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Marc Greis` Tutorial for the UCB/LBNL/VINT Network Simulator "ns"

1. provide each mobilenode with hier address of its base station Next connect wired nodes and BS and setup TCP traffic between wireless node node_ 0 and wired node W 0 and between W 1 and node_ 2 as shown below create links between wired and BS nodes Sns_ duplex link S W 0 W 1 5Mb 2ms DropTail Sns_ duplex link W 1 BS 0 5Mb 2ms DropTail Sns_ duplex link op W 0 SW 1 orient down Sns_ duplex link op W 1 BS 0 orient left down setup TCP connections set tcpl new Agent TCP tepl see class 2 set sinkl new Agent TCPSink Sns_ attach agent Snode_ 0 S tcpl Sns_ attach agent W 0 Ssinkl Sns_ connect tcpl sinkl set ftpl new Application FTP Sftpl attach agent Stcpl Sas at Ses icol sicaicic VSiticjeil steunt set tcp2 new Agent TCP Stcp2 set class_ 2 set sink2 new Agent TCPSink Sns_ attach agent W 1 Stcp2 Sns_ attach agent Snode_ 2 S sink2 Sns_ connect tcp2 sink2 set ftp2 new Application FTP Sftp2 attach agent Stcp2 Sins eice Seyi rep start WSs psiceucie This would be followed by the remaining lines from wireless 1 tcl sourcing cp and sc files telling mobilenodes when to stop and finally running ns It is possible that some lines of code in wireless2 tcl have not been discussed here For a complete copy of script wireless2 tcl download from here Run the script The ns and nam trace files are generated at the end of simulation run Running wireless2 out nam show
2. Configure for ForeignAgent and HomeAgent nodes Sns_ node config mobileIP ON adhocRouting Sopt adhocRouting Slhilnyos Ses ill macType Sopt mac ifgqIype opt ifq eben Sojore Eedem N antType Sopt ant propType opt prop phyType Sopt netif channelType Sopt chan N topoInstance topo wiredRouting ON agentTrace ON routerTrace OFF MACI CERORE Create HA and FA set HA ns_ node set FA ns_ node SHA random motion FA random motion Cone ja HI SS So je TS S provide some co ord fixed to these base station nodes SHA set X_ 1 000000000000 SHA set Y_ 2 000000000000 SHA set Z_ 0 000000000000 SFA set X_ 650 000000000000 SFA set Y_ 600 000000000000 SFA set Z_ 0 000000000000 Next create the mobilehost as follows Note as before we have to turn off the option wiredRouting used for creation of base station nodes before creating mobilenodes Also the HA is setup as the home agent for the mobilehost The MH has an address called the care of address COA Based on the registration beacons exchanged between the MH and the base station node of the domain the MH is currently in the base station s address is assigned as the MH s COA Thus in this simulation address of HA is assigned initially as the COA of MH As MH moves in to the domain of FA its COA changes to that of the FA For details on MobileIP implementation in ns read section 15 2 2 of in wireless networking chapter ns_
3. Sns attach agent n0 Sudp0 Create a CBR traffic source and attach it to udp0 set cbrO new Application Traffic CBR ScbrO set packetSize_ 500 ScbrO set interval_ 0 005 ScbrO attach agent Sudp0 Create a UDP agent and attach it to node nl set udpl new Agent UDP Sme attach agent Smil Sudpl Create a CBR traffic source and attach it to udpl set cbrl new Application Traffic CBR Scbrl set packetSize_ 500 Scloril set interval 0 005 Scbrl attach agent Sudpl set null0O new Agent Null Sns attach agent n3 Smula i The two CBR agents have to be connected to the Null agent Sns connect Sucot Snull10 Sns connect Sudpl Snul110 We want the first CBR agent to start sending at 0 5 seconds and to stop at 4 5 seconds while the second CBR agent starts at 1 0 seconds and stops at 4 0 seconds Sns Sns Sns Sns at at at at Cie loyal Seiri Woe loreal YSE ss SS Gar Key Sy Oy SE TER Siarc Seon stop When you start the script now with ns example2 tcl you will notice that there is more traffic on the links from nO to n2 and nl to n2 than the link from n2 to n3 can carry A simple calculation confirms this We are sending 200 packets per second on each of the first two links and the packet size is 500 bytes This results in a bandwidth of 0 8 megabits per second for the links from nO to n2 and from n1 to n2 That s a total bandwidth of 1 6Mb s but the link between n2 and n3 onl
4. documentation Also see files mip cc h mip reg cc h tcl lib ns mip tcl ns wireless mip tcl configure for mobilehost Sns_ node config wiredRouting OFF create mobilehost that would be moving between HA and FA note address of MH indicates its in the same domain as HA set MH ns_ node 1 0 1 set node_ 0 MH set HAaddress AddrParams set hieraddr HA node addr SMH set regagent_ set home_agent_ HAaddress movement of the MH SMH set Z_ 0 000000000000 SMH set Y_ 2 000000000000 SMH set X_ 2 000000000000 MH starts to move towards FA 640 610 at a speed of 20m s Sns_ at 100 000000000000 SMH setdest 640 000000000000 610 000000000000 20 000000000000 and goes back to HA 2 2 at a speed of 20 m s Sns at 200 000000000000 SMH setdest 2 000000000000 2 000000000000 20 000000000000 Create links between Wired nodes and HA FA and setup TCP connection create links between wired and BaseStation nodes Sns_ duplex link S W 0 W 1 5Mb 2ms DropTail Sns_ duplex link S W 1 SHA 5Mb 2ms DropTail Sns_ duplex link S W 1 SFA 5Mb 2ms DropTail Sns_ duplex link op W 0 S W 1 orient down Sns_ duplex link op W 1 SHA orient left down Sns_ duplex link op W 1 SFA orient rignt donn setup TCP connections between a wired node and the MobileHost set tcpl new Agent TCP Seciol set class _ 2 set sinkl new Agent TCPSink Sns_ attach agent W 0 Stcpl Sns_ attach agent MH S Ssink1l Sns_ connect
5. ns at 10 0 SsourceO0 start Sns at 10 0 Ssourcel start Sns at 10 0 Ssource2 start ns at 50 0 source0 stop ns at 50 0 Ssourcel stop S ns at 50 0 source2 stop ns at 60 0 finish ns run First the record procedure is called and afterwards it will re schedule itself periodically every 0 5 seconds Then the three traffic sources are started at 10 seconds and stopped at 50 seconds At 60 seconds the finish procedure is called You can find the full example script here When you run the simulation an xgraph window should open after some time which should look similar to this one Pa anal arly awn WIT 5 i i aa As you can see the bursts of the first flow peak at 0 1 Mbit s the second at 0 2Mbit s and the third at 0 3Mbit s Now you can try to modify the time value in the record procedure Set it to 0 1 and see what happens and then try 1 0 It is very important to find a good time value for each simulation scenario Note that the output files created by the record procedure can also be used with gnuplot Previous section Next section Back to the index ns users ns users isi edu IX Running Wireless Simulations in ns Previous section Next section Back to the index In this section you are going to learn to use the mobile wireless simulation model available in ns The section consists of two parts In the first subsection we discuss how to create and run a simple 2 node wi
6. channelType Channel WirelessChannel topolInstance Stopo energyModel EnergyModel initialEnergy in Joules rxPower in W txPower in W agentTrace ONO OEE SwOieSie WieeeS ON Gre Ole See WES ON ora Eis movementTrace ON or OFF All default values for these options are NULL except addressingType flat We are going to use the default value of flat addressing Also lets turn on only AgentTrace and RouterTrace You can experiment with the traces by turning all of them on AgentTraces are marked with AGT RouterTrace with RTR and MacTrace with MAC in their 5th fields MovementTrace when turned on shows the movement of the mobilenodes and the trace is marked with M in their 2nd field The configuration API for creating mobilenodes looks as follows Configure nodes Sne node config adhocRouting S val rp L brype Sxl LL y macType val mac ifqType Sval ifq ifqhen val ifqlen y antType S val ant propType val prop phyType Sval netif topoInstance topo channelType Sval chan agentTrace ON SIeOUMESicMicacS ON macTrace OFF movementTrace OFF Next we create the 2 mobilenodes as follows ror sei a Of Si lt Swell im aimee ir f sae oce S1 Sas noce i snode 1 random motion 0 disable random motion The random motion for nodes is disabled here as we are going to provide node position and movement speed amp direction directives next Now that
7. use ifdef etc so you can easily remove your changes or port them to new ns releases We re going to need a new packet type for the ping agent so the first step is to edit the file packet h There you can find the definitions for the packet protocol IDs i e PT_TCP PT_TELNET etc Add a new definition for PT_PING there In my edited version of packet h the last few lines of enum packet_t looks like the following code it might look a bit different in earlier later releases enum packet_t PIE Cle PME WIDIE insert new packet types her PE IRC PE INEINC INCI PT_PING l packet prococol ID ror our pang agente PT_NTYPE This MUST be the LAST one You also have to edit the p_info in the same file to include Ping elass Q inro PURIHEIGE D imco name_ PT_TCP tcp name_ PT_UDP udp name_ P FRC tcpFriend name_ P FRC_ACK tcpFriendCt1 name_ PT_PING Ping name_ PT_NTYPE undefined Remember that you have to do a make depend before you do the make otherwise these two files might not be recompiled The file tcl lib ns default tcl has to be edited too This is the file where all default values for the Tcl objects are defined Insert the following line to set the default packet size for Agent Ping Agent Ping set packetSize_ 64 You also have to add an entry for the new ping packets in the file tcl lib ns packet tcl in the li
8. See cbr 3 test to find out more about the traffic flows that are setup These traffic pattern files can also be generated using CMU s TCP CBR traffic generator script More about this is discussed in section XI 1 of this tutorial We shall make changes to the script simple wireless tcl we had created in section IX 1 and shall call the resulting file wireless 1 tcl For a copy of wireless 1 tcl download from here In addition to the variables LL MAC antenna etc that were declared at the beginning of the script we now define some more parameters like the connection pattern and node movement file x and y values for the topology boundary a seed value for the random number generator time for the simulation to stop for convinience They are listed as follows set val chan Channel WirelessChannel set val prop Propagation TwoRayGround set val netif Phy WirelessPhy set val mac Mac 802_11 set val ifq Queue DropTail PriQueue sire welll LiL LL set val ant Antenna OmniAntenna set val x 670 X dimension of the topography set val y 670 Y dimension of the topography set val ifqlen 50 max packet in ifq set val seed ORO set val adhocRouting DSR set val nn 3 how many nodes are simulated set val cp mobility scene cbr 3 test set val sc mobility scene scen 3 test set val stop 2000 0 simulation time Number of mobilenodes is changed to 3 Also we use DSR dynamic source routing as the
