[LARTC] simulating RED using tcsim question

[LARTC] simulating RED using tcsim question

[Stephen Lally]

I'm trying to setup a bottlekneck scenario so I can see the effects of 
the RED qdisc on a congested interface.
My example simulation code is at the bottom of this email if someone 
wants to see it.

The following is a snippet form TCSIMs output.

0.602000 E : 0x80bc080 40 : inputB_eth0: 45000028 00000000 40060000 ...
0.602000 D : 0x80bc080 40 : inputB_eth0: 45000028 00000000 40060000 ...
0.602003 E : 0x80bbfd8 40 : router_eth2: 45000028 00000000 40060000 ...
0.602003 * : 0x80bbfd8 40 : router_eth2: enqueue returns CN (2)
0.602003 E : 0x80bc080 40 : router_eth2: 45000028 00000000 40060000 ...
0.602003 * : 0x80bc080 40 : router_eth2: enqueue returns CN (2)
0.604000 E : 0x80bbfd8 40 : inputA_eth0: 45000028 00000000 40060000 .

As I hoped, packets seem to get dropped as marked by '*' when the 
interface gets congested.

On closer inspection (with -v) tcsim output is:

0.182000 D : 0x80bc0a0 40 : inputB_eth0: 45000028 00000000 40060000 ...
0.182003 E : 0x80bbff8 40 : router_eth2: 45000028 00000000 40060000 ...
0.182003 e : 0x80bbff8 40 : <1> red (2:0) returns CN (2)
0.182003 e : 0x80bbff8 40 : <0> dsmark (1:0) returns CN (2)
0.182003 * : 0x80bbff8 40 : router_eth2: enqueue returns CN (2)
0.182003 E : 0x80bc0a0 40 : router_eth2: 45000028 00000000 40060000 ...
0.182003 e : 0x80bc0a0 40 : <1> red (2:0) returns CN (2)
0.182003 e : 0x80bc0a0 40 : <0> dsmark (1:0) returns CN (2)
0.182003 * : 0x80bc0a0 40 : router_eth2: enqueue returns CN (2)
0.184000 E : 0x80bbff8 40 : inputA_eth0: 45000028 00000000 40060000 ...

I was exspecting the '*' to now print as 'x' to indicate a dropped 
packet rather than some error occuring!

The network setup looks something like this

|inputA_eth0|--100 Mbs------]
                            ]----|router_eth2|---10 Bs------|output_eth1|  
|inputB_eth0|--100 Mbs------]
     
    RED is added router_eth2, router_eth2 is set as a 10 Bs interface to 
force some congestion.


Anyone know what's going on? What does "router_eth2: enqueue returns CN 
(2)" mean?
Any help is much appreciated.

Stephen.


bottleneck.tcsim
-----------------
//inputA to router
host {
        dev inputA_eth0 100 Mbps
}

//inputB to router
host {
        dev inputB_eth0 100 Mbps
}


//the router
host {
        dev router_eth0 100 Mbps
        dev router_eth1 100 Mbps
        dev router_eth2 10 //the bottleneck
        {
                egress {
                        red( min 150 B,
                             max 450 B,
                             burst 200 B,
                             limit 600 B,
                             bandwidth 100 bps,
                             probability 0.4,
                             avpkt 80 B );
                }
        }

        route 10.0.0.0 netmask 255.0.0.0 router_eth2

}

//output destination from router
host {
        dev output_eth0 10 Mbps
        dev output_eth1 100 Mbps
        route 10.0.0.2 netmask 255.0.0.0 output_eth1
}

connect inputA_eth0 router_eth0
connect inputB_eth0 router_eth1
connect router_eth2 output_eth0


every 0.002s until 5s send inputA_eth0 TCP_PCK($tcp_sport = PORT_HTTP);

every 0.002s until 5s send inputB_eth0 TCP_PCK($tcp_sport = PORT_SSH);

time 6s
end



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