(P2) Fundamentals of Communication And Networks Flashcards
1
Q
Describe what thin client computing is.
A
Thin client computing are programs that are executed on an application server.
2
Q
Explain two reasons why a thin client system is better than a thick client system.
A
Clients are cheaper as they have lower hardware specifications. Easier to add new clients. Simpler to update software.
3
Q
Describe the relationship between bitrate and bandwidth.
A
Greater the bandwidth, the higher the bit rate. They are directly proportional.
4
Q
Describe the difference of operation between of serial and parallel transmission.
A
Serial sends one bit at a time, but parallel sends multiple bits at the same time.
5
Q
Explain why a laser printer with a built in wireless network adapter is likely to be a suitable choice for a small office.
A
Laser printer: cheaper than buying ink. Cheaper per page.
Wireless: Cheaper as no cabling. All devices can use it.
6
Q
State one reason why IPv6 has been introduced to replace IPv4.
A
Not enough unique addresses in IPv4.
7
Q
Explain how the CSMA/CA protocol with RTS/CTS is used.
A
- Computer with data to send monitors data signals.
- If data signal is present, then continue to wait.
- When no signal presents, computer sends Request To Send (RTS).
- Two computers could start transmitting at the same time if they both detect no data signal.
- Wireless Access Point (WAP) responds to RTS with Clear To Send (CTS) signal.
- RTS/CTS signal blocks any other transmission from nodes for specific time.
- When CTS received then start to transmit.
- If CTS not received, continue to wait.
- Reciever sends acknowledgement.
- After transmitting, the transmitter waits to recieve acknowledgement packet.
- If no acknowledgement then wait and listen again.
- Acknowledgement notifies other computers they can transmit again.
- Collisions cannot be detected by transmitter.
8
Q
State two reasons why JSON is better than XML.
A
Less lines of code so take up less storage/ memory.
Easier for humans to read and debug.
9
Q
State one advantage of using DHCP.
A
No requirements to manually assign IP addresses. Facilitates efficient use of a limited pool of IP addresses.
10
Q
Explain how two or more computers connected to the Internet can have the same IP address and still communicate with each other.
A
Computers have private IP addresses. Network address translation (NAT) will be performed so that computers can communicate on the Internet.
11
Q
Explain four different ways that a firewall can protect computers on a LAN.
A
Block specific protocols. Block certain types of packets. Firewall maintains information about current connections and only allows packets relevant to these connections through. Acts as proxy server.
12
Q
Explain how Computer A will use a subnet mask to determine whether or not it can send the packet directly to Computer B across the LAN or if the packet must be send via the Internet.
A
AND operation of subnet mask with Computer A’s and B’s IP address. Result of each AND operation is the subnet ID. Subnet ID compared, if they are different packets, then must be sent through Internet.
13
Q
Explain how packets are routed across the Internet.
A
Hierarchical organisation of routers. Path to take selected by each router. Route may change as a result of congestion. Route determined using the IP address. Router decrementing “time to live” of packet. Source and destination MAC address changed at each router.
14
Q
Explain how the checksum can be used to determine if the recieved packets has been changed during transmission.
A
Checksum produced when packet transmitted. Checksum calculated from packet content. MOD operation used to limit magnitude of checksum. Recalculated checksum and compare. If these match, data is accurate.
15
Q
State the name of two application protocols and their use.
A
SMTP- Send/ transmit emails
IMAP- Send and recieve emails
16
Q
Explain how the transport layer of TCP/IP stack determines which application layer software on the server should deal with the received request.
A
It uses the port to determine which server should deal with the request.
17
Q
Describe one function of the network layer of the TCP/IP stack.
A
Adds source IP address. Adds destination IP address.
18
Q
Explain the difference between asynchronous and synchronous communication.
A
Asynchronous: The receiver and transmitter are not synchronised by a common clock.
Synchronous: The reciever and transmitter are synchronised by a common clock.
19
Q
In asynchronous data transmittion, where are the stop, start and parity bit located?
A
Left to Right:
Stop. Parity. Start.
20
Q
A message is to be sent from Computer A to B and will be encrypted using asymmetric encryption. To enable Computer B to authenticate that the message was sent by Computer A, a digital signature will also be sent with the message.
Explain how Computer B will decrypt the message and verify that it was sent by Computer A.
A
Receiver’s private key is used to decrypt message. Hash is calculated from the message. Sender’s public key is used to decrypt the digital signature. If both hashs match then the sender then the sender can be authenticated.
21
Q
Explain why the DCHP system is used.
A
Reduces the need for expert knowledge when configuring a host. Facilities efficient use of a pool of IP addresses. Content of communication: Host sends to discover a DHCP server. DHCP server offers configuration to host. Host accepts offer of configuration from DHCP server by echoing the accepted to host.
22
Q
What is the purpose of DHCP system?
A
To auntomate the configuration of hosts connecting to a TCP/IP network.
23
Q
What is the key exchange problem with a symmetric cipher?
A
How to pass the key from sender to reciever as the key can be intercepted if transmitted.
24
Q
Explain how External Routers are configured so that web servers can be accessed by computers outside of the network.
A
Trafiic arriving on the HTTPS port must be forwarded by the external router to the IP address on the Web Server.
25
Describe two security measures to keep a wireless access point secure and explain how these measures will make ut more secure.
Disable broadcast of SSID so that you must know the SSID to connect.
Use a MAC address whitelist so that only devices with an address on the list can connect.
26
Explain how the CSMA/CA access method with RTS/CYS will be used during thia transmission.
Computer with data to send listens for data signal. If data signal is present then continue to wait. When no data signal present, computer sends a Request to Send. Two computers could start transmitting at the same time if they both detect there is no signal. WAP responds to Request to Send with Clear to Send. RTS/CTS signal blocks any other transmission from nodes in range. When CTS is recieved, then start to transmit. If CTS not recieved continue to wait. Reciever sends acknowledgement. After transmitting, the transmitter waits to recieve acknowledgement packet. If no acknowledgement, wait a period of time. The acknowledgement also notifies other computers that they can transmit again. Waiting periods are often random. Collisions cannot be detected by transmitter.
27
Explain the difference between a symmetric and an asymmetric cipher system.
Symmetric: same key used to encrypt and decrypt.
Asymmetric: different but related keys are used for encryption and decryption.
28
Explain why serial communication is more appropriate than parallel communication when sending data over long distances.
Skew can occur where data arrives in the wrong order, which is likely to happen over long distances.
Bit transmitted together don't arrive together.
29
Explain the difference between a physical topology and a logical topology.
Physical: the layout of the wiring between devices.
Logical: how data flows around a network.
30
Explain the difference between client-server and peer-to-peer networking.
Client-server: All data and resources are stored on the server. Setup requires greater expertise. Administration is easier.
Peer-to-peer: All devices have equal status. Resources are stored on each individual device. Any device can share resources with any other device on the network. A device can act as both client and server. Devices communicate directly with each other. No dependence on a server.
31
State one difference between HTTP and HTTPS.
HTTPS uses encryption to make it secure.
32
Identify the TCP/IP layer that is concerned with ports and explain how a client port and a well-known port are used when retrieving a web page.
Transport layer. Client port allocated to web browser by transport layer. Well Known Port: web server uses Well Known Port so that client is able to contact it to initate.
33
What is the purpose of a Domain Name System (DNS) server?
To take a required FQDN and return an IP address.
34
Describe two situations when a DNS query will not be sent to a DNS server.
The local computer already has a copy of the needed IP address in a host's file.
The local computer has a cache of recent DNS queries.
35
What is encryption?
Using an algorithm to convert a message into a form that is not understandable without the key to decrypt it.
36
State two purposes of the addition of a digital signature to a message.
Verfiy the sender.
Detect if message has been tampered with.
37
Explain how a thin-client works.
Most processing is done by the central server. Work stations are just interfaces. Applications are not installed on thin client workstations.
38
Explain how choosing to use a thin-client network will affect the selection of hardware used by the system.
Higher bandwidth network connection required. Network must use switch not hub.
39
Explain what is meant by an IP address.
A numerical value assigned to a device.
40
State what is meant by the term protocol.
A set of rules for communication between devices.
41
Explain what a virus is and the diferenfes between a virus and a worm.
Virus is a program that attachs itself to another program. Self-replicating. Has malicious purposes. Viruses need human interaction to spread, and worms do not. Viruses are a sub-class of worm. Worms duplicate by exploiting a network security weakness.
42
Describe the steps that would be involved in producing a digital signature for a message before it is transmitted by a computer.
Digest calculated from message contents. Sender's private key is used for hash encryption. Digital signature is appended to message.