9. Snf The first line opens the file out nam for writing and gives it the file handle nf In the second line we tell the simulator object that we created above to write all simulation data that is going to be relevant for nam into this file The next step is to add a finish procedure that closes the trace file and starts nam proe rimissa global ns nf Sns flush trace ClOSS Sime SKS Miei OWIE wield e exit 0 You don t really have to understand all of the above code yet It will get clearer to you once you see what the code does The next line tells the simulator object to execute the finish procedure after 5 0 seconds of simulation time Sns ate 5 0 itslinaein You probably understand what this line does just by looking at it ns provides you with a very simple way to schedule events with the at command The last line finally starts the simulation Sns run You can actually save the file now and try to run it with ns example1 tcl You are going to get an error message like nam empty trace file out nam though because until now we haven t defined any objects nodes links etc or events We are going to define the objects in section 2 and the events in section 3 You will have to use the code from this section as starting point in the other sections You can download it here IV 2 Two nodes one link In this section we are going to define a very simple topology with two nodes that are connect
10. Tclcl libs and then creates the executable setdest 3 Run setdest with arguments as shown below setdest n num_of_nodes p pausetime s maxspeed t simtime x maxx y maxy gt outdir movement file Lets say we want to create a node movement scenario consisting of 20 nodes moving with maximum speed of 10 0m s with an average pause between movement being 2s We want the simulation to stop after 200s and the topology boundary is defined as 500 X 500 So our command line will look like jsercasc a 20 9 2 0 10 0 r 200 x 500 y 500 gt scen 2O resic The output is written to stdout by default We redirect the output to file scen 20 test The file begins with the initial position of the nodes and goes on to define the node movements Sns_ at 2 000000000000 Snode_ 0 setdest 90 441179033457 44 896095544010 1 SISSSOLOVOLO This line from scen 20 test defines that node_ 0 at time 2 0s starts to move toward destination 90 44 44 89 at a speed of 1 37m s These command lines can be used to change direction and speed of movement of mobilenodes Directives for GOD are present as well in node movement file The General Operations Director GOD object is used to store global information about the state of the environment network or nodes that an omniscent observer would have but that should not be made known to any participant in the simulation Currently the god object is used only to store an array of the shorte
11. and nam output file wireless1 out nam are created Running wireless 1 out nam we see the three mobilenodes moving in nam window However as mentioned earlier no traffic flow can be seen not supported as yet For a variety of coarse and fine grained trace outputs turn on off AgentTrace RouteTrace MacTrace and movementTrace as shown earlier in the script From the CMUTrace output we find nodes 0 and 2 are out of range and so cannot hear one another Node is in range with nodes 0 and 2 and can communicate with both of them Thus all pkts destined for nodes 0 and 2 are routed through node 1 For details on X Creating Wired cum Wireless and MobilelP Simulations in ns Previous section Next section Back to the index IMPORTANT This tutorial chapter uses new node APIs which are not available in the ns2 1b5 version So please download the daily snapshot unless a release is made for version ns2 1b6 or higher The current snapshot version is updated daily so please check the validation test results for that day before downloading as these snapshots can sometimes be unstable due to ongoing changes made by ns developers X 1 Creating a simple wired cum wireless scenario The wireless simulation described in section IX supports multi hop ad hoc networks or wireless LANs But we may need to simulate a topology of multiple LANs connected through wired nodes or in other words we need to create a wired cum wireless topology In this section
12. click directly on the link to get some graphs with statistics I also suggest that you try to change the packetsize_ and interval_ parameters in the Tcl script to see what happens You can download the full example here Most of the information that I needed to be able to write this Tcl script was taken directly from the example files in the tcl ex directory while I learned which CBR agent arguments packetSize_ interval_ I had to set from the ns manual page V Making it more interesting Previous section Next section Back to the index In this section we are going to define a topology with four nodes in which one node acts as router that forwards the data that two nodes are sending to the fourth node I will explain find a way to distinguish the data flows from the two nodes from each other and I will show how a queue can be monitored to see how full it is and how many packets are being discarded V 1 The topology As always the first step is to define the topology You should create a file example2 tcl using the code from section IV 1 as a template As I said before this code will always be similar You will always have to create a simulator object you will always have to start the simulation with the same command and if you want to run nam automatically you will always have to open a trace file initialize it and define a procedure which closes it and starts nam Now insert the following lines into the
13. code to create four nodes set nO Sns node set nl Sns node set n2 Sns node set n3 Sns node The following piece of Tcl code creates three duplex links between the nodes Sns duplex link n0 n2 1Mb 10ms DropTail Sns duplex link nl n2 1Mb 10ms DropTail Sns duplex link n3 n2 1Mb 10ms DropTail You can save and start the script now You might notice that the topology looks a bit awkward in nam You can hit the re layout button to make it look better but it would be nice to have some more control over the layout Add the next three lines to your Tcl script and start it again Sns duplex link op n0 n2 orient right down Sns duplex link op nl n2 orient right up Sns duplex link op n2 n3 orient right You will probably understand what this code does when you look at the topology in the nam window now It should look like the picture below Note that the autolayout related parts of nam are gone since now you have taken the layout into your own hands The options for the orientation of a link are right left up down and combinations of these orientations You can experiment with these settings later but for now please leave the topology the way it is V 2 The events Now we create two UDP agents with CBR traffic sources and attach them to the nodes n0 and n1 Then we create a Null agent and attach it to node n3 Create a UDP agent and attach it to node n0 set udpO new Agent UDP
14. node set n1 ns node set n2 ns node set n3 ns node set n4 ns node ns duplex link n0 n3 1Mb 100ms DropTail ns duplex link n1 n3 1Mb 100ms DropTail ns duplex link n2 n3 1Mb 100ms DropTail ns duplex link n3 n4 1Mb 100ms DropTail We are going to attach traffic sources to the nodes n0 n1 and n2 but first we write a procedure that will make it easier for us to add the traffic sources and generators to the nodes proc attach expoo traffic node sink size burst idle rate Get an instance of the simulator set ns Simulator instance Create a UDP agent and attach it to the node set source new Agent UDP ns attach agent node Ssource Create an Expoo traffic agent and set its configuration parameters set traffic new Application Traffic Exponential Straffic set packet size size Straffic set burst time S burst Straffic set idle time idle Straffic set rate Srate Attach traffic source to the traffic generator traffic attach agent source Connect the source and the sink ns connect source sink return Straffic This procedure looks more complicated than it really is It takes six arguments A node a previously created traffic sink the packet size for the traffic source the burst and idle times for the exponential distribution and the peak rate For details about the Expoo traffic sources please refer to the documentation for ns First the procedure creates a traffic source and attaches it to
15. setdest program see section XI 2 generates movement pattern files using the random waypoint algorithm The node movement files generated using setdest like scen 3 test already include lines like above to load the god object with the appropriate information at the appropriate time A program called calcdest ns indep utilities cmu scen gen setdest calcdest can be used to annotate movement pattern files generated by other means with the lines of god information calcdest makes several assumptions about the format of the lines in the input movement pattern file which will cause it to fail if the file is not formatted properly If calcdest rejects a movement pattern file you have created the easiest way to format it properly is often to load it into ad hockey and then save it out again If ad hockey can read your input correctly its output will be properly formatted for calcdest Both setdest and calcdest calculate the shortest number of hops between nodes based on the nominal radio range ignoring any effects that might be introduced by the propagation model in an actual simulation The nominal range is either provided as an argument to the programs or extracted from the header in node movement pattern files The path length information provided to god was used by CMU s Monarch Project to analyze the path length optimality of ad hoc network routing protocols and so was printed out as part of the CMUTrace output for each packet Other uses that C
