Ryu(SDN) - identify packet send by controller from switch to switch

Question

I am a newbie to SDN and have to implement latency monitor with Ryu controller.

I am thinking of sending a packet from switch to switch, where i remember the packet send, and then i recieve it at end switch i will calculate the delay.

The problem is i dont know how to tell apart the packets, which i send. I was thinking of putting into them a string which would tell me:"hey i am packet number 23." But i dont know if it is possible. I read the ryu wiki several times and looked over the examples.

I just dont know how to move forward.

Answer 1

I have answered a similar question over here about how to measure latency. You can have a look. But if you wanna go ahead with your current approach. You can try something like this:

1. Record switch details and current timing value in packet and send the packet to next switch (via the link for which you want to measure latency).

2. When recieved that packet on another switch parse the recorded information.

3. Subtract the timing delay.

For example you can have a look at RYU implementation at here which uses a kind of similar mechanism to discover topology. LLDP packets are generated by controller, sent to one switch which is to be forwarded via a specific port, when another switch receives this packet, it parses the packet to obtain sender switch's id and port and again sends this information to controller, which in-turn detects that there is a path between these switches.

But I would suggest you to have a look at the papers I mentioned before implementing your approach (if at all you have not already done the hard work).