Network Simulator(NS) Tutorial

1. Network Simulator(NS) Tutorial These slides can be downloaded from: http://networks.cs.ucdavis.edu/~lijian/289I/ Lijian@cs.ucdavis.edu

2. Agenda • What Is NS? • Elements of Simulation • NS Architecture • NS Internals • Summary Lijian@cs.ucdavis.edu

3. What is NS • Discrete event simulator • Packet-level • Protocol stack • Link layer and up for wired networks; • Physical layer and up for wireless networks • Wired and wireless(both local and satellite) Detour Lijian@cs.ucdavis.edu

4. History and Status • Now part of VINT(Virtual InterNet Testbed) project • Columbia NEST --> UCB REAL --> NS-1 --> NS-2 • Users from approximately • 600 institutes • 50 countries • Releases • Periodic releases (currently 2.1b9, April 2002) • Nightly snapshots (probably compiles and works, but “unstable”) • Available from: USC/ISI, UC Berkeley, UK mirror Lijian@cs.ucdavis.edu

5. Platforms • Most UNIX and UNIX-like systems • FreeBSD or *BSD • Linux • Sun Solaris • HP, SGI • Window 95/98/NT • Some work, some does not • (Emulation only for FreeBSD for now) Lijian@cs.ucdavis.edu

6. Functionality of NS • Wired world • Point-to-point link, LAN • Unicast/multicast routing • Transport • Application layer • Wireless • Mobile IP • Ad hoc routing • Tracing, visualization, various utilities Lijian@cs.ucdavis.edu

7. Visualization Tools • nam-1 (Network AniMator Version 1) • Packet-level animation • Well supported by ns • xgraph • Conversion from ns trace to xgraph format Lijian@cs.ucdavis.edu

8. Getting Started • NS official site: • http://www.isi.edu/nsnam/ns/ • A painless tutorial by Marc Greis: • http://www.isi.edu/nsnam/ns/tutorial/index.html • Another good tutorial from WPI • http://nile.wpi.edu/NS/ Lijian@cs.ucdavis.edu

9. Getting Help & Reference • Building NS • http://www.isi.edu/nsnam/ns/ns-build.html • NS user mailing list • http://mailman.isi.edu/mailman/listinfo/ns-users • NS manual • http://www.isi.edu/nsnam/ns/ns-documentation.html Lijian@cs.ucdavis.edu

10. Agenda • What Is NS? • Elements of Simulation • NS Architecture • NS Internals • Summary Lijian@cs.ucdavis.edu

11. Elements of Simulation • Create the event scheduler • [Turn on tracing] • Create network • Setup routing • [Insert errors] • Create traffic • Start simulation • Post-process trace Detour Lijian@cs.ucdavis.edu

12. Creating Event Scheduler • Create event scheduler • set ns [new Simulator] • Schedule events • $ns at <time> <event> • <event>: any legitimate ns/tcl commands • Start scheduler • $ns run Lijian@cs.ucdavis.edu

13. Tracing • Trace packets on all links • $ns trace-all [open test.out w] <event> <time> <from> <to> <pkt> <size> -- <fid> <src> <dst> <seq> <attr> + 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0 - 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0 r 1.00234 0 2 cbr 210 ------- 0 0.0 3.1 0 0 • Trace packets on all links in nam-1 format • $ns namtrace-all [open test.nam w] • Turn on tracing on specific links • $ns trace-queue $n0 $n1 • $ns namtrace-queue $n0 $n1 • Must appear immediately after creating scheduler Lijian@cs.ucdavis.edu

14. Creating Network • Nodes • set n0 [$ns node] • set n1 [$ns node] • Links and queuing • $ns duplex-link $n0 $n1 <bandwidth> <delay> <queue_type> • <queue_type>: DropTail, RED, CBQ, FQ, SFQ, DRR Lijian@cs.ucdavis.edu

15. Creating Network: LAN • LAN • $ns make-lan <node_list> <bandwidth> <delay> <ll_type> <ifq_type> <mac_type> <channel_type> • <ll_type>: LL • <ifq_type>: Queue/DropTail, • <mac_type>: MAC/802_3 • <channel_type>: Channel Lijian@cs.ucdavis.edu

16. Inserting Errors • Creating Error Module • set loss_module [new ErrorModel] • $loss_module set rate_ 0.01 • $loss_module unit pkt • $loss_module ranvar [new RandomVariable/Uniform] • $loss_module drop-target [new Agent/Null] • Inserting Error Module • $ns lossmodel $loss_module $n0 $n1 Lijian@cs.ucdavis.edu