16. tcpl sinkl set ftpl new Application FTP Sftpl attach agent Stcpl Sis sie Sope epl stare Msiricjell pieacic The rest of the script remains unchanged i e tell mobilenodes when the simulation stops Save and run the script Click here for a copy of the file wireless3 tcl While running the script you may see warnings like warning Route to base_stn not known dropping pkt This means that as the MH moves from the domain of one base station into domain of another there may be interim periods when it is not registered to any base station and thus doesnot know whom to forward pkts destined outside its domain On completion of the run ns and nam trace output files wireless3 out tr and wireless3 out nam are created The nam output shows the movement of the mobilehost and traffic flow in the wired domain The ns trace output shows traces for both the wired nodes as well as the wireless domain We see routine beacon broadcast solicitations sent out by HA FA and the MH Initially the TCP pkts are handed down to MH directly by its HA As MH moves away from HA domain into the domain of the FA we find the pkts destined for MH being encapsulated and forwarded to the FA which then strips off or decapsulates the pkt and hands it over to the MH Previous section Next section Back to the index VINT ns users isi edu XI Generating node movement and traffic connection files for large wireless scenarios Previous section Back to t
17. the node then it creates a Traffic Expoo object sets its configuration parameters and attaches it to the traffic source before eventually the source and the sink are connected Finally the procedure returns a handle for the traffic source This procedure is a good example how reoccuring tasks like attaching a traffic source to several nodes can be handled Now we use the procedure to attach traffic sources with different peak rates to n0 n1 and n2 and to connect them to three traffic sinks on n4 which have to be created first set sinkO new Agent LossMonitor set sinkl new Agent LossMonitor set sink2 new Agent LossMonitor ns attach agent n4 sink0 ns attach agent n4 sink1 ns attach agent n4 sink2 set source0 attach expoo traffic n0 sink0 200 2s 1s 100k set sourcel attach expoo traffic nl sinkl 200 2s 1s 200k set source2 attach expoo traffic n2 sink2 200 2s 1s 300k In this example we use Agent LossMonitor objects as traffic sinks since they store the amount of bytes received which can be used to calculate the bandwidth VIII 2 Recording Data in Output Files Now we have to open three output files The following lines have to appear early in the Tcl script set f0 open out0 tr w set f1 open outl tr w set f2 open out2 tr w These files have to be closed at some point We use a modified finish procedure to do that proe Cinisi f global 0 f1 2 Close the output files close TO close TI cl
18. to udp0d set cbrO new Application Traffic CBR ScbrO set packetSize_ 500 ScbrO set interval_ 0 005 ScbrO attach agent Sudp0 These lines create a UDP agent and attach it to the node nO then attach a CBR traffic generatot to the UDP agent CBR stands for constant bit rate Line 7 and 8 should be self explaining The packetSize is being set to 500 bytes and a packet will be sent every 0 005 seconds i e 200 packets per second You can find the relevant parameters for each agent type in the ns manual page The next lines create a Null agent which acts as traffic sink and attach it to node n1 set null0O new Agent Null Sns attach agent Sal mulia pr Now the two agents have to be connected with each other Sns connect Sudp0O Snull10 And now we have to tell the CBR agent when to send data and when to stop sending Note It s probably best to put the following lines just before the line ns at 5 0 finish Sng at 0 5 Voco srar Sms adt 4 5 Ycbri srog This code should be self explaining again Now you can save the file and start the simulation again When you click on the play button in the nam window you will see that after 0 5 simulation seconds node 0 starts sending data packets to node 1 You might want to slow nam down then with the Step slider OF I suggest that now you start some experiments with nam and the Tcl script You can click on any packet in the nam window to monitor it and you can also
19. we are going to extend the simple wireless topology created in section IX to create a mixed scenario consisting of a wireless and a wired domain where data is exchanged between the mobile and non mobile nodes We are going to make modifications to the tcl script called wireless 1 tcl created in section IX 2 and name the resulting wired cum wireless scenario file wireless2 tcl For the mixed scenario we are going to have 2 wired nodes W 0 and W 1 connected to our wireless domain consisting of 3 mobilenodes nodes 0 1 amp 2 via a base station node BS Base station nodes are like gateways between wireless and wired domains and allow packets to be exchanged between the two types of nodes For details on base station node please see section 2 wired cum wireless networking of chapter 15 of ns_ notes amp doc now renamed as ns Manual Fig1 shows the topology for this example described above Wo Vk BS 0 Base station node i Node 1 No e oN 0 de 2 Wireless mobilenodes Wireless mobilenodes Fig Topology for wired cum wireless simulation example Let us begin by checking what changes need to be made to the list of variables defined at the beginning of wireless1 tcl The Adhoc routing protocol is changed to DSDV Also we define TCP and CBR connections between the wired and wireless nodes in the script itself So we won t need to use the connection pattern file used in earlier simulation Also change the si
20. Agent at nodel which then sends an ACK back to nodeO and the TCP connection is setup However as node starts to move away from node0 the connection breaks down again around time 116 0s Pkts start getting dropped as the nodes move away from one another IX 2 Using node movement traffic pattern files and other features in wireless simulations As an extension to the previous sub section we are going to simulate a simple multihop wireless scenario consisting of 3 mobilenodes here As before the mobilenodes move within the boundaries of a defined topology However the node movements for this example shall be read from a node movement file called scen 3 test scen 3 test defines random node movements for the 3 mobilenodes within a topology of 670mX670m This file is available as a part of the ns distribution and can be found along with other node movement files under directory ns tcl mobility scene Random node movement files like scen 3 test can be generated using CMU s node movement generator setdest Details on generation of node movement files are covered in section XI 2 of this tutorial In addition to node movements traffic flows that are setup between the mobilenodes are also read from a traffic pattern file called cbr 3 test cbr 3 test is also available under ns tcl mobility scene Random CBR and TCP flows are setup between the 3 mobilenodes and data packets are sent forwarded or received by nodes within hearing range of one another
21. MU has found for the information are e Characterizing the rate of topology change in a movement pattern e Identifying the frequency and size of partitions e Experimenting with the behavior of the routing protocols if the god information is used to provide them with perfect neighbor information at zero cost Next add the following lines for providing initial position of nodes in nam However note that only node movements can currently be seen in nam Dumping of traffic data and thus visualization of data pkt movements in nam for wireless scenarios is still not supported future work Define node initial position in nam tor se a OF Sa lt Sve mim tanci af 4 20 defines the node size in nam must adjust it according to your scenario size The function must be called after mobility model is defined Sns_ initial_node_pos Snode_ i 20 Next add informative headers for the CMUTrace file just before the line ns_ run puts Stracefd M 0 0 nn val nn x val x y val y rp val adhocRouting puts Stracefd M 0 0 sc val sc cp Sval cp seed val seed puts Stracefd M 0 0 prop S val prop ant Sval ant The rest of the script remains unchanged Save the file wireless1 tcl Make sure the connection pattern and node movement files exist under the directories as declared above Run the script by typing at the prompt ms wirelessi cal On completion of the run CMUTrace output file wireless1 out tr
22. Tutorial for the Network Simulator ns I Introduction Next section Back to the index Disclaimer This tutorial was originally developed by Marc Greis Currently the tutorial is maintained and being expanded by the VINT group Please note if there is any problem with the example scripts provided below please refer to the test suites ns tcl test test suite greis tcl and test suite WLtutorial tcl for and lastest updates and let us know thanks Since you have found this page I assume that you already know what ns is and where you can get it from If not I suggest you either go to the web page for the VINT project or the web page for ns version 2 Note In these pages I describe ns version 2 Version 1 is different though there is a backwards compatibility library in version 2 The purpose of these pages is to make it easier for new ns users to use ns and nam to create their own simulation scenarios for these tools and to eventually add new functionality to ns I have found the existing documentation to be rather useful for users who already know the basic features of ns while it can be a bit tedious for new users to extract the necessary information from the manuals and the example scripts In this tutorial I will lead you through some simple examples introducing more and more new features as we go along The ultimate goal is that after a short time you are able to efficiently use ns and to find any further informati
23. adhoc routing protocol inplace of DSDV Destination sequence distance vector After creation of ns_ the simulator instance open a file wireless 1 out tr for wireless traces Also we are going to set up nam traces set tracefd open wirelessl out tr w Smag icwace alll Siciracsicc for wireless traces set namtrace open wirelessl out nam w for nam tracing Sns_ namtrace all wireless Snamtrace Sval x S val y Next after creation of mobilenodes source node movement and connection pattern files that were defined earlier as val sc and val cp respectively Define node movement model puts Loading connection pattern source Sval cp Define traffic model puts Loading scenario file source Sval sc In node movement file scen 3 test we see node movement commands like Sns_ at 50 000000000000 Snode_ 2 setdest 369 463244915743 L170 5192031152 3 37LISSEOSISAY This as described in earlier sub section means at time 50s node2 starts to move towards destination 368 4 170 5 at a speed of 3 37m s We also see other lines like SqocL_ seic cisic 1 2 2 These are command lines used to load the god object with the shortest hop information It means the shortest path between node 1 and 2 is 2 hops By providing this information the calculation of shortest distance between nodes by the god object during simulation runs which can be quite time consuming is prevented The