43
Explain what asynchronous data transmission is and why stop and start bits are required when asynchronous data transmission is used.
Transmission of data without use of external clock signal.
Start but locks reciever and transmitter in phase.
Stop bit allows start bit to be recognised.
44
What is Baud Rate?
The number of signal changes in the medium per second.
45
What is Bit Rate?
Number of bits that are transmitted over the medium per second.
46
State the equation for bit rate.
Bit rate = Baud rate × No. of Bits per signal
47
What are the units for Bandwidth?
Hertz.
48
What is bandwidth?
Range of frequencies that a communication medium is capable of transmitting.
49
What is the relationship between bandwidth and bit rate?
Direct relationship.
50
What are the units for latency?
Milliseconds.
51
What is Latency?
The difference in time between an action being initiated and its effect being noticed.
52
Explain how serial data transmission works.
Data is sent one bit at a time over one communication line.
53
When is serial transmission usually used?
Over medium to long distances (e.g. mouse to computer).
54
Explain how parallel data transmission works.
The transimssion uses numerous parallel communication lines in order to send multiple bits between components in a computer simultaneously.
55
How is skew caused?
Communication lines that form part of a parallel communication medium will have slightly different electrical properties, meaning that the time taken for one bit to be transferred will differ slightly from line to line. Therefore, bits sent together may not arrive together.
56
State when skew is worse and explain what can happen as a result of this.
Worse over long distances.
Bits from different pulses overlapping, causing a corruption of data.
57
Describe a disadvantage of parallel data transmission.
More expensive because of their use of multiple lines.
58
Describe when parallel data transmission is likely to be used.
Over short distances. (Between parts of the processor and within RAM)
59
What is crosstalk and when does it occur?
Occur over parallel data transmission. When communication lines are tightly packed, signals from one line can 'leak' into another, causing corruption of data.
60
Explain two advantages of serial data transmission.
Doesn't suffer from crosstalk or skew, which makes it more reliable, especially over long distances.
Uses just one line, so are cheaper to install than parallel mediums.
61
When is synchronous data transmission used?
Within busses of a computer's processor in the fetch-execute cycle.
62
Explain why synchronous data transmission is more suitable for transmitting data in real-time systems.
Signals are sent at regular intervals, which will be recieved in the same order that they were sent.
63
Why does asynchronous data transmission not need a clock signal to work?
The start and stop bits indicate the duration of transmittion.
64
Explain how the start and stop bit are related.
The start bit must be a 1 or 0, and the stop bit has to be the opposite.
65
State two requirements for asynchronous data transmission between a sender and receiver.
Use the same Baud Rate.
Synchronise their clocks for the duration of data transmission.
66
Describe a physical star topology.
Each client has its own direct connection to the central hub
67
In a physical star toplogy, what is the hub responsible for?
Recieving packets for all of the clients connected to it and is responsible for delivering them to the correct recipient.
68
Give 4 advantages of a star topology.
1. Packets are sent directly to their recipient, over a cable and so other clients cannot see packets that aren't meant for them.
2. Easy to add and remove clients to and from the network.
3. Each cable has just one device communicating over it, eliminating the possibility of collisions.
4. Failure of one cable does not affect rest of the network.
69
Give 2 disadvantages of a physical star topology.
1. Should central hub fail, all communication over the network is stopped.
2. Expensive to install due to amount of cable required.
70
Describe the components of a physical bus topology.
Clients are connected to a single cable called a backbone.
A device called a terminator is placed at either end of the backbone.
No need for a central hub.
71
Give two advantages for a physical bus topology.
1. No central hub, so reduces chances of a network failure and decreases cost of installation.
2. Inexpensive to install as a minimum length of a cable is required.
72
Give 3 disadvantages of a physical bus topology.
1. Packets are sent through shared backbone, allowing every client on the network to see packets that aren't mesnt for them.
2. Backbone is used for communication by multiple clients, introducing the risk of collisions.
3. Should the backbone fail, the entire network becomes unusable.
73
Describe a logical bus topology.
Network delivers packets to all clients on the network.
74
Describe a logical star topology.
Network delivers packets only to the intended user.
75
Explain what a host is.
A hostbis device on a network that provides services. They provide services such as file storage, printer sharing and internet access.
76
Explain what two components are needed for a wireless network to function.
Wireless access point, which can connect to a wired network.
Wireless network adapter in the devices that connect to the wireless network.
