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List:       lartc
Subject:    Re: [LARTC] tc ingress policing with multiple subnets
From:       Andy Furniss <lists () andyfurniss ! entadsl ! com>
Date:       2006-06-26 12:33:42
Message-ID: 449FD426.7060804 () andyfurniss ! entadsl ! com
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Nikolay Kichukov wrote:
> Hello everybody on the list,
> 
> I have the following situation where  I want to police the speed of 
> incoming
> packets from specific subnets to 1024kbps and then police all the rest to
> 256kbps, which is the speed my ISP grants for the rest of the internet.

If you are shaping ingress you will need to set a rate below the link 
speed, or you won't do anything.

> 
> So, eth1 is the one connected to the cable modem and then to the internet.
> 
> I do:
> 
> tc qdisc add dev eth1 ingress handle ffff:
> 
> 
> then:
> 
> tc filter add dev eth1 parent ffff: protocol ip prio 1 u32 match ip src 
> xx.yy.zz.0/24 police rate 1024kbit burst 10kb drop flowid ffff:
> tc filter add dev eth1 parent ffff: protocol ip prio 1 u32 match ip src 
> pp.dd.df.0/23 police rate 1024kbit burst 10kb drop flowid ffff:
> ...
> ...
> and finally:
> 
> tc filter add dev eth1 parent ffff: protocol ip prio 2 u32 match ip src 
> 0.0.0.0/0 police rate 256kbit burst 10kb drop flowid ffff:
> 
> 
> My question is, is there a way I can limit the overall speed of incoming
> packets from all of those defined subnets to 1024kbps, as it seems in the
> above scenario that if packets from xx.yy.zz.0/24 subnet arrive at the 
> speed
> of 1024kbps, and at the same time packets are arriving from 
> pp.dd.df.0/23 at
> 1024kbps the overall would be 2048kbps, which I do not want.

You can use a shared meter.

... police index 1 rate ......


> 
> Any comments or suggestions on this topic are welcomed.
> 
> Another question I have is, what is the difference of the burst/buffer 
> being 10kb or 90kb for example? What difference would that make?

The detailed behaviour probably depends on rate estimators in kernel config.

Roughly the burst/buffer is a virtual buffer that when full will cause 
further packets to be dropped until it has drained enough over time to 
pass them again.

If you are shaping ingress at near link speed I think smaller is better 
- if you are shaping well below link speed like 1meg/100 then you can 
use a bigger buffer.

Andy.

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