09 Communication And Networking Flashcards

1
Q

What is serial data transmission?

A

One cable is used and the bits are sent one after the other along it
Two lines are required for two way transmission

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2
Q

What is parallel data transmission?

A

Parallel cables are a ribbon of several smaller cables
Several bits are sent at once along different channels however it has to wait until one set of data has been sent in order to send the next set

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3
Q

What are the advantages of serial data transmission?

A

Only one line is required
They are reliable over very long distances at very high frequencies
Serial connectors are cheaper and smaller

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4
Q

What are two problems with parallel data transmission?

A

Skew - As each wire has different properties, bits may travel slightly faster in one wire compared to another which causes skew

Crosstalk - It is the electromagnetic interference between two adjacent channels or parallel wires and gets more pronounced as frequency (speed of transmission) increases

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5
Q

What are the advantages and disadvantages of parallel data transmission?

A

It is fast over a short distance such as inside computers

It can only be used in short distances of up to 2m
Liable to crosstalk and skew
Uses much more lines/cables

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6
Q

Give an example of a serial and parallel connector

A

Serial - USB

Parallel - VGA

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7
Q

What is synchronous data transmission?

A

All data transfers coincide with an internal clock pulse
Data is sent as one long stream or block of data with no gaps
Receiver counts the bits and reconstructs it

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8
Q

What is asynchronous data transmission?

A

Each byte is sent separately the moment it is available

Each byte starts with a start bit and ends with a stop bit.

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9
Q

How is a parity bit used in asynchronous data transmission?

A

It is added as the 8th bit and is used for error detection

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10
Q

What are the advantages and disadvantages of asynchronous transmission?

A

It is relatively slow due to the increased number of bits being sent

It is a cheap and effective form of serial transmission well suited to low speed connections such as a mouse and keyboard

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11
Q

What is latency?

A

The time delay between the moment the first byte starts and when it is received at its destination

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12
Q

What is a protocol?

A

The set of rules relating to communication between devices

Two devices can be linked if they have the same protocol

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13
Q

What does a protocol need to define?

A
Standards for physical connections and cabling
Rate of transmission (bit or baud rate)
Data format
Asynchronous or synchronous
Error checking procedures
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14
Q

What is bit rate?

A

The number of bits transmitted in one second over a wired or wireless data link

Higher signal change means higher bit rate

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15
Q

What is baud rate?

A

How many times a signal changes per second

Measured in megabits per second (Mbit/s

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16
Q

What is baseband?

A

It carries one signal at a time. A bit is represent by high or low voltage

In baseband, bit rate is the same as baud rate and at each signal change one symbol is transmitted

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17
Q

What is broadband?

A

It carries multiple signals on a fixed carrier wave and bits are sent as variations on the wave

18
Q

What is the relationship between bit and baud rate?

A

Bit rate = baud rate x number of bits per signal

19
Q

What is bandwidth?

A

The maximum capacity of a communications channel

Data transfer rate

20
Q

What is a local area network (LAN)?

A

Two or more computers connected together within a small geographical area (building)

21
Q

What is a network topology?

A

The arrangement of the devices which make up a computer network

22
Q

What is bus topology?

A

All nodes are connected to a single backbone cable
Each end has a terminator which stops signals bouncing back
Each node is passive
Data is sent in one direction at a time
Only one computer can transmit successfully at one time

23
Q

What are the advantages of a bus network?

A

Cheap to set up
Easy to add more devices
Good for small networks

24
Q

What are the disadvantages of a bus network?

A

If the main cable fails, everything fails
Limited cable length
Poor security
Low performance under heavy use due to data collisions

25
What is Carrier sense multiple access with collision detection (CSMA/CD)?
It detects two nodes attempting to transmit at the same time Both nodes stop and wait a random amount of time before transmitting again Used in wired networks CSMA/CA (Collision Avoidance) is used in wireless networks
26
What is star topology?
Computers are connected to a central node which is either a hub or a switch
27
What is a switch and what is a hub?
A switch sends each communication to the specific computer it is intended for. It uses MAC addressing A hub broadcasts the message to every computer on the LAN
28
What are the advantages of a star network?
Easy to isolate problems Good performance More secure if a switch is used as data is only sent to the recipient
29
What are the disadvantages of a star networks?
Can be expensive to set up because of the length of cable required If the central device fails everything else fails
30
What is physical and logical topology?
Physical - How the devices are physically connected Logical - How the devices communicate across the physical topologies
31
What is a client-server network?
Server provides services or resources required by clients Client requests services or resources Suitable for small and big organisations but requires an IT specialist
32
What does the server do in a client server network?
Manage security Hold some files Some processing tasks
33
What is peer to peer networking?
No central server All computer can see each other’s files and communicate with each other If a computer is switched off data cannot be retrieved
34
What are the advantages of cloud computing?
Some software does not have to be downloaded Accessible from anywhere with anything Automatic backup and doesn’t take any storage on the device
35
What is the purpose of Wi-Fi and what is needed for it?
Wireless network which devices can connect to through the WAP (wireless access point) Need an ISP, modem and wireless router, device with an NIC
36
How does Wi-Fi work?
A station consists of a computer and a network interface card Stations share a radio frequency channel WAP requires a connection to a router and router requires a connection to the modem
37
What is SSID?
Service set identifier | Identifies each network by a unique name
38
How can u secure Wi-Fi connections?
WPA WPA2 MAC address whitelist
39
How does CSMA/CA work?
Assemble a frame Is channel idle? If no wait a random amount of time If yes transmit data
40
What is the hidden node problem?
Nodes A and B are hidden from each other but the WAP can hear them both
41
What is CSMA/CA using RTS/CTS?
``` Assemble a frame Is channel idle If no wait a random amount of time If yes transmit RTS Is CTS received? If no wait a random amount of time and go back to is channel idle? If yes transmit data ```