In selecting an Internet Server Provider, or a Web, or application hosting company, you are faced with the task of evaluating how well that ISP can meet your business's needs. When you use one of these providers, essentially you are outsourcing some of your networking infrastructure. Companies go down this road for any one of a number of reasons. Among the most commonly stated reasons are better uptimes as guaranteed by your Service Level Agreement or SLA, an ability to grow on demand seamlessly (and capture more business and profit), superior technical support, better security, and so on.

You can't just depend on anecdotal information or recommendations from selected clients, because if the service fails and your company suffers a considerable loss, your neck could be on the line. So some thought about the selection process will help you go a long way.

First, if your ISP has survived the rather brutal shakeout in this field and is healthy, that says a lot about the company. You are going to pay for different levels of uptime different amounts, so your first question should be: "How much performance do I really need." Don't buy five 9's performance (99.999%) when you only really need (99.9%). Work the numbers and you find that in the former case you are asking for no more than 5 minutes of downtime (a server reboot or two), while in the latter case you are asking for a little more than 52 minutes a year. If your site is a banking transaction that processes millions of dollars of transaction or is required for a life or death service (mission critical), than five nines is for you. However, a messaging application can get by with three nines or less.

If your intended ISP has known Web sites, for example, there are several measuring services that will tell you what uptime that site has achieved. That's a reality check from what the ISP salesperson is telling you. Uptime is only one part of the issue; another issue is response times. If your site is up, but sluggish, you may not achieve your performance objectives. Measuring services also report response times as well. Many ISPs connect to a major backbone, but a few connect to multiple backbones for better load balancing and fault tolerance.

Barrie Sosinsky is president of consulting company Sosinsky and Associates (Medfield MA). He has written extensively on a variety of computer topics. His company specializes in custom software (database and Web related), training and technical documentation.