Tuning bandwidth throttling

English Network/Internet
1

Hi

I have a box with SuSE-11.1 as a router and a switch on the LAN side giving internet access to a bunch of users. On the external side is a very lousy ADSL with approx. 77K/s downstream and 50K/s upstream. In order to speed up interactive connections using ssh I have installed bandwith throttling with a script like this: The Ultimate Traffic Conditioner: Low Latency, Fast Up & Downloads

First: It works very well for speeding up interactive connections and it does balance service for different users in the LAN fairly well. However I need some advice in tuning the parameters to get the most out of my bandwith.

tc -s qdisc show dev eth1 (eth1 being the WAN side)

qdisc cbq 1: root rate 100000Kbit (bounded,isolated) prio no-transmit
Sent 36244434 bytes 61636 pkt (dropped 0, overlimits 22896 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
borrowed 0 overactions 0 avgidle 78 undertime 0
qdisc sfq 10: parent 1:10 limit 127p quantum 1506b perturb 10sec
Sent 1879720 bytes 30767 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
qdisc sfq 20: parent 1:20 limit 127p quantum 1506b perturb 10sec
Sent 34364714 bytes 30869 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
qdisc ingress ffff: parent ffff:fff1 ----------------
Sent 61937366 bytes 79465 pkt (dropped 1414, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0

tc -s class show dev eth1

class cbq 1: root rate 100000Kbit (bounded,isolated) prio no-transmit
Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
borrowed 0 overactions 0 avgidle 78 undertime 0
class cbq 1:1 parent 1: rate 360000bit (bounded,isolated) prio 5
Sent 36244170 bytes 61635 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
borrowed 5669 overactions 0 avgidle 78 undertime 0
class cbq 1:10 parent 1:1 leaf 10: rate 360000bit prio 1
Sent 1879720 bytes 30767 pkt (dropped 0, overlimits 153 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
borrowed 1 overactions 103 avgidle 78 undertime 0
class cbq 1:20 parent 1:1 leaf 20: rate 324000bit prio 2
Sent 34364450 bytes 30868 pkt (dropped 0, overlimits 24210 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
borrowed 5668 overactions 5955 avgidle -23816 undertime 58066

Question is how to interpret those borrowed / overactions / avgidle / undertime values and tune the speed parameters accordingly to optimize throughput.

Any hints would be appreciated.
Regards, Thomas

2

You’d have to read the mathematical explanation of how traffic control works, what those metrics mean, then work out which knobs to turn and experiment a bit. There should be links in the LARTC to technical papers.

If this doesn’t sound very helpful it’s because TC is really is fairly complicated, and even I would have to relearn all this stuff if I wanted to do it again. Scripts of necessity make a lot of simplifying assumptions which may or may not suit your situation.

3

Hi

Thanks a lot. You’re helpful insofar as I know now that I’m pretty much on my own here. I’m one of those old fashioned guys who does read the manuals and in fact I studied LARTC and the tc manuals but I was unable to gain much insight on how to tune, as there are a bunch of parameters and this makes a trial and error method almost impossible. I may have to read the source code (that’s what open source is good for!).

Anyone out there who knows whether HTB works together with tc and SuSE-11-1 (32Bit) without recompiling the kernel?

Thomas

4

IIRC Hierarchical Token Bucket is just one of the controllers that can be plugged into the TC framework, probably the best known one. I don’t know if you need to roll your own kernel on openSUSE to have TC, but if it’s already working, then chances are it’s compiled in or available as a module.