Communication

Question 1

Explain what a handshake is, and why it is useful.

Answer 1

Handshaking - Handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel before normal communication begins.

Handshaking allows for the establishment of a reliable connection, it allows for the two hosts to agree on properties which provide security and reliability.

Handshaking allows for the two hosts to agree on sequence numbers, allowing for reliable communication and easy identification of missing/duplicated packets.

Question 2

What is parallel data transmission, how does it differ from serial data transmission?

Answer 2

Parallel data transmission sends multiple bits at the same time.

The difference is that parallel transmits data over multiple wires/cables, while serial uses only transmits over a single medium.

Question 3

List two advantages and one disadvantage of using Asynchronous data transmission over Synchronous data transmission.

Answer 3

Asynchronous transmission

Advantages:
Simple, doesn’t require synchronization of both communication sides
Cheap, because asynchronous transmission requires less hardware
Setup is faster than other transmissions, so well suited for applications where messages are generated at irregular intervals, for example data entry from the keyboard, and the speed depends on different applications.

Disadvantages:
Large relative overhead, a high proportion of the transmitted bits are uniquely for control purposes and thus carry no useful information

Synchronous transmission

Advantages:
Lower overhead and thus, greater throughput
No synchronization between the two communicating hosts is needed.

Disadvantages:
Slightly more complex
Hardware is more expensive

Question 4

What is the importance of a parity bit?

Answer 4

Parity is used to detect that the data you have been sent is correct.

Question 5

What is latency, and how does it affect communication systems?

Answer 5

Latency is the delay between the moment an action is initiated, and the moment it’s first effect occurs.

Extreme latency will reduce performance and will increase the time needed to complete tasks.

Question 6

Explain baud rate in the context of data communications.

Answer 6

Baud rate is the rate at which signals may change, how often the voltage transmitted over a wire may change.

Question 7

Explain the relationship between bit rate and bandwidth.

Answer 7

The greater the bandwidth the higher the bit rate.

If data rate is W bits/sec a good representation can be achieved with 2W Hz (bandwidth).

Question 8

A printer is connected to the same computer using a faster serial connection at a speed
of 128,000 bits per second and a baud rate of 64,000 baud.

Explain how it is possible for the number of bits transmitted per second to be higher
than the baud rate.

Answer 8

Each signal level/signal change represents two bits (of data)/more than one bit (of data) // channel supports four/more than two different signal levels/voltages // use of modulation/coding technique e.g. phase
modulation.