How to achieve application reliability

Sigh, when you have a hammer everything looks like a nail.

There are several different ways to achieve 99.99% application reliability
which do not require 99.99% network reliability.

In your credit card application, the keyword I see is "gateway." This implies
there is already some seperation between the front-end and a back-end application. One method to improve application availablility is have multiple
gateways spread around on different networks, instead of depending on a single
gateway being multi-homed. Clients could find a working gateway in several
different ways, pre-configured addresses, DNS and multiple A records, an
application specific discovery protocol. "Its only a small matter of

This works best for applications with very small address requirements, such
as your credit card company which wouldn't qualify for a /19 or /20 from
ARIN. It doesn't make sense for larger address use applications, since it
essentially requires addresses be duplicated N times.

While this lowers demand on routing table entries, it increases demand for
addresses. Depending on which one people think we will run out of first,
will change your point of view.

Pick your trade-off.

You're absolutely right Sean. Actually, "gateway" is probably a bad
choice of words. This particular credit card processor
( didn't work behind the scenes, it used a front-end.
In order to use them, a merchant would have a hyper link to the
internetsecure web site. So the consumer would actually have to go to
internetsecure to type in the credit card. The problem with Round-Robin
DNS is the possibility of the consumer's web browser picking up an IP
address of a server that is down. If it was a real payment gateway, your
suggestion would work great. Unfortunately, the Canadian banks put some
weird "restrictions" on how we could do things. Another "restriction" is
we couldn't colocate for security and maintanence issues. I'm sure
everyone can sympathize with the difficulties politics can sometimes play
with technical issues. :slight_smile: