n groups of 1,2 or 3 people n if seats are available, also 1 person per group is also fine n individual written report discussed during the oral exam

Transcription

1 Copyright Omnet++ laboratories Paolo Giaccone 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 1 TLC Network Group - Politecnico di Torino 2 Lab organization l every Friday 14:30-17:30 l LAIB 2B (14/11, 21/11), LAIB 5D (28/11, 5/12, 12/12, 19/12, 9/1) l based on VDI (Virtual Desktop Virtualization) l l you access a Virtual Machine (VM) running in Polito datacenter you can start your VM anytime from any LAIB PC l not running from outside Politecnico Lab organization n groups of 1,2 or 3 people n if seats are available, also 1 person per group is also fine n individual written report discussed during the oral exam n mandatory writing the report (one for each group) to pass the exam n not mandatory attend the laboratory n plagiarism is forbidden and punished n discussion and interaction among students are welcome TLC Network Group - Politecnico di Torino 4 M/M/1 Lab #2 n Omnet++ implementation n templates n dummy.ned n dummy.cc TLC Network Group - Politecnico di Torino 5 TLC Network Group - Politecnico di Torino 6 1

2 dummy.ned dummy.cc simple Dummy { parameters: gates: input in; output out; network DummyNet { submodules: node1: Dummy; node2: Dummy; connections: node1.out --> node2.in; node2.out --> node1.in; TLC Network Group - Politecnico di Torino 7 #include <string.h> #include <omnetpp.h> class Dummy : public csimplemodule { private: // local variable public: // constructor Dummy(); // constructor virtual~ Dummy(); // destructor protected: virtual void initialize(); virtual void finish(); virtual void handlemessage(cmessage *msg); ; Define_Module(Dummy); TLC Network Group - Politecnico di Torino 8 dummy.cc Statistical collections Dummy::Dummy() { // init all msgs to NULL Dummy::~Dummy() { // delete messages with cancelanddelete() void Dummy::initialize() { // Initialize variables. void Dummy::finish() { // finish void Dummy::handleMessage(cMessage *msg) { // main function to code n Two approaches n signal mechanism, using declared statistics n not covered here n more flexible n using the simulation library n data collection n to get some statistical meaurement n e.g., average, std_dev n data sampling n to get the time evolution of a quantity TLC Network Group - Politecnico di Torino 9 TLC Network Group - Politecnico di Torino 10 Data collection Data sampling cstddev stat("stat"); for (int i=0; i<10; i++) stat.collect( normal(0,1) ); long numsamples = stat.getcount(); double smallest = stat.getmin(), largest = stat.getmax(); double mean = stat.getmean(), standarddeviation = stat.getstddev(), variance = stat.getvariance(); TLC Network Group - Politecnico di Torino 11 n coutvector class Sink : public csimplemodule { protected: coutvector endtoenddelayvec; ; void Sink::initialize() { endtoenddelayvec.setname("end-to-end Delay"); void Sink::handleMessage(cMessage *msg) { simtime_t eed = simtime()-msg->getcreationtime(); endtoenddelayvec.record(eed); delete msg; TLC Network Group - Politecnico di Torino 12 2

3 Statistical results n Available under results/ n Accessible through n scavetool scalar n scavetool vector Lab #3 TLC Network Group - Politecnico di Torino 13 TLC Network Group - Politecnico di Torino 14 Packets n cpacket extends cmessage class n support for TLC network packets n packet length n transmission time on a channel with a datarate n packet error on a channel with error probability n encapsulation (recursive) TLC Network Group - Politecnico di Torino 15 Creation of a packet void Generator::handleMessage(cMessage *msg) { cpacket *pkt; simtime_t departure_time; // create new packet pkt = new cpacket("packet"); // set its size pkt->setbytelength((long)par("pktsizebytes")); // sent to the output send(pkt,"out"); // compute the new departure time departure_time=simtime()+par("interarrivaltime"); // schedule the new packet generation scheduleat(departure_time, sendmsgevent); TLC Network Group - Politecnico di Torino 16 Channel with datarate n in ned file: network Ethernet { connections: mod1.out --> {datarate=100mbps;delay=1us; --> mod2.in; Channel offered load n arrival rate r [s -1 ] n average interarrival time T [s] n average pkt size P [bit] n datarate v [bit/s] n offered load= rp/v = P/(vT) n in [0,1] to be admissible TLC Network Group - Politecnico di Torino 17 TLC Network Group - Politecnico di Torino 18 3