24. asics o II 1 Downloading Installing ns amp nam o IM 2 Starting ns o M 3 Starting nam IV The first Tcl script o IV 1 How to start o IV 2 Two nodes one link o IV 3 Sending data V Making it more interesting o V 1 The topology o V 2 The events o V 3 Marking flows o V 4 Monitoring a queue VI Network dynamics V1 1 Creating a larger topology VI 2 Link failure VII A new protocol for ns o VIL1 The header file o VI 2 The C code o VII 3 Necessary changes o VIL4 The Tcl code VIII Creating Output Files for Xgraph o VHI 1 Topology and Traffic Sources o VHI 2 Recording Data in Output Files o VHI 3 Running the Simulation IX Running Wireless Simulations in ns o IX 1 Creating a simple wireless scenario o IX 2 Using node movement traffic pattern files and other extensions for wireless simulations X Creating Wired cum Wireless and MobileIP Simulations o X 1 Creating a simple wired cum wireless scenario o X 2 Running MobileIP in a simple wired cum wireless topology XI Generating traffic connection and node movement files for large wireless scenarios o XI l Creating random traffic pattern for wireless scenarios o XI 2 Creating node movements for wireless scenarios Next section Version with frames ns users ll Finding Documentation Previous section Next section Back to the index In this section I am going to list some sources for docume
25. ass jowlolL aL s PingClass TclClass Agent Ping TclObject create int const char const return new PingAgent Cllassjosling p The next piece of code is the constructor for the class PingAgent It binds the variables which have to be accessed both in Tcl and C PingAgent PingAgent Agent PT_PING bind packetSize_ amp size_ loalinGl Yor ome Yy COLE OLACG e The function command is called when a Tcl command for the class PingAgent is executed In our case that would be pa send assuming pa is an instance of the Agent Ping class because we want to send ping packets from the Agent to another ping agent You basically have to parse the command in the command function and if no match is found you have to pass the command with its arguments to the command function of the base class in this case Agent command The code might look very long because it s commented heavily int PingAgent command int argc const char const argv ic ange 2 ii stromo aucen 1 YsencH 1 Create a new packet Peels jolie euliloejolcc 2 Access the Ping header for the new packet lance oae aei ace oine okie raes Orr oLa Set the ret field to 0 so the receiving node knows that it has to generate an echo packet hdr ret Op Store the current time in the send_time field hdr gt send_time Scheduler instance clock Send the packe
26. e version 2 1b2 instead or go to the ns web page to download a current snapshot of ns If you do that you have to unzip and untar the file in your allinone directory Then you change into the new directory and run configure then make II 2 Starting ns You start ns with the command ns lt tclscript gt assuming that you are in the directory with the ns executable or that your path points to that directory where lt tclscript gt is the name of a Tcl script file which defines the simulation scenario i e the topology and the events You could also just start ns without any arguments and enter the Tcl commands in the Tcl shell but that is definitely less comfortable For information on how to write your own Tcl scripts for ns see section IV Everything else depends on the Tcl script The script might create some output on stdout it might write a trace file or it might start nam to visualize the simulation Or all of the above These possibilities will all be discussed in later sections II 3 Starting nam You can either start nam with the command nam lt nam file gt where lt nam file gt is the name of a nam trace file that was generated by ns or you can execute it directly out of the Tcl simulation script for the simulation which you want to visualize The latter possibility will be described in Section IV For additional parameters to nam see the nam manual page Below you can see a screenshot of a nam window where the
27. ed by a link The following two lines define the two nodes Note You have to insert the code in this section before the line ns run or even better before the line ns at 5 0 finish set nO Sns node set n1 ns node A new node object is created with the command ns node The above code creates two nodes and assigns them to the handles nO and n1 The next line connects the two nodes Sns duplex link n0 nl 1Mb 10ms DropTail This line tells the simulator object to connect the nodes nO and n1 with a duplex link with the bandwidth 1 Megabit a delay of 10ms and a DropTail queue Now you can save your file and start the script with ns example1 tcl nam will be started automatically and you should see an output that resembles the picture below You can download the complete example here if it doesn t work for you and you think you might have made a mistake IV 3 Sending data Of course this example isn t very satisfying yet since you can only look at the topology but nothing actually happens so the next step is to send some data from node nO to node n1 In ns data is always being sent from one agent to another So the next step is to create an agent object that sends data from node n0 and another agent object that receives the data on node n1 Create a UDP agent and attach it to node n0 set udpO new Agent UDP Sns attach agent SnO Sudp0 Create a CBR traffic source and attach it
28. en WO and MH As MH moves out from the domain of its HA into the domain of FA we will observe how pkts destined for MH is redirected by its HA to the FA as per mobileIP protocol definitions See fig2 below for the topology described above Wired domain HA MH Y ee hEn i Wireless domain moving between HA and FA Fig2 Topology for mobileIP simulation example We shall edit wireless2 tcl created in section X 1 to create the wireless mip script called wireless3 tcl It may be possible that the whole of wireless3 tcl is not discussed here So for convinience you may download a copy of wireless3 tcl from here Change number of mobilenodes and time of simulation set opt nn 1 Just one MH set opt stop 250 In this example we will set up the TCP connection as well as define movement of the MH in the script itself Hence we are not going to use the cp and sc files Set opii cp gi Seu OPE Sc ie Define the TCP flow starttime set opt ftpl start 100 0 Change number of wired base station and mobile nodes However note that the variable num_bs_nodes is not really used in this script The base station nodes HA and FA are individually created and handled set num_wired_nodes 2 After the 2 lines creating ns instance and setting address format to hierarchical add the following lines to define the topological hierarchy It is quite similar to that of wireless2 tcl except that now we have a third domain for t
29. enamed as ns Manual At the beginning of a wireless simulation we need to define the type for each of these network components Additionally we need to define other parameters like the type of antenna the radio propagation model the type of ad hoc routing protocol used by mobilenodes etc See comments in the code below for a brief description of each variable defined The array used to define these variables val is not global as it used to be in the earlier wireless scripts For details and available optional values of these variables see chapter 15 mobile networking in ns of ns documentation We begin our script simple wireless tcl with a list of these different parameters described above as follows Define options set val chan Channel WirelessChannel channel type set val prop Propagation TwoRayGround radio propagation model set val ant Antenna OmniAntenna Antenna type set val 11 LL Link layer type set val ifq Queue DropTail PriQueu Interface queue typ set val ifqlen 50 max packet in ifq set val netif Phy WirelessPhy network interface type set val mac Mac 802_11 MAC type set val rp DSDV 7 ad hoc routing protocol set val nn 2 number of mobilenodes Next we go to the main part of the program and start by creating an instance of the simulator SE ng new Simulator Then setup trace support by o
30. es in the same cluster in wired domain 0 Also we could have placed other wireless nodes in different clusters in wireless domain 1 Also depending on our topology we may have got rid of clusters altogether and simply have had 2 layers of hierarchy the domains and the nodes configure for base station node Sns_ node config adhocRouting Sopt adhocRouting SlliltyioS Soot li macType opt mac ifqType Sopt ifq ifqhen Sopt ifqlen antType Sopt ant propType Sopt prop phyType Sopt netif channelType Sopt chan topoInstance topo wiredRouting ON agentTrace ON routerTrace OFF WEC ACE OUT create base station node sae cout 1 0 0 Lo0 t 1 0 2 1 0 3 hier address to be used for wireless domain Sete BSW I Sns noce linces Srana Oll SBS 0 random motion 0 disable random motion provide some co ordinates fixed to base station node BS 0 set X_ 1 0 S88 0 see X 2 0 BS 0 set Z_ 0 0 create mobilenodes in the same domain as BS 0 note the position and movement of mobilenodes is as defined in Sopt sc Note there has been a change of the earlier AddrParams epiaCicsloim Veverc lalereciclcle joo VY euckole2atcl configure for mobilenodes Sns_ node config wiredRouting OFF now create mobilenodes ftom leer J O S53 lt Soo im ainew Jr 4 set node_ 3j ns_ node lindex Stemp esp isai m node_ j base station AddrParams addr2id BS 0 node addr
31. et field to 1 so the receiver won t send another echo hdrret gt ret 1 Set the send_time field to the correct value hdrret gt send_time stime Send the packet send pktret 0 else A packet was received Use tcl eval to call the Tcl interpreter with the ping results Hi Nores Win the Well coce A procecure VNG Sine Paling recy r00 rtt has to be defined which allows the user to react to the ping hii results chara o ute lO Oy F Prepare the output to the fd teip time sprime Oule VSS wecy eae o nane hdrip gt src_ addr_ gt gt Address instance NodeShift_ 1 Secheqduilleta ss amet ance le Clocks On hda scmcmntasme OOO Tele wel Wells ssinisiweines l tcl eval out Discard the packet Packet free pkt cl interpreter Calculate the round You can download the full file here The most interesting part should be the tcl eval function where a Tcl function recv is called with the id of the pinged node and the round trip time in miliseconds as parameters It will be shown in Section VII 4 how the code for this function has to be written But first of all some other files have to be edited before ns can be recompiled VII 3 Necessary changes You will have to change some things in some of the ns source files if you want to add a new agent especially if it uses a new packet format I suggest you always mark your changes with comments
