4.9 Fundamentals of communication and networking

Question 1

define serial data transmission

Answer 1

sends one bit at a time, serial uses a single wire, typically used for transmitting data over medium to long distances

Question 2

define parallel data transmission

Answer 2

sends multiple bits simultaneously, parallel uses several wires, the more lines that the medium uses the more data can be transferred simultaneously, used for short distances

Question 3

advantages of serial over parallel transmission (three reasons)

Answer 3

1) parallel communication requires more wires so higher cost and more difficult to manage when setting up the system
2) parallel needs the data to be synchronised across the wires so more chance of errors and limiting factor on transmission speed
3) parallel carries risk of crosstalk between wires so also more chance of errors

Question 4

what is skew and how does it occur

Answer 4

skew is a problem where the bits sent will not be received together - each of the communication lines in parallel transmission will have slightly different electrical properties meaning time takes for bit to transfer will differ slightly - skew is worse over long distances and an lead to buts from different pulses overlapping causing corruption

Question 5

what is crosstalk

Answer 5

occurs in parallel transmission when the communication lines are tightly packed signals from one line can leak into another also causing data corruption

Question 6

define synchronous data transmission

Answer 6

a clock signal shared between sender and receiver is used to time when signals are sent - used within buses in the FDE cycle - signals sent in regular intervals will be received in the same order so suitable for transmitting information in real time systems

Question 7

define asynchronous data transmission

Answer 7

start and stop bits are used to indicate the duration of a transmission - start bits are either 0 or 1 and stop bits are the opposite of the start bit - sender and receiver must use the same baud rate so they only need to synchronise clock for duration of data transmission

Question 8

define baud rate

Answer 8

number of signal changes per second - measured in bauds

Question 9

define bit rate

Answer 9

the number of bits that can be sent in one second - measured in bits per second (bps)

Question 10

relationship between bit rate and baud rate

Answer 10

bit rate = baud rate x no of bits per signal

Question 11

define bandwidth

Answer 11

bandwidth relates to the range of frequencies that a communication medium is capable of transmitting - measured in hertz

Question 12

what is the relationship between bit rate and bandwidth

Answer 12

bit rate is directly proportionate to bandwidth

Question 13

how can bit rate be higher than baud rate

Answer 13

each signal change represents more than one bit of data

Question 14

define latency

Answer 14

time delay between a signal being transmitted and it being received - measured in milliseconds - usually increases with distance

Question 15

define protocol

Answer 15

a set of rules relating to communication between devices

Question 16

what is a physical network topology

Answer 16

the physical architecture of the cabling between devices on the network

Question 17

what is a logical network topology

Answer 17

the flow of data packets around a network

Question 18

what is a physical star topology

Answer 18

each client has a direct connection to a central node, the central node receives all packets and delivers them to the recipient

Question 19

advantages of a physical star topology - 4 reasons

Answer 19

1) packets are sent directly to recipient so other clients on the network can’t see packets not intended for them - improved security
2) easy to add and remove clients to and from network
3) speed of links are constant as no collisions
4) improved reliability as if one link fails the other links are not affected

Question 20

disadvantages of physical star topology - 2 reasons

Answer 20

1) if the central hub fails, all communication is stopped
2) its expensive to install as lots of cables required

Question 21

what is a physical bus topology

Answer 21

connects clients to a single cable called the backbone - a device called a terminator is placed on either end of the backbone with the server connected via the backbone too

Question 22

advantages of a physical bus topology

Answer 22

1) no central hub so reduces chance of network failure and cost of installation
2) inexpensive to install as a minimum length of cable required

Question 23

disadvantages of a physical bus topology

Answer 23

1) low security as packets are sent through shared backbone so all clients can see them
2) the backbone may be used by multiple clients - increasing risk of collisions
3) if the backbone fails the entire network becomes unusable

Question 24

difference between logical bus and star topology

Answer 24

logical bus network delivers packets to all clients on the network whereas logical star network only delivers the packet to the recipient

Question 25

how can a physical star topology behave logically as a bus network

Answer 25

by using a bus protocol and appropriate packet switching to distribute packets to all connected clients

Question 26

what is a host on a network

Answer 26

a device on a network that provides services - often a server - includes file storage, printer sharing and internet access

Question 27

what is peer-to-peer networking

Answer 27

each computer has equal status, services are provided by the clients themselves - any device can access and share resources from any other client

Question 28

what is client-server networking

Answer 28

one or more central servers provide services to the clients on the network, servers are often more powerful machines than the clients - clients request services from the servers

Question 29

advantages of client-server networking

Answer 29

allows for central management of clients on a network - improves security

Question 30

disadvantages of client-server networking

Answer 30

requires expertise to set up and manage

Question 31

advantage of peer-to-peer networking

Answer 31

more cost effective as there is no need for a powerful server - easier to set up and maintain

Question 32

disadvantage of peer-to-peer networking

Answer 32

all clients which provide services must be running in order for the network to be fully operational

Question 33

when is client-server networking used

Answer 33

most schools and business organisations use it to allow central management of clients on network

Question 34

when is peer-to-peer networking used

Answer 34

large file-sharing networking and multimedia providers use is to provide high performances services without needing a server

Question 35

explain the purpose of wifi

Answer 35

wifi is used to enable devices to connect to wireless networks, refers to a wireless local area network that is based on international standards, this allows a device made in one part of the world to seamless connect to wireless networks all over the world

Question 36

what components are required for wireless networking

Answer 36

requires a wireless access point which connects to a wired network and a wireless network adapter in the device that connects to the wireless network

Question 37

How are wireless networks secure

Answer 37

by encrypting transmitted data using a WPA or WPA2, disabling SSID broadcoast and set up a MAC address allow list

Question 38

what is a WPA

Answer 38

stands for wifi protected access anf requires that a new wireless client entrers a password in order to connect to the network

Question 39

what is SSID and how does disabling it enhance security

Answer 39

stands for service set identifier it is the name that identifies wireless networks - disabling it stops wireless devices within range of the network from displaying it is available so only those who know the SSID can connect

Question 40

what is a MAC address and how does setting up an allow list enhance security

Answer 40

stands for media access control - addresses are assigned to every wireless device and is unique - mac address allow lists are used to only allow specific devices to connect to a network