Link capacity upgrade threshold

Tom Sands tsands at
Sun Aug 30 09:06:39 CDT 2009

If talking about just max capacity, I would agree with most of the 
statements of 80+% being in the right range, likely with a very fine 
line of when you actually start seeing a performance impact.

Operationally, at least in our network, I'd never run anything at that 
level. Providers that are redundant for each other don't normally 
operate above 40-45%, in order to accommodate a failure.  Other links 
that have a backup, but don't actively load share, normally run up to 
about 60-70% before being upgraded.  By the time the upgrade is 
complete, it could be close to 80%.

Tom Sands			  						
Rackspace Hosting	    	       	   	

William Herrin wrote:
> On Sat, Aug 29, 2009 at 11:50 PM, devang patel<devangnp at> wrote:
>> I just wanted to know what is Link capacity upgrade threshold in terms of %
>> of link utilization? Just to get an idea...
> 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.
> If you average or median utilizations are at 80% capacity then as
> often as not it's time for your boss to fire you and replace you with
> someone who can do the job.
> Slight variations depending on the resource. Use absolute peak instead
> of 95th percentile for modem bank utilization -- under normal
> circumstances a modem bank should never ring busy. And a gig-e can run
> a little closer to the edge (percentage-wise) before folks notice
> slowness than a T1 can.
> Regards,
> Bill Herrin

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