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 From:  Mark Ryan <markryan at cfl dot rr dot com>
 To:  Chris Hoy Poy <chrishp at dugeo dot com>
 Cc:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] traffic shaper borrowing
 Date:  Tue, 24 Oct 2006 21:00:37 -0400
Chris Hoy Poy wrote:
> hello again ;)
> You've got pipes and queues.
> my understanding is this:
>  Queues represent possible slices of a pipe. The shaper will try to allow each 
> queue its *minimum* % bandwidth of a pipe, but the queue is allowed to use 
> all of the pipe if its available.
> But pipes represent a hard limit, to my knowledge, and wont borrow from other 
> pipes. You need to do that allocation at the queue level. 
> Rules then allocate actual traffic to each queue. 
> so looking at your question again : if FTP is in the low priority queue and 
> everything else is in the high priority queue, then FTP will use the maximum 
> pipe speed, but will drop back down to its minimum when something else 
> happens.
> Note the one "semi" issue I have seen is where you allocate a pipe to be less 
> then the bandwidth you have available - it seems to use a bucket system to 
> allocate the pipe, so if you allocate a really small pipe (like 512kbit) and 
> you actually have 2mbit of bandwidth there, the pipe will flood the bandwidth 
> for 1/4 of the time available and the actual usage will be very jagged. That 
> may not apply, but I've done it a few times without thinking and found the 
> behaviour (though it makes sense when I think about it) at the time was a bit 
> bizarre. There might be some way to change the interval that the traffic 
> shaper uses? It seems to be set at like 5 or 10 seconds. Having smaller 
> intervals would make the flow a bit smoother, I assume. 
> does that make sense? ;) 
> On Tuesday 24 October 2006 09:44, Mark Ryan wrote:
>> I've been evaluating whether the m0n0wall traffic shaper will work for
>> me and I have to say wow!  It seems very nice.
>> I do have 1 question:
>> Does the traffic shaper use borrowing?  Such as if i have 2 upload ques,
>> ftp assigned to low priority que and everything else assigned to high
>> prio que.  Will the ftp consume the maximum available pipe speed until
>> something in the high prio ques needs it, then i would assume the ftp
>> traffic would slow down until the bw is available again?
>> Sorry for the cryptic question there.
>> Mark
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Yes, makes sense.  That jagged use of bw bothers me though.  Does that 
happen if you set the pipe close to the bw available?

Thanks for the explanation!