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TODO : Check prio because I think not working

  • What I wanna do

    • When you have a link that's 100% used and you want to do something interactive (telnet), the response time can be very bad. So I want to give the telnet traffic a higher priority.

    To test it, I generate tcp traffic to fullfill the total bandwidth and I start a ping. I don't know it's a good indication, but that's the best I found.

  • First script : prio qdisc

    • The prio qdisc has 3 builtin bands. First everything will be send from the first band and this is all non-tcp traffic (so the pings). All the tcp packets are send secondly. 
    #!/bin/sh
RATE_TOT=100kbps
IP=kriek
 
DEV="dev eth0"
OPTION="allot 1514 maxburst 20 avpkt 1000"

tc qdisc del $DEV root
tc qdisc add $DEV root handle 10: cbq bandwidth 10mbit avpkt 1000
tc class add $DEV parent 10:0 classid 10:1 cbq bandwidth 10mbit rate $RATE_TOT $OPTION prio 3 bounded isolated
 
tc qdisc add $DEV parent 10:1 handle 20: prio

tc filter add $DEV parent 10: protocol ip prio 3 handle 1 fw classid 10:1
tc filter add $DEV parent 10: protocol ip prio 3 handle 2 fw classid 10:1
tc filter add $DEV parent 20: protocol ip prio 3 handle 1 fw classid 20:1
tc filter add $DEV parent 20: protocol ip prio 3 handle 2 fw classid 20:3
 
iptables -F
iptables -X
iptables -N acc_0
iptables -N acc_1
iptables -A OUTPUT -t mangle -p ! tcp -j MARK --set-mark 1
iptables -A OUTPUT -t mangle -p   tcp -j MARK --set-mark 2
iptables -A OUTPUT -p ! tcp -j acc_0
iptables -A OUTPUT -p   tcp -j acc_1

  • Second tests : cbq

    •  In my second tests, I use CBQ to make two classes. One for the tcp traffic and one for the rest.

    Used script (download) I also tried all possible combinations of the prio parameter, but the results didn't change.

  • Results

    • I generated traffic and started 10 pings to measure the response time. These are the results :

      Result
    CBQ With qdisc 11.4 ms
    CBQ With NO qdisc 20: 207.1 ms
    PRIO : ping in band 1, rest in band 1 268.9 ms
    PRIO : ping in band 1, rest in band 3 18.3 ms
    PRIO : ping in band 1, rest in band 5 18.9 ms
    PRIO : ping in band 3, rest in band 1 (X)83 s

    (X) :
    10 packets transmitted, 5 packets received, 50% packet loss
    round-trip min/avg/max = 23233.2/83230.2/143223.3 ms

  • Other tests : telnet session

    • I adapted the script so I can give more priority to telnet traffic on port 23. Of course you can't prove this with numbers, but it was clear that I had a much faster response with the prio qdisc. Same with the cbq script.

    adapted prio script:

    Used script (download)

    adapted CBQ script:

    Used script (download)