Although users think of the Internet as a single giant network, it is not.
Instead, the Internet uses a network of networks approach in which thousands of computer networks are inter connected by routers. Each host attaches to one of the individual networks.
Software on the routers allows a host to exchange packets with any other host. Thus, when a computer on one network communicates with a computer on another network, it sends packets through a router.
Software on routers gives the appearance of a single, unified communication system.
The router architecture
Because a given router can interconnect networks that use different hardware technologies, the router architecture permits the Internet to accommodate multiple types of network.
Choice of network technology
Whenever a group installs a network, the group can choose a network technology that is best suited to their purpose. The group then uses a router to connect their network to the rest of the Internet.
In particular, a given network can be wired or wireless, a LAN or WAN, and can have many hosts attached or a few hosts attached. In fact, a network used merely to connect other networks may not have any hosts attached.
Importance of connecting multiple types of networks
Connecting multiple types of networks is important for two reasons.
- First, because the Internet connects many organizations of diverse size, networking needs, and budgets, the organizations use diverse network technologies.
- Second, and more important, networking technologies continue to change. Many of the hardware technologies currently used in the Internet did not exist when the Internet began, and many technologies in use now will be replaced in the future.
Examples of changes in technology
For example, leased lines have been around since the 1970’s but their speeds were a lot slower then. Since then, access data rates have evolved dramatically to speeds of up to 10Gbit/s in the early 21st century. Consequently, leased line prices have also dropped during this time to meet continued market demand.
Another example of advances in connectivity are Wiresless networks which were not invented when the internet was created.
Using a network-of-networks approach keeps the Internet extremely flexible by allowing any given network to be upgraded at any time. The Internet would not have survived if a single technology had been used.