools can be reused.
– e.g., pcap trace output, ns-2 mobility scripts
• ns-3 is adding support for running
implementation code
– Network Simulation Cradle integration has met with
success: Linux TCP code
– ns-3 “process” API
UW EE Colloquium Feb. 2009
31
ns-3 simulation cradle
• Port by Florian Westphal of Sam Jansen’s Ph.D. work
Figure reference: S. Jansen, Performance, validation and testing with the Network
Simulation Cradle. MASCOTS 2006.
UW EE Colloquium Feb. 2009
ns-3 simulation cradle
For ns-3:
• Linux 2.6.18
• Linux 2.6.26
• Linux 2.6.28
Others:
• FreeBSD 5
• lwip 1.3
• OpenBSD 3
Other simulators:
• ns-2
• OmNET++
Figure reference: S. Jansen, Performance, validation and testing with the Network
Simulation Cradle. MASCOTS 2006.
UW EE Colloquium Feb. 2009
ns-3 “processes” and Posix API
Support for a synchronous Posix socket API
• each Posix type and function is redefined in the simulator
• processes get their own private stack
– somewhat like a lightweight virtual machine
• Benefits:
– makes porting real world application code much easier
– makes writing applications easier because the BSD socket API is
faithfully followed
• see the “mathieu/ns-3-simu” code repository
UW EE Colloquium Feb. 2009
34
3) emulation support
Support moving between simulation and testbeds or live
systems
• A real-time scheduler, and support for two modes of
emulation
UW EE Colloquium Feb. 2009
35
ns-3 emulation modes
real machine
virtual
machine
ns-3
virtual
machine
ns-3
ns-3
real
machine
real
machine
Testbed
1) ns-3 interconnects real or virtual
machines
2) testbeds interconnect ns-3
stacks
Various hybrids of the above are possible
UW EE Colloquium Feb. 2009
36
Example: ORBIT and ns-3
• Support for use of Rutgers WINLAB
ORBIT radio grid
UW EE Colloquium Feb. 2009
37
4) Composition
Define ns-3 with
interfaces to support
integration with other
tools
• Topology generators
• Traffic generators
• Data analysis frameworks
• Configuration tools
• Animators
ns-3 is a component of an overall workflow
UW EE Colloquium Feb. 2009
Common Open Research Emulator
Engineering, Operations & Technology | Boeing Research & Technology
Scalable Network Emulator
• Network lab “in a box”
• Efficient and scalable
• Easy-to-use GUI canvas
• Kernel-level networking efficiency
• Reference passing packet sending
• Runs real binary code
• No need to modify applications
• Connects with real networks
• Hardware-in-the-loop
• Distributed - runs on multiple servers
• Virtual nodes process real packets
• Fork of the IMUNES project
• University of Zagreb
• Open Source
• http://cs.itd.nrl.navy.mil/work/core
Copyright © 2009 Boeing. All rights reserved.
Networked Systems Technology
Overview of CORE Components
Engineering, Operations & Technology | Boeing Research & Technology
Networked Systems Technology
3. graphical user interface
Three key components
1. virtual machines
virtual images
(vimages)
Tcl/Tk GUI
core_span
core_wlan
tunnels
CORE
API
userspace
FreeBSD
kernel
netgraph
system
ng_wlan
NIC
2. networking subsystem
Copyright © 2009 Boeing. All rights reserved.
CORE features
Engineering, Operations & Technology | Boeing Research & Technology
Networked Systems Technology
IMUNES base:
• Flexible GUI-based management of FreeBSD lightweight
virtual containers
• Virtual topology can be hooked to real devices
CORE extensions:
• GUI enhancements, kernel enhancements, wireless
networking, Linux support (OpenVz and NetEm),
distributed emulation, and packaging.
• Software leads: Jeff Ahrenholz and Claudiu Danilov,
Boeing
• http://cs.itd.nrl.navy.mil/work/core
Copyright © 2009 Boeing. All rights reserved.
