[117036] in North American Network Operators' Group
Re: Link capacity upgrade threshold
daemon@ATHENA.MIT.EDU (Mikael Abrahamsson)
Sun Aug 30 01:24:46 2009
Date: Sun, 30 Aug 2009 07:23:57 +0200 (CEST)
From: Mikael Abrahamsson <swmike@swm.pp.se>
To: nanog@nanog.org
In-Reply-To: <3c3e3fca0908292115s12039efch61c0b1138530d814@mail.gmail.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Sun, 30 Aug 2009, William Herrin wrote:
> If your 95th percentile utilization is at 80% capacity, it's time to
> start planning the upgrade. If your 95th percentile utilization is at
> 95% it's time to finish the upgrade.
I now see why people at the IETF spoke in a way that "core network
congestion" was something natural.
If your MRTG graph is showing 95% load in 5 minute average, you're most
likely congesting/buffering at some time during that 5 minute interval. If
this is acceptable or not in your network (it's not in mine) that's up to
you.
Also, a gig link on a Cisco will do approx 93-94% of imix of a gig in the
values presented via SNMP (around 930-940 megabit/s as seen in "show int")
before it's full, because of IFG, ethernet header overhead etc.
So personally, I consider a gig link "in desperate need of upgrade" when
it's showing around 850-880 megs of traffic in mrtg.
--
Mikael Abrahamsson email: swmike@swm.pp.se
