traffic shaping and fixed per-packet overhead

traffic shaping and fixed per-packet overhead

[Matthias Urlichs]

Hi,

I have an IPIP tunnel through a DSL line (PPPoE) which I need to
traffic-shape / flow control. Unfortunately, the tunnel has a fixed
per-packet overhead, which means that small packets overrun the
bandwidth allowed for the tunnel and get dropped, while (if I set the
allowed bandwidth to too-small values) the wire will be idle when
I send large packets.

(I'm using HTB.)

I can think of a couple of solutions ...
- Use bit-banging in the outer filter instead of nice rules on the tunnel.
  (OK, that's a dumb idea from a useability POV.)
- Extend the HTB code to allow specifying a per-packet overhead.
- Hack the kernel to propagate a packet's netfilter MARK.

Other / better ideas?

-- 
Matthias Urlichs  |  {M:U} IT Design @ m-u-it.de  |   smurf@smurf.noris.de
Disclaimer: Das Zitat wurde zufällig ausgewählt.  |   http://smurf.noris.de
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Mußt Du immer meine Fragen, die ich immer schon stellen
wollte, beantworten, _bevor_ ich daran dachte, sie zu äußern.
		-- Gerold Korbus über Joey

Re: traffic shaping and fixed per-packet overhead

[Patrick McHardy]

Matthias Urlichs schrieb:
> Hi,
> 
> I have an IPIP tunnel through a DSL line (PPPoE) which I need to
> traffic-shape / flow control. Unfortunately, the tunnel has a fixed
> per-packet overhead, which means that small packets overrun the
> bandwidth allowed for the tunnel and get dropped, while (if I set the
> allowed bandwidth to too-small values) the wire will be idle when
> I send large packets.
> 
> (I'm using HTB.)
> 
> I can think of a couple of solutions ...
> - Use bit-banging in the outer filter instead of nice rules on the tunnel.
>   (OK, that's a dumb idea from a useability POV.)
> - Extend the HTB code to allow specifying a per-packet overhead.
> - Hack the kernel to propagate a packet's netfilter MARK.

Totally unrelated to netfilter-devel, but:

# tc qdisc add htb help
...
  mpu      minimum packet size used in rate computations
  overhead per-packet size overhead used in rate computations