32. he FA Change the cluster and node parameters accordingly AddrParams set domain_num_ 3 number of domains lappend cluster_num 2 1 1 number of clusters in each domain AddrParams set cluster_num_ Scluster_num lapperne Cillasicieywel 1 1 2 1 7 number of nodes in each cluster AddrParams set nodes_num_ Seilastlevel of each domain Next set up ns trace and nam files for wireless mip set tracefd open wireless3 out tr w set namtrace open wireless3 out nam w Sns_ trace all Stracefd Sns_ namtrace all wireless Snamtrace Sopt x Sopt y So in this topology we have one wired domain denoted by 0 and 2 wireless domains denoted by amp 2 respectively Hence as described in section X 1 the wired node addresses remain the same 0 0 0 and 0 1 0 In the first wireless domain domain 1 we have base station HA and mobilenode MH in the same single cluster Their addresses are 1 0 0 and 1 0 1 respectively For the second wireless domain domain 2 we have a base station FA with an address of 2 0 0 However in the course of the simulation the MH will move into the domain of FA and we shall see how pkts originating from a wired domain and destined to MH will reach it as a result of the MobileIP protocol Wired nodes will be created as earlier However in place of a single base station node a HA and FA will be created Note here that to turn the mobileIP flag on we have configure the node structure accordingly using option mobileIP ON
33. he index We have used traffic pattern and node movement files available with the ns distribution for simulation examples in section IX and section X In this section we will discuss how to use CMU s traffic and scenario generating scripts to create these files This section is divided into 2 subsections The first subsection talks about the traffic pattern generating script how it works and the random TCP and or CBR flows it produces The second subsection is about CMU s node movement generator setdest which can be used to create random waypoint node movements for mobilenodes IMPORTANT This tutorial chapter uses a revised version of setdest which is not available in the ns2 1b5 version So please download the daily snapshot unless a release is made for version ns2 1b6 or higher The current snapshot version is updated daily so please check the validation results for that day before downloading as these snapshots can sometimes be unstable due to ongoing changes made by ns developers XI 1 Creating random traffic pattern for wireless scenarios Random traffic connections of TCP and CBR can be setup between mobilenodes using a traffic scenario generator script This traffic generator script is available under ns indep utils emu scen gen and is called cbrgen tcl It can be used to create CBR and TCP traffics connections between wireless mobilenodes In order to create a traffic connection file we need to define the type of traffic c
34. hier internal network components Tell nodes when the simulation ends mor ser t Of Si lt Swed am imer a Ssns at 150 0 Snode_ i reset Sag art 150 0001 steel Sins atc 150 0002 Yous WNS MIWING Sms halt ISOC StH iP Glooel me_ wicaceiccl close Stracefd At time 150 0s the simulation shall stop The nodes are reset at that time and the ns_ halt is called at 150 0002s a little later after resetting the nodes The procedure stop is called to flush out traces and close the trace file And finally the command to start the simulation putes Srat SmalacioN s Sina run Save the file simple wireless tcl In order to download a copy of the file click here Next run the simulation in the usual way type at prompt ns simple wireless tcl At the end of the simulation run trace output file simple tr is created As we have turned on the AgentTrace and RouterTrace we see DSDV routing messages and TCP pkts being received and sent by Router and Agent objects in node _0_ and _1_ Note that all wireless traces starts with WL in their first field See Chapter 15 of ns documentation for details on wireless trace We see TCP flow starting at 10 0s from node0 Initially both the nodes are far apart and thus TCP pkts are dropped by node as it cannot hear from node1 Around 81 0s the routing info begins to be exchanged between both the nodes and around 100 0s we see the first TCP pkt being received by the
35. ince it contains some components that you don t need anymore after you compiled ns and nam It s still good for first tests and you can always switch to the single package distribution later Note The all in one package only works on Unix systems You can download the package from the ns download page at UCB If you have any problems with your installation take a look at the installation problems page on their server If that also doesn t solve your problem you might want to ask the ns users mailing list After the installation is complete you should make sure that your path points to the ns allinone bin directory if you installed the ns allinone package where links to the ns and nam executables in the ns 2 and nam 1 directories can be found or if you built ns and nam from the pieces let your path point directly to the directories with the ns and nam executables On some systems you will also have to make sure that ns can find the library libotcl so If you installed the ns allinone package it should be in ns allinone otcl On Solaris systems you would have to add this path to the LD_LLIBRARY_PATH environment variable For help with other systems consult the installation problem page the ns users mailing list or your local Unix gurus A note concerning the ns allinone version 2 1b3 There is a bug in it which causes some problems on Solaris systems when nam trace generation is turned on You can either download ns allinon
36. ion The usage of movement pattern files and feeding of next hop info to God shall be shown in the example in the next sub section The procedure create god is defined in ns tcl mobility com tcl which allows only a single global instance of the God object to be created during a simulation In addition to the evaluation functionalities the God object is called internally by MAC objects in mobilenodes So even though we may not utilise God for evaluation purposes as in this example we still need to create God Next we create mobilenodes The node creation APIs have been revised and here we shall be using the new APIs to create mobilenodes IMPORTANT NOTE The new APIs are not available with ns2 1b5 release Download the daily snapshot version if the next release 2 1b6 upwards is not as yet available First we need to configure nodes before we can create them Node configuration API may consist of defining the type of addressing flat hierarchical etc the type of adhoc routing protocol Link Layer MAC layer IfQ etc The configuration API can be defined as follows parameter examples Sns_ node config addressingType flat or hierarchical or expanded adhocRouting DSDV or DSR or TORA llType ill macType Mac 802_11 propType Propagation TwoRayGround ifgqType Queue DropTail PriQueue ifqLen 50 phyType Phy WirelessPhy antType Antenna OmniAntenna
37. l simulation The nominal range is either provided as an argument to the programs or extracted from the header on the movement pattern file The path length information was used by the Monarch Project to analyze the path length optimality of ad hoc network routing protocols and so was printed out as part of the CMUTrace output for each packet Other uses that CMU found for the information e Characterizing the rate of topology change in a movement pattern e Identifying the frequency and size of partitions e Experimenting with the behavior of the routing protocols if the god information is used to provide them with perfect neighbor information at zero cost Thus at the end of the node movement file are listed information like number of destination unreachable total number of route and connectivity changes for mobilenodes and the same info for each mobilenode The revised more portable version of setdest files revised are setdest cc h ns rng cc h ns Makefile in should be available from the latest ns distribution If not you could download the daily snapshot version of ns from ns build page Previous section Back to the index VINT ns users isi edu
38. l110 Sms at 0 35 Selo start Sas ar 4 5 SClor0 stop The code above should look familiar to you by now The only difference to the last sections is that now we have to use the node array elements If you start the script you will see that the traffic takes the shortest path from node 0 to node 3 through nodes 1 and 2 as could be expected Now we add another interesting feature We let the link between node and 2 which is being used by the traffic go down for a second Sns rtmodel at 1 0 down n 1 n 2 ns rtmodel at 2 0 up n 1 n 2 It is probably not too hard to understand these two lines Now you can start the script again and you will see that between the seconds 1 0 and 2 0 the link will be down and all data that is sent from node 0 is lost ie Now I will show you how to use dynamic routing to solve that problem Add the following line at the beginning of your Tcl script after the simulator object has been created Sns rtproto DV Start the simulation again and you will see how at first a lot of small packets run through the network If you slow nam down enough to click on one of them you will see that they are rtProtoDV packets which are being used to exchange routing information between the nodes When the link goes down again at 1 0 seconds the routing will be updated and the traffic will be re routed through the nodes 6 5 and 4 Z Z ari You can download the full exa
39. lar to the one below after a few moments You can see the packets in the queue now and after a while you can even see how the packets are being dropped though at least on my system I guess it might be different in later or earlier releases only blue packets are being dropped But you can t really expect too much fairness from a simple DropTail queue So let s try to improve the queueing by using a SFQ stochastic fair queueing queue for the link from n2 to n3 Change the link definition for the link between n2 and n3 to the following line Sns duplex link n3 n2 1Mb 10ms SEG The queueing should be fair now The same amount of blue and red packets should be dropped You can download the full example here Previous section Next section Back to the index ns users ns users isi edu VI Network dynamics Previous section Next section Back to the index In this section I am going to show you an example for a dynamic network where the routing adjusts to a link failure On the way there I ll show you how you can keep a larger number of nodes in a Tcl array instead of giving each node its own name VI 1 Creating a larger topology I suggest you call the Tcl script for this example example3 tcl You can already insert the template from section IV 1 into the file As always the topology has to be created first though this time we take a different approach which you will find more comfortable when you wa
