Finding the correct traversal path for a packet - unetstack

Question

Suppose a scenario similar to the above image where Node-A and Node-B are sending data to Node-D via Node-C. Node-A and Node-B each sent one data packet to Node-D. Node-A sent one msg with msg-id = 1 which is received at Node-C with msg-id = 1 and Node-B sent one msg with msg-id = 3 which is received at node-C with msg-id = 3. Now, how I will get to know that the msg forwarded from Node-C with msg-id = 2 is the msg from Node-A or Node-B and msg forwarded from Node-C with msg-id = 4 is the msg from Node-A or Node-B? How I will follow the correct path while traversing the trace.json file of simulation?

Answer 1

The trace.json file has information about the thread of events and stimulus that is related to each event. This may provide you the relevant information for your tracing.
To illustrate the idea, I take an example of how the ranging agent works. Other agents such as router work similarly, so you can use the same idea for tracing routed frames.
See the following entry from a trace.json output of a ranging simulation:
{
"time":1645606042088,
"component":"ranging::org.arl.unet.localization.Ranging/A",
"threadID":"88b89b82-eb37-4ac5-83da-3695acb80e7f",
"stimulus":{"clazz":"org.arl.unet.phy.RxFrameNtf","messageID":"88b89b82-eb37-4ac5-83da-3695acb80e7f","performative":"INFORM","sender":"phy","recipient":"#phy__ntf"},
"response":{"clazz":"org.arl.unet.phy.TxFrameReq","messageID":"ee9f72f5-5753-4d46-a885-9e446bbf9746","performative":"REQUEST","recipient":"phy"}
}
This entry shows that the received frame (RxFrameNtf) with ID 88b89b82... caused the transmission of a new frame (TxFrameReq) with ID ee9f72f5.... The threadID entry can also be helpful, as the same threadID is maintained for the whole chain of events within a single node.
Each of your frames from nodes A and B will have unique IDs, and so will each of the frames relayed by node C. The trace.json entry corresponding to each relay transmission should tell you which stimulus (frame from node A or B) resulted in the transmission.
For your application, I extract a few of the JSON entries from your trace.json to illustrate this:
{
"time":10000, "component":"router::org.arl.unet.net.Router/A", "threadID":"2e37d6d6-a3d2-4e0f-aacc-456efdae91bb",
"stimulus":{"clazz":"org.arl.unet.DatagramReq", "messageID":"2e37d6d6-a3d2-4e0f-aacc-456efdae91bb", "performative":"REQUEST", "sender":"simulator", "recipient":"router"},
"response":{"clazz":"org.arl.unet.DatagramReq", "messageID":"54a55a12-4051-4934-88bc-beb4fa28c548", "performative":"REQUEST", "recipient":"uwlink"}
}
{
"time":10491, "component":"uwlink::org.arl.unet.link.ReliableLink/A", "threadID":"54a55a12-4051-4934-88bc-beb4fa28c548",
"stimulus":{"clazz":"org.arl.unet.DatagramReq", "messageID":"54a55a12-4051-4934-88bc-beb4fa28c548", "performative":"REQUEST", "sender":"router", "recipient":"uwlink"},
"response":{"clazz":"org.arl.unet.phy.TxFrameReq", "messageID":"87757d67-7510-4856-a9ee-a27924f9548a", "performative":"REQUEST", "recipient":"phy"}
}
{
"time":10491, "component":"phy::org.arl.unet.sim.HalfDuplexModem/A", "threadID":"87757d67-7510-4856-a9ee-a27924f9548a",
"stimulus":{"clazz":"org.arl.unet.phy.TxFrameReq", "messageID":"87757d67-7510-4856-a9ee-a27924f9548a", "performative":"REQUEST", "sender":"uwlink", "recipient":"phy"},
"response":{"clazz":"org.arl.unet.sim.HalfDuplexModem$TX", "messageID":"31b892fd-1b2c-40b1-a1d6-4dc457f57a2c", "performative":"INFORM", "recipient":"phy"}
}
{
"time":11870, "component":"phy::org.arl.unet.sim.HalfDuplexModem/C", "threadID":"31b892fd-1b2c-40b1-a1d6-4dc457f57a2c",
