Link capacity upgrade threshold

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1

Date: Sun, 30 Aug 2009 21:04:15 +0900
From: Randy Bush <randy@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.

2

> > 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/

What is this "upgrade" thing you all speak of? When your links become saturated, shouldn't you solve the problem by deploying DPI-based application-discriminatory throttling and start double-dipping your customers? After all, it's their fault for using up more bandwidth than your flawed business model told you they will use.

(If you're not familiar with Bell Canada, it's OK if you don't get the joke).