40. me programming skills you should be able to learn most of what you need for simple scenarios as you go along However I will try to provide some interesting links for the more ambitious users who are not willing or able to buy a Tcl book The Tcl8 0 Tk8 0 Manual is basically a collection of hypertext manual pages A draft for a Tcl Tk book is available in postscript format for personal use Only the first 94 pages are relevant for Tcl the rest of the book is about Tk and more complicated aspects of Tcl I also found a short OTcl Tutorial Another good starting point for looking for Tcl documentation is the Yahoo Tcl Tk category II 3 Documentation for C I d like to note that you don t need any C programming knowledge unless you want to add new functionality to ns Perhaps the best source for learning C is the book The C Programming Language by Bjarne Stroustrup If you don t want to buy a book you can take a look at this C tutorial lll The Basics Previous section Next section Back to the index II 1 Downloading Installing ns amp nam You can build ns either from the the various packages Tcl Tk otcl etc or you can download an all in one package I would recommend that you start with the all in one package especially if you re not entirely sure which packages are installed on your system and where exactly they are installed The disadvantage of the all in one distribution is the size s
41. most important functions are being explained Fast forward by 25 Step seconds Stop animation Flay animation Flay animation backwards y Quit nam Current animation time bee as i Time beter een two animation frames f ra _Change the Step parameter Rewind by 25 Step seconds a Zoomin __ oe Zoom cut Drag slider to a specific point in time Run auto layout f Attactye force for layout model Number of iterations for layout Repulsive force for layout model Previous section Next section Back to the index ns users ns users isi edu IV The first Tcl script Previous section Next section Back to the index In this section you are going to develop a Tcl script for ns which simulates a simple topology You are going to learn how to set up nodes and links how to send data from one node to another how to monitor a queue and how to start nam from your simulation script to visualize your simulation IV 1 How to start Now we are going to write a template that you can use for all of the first Tcl scripts You can write your Tcl scripts in any text editor like joe or emacs I suggest that you call this first example example1 tcl First of all you need to create a simulator object This is done with the command set ns new Simulator Now we open a file for writing that is going to be used for the nam trace data set nf open out nam w Sns namtrace all
42. mple here Previous section Next section Back to the index ns users ns users isi edu Vil A new protocol for ns Previous section Back to the index Next section In this section I will give you an example for a new protocol that could be implemented in ns You should probably become fairly familiar with ns before you try this yourself and some C knowledge is definitely necessary You should also read at least the chapters 3 1 3 3 from ns Notes and Documentation now renamed ns Manual to understand the interaction between Tcl and C The code in this section implements some sort of simple ping protocol inspired by the ping requestor in chapter 9 6 of the ns Notes and Documentation now renamed ns Manual but fairly different One node will be able to send a packet to another node which will return it immediately so that the round trip time can be calculated I understand that the code presented here might not be the best possible implementation and I am sure it can be improved though I hope it is easy to understand which is the main priority here However suggestions can be sent here VII 1 The header file In the new header file ping h we first have to declare the data structure for the new Ping packet header which is going to carry the relevant data struct ace olas echar ret double send_time Ie The char ret is going to be set to 0 if the packet is on its way from the sende
43. mulation stop time Note here that we use array opt instead of val simply to illustrate that this is no longer a global array variable and its scope is defined only in the test script set opt adhocRouting DSDV Ser GAE KED kiy cp file not used Ser OpE SiC 300 time to stop simulation We define the start times for TCP flows here set opt ftpl start LETO set opt ftp2 start LO O Also add the following line to define number of wired and base station nodes set num wired_nodes 2 set num_bs_nodes AL Now we move to the main part of the program For mixed simulations we need to use hierarchical routing in order to route packets between wireless and wired domains As explained in section 15 2 1 of ns Manual in ns the routing information for wired nodes are based on connectivity of the topology i e how are nodes connected to one another through Links This connectivity information is used to populate the forwarding tables in each wired node However wireless nodes have no concept of links Packets are routed in a wireless topology using their adhoc routing protocols which build forwarding tables by exchanging routing queries among its neighbours So inorder to exchange pkts among these wired and wireless nodes we use base stations which act as gateways between the two domains We seggregate wired and wireless nodes by placing them in different domains Domains and sub domains or clusters as they are called here are defined by mea
44. ns of hierarchical topology structure as shown below After line set ns new Simulator add the following lines Sns_ node config addressType hierarchical AddrParams set domain_num_ 2 number of domains lappend cluster_num 2 1 number of clusters in each domain AddrParams set cluster_num_ cluster_num lappend eilastlevel 11 4 number of nodes in each cluster AddrParams set nodes_num_ Seilastlevel for each domain In the above lines we first configure the node object to have addresstype as Hierarchical Next the topology hierarchy is defined Number of domains in this topology is 2 one for the wired nodes and one for the wireless Number of clusters in each of these domains is defined as 2 1 which indicates the first domain wired to have 2 clusters and the second wireless to have cluster The next line defines the number of nodes in each of these clusters which is 1 1 4 i e one node in each of the first 2 clusters in wired domain and 4 nodes in the cluster in the wireless domain So the topology is defined into a 3 level hierarchy see the topology figure above Next we setup tracing for the simulation Note here that for wired cum wireless simulation traces may be generated for both wired and wireless domains Both the traces are written into the same output file defined here as wireless2 out tr In order to differentiate wireless traces from wired ones all wireless traces begin with WL We also setup nam traces As menti
45. nt to create larger topologies The following code creates seven nodes and stores them in the array n wore see L Ok Sa lt 7 Famer af set n Si ns node You have certainly seen for loops in other programming languages before and I am sure you understand the structure at once Note that arrays just like other variables in Tcl don t have to be declared first Now we re going to connect the nodes to create a circular topology The following piece of code might look a bit more complicated at first cor eee i O Si lt 7 incr a Sns duplex link Sn S i Sn expr i 1 7 1Mb 10ms DropTail This for loop connects all nodes with the next node in the array with the exception of the last node which is being connected with the first node To accomplish that I used the modulo operator When you run the script now the topology might look a bit strange in nam at first but after you hit the re layout button it should look like the picture below VI 2 Link failure The next step is to send some data from node n 0 to node n 3 Create a UDP agent and attach it to node n 0 set udpO new Agent UDP Sns attach agent n 0 Sudp0 Create a CBR traffic source and attach it to udp0d set cbrO new Application Traffic CBR ScbrO set packetSize_ 500 ScbrO set interval_ 0 005 ScbrO attach agent Sudp0 set null0O new Agent Null Sns attach agent n 3 Smella Sns connect Sudp0O Snu
46. ntation for ns and related packages If you know any other sources or if any of the links have expired please send email to_ns users mailing list II 1 Documentation for ns amp nam The following documentation for ns and nam is available from the main ns web page at UCB ns Notes and Documentation now renamed the ns Manual could be called the main manual for ns and is available in Postscript format An HTML version currently without diagrams of nsN amp D now renamed ns Manual is available here A manual page for ns is included in the distribution in the ns directory There is a HTML ized version here but it might be out dated There is a ps version of the nam user manual which is available from the nam page You can also get an ASCII version from here You can also get slides from the second ns workshop from this page They don t really contain more information than the ns Notes and Documentation now renamed ns Manual document though it might be a bit easier to understand and use If you can t get ns to compile if it crashes or if you have any other similar problems take a look at the ns problems page before you ask on the mailing list If you have any general questions about ns or nam you can send them to the ns users mailing list If you re not sure if your question has been asked before check the Archive for the mailing list II 2 Documentation for Tcl Tcl is fairly simple and if you already have so
47. omain will be forwarded by mobilenodes towards their assigned base station Note that it is important for the base station node to be in the same domain as the wireless nodes This is so that all pkts originating from the wired domain and destined for a wireless node will reach the base station which then uses its adhoc routing protocol to route the pkt to its correct destination Thus in a mixed simulation involving wired and wireless nodes its necessary 1 to turn on hierarchical routing 2 to create separate domains for wired and wireless nodes There may be multiple wired and wireless domains to simulate multiple networks 3 to have one base station node in every wireless domain thru which the wireless nodes may communicate with nodes outside their domain Let us go step by step for this example to see how the hierarchy is created Here we have two domains domain 0 for wired and domain 1 for wireless The two wired nodes are placed in 2 separate clusters 0 and 1 thus their addresses look like 0 domain 0 0 cluster 0 0 only node and 0 same domain 0 1 cluster 1 0 again only node As for the wireless nodes they are in domain 1 we have defined one cluster 0 so all nodes are in this cluster Hence the addresses are Base station 1 second domain 1 0 cluster 0 0 first node in cluster WL node 1 1 0 1 second node in cluster WL node 2 1 0 2 third node WL node 3 1 0 3 fourth node We could have placed the two wired nod
