mailing list archives
RE: VoIP QOS best practices
From: "Ray Burkholder" <ray () oneunified net>
Date: Mon, 10 Feb 2003 13:25:32 -0500
Ok, I've taken all the courses and done some stuff myself.
Here is roughly what to expect.
It IS important to do QoS at the CPE. This ensures that during times of
congestion, voice traffic gets out to the real world in a timely
In networks supported by Nanog people, usually they have bandwdith to
spare, and so QoS isn't necessarily important. The issue is when
traffic crosses ISP boundaries, because many times these links are
clogged. It used to be you had to stay away from MAEWEST and such
because of big packet drops and delays (big no-no's for voice). Things
are getting better in this regard because of a larger number of cross
connects between carriers.
General rule of thumb used by the big Voip guys is to send most of your
voip traffic through what could loosely be termed as Tier 1 providers
(please don't flame me on this remark). They you can be pretty sure
that there is much excess bandwidth, fast switches, and fast transit
time with little drop out (all important criteria for good voice
The issues are always when crossing carriers, and at the network edge.
These are the troublesome spots. Some solutions include peering with
multiple Tier 1 providers, and doing traffic engineering to ensure your
traffic goes through the best provider to the end destination, etc, ...
When you get into IP Telphony in a LAN environment I can get into a
whole other discussion of myth dispelling. For example, just because
your LAN switch has underutilized GigE and FE ports, did you know that
you can still suffer horrible voice quality? QoS fixes this in a LAN
enviroment which could be viewed as bursty system where as internet
switches tend to be more smooth flow in nature (if I'm wrong on this
one, I'd like to hear about it).
From: Charles Youse [mailto:cyouse () register com]
Sent: February 10, 2003 14:03
To: Bill Woodcock; nanog () nanog org
Subject: RE: VoIP QOS best practices
That doesn't seem to make a lot of sense - is it that QoS
doesn't work as advertised?
As someone who is looking to deploy VoIP in the near future
this is of particular interest.
From: Bill Woodcock [mailto:woody () pch net]
Sent: Monday, February 10, 2003 12:48 PM
To: nanog () nanog org
Subject: Re: VoIP QOS best practices
> > Looking for some links to case studies or other
> > describe implementing VoIP between sites which do not
have point to
> > point links. From what I understand, you can't
enforce end-to-end QoS
> > on a public network, nor over tunnels. I'm wondering
if my basic
> > understanding of this is flawed and in the case that
it's not, how is
> > this dealt with if the ISPs of said sites don't have
any QoS policies?
QoS is completely unnecessary for VoIP. Doesn't appear to
make a bit of
difference. Any relationship between the two is just FUD from people
who've never used VoIP.
- RE: VoIP QOS best practices, (continued)