[Asterisk-Dev] Anyone doing QOS routing on Linux for SIP/RTP?

[Adam Goryachev]

> In my North American-based experience, QOS is overrated.  There are
> exceptions, but in many cases the problem can be traced to "poor
> network engineering", into which the introduction of QOS will only
> throw things further into a meltdown.

The problem with this is that bandwidth is not as cheap elsewhere as it is
in North America... (It is also frequantly metered or byte charged which can
really impact on VoIP costings).

I can see a couple of important area QoS can improve voice quality on a IP
network, I haven't completely set this up yet, but I have 'tested' it
briefly. I have my office PBX at work (asterisk), and I dial into my office
router when I'm at home using an 64k ISDN. Now I tried using my ATA186
directly to the office PBX which was pretty bad and quickly degraded to
impossible (something about needing around 72kbps and only having 64kbps :))
Anyway, so I install asterisk on my home PC, use IAX across the 64kbps line
with the gsm codec and then my home PC converts back to SIP for the ATA186.
In this instance, I need to be able to ssh to the servers at work, and
browse the internet, and have outlook check my email on a regular basis
*while* I am on the phone, and preferably without any issues with the voice.
Which means if outlook decides to auto-check my email and download a 5MB
email, I *need* QoS to ensure the voice connection takes priority.

> >Just wondering if anyone out there has done any work, or knows where
> >any work is being done, to try to honor the latency requirements of
> >this VOIP stuff and push out SIP and RTP traffic, etc., "ahead of
> >the crowd."

Well, I have frequantly looked at the linux kernel compile time options for
Advanced Router and the various QoS details below that, but I've never even
attempted to implement them. I would suggest some google searches and
reading... Of course, if you have the equipment, then nothing beats plain
trial and error :) I for one would be very interested to hear your results.

> >I'm doing my VOIP behind wireless, so it is particularly important.
> >I am getting ready to do some digging, and don't want to re-invent
> >the wheel.

I'm not sure how wireless affects QoS ?? It might increase the latency
slightly, but as long as available bandwidth > required bandwidth, there
shouldn't be any issues.

Again, I would be interested to hear more about this as well as I will be
implementing a large-ish multi-site PBX using a wireless link soon...

Regards,
Adam

Adam Goryachev
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