Section 4.1. Connected and Non-Connected Networks

4.1 Connected and Non-Connected Networks

First, you must decide whether your new network will be fully connected to the Internet. A connected network is directly attached to the Internet and is fully accessible to other networks on the Internet. A non-connected network is not directly attached to the Internet, and its access to Internet networks is limited. An example of a non-connected network is a TCP/IP network that attaches to the outside world via a network address translation (NAT) box or a proxy server. Users on the non-connected network can access remote Internet hosts, but remote users cannot directly access hosts on the non-connected network. Because non-connected networks do not provide services to the outside world, they are also known as private networks.

Private networks that interconnect the various parts of an organization are often called enterprise networks. When those private networks use the information services applications that are built on top of TCP/IP, particularly web servers and browsers, to distribute internal information, those networks are called intranets.

There are a few basic reasons why many sites do not fully connect to the Internet. One reason is security. Connecting to any network gives more people access to your system. Connecting to a global network with millions of users is enough to scare any security expert. There is no doubt about it: connecting to the Internet increases the security risks for your network. Chapter 12 covers some techniques for reducing this risk.

Cost is another consideration. Many organizations do not see sufficient value in a full Internet connection for every desktop. For some organizations, low use or limited requirements, such as needing only email access, make the cost of connecting the entire network to the Internet exceed the benefit. For others, the primary reason for an Internet connection is to provide information about their products. It is not necessary to connect the entire enterprise network to the Internet to do this. It is often sufficient to connect a single web server to the local Internet Service Provider (ISP) or to work with a web hosting company to provide information to your customers.

Other organizations consider an Internet connection an essential requirement. Educational and research institutions depend on the Internet as a source of information, and many companies use it as a means of delivering service and support to their customers.

You may have both types of networks: a non-connected enterprise network sitting behind a security firewall, and a small connected network that provides services to your external customers and proxy service for your internal users.

Unless you have carefully determined what your needs are and what an Internet connection will cost, you cannot know whether connecting your entire network to the Internet is right for your organization. Your local ISPs can give you the various cost and performance alternatives. Ask them about services as well as prices. Some ISPs specialize in providing low-cost service to home users. They emphasize price. However, if you are connecting a full network to the Internet, you may want an ISP that can provide network addresses, name service, web hosting, and other features that your network might need.