North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: Testing Bandwidth performance

  • From: Valdis.Kletnieks
  • Date: Wed Jun 26 01:19:09 2002

On Wed, 26 Jun 2002 01:02:29 EDT, Martin Hannigan <hannigan@fugawi.net>  said:

> Whatever happened to using NTP between sites? Works well if you have
> clocks at each site. Sorta works on strat 1/2 no clock.

That will give you latency for a specific fixed packet size, which may not be
at all correlated with actual bandwidth.  You basically end up having to 
assume that any jitter in the RTT is based on queues in the routers along
the way and from that extrapolate what the bandwidth was.

And of course, the first time you hit a provider that does traffic engineering
that moves NTP packets to the front of the queue so as to minimize the jitter,
the measurement becomes useless for bandwidth management...
-- 
				Valdis Kletnieks
				Computer Systems Senior Engineer
				Virginia Tech

Attachment: pgp00021.pgp
Description: PGP signature