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Creation of a simple tsn network

Introduction

In this chapter, we will explore how to transform the Ethernet network simulation script from the previous chapter into a TSN network simulation script. Then, we will discuss how to instantiate and configure the various TSN mechanisms supported by the simulation library.

Note that the operation and configuration of TSN mechanisms will not be explained in depth. This chapter assumes that the reader is familiar with the details of the mechanisms implemented.

From Ethernet to TSN simulation

Let’s start by importing two new objects: TsnNode and TsnNetDevice.

[...]
#include "ns3/tsn-node.h"
#include "ns3/tsn-net-device.h"
[...]

Next, it is necessary to replace the node and EthernetNetDevice objects with their TSN versions in order to instantiate the various TSN mechanisms described below.

[...]
    //Create four nodes
    Ptr<TsnNode> n0 = CreateObject<TsnNode>();
    Names::Add("ES1", n0);
    Ptr<TsnNode> n1 = CreateObject<TsnNode>();
    Names::Add("ES2", n1);
    Ptr<TsnNode> n2 = CreateObject<TsnNode>();
    Names::Add("ES3", n2);
    Ptr<TsnNode> n3 = CreateObject<TsnNode>();
    Names::Add("SW", n3);

    //Create and add a netDevice to each end-station node
    Ptr<TsnNetDevice> net0 = CreateObject<TsnNetDevice>();
    n0->AddDevice(net0);
    Names::Add("ES1#01", net0);
    Ptr<TsnNetDevice> net1 = CreateObject<TsnNetDevice>();
    n1->AddDevice(net1);
    Names::Add("ES2#01", net1);
    Ptr<TsnNetDevice> net2 = CreateObject<TsnNetDevice>();
    n2->AddDevice(net2);
    Names::Add("ES3#01", net2);
    //Create and add a netDevice to each switch port
    Ptr<TsnNetDevice> swnet0 = CreateObject<TsnNetDevice>();
    n3->AddDevice(swnet0);
    Names::Add("SW#01", swnet0);
    Ptr<TsnNetDevice> swnet1 = CreateObject<TsnNetDevice>();
    n3->AddDevice(swnet1);
    Names::Add("SW#02", swnet1);
    Ptr<TsnNetDevice> swnet2 = CreateObject<TsnNetDevice>();
    n3->AddDevice(swnet2);
    Names::Add("SW#03", swnet2);
[...]

At this stage, it is possible to run a simulation, but the result will be identical to a simple Ethernet network.

To simplify the illustration of the latency control mechanisms (CBS and TAS), we can make the following modifications to the application:

[...]
    //Application description
    //ES1 -> ES3 with priority 1
    Ptr<EthernetGenerator> app0 = CreateObject<EthernetGenerator>();
    app0->Setup(net0);
    app0->SetAttribute("Address", AddressValue(net2->GetAddress()));
    app0->SetAttribute("BurstSize", UintegerValue(5));
    app0->SetAttribute("PayloadSize", UintegerValue(1400));
    app0->SetAttribute("Period", TimeValue(Seconds(5)));
    app0->SetAttribute("VlanID", UintegerValue(1));
    app0->SetAttribute("PCP", UintegerValue(1));
    n0->AddApplication(app0);
    app0->SetStartTime(Seconds(0));
    app0->SetStopTime(Seconds(10));
[...]

The output of a simulation should look like this:

[0/2] Re-checking globbed directories...
[2/2] Linking CXX executable ../build/scratch/ns3.40-book-default
Start of the simulation
+0s 	ES1:ES1#01 : Pkt #0 sent!
+0s 	ES1:ES1#01 : Pkt #1 sent!
+0s 	ES1:ES1#01 : Pkt #2 sent!
+0s 	ES1:ES1#01 : Pkt #3 sent!
+0s 	ES1:ES1#01 : Pkt #4 sent!
+0.000233905s 	ES3:ES3#01 : Pkt #0 received!
+0.000349265s 	ES3:ES3#01 : Pkt #1 received!
+0.000464625s 	ES3:ES3#01 : Pkt #2 received!
+0.000579985s 	ES3:ES3#01 : Pkt #3 received!
+0.000695345s 	ES3:ES3#01 : Pkt #4 received!
+5s 	ES1:ES1#01 : Pkt #5 sent!
+5s 	ES1:ES1#01 : Pkt #6 sent!
+5s 	ES1:ES1#01 : Pkt #7 sent!
+5s 	ES1:ES1#01 : Pkt #8 sent!
+5s 	ES1:ES1#01 : Pkt #9 sent!
+5.00023s 	ES3:ES3#01 : Pkt #5 received!
+5.00035s 	ES3:ES3#01 : Pkt #6 received!
+5.00046s 	ES3:ES3#01 : Pkt #7 received!
+5.00058s 	ES3:ES3#01 : Pkt #8 received!
+5.0007s 	ES3:ES3#01 : Pkt #9 received!
End of the simulation

CBS

To instantiate a CBS, we must first add its dependency.

