VoIP QOS best practices

Mon Feb 10 18:19:08 UTC 2003

> -----Original Message-----
> From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On 
> Behalf Of Stephen J. Wilcox
> Sent: Monday, February 10, 2003 12:56 PM
> To: Bill Woodcock
> Cc: nanog at nanog.org
> Subject: Re: VoIP QOS best practices
> 
> 
> 
> On Mon, 10 Feb 2003, Bill Woodcock wrote:
> 
> > 
> >     > > Looking for some links to case studies or other 
> documentation which
> >     > > 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.
> 
> My conclusion too when I looked at this a couple years back. 
> 
> However, its important that the backbone is operating 
> "properly" ie not saturated which I think should be the case 
> for all network operators, theres a requirement tho if the 
> customer has a relatively low bandwidth tail to the network 
> which is shared for different applications, its probably a 
> good idea to make sure the voip packets have higher priority 
> than non-realtime data... (this 
> last comment is a suggestion, I've not actually tested this in a real 
> environment, low b/w lab tests tend to exclude other traffic flows)

I have tested this in lab settings for video over IP (t1 with multiple
384k calls and data) , and came to that same conclusion. While it works
on the tail and needs to be implemented bi-directionally (which never
happens). There is no reason to implement QOS on the Core. Having said
that, there still seems to be too many issues on the tier 1 networks
with pacekt reordering as they affect h.261/h.263 traffic. 

> 
> Steve
> 