4.9.1-4.9.2-4.9.3 Communication

Question 1

What is Serial Transmission?

Answer 1

1) Serial Transmission is where bits are sent via an interface one bit at a time over a single wire from the source to the destination

Question 2

What is Parallel Transmission?

Answer 2

1) Parallel transmission is where several bits are sent simultaneously over a number of parallel wires
2) Used in integrated circuits and in RAM

Question 3

What are the advantages of Serial over Parallel transmission?

Answer 3

1) Reduction in size and complexity of connectors in serial transmission reduces costs
2) More reliable over longer distances than parallel transmission
3) Lack of interference creates higher signal frequencies which lead to higher net data transfer

Question 4

What are the disadvantages of Parallel over Serial transmission

Answer 4

1) Crosstalk creates interference between lines and can corrupt words which have to be re-transmitted
2) Skew occurs when bits travel at different speeds over the wires

Question 5

What is synchronous transmission and how is it used?

Answer 5

1) Data transfer at regular intervals, timed by clocking signal which allows for a constant and reliable transmission time for sensitive data
2) Parallel transmission uses this synchronised approach with the CPU and the clock emitting a signal

Question 6

What is asynchronous transmission?

Answer 6

1) One byte is sent at a time with each character being preceded by a start bit and a stop bit

Structure:
Start Bit: Singular Byte: Stop Bit

Question 7

What is the role of the start bit and what is required for the correct sending of a signal?

Answer 7

1) The start bit alerts the receiving device and synchronises the clock inside the receiver to receive the character
2) equal baud rates are required for a correct sending of a signal

Question 8

What is the role of the stop bit?

Answer 8

1) The stop bit is a ‘stop period’ which can be of any time period
2) This stop period allows the receiver to identify the next start bit and it allows the receiver time to process the data before the next value is transmitted

Question 9

What is baud rate?

Answer 9

1) The rate at which information is transferred in a communication channel

Question 10

What is the bit rate?

Answer 10

1) The bit rate is the speed at which data is transmitted serially it is measured in bits per second

Question 11

What is bandwidth?

Answer 11

1) Bandwidth is the range of frequencies that a transmission medium can carry
2) Larger the range the higher the quantity of data that can be transmitted
3) Direct relationship between bandwidth and bit rate
4) Expressed in bits per second (bps)

Question 12

What is latency?

Answer 12

The time delay between the start of transmission of the first byte or packet and when it is fully received at its destination

Question 13

What is protocol?

Answer 13

1) A set of rules relating to communication between devices

Question 14

What is the difference between baud and bit rate?

Answer 14

1) Bitrate higher than baud rate if more than one bit is encoded for each signal change

Question 15

What is the relationship between bit rate and bandwidth?

Answer 15

Bitrate is directly proportional to bandwidth

Question 16

What is a Physical Star topology?

Answer 16

1) A star network that has a central node ( a switch or a computer) that acts as a router to transmit messages

Question 17

What is a physical bus topology?

Answer 17

1) All computers are connected to a single cable, the ends of the cable are plugged into a terminator

Question 18

What are the advantages of a Physical bus topology?

Answer 18

1) Inexpensive to install as it needs less cable than a star topology
2) Doesn’t require any additional hardware

Question 19

What are the disadvantages of a bus topology?

Answer 19

1) If the main cable fails network data can no longer be transmitted to any of the nodes
2) Heavy traffic reduces performance
3) Decreased security all computers on the network can see all data transmissions

Question 20

What are the advantages of a Physical star topology?

Answer 20

1) If one cable fails only one station is affected so the fault is isolated
2) Consistent performance even under high traffic
3) Easy to add new stations without disrupting the network
4) No problems with collisions of data since each station has its own cable to the server

Question 21

What are the disadvantages of a Star Network?

Answer 21

1) Costly to install as lengthy cabling is needed

2) If the central device goes down network data can no longer be transmitted to any of the nodes

Question 22

What is peer to peer networking?

Answer 22

1) Each computer has equal status and there is no central server
2) Computers are connected to each other locally or over a wide area network (WAN?)
3) Can be used by companies providing VOD (Video on Demand)

Question 23

What is client-server networking?

Answer 23

1) One or more computers or clients are connected to a central computer (server)
2) Clients can hold their own files and software and can also access resources from the server
3) In larger networks there may be several servers
4) The client requests services from the servers e.g. file server, email server

Question 24

Explain the purpose of wifi?

Answer 24

1) WIFI is a local area wireless technology that allows you to connect your devices to the internet via a wireless network (WAP Wireless access point)

Question 25

What is a Wireless network adapter?

Answer 25

1) A physical device that allows a computer system to connect to a wireless network

Question 26

What is a wireless access point?

Answer 26

Creates a local area network that allows multiple devices to connect to a wired network

Question 27

How is a wireless network secured?

Answer 27

1) WPA and WPA 2 (Wi-Fi Protected Access) security protocols which provide strong encryption for data transmissions with 128-bit keys generated for packets sent
2) SSID (Service Set Identification) which is just the name of the network
3) MAC address whitelists control who is allowed on a network this address is a unique identifier assigned to a network interface card by the manufacturer

Question 28

What is CSMA/CA?

Answer 28

1) CSMA/CA (Carrier sense multiple access/ collision avoidance) is a protocol for carrier transmission in wireless area networks
2) Works by nodes listening for signals on the wireless network to determine if another node is already transmitting
3) If it detects another node transmitting it will wait a random period of time for that now to stop transmitting and then listen again

Question 29

What is RTS/CTS?

Answer 29

1) RTS = Request to Send
CTS = Clear to Send

2) When no other node is transmitting an RTS ( request to send) signal is sent out and when the channel is idle the WAP sends a CTS ( Clear to send a signal)
3) This eliminates the problem of hidden nodes

Question 30

Purpose of SSID?

Answer 30

1) Hide your network

2) Identify your network

Question 31

Explain the structure of the Internet?

Answer 31

1) Backbone cables connected by trans-continental lines fed across sea beds
2) National ISP’s directly connected to this backbone and distribute the internet to smaller ISPs who provide internet to homes and businesses

Question 32

Describe URL (Uniform resource locator)? (MOUZ MHL)

Answer 32

1) A URL is the full address for an Internet resource it specifies the location of the resource on the internet including name and file type
2) The browser requests this address from the website server

• method = HTTP
• Host = www
• Location = webpage
• Resource = element (end of URL)

Question 33

What is packet switching?

Answer 33

1) A method for sending data over a network by breaking data into several data packets which are sent independently and join together when they reach their destination

Question 34

What is a router?

Answer 34

1) Routers are devices used to connect at least two networks commonly two LAN’s or WAN’s

Question 35

What is an IP address?

Answer 35

1) An IP address is a unique address that is assigned to a network device
2) The IP address indicates where a packet of data is to be sent or has been sent from

Question 36

What is a Fully qualified domain name (FQDN)

Answer 36

1) A FQDN is one that includes the host server name
- WWW
- mail
- FTP
2) This depends on what server the email is requested from

Question 37

What is a domain name and how are domain names organised?

Answer 37

1) A domain name identifies the area or domain that in internet resource resides in
2) Structured into a hierarchy of smaller domains and written as a string separated by full stops

Question 38

What is a gateway? (Packet head cutter)

Answer 38

1) A gateway is used when packets are routed from one router to another where there are different protocols
2) A gateway strips header data from the packet leaving and applies a new header with the same format as the new network is applied and the packets sent of

Question 39

Explain the role of the Internet registries?

Answer 39

1) 5 global organisations governed by the (ICANN) have worldwide databases that hold records of all domain names currently issued
2) Needed so a domain name is only used by one organisation

Question 40

What is a firewall? (Remember PP)

Answer 40

1) A firewall is a security checkpoint designed to prevent unauthorised access between two networks it makes use of
- Proxy Servers
- Packet Filtering

Question 41

How does Packet Filtering Work?

Answer 41

1) Examines the source and destination IP addresses in packet headers
2) If the IP address matches that on the permitted list then they are accepted
3) Can also block packets based upon the protocols being used and the port numbers they are trying to access

Question 42

How does Stateful inspection work?

Answer 42

1) Examines the payload contents of a data packet to better assess it for safety
2) Can also create temporary contextual based on the passage of previous packets in ‘a conversation’

Question 43

How does a proxy server work?

Answer 43

1) Physical computer that intercepts packets entering and leaving a network while hiding the true network addresses of the source from the recipient
2) Allows for privacy and anonymous surfing

Question 44

Explain symmetric (Private Key) encryption?

Answer 44

1) Uses the same key to encrypt and decrypt data

Question 45

Explain Asymmetric (Public Key) encryption?

Answer 45

1) Uses two separate but related keys one of the keys is a public key which is made so others can encrypt the data they want to send to you
2) Private Key which is known only by you and it can be used to decrypt data

Question 46

What is a Digital Signature?

Answer 46

1) A mathematical scheme producing a unique signature that verifies the authenticity of encrypted digital message
2) It is used to encrypt the contents of a message using public and private keys the public key encrypts the hash total and the public key encrypts the whole message
3) The Recipient uses their own private key to decrypt the message and uses the senders public key to decrypt the signature
4) If the hash total matches the total in the digital signature it verifies the integrity of the message

Question 47

What is a Digital certificate?

Answer 47

1) A digital certificate verifies ownership of a key pair used in asymmetric encryption
2) Can be used to check that a fake key pair isn’t being used by an imposter. Issued by certificate authorities.

Question 48

What is a Virus and what vulnerabilities does it exploit

Answer 48

1) Viruses are a type of malware that requires a host file to reside in, these files are usually executable files
2) Most reside inside of memory and once in memory all other uninfected files that run become infected

Question 49

What is a worm and what vulnerabilities does it exploit?

Answer 49

1) Worms are pieces of malicious software that can self-replicate between computers within a network or by users downloading and running a malicious file E.g Email attachment

Question 50

What is a Trojan and what vulnerabilities does it

exploit?

Answer 50

1) A Trojan is a type of malware disguised as a benign or a useful file that when opened a payload is released
2) A Trojan can open a back door to your computer system and can harvest personal information or use up bandwidth to send spam emails etc
3) This slows down your computer

Question 51

What system vulnerabilities does malware exploit?

Answer 51

1) Exploits human and software bugs
2) Un-renewed Virus protection weakens systems
3) Failed administrative rights
4) Cracks in software

Question 52

How can malware such as trojan worms and viruses be handled?

Answer 52

1) Code Quality: ‘buffer overflow’ values stored in location they shouldn’t have access to and data is interpreted as instruction
2) Educations around spam emails and, spam filtering
3) Anti-Virus software updates reduce the risk of attack