4 Transmission model n transmission and propagation delays n Channel with datarate gettransmissionfinishtime() of cchannel class n for transmission channels, returns the simulation time the sender gate will finish transmitting n in handle_message() TLC Network Group - Politecnico di Torino 19 // declarations cchannel *txchannel=gate("out )-> gettransmissionchannel(); simtime_t txfinishtime; send(msg, out ); // compute the end of transmission of the current pkt txfinishtime = txchannel->gettransmissionfinishtime(); // evaluate the transmission delay (only if needed) transmission delay = txfinishtime-simtime() TLC Network Group - Politecnico di Torino 20 Transmitting a packet n in handlemessage if msg is end-of-tx event if another packet is available in the queue remove the packet from tx queue send packet schedule end-of-tx event at txfinishtime if msg is a packet if the channel is free (i.e., end-of-tx not scheduled) send packet schedule end-of-tx event at txfinishtime else store the pkt in the tx queue Trasmitting a packet n note that in the previous code, the intransmission packet is not (anymore) in the queue n it possible to modify the code to keep the packet inside the queue until the packet is completely transmitted TLC Network Group - Politecnico di Torino 21 TLC Network Group - Politecnico di Torino 22 Message casting n n dynamic_cast allows to adapt a pointer to the derived/base class cpacket is a derived class from cmessage void Sink::handleMessage(cMessage *msg) { // msg->getbytelength() NOT VALID cpacket *pkt; pkt=check_and_cast<cpacket *>(msg); // equivalent (but safer!) to pkt=(cpacket *)msg; // now you can use for the same received packet EV << "Bytes "<<pkt->getbytelength()<<endl; EV << Creation time <<msg->getcreationtime()<<endl; Lab #4 TLC Network Group - Politecnico di Torino 23 TLC Network Group - Politecnico di Torino 24 4

5 Packet scheduler n pkt is enqueued based on the arrival gate n scheduling decision n Round Robin n Strict Priority Arrival gate of a msg n ArrivedOn(gatename) method of cmessage to understand if the msg arrived from a specific gate void MyModule::handleMessage(cMessage *msg) { if (msg->arrivedon( in1 )) { // do something // e.g. store into the correct queue queue1.insert(msg); TLC Network Group - Politecnico di Torino 25 TLC Network Group - Politecnico di Torino 26 Scheduling decision SP Scheduler if msg is end-of-tx event q=scheduler() // choose the tx-queue to serve // q=0 -> all tx-queues are empty // q=1 -> serve tx-queue1 // q=2 -> serve tx-queue2 if q>=1 // if a non-empty queue was chosen remove the packet from tx-queue q send packet schedule end-of-tx event at txfinishtime if msg is a packet if end-of-tx not scheduled (i.e., free channel) send packet schedule end-of-tx event at txfinishtime else store the pkt into the proper tx-queue // high priority to tx-queue1 int scheduler() if tx-queue1 is not empty return 1 else if tx-queue2 is not empty return 2 else // both queues are empty return 0 TLC Network Group - Politecnico di Torino 27 TLC Network Group - Politecnico di Torino 28 RR Scheduler Personalized packet format last_queue_served is a private variable of the class int scheduler() if (last_served_queue==1) if (tx-queue2 is not empty) last_served_queue=2 return 2 else if (tx-queue1 is not empty) return 1 else return 0 else // last_served_queue==2 if (tx-queue1 is not empty) last_served_queue=1 return 1 else if (tx-queue2 is not empty) return 2 else return 0 TLC Network Group - Politecnico di Torino 29 n create a new file MyPacket.msg packet MyPacket { int sourceid; ; n pre-compile with opp_makemake f n creates MyPacket_m.h and MyPacket_m.cc n now, a new derived class from cpacket is available with name MyPacket n new available methods declared in MyPacket_m.h TLC Network Group - Politecnico di Torino 30 5

6 Personalized packet usage n to use in some.cc #include MyPacket_m.h n to create a new packet MyPacket *mypkt; mypkt = new MyPacket("packet"); n to set/get the sourceid mypkt->setsourceid(int value); EV<< mypkt->getsourceid(); n since it is a derived class from cpacket, it inherits all the methods mypkt->setbytelength(); // from cpacket if (mypkt->isscheduled()); // from cmessage TLC Network Group - Politecnico di Torino 31 Lab #5 TLC Network Group - Politecnico di Torino 32 Lossy channels n a bit error probability (ber) or a packet error probability (per) can be associated to a link n in ned file: network Ethernet { connections: mod1.out --> {datarate=100mbps;delay=5us;per= > mod2.in; Packet loss detection n at the receiver, hasbiterror() method of cpacket to check whether the packet has been received void Receiver::handleMessage(cMessage *msg) { // cast the msg into a packet // (assuming that it is possible) cpacket *pkt; pkt=check_and_cast<cpacket *>(msg); if (pkt->hasbiterror()) { // drop packet else { // manage a correctly received packet TLC Network Group - Politecnico di Torino 33 TLC Network Group - Politecnico di Torino 34 Go back N n at the tx n tx_window n base_seq -> min pkt id not yet acked n current_seq -> current pkt in tx n max_seq -> max pkt id not yet acked n at the rx n requested_seq -> id of the next pkt to receive n cumulative ack Receiver if received pkt has errors loose pkt else // pkt is correct if the pkt corresponds to requested_seq // pkt is accepted requested_seq++ send ack (requested_id) else // unexpected pkt discard pkt send ack (requested_id) TLC Network Group - Politecnico di Torino 35 TLC Network Group - Politecnico di Torino 36 6

