1 / 32

TCP/IP Network Simulation

TCP/IP Network Simulation. Jahwan Koo Intelligent HCI Convergence Research Center Sungkyunkwan University jhkoo@songgang.skku.ac.kr. Talk Objectives. Appreciate the role of simulation in performance evaluation Understand the steps of simulation methodology Classify various simulation tools

tiva
Télécharger la présentation

TCP/IP Network Simulation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. TCP/IP Network Simulation Jahwan KooIntelligent HCI Convergence Research CenterSungkyunkwan Universityjhkoo@songgang.skku.ac.kr

  2. Talk Objectives • Appreciate the role of simulation in performance evaluation • Understand the steps of simulation methodology • Classify various simulation tools • Become familiar with popular simulation tools

  3. Research To study (something) thoroughly so as to present in a detailed, accurate manner Development Mathematical Experimental Simulation Methodology Basic Concepts Case Study How are you doing research?

  4. Simulation? • Robert.E Shannon, “Introduction to the art and science of simulation” • the process of designing a model of a real system and conducting experiments with this model for the purpose of understanding the behavior of the system and /or evaluating various strategies for the operation of the system • Advantages • Describe the behavior of a system • Use the model to predict future behavior, i.e. the effects that will be produced by changes in the system or in its method of operation

  5. Simulation Methodology

  6. Classification • General-purpose programming languages (GPPL) • “Plain” simulation languages (PSL) • Simulation packages (SP)

  7. Advantages & Disadvantages • GPPLs • Advantages • Available in almost all computer systems & platforms • Almost all researchers know at least one GPPL very well • Provide total control over the software development process • Disadvantages • Lack of support for a discrete-event simulation • Spend considerable time and effort writing routines for event handling & random number generation • Model constructions take a very long time • PSLs • Advantages • Basic support for a discrete-event simulation • Disadvantages • Not available in all computer systems & platforms • The need of programming expertise in a new language • Lack of built-in libraries for TCP/IP networks • SPs • Advantages • Highest level of simulation tools • Basic support for a discrete-event simulation • Built-in libraries for TCP/IP networks

  8. NS History • 1989: REAL network simulator • 1995: DARPA VINT project at LBL, Xerox PARC, UCB, and USC/ISI • Present: DARPA SAMAN project and NSF CONSER project • Collaboration with other researchers including CIRI

  9. NS Status • Periodical release (ns-2.1b9a, July 2002) • ~200K LOC in C++ and Otcl, • ~100 test suites and 100+ examples • 371 pages of ns manual • Daily snapshot (with auto-validation) • Stability validation • http://www.isi.edu/nsnam/ns/ns-tests.html • Platform support • FreeBSD, Linux, Solaris, Windows and Mac • User base • > 1k institutes (50 countries), >10k users • About 300 posts to ns-users@isi.edu every month

  10. NS Functionalities • Wired world • Routing DV, LS, PIM-SM • Transportation: TCP and UDP • Traffic sources:web, ftp, telnet, cbr, stochastic • Queuing disciplines:drop-tail, RED, FQ, SFQ, DRR • QoS: IntServ and Diffserv • Emulation • Wireless • Ad hoc routing and mobile IP • Directed diffusion, sensor-MAC • Tracing, visualization, various utilities

  11. NS Components • Ns, the simulator itself • Nam, the network animator • Visualize ns (or other) output • Nam editor: GUI interface to generate ns scripts • Pre-processing: • Traffic and topology generators • Post-processing: • Simple trace analysis, often in Awk, Perl, or Tcl

  12. NS Models • Traffic models and applications: • Web, FTP, telnet, constant-bit rate, real audio • Transport protocols: • unicast: TCP (Reno, Vegas, etc.), UDP • Multicast: SRM • Routing and queuing: • Wired routing, ad hoc rtg and directed diffusion • queuing protocols: RED, drop-tail, etc • Physical media: • Wired (point-to-point, LANs), wireless (multiple propagation models), satellite

  13. NS Resources • Ns Homepage • http://www.isi.edu/nsnam/ns/ • Ns and nam build questions • http://www.isi.edu/nsnam/ns/ns-build.html • Ns mailing list: ns-users@isi.edu • Ns manual and tutorial (in distribution) • TCL: http://dev.scriptics.com/scripting • Otcl tutorial (in distribution): ftp://ftp.tns.lcs.mit.edu/pub/otcl/doc/tutorial.html

  14. * * Unix Linux Windows #1 Basic Concept Commands Shell #3 C Fundamental Installation #2 #6 Unix System Programming #4 C++ Fundamental Management Guidelines & Activities Main Topics Technical Paper Presentation #7 #8 Network Concept NS-2 #5 Study Guidelines-1

  15. Study Guidelines-2 Step 1) Prepare a Linux Machine and Install Redhat Linux Operating System • http://www.redhat.com Step 2) Download NS All-in-One version(2.29.tar.gz) and Install it on your machine • http://www.isi.edu/nsnam/ns/ns-tests.html Step 3) Practice step-by-step Examples • http://perform.wpi.edu/NS/index.html Step 4) Read numerous technical papers, understand network concepts, and select main topics or problems • Related papers using NS-2 Step 5) Execute modeling and simulation • By Simulation Methodology • Use a simulation language like Otcl, C++ • Use graph and chart drawing tools such as gnuplot, excel, MatLab

  16. Overview • Developed by UCB/LBNL/VINT groups (http://www.isi.edu/nsnam/ns/) • Very popular software • Object-oriented simulator • Represents Network components & network characteristics by various classes • Written in C++ & object-oriented tcl (Otcl) scripts

  17. Model Construction & Parameter Setting • A network model in ns is constructed by interconnecting several components, called ns object. • Built from a hierarchical C++ class structure • http://www.isi.edu/nsnam/nsdoc-classes/index.html

  18. NsObject • NsObject • Base class for all derived classes • Methods • handle method to handle events • recv method to process received packets • Connector • Derive to links related objects (Queue, Delay) and nodes related objects (Agents) • Trace • Used to collect data about packets in the network during the simulation • Classifier • Examines packets & forward them to the appropriate destination • By passing the packet object to the recv method of the object • Unicast address classifier • Multicast address classifier • Replicator

  19. Major Objects-1 • Nodes • Represent clients, hosts, routers, or switches • A node s1 can be created as follows: set s1 [$ns node] • Classifiers • Determine the outgoing interface object • Address Classifiers : support unicast packet forwarding • Multicast Classifiers : classify packets based on both source and destination group address • Multipath Classifiers : support equal cost multipath forwarding • Replicators : deliver copies of the same packet to multiple receivers • Links • Used to connect nodes to form a network topology • Support for a variety of links $ns <link-type> <n1> <n2> <bandwidth> <delay> <queue-type> • link-type : simplex-link, duplex-link, or duplex-intserv-link • queue-type : DropTail, Fair Queueing (FQ), Stochastic Fair Queuing (SFQ), Deficit Round Robin scheduling (DRR), Random Early Detection (RED), or Class Based Queuing (CBQ) • Example $ns duplex-link $s1 $r1 8Mb 5ms DropTail

  20. Major Objects-2 • Agents • Have several fields to construct the appropriate packet • Source address, destination address, packet size, IP flow identifier, IP priority, flags, time to live • Can be set using the set command • Attached to a node using the attach-agent command • UDP agents • Commonly use when rate-based traffic generators (CBR or Pareto) are used at the application level. set udp_agent [new Agent/UDP] $ns attach-agent <node> $udp_agent $udp_agent set <field> <field-value> • TCP agents • Create set tcp_agent [new Agent/<tcp-agent-type>] • connect between two agents $ns connect <source agent> <destination agent> • Parameters • Window settings (window_), ECN bit (ecn_), timer granularity (tcpTick_), congestion window, ssthresh setting. $tcp_agent set window_ 15 $tcp_agent set ecn_ 1

  21. Major Objects-3 • Applications • Produce data on top of the transport layer (UDP or TCP) • Attached to the transport end points by the attach-agent command • Start (stop) sending data at specified times using the start (stop) command • Main application supported by ns • FTP, Telnet, WWW, etc • Example) a TCP agent is used as the transport layer and an FTP application runs on top of it. set tcp_agent [new Agent/TCP] $ns attach-agent $source $tcp_agent set ftp_app [new Application/FTP] $ftp_app attach-agent $tcp_agent $ns at 10.0 “$ftp_app start” $ns at 20.0 “$ftp_app stop”

  22. Major Objects-4 • Traffic Generators • Automate generation of traffic according to a desired pattern & load • Exponential ON-OFF • Generate packets at a fixed rate during the ON periods, while no packets are sent during the OFF periods. • Exponential distribution • Size of packets being generated, average ON time, average OFF time, and sending rate set expapp [new Application/Traffic/Exponential] $expapp set packetsize_ 1000 $expapp set rate_ 500k $expapp set burst_time_ 100ms $expapp set idle_time_ 30ms • Pareto ON-OFF • Pareto distribution • Self-similar traffic can be generated by aggregating several Pareto ON-OFF sources • The shape of the pareto distribution can be set as follows: set parapp [new Application/Traffic/Pareto] $parapp set shape 1.0

  23. Major Objects-5 • Traffic Generators • Constant Bit Rate (CBR) • Generates packets at a constant rate • Random noise can be introduced to vary the time between sending of packets • Constant packet sizes • Sending rate, interval between packets, size of packets, a flag to specify introduction of random noise, maximum number of packets that can be sent set cbrapp [new Application/Traffic/CBR] $cbrapp set maxpkts_ 10000 $cbrapp set packetsize_ 5000 $cbrapp set rate_ 16kb $cbrapp set interval_ 1ms $cbrapp set random 1

