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 From:  "Kimmo Jaskari" <kimmo dot jaskari at gmail dot com>
 To:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] Asterisk VoIP Quality Horrible...
 Date:  Thu, 1 Jun 2006 17:59:25 +0300
On 5/10/06, C. Andrew Zook <andrewzook at pdqlocks dot com> wrote:

> I have found this to be a much more difficult problem than you may first
> imagine. I have still not been able to get my traffic shaper totally
> under control with DSL.
>
> In a nutshell, you have to be very careful that your traffic does not
> get queued by your DSL modem.
>
> The best I have been able to figure out is that this is only possible by
> severely limiting your upload and download speeds. What happens is that
> your upload gets maxed out, the modem (or ISP) starts to queue stuff,
> and it is delayed too long for VOIP.

You don't have to severely limit them, you just have to limit
especially the uplink speed to be below the speed of your ADSL uplink.
The objective here is to make sure traffic through the m0n0 is pumped
into the ADSL modem with just a hair below the speed it can output to
the Internet. If you go as much as 1k over that speed, you'll start
filling the queue on the ADSL modem and will se severely increased
latency as a result.

I found one way to, sort of, test where the cutoff limit is. You make
sure you're filling your upload pipe with traffic first so you have
high latency when running a continuous ping to the next IP up from
your modem, the gateway to which it is connected. This would indicate
that your outgoing transfer speed is set too high - the shaper
prioritizes the traffic but the modem is still buffering traffic.

Then just have a continuous ping going from your workstation (on the
local lan, obviously) and start tweaking the uplink speed down in the
shaper with whatever increments you want (5k/sec maybe) and
save/apply. Eventually you hit a point where your ping times drop
dramatically, and that is when you have hit on the setting you need to
shape the traffic.

There may be a more professional way to do this but that works for me,
anyway. Using the magic shaper wizard in m0n0 and then finding your
sweet spot for upload speed should make the voip problems go away. In
theory. ;)

-- 
-{ Kimmo Jaskari }--{ kimmo dot jaskari at gmail dot com }--

Progress isn't made by early risers. It's made by lazy men trying to
find easier ways to do something.
  - Robert Heinlein