About time synchronization in TSN showcases

[p4pe]

Hello everyone,

I am a newbie with omnet++ and inet and currently, I started to use it in order to examine TSN Time-Aware-Shaper (TAS). I show the showcases that are provided, and I have a question regarding the synchronization between the nodes.

I extend the default linear topology:

package _5switches.simulations;


import inet.networks.base.TsnNetworkBase;
import inet.node.contract.IEthernetNetworkNode;
import inet.node.ethernet.EthernetLink;

network TsnDumbbellNetwork extends TsnNetworkBase
{
    parameters:
        *.eth[*].bitrate = default(100Mbps);
    submodules:
        client: <default("TsnDevice")> like IEthernetNetworkNode {
            @display("p=300,150");
        }
        client2: <default("TsnDevice")> like IEthernetNetworkNode {
            @display("p=300,350");
        }
        switch1: <default("TsnSwitch")> like IEthernetNetworkNode {
            @display("p=500,250");
        }
        switch2: <default("TsnSwitch")> like IEthernetNetworkNode {
            @display("p=700,250");
        }
         switch3: <default("TsnSwitch")> like IEthernetNetworkNode {
            @display("p=900,250");
        }
         switch4: <default("TsnSwitch")> like IEthernetNetworkNode {
            @display("p=1100,250");
        }
         switch5: <default("TsnSwitch")> like IEthernetNetworkNode {
            @display("p=1300,250");
        }
        server: <default("TsnDevice")> like IEthernetNetworkNode {
            @display("p=1500,150");
        }
        server2: <default("TsnDevice")> like IEthernetNetworkNode {
            @display("p=1700,350");
        }
    connections:
        client.ethg++ <--> EthernetLink <--> switch1.ethg++;
        client2.ethg++ <--> EthernetLink <--> switch1.ethg++;
        switch1.ethg++ <--> EthernetLink <--> switch2.ethg++;
        switch2.ethg++ <--> EthernetLink <--> switch3.ethg++;
        switch3.ethg++ <--> EthernetLink <--> switch4.ethg++;
        switch4.ethg++ <--> EthernetLink <--> switch5.ethg++;
        switch5.ethg++ <--> EthernetLink <--> server.ethg++;
        switch5.ethg++ <--> EthernetLink <--> server2.ethg++;
}

Are the nodes in the topology synchronized or I should add a clock or another kind of configuration?

Thank you in advance.

[levy]

They are perfectly synchronized by default. You can add local clock and configure the gPtp time synchronization protocol if you need that. See this showcase for example.

[p4pe]

Thank you for the confirmation @levy may I ask you something else;

Based on the above topology, I added two more clients (client3 and client4) connected to switch1.
I am facing some problems with the configuration of the gates and I don't know if I understood correctly how it works.
I have an external custom solver that computes the schedules for high-priority traffic (e.g. video).

I have two video flows, from client --> server and from client3 --> server.
Also I have two clients that send best-effort traffic (client2, client4, to server2)
Based on the solver the "video packet" should leave the egress interface of the switch every 86us.

Switch1 -> 86us
Switch2 -> 172us
Switch3-> 258us
Switch4 -> 344us
Switch5 -> 430us

The configuration is below:

# time-aware traffic shaping
*.switch1.eth[*].macLayer.queue.numTrafficClasses = 2
*.switch1.eth[*].macLayer.queue.*[0].display-name = "best effort"
*.switch1.eth[*].macLayer.queue.*[1].display-name = "video"
*.switch1.eth[*].macLayer.queue.transmissionGate[0].offset = 542us
*.switch1.eth[*].macLayer.queue.transmissionGate[0].durations = [628us, 172us] # period is 10
*.switch1.eth[*].macLayer.queue.transmissionGate[1].offset = -86us
*.switch1.eth[*].macLayer.queue.transmissionGate[1].durations = [1us,1us, 171us, 627us]

*.switch2.eth[*].macLayer.queue.numTrafficClasses = 2
*.switch2.eth[*].macLayer.queue.*[0].display-name = "best effort"
*.switch2.eth[*].macLayer.queue.*[1].display-name = "video"
*.switch2.eth[*].macLayer.queue.transmissionGate[0].offset = 456us
*.switch2.eth[*].macLayer.queue.transmissionGate[0].durations = [628us, 172us] # period is 10
*.switch2.eth[*].macLayer.queue.transmissionGate[1].offset = -172us
*.switch2.eth[*].macLayer.queue.transmissionGate[1].durations = [1us,1us, 171us, 627us]

*.switch3.eth[*].macLayer.queue.numTrafficClasses = 2
*.switch3.eth[*].macLayer.queue.*[0].display-name = "best effort"
*.switch3.eth[*].macLayer.queue.*[1].display-name = "video"
*.switch3.eth[*].macLayer.queue.transmissionGate[0].offset = 370us
*.switch3.eth[*].macLayer.queue.transmissionGate[0].durations = [628us, 172us] # period is 10
*.switch3.eth[*].macLayer.queue.transmissionGate[1].offset = -258us
*.switch3.eth[*].macLayer.queue.transmissionGate[1].durations = [1us,1us, 171us, 627us]

*.switch4.eth[*].macLayer.queue.numTrafficClasses = 2
*.switch4.eth[*].macLayer.queue.*[0].display-name = "best effort"
*.switch4.eth[*].macLayer.queue.*[1].display-name = "video"
*.switch4.eth[*].macLayer.queue.transmissionGate[0].offset = 284us
*.switch4.eth[*].macLayer.queue.transmissionGate[0].durations = [628us, 172us] # period is 10
*.switch4.eth[*].macLayer.queue.transmissionGate[1].offset = -344us
*.switch4.eth[*].macLayer.queue.transmissionGate[1].durations = [1us,1us, 171us, 627us]

*.switch5.eth[*].macLayer.queue.numTrafficClasses = 2
*.switch5.eth[*].macLayer.queue.*[0].display-name = "best effort"
*.switch5.eth[*].macLayer.queue.*[1].display-name = "video"
*.switch5.eth[*].macLayer.queue.transmissionGate[0].offset = 198us
*.switch5.eth[*].macLayer.queue.transmissionGate[0].durations = [628us, 172us] # period is 10
*.switch5.eth[*].macLayer.queue.transmissionGate[1].offset = -430us
*.switch5.eth[*].macLayer.queue.transmissionGate[1].durations = [1us,1us, 171us, 627us]

I run the simulation but it seems that something is going wrong from switch2 --> switch3

I can not figure out what is going wrong.

Thank you in advance.

[levy]

I can't tell what's wrong, I'm sorry but it would take me too much effort to understand what's going on in your example. Try to come up with a small example that demonstrates incorrect behavior.

[Abh4git]

Its quite an old post. Maybe you already figured out the issue. Would be great to post here. Is it due to -8us (negative) in offset somehow leading to the traffic not going next step? Just curious. Thank you for your time!

[p4pe]

The issue was due to a misconfiguration of the PCP value.

[Abh4git]

Thank you for the update!