Internet architecture

Internet architecture
9.1.7 This page will examine the basic architecture of the Internet.


The Internet enables nearly instantaneous worldwide data communications between anyone, anywhere, at any time.

LANs are networks within limited geographic areas. However, LANs are limited in scale. Although there have been technological advances to improve the speed of communications, such as Metro Optical, Gigabit, and 10-Gigabit Ethernet, distance is still a problem.

Students can focus on the communications between source and destination computers or intermediate computers at the application layer to get an overview of the Internet architecture. Identical instances of an application could be placed on all the computers in a network to ease the delivery of messages. However, this does not scale well. New software would require new applications to be installed on every computer in the network. For new hardware to function properly, the software would need to be modified. Any failure of an intermediate computer or computer application would cause a break in the chain of the messages that are passed.

The Internet uses the principle of network layer interconnection. The goal is to build the functionality of the network in independent modules. This allows a diversity of LAN technologies at Layers 1 and 2 of the OSI model and a diversity of applications at Layers 5, 6, and 7. The OSI model provides a mechanism where the details of the lower and the upper layers are separated. This allows intermediate networking devices to relay traffic without details about the LAN.

This leads to the concept of internetworks, or networks that consist of many networks. A network of networks is called an internetwork, which is indicated with the lowercase i. The network on which the World Wide Web (www) runs is the Internet, which is indicated with a capital I. Internetworks must be scalable with regard to the number of networks and computers attached. They must also be able to handle the transport of data across vast distances. An internetwork must be flexible to account for constant technological innovations. It must be able to adjust to dynamic conditions on the network. And internetworks must be cost-effective. Internetworks must be designed to permit data communications to anyone, anywhere, at any time.

Figure summarizes the connection of one physical network to another through a special purpose computer called a router. These networks are described as directly connected to the router. The router is needed to handle any path decisions required for the two networks to communicate. Many routers are needed to handle large volumes of network traffic.

Figure extends the idea to three physical networks connected by two routers. Routers make complex decisions to allow users on all the networks to communicate with each other. Not all networks are directly connected to one another. The router must have some method to handle this situation.

One option is for a router to keep a list of all computers and all the paths to them. The router would then decide how to forward data packets based on this reference table. Packets would be forwarded based on the IP address of the destination computer. This option would become difficult as more users were added to the network. Scalability is introduced when the router keeps a list of all networks, but leaves the local delivery details to the local physical networks. In this situation, the routers pass messages to other routers. Each router shares information about its connected network.

Figure shows the transparency that users require. However, the physical and logical structures inside the Internet cloud can be extremely complex as shown in Figure . The Internet has grown rapidly to allow more and more users. The fact that the Internet has grown so large, with more than 90,000 core routes and 300,000,000 end users, proves the effectiveness of the Internet architecture.

Two computers located anywhere in the world that follow certain hardware, software, and protocol specifications can communicate reliably. The standardization of ways to move data across networks has made the Internet possible.

This page concludes this lesson. The next lesson will discuss Internet addressing. The first page covers IP addressing.