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OMNeT ++. Outline. Introduction Overview The NED Language Simple Modules. What Is OMNeT ++?. Object-oriented modular discrete event network simulation framework modeling of wired and wireless communication networks protocol modeling modeling of queueing networks - PowerPoint PPT Presentation
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OMNET++
Outline• Introduction• Overview• The NED Language• Simple Modules
What Is OMNeT++?• Object-oriented modular discrete event network simulation
framework• modeling of wired and wireless communication networks• protocol modeling• modeling of queueing networks• modeling of multiprocessors and other distributed hardware
systems• validating of hardware architectures• evaluating performance aspects of complex software systems
What Is OMNeT++?• Object-oriented modular discrete event network simulation
framework
• Components (modules) are programmed in C++• Assembled into larger components and models using a
high-level language (NED)
Modeling Concepts
Connection• Spanning hierarchy levels are not permitted• Propagation delay, data rate and bit error rate, can be assigned
Gates• Input and output interfaces
Main features• Hierarchical Modules
• Top level module is the system module• Depth of module nesting is unlimited• Model structure is described in OMNeT++'s NED language• User implements the simple modules in C++, using the OMNeT++
simulation class library
• Module Types• Both simple and compound modules are instances of module types
Main features• Messages
• Modules communicate by exchanging messages• Frames or packets in a computer network• Jobs or customers in a queuing network
• Gates• Input and output interfaces of modules• messages are sent out through output gates and arrive through
input gates
• Links (connection)• Created within a single level of the module hierarchy
Main features• Modeling of Packet Transmissions
• Data rate, propagation delay, bit error rate and packet error rate
• Parameters• Can be assigned in either the NED files or the configuration file
omnetpp.ini• Used to customize simple module behavior, and to parameterize
the model topology
• Topology Description Method• User defines the structure of the model in NED language
descriptions
The NED Language• A communication network
Defines a network//Net6.ned
network Network
{
submodules:
node1: Node;
node2: Node;
node3: Node;
...
connections:
node1.port++ <--> {datarate=100Mbps;} <--> node2.port++;
node2.port++ <--> {datarate=100Mbps;} <--> node4.port++;
node4.port++ <--> {datarate=100Mbps;} <--> node6.port++;
...
}
//omnetpp.ini
[General]
network = Network
new gate
Introducing a Channelnetwork Network
{
types:
channel C extends ned.DatarateChannel {
datarate = 100Mbps;
}
submodules:
node1: Node;
node2: Node;
node3: Node;
...
connections:
node1.port++ <--> C <--> node2.port++;
node2.port++ <--> C <--> node4.port++;
node4.port++ <--> C <--> node6.port++;
...
}
The App, Routing, and Queue Simple Modules
simple App
{
parameters:
int destAddress;
...
@display("i=block/browser");
gates:
input in;
output out;
}
simple Routing
{
...
}
simple Queue
{
...
}
sending and receiving application packets
App.ned, Routing.ned and Queue.ned
The Node Compound Modulemodule Node
{
parameters:
int address;
@display("i=misc/node_vs,gold");
gates:
inout port[];
submodules:
app: App;
routing: Routing;
queue[sizeof(port)]: Queue;
connections:
routing.localOut --> app.in;
routing.localIn <-- app.out;
for i=0..sizeof(port)-1 {
routing.out[i] --> queue[i].in;
routing.in[i] <-- queue[i].out;
queue[i].line <--> port[i];
}
}
size will be determined implicitly by the number of neighboursbidirectional connections
Simple Modules• Simple modules are programmed in C++, using the
OMNeT++ class library• Discrete Event Simulation
• start of a packet transmission• end of a packet transmission• expiry of a retransmission timeout
initialize -- this includes building the model and inserting initial events to FES(Future Event Set)
while (FES not empty and simulation not yet complete){ retrieve first event from FES t:= timestamp of this event process event (processing may insert new events in FES or delete existing ones)}finish simulation (write statistical results, etc.)
Components, Simple Modules, Channels
Defining Simple Module Types// file: HelloModule.cc
#include <omnetpp.h>
class HelloModule : public cSimpleModule
{
protected:
virtual void initialize();
virtual void handleMessage(cMessage *msg);
};
// register module class with `\opp`
Define_Module(HelloModule);
void HelloModule::initialize()
{
ev << "Hello World!\n";
}
void HelloModule::handleMessage(cMessage *msg)
{
delete msg; // just discard everything we receive
}
called for every message that arrives at the module
// file: HelloModule.nedsimple HelloModule{ gates: input in;}
handleMessage()• send() family of functions
• to send messages to other modules
• scheduleAt()• to schedule an event (the module “sends a message to itself”)
• cancelEvent()• to delete an event scheduled with scheduleAt()
• Cannot use the receive() and wait() functions
Protocol Modelsclass FooProtocol : public cSimpleModule
{
protected:
// state variables
// ...
virtual void processMsgFromHigherLayer(cMessage *packet);
virtual void processMsgFromLowerLayer(FooPacket *packet);
virtual void processTimer(cMessage *timer);
virtual void initialize();
virtual void handleMessage(cMessage *msg);
};
// ...
void FooProtocol::handleMessage(cMessage *msg)
{
if (msg->isSelfMessage())
processTimer(msg);
else if (msg->arrivedOn("fromNetw"))
processMsgFromLowerLayer(check_and_cast<FooPacket *>(msg));
else
processMsgFromHigherLayer(msg);
}
activity()• receive()
• to receive messages (events)
• wait()• to suspend execution for some time (model time)
• send() family of functions• to send messages to other modules
• scheduleAt()• to schedule an event (the module “sends a message to itself”)
• cancelEvent()• to delete an event scheduled with scheduleAt()
• end()• to finish execution of this module (same as exiting the activity()
function)
activity()
void Sink::activity()
{
while(true)
{
msg = receive();
delete msg;
}
}