77
Explain how wireless networks are secured: WPA.
By encrypting transmitted data using WPA (WiFi Protected Access) or WPA2.
WPA requires that a new wireless client enters a password in order to connect to a network.
78
Explain a method of securing a wireless network: SSID.
Disabling SSID (Service Set Identifier) broadcast so wireless devices in range of the network can't see the network is available, allowing only those who know the SSID to connect.
79
Explain a way of securing a wireless network: MAC.
Set up a MAC (Media Access Control) address filter. MAC address whitelists can be created to allow only specific devices to connect to a network. Or use a MAC address blacklist to block specific devices from connecting to a network.
80
What does CSMA/CA stand for?
Carrier Sense Multiple Access with Collision Avoidance.
81
What is CSMA/CA?
A protocol hsed in wireless networks to avoid data collisions caused by multiple devices communicating simultaneously.
82
Describe the process of CSMA/CA WITHOUT RTS/CTS.
1. When a device is ready to transmit, it listens to its communication channel to check whether it is idle.
2. If so, then data is transmitted.
3. If the channel is busy, the device waits for a random period of time before checking the channel again.
83
How can a CSMA/CA waiting time period be increased?
Using an exponential backoff algorithm.
84
State a disadvantage of CSMA/CA.
Cannot overcome hidden nodes.
A problem that arises when the device checking for an idle channel cannot see some parts of the network on which there might be communication happening.
85
What does RTS/CTS stand for?
Request to send / Clear to send.
86
State the method of aolving the hidden node problem.
RTS/CTS
87
Describe the process of RTS/CTS.
1. Once the transmitting device has checked whether the channel is idle, it sends a Request to Send message to the server.
2. If the server is idle, it will respond with a Clear to Send message at which point the transmitting device can begin communication with the server.
3. If no Clear to Send message is recieved, the server is busy communicating with a hidden node and the transmitting device must wait.
88
Define the Internet.
A network of inter-connected computer networks which use an end-to-end communication protocol.
89
What protocol is used by the Internet?
TCP/IP
90
What is a packet?
A container in which data is transmitted over networks.
91
Explain what a packet switched network is.
One in which data is sent in packets. One message is frequently split into multiple packets, each of which is sent to its recipient via the best possible route before being reassembled with other packets by its recipient.
92
When a packet is sent through a network, what does it have to pass through?
A number of routers before reaching its destination.
93
How does a router know where to send a packet?
Uses the recipient address on the packet to determine where to send the packet.
94
Define the term 'hop'?
Hop refers to every time a packet passes through a router.
95
What does TTL stand for?
Time To Live
96
Explain what a packet's TTL is?
Number that indicates how many hops the packet can partake in and is reduced by one with each hop.
97
Explain the term 'dropped'.
The term dropped refers to when a packet's TTL expires, meaning that the packet is deleted. The hop count is reduced by one with every hop.
98
What are the components of a packet?
Header
Payload
Footer
Sender's address
Reciever's address
Packet contents
Time to Live
Sequence Number
99
What is the purpose of Sender's Address in a packet?
Identify where the packet is from, therefore where the response should be sent from.
100
What is the purpose of the Reciever's Address in a packet?
Identifies the packet's intended recipient, allowing it to be routed to the correct device.
101
What is the purpose of the Packet Contents in a packet?
Where the packet holds the data that is being transferred.
102
What is the purpose of TTL in a packet?
Holds the number of hops a packet can go through before being dropped.
103
Explain the purpose of a Sequence Number in a packet?
Contains the number of packets in a message and identifies a packet's position relative to each other. This allows packets to be reassembled in the correct order and allowes missing packets to be identified.
104
What is the function of both routers and gateways?
They connect different networks, allowing packets to reach their destination.
105
Describe the route that Routers sent their packets though.
The fastest possible route.
106
What algorithm do routers use to find the shortest route for their packets?
Dijkstra's algorithm.
107
Explain how routers are constantly able to find the quickest path.
Routers hold tables with information relating to the fastest routes to certain devices which they frequently update so they can maximise performance.
108
Explain what must happen to packets when different protocols are used.
Packets must be modified so they conform to both protocols.
109
When are gateways used?
When packets have to conform to more than one protocol.
110
What is the function of gateways?
Gateways strip away most of a packet's details, leaving just the packets contents. The gateway will then give packets new sender and reciever addresses which comply to the new protocol.
111
What does URL stand for?