48. on you might need in the existing documentation For this purpose I will also try to tell you where I found the information in this tutorial myself so you not only learn how to use ns but also how to use its documentation The web is probably the best medium for a tutorial like this because it s not only possible to add pictures or even animations for the examples but you can also directly download the examples if you don t have the time for typing them in yourself though I would suggest doing that at least for the first few examples I chose a frame oriented design for these pages since it makes them easier to navigate If you find that the left frame with the contents takes up too much room or if you just don t like frames you can switch to a frameless version Please understand that I can not give you a full reference manual for ns here or a full Tcl C tutorial and that in a simple tutorial like this I can not help you with special problems like installation problems There are better sources for that which I am going to list in Section H If you have any suggestions find any bugs or problems have any comments and also if you have any new well documented examples that could be added here please send email to ns users mailing list Next section Back to the index ns users ns users isi edu ns Tutorial Contents I Introduction II Finding Documentation o I 1 For ns amp nam o I 2 For Tcl o I 3 For C III The B
49. oned earlier nam traces for wireless nodes currently show node movements only set tracefd open wireless2 out tr w set namtrace open wireless2 out nam w Sns_ trace all Stracefd Sns_ namtrace all wireless Snamtrace Sopt x Sopt y Next we need to create the wired wireless and base station nodes Note here that for all node creations you have to pass the hierarchical address of the node So after line create god opt nn add the following lines for creating wired nodes Create wired nodes set temp 0 0 0 0 1 0 hierarchical addresses to be used for set i 0 i lt Snum_wired_nodes incr i set W i ns_ node lindex Stemp i In order to create base station node we need to configure the node structure as shown below This is part of the new node API which consists of first configuring and then creating nodes Refer to node API in chapterIX for details about the new node API Since base station nodes are gateways between wired and wireless domains they need to have wired routing mechanism turned on which is done by setting node config option wiredRouting ON After creating the base station node we reconfigure for wireless node and so turn wiredRouting OFF All other node config options used for base station remains the same for mobilenode Also the BS 0 node is assigned as the base station node for all the mobilenodes in the wireless domain so that all pkts originating from mobilenodes and destined outside the wireless d
50. onnection CBR or TCP the number of nodes and maximum number of connections to be setup between them a random seed and incase of CBR connections a rate whose inverse value is used to compute the interval time between the CBR pkts So the command line looks like the following ns cbrgen tcl type cbr tcp nn nodes seed seed mc connections rate rate The start times for the TCP CBR connections are randomly generated with a maximum value set at 180 0s Go through the tcl script cbrgen tcl for the details of the traffic generator implementation For example let us try to create a CBR connection file between 10 nodes having maximum of 8 connections with a seed value of 1 0 and a rate of 4 0 So at the prompt type ne Gorgen tEl ry93 Cor m L0 SCC Cul OM MC rare 40 gt Cor 10 regt From cbr 10 test file into which the output of the generator is redirected thus created one of the cbr connections looks like the following 2 connecting to 3 at time 82 557023746220864 set udp_ 0 new Agent UDP Sns_ attach agent node_ 2 Sudp_ 0 set null_ 0 new Agent Nul1 Sns_ attach agent node_ 3 S null_ 0 set cbr_ 0 new Application Traffic CBR SClom 0 see jackeicSawe 52 Sclox 0 sete incerval _ 0 25 Scbr_ 0 set random_ 1 Scbr_ 0 set maxpkts_ 10000 SiC basen 0 arccach agent Swcio 0 Sma COmmece Secho 0 Smiil 0 Sag aw 32 551023 746220364 Siclore 0 scart Thus a UDP connec
51. ose f2 Call xgraph to display the results exec xgraph out0 tr outl tr out2 tr geometry 800x400 amp exit 0 It not only closes the output files but also calls xgraph to display the results You may want to adapt the window size 800x400 to your screen size Now we can write the procedure which actually writes the data to the output files proc record f global sink siski sink2 fO fI f2 Get an instance of the simulator set ns Simulator instance Set the time after which the procedure should be called again set time 0 5 How many bytes have been received by the traffic sinks set bw0 sink0 set bytes_ set bwl sinkl set bytes_ set bw2 sink2 set bytes_ Get the current time set now ns now Calculate the bandwidth in MBit s and write it to the files puts f0 Snow expr Sbw0 Stime 8 1000000 puts f1 Snow expr Sbwl Stime 8 1000000 puts f2 Snow expr Sbw2 Stime 8 1000000 Reset the bytes_ values on the traffic sinks sink0 set bytes_ 0 sinkl set bytes_ 0 sink2 set bytes_ 0 Re schedule the procedure ns at expr Snow Stime record This procedure reads the number of bytes received from the three traffic sinks Then it calculates the bandwidth in MBit s and writes it to the three output files together with the current time before it resets the bytes_ values on the traffic sinks Then it re schedules itself VIIL3 Running the Simulation We can now schedule the following events sns at 0 0 record
52. pening file simple tr and call the procedure trace all as follows set tracefd open simple tr w Sins crace all SicieacSiccl Next create a topology object that keeps track of movements of mobilenodes within the topological boundary set topo new Topography We had earlier mentioned that mobilenodes move within a topology of 500mX500m We provide the topography object with x and y co ordinates of the boundary x 500 y 500 ropo loac rilarcoric 500 500 The topography is broken up into grids and the default value of grid resolution is 1 A diferent value can be passed as a third parameter to load_flatgrid above Next we create the object God as follows create god Sval nn Quoted from CMU document on god God General Operations Director is the object that is used to store global information about the state of the environment network or nodes that an omniscent observer would have but that should not be made known to any participant in the simulation Currently God object stores the total number of mobilenodes and a table of shortest number of hops required to reach from one node to another The next hop information is normally loaded into god object from movement pattern files before simulation begins since calculating this on the fly during simulation runs can be quite time consuming However in order to keep this example simple we avoid using movement pattern files and thus do not provide God with next hop informat
53. r to the node which is being pinged while it is going to be set to 1 on its way back The double send_time is a time stamp that is set on the packet when it is sent and which is later used to calculate the round trip time The following piece of code declares the class PingAgent as a subclass of the class Agent class PingAgent public Agent puoli es PingAgent EME COMMA ne EEnitsmcaaGic Aeons ehan conse Raron void recv Packet Handiler protected lot Or LAC In the following section I am going to present the C code which defines the constructor PingAgent and the functions command and recv which were redefined in this declaration The int off_ping_ will be used to access a packet s ping header Note that for variables with a local object scope usually a trailing _ is used You can download the full header file here I suggest you do that and take a quick look at it since the code that was presented here isn t totally complete VII 2 The C code First the linkage between the C code and Tcl code has to be defined It is not necessary that you fully understand this code but it would help you to read the chapters 3 1 3 3 in the ns Manual if you haven t done that yet to understand it static class PingHeaderClass public PacketHeaderClass POLIGI PingHeaderClass PacketHeaderClass PacketHeader Ping sizeof hdr_ping class_pinghdr static class PingClass public TclCl
54. reless network simulation In second subsection we will extend our example in subsection 1 to create a relatively more complex wireless scenario IMPORTANT This tutorial chapter uses new node APIs which are available as of ns 2 1b6 released January 18 2000 If you have an earlier version of ns you must upgrade to use these features IX 1 Creating a simple wireless scenario We are going to simulate a very simple 2 node wireless scenario The topology consists of two mobilenodes node_ 0 and node_ 1 The mobilenodes move about within an area whose boundary is defined in this example as 500mX500m The nodes start out initially at two opposite ends of the boundary Then they move towards each other in the first half of the simulation and again move away for the second half A TCP connection is setup between the two mobilenodes Packets are exchanged between the nodes as they come within hearing range of one another As they move away packets start getting dropped Just as with any other ns simulation we begin by creating a tcl script for the wireless simulation We will call this file simple wireless tcl If you want to download a copy of simple wireless tcl click here A mobilenode consists of network components like Link Layer LL Interface Queue IfQ MAC layer the wireless channel nodes transmit and receive signals from etc For details about these network components see section 1 of chapter 15 of ns Notes amp Documentation now r