CORE and ns-3 integration
Engineering, Operations & Technology | Boeing Research & Technology
Networked Systems Technology
ns-3 tap-wifi-dumbbell.cc program
Copyright © 2009 Boeing. All rights reserved.
ns-3 and research alignment
In summary, make it easier to move from
simulation to emulation to experiments
• Realism and alignment with popular interfaces
• Support use of real code
• Emulation capabilities
• Combine ns-3 with other tools
UW EE Colloquium Feb. 2009
43
Challenges for ns (and simulators)
• Align with how research is now conducted
• Improve credibility
UW EE Colloquium Feb. 2009
44
Background on simulation credibility
[1] “Why We STILL Don’t Know How to Simulate Networks”
– Mostafa Ammar, Georgia Institute of Technology, Annual
Simulation Symposium 2005
[2] “Maintaining a Critical Attitude Towards Simulation
Results”
– Sally Floyd, WNS2 Workshop Keynote, October 2006
[3] “MANET Simulation Studies: The Incredibles”
– Kurkowski, Camp, and Colagrosso, ACM Sigmobile, MC2R,
Volume 9, Issue 4, October 2005
[4] “An Integrated Approach to Evaluating Simulation
Credibility”
– Muessig, Laack, and Wrobleski, U.S. Naval Air Warfare Center,
August 2001
UW EE Colloquium Feb. 2009
45
Criteria for Credibility
•
•
•
•
•
•
•
•
Repeatable
Unbiased
from [3]
Realistic Scenarios
Statistically Sound
Model Accuracy
Results Accuracy (Validation)
from [4]
Data Accuracy
Usability
UW EE Colloquium Feb. 2009
46
Repeatability
A hallmark of the scientific method...
• Papers should identify simulator, version,
operating system, parameters, etc.
• Better yet, make code and configuration
scripts available to the community
– Yet, 0 out of 84 ACM Mobihoc MANET
simulation papers (2000-2004) referenced
publicly available code (from [3])
UW EE Colloquium Feb. 2009
47
ns-3 approach
• We are adding support to systematically
document how simulations were
conducted
– A configuration subsystem that dumps
simulation parameters to a configuration file
(input and output)
• We will host code, publications, validation
results, etc.
UW EE Colloquium Feb. 2009
Model accuracy
• “error-free-ness” of software and models
• ns-3 goals here:
– Support real code where possible
– Open source models
– Maintainers
UW EE Colloquium Feb. 2009
49
Open source models
• “Given enough eyeballs, all bugs are shallow”
– Eric Raymond, “The Cathedral and the Bazaar”
• ns-3 needs ways to certify models, too
– capture level of community acceptance
– publication lists, cross-reference
– need to identify maintainers, or state the
absence of a maintainer
– validation techniques and results
UW EE Colloquium Feb. 2009
50
Example: ns-3 Wifi development
Several research groups are maturing the original INRIA model:
• Karlsruhe Institute of Technology: 802.11 PHY, 802.11e
– Equalizing PHY models including capture effects, user-definable coding
rates (e.g. 5.9 GHz from 802.11p), EDCA QoS extensions of 802.11e,
Nakagami/Rayleigh propagation loss model
• University of Florence: 802.11n features
– Frame Aggregation, Block ACK, HCF (EDCA and support for
HCCA),TXOP, HT terminal (also with protection modes), MIMO
• Russian Academy of Sciences: 802.11s
– a complete model of IEEE802.11s D2.0 Draft Standard
• Deutsche Telekom Laboratories in Berlin: 802.11 PHY
• Boeing: 802.11b channel models, validation
• (and others...)
UW EE Colloquium Feb. 2009
Pledge break
• ns-3 needs participation from the research
community
1) improving simulation credibility
2) contributed and supported models
3) maintainers
Please support your open source projects!
UW EE Colloquium Feb. 2009
Summary of simulation credibility
• Learn from good and bad examples of
simulation research, to produce credible
simulations
• Consider open source (or publishing of
models and scripts) to be integral part of
your research
• Please give back to the simulators that you
use
UW EE Colloquium Feb. 2009
53
Acknowledgments
Thanks to:
• the core development team and research project leads
– Raj Bhattacharjea, Gustavo Carneiro, Walid Dabbous, Craig
Dowell, Joe Kopena, Mathieu Lacage (software lead), George
Riley, Sumit Roy
• 2008 Google Summer of Code mentors and students
• many code authors and testers
• the ns-2 PIs and developers for creating ns-2 and for
supporting ns-3 activities
• USC ISI for hosting project mailing lists
Contact: [email protected] (office M354)
UW EE Colloquium Feb. 2009
54