Introduction to Omnet++

Transcription

1 Introduction to Omnet++ Paolo Giaccone TLC Network Group - Politecnico di Torino 1 Copyright Quest opera è protetta dalla licenza Creative Commons NoDerivs-NonCommercial. Per vedere una copia di questa licenza, consultare: oppure inviare una lettera a: Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. This work is licensed under the Creative Commons NoDerivs-NonCommercial License. To view a copy of this license, visit: or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA TLC Network Group - Politecnico di Torino 2 1

2 What is OMNeT++? object-oriented modular discrete event network simulator general purpose - protocol design - queueing systems - distributed hardware design - software systems - others... (air traffic, bus traffic) What is OMNeT++? open source, freely available ( - main core developed at Technical University of Budapest - well documented - OS support Linux - fully supported :-) Windows - 4.X version provides C++ compiler through MinGW (Minimalist GNU compilers for Windows) - commercial version available ( 2

3 OMNeT++ libraries very large catalog ( models/catalog) TCP/IP networks, 802.* MAC, MPLS, OSPF wireless mobile, vehicular networks wireless sensor and body area networks LTE networks CAN networks, satellite networks Infiniband, fiberchannel, storage area networks How does OMNeT++ work? based on the interaction among hierarchically nested modules - communication among modules through message passing - kind of glue for C++ modules interacting with messages and not through calling direct methods C++ knowledge is not mandatory but helpful C knowledge is mandatory 3

4 Model components modules /compound modules C++ file for each simple module ned file for the topology (compound modules and connections) Methods for simple module n method called during the simulation n handle_message() n main method to design the module behaviour n describe how to react when a message is received n n message can arrive n from another model n from itself (self-message) messages travel across connections TLC Network Group - Politecnico di Torino 8 4

5 Methods for simple module n methods called at the beginning of the simulation n constructor n called when the module is created, during setup process n useful to allocate data structures n initialize() n called after all the modules have been created n useful to initialize data structures and statistical variables TLC Network Group - Politecnico di Torino 9 Methods for simple module n methods called at the end of the simulation n finish() n called at the end a normally terminated simulation n useful to record statistics n all the other modules are still active n destructor n always called at the end of a simulation n useful to deallocate data structures TLC Network Group - Politecnico di Torino 10 5

6 Connections defined by data-rate, propagation delay and biterror-rate usually, in ned file output-gate -> input-gate (unidirectional) Messages may contain any complex data structure managed directly by module methods - send(message, out-gate) - senddelayed(message, delay, out-gate) - senddirect(message, targetmodule, in-gate) - scheduleat(time,message) self-message useful to schedule future events cancelevent(message) to remove the event from the FES 6

7 Simulation modeling process NED language (*.ned) to describe the modules topology - connections among modules - compound modules - modules parameters C++ code (*.cc, *.h) to describe the module behavior simulation configurations (omnetpp.ini) How to compile and run opp_makemake f! make! TLC Network Group - Politecnico di Torino 14 7

8 Single FIFO queue gen: Generator out in queue: Queue out in sink: Sink topology connections - gen.out --> queue.in - queue.out --> sink.in network MM1 Single FIFO queue gen: Generator queue: Queue sink: Sink parameters - generator: interarrivaltime [sec] - queue: - sink servicetime [sec] network MM1 8

9 Generator use a single message to schedule a new departure - sendmsgevent handlemessage(msg) - create a new packet pkt - send pkt to the output gate - compute the new departure-time - schedule sendmsgevent at departure-time - send self-message through scheduleat() do nothing - delete the packet - compute statistics Sink 9

10 Queue two messages to manage - endserviceevent - new packet arriving handlemessage(msg) if msg is endserviceevent, then dequeue and send the pkt to out-gate if another pkt is available in the buffer, then start a new service if msg is a packet, then enqueue the pkt if server is idle, then start a new service Recording simulation results final statistics (output scalars) void Sink::finish() { recordscalar("totarrivedpackets", num_packets); } sampled statistics (output vectors) void Sink::handleMessage(cMessage *msg) { simtime_t delay = simtime() - msg->creationtime(); delayvector.record(delay); delete msg; } 10

11 Simulation class library modules, gates, connections parameters messages - send, receive - scheduling, canceling of events container classes (queues, arrays) data collection classes Simulation class library data random generators - based on Mersenne Twister: period - many distributions available statistics (average, std.dev.) and distribution estimation classes (histograms, quantiles etc.) transient detection and result accuracy detection classes routing support for networks 11

12 Advanced features IDE graphical editor to code, debug and visually program the topology parallel distributed simulation - multiple replications - each module can run on a different processor GUI (Graphical User Interface) can be disabled activity() process style - wait for an incoming message (event) at any point of the code, or suspend the execution for some time Advanced features ad-hoc support for Finite State Machine FSM direct method calls among modules dynamic module creation object ownership management message encapsulation debug - logging information for just subsets of modules - watches, snapshots prompt for user input and inspect variables in GUI 12