[afnog] QoS/TE

[Brian Candler]

On Thu, Jan 19, 2006 at 12:22:48PM +0200, Mark Tinka wrote:
> On Wednesday 18 January 2006 22:57, Brian Candler wrote:
> 
> > When discussing this I made the same points as have
> > been raised here. The response was that even relatively
> > uncongested links, around 20% utilisation upwards, can
> > result in measurable increases in latency and jitter.
> 
> If core links are running at 20% utilization, including 
> the occasional spike in traffic that could send that up 
> to 60% or more for a couple of minutes to a few hours 
> (school-kid gamers back home from school, DoS attacks, 
> breaking news, e.t.c.), with enough bandwidth on the 
> wire, why would you expect an increase in latency if your 
> gear can run the wire at line rate, and you have a good 
> mind to keep utilization under a rough figure, e.g., 75%?

It's variability of latency (i.e. jitter) which is the issue. If utilisation
is at 75%, and you have mostly large packets coming through, mixed in with
some small VoIP ones, the VoIP ones may find themselves at the back of the
queue sometimes and at the front at other times.

Regards,

Brian.