17. Network Dynamics • Link failures • Hooks in routing module to reflect routing changes • Four models $ns rtmodel Trace <config_file> $n0 $n1 $ns rtmodel Exponential {<params>} $n0 $n1 $ns rtmodel Deterministic {<params>} $n0 $n1 $ns rtmodel-at <time> up|down $n0 $n1 • Parameter list [<start>] <up_interval> <down_interval> [<finish>] Lijian@cs.ucdavis.edu

18. Setup Routing • Unicast • $ns rtproto <type> • <type>: Static, Session, DV, cost, multi-path • Multicast • $ns multicast (right after [new Simulator]) • $ns mrtproto <type> • <type>: CtrMcast, DM, ST, BST Lijian@cs.ucdavis.edu

19. Creating Connection: UDP or TCP • UDP • set udp [new Agent/UDP] • set null [new Agent/Null] • $ns attach-agent $n0 $udp • $ns attach-agent $n1 $null • $ns connect $udp $null • TCP • set tcp [new Agent/TCP] • set tcpsink [new Agent/TCPSink] • $ns attach-agent $n0 $tcp • $ns attach-agent $n1 $tcpsink • $ns connect $tcp $tcpsink Lijian@cs.ucdavis.edu

20. Creating Traffic: On Top of UDP • CBR • set src [new Application/Traffic/CBR] • Exponential or Pareto on-off • set src [new Application/Traffic/Exponential] • set src [new Application/Traffic/Pareto] Lijian@cs.ucdavis.edu

21. Creating Traffic: On Top of TCP • FTP • set ftp [new Application/FTP] • $ftp attach-agent $tcp • Telnet • set telnet [new Application/Telnet] • $telnet attach-agent $tcp Lijian@cs.ucdavis.edu

22. Creating Traffic: Trace Driven • Trace driven • set tfile [new Tracefile] • $tfile filename <file> • set src [new Application/Traffic/Trace] • $src attach-tracefile $tfile • <file>: • Binary format (native!) • inter-packet time (msec) and packet size (byte) Lijian@cs.ucdavis.edu

23. Application-Level Simulation • Features • Build on top of existing transport protocol • Transmit user data, e.g., HTTP header • Two different solutions • TCP: Application/TcpApp • UDP: Agent/Message Lijian@cs.ucdavis.edu

24. Agenda • What Is NS? • Elements of Simulation • NS Architecture • NS Internals • Summary Detour ends. Lijian@cs.ucdavis.edu

25. NS Architecture • Object-oriented (C++, OTcl) • Scalability + Extensibility • Control/”data” separation • Split C++/OTcl object • Modular approach • Fine-grained object composition Detour ends. Lijian@cs.ucdavis.edu

26. C++/OTcl Split Objects Pure OTcl objects Pure C++ objects 100K 70K C++ OTcl C++/OTcl split objects NS Lijian@cs.ucdavis.edu

27. C++/OTcl Linkage Lijian@cs.ucdavis.edu

28. TclObject: Hierarchy and Shadowing C++ class hierarchy OTcl class hierarchy TclObject TclObject Agent Agent TcpAgent Agent/TCP *tcp _o123 Agent/TCP OTcl shadow object Agent/TCP C++ object Lijian@cs.ucdavis.edu

29. The Merit of OTcl • Smoothly adjust the granularity of scripting to balance extensibility and performance • With complete compatibility with existing simulation scripts Program size, complexity low high OTcl C/C++ split objects Lijian@cs.ucdavis.edu

30. Scalability vs Flexibility • It’s tempting to write all-OTcl simulation • Benefit: quick prototyping • Cost: memory + runtime • Solution • Control the granularity of your split object by migrating methods from OTcl to C++ Lijian@cs.ucdavis.edu

31. Object Granularity Tips • Functionality • Per-packet processing  C++ • Hooks, frequently changing code  OTcl • Data management • Complex/large data structure  C++ • One-time configuration variables  OTcl Lijian@cs.ucdavis.edu

32. Agenda • What Is NS? • Elements of Simulation • NS Architecture • NS Internals • Summary Lijian@cs.ucdavis.edu

33. NS Internals • Discrete event scheduler • Network topology • Routing • Transport • Packet flow • Packet format • Application Lijian@cs.ucdavis.edu

