This is a common question faced by many companies wanting to connect multiple seperate work sites together on one network. This is commonly called a WAN (Wide Area Network). A one site network is commonly called a LAN (Local Area Network).

A WAN may cover sites within a few miles of each other ... as in locations in the same town/city ... or even different towns/cities but the same state. Or it could connect sites in multiple different States.   Seperation of physical locations is the key to the definition.

What follows is not meant to be a detailed plan of action with all the bells and whistles .... and calculations and negotiations. It's simply a start to get you thinking and organized ... and off in the right direction.

First start by asking yourself which applications you need to run over the link. People don't buy networks, they buy access to applications. Will it involve multi-media and large file transfer? Will it include both voice and data exchanges? Or will it be simple file and email communication?

Then you need to look at the expected usage over the link. The profile of the applications is also important -- are they latency constrained? Are they bandwidth hogs? Is it sporadic access or sustained? Are you bringing Internet over the link?
How far apart are the sites? Will that introduce latency? Is that latency going to be a problem?

You also have to look at what you can get. Maybe all you can get is a T1 line at 1 or more locations. What is available from providers at the locations you need served? Is ethernet an option?

What do your bandwidth calculations based on application and usage indicate? Will a DS3 circuit cover the load requirements?

Do providers available to service the locations in question offer a MPLS network solution (Multi-Protocol Label Switching)?

What is the budget you have dedicated to the project? Don't let cost limit your decision though. You can find very cost effective solutions and special deals to fit any economic constraints ... with a little help. Meeting your application and communication requirements is more important to your bottom line than buying solely on price.

When considering any firewall issue remember that it is a security thing. If all locations are branch offices of the same company, maybe a firewall will cause more problems than it solves.

Depending on the answers above, you might also need to look at WAN acceleration, Citrix, or other such technologies to get around application limitations. Some applications just don't work well when they're separated by their users by more than a few milliseconds.

If you're at the director level, this might be a more appropriate task for one of your staff to run down (IT or Telecommunications if you have them). If you're one of those directors-with-zero-reports type people, you may consider engaging a consultant.

You want to make sure this is done right, as the cost of the connection may be significant over the course of the contract. Use of a consultant (especially those who offer such services at no cost) ... will help you save in both the short and long term. Some consultants have relationships and other information not readily available to you or the general public. Such as unadvertised special pricing, design options which deliver the required performance but are more cost effective, and knowledge of the appropriate SLA (Service Level Agreement) and QoS (Quality of Service) to be expected from the available vendors for the specific sites.

Although this is a common question the results can vary. You want to follow the above guide getting started so as to limit the variance of the results for your business .... and arrive at the best network bandwidth solution for your needs.