  24. Data Collection-1 • Tracing • Records each packets as it arrives at a node, departs a node, or is dropped at a link or queue. • Useful in debugging or verification of the simulation code • To collect the trace record of every packet $ns trace-all <tracefile> • Structure of trace files • Event Type : enqueue (+), dequeue (-), drop (d), receive (r) • Src, Dst addr : “node.port” • Example

  25. Data Collection-2 • Monitoring • Monitor counts, such as number of packets dropped, for all traffic in the network, for specific links, or for specific flows • Monitoring objects are inserted into the network topology at specific places. • To create a trace object between a src and a dest node $ns create-trace <type> <tracefile> <src> <dest> • type Enqueue, Deque, Drop, or Recv • To add a trace agent to trace the TCP congestion window variable $ns add-agent-trace $tcp_agent tcp_agent $ns monitor-agent-trace $tcp_agent $tcp_agent tracevar cwnd_

  26. Simulation Execution • An object of class Simulator must be created as follow: set ns [new Simulator] • To start an application at a specified time $ns at <time> “<command>” • Example) An FTP source can be started at time 0.0 $ns at 0.0 “$ftp_app atart” • To terminate ns • by calling the finish procedure $ns at 2.0 “finish” • To execute ns $ns run

  27. ns Examples-1 • A Simple Network Topology

  28. ns Examples-2 • Evaluating TCP Performance • Step 1: Design Network Model • Step 2 : Select Performance Metrics • Observe the throughput of the FTP connection • Monitor the rate of sequence number increase over time • Step 3 : Select Variables • Buffer size at R1 to examine the effect of buffer size on the TCP throughput • Step 4 : Construct Model & Set Parameters • Create the four nodes • Connect nodes with link • Create TCP source & sink agent • Connect source to sink • Attach FTP application to TCP transport protocol

  29. ns Examples-2 (Con’t) • Step 4 : Construct Model & Set Parameters (Cont’) • Create the four nodes set n0 [$ns node] set R1 [$ns node] set R2 [$ns node] set n1 [$ns node] • Connect nodes with link $ns duplex-link $n0 $R1 10Mb 1ms DropTail $ns duplex-link $R1 $R2 1Mb 3ms DropTail $ns duplex-link $R2 $n1 10Mb 1ms DropTail • Create TCP source & sink agent set tcp0 [new Agent/TCP] $ns attach-agent $n0 $tcp0 set tcpsink0 [new Agent/TCPSink] $ns attach-agent $n1 $tcpsink0 • Connect source to sink $ns connect $tcp0 $tcpsink0 • Attach FTP application to TCP transport protocol set ftp0 [new Application/FTP] $ftp0 attach-agent $tcp0

  30. ns Examples-2 (Con’t) • Step 5 : Data Collection • Use tracing for collecting the sequence numbers $ns trace-all [open out.tr w] • Use monitoring for collecting the throughput data #Define “bytes_” in TCP sink agent (tcp-sink.cc) void TcpSink::recv(Packet* pkt, Handler*) { ... Some line before bytes_ += hdr_cmn::access(pkt) -> size(); Double now = Scheduler::instance().clock(); ... Some line after } #Bind variables in agent’s constructor TcpAgent::TcpAgent() : Agent(PT_TCP), ... { ... Some line before bind(“seqno_”, &seqno_); ... Some line after } TcpSink::TcpSink(Acker* acker) : Agent(PT_ACK), acker_(acker), save_(NULL) { ... Some line before bind(“bytes_”, &bytes_); ... Some line after }

  31. ns Examples-2 (Con’t) #Initialize variables in ns-default.tcl to be linked to OTcl Agent/TCP set seqno_ 0 Agent/TCPSink set bytes_ 0 #Open output file for writing data set f1 [open seq.dat w] set f2 [open thruput.dat w] set f3 [open delay.dat w] #Call output variable in Tcl and write data to output file set seq [$tcp0 set seqno_] set bw [$tcpsink0 set bytes_] set delay [$tcpsink0 set e2e_delay_] puts $f1 “$now $seq” puts $f2 “$now [expr $bw/$time*8/1000]” puts $f3 “$now [expr $delay*1000]” #Recompile ns

  32. ns Examples-2 (Con’t) • Step 6 : Simulation Execution #Set simulation time, run FTP sources for 10 seconds $ns at 0.0 “$ftp0 start” $ns at 10.0 “$ftp0 stop” $ns at 0.0 “record” $ns at 10.0 “finish” $ns run • Step 7 : Presentation & Analysis of Simulation Results exec awk { { if (($1 == “r”) && ($4 == “0”) && ($5 == “ack”)) print $2, $11 } } out.tr > datafile

More Related