#include "ns3/cbs.h"

It is then possible to instantiate a CBS and link it to an output port queue. In the following example, we instantiate the CBS on the output port of the transmitting end station.

[...]
    //Create 2 output port FIFOs for each netDevice.
    Ptr<Cbs> cbs = CreateObject<Cbs>();
    cbs->SetTsnNetDevice(net0);
    cbs->SetAttribute("IdleSlope", DataRateValue(DataRate("20Kb/s")));
    cbs->SetAttribute("portTransmitRate", DataRateValue(DataRate("100Mb/s")));
    net0->SetQueue(CreateObject<DropTailQueue<Packet>>());              //FIFO 0
    net0->SetQueue(CreateObject<DropTailQueue<Packet>>(), cbs);         //FIFO 1

    for (int i=0; i<2; i++){
        net1->SetQueue(CreateObject<DropTailQueue<Packet>>());
        net2->SetQueue(CreateObject<DropTailQueue<Packet>>());
        swnet0->SetQueue(CreateObject<DropTailQueue<Packet>>());
        swnet1->SetQueue(CreateObject<DropTailQueue<Packet>>());
        swnet2->SetQueue(CreateObject<DropTailQueue<Packet>>());
    }
[...]

When launching the simulation, we can now see that the reception of burst frames is spread out over time due to the waiting time imposed by the CBS credit reload on the emission port.

[0/2] Re-checking globbed directories...
[2/2] Linking CXX executable ../build/scratch/ns3.40-book-default
Start of the simulation
+0s 	ES1:ES1#01 : Pkt #0 sent!
+0s 	ES1:ES1#01 : Pkt #1 sent!
+0s 	ES1:ES1#01 : Pkt #2 sent!
+0s 	ES1:ES1#01 : Pkt #3 sent!
+0s 	ES1:ES1#01 : Pkt #4 sent!
+0.000233905s 	ES3:ES3#01 : Pkt #0 received!
+0.577031s 	ES3:ES3#01 : Pkt #1 received!
+1.15383s 	ES3:ES3#01 : Pkt #2 received!
+1.73063s 	ES3:ES3#01 : Pkt #3 received!
+2.30743s 	ES3:ES3#01 : Pkt #4 received!
+5s 	ES1:ES1#01 : Pkt #5 sent!
+5s 	ES1:ES1#01 : Pkt #6 sent!
+5s 	ES1:ES1#01 : Pkt #7 sent!
+5s 	ES1:ES1#01 : Pkt #8 sent!
+5s 	ES1:ES1#01 : Pkt #9 sent!
+5.00023s 	ES3:ES3#01 : Pkt #5 received!
+5.57703s 	ES3:ES3#01 : Pkt #6 received!
+6.15383s 	ES3:ES3#01 : Pkt #7 received!
+6.73063s 	ES3:ES3#01 : Pkt #8 received!
+7.30743s 	ES3:ES3#01 : Pkt #9 received!
End of the simulation

TAS

To instanciate TAS, we need to add a clock to the TsnNode, add GCL entries to the net device and add 8 FIFOs to the output ports. It can be done as follows:

[...]
    //Add a perfect clock to the SW node
    n3->AddClock(CreateObject<Clock>());
[...]
    //Create 8 output port FIFOs for each netDevice.
    Ptr<Cbs> cbs = CreateObject<Cbs>();
    cbs->SetTsnNetDevice(net0);
    cbs->SetAttribute("IdleSlope", DataRateValue(DataRate("20Kb/s")));
    cbs->SetAttribute("portTransmitRate", DataRateValue(DataRate("100Mb/s")));
    net0->SetQueue(CreateObject<DropTailQueue<Packet>>());              //FIFO 0
    net0->SetQueue(CreateObject<DropTailQueue<Packet>>(), cbs);         //FIFO 1
    for (int i=0; i<6; i++){
         net0->SetQueue(CreateObject<DropTailQueue<Packet>>());         //FIFO 0
    }

    for (int i=0; i<8; i++){
        net1->SetQueue(CreateObject<DropTailQueue<Packet>>());
        net2->SetQueue(CreateObject<DropTailQueue<Packet>>());
        swnet0->SetQueue(CreateObject<DropTailQueue<Packet>>());
        swnet1->SetQueue(CreateObject<DropTailQueue<Packet>>());
        swnet2->SetQueue(CreateObject<DropTailQueue<Packet>>());
    }
[...]
    //Configure TAS schedule
    swnet2->AddGclEntry(Time(Seconds(2)), 0);   //All gates are close
    swnet2->AddGclEntry(Time(Seconds(3)), 2);   //Only the gate of the FIFO 1 is open
    swnet2->StartTas();
[...]

In this example, a TAS schedule is added to the switch’s output port, used by the flow. This schedule is designed to delay the frames of the two bursts by approximately two seconds compared to the previous example. The result obtained is as follows.

