Tài liệu NS-2 Tutorial pdf

NS-2 Tutorial Motivation What’s NS-2 • Network simulator – Discrete event simulator • It covers multiple layers – Application layer, transport layer, network layer and link layer. • Supports the simulation of – intserv/diffserv, Multicast, Transport, Applications, Wireless (fixed, mobile, satellite) • Packet level Model world as Model world as events events – – simulator has list of events ordered by simulation time simulator has list of events ordered by simulation time – – process: take next one, run it, until done process: take next one, run it, until done – – each event happens in an instant of each event happens in an instant of virtual (simulated) virtual (simulated) time time , but takes an arbitrary amount of , but takes an arbitrary amount of real real time time NS uses simple model NS uses simple model : single thread of control => : single thread of control => no locking or race conditions to worry about (very no locking or race conditions to worry about (very easy) easy) Discrete Event Simulation Discrete Event Simulation History and Status • REAL variant (1989)DARPA (LBL, Xerox PARC, UCB, and USC/ISI) (1995) • Currently; DARPA; NSF; collaboration with researchers: ACIRI, UCB Daedelus, CMU, Sun Microsystems, NORTEL, Cisco • ns-1 • ns-2 – 100K lines of C++ – 70K lines of OTcl – 30K lines of test suite – 20K lines of documentation • Current version is 2.28 ns-2 Programming Languages • NS-2 is an object oriented simulator, written in NS-2 is an object oriented simulator, written in C++ C++ , , with an with an OTcl OTcl (Object Tool Command Language) (Object Tool Command Language) interpreter as a front-end. interpreter as a front-end. • Back-end C++ – Defining new agents, protocols and framework. – Manipulations at the byte/bit levels. – if you have to change the behaviour of an existing C++ class in if you have to change the behaviour of an existing C++ class in ways that weren't anticipated ways that weren't anticipated • Front-end Otcl Topologies, scenarios, simulations, … – Script language (easy topology modifications) – if you can do what you want by manipulating existing C++ if you can do what you want by manipulating existing C++ objects objects Why Two Languages • Simulator had two distinct requirements Simulator had two distinct requirements – Detailed simulation of Protocol(Run-time speed) Detailed simulation of Protocol(Run-time speed) – Varying parameters or configuration(Change model & Varying parameters or configuration(Change model & rerun) rerun) • C++ is fast to run but slower to change C++ is fast to run but slower to change • Otcl runs much slower but can be changed Otcl runs much slower but can be changed quickly quickly OTcl and C++: The Duality C++ OTcl Pure C++ objects Pure OTcl objects C++/OTcl split objects ns Split Object: Object created in Otcl has a corresponding object in C++. ns Directory Structure TK8.0 OTcl tclclTcl8.0 ns-2 nam-1 tcl ex test lib examples validation tests C++ code OTcl code ns-allinone mcast Network Topology: Node Network Topology: Node n0 n1 Addr Classifier Port Classifier classifier_ dmux_ entry_ Node entry Unicast Node Multicast Classifier classifier_ dmux_ entry_ Node entry Multicast Node multiclassifier_ Classifier : Address, Multicast, Multipath, Hash Classifier : Address, Multicast, Multipath, Hash [...]... n1-n0 1 0 0 dst_=0.0 Agent/TCPSink Running NS-2 Program Resources • http://www.isi.edu/nsnam/ns • Tcl (Tool Command Language) – http://dev.scriptics.com/scripting • OTcl (MIT Object Tcl) – ~otcl/doc /tutorial. html (in distribution) • ns manual – Included in distribution: ~ns/doc – http://www.isi.edu/nsnam/ns/nsdocumentation.html Outline • • • • • What’s NS-2 NS-2 Structures TCL(Tool Command Language) . NS-2 Tutorial Motivation What’s NS-2 • Network simulator – Discrete event simulator • It covers. Cisco • ns-1 • ns-2 – 100K lines of C++ – 70K lines of OTcl – 30K lines of test suite – 20K lines of documentation • Current version is 2.28 ns-2 Programming