Re: Testing Bandwidth performance

[Valdis.Kletnieks () vt edu]

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

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