Perspectives on Networking

So, you are new to networking. Like many people, your perspective about networks might be that of a user of the network, as opposed to the network engineer who builds networks. 

 For some, your view of networking might be based on how you use the Internet, from home, using a high-speed Internet connection like digital subscriber line (DSL) or cable TV.

The top part of the figure shows a typical high-speed cable Internet user.  The PC connects to a cable modem using an Ethernet cable. The cable modem then connects to a cable TV (CATV) outlet in the wall using a round coaxial cable—the same kind of cable used to connect your TV to the CATV wall outlet.  Because cable Internet services provide service continuously, the user can just sit down at the PC and start sending email, browsing websites, making Internet phone calls, and using other tools and applications.

The lower part of the figure uses two different technologies. First, the tablet computer uses wireless technology that goes by the name wireless local-area network (wireless LAN), or Wi-Fi, instead of using an Ethernet cable. In this example, the router uses a different technology, DSL, to communicate with the Internet.

 Both home-based networks and networks built for use by a company make use of similar networking technologies. The Information Technology (IT) world refers to a network created by one corporation, or enterprise, for the purpose of allowing its employees to communicate, as an enterprise network. The smaller networks at home, when used for business purposes, often go by the name small office/home office (SOHO) networks. 

Users of enterprise networks have some idea about the enterprise network at their company or school. People realize that they use a network for many tasks. PC users might realize that their PC connects through an Ethernet cable to a matching wall outlet, as shown at the top of Figure 1-2. Those same users might use wireless LANs with their laptop when going to a meeting in the conference room as well. 

TCP/IP Networking Model 

A networking model, sometimes also called either a networking architecture or networking blueprint, refers to a comprehensive set of documents.

 Individually, each document describes one small function required for a network; collectively, these documents define everything that should happen for a computer network to work. 

Some documents define a protocol, which is a set of logical rules that devices must follow to communicate. Other documents define some physical requirements for networking. 

For example, a document could define the voltage and current levels used on a particular cable when transmitting data. You can think of a networking model as you think of an architectural blueprint for building a house. Sure, you can build a house without the blueprint.

 However, the blueprint can ensure that the house has the right foundation and structure so that it will not fall down, and it has the correct hidden spaces to accommodate the plumbing, electrical, gas, and so on.

 Also, the many different people that build the house using the blueprint—such as framers, electricians, bricklayers, painters, and so on—know that if they follow the blueprint, their part of the work should not cause problems for the other workers. 

Similarly, you could build your own network—write your own software, build your own networking cards, and so on—to create a network. However, it is much easier to simply buy and use products that already conform to some well-known networking model or blueprint. Because the networking product vendors build their products with some networking model in mind, their products should work well together.