1.4 Computer networks  (Page 2/2)

There are three basic categories of network topologies:

• Physical topologies
• Signal topologies
• Logical topologies

Here are some physical topology

Point to point

The simplest topology is a permanent link between two endpoints. Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is the value of guaranteed, or nearly so, communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers.

Bus

Bus networks (not to be confused with the system bus of a computer) use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.

Ring

In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). A failure in any cable or device breaks the loop and can take down the entire network.

The internet

History of the internet

The history of the Internet dates back to the early development of communication networks. The idea of a computer network intended to allow general communication between users of various computers has developed through a large number of stages. The melting pot of developments brought together the network of networks that we know as the Internet. This included both technological developments, as well as the merging together of existing network infrastructure and telecommunication systems.

The earliest versions of these ideas appeared in the late 1950s. Practical implementations of the concepts began during the late 1960s and 1970s. By the 1980s, technologies we would now recognize as the basis of the modern Internet began to spread over the globe. In the 1990s the introduction of the World Wide Web saw its use become commonplace.

Internet services

• FTP (Filer Transfer Protocol)
• Telnet
• WWW
• Email
• Chat

Advantages of the internet

The Internet or the World Wide Web is indeed a wonderful and amazing addition in our lives. The Internet can be known as a kind of global meeting place where people from all parts of the world can come together. The major advantages of the internet are:

• E-mail: E-mail is an online correspondence system. With e-mail you can send and receive instant electronic messages, which works like writing letters.
• Access Information: The Internet is a virtual treasure trove of information. The ‘search engines’ on the Internet can help you to find data on any subject that you need.
• Shopping: Along with getting information on the Internet, you can also shop online. There are many online stores and sites that can be used to look for products as well as buy them using your credit card
• Online Chat: There are many ‘chat rooms’ on the web that can be accessed to meet new people, make new friends, as well as to stay in touch with old friends.
• Downloading Software: You can download innumerable, games, music, videos, movies, and a host of other entertainment software from the Internet, most of which are free.

How to connect to the internet?

Before you can connect to the Internet and access the World Wide Web, you need to have certain equipment:

• The Hardware: Modem (dial up, ADSL) or Ethernet Card
• The Software: Operating System, Connection Software
• The Browser
• Connection Options: Dial up, Cable, ADSL, Wireless. . .
• Locating Internet Access Providers