Uniform Resource Locator
112
What is a URL?
An address assigned to files on the Internet.
113
In a URL, what is the name of the part that comes before the '://'?
Protocol being used tk access a file.
114
What is thenpart of the URL that comes after '//'?
Subdomain. Will usually point to the web server hosted at the following domain.
115
What is the part of the URL located after the subdomain?
The domain.
116
What is the name of the part of the URL that is located directly after the first single '/'?
The directory.
117
What is the name of the part of the URL that is located directly after the second single '/'?
The subdirectory.
118
What is the name of the part of the URL that is located directly after the first single '/'?
Name of the file being requested.
119
What is the name of the part of the URL that is located directly after the final '.'?
The file's extension.
120
What is the purpose of a domain name?
A domain name identifies an organisation or individual on the Internet.
121
What do domain names use to make them easier for humans to remember?
Alphanumerical characters.
122
What does FQDN stand for?
Fully Qualified Domain Name.
123
Explain what a FQDN is?
A domain that specifies an exact resource and can be interpreted in only one way. An FQDN will always include the server's host name.
124
What does IP stand for?
Internet Protocol.
125
Why do we use domain names instead of IP adresses?
IP addresses are not easy for humans to remember. So domain names map to IP addresses.
126
Explain how IP addresses are assigned.
Assigned to every computer on the Internet and every device that communicates on a network.
127
What does DNS stand for?
Domain Name Server.
128
What is the purpose of a DNS and how does it work?
When a domain name is entered into a browser's address bar, a domain name server is used to translate the domain name into its corresponding IP address.
A domain name server stores a table of domain names and their corresponding IP addresses.
129
Explain what happens if a DNS does not have a requested record.
If the DNS does not have the record, you are trying to access, your request will be passed to another DNS. This is more common for smaller websites that are rarely visited as they mighr need numerous changes of servers. This makes accessing these websites slightly slower.
130
What is an Internet Registry?
An organisation responsible for allocating IP addresses.
131
How many Internet Registries are there?
5, each serving a different geographical area.
132
Explain a function of Internet Registries.
Protect the world's depleting pool of unallocated IP addresses. When a new IP address is requested, an Internet Registry will first look for a previously allocated IP address that has become unused rather than allocate a brand new one straight away.
133
Explain what a firewall is.
A firewall sits between a device and the Internet and regulates the packets that pass through it. Firewalls can be either software or hardware and work as a proxy server which can perform bith packet switching and stateful inspection.
134
Explain what packet filtering is.
Firewalls use packet filtering to accept and block packets based on their source IP address or the protocol that they are using, which is determined by their port number. This can be specifying particular IP addresses or protocols to block or using automatic filtering software that can block suspicious packets.
135
Explain what stateful inspection is.
Examining the contents of a packet before deciding whether to allow it through the firewall. Some firewalls keep a record of current connections in a network, allowing them to filter out packets that aren’t related to the activity on the network.
136
Explain what a proxy server is.
A server that sits between a public network and a private network. These devices manage every packet that passes between the two networks.
137
When does a firewall act as a proxy server?
When they control the movement of packets between public and private networks.
138
Discuss how a firewall keeps the users of its private network anonymous.
When a device on a private network sends a packet into a public network, the sender’s address is that of the firewall, and not the IP address of the device. So IP addresses are never sent to anyone to anyone beyond the private network.
139
Explain why symmetric encryption is.
Both sender and receiver share the same private key. This key is used to both encrypt and decrypt data.
140
Discuss the disadvantage of using symmetric encryption.
If key is exchanged over a network, it is vulnerable to interception.
141
Describe asymmetric encryption.
Four different keys are used. Each device has a pair of mathematically related keys, one of which is private and the other is shared on the Internet, making it public.
142
Describe the process of asymmetric encryption without a digital signature.
Message is encrypted by the sender using the recipient’s public key. This mean the message can only be decrypted by the receiver’s private key, which only they have access to. Making the receiver the only person able to decrypt the message.
143
For what type of encryption are digital signatures used?
Asymmetric.
144
Why are digital signatures used?
Verify the sender of a message and make sure the message hasn’t been tampered with.
145
Describe the process of asymmetric encryption with a digital signature.