34. head_ -> handler_ -> handle() reschedule insert time_, uid_, next_, handler_ Discrete Event Scheduler • Three types of schedulers • List: simple linked list, order-preserving, O(N) • Heap: O(logN) • Calendar: hash-based, fastest, O(1) time_, uid_, next_, handler_ head_ -> Lijian@cs.ucdavis.edu

35. n0 n1 Port Classifier Multicast Node dmux_ Addr Classifier classifier_ Node entry Node entry dmux_ entry_ entry_ Multicast Classifier classifier_ multiclassifier_ Network Topology: Node Unicast Node Lijian@cs.ucdavis.edu

36. n0 n1 duplex link n1 entry_ head_ enqT_ queue_ deqT_ link_ ttl_ drophead_ drpT_ tracing simplex link Network Topology: Link Lijian@cs.ucdavis.edu

37. n0 n1 Port Classifier Addr Classifier n1 entry_ 0 Node entry head_ dmux_ enqT_ queue_ deqT_ link_ ttl_ 1 entry_ classifier_ drophead_ drpT_ Routing Lijian@cs.ucdavis.edu

38. n0 n1 Port Classifier Port Classifier Addr Classifier Addr Classifier 0 1 dmux_ dmux_ 0 1 entry_ entry_ classifier_ classifier_ Link n1-n0 Routing (con’t) Link n0-n1 Lijian@cs.ucdavis.edu

39. dst_=0.0 dst_=1.0 Agent/TCP Agent/TCPSink agents_ agents_ 1 0 0 1 Transport n0 n1 Port Classifier Port Classifier Addr Classifier Addr Classifier 0 0 dmux_ dmux_ Link n0-n1 entry_ entry_ classifier_ classifier_ Link n1-n0 Lijian@cs.ucdavis.edu

40. Application/FTP dst_=0.0 dst_=1.0 0 1 1 0 Application: Traffic Generator n0 n1 Port Classifier Port Classifier Agent/TCPSink Addr Classifier Addr Classifier Agent/TCP 0 0 agents_ agents_ dmux_ dmux_ Link n0-n1 entry_ entry_ classifier_ classifier_ Link n1-n0 Lijian@cs.ucdavis.edu

41. dst_=0.0 dst_=1.0 0 1 1 0 Plumbing: Packet Flow n0 n1 Application/FTP Port Classifier Port Classifier Agent/TCPSink Addr Classifier Addr Classifier Agent/TCP 0 0 Link n0-n1 entry_ entry_ Link n1-n0 Lijian@cs.ucdavis.edu

42. ts_ cmn header ptype_ ip header uid_ tcp header size_ rtp header iface_ trace header ... Packet Format header data Lijian@cs.ucdavis.edu

43. Abstract the Real Wireless World • Packet headers • Mobile node • Wireless channel • Forwarding and routing • Visualization Lijian@cs.ucdavis.edu

44. ts_ cmn header ptype_ IP header uid_ ...... size_ LL iface_ MAC 802_11 ARP ...... Wireless Packet Format header data Wireless headers Lijian@cs.ucdavis.edu

45. Mobile Node Abstraction • Location • Coordinates (x,y,z) • Movement • Speed, direction, starting/ending location, time ... Lijian@cs.ucdavis.edu

46. Classifier: Forwarding Agent: Protocol Entity Node Entry LL: Link layer object IFQ: Interface queue MAC: Mac object PHY: Net interface Portrait of A Mobile Node port classifier Node protocol agent 255 routing agent addr classifier defaulttarget_ ARP LL LL LL IFQ IFQ MAC MAC Propagation and antenna models PHY PHY MobileNode CHANNEL Lijian@cs.ucdavis.edu

47. Wireless Channel • Duplicate packets to all mobile nodes attached to the channel except the sender • It is the receiver’s responsibility to decide if it will accept the packet • Collision is handled at individual receiver • O(N2) messages  grid keeper Lijian@cs.ucdavis.edu

48. Agenda • What Is NS? • Elements of Simulation • NS Architecture • NS Internals • Summary Lijian@cs.ucdavis.edu

49. Summary • What can we do with NS? • Architectural overview of NS • split C++/OTcl Object • Inside NS • node, link, routing, tcp, app, wireless extension • how it works Lijian@cs.ucdavis.edu

50. References • http://www.isi.edu/nsnam/dist/ns-workshop00/ • http://www.isi.edu/nsnam/ns/ Lijian@cs.ucdavis.edu