Does ns3 nodes acts upon the Type of Services(TOS) bits in the header by default

[Joyanta Biswas]

Hello,

For the last few days I am really having a tough time figuring out how this Type of Services(TOS) business really works in ns3. I did some code where the topology is like the following:

//  n0                                        n4
//     \ 5 Mb/s, 2ms                    /
//      \          1.5Mb/s, 10ms    /
//       n2 -------------------------n3
//      /                                     \
//     / 5 Mb/s, 2ms                   \
//   n1                                     n5

Where n0 generate flow (destination n4),with the TOS 184, which expects expedited forwarding (EF) service, and n1 generates flow (destination n4) with TOS value 0x70 (which is AF32). The packet tagging was done correctly as I have seen the pcap and xml files to verify that.

But when I run the program, I see both flows experiencing almost equal delaysum! I am not sure how is that possible, as the flow generated by n0, represents expedited forwarding, and the delay should be much more smaller than the other one.

Then I make change the n1 to generate AF32 traffic and n0 to generate EF traffic, but the result remains same. From this, it seems like the intermediate nodes (n2--n3) are not behaving appropriately. Should I need to go for different queuing mechanism to implement that?

I have attached my code. Please let me know whether anything wrong with my code. I am using ns3 version 3.30.1.

Thanks for your time.

Best

Joyanta