[0/2] Re-checking globbed directories...
[2/2] Linking CXX executable ../build/scratch/ns3.40-book-default
Start of the simulation
+0s 	ES1:ES1#01 : Pkt #0 sent!
+0s 	ES1:ES1#01 : Pkt #1 sent!
+0s 	ES1:ES1#01 : Pkt #2 sent!
+0s 	ES1:ES1#01 : Pkt #3 sent!
+0s 	ES1:ES1#01 : Pkt #4 sent!
+2.00011s 	ES3:ES3#01 : Pkt #0 received!
+2.00023s 	ES3:ES3#01 : Pkt #1 received!
+2.00035s 	ES3:ES3#01 : Pkt #2 received!
+2.00046s 	ES3:ES3#01 : Pkt #3 received!
+2.30743s 	ES3:ES3#01 : Pkt #4 received!
+5s 	ES1:ES1#01 : Pkt #5 sent!
+5s 	ES1:ES1#01 : Pkt #6 sent!
+5s 	ES1:ES1#01 : Pkt #7 sent!
+5s 	ES1:ES1#01 : Pkt #8 sent!
+5s 	ES1:ES1#01 : Pkt #9 sent!
+7.00011s 	ES3:ES3#01 : Pkt #5 received!
+7.00023s 	ES3:ES3#01 : Pkt #6 received!
+7.00035s 	ES3:ES3#01 : Pkt #7 received!
+7.00046s 	ES3:ES3#01 : Pkt #8 received!
+7.30743s 	ES3:ES3#01 : Pkt #9 received!
End of the simulation

gPTP

To synchronize the nodes in our network using gPTP, several changes must be made. Let’s start with the includes.

[...]
#include "ns3/clock-constant-drift.h"
#include "ns3/gPTP.h"
#include "ns3/ethernet-header2.h"
[...]

Next, let’s modify the callbacks that log packet transmission and reception so that events are only logged if the VLAN ID matches the VLAN ID of the flows going from ES1 to ES3. This change prevents the output from being flooded with logs concerning the transmission or reception of synchronization frames. We also add a callback to log the difference between the perfect clock (the simulation time) and the device clock after each correction to verify that gPTP is working properly.

//A callback to log the pkt emission
static void
MacTxCallback(std::string context, Ptr<const Packet> p)
{
  Ptr<Packet> pkt = p->Copy();
  EthernetHeader2 ethHeader;
  pkt->RemoveHeader(ethHeader);
  if (ethHeader.GetVid() == 1) {
    NS_LOG_INFO((Simulator::Now()).As(Time::S) << " \t" << context << " : Pkt #" << p->GetUid() << " sent!");
  }
}

//A callback to log the pkt reception
static void
MacRxCallback(std::string context, Ptr<const Packet> p)
{
  Ptr<Packet> pkt = p->Copy();
  EthernetHeader2 ethHeader;
  pkt->RemoveHeader(ethHeader);
  if (ethHeader.GetVid() == 1) {
    NS_LOG_INFO((Simulator::Now()).As(Time::S) << " \t" << context << " : Pkt #" << p->GetUid() << " received!");
  }
}

//A callback to log clock offset after correction
static void
ClockAfterCorrectionCallback(std::string context, Time clockValue)
{
  NS_LOG_INFO("[GPTP] At " << Simulator::Now() << " on "<< context << " clock value after correction = " << clockValue.GetNanoSeconds() << "ns (error = "<< (Simulator::Now()-clockValue).GetNanoSeconds() << "ns)");
}

Next, we replace the perfect clock previously instantiated on n3(SW) in the TAS section with clock instantiation on the various network devices. Note that the clock instantiated on ES1(n0) is a perfect clock (i.e., it corresponds to the simulation time) since it acts as the Grandmaster.

[...]
    Ptr<TsnNode> n3 = CreateObject<TsnNode>();
    Names::Add("SW", n3);

    //Create and add clocks to TsnNodes
    Ptr<Clock> c0 = CreateObject<Clock>();      //perfect clock because Grandmaster
    n0->SetMainClock(c0);
    Ptr<ConstantDriftClock> c1 = CreateObject<ConstantDriftClock>();
    c1->SetAttribute("InitialOffset", TimeValue(Seconds(20)));
    c1->SetAttribute("DriftRate", DoubleValue(-50));
    c1->SetAttribute("Granularity", TimeValue(NanoSeconds(10)));
    n1->SetMainClock(c1);
    Ptr<ConstantDriftClock> c2 = CreateObject<ConstantDriftClock>();
    c2->SetAttribute("InitialOffset", TimeValue(Seconds(3)));
    c2->SetAttribute("DriftRate", DoubleValue(2));
    c2->SetAttribute("Granularity", TimeValue(NanoSeconds(10)));
    n2->SetMainClock(c2);
    Ptr<ConstantDriftClock> c3 = CreateObject<ConstantDriftClock>();
    c3->SetAttribute("InitialOffset", TimeValue(Seconds(0.5)));
    c3->SetAttribute("DriftRate", DoubleValue(-25));
    c3->SetAttribute("Granularity", TimeValue(NanoSeconds(10)));
    n3->SetMainClock(c3);

[...]

Then, we add and configure the gPTP instances on the different nodes. Note that the implementation of gPTP in Eden-sim only supports static configuration of gPTP (i.e. no BTCA).

