Vas Péter wrote:
Typically you'll have a few mbps capacity on the ADSL link, and
100mbps on LAN. So why would you want to use queues to limit things
on a 100mbps network, when it's already passed through a much smaller
link?
Simple answer: Flow control.
By using queues on the interface toward the LAN, you can control the
speed of TCP sessions for example. You can't control the traffic
going across the ADSL link (without control of a upstream router)
directly, but you can slow the TCP connection down by setting up
queueing on the LAN interface. The result is admittably a poor hack
compared to controlling the other end-point of the ADSL link, but it
does the trick.
The trouble comes when you use the router as a gateway for multiple LANs to one WAN. If
you put a queue on the LAN connections to try to control the inbound WAN connection,
you'll find that you are also throttling the traffic BETWEEN the two LAN connections to a
maximum of the speed of the WAN connection.
Also, if you have two LAN connections (LAN and DMZ) then queuing on the outbound side
of their interfaces fails to limit the WAN speed -- the two LAN interfaces do not _share_
bandwidth, they each think they have the amount of bandwidth as allotted to their queue.
This will be _twice_ the aggregate bandwidth that the WAN side actually has, and will make
queuing impossible to use for managing the speed of the WAN side.
I believe that this indicates that PF needs the ability to queue on the inbound side of
an interface. Numerous people have told me that this is not necessary, but have not been
able to explain how to make flow-control work properly with one slow WAN interface and two
fast LAN interfaces.
Throw NAT into the situation, and it gets even worse.
I'd be thrilled to be proved wrong.
Terje
--
Chris 'Xenon' Hanson | Xenon @ 3D Nature | http://www.3DNature.com/
"I set the wheels in motion, turn up all the machines, activate the programs,
and run behind the scenes. I set the clouds in motion, turn up light and
sound,
activate the window, and watch the world go 'round." -Prime Mover, Rush.
