On Tue, 4 Apr 2006, Keith A. Glass wrote:

> . . . .Here's my situation:
> We're currently spec'ing functional requirements for a new web-based
> implementation of a number of enterprise apps. One obvious problem is the
> firewall system: it needs to be both load-balancing and high-availability,
> AND scalable. We're still getting a feel for potential traffic, but we
> expect to have a requirement for in-line expansion of the system while
> remaining online.

high-availability is easy to understand the requirements for.

load-balancing is only a requirement from a marketing/management point of
view unless you can define your third point

scalable. scaleable to what? are you talking an Internet connection where
you have a need for multiple T-1 lines? multiple DS-3 lines? multiple
OC-12 lines? or are you talking local networks where you have 100Mb
ethernet? or gig ethernet? or 10gig ethernet? are you talking just a
couple of these networks or are you talking about dozens of these

as others noted load balanceing is seldom needed for technical reasons,
and it's impossible to answer anything about scalability without knowing
what sort of scale you are talking about. In most cases a single
high-capacity box (plus HA backup) can easily handle the full load, and
the percentage of cases like this is growing as boxes get faster (which is
happening at a faster rate then the communications links)

sorry for the rant, but you managed to hit one of my current sore points
(I just got out of a meeting with an engineer who claimed that we couldn't
do something becouse of the huge load that it would cause, when that load
consisted of one extra network hop for one out of hundred connections :-/

David Lang

There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies.
-- C.A.R. Hoare

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