"stimulus":{"clazz":"org.arl.unet.sim.HalfDuplexModem$TX", "messageID":"31b892fd-1b2c-40b1-a1d6-4dc457f57a2c", "performative":"INFORM", "sender":"phy", "recipient":"phy"},
"response":{"clazz":"org.arl.unet.phy.RxFrameNtf", "messageID":"5cd195ef-74b0-4394-8f9a-9077de08bc56", "performative":"INFORM", "sender":"phy", "recipient":"#phy__ntf"}
}
{
"time":11870, "component":"router::org.arl.unet.net.Router/C", "threadID":"5cd195ef-74b0-4394-8f9a-9077de08bc56",
"stimulus":{"clazz":"org.arl.unet.phy.RxFrameNtf", "messageID":"5cd195ef-74b0-4394-8f9a-9077de08bc56", "performative":"INFORM", "sender":"phy", "recipient":"#phy__ntf"},
"response":{"clazz":"org.arl.unet.DatagramReq", "messageID":"e9ecfc32-ff9a-4750-99d5-b3b462dcd660", "performative":"REQUEST", "recipient":"uwlink"}
}
{
"time":12259, "component":"uwlink::org.arl.unet.link.ReliableLink/C", "threadID":"e9ecfc32-ff9a-4750-99d5-b3b462dcd660",
"stimulus":{"clazz":"org.arl.unet.DatagramReq", "messageID":"e9ecfc32-ff9a-4750-99d5-b3b462dcd660", "performative":"REQUEST", "sender":"router", "recipient":"uwlink"},
"response":{"clazz":"org.arl.unet.phy.TxFrameReq", "messageID":"76200f60-2334-4f20-88a3-9c2d42a769ad", "performative":"REQUEST", "recipient":"phy"}
}
{
"time":12259, "component":"phy::org.arl.unet.sim.HalfDuplexModem/C", "threadID":"76200f60-2334-4f20-88a3-9c2d42a769ad",
"stimulus":{"clazz":"org.arl.unet.phy.TxFrameReq", "messageID":"76200f60-2334-4f20-88a3-9c2d42a769ad", "performative":"REQUEST", "sender":"uwlink", "recipient":"phy"},
"response":{"clazz":"org.arl.unet.sim.HalfDuplexModem$TX", "messageID":"f3161e4e-1007-4540-8192-f0d7bf80e126", "performative":"INFORM", "recipient":"phy"}
}
{
"time":13542, "component":"phy::org.arl.unet.sim.HalfDuplexModem/D", "threadID":"f3161e4e-1007-4540-8192-f0d7bf80e126",
"stimulus":{"clazz":"org.arl.unet.sim.HalfDuplexModem$TX", "messageID":"f3161e4e-1007-4540-8192-f0d7bf80e126", "performative":"INFORM", "sender":"phy", "recipient":"phy"},
"response":{"clazz":"org.arl.unet.phy.RxFrameNtf", "messageID":"ab5e15a9-27e0-4495-b0b8-f199159cb2a3", "performative":"INFORM", "sender":"phy", "recipient":"#phy__ntf"}
}
{
"time":13542, "component":"uwlink::org.arl.unet.link.ReliableLink/D", "threadID":"ab5e15a9-27e0-4495-b0b8-f199159cb2a3",
"stimulus":{"clazz":"org.arl.unet.phy.RxFrameNtf", "messageID":"ab5e15a9-27e0-4495-b0b8-f199159cb2a3", "performative":"INFORM", "sender":"phy", "recipient":"#phy__ntf"},
"response":{"clazz":"org.arl.unet.DatagramNtf", "messageID":"bb534fc0-47ec-4b2d-8124-07af87528d37", "performative":"INFORM", "recipient":"#uwlink__ntf"}
}
{
"time":13542, "component":"router::org.arl.unet.net.Router/D", "threadID":"bb534fc0-47ec-4b2d-8124-07af87528d37",
"stimulus":{"clazz":"org.arl.unet.DatagramNtf", "messageID":"bb534fc0-47ec-4b2d-8124-07af87528d37", "performative":"INFORM", "sender":"uwlink", "recipient":"#uwlink__ntf"},
"response":{"clazz":"org.arl.unet.DatagramNtf", "messageID":"5e660793-9a44-4341-8843-fc7fa91aa450", "performative":"INFORM", "recipient":"#router__ntf"}
}
These entries show the sequence of events that occurred:
time 10000: DatagramReq from router#A to uwlink#A
time 10491: TxFrameReq from uwlink#A to phy#A
time 10491: TX from phy#A to phy#C
time 11870: RxFrameNtf from phy#C (publish on topic)
time 11870: DatagramReq from router#C to uwlink#C
time 12259: TxFrameReq from uwlink#C to phy#C
time 12259: TX from phy#C to phy#D
time 13542: RxFrameNtf from phy#D (publish on topic)
time 13542: DatagramNtf from uwlink#D (publish on topic)
time 13542: DatagramNtf from router#D (publish on topic)
You should find that each JSON entry's response.messageID corresponds to the next JSON entry's stimulus.messageID. This allows you to follow through the sequence of events.