Rémi Guyomarch wrote:
>
> On Tue, May 01, 2001 at 07:28:42PM +0000, Gunther Schadow wrote:
> > Rémi Guyomarch wrote:
> >
> > > IIRC you can put a bandwidth limiter on a virtual interface (this is
> > > even the only solution to use ALTQ on tun or ppp devices) and thus
> > > provide a queue which can be managed by ALTQ.
> >
> > Aha! A Light! How is that done? Can you give more specifics?
>
> Look at docs/TIPS.txt in the altq-3.0 release, point 1.9 :
>
> ...
> 1.9 Tun Driver
> Although altq-3.0 supports the tun driver, it is a bit tricky to
> control the tun device.
>
> When ppp transmits packets the tun interface is not a bottleneck
> but the serial port is the bottleneck. As a result, packets are
> queued in the output queue of ppp and the buffer in the kernel
> as shown in the following figure. (a queued packet is shown as X.)
>
> ppp
> app ---+ +-->[ XXX]--+
> | | |
> user | | |
> ==========|==============|===========|=====
> kernel | | |
> | +------+ | |
> +-->| |---+ +->[ XX]--> sio
> +------+ line
> tun0 discipline
>
> To control traffic at the tun interface, rate-limit the tun
> interface by a token-bucket regulator to shift the queueing point
> to the tun device as shown in the following figure.
>
> ppp
> app ---+ +-->[ ]--+
> | | |
> user | | |
> ==========|==============|===========|=====
> kernel | | |
> | +------+ | |
> +-->| XXXXX|---+ +->[ ]--> sio
> +------+^tbr line
> tun0 discipline
>
> Note that ppp usually compress packets so that the throughput at
> the tun interface will be much higher than the line rate.
the above picture is only true for ppp
if you use mpd it is as follows:
>
> app ---+
> |
> user |
> ==========|================================
> kernel |
> | +------+ ppp
> +-->| |---+-->[ ]--+->[ ]--> sio
> +------+^tbr line
> ng0 discipline
>
> ...
>
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