Hi Alejandro >Hi to all of you!!! > >I am a Computer Science student trying to do the pre-grade thesis. I am trying >to develop a free software tool to help administrators to control the >traffic. Right now this tool is based on tc and iptables. >I am having some problems trying to understand tc and tc examples: >- Why in almost every list of tc rules based on htb class, there is > a "tc qdisc dev ... root ... htb default ..." as a root node? > Is it mandatory to work with htb class? It is not mandatory to attach a HTB qdisc to the root. You can attach it to any classfull qdisc's cass. You can only create HTB classes under a HTB qdisc, and you can only create CBQ classes under a CBQ class. However you can attach any qdisc to a given class. What is exactly that you find strange? >- I understood that every class node has its own qdisc attached > (fifo by default, right?). Correct. To be exact, most qdiscs use Packet FIFO (pfifo) by default, but that's not a rule (there are exceptions). >If that is the case, why when I do "tc qdisc show ..." it >JUST shows me those qdisc I explicitly attached to classes without any child >class? The default pFIFO qdisc that get attached to the classes are not shown by the above command. >- What should I expect if I run something like this? > >tc qdisc add dev eth0 root handle 1: htb default 10 >tc class add dev eth0 parent 1: classid 1:1 htb rate 100mbit >tc class add dev eth0 parent 1:1 classid 1:10 htb rate 90mbit >tc class add dev eth0 parent 1:1 classid 1:20 htb rate 1kbit >tc class add dev eth0 parent 1:20 classid 1:21 htb rate 10mbit > >I guessed the traffic redirected to 1:21 should have 1kbit of rate at most >(because of its parent 1:20), but when I ran this, I got a higher rate >(because of the 10mbit rate, I guess). Why? Shouldn't parent classes restrict >children's rate? I would say that that is a misconfiguration. Neither the tc command nor the kernel gives you any warning. You could implement it as part of your project ... :) You are right. Class 1:20 does not limit the class 1:21's rate to 1kbit. This is due to the way the kernel schedules the HTB classes. Note that since you did not use the "ceil" config option, class 1:21 gets by default "ceil" = "rate" = 10mbit, and therefore it can not borrow from its parent 1:20. There would be nothing to borrow anyway, since 1:20 is limited to 1kbit (rate=cel=1kbit). Regards /Christian [http://benve.info] _______________________________________________ LARTC mailing list LARTC@xxxxxxxxxxxxxxx http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc
