Adam wrote:

> If you are intending to deliver your application over an unstable
> network, then I would suggest that a "client-server" approach will not
> work very well. Better off choosing some n-tier architecture.

In the early days of using Frame Relay provided by British Telecom we
had no end of trouble getting a reliable network, which we were told was
down to the software. The major problem was maintaining operation on the
remote sites, so a copy of Interbase at that time was loaded on every
site ( Firebird created a LARGE saving in license fees ). All the local
applications ran from the local copy, and we used messaging to signal
updates back and forth to the main server. If a connection could not be
made for an update, then the local machine carried on running, but just
kept retrying to get an answer until a time out period after which the
local machine would change the platform displays to provide just general
information. The arrangement was so efficient that we were using less
than 1% of the available bandwidth - which was 64kb links to each
station, and 2Mb at the control center. We still had problems with
reliability, very infrequently, but then a new engineer arrived at BT
and once he ACTUALLY configured THEIR modems all our problems went away.
They never did pay any compensation for the 6 months of work spent
trying to fix a problem in the software that did not exist :( but since
the resulting system was using so little bandwidth, and they were paid
by usage the customer saved a lot of money over the last few years :)

This was STILL running IBO3, so the application stuff is not the
problem. I just had two connections, one local - which if there are
problems with that then you need to change computer suppliers - and one
which is checked and dropped at regular intervals connecting to the
remote server. So you CAN make an almost stable system even when the
network is working against you, and with Firebird and IBO4 things would
be even better on our older setup - but the customer has moved on from
that now, and Frame Relay has been replaced by a broadband network.

--
Lester Caine
-----------------------------
L.S.Caine Electronic Services
Treasurer - Firebird Foundation Inc.