    [...]
	swnet2->SetQueue(CreateObject<DropTailQueue<Packet>>());
    }

    Ptr<GPTP> gPTP0 = CreateObject<GPTP>();
    gPTP0->SetNode(n0);
    gPTP0->SetMainClock(c0);
    gPTP0->AddDomain(0);
    gPTP0->AddPort(net0, GPTP::MASTER, 0);
    gPTP0->SetAttribute("SyncInterval", TimeValue(Seconds(0.125)));     //This line is not mandatory because 0.125s is the default value
    gPTP0->SetAttribute("PdelayInterval", TimeValue(Seconds(1)));        //This line is not mandatory because 1s is the default value
    gPTP0->SetAttribute("Priority", UintegerValue(7));
    n0->AddApplication(gPTP0);
    gPTP0->SetStartTime(Seconds(0));
    Ptr<GPTP> gPTP1 = CreateObject<GPTP>();
    gPTP1->SetNode(n1);
    gPTP1->SetMainClock(c1);
    gPTP1->AddDomain(0);
    gPTP1->AddPort(net1, GPTP::SLAVE, 0);
    gPTP1->SetAttribute("Priority", UintegerValue(7));
    n1->AddApplication(gPTP1);
    gPTP1->SetStartTime(Seconds(0));
    Ptr<GPTP> gPTP2 = CreateObject<GPTP>();
    gPTP2->SetNode(n2);
    gPTP2->SetMainClock(c2);
    gPTP2->AddDomain(0);
    gPTP2->AddPort(net2, GPTP::SLAVE, 0);
    gPTP2->SetAttribute("Priority", UintegerValue(7));
    n2->AddApplication(gPTP2);
    gPTP2->SetStartTime(Seconds(0));
    Ptr<GPTP> gPTP3 = CreateObject<GPTP>();
    gPTP3->SetNode(n3);
    gPTP3->SetMainClock(c3);
    gPTP3->AddDomain(0);
    gPTP3->AddPort(swnet0, GPTP::SLAVE, 0);
    gPTP3->AddPort(swnet1, GPTP::MASTER, 0);
    gPTP3->AddPort(swnet2, GPTP::MASTER, 0);
    gPTP3->SetAttribute("Priority", UintegerValue(7));
    n3->AddApplication(gPTP3);
    gPTP3->SetStartTime(Seconds(0));

And finally, we add the callbacks.

[...]
    net2->TraceConnectWithoutContext("MacRx", MakeBoundCallback(&MacRxCallback, context));
    //Callback to display clock offset after correction 
    gPTP1->TraceConnectWithoutContext("ClockAfterCorrection", MakeBoundCallback(&ClockAfterCorrectionCallback, Names::FindName(n1)));
    gPTP2->TraceConnectWithoutContext("ClockAfterCorrection", MakeBoundCallback(&ClockAfterCorrectionCallback, Names::FindName(n2)));
    gPTP3->TraceConnectWithoutContext("ClockAfterCorrection", MakeBoundCallback(&ClockAfterCorrectionCallback, Names::FindName(n3)));
[...]

When running the simulation, we can observe that gPTP effectively mitigates clock drift thanks to periodic synchronization on SW and ES2. However, we note that there is no gPTP log for ES3. This is due to the TAS configuration, which never opens the FIFO7 gate used by synchronization messages. Of course, such a configuration has no place in a network that is intended to be functional, but in this example it illustrates the impact of the TAS configuration on gPTP packets.

Stream Identification

Before using PSFP or FRER, it is necessary to implement an identification function. In this section, we will use a null Stream identification function on the switch port connected to ES1. This function will then be used in the following two sections to implement PSFP in order to validate the flow contract and to replicate frames using FRER.

Let’s start by importing this function.

[...]
#include "ns3/stream-identification-function-null.h"
[...]

Next, let’s create and add the identification function on port swnet0 in input and outfacing mode.

[...]
    swnet2->StartTas();

    //Add a stream identification function
    Ptr<NullStreamIdentificationFunction> sif0 = CreateObject<NullStreamIdentificationFunction>();
    uint16_t StreamHandle = 10;
    sif0->SetAttribute("VlanID", UintegerValue(1));
    sif0->SetAttribute("Address", AddressValue(net2->GetAddress()));
    n3->AddStreamIdentificationFunction(StreamHandle, sif0, {swnet0}, {}, {}, {});
[...]

PSFP

Now that we have an identification function capable of identifying frames going from ES1 to ES3 with VLAN ID 1, we can set up a PSFP instance to validate compliance with a network usage contract. Currently, the simulator implements the stream filter and the flow meter. They can be added and configured as follows.

[...]
    n3->AddStreamIdentificationFunction(StreamHandle, sif0, {swnet0}, {}, {}, {});

    //PSFP configuration
    Ptr<StreamFilterInstance> sfi0 = CreateObject<StreamFilterInstance>();
    sfi0->SetAttribute("StreamHandle", IntegerValue(StreamHandle));
    sfi0->SetAttribute("Priority", IntegerValue(-1)); //-1 = wildcard
    sfi0->SetAttribute("MaxSDUSize", UintegerValue(1422));
    n3->AddStreamFilter(sfi0);
    Ptr<FlowMeterInstance> fm0 = CreateObject<FlowMeterInstance>();
    fm0->SetAttribute("CIR", DataRateValue(DataRate("20Kb/s")));
    fm0->SetAttribute("CBS", UintegerValue(1400));
    fm0->SetAttribute("DropOnYellow", BooleanValue(true));
    fm0->SetAttribute("MarkAllFramesRedEnable", BooleanValue(false));
    uint16_t fmid = n3->AddFlowMeter(fm0);
    sfi0->AddFlowMeterInstanceId(fmid);
[...]

After these changes, running the simulation does not produce a different output from previous runs. However, by changing the parameters of the emitting application to increase its bandwidth consumption (e.g., increasing the packet size) or by increasing the idle slope of the CBS, it is possible to observe that packets that do not comply with the contract are never received as they are discarded.

FRER

And finally, let’s instantiate FRER. However, the topology we are working with in this chapter does not have multiple paths between ES1 and ES3. So in this section, we will replicate the frames on the output ports of the switch connected to ES2 and ES3 to illustrate the philosophy behind FRER instantiation. We will only detail the replication part. The elimination part is detailed in the example contrib/tsn/examples/tsn-switched-withFRER.cc, which has a topology much more suited to the use of FRER.

Replication with FRER is based on two functions: Sequence Generation Function and Sequence Encode/Decode Function. These two functions are created and configured as follows.

[...]
    sfi0->AddFlowMeterInstanceId(fmid);

    //Sequencing : Sequence generation
    Ptr<SequenceGenerationFunction> seqf0 = CreateObject<SequenceGenerationFunction>();
    seqf0->SetAttribute("Direction", BooleanValue(false));   //in-facing
    seqf0->SetStreamHandle({StreamHandle});
    n3->AddSequenceGenerationFunction(seqf0);
    //Sequence encode
    Ptr<SequenceEncodeDecodeFunction> seqEnc0 = CreateObject<SequenceEncodeDecodeFunction>();
    seqEnc0->SetAttribute("Direction", BooleanValue(false)); //in-facing
    seqEnc0->SetAttribute("Active", BooleanValue(true));
    seqEnc0->SetStreamHandle({StreamHandle});
    seqEnc0->SetPort(swnet0);
    n3->AddSequenceEncodeDecodeFunction(seqEnc0);

    //Add a forwarding table entry
    sw->AddForwardingTableEntry(Mac48Address::ConvertFrom(net2->GetAddress()), 1, {swnet1, swnet2});
[...]

With this configuration, replication is achieved by forwarding to two different ports. This simplifies configuration by not using the FRER splitting function. However, it is necessary to change the configuration of the forwarding table as shown in the previous listing.

In order to validate the correct operation of the replication (i.e., the addition of the R-TAG), modify the callbacks as follows to display the frame size at transmission and reception.

[...]
//A callback to log the pkt emission
static void
MacTxCallback(std::string context, Ptr<const Packet> p)
{
  Ptr<Packet> pkt = p->Copy();
  EthernetHeader2 ethHeader;
  pkt->RemoveHeader(ethHeader);
  if (ethHeader.GetVid() == 1) {
    NS_LOG_INFO((Simulator::Now()).As(Time::S) << " \t" << context << " : Pkt #" << p->GetUid() << "(" << p->GetSize() << "bytes) sent!");
  }
}

//A callback to log the pkt reception
static void
MacRxCallback(std::string context, Ptr<const Packet> p)
{
  Ptr<Packet> pkt = p->Copy();
  EthernetHeader2 ethHeader;
  pkt->RemoveHeader(ethHeader);
  if (ethHeader.GetVid() == 1) {
    NS_LOG_INFO((Simulator::Now()).As(Time::S) << " \t" << context << " : Pkt #" << p->GetUid() << "(" << p->GetSize() << "bytes) received!");
  }
}
[...]

And now, when running the simulation script, we observe an increase in frame size of 6 bytes (the size of R-TAG) between transmission and reception, as illustrated below.

[...]
+5s 	ES1:ES1#01 : Pkt #215(1422bytes) sent!
[...]
+7.30743s 	ES3:ES3#01 : Pkt #215(1428bytes) received!
[...]

Conclusion and final simulation script

In this section, we have implemented the various TSN mechanisms of Eden-sim.

Note that the examples found in contrib/tsn/examples/ illustrate more complicated configurations and implement different traces to log information about the mechanism’s operation. These examples are a good means of further exploring the uses of these TSN mechanisms.