55. s the movement of mobilenodes and traffic in the wired domain As mentioned earlier traffic flow for mobilenodes is not as yet supported in nam In trace file wireless2 out tr we see traces for both wired domain and wireless domain preceeding with WL for wireless At 160 0s a TCP connection is setup between _3_ which is node_ 0 and 0 which is W 0 Note that the node ids are created internally by the simulator and are assigned in the order of node creation At 170s another TCP connection is setup in the opposite direction from the wired to the wireless domain For details on CMUTraces see chapter 15 of ns documentation X 2 Running MobileIP in a simple wired cum wireless topology So far we have created a wired cum wireless topology and have exchanged pkts between a wired and wireless domain via a base station But a mobilenode may roam outside the domain of its basestation and should still continue to receive packets destined to it In other words it would be interesting to extend mobileIP support in the wired cum wireless scenario we created in section X 1 For this example we have the same wired domain consisting of 2 wired nodes WO and W1 We have 2 base station nodes and call them HomeAgent HA and ForeignAgent FA respectively The wired node W1 is connected to HA and FA as shown in the figure below There is a roaming mobilenode called MobileHost MH that moves between its home agent and foreign agents We will set up a TCP flow betwe
56. st at the beginning of the file It would look like the following piece of code SiNMEXC Gstic Sie exce_ Ping ofr oime set cl PacketHeader lindex Spair 0 The last change is a change that has to be applied to the Makefile You have to add the file ping o to the list of object files for ns In my version the last lines of the edited list look like this sessionhelper o delaymodel o srm ssm o srm topo o ping o LIB _DIR int Vec o LIB DIR int RVec o S LIB_DIR dmalloc_support o You should be able to recompile ns now simply by typing make in the ns directory If you are having any problems please email ns users VII 4 The Tcl code I m not going to present the full code for a Tcl example for the Ping agent now You can download a full example here But I will show you how to write the recv procedure that is called from the recv function in the C code when a ping echo packet is received INGISINE Palinve Lastro recy irom wicie f Sself instvar node_ puts node Snode_ id received ping answer from rrom with round Eripoeime omit ms This code should be fairly easy to understand The only new thing is that it accesses the member variable node_ of the base class Agent to get the node id for the node the agent is attached to Now you can try some experiments of your own A very simple experiment would be to not set the ret field in the packets to 1 You can probably guess wha
57. st number of hops required to reach from one node to an other The god object does not calculate this on the fly during simulation runs since it can be quite time consuming The information is loaded into the god object from the movement pattern file where lines of the form Sag ee BOYY 642 VsSeqe cl seic clist 23 46 2 are used to load the god object with the knowledge that the shortest path between node 23 and node 46 changed to 2 hops at time 899 642 The setdest program generates node movement files using the random waypoint algorithm These files already include the lines to load the god object with the appropriate information at the appropriate time Another program calcdest also available in ns indep utils emu scen gen setdest can be used to annotate movement pattern files generated by other means with the lines of god information calcdest makes several assumptions about the format of the lines in the input movement pattern file which will cause it to fail if the file is not formatted properly If calcdest rejects a movement pattern file you have created the easiest way to format it properly is often to load it into ad hockey and then save it out again If ad hockey can read your input correctly its output will be properly formatted for calcdest Both calcdest and setdest calculate the shortest number of hops between nodes based on the nominal radio range ignoring any effects that might be introduced by the propagation model in an actua
58. t send pkt 0 veturn TCL_OK so the calling function knows that the command has been processed RE CUTA INCIh Ol 2 T the command hasn t been processed by PingAgent command call the command function for the base class return Agent command argc argv The function recv defines the actions to be taken when a packet is received If the ret field is 0 a packet with the same value for the send_time field but with the ret field set to 1 has to be returned If ret is 1 a Tcl function which has to be defined by the user in Tcl is called and processed the event Important note to users of the ns version 2 1b2 Address instance NodeShift_ 1 has to be replaced with NODESHIFT to get the example to work under ns 2 1b2 void PingAgent recv Packet pkt Handler Access the IP header for the received packet in lie alia meko ache sj jakic Saceess ort o Ny Access the Ping header for the received packet lovelies otne aele lacks oiae jolie SeiGOOSss ice DLA p Is the ret field 0 i e the receiving node is being pinged if hdr gt ret 0 Send an echo First save the old packet s send_time double stime hdr gt send_time Discard the packet Packet free pkt Create a new packet Peele jolie eillilocjolic p Access the Ping header for the new packet hdr_ping hdrret hdr_ping pktret gt access off_ping_ Set the r
59. t is going to happen You can also try to add some code that allows the user to send ping packets with pa send node where pa is a ping agent and node a node without having to connect the agent pa with the ping agent on node first though that might be a little bit more complicated than it sounds at first You can also read the chapter 9 6 from the ns Manual to learn more about creating your own agents Good luck Previous section Back to the index Next section Marc Greis greis cs uni bonn de VIII Creating Output Files for Xgraph Previous section Next Section Back to the index One part of the ns allinone package is xgraph a plotting program which can be used to create graphic representations of simulation results In this section I will show you a simple way how you can create output files in your Tcl scripts which can be used as data sets for xgraph On the way there I will also show you how to use traffic generators A note The technique I present here is one of many possible ways to create output files suitable for xgraph If you think there is a technique which is superior in terms of understandablity which is what I aim for in this tutorial please let me know VIII 1 Topology and Traffic Sources First of all we create the following topology The following piece of code should look familiar to you by now if you read the first sections of this tutorial set n0 ns
60. tion is setup between node 2 and 3 Total UDP sources chosen between nodes 0 10 and total number of connections setup is indicated as 5 and 8 respectively at the end of the file cbr 10 test Similarly TCP connection files can be created using type as tcp An example would be Ms Corgens cel ToS teo an 25 seecl 0 0 ne 8 gt TCD 2I TESE A typical connection from tcp 25 test looks like the following 5 connecting to 7 at time 163 0399642433226 ser co Cl SiaS_ CieSeice Coimiseirsiom TCS Smode 5 WePSiinke Sinecla_ 7 Ol Stcp_ 1 set window_ 32 Stcp_ 1 set packetSize_ 512 sert cgo Seea_ il aircacin souicea TIE Sms ait IGS OS9VGAZAS S226 Yrgo 1 Srare XI 2 Creating node movements for wireless scenarios The node movement generator is available under ns indep utils cmu scen gen setdest directory and consists of setdest cc h and Makefile CMU s version of setdest used system dependent dev random and made calls to library functions initstate for generating random numbers That was replaced with a more portable random number generator class RNG available in ns In order to compile the revised setdest cc do the following 1 Go to ns directory and run configure you probably have done that already while building ns This creates a makefile for setdest 2 Go to indep utils emu scen gen setdest Run make which first creates a stand alone object file for ns rng cc the stand alone version doesnot use
61. we have created mobilenodes we need to give them a position to start with Provide initial X Y for now Z 0 co ordinates for node_ 0 and node_ 1 Smode 0 ser X 540 Sinocla 0 sete _ 2 0 nodem Oee eO Sinocle il ser X 390 0 Sinocle_ il see Wo Noor Sinoce il ser A_ 0 0 Node has a starting position of 5 2 while Node1 starts off at location 390 385 Next produce some node movements Node_ 1 starts to move towards node_ 0 Sis arc 50 0 Sinocle_ il seteclesie 25 0 20 0 15 0 Sms awr 10 0 WSnoce 0 sercesc 20 0 13 0 1 04 Node_ 1 then starts to move away from node_ 0 Sag ee 100 0 noce 1 seccesc 490 0 480 0 15 0 ns_ at 50 0 node_ 1 setdest 25 0 20 0 15 0 means at time 50 0s nodel starts to move towards the destination x 25 y 20 at a speed of 15m s This API is used to change direction and speed of movement of the mobilenodes Next setup traffic flow between the two nodes as follows TCP connections between node_ 0 and node_ 1 set tcp new Agent TCP Stcp set class_ 2 set sink new Agent TCPSink Sns_ attach agent S node_ 0 tcp Sns_ attach agent node_ 1 Ssink Sns_ connect Stcp S sink set ftp new Application FTP Shea bach agent STES Sms art 10 0 Site srat This sets up a TCP connection betwen the two nodes with a TCP source on node0 Then we need to define stop time when the simulation ends and tell mobilenodes to reset which actually resets t
62. y has a capacity of 1Mb s so obviously some packets are being discarded But which ones Both flows are black so the only way to find out what is happening to the packets is to monitor them in nam by clicking on them In the next two sections I m going to show you how to distinguish between different flows and how to see what is actually going on in the queue at the link from n2 to n3 V 3 Marking flows Add the following two lines to your CBR agent definitions SudpO set class_ Sudpl set class_ The parameter fid_ stands for flow id Now add the following piece of code to your Tcl script preferably at the beginning after the simulator object has been created since this is a part of the simulator setup PSREN Sinks CCl lor 1 Blue Lome Zee This code allows you to set different colors for each flow id Now you can start the script again and one flow should be blue while the other one is red Watch the link from node n2 to n3 for a while and you will notice that after some time the distribution between blue and red packets isn t too fair anymore at least that s the way it is on my system In the next section I ll show you how you can look inside this link s queue to find out what is going on there V 4 Monitoring a queue You only have to add the following line to your code to monitor the queue for the link from n2 to n3 Sns duplex link op n2 n3 queuePos 0 5 Start ns again and you will see a picture simi

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