Link capacity upgrade threshold

Sun Aug 30 16:22:59 UTC 2009

> Date: Sun, 30 Aug 2009 21:04:15 +0900
> From: Randy Bush <randy at psg.com>
> 
> > If your 95th percentile utilization is at 80% capacity, it's time to
> > start planning the upgrade.
> 
> s/80/60/
> 
> the normal snmp and other averaging methods *really* miss the bursts.

s/60/40/

If you need to carry large TCP flows, say 2Gbps on a 10GE, dropping
even a single packet due to congestion is unacceptable. Even with fast
recovery, the average transmission rate will take a noticeable dip on
every drop and even a drop rate under 1% will slow the flow
dramatically. 

The point is, what is acceptable for one traffic profile may be
unacceptable for another. Mail and web browsing are generally unaffected
by light congestion. Other applications are not so forgiving.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751