Chapter 6: Evolution of Networking & Terminologies

A Computer Network is a collection of interconnected computers and devices that can communicate with each other and share resources like data, hardware (printers), and software.

6.1 Evolution of Networking

The Internet as we know it didn’t appear overnight. It evolved through several key research projects.

1. ARPANET (Advanced Research Projects Agency Network):

   • Considered the grandfather of the Internet.
   • Created in 1969 by the US Department of Defense (ARPA).
   • Its primary goal was to connect computers at different universities and research institutions to allow scientists to share data and resources optimally, even over unreliable military lines.

2. NSFNET (National Science Foundation Network):

   • Created in the mid-1980s by the US National Science Foundation.
   • It was a high-capacity network designed to connect supercomputer centers across the country. It was much faster than ARPANET and had broader access, but initially restricted to research use only.

3. The INTERNET:

   • As ARPANET and NSFNET grew, eventually smaller regional and local networks were interconnected, forming a massive “network of networks.” This global interconnection of networks became known as the Internet.

6.2 Data Communication Terminologies

Data communication is the exchange of data between two devices via some form of transmission medium.

6.2.1 Core Components of Communication

1. Sender: The device (computer, phone) sending the data.
2. Receiver: The device receiving the data.
3. Message: The information (text, audio, video) being communicated.
4. Communication Media (Medium): The physical path (e.g., cables, radio waves) over which the message travels.
5. Protocols: A set of strict rules governing the communication process (so the sender and receiver understand each other).

6.2.2 Measuring Network Capacity

• Bandwidth: The difference between the highest and lowest frequencies that can be transmitted on a channel. In computer networks, bandwidth often loosely refers to the amount of data that can be transmitted in a fixed amount of time. It’s measured in Hertz (Hz).
• Data Transfer Rate (DTR): The actual speed at which data is transferred over a network. Common units include:
  • bps (bits per second)
  • Kbps (Kilobits per second)
  • Mbps (Megabits per second)
  • Gbps (Gigabits per second)

6.2.3 IP Address

Every device connected to an IP network (like the Internet) is assigned a unique numerical label called an Internet Protocol (IP) Address. It serves two principal functions: host identification and location addressing.

(Example: 192.168.1.1 in IPv4). A computer’s real physical address baked into its network card is called the MAC address, which never changes, unlike an IP address.

6.2.4 Switching Techniques

When data travels across a complex network, it must be routed efficiently from the source to the destination. There are two primary techniques:

1. Circuit Switching:

   • A dedicated physical path (circuit) is established between the sender and receiver before data transmission begins.
   • The path remains dedicated to that connection until communication ends.
   • Analogy: Making a traditional landline telephone call.

2. Packet Switching:

   • No dedicated path is established.
   • The message is divided into small chunks called packets.
   • Each packet carries the source and destination addresses.
   • Packets are routed independently through the network. They may take different paths and arrive out of order. The receiving computer reassembles them.
   • Analogy: Sending a letter via the postal service. This is how the modern Internet works.