[66623] in North American Network Operators' Group
Re: One-element vs two-element design
daemon@ATHENA.MIT.EDU (Deepak Jain)
Sat Jan 17 15:03:57 2004
Date: Sat, 17 Jan 2004 15:02:08 -0500
From: Deepak Jain <deepak@ai.net>
To: Scott McGrath <mcgrath@fas.harvard.edu>
Cc: Brent_OKeeffe@asc.aon.com, Timothy Brown <tim@tux.org>,
nanog@merit.edu
In-Reply-To: <Pine.LNX.4.58.0401171423170.30471@ls02.fas.harvard.edu>
Errors-To: owner-nanog-outgoing@merit.edu
[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