Here is the script at the end of this chapter:

#include "ns3/simulator.h"
#include "ns3/core-module.h"
#include "ns3/node.h"
#include "ns3/drop-tail-queue.h"

#include "ns3/tsn-node.h"
#include "ns3/tsn-net-device.h"
#include "ns3/cbs.h"
#include "ns3/ethernet-channel.h"
#include "ns3/switch-net-device.h"
#include "ns3/ethernet-generator.h"
#include "ns3/clock-constant-drift.h"
#include "ns3/gPTP.h"
#include "ns3/ethernet-header2.h"
#include "ns3/stream-identification-function-null.h"

using namespace ns3;
NS_LOG_COMPONENT_DEFINE("Chapter 3");

//A callback to log the pkt emission
static void
MacTxCallback(std::string context, Ptr<const Packet> p)
{
  Ptr<Packet> pkt = p->Copy();
  EthernetHeader2 ethHeader;
  pkt->RemoveHeader(ethHeader);  
  if (ethHeader.GetVid() == 1) {
    NS_LOG_INFO((Simulator::Now()).As(Time::S) << " \t" << context << " : Pkt #" << p->GetUid() << "(" << p->GetSize() << "bytes) sent!");
  }
}

//A callback to log the pkt reception
static void
MacRxCallback(std::string context, Ptr<const Packet> p)
{
  Ptr<Packet> pkt = p->Copy();
  EthernetHeader2 ethHeader;
  pkt->RemoveHeader(ethHeader);  
  if (ethHeader.GetVid() == 1) {
    NS_LOG_INFO((Simulator::Now()).As(Time::S) << " \t" << context << " : Pkt #" << p->GetUid() << "(" << p->GetSize() << "bytes) received!");
  }
}

//A callback to log clock offset after correction
static void
ClockAfterCorrectionCallback(std::string context, Time clockValue)
{
  NS_LOG_INFO("[GPTP] At " << Simulator::Now() << " on "<< context << " clock value after correction = " << clockValue.GetNanoSeconds() << "ns (error = "<< (Simulator::Now()-clockValue).GetNanoSeconds() << "ns)");
}

int
main(int argc, char* argv[])
{
    //Enable logging
    LogComponentEnable("Chapter 3", LOG_LEVEL_INFO);

    //Create four nodes
    Ptr<TsnNode> n0 = CreateObject<TsnNode>();
    Names::Add("ES1", n0);
    Ptr<TsnNode> n1 = CreateObject<TsnNode>();
    Names::Add("ES2", n1);
    Ptr<TsnNode> n2 = CreateObject<TsnNode>();
    Names::Add("ES3", n2);
    Ptr<TsnNode> n3 = CreateObject<TsnNode>();
    Names::Add("SW", n3);

    //Create and add clocks to TsnNodes
    Ptr<Clock> c0 = CreateObject<Clock>();	//perfect clock because Grandmaster
    n0->SetMainClock(c0);
    Ptr<ConstantDriftClock> c1 = CreateObject<ConstantDriftClock>();
    c1->SetAttribute("InitialOffset", TimeValue(Seconds(20)));
    c1->SetAttribute("DriftRate", DoubleValue(-50));
    c1->SetAttribute("Granularity", TimeValue(NanoSeconds(10)));
    n1->SetMainClock(c1);
    Ptr<ConstantDriftClock> c2 = CreateObject<ConstantDriftClock>();
    c2->SetAttribute("InitialOffset", TimeValue(Seconds(3)));
    c2->SetAttribute("DriftRate", DoubleValue(2));
    c2->SetAttribute("Granularity", TimeValue(NanoSeconds(10)));
    n2->SetMainClock(c2);
    Ptr<ConstantDriftClock> c3 = CreateObject<ConstantDriftClock>();
    c3->SetAttribute("InitialOffset", TimeValue(Seconds(0.5)));
    c3->SetAttribute("DriftRate", DoubleValue(-25));
    c3->SetAttribute("Granularity", TimeValue(NanoSeconds(10)));
    n3->SetMainClock(c3);


    //Create and add a netDevice to each end-station node
    Ptr<TsnNetDevice> net0 = CreateObject<TsnNetDevice>();
    net0->SetAttribute("DataRate", DataRateValue(DataRate("100Mb/s")));
    n0->AddDevice(net0);
    Names::Add("ES1#01", net0);
    Ptr<TsnNetDevice> net1 = CreateObject<TsnNetDevice>();
    net1->SetAttribute("DataRate", DataRateValue(DataRate("100Mb/s")));
    n1->AddDevice(net1);
    Names::Add("ES2#01", net1);
    Ptr<TsnNetDevice> net2 = CreateObject<TsnNetDevice>();
    net2->SetAttribute("DataRate", DataRateValue(DataRate("100Mb/s")));
    n2->AddDevice(net2);
    Names::Add("ES3#01", net2);
    //Create and add a netDevice to each switch port
    Ptr<TsnNetDevice> swnet0 = CreateObject<TsnNetDevice>();
    swnet0->SetAttribute("DataRate", DataRateValue(DataRate("100Mb/s")));
    n3->AddDevice(swnet0);
    Names::Add("SW#01", swnet0);
    Ptr<TsnNetDevice> swnet1 = CreateObject<TsnNetDevice>();
    swnet1->SetAttribute("DataRate", DataRateValue(DataRate("100Mb/s")));
    n3->AddDevice(swnet1);
    Names::Add("SW#02", swnet1);
    Ptr<TsnNetDevice> swnet2 = CreateObject<TsnNetDevice>();
    swnet2->SetAttribute("DataRate", DataRateValue(DataRate("100Mb/s")));
    n3->AddDevice(swnet2);
    Names::Add("SW#03", swnet2);

