How to achieve application reliability

James Smith jsmith at
Sun Dec 5 05:26:28 UTC 1999

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. :-) 

James Smith, CCNA
Network/System Administrator

2140 Winston Park Drive, Suite 203
Oakville, ON, CA L6H 5V5         
Tel:   905-829-3389 (email preferred)
Fax:  905-829-5692
1-877-DXSTORM (1-877-397-8676)

On 4 Dec 1999, Sean Donelan wrote:

> On Sat, 04 December 1999, James Smith wrote:
> > The unfortunate reality is that there are a lot of businesses that need
> > 99.99% reliability and uptime, but aren't big enough to get a /19.  
> > 
> > My previous company was a credit card processing gateway.  If they went
> > down, their customers were screwed.  But they hadn't even used a Class C,
> > so they weren't eligible for a /19 or /20 from ARIN.  
> > 
> > My point is that the current requirement that a network must have a large
> > chunck of IP space to be multi-homed is not ideal.  According to the
> > status quo, while an e-commerce company such as a credit card processor
> > may be big in the business world and worth millions, but insignificant on
> > the Net and left vulnerable because it can't be multi-homed.
> 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
> programming."
> 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.

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