Re: [LARTC] Shared ADSL SHAPER

[Andy Furniss <andy.furniss@dsl.pipex.com>]

Rasmus Melgaard wrote:
> Hi,
> 
> I'm trying to make a shaper / firewall to improve sharing of bandwidth on a 
> ADSL (3mbit down / ½ mbit up)
> 
> Since the ADSL is very asymmetric, down is unimportant, I make a ingress rate 
> limit shaper to ensure, all shaping is at the Shaper, and not on the Router 
> or the ISP.
> 
> The Idea is then to make one HTB hierarchy and have each client (IP) filtererd 
> and put in a child-HTB queue. This is the main idea, I have added prio to 
> each HTB-child to keep priorities for each client.
> 
> I currently use a reduced setup with total-uplink limited to 160kbit, and i 
> run first the firewall script (first) and then the Shaper script, below.
> 
> The problem is know that if a take Azureus, bittorrent client, and let it go 
> (no uplink limitation), it now kills its own downlink speed. If I limit the 
> uplink speed in Azureus the downlink will grow again, it is quiet obvious. 
> 
> I've tried adding some trick from the net, to especially improve ACK 
> performance, but it hasn't helped.

I haven't checked the script but assuming it's OK I think that this 
could be fixed - I use the python client and it seems OK.

When you back off you will get fairness from the client - so you should 
use sfq.

You will need to priorotise small packets - I use < 128.

You also need to limit the length of the sfq to say 20 - 30 so that you 
get plenty of drops and less acks for the download get piggybacked on 
the upload packets - bittorrent uses tcp full duplex which makes it a 
bit of a special case for shaping.

Always remember that unless you patch/use overhead parameters that you 
need to back off from the advertises link rate.

Andy.
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