Into.the.Void.

On my previous post, more netroute2 hacks – high availability, one of the changed files was the dial_conn file. At the end of the diff there was a line with a # in front:
+ sleep 5
+ #/etc/bin/wshaper ppp0 192 1024

Inside netroute2 one can find the /etc-ro/ppp/wshaper file which is the traffic shaping script of the modem/router. Unfortunately it resides in the read-only section of the router so you can’t make changes directly to it. What I did was to make a copy of it on the writable /etc/bin/ and change a line in my /etc/bin/dial_conn to call it from there, right after (5 seconds later) the connection with the ISP has been established.

If you have followed the previous post about high availability the only thing you need to change is to edit your /etc/bin/dial_conn file and remove the # from the live above. Else…read the previous post 🙂

The first argument of the script is the device the rules will apply to, the second argument is the upload speed and the third is the download speed. Netroute2’s own traffic shaping script gets the 3 arguments while syncing with the dslam. The problem with adsl lines here in Greece, and I guess in many other countries as well, is that the speed the modem syncs with the dslam has nothing to do with the real speed you actually get. So shaping for 256kbit upload while never reaching more than 200 is a bit foolish imho. What I did was lower the upload so that I am always (or mostly always) sure that this is my max upload speed at the time. I can now create rules based on the assumption that my upload speed is 192kbit. If the upload speed your modem syncs is 192kbit I would advise you not to put more than 128kbit as the first argument. It’s a trial and error situation.

While lowering my shaped upload speed and keeping the rest of the script intact already made a difference I knew that I could do some more tweaking.
The first thing one has to know before creating any traffic shaping script is to learn what the TOS field is:

#TOS FIELD
# 0x10 – (minimize delay)
# 0x08 (maximize throughput),
# 0x04 (maximize reliability),
# 0x02 (minimize cost)
# 0x00 (best effort)

You can then create rules with iptables to change the TOS field of certain packets, for example:
$IPTABLES -t mangle -A POSTROUTING -o $DEV -p tcp --syn -m length --length 40:68 -j TOS --set-tos 0x10
$IPTABLES -t mangle -A POSTROUTING -o $DEV -p tcp --tcp-flags ALL ACK,FIN -j TOS --set-tos 0x10


A great rule to add to any of your scripts is to speed up ACK packets,(2) by adding them to the highest priority class (on netroute2 that’s 1:10):
$TC filter add dev $DEV parent 1: protocol ip prio 1 u32 \
match ip protocol 6 0xff \
match u8 0x05 0x0f at 0 \
match u16 0x0000 0xffc0 at 2 \
match u8 0x10 0xff at 33 \
flowid 1:10


What is also very very helpfull is to specify the port your torrent client uses (eg 17777) and add it to the lowest priority class (on netroute2 that 1:30):
$TC filter add dev $DEV parent 1:0 protocol ip prio 3 u32 match ip sport 17777 0xffff flowid 1:30
$TC filter add dev $DEV parent 1:0 protocol ip prio 3 u32 match ip dport 17777 0xffff flowid 1:30


Of course you can create your own classes inside /etc/bin/wshaper. If you are carefull enough with the rules you add you will be more than happy with the result 🙂

To monitor how your traffic shaping is going you can download a great perl script from here: http://qos.kallenberg.dk/ called qos.pl. This script reads a machine’s qos classes and priorities and creates graphs like the ones on the site. The problem with netroute2 is that it doesn’t have perl included, so one has to modify qos.pl to make it read netroute2’s qos performance while running from another machine. This is done by making the script run its commands through ssh-ing to netroute2 using public key auth. If you don’t know how to enable this on netroute2 please read part F of my older post: Intracom netroute2 hacks/.

What you need to change on the qos.pl script is:
a) change the $tc line with something like this:
$tc = "ssh root\@NETROUTE2.IP.GOES.HERE /usr/sbin/tc";
b) Find any occurances of “eth2” and replace with “ppp0” (there must be 2 occurances only).

now run the qos.pl script and it will start creating some graphs (png files) and an index.html on the directory from which you executed it. qos.pl depends on gnuplot, so you must install it before you run it.

The graphs are a great visual aid to to tweak your new traffic shaping script more and more.

Filed by kargig at 04:33 under Internet,Linux,Networking
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