    //Create Ethernet Channels and connect switch to the end-stations
    Ptr<EthernetChannel> channel0 = CreateObject<EthernetChannel>();
    channel0->SetAttribute("Delay", TimeValue(NanoSeconds(50)));
    net0->Attach(channel0);
    swnet0->Attach(channel0);
    Ptr<EthernetChannel> channel1 = CreateObject<EthernetChannel>();
    channel1->SetAttribute("Delay", TimeValue(NanoSeconds(75)));
    net1->Attach(channel1);
    swnet1->Attach(channel1);
    Ptr<EthernetChannel> channel2 = CreateObject<EthernetChannel>();
    channel2->SetAttribute("Delay", TimeValue(NanoSeconds(100)));
    net2->Attach(channel2);
    swnet2->Attach(channel2);

    //Create and add a switch net device to the switch node
    Ptr<SwitchNetDevice> sw = CreateObject<SwitchNetDevice>();
    sw->SetAttribute("MinForwardingLatency", TimeValue(MicroSeconds(2)));
    sw->SetAttribute("MaxForwardingLatency", TimeValue(MicroSeconds(5))); 
    n3->AddDevice(sw);
    sw->AddSwitchPort(swnet0);
    sw->AddSwitchPort(swnet1);
    sw->AddSwitchPort(swnet2);

    //Allocate Mac addresses to the netDevices 
    net0->SetAddress(Mac48Address::Allocate());
    net1->SetAddress(Mac48Address::Allocate());
    net2->SetAddress(Mac48Address::Allocate());
    sw->SetAddress(Mac48Address::Allocate());
    
    //Create 8 output port FIFOs for each netDevice.
    Ptr<Cbs> cbs = CreateObject<Cbs>();
    cbs->SetTsnNetDevice(net0);
    cbs->SetAttribute("IdleSlope", DataRateValue(DataRate("20Kb/s")));
    cbs->SetAttribute("portTransmitRate", DataRateValue(DataRate("100Mb/s")));
    net0->SetQueue(CreateObject<DropTailQueue<Packet>>());		//FIFO 0
    net0->SetQueue(CreateObject<DropTailQueue<Packet>>(), cbs);		//FIFO 1
    for (int i=0; i<6; i++){
         net0->SetQueue(CreateObject<DropTailQueue<Packet>>());		//FIFO 0
    }

    for (int i=0; i<8; i++){
	net1->SetQueue(CreateObject<DropTailQueue<Packet>>());
	net2->SetQueue(CreateObject<DropTailQueue<Packet>>());
	swnet0->SetQueue(CreateObject<DropTailQueue<Packet>>());
	swnet1->SetQueue(CreateObject<DropTailQueue<Packet>>());
	swnet2->SetQueue(CreateObject<DropTailQueue<Packet>>()); 
    }

    //Add and configure gPTP
    Ptr<GPTP> gPTP0 = CreateObject<GPTP>();
    gPTP0->SetNode(n0);
    gPTP0->SetMainClock(c0);
    gPTP0->AddDomain(0);
    gPTP0->AddPort(net0, GPTP::MASTER, 0);
    gPTP0->SetAttribute("SyncInterval", TimeValue(Seconds(0.125)));     //This line is not mandatory because 0.125s is the default value
    gPTP0->SetAttribute("PdelayInterval", TimeValue(Seconds(1)));        //This line is not mandatory because 1s is the default value
    gPTP0->SetAttribute("Priority", UintegerValue(7));
    n0->AddApplication(gPTP0);
    gPTP0->SetStartTime(Seconds(0));
    Ptr<GPTP> gPTP1 = CreateObject<GPTP>();
    gPTP1->SetNode(n1);
    gPTP1->SetMainClock(c1);
    gPTP1->AddDomain(0);
    gPTP1->AddPort(net1, GPTP::SLAVE, 0);
    gPTP1->SetAttribute("Priority", UintegerValue(7));
    n1->AddApplication(gPTP1);
    gPTP1->SetStartTime(Seconds(0));
    Ptr<GPTP> gPTP2 = CreateObject<GPTP>();
    gPTP2->SetNode(n2);
    gPTP2->SetMainClock(c2);
    gPTP2->AddDomain(0);
    gPTP2->AddPort(net2, GPTP::SLAVE, 0);
    gPTP2->SetAttribute("Priority", UintegerValue(7));
    n2->AddApplication(gPTP2);
    gPTP2->SetStartTime(Seconds(0));
    Ptr<GPTP> gPTP3 = CreateObject<GPTP>();
    gPTP3->SetNode(n3);
    gPTP3->SetMainClock(c3);
    gPTP3->AddDomain(0);
    gPTP3->AddPort(swnet0, GPTP::SLAVE, 0);
    gPTP3->AddPort(swnet1, GPTP::MASTER, 0);
    gPTP3->AddPort(swnet2, GPTP::MASTER, 0);
    gPTP3->SetAttribute("Priority", UintegerValue(7));
    n3->AddApplication(gPTP3);
    gPTP3->SetStartTime(Seconds(0));

    //Configure TAS schedule
    swnet2->AddGclEntry(Time(Seconds(2)), 0);   //All gates are close
    swnet2->AddGclEntry(Time(Seconds(3)), 2);   //Only the gate of the FIFO 1 is open
    swnet2->StartTas();

    //Add a stream identification function
    Ptr<NullStreamIdentificationFunction> sif0 = CreateObject<NullStreamIdentificationFunction>();
    uint16_t StreamHandle = 10;
    sif0->SetAttribute("VlanID", UintegerValue(1));
    sif0->SetAttribute("Address", AddressValue(net2->GetAddress()));
    n3->AddStreamIdentificationFunction(StreamHandle, sif0, {swnet0}, {}, {}, {});

    //PSFP configuration
    Ptr<StreamFilterInstance> sfi0 = CreateObject<StreamFilterInstance>();
    sfi0->SetAttribute("StreamHandle", IntegerValue(StreamHandle));
    sfi0->SetAttribute("Priority", IntegerValue(-1)); //-1 = wildcard
    sfi0->SetAttribute("MaxSDUSize", UintegerValue(1422));
    n3->AddStreamFilter(sfi0);
    Ptr<FlowMeterInstance> fm0 = CreateObject<FlowMeterInstance>();
    fm0->SetAttribute("CIR", DataRateValue(DataRate("20Kb/s")));
    fm0->SetAttribute("CBS", UintegerValue(1400));
    fm0->SetAttribute("DropOnYellow", BooleanValue(true));
    fm0->SetAttribute("MarkAllFramesRedEnable", BooleanValue(false));
    uint16_t fmid = n3->AddFlowMeter(fm0);
    sfi0->AddFlowMeterInstanceId(fmid);

    //Sequencing : Sequence generation
    Ptr<SequenceGenerationFunction> seqf0 = CreateObject<SequenceGenerationFunction>();
    seqf0->SetAttribute("Direction", BooleanValue(false));   //in-facing
    seqf0->SetStreamHandle({StreamHandle});
    n3->AddSequenceGenerationFunction(seqf0);
    //Sequence encode
    Ptr<SequenceEncodeDecodeFunction> seqEnc0 = CreateObject<SequenceEncodeDecodeFunction>();
    seqEnc0->SetAttribute("Direction", BooleanValue(false)); //in-facing
    seqEnc0->SetAttribute("Active", BooleanValue(true));
    seqEnc0->SetStreamHandle({StreamHandle});
    seqEnc0->SetPort(swnet0);
    n3->AddSequenceEncodeDecodeFunction(seqEnc0);

    //Add a forwarding table entry
    sw->AddForwardingTableEntry(Mac48Address::ConvertFrom(net2->GetAddress()), 1, {swnet1, swnet2});

    //Application description
    //ES1 -> ES3 with priority 1
    Ptr<EthernetGenerator> app0 = CreateObject<EthernetGenerator>();
    app0->Setup(net0);
    app0->SetAttribute("Address", AddressValue(net2->GetAddress()));
    app0->SetAttribute("BurstSize", UintegerValue(5));
    app0->SetAttribute("PayloadSize", UintegerValue(1400));
    app0->SetAttribute("Period", TimeValue(Seconds(5)));
    app0->SetAttribute("VlanID", UintegerValue(1));
    app0->SetAttribute("PCP", UintegerValue(1));
    n0->AddApplication(app0);
    app0->SetStartTime(Seconds(0));
    app0->SetStopTime(Seconds(10));
    
    //Callback declarations
    //Callback to display the packet sent log
    std::string context = Names::FindName(n0) + ":" + Names::FindName(net0);
    net0->TraceConnectWithoutContext("MacTx", MakeBoundCallback(&MacTxCallback, context));
    //Callback to display the packet received log
    context = Names::FindName(n2) + ":" + Names::FindName(net2);
    net2->TraceConnectWithoutContext("MacRx", MakeBoundCallback(&MacRxCallback, context));
    //Callback to display clock offset after correction	
    gPTP1->TraceConnectWithoutContext("ClockAfterCorrection", MakeBoundCallback(&ClockAfterCorrectionCallback, Names::FindName(n1)));
    gPTP2->TraceConnectWithoutContext("ClockAfterCorrection", MakeBoundCallback(&ClockAfterCorrectionCallback, Names::FindName(n2)));
    gPTP3->TraceConnectWithoutContext("ClockAfterCorrection", MakeBoundCallback(&ClockAfterCorrectionCallback, Names::FindName(n3)));

    
    //Execute the simulation
    NS_LOG_INFO("Start of the simulation");
    Simulator::Stop(Seconds(10));
    Simulator::Run();
    Simulator::Destroy();
    NS_LOG_INFO("End of the simulation");
    return 0;
}