[LARTC] Newbie STILL trying to limit bandwidth - is this script wrong?

[Jason Boxman]

On Monday 24 May 2004 18:37, George Adams wrote:
> My previous message
> (http://mailman.ds9a.nl/pipermail/lartc/2004q2/012285.html) didn't generate
> any replies, so I thought I'd try posting what I've done trying to solve my
> own problem, in hopes that someone will take pity and show me if/where I'm
> going wrong.
>
> Just to recap, I'm trying to accomplish this on my server, which streams
> RealAudio files and allows HTTP downloads of large files.
>
> 1) SSH connections (port 22) (i.e. me connecting remotely) should get all
> the bandwidth they can consume (highest priority).
>
> 2) RealAudio streaming clients (port 554) should get all the bandwidth left
> after #1 that they can consume.
>
> 3) Web downloaders (port 80) should get all the bandwidth left after #1 and
> #2 that they can consume (lowest priority).
>
> I've tried adapting an existing tcng script into this:

I had little success using TCNG, although it was a nice tool to use and the 
ruleset is easy and straight forward.

I am having considerable, nearly out-of-the-box success using IPTables with 
the CLASSIFY extension (for 2.4 and 2.6) and a few raw `tc` commands to 
create the actual shaping classes.

<snip>
>         class ( <$ssh> ) if tcp_sport == 22 ;
>         class ( <$audio> ) if tcp_sport == 554 || tcp_sport == 7070 ;
>         class ( <$web> ) if tcp_sport == 80 ;
>         class ( <$other> ) if 1 ;

           ^^^^^^^^^^^^^
You grab those with IPTables and CLASSIFY, or if you really must, you can just 
use the MARK target and some extra `tc` filters to catch those marks.

>         htb () {
>             class ( rate 600kbps, ceil 600kbps ) {
>                 $ssh = class ( rate  64kbps, ceil 128kbps ) { sfq; } ;
>                 $audio = class ( rate 128kbps, ceil 128kbps ) { sfq; } ;
>                 $web = class ( rate 256kbps, ceil 512kbps ) { sfq; } ;
>                 $other = class ( rate 128kbps, ceil 384kbps ) { sfq; } ;
>             }
>         }

Not too bad:

tc qdisc add dev eth0 root handle 1: htb default 90
tc class add dev eth0 parent 1: classid 1:1 htb rate 600kbit ceil 600kbit


tc class add dev eth0 parent 1:1 classid 1:10 htb rate 64kbit ceil 128kbit
...
tc class add dev eth0 parent 1:1 classid 1:90 htb rate 8kbit ceil 64kbit

SFQ for each:

tc qdisc add dev eth0 parent 1:10 handle 10: sfq perturb 20
...
tc qdisc add dev eth0 parent 1:90 handle 90: sfq perturb 20

Replace 'eth0' with your actual Internet facing interface.

<snip tcc output>
> I've tried loading them into tc, but I'm not really sure if it's working or
> not.  The only way I could think to test it was to get a friend (in another
> state) to trying download 3 files via HTTP, which would normally cause my
> SSH sessions to slow to a crawl.  The 3 downloads started, and it still
> seemed like the latency in my SSH sessions was high (i.e. it didn't appear
> that they had any priority over the HTTP downloads).

SSH is a lot of fun, and it doesn't flag things like tunnels or `scp` with the 
TOS flags that it should, so bear in mind without tweaks you will suffer if 
you perform any of those activities while using any SSH terminal sessions.

Here's a rule to match all outbound packets trying to hit port 80 (i.e. HTTP 
requests by me to external sites):

$IPTABLES -t mangle -A POSTROUTING -o $LOCALIF -p tcp --dport 80 \
  -j CLASSIFY --set-class 1:20

Classify simply assigns it to the correct class, which will be whatever you 
define.  I believe it only works in the POSTROUTING chain, however.

> So am I totally on the wrong track here?  Or am I on the right track but
> just needing some tweaks to my script?
>
> Thanks to anyone who can help - I need it!

Enjoy.

-- 

Jason Boxman
Perl Programmer / *NIX Systems Administrator
Shimberg Center for Affordable Housing | University of Florida
http://edseek.com/ - Linux and FOSS stuff