One-element vs two-element design

Sat Jan 17 20:02:08 UTC 2004

[stuff snipped]

> but the overall system reliability is much higher than a reliable network
> since a component failure does not equal a functional failure.

s/reliability/availabilty.

You meant reliability when comparing a 1 vs 2 engine airplane, but a 
network (from a customer point of view) isn't defined by reliability, 
its defined by availability.

If you are using your backup (N+1) router(s) for extra capacity, than 
you don't fail back to full capacity, but you do have limited availabilty.

Availability/Performance of the overall system (network) is what we all 
engineer for. Customers don't care about reliability as long as the 
first two items are not impuned. (For example, they don't care if you 
have to replace their physical dialup port every hour on the hour, 
provided that they can get in and off in between service intervals --not 
a very reliable port, but a highly available network from the customer 
perspective).

Maybe I am just picking on semantics.

Deepak