Link capacity upgrade threshold

Nick Hilliard nick at foobar.org
Sun Aug 30 07:26:57 CDT 2009


On 30/08/2009 13:04, Randy Bush wrote:
> the normal snmp and other averaging methods *really* miss the bursts.

Definitely.  For fun and giggles, I recently turned on 30 second polling on 
some kit and it turned up all sorts of interesting peculiarities that were 
completely blotted out in a 5 minute average.

In order to get a really good idea of what's going on at a microburst 
level, you would need to poll as often as it takes to fill the buffer of 
the port in question.  This is not feasible in the general case, which is 
why we resort to hacks like QoS to make sure that when there is congestion, 
it is handled semi-sensibly.

There's a lot to the saying that QoS really means "Quantity of Service", 
because quality of service only ever becomes a problem if there is a 
shortfall in quantity.

Nick




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