Computer Networking Fundamentals and History

Key Networking Concepts: Q&A

Q1. The presentation layer is responsible for translation, compression, and encryption of data.

Q2. The physical layer converts bits into electronic signals for outgoing messages.

Q3. The difference between the maximum and minimum signal heights is called amplitude.

Q4. The difference between the highest and lowest frequencies of the constituent parts of an analog signal is called bandwidth.

Q5. If a system that operates at 1000 baud has four signal levels, then the system can transfer 2000 bits per second.

Q6. A digital signal represents bits.

Q7. If the time required for one cycle of a signal is 2 seconds, then the frequency will be 0.5 Hertz.

Q8. By the 1990s, applications arose that allowed users to transfer images easily.

Q9. The session layer is responsible for dialog control and synchronization.

Q10. Sine waves are especially important in information sources because natural phenomena produce them.

Synchronous vs. Asynchronous Communication

• Synchronous communications: Receiver gets the message instantaneously.
• Asynchronous communications: Receiver gets the message after some delay.

Signal Characteristics

• Frequency: The number of oscillations per unit time (usually seconds).
• Amplitude: The difference between the maximum and minimum signal heights.
• Wavelength: The length of a cycle as a signal propagates across a medium; it is determined by the speed with which a signal propagates.

Bit and Baud

• Bit: The basic unit of information in computing and digital communications.
• Baud: How many times the signal can change per second.

Periodic and Aperiodic Signals

• Periodic Signal: A signal which repeats itself after a specific interval of time.
• Aperiodic Signal: A signal which does not repeat itself after a specific interval of time.

Modulation and Multiplexing

• Modulation: Refers to the way electromagnetic radiation is used to send information.
• Multiplexing: Refers to the way information from multiple sources is combined for transmission across a shared medium.

TCP/IP Suite and OSI Model

• TCP/IP: A suite of communication protocols used to interconnect network devices on the internet.
• Open Systems Interconnection (OSI): A set of internationally recognized, non-proprietary standards for networking and for operating systems involved in networking functions.

Dedicated Circuit and Packet Switching

• Dedicated circuit: A circuit that serves only that appliance.
• Packet-switched networks: Move data in separate, small blocks (packets) based on the destination address in each packet.

Data Passing Through the Layers in OSI

History and Growth of Computer Networking

Early computer networks were designed when computers were large and expensive, and the main motivation was resource sharing. Networks were devised to connect multiple users. Later, networks allowed multiple users to share peripheral devices.

By the 1960s, ARPA planned to interconnect all computers with a network and devise software that would allow a researcher to use whichever computer was best suited to perform a given task. ARPA did the following to achieve this visionary work: gathered some of the best minds available, focused them on computer network research, and hired contractors to turn the designs into a working system.

In less than 30 years, the Internet has grown from an early research prototype connecting a handful of sites to a global communication system. The rate of growth has been phenomenal. The internet has had exponential growth for over 25 years, doubling in size every 9-14 months.