7 Transmitter: end-of-tx if msg is end-of-tx // check if another transmission is possible // according to the current window if (current_seq<max_seq) // tx a new pkt current_seq++ transmit pkt with current_seq id schedule end-of-tx at txfinishtime reset timer TLC Network Group - Politecnico di Torino 37 Transmitter: ack - 1/2 if msg is an ack for ack_seq if ack is corrupted drop ack return // update the window base_seq=ack_seq max_seq=base_seq+tx_window-1 // check if end of file if (ack_seq>=file_size_in_pkts) // end the simulation and call finish endsimulation() // delete the pkt delete ack [continue on the following slide] TLC Network Group - Politecnico di Torino 38 Transmitter: ack 2/2 [continue from the previous slide] // if tx is idling, tx a new pkt if end-of-tx is not scheduled current_seq++ transmit pkt with current_seq id schedule end-of-tx at txfinishtime reset timer Transmitter: timeout if msg is timeout // restart to transmit from the beginning in window current_seq=base_seq-1 if end-of-tx is not scheduled // i.e. tx is idling // tx a new pkt current_seq++ transmit pkt with current_seq id schedule end-of-tx at txfinishtime reset timer TLC Network Group - Politecnico di Torino 39 TLC Network Group - Politecnico di Torino 40 Reset timer // if the timeout is still in the FES, remove it if (timeoutevent->isscheduled()) cancelevent(timeoutevent) // schedule a new timeout scheduleat(simtime()+timeout, timeoutevent); Lab #6 TLC Network Group - Politecnico di Torino 41 TLC Network Group - Politecnico di Torino 42 7

8 Wireless channel Possible simulator design n radio channel is shared medium n wireless communication is broadcast n not directly supported by Omnet++ n possible solution n central module (RX) responsible to manage the state of the channel and to detect interference among transmissions TX1 RX TX1 TX1 TLC Network Group - Politecnico di Torino 43 TLC Network Group - Politecnico di Torino 44 Possible simulator design n TX module n transmits a control message (START-RX) to RX to notify the start-of-reception n transmits a control message (END-RX) to RX to notify the end-of-reception Transmitter module of TX if msg is endtxevent, then dequeue pkt create END-RX control message send END-RX to RX at propagation-delay from now try to transmit from the queue if msg is a packet, then enqueue the pkt if server idling, then try to transmit from the queue TLC Network Group - Politecnico di Torino 45 TLC Network Group - Politecnico di Torino 46 Transmitter module Receiver module // function: try-to-transmit from the queue if queue is not empty compute the tx-time of the packet in front of queue schedule endtxevent at tx-time from now create the control message START-RX send START-RX to RX at propagation-delay from now if msg is START-RX num_contemporary_rx++ if (num_contemporary_rx==1) good_rx=true // maybe good reception else good_rx=false // interference! if msg is END-TX if (num_contemporary_rx==1 && good_rx) // packet has been received correctly! else // packet has been lost TLC Network Group - Politecnico di Torino 47 TLC Network Group - Politecnico di Torino 48 8

9 Direct sending - NED simple TXModule { gates: output simple ChannelModule { gates: input Direct sending C++ n at the transmitter // identify the receiver moduler cmodule *rxmodule = getparentmodule()->getsubmodule( channel"); // transmit directly to the radioin gate of channel module senddirect(msg,rxmodule,"radioin"); // or senddirect(msg,propagation_delay,datarate,rxmodule,"radioin"); // where datarate is considered only for cpacket *msg n at the receiver msg->getsendermoduleid() returns the id (integer value) of the sending module TLC Network Group - Politecnico di Torino 49 TLC Network Group - Politecnico di Torino 50 Control messages n it is possible to identify the kind of message/ packet with method setkind() and getkind() // EXAMPLES: // at TX, choose the kind of msg msg->setkind(1) // for START-RX msg->setkind(2) // for END-RX // at RX, identify the kind of msg if (msg->getkind()==1) { // START_RX else if (msg->getkind()==2) { // END-RX C++ STL map n To evaluate statistics, it may be possible to exploit map data structures available in C++ standard template library // Declaration std::map<int,long>num_rx_packets; // Update information for key 312 num_rx_packets[312]=num_rx_packets[312]+1 Key-1 Value-1 Key-2 Value-2 Key-3 Value-3 // Retrieve all the values in the map std::map<int,long>::iterator it; for (it=num_rx_packets.begin(); it!=num_rx_packets.end(); it++) { EV << key << it->first << value <<it->second<<endl; TLC Network Group - Politecnico di Torino 51 TLC Network Group - Politecnico di Torino 52 9