[117038] in North American Network Operators' Group
Re: Link capacity upgrade threshold
daemon@ATHENA.MIT.EDU (Nick Hilliard)
Sun Aug 30 08:27:43 2009
X-Envelope-To: nanog@nanog.org
Date: Sun, 30 Aug 2009 13:26:57 +0100
From: Nick Hilliard <nick@foobar.org>
To: Randy Bush <randy@psg.com>
In-Reply-To: <m2ws4l1pa8.wl%randy@psg.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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