1. A digest of the message is created, by a checksum or hashing algorithm.
2. Digest is encrypted with the sender’s private key
3. The encrypted digest is appended to the message.
4. The message and appended digest are encrypted with receiver’s public key, so only the receiver can decrypt it.
5. Receiver gets the message and decrypt it using their private key, leaving the decrypted message and the encrypted digest.
6. Digest is decrypted using the sender’s public key. This verifies that the message is from the sender as only they have access to their private key.
7. Receiver decrypts the digest using the same hashing or checksum algorithm.
8. If everything matches, then receiver can be certain it is from sender and has not been tampered with.
146
What information is contained in a digital certificate contain?
Serial number
Owner’s name
Expiry date
Owner’s public key
Certificate authority’s digital signature
147
Why are digital certificates used?
Verifies ownership of a key pair used in asymmetric encryption and can be used to check if a fake key is being used by an imposter.
148
What is a worm?
Malicious software that can self-replicate between computers, either within a network or by users downloading and running a malicious file.
149
What is a Trojan?
Malware that is disguised as a benign file that users can be tricked into opening. Often spread as email attachments or downloaded from malicious softwares.
150
What is a virus?
Require a host file to reside in. These files are typically executable files, so viruses lie dormant until their host file is opened or run. Viruses can spread between computers over a private network or through use of physical media like hard drives or optical disks.
151
How can malware be avoidable?
Malware often exploits bugs in code so having good quality code.
Installing antivirus software.
152
What can make a system more likely to be affected by malware?
Lack of antivirus, out of date software, poor security.
153
What are antivirus programs?
Specialist pieces of software that scan the files on a computer and remove any suspicious files.
154
What does TCP/IP stand for and where is the protocol used?
Transmission Control Protocol / Internet Protocol.
All parts of the Internet.
155
What are the four layers of the TCP/IP stack?
Application
Transport
Network
Link
156
What is application layer responsible for?
Selects and uses the correct protocol to transmit data. The layer interacts with the user with application software like a web browser.
157
What is the transport layer responsible for?
Delivering data to the appropriate application process on the host computer. Establishes a virtual path. Layer splits transmission into packets.
158
What is a virtual path?
End to end connection between the sender and receiver.
159
What is the network layer responsible for?
Providing the correct IP address for each packet’s source and destination. Routers work within the network layer, using IP addresses on a packet to send it to its destination.
160
What is the link layer responsible for?
Controls physical connections between pieces of hardware in a network. Adds MAC addresses to packets which it receives from the network layer. These MAC addresses change with every hop.
161
Why do MAC addresses change with every hop?
Because when a packet reaches a router, the router discards the original source MAC address and replaces it with its own before sending it to where it needs to go next.
162
Describe what happens to a packet when it has reached it’s destination.
1. Packet is stripped of extra information, reversing the TCP/IP stack.
2. Link layer removes MAC address from packet.
3. Network layer removes IP address.
4. Transport layer uses port numbers to determine the correct application to send the packet to.
5. Transport layer checks the packet’s sequence number to ensure that it is in the correct position.
6. Application layer displays information to the user.
163
What is a socket address?
When an IP address is combined with a port number.
164
What does a socket address look like?
An IP address, followed by a colon, followed by a port number.
165
What is socket address used for?
Identifies which of the applications on the recipient decide a packet should be sent to.
166
What does FTP stand for?
File Transfer Protocol.
167
What are the part numbers for FTP?
20 and 21
168
What is the purpose of the FTP protocol?
Used for sending files between devices. FTP client software can run in devices, allowing them to connect to FTP servers which send files requested by the client.
169
What does SSH stand for?
Secure Shell
170
What is the port number for SSH?
22
171
What is the purpose of SSH?
Used for remote management of computers. In order to access a remote computer, SSH require a username/ password combination and encrypts data during transmission.
172
What are SSH clients?
Pieces of software which can be used to make a TCP connection to a remote port. Once a connection is established, commands for application-level protocols can be sent to the remote computer.
173
What is the port number for the HTTP protocol?
80
174
What is the purpose of the HTTP protocol?
Web servers hold web pages in text form, which they can deliver using HTTP. Application software on the client receives these text files and renders them as web pages.
175
What is the port number for the HTTPS protocol?
443
176
What is the purpose of the HTTPS protocol?
HTTPS performs the same function as HTTP, but encrypts information during transmission. This prevents information from being tampered or modified with.
177
What does POP3 stand for?
Post Office Protocol
178
What are the port numbers for POP3?
110 and 995
179
What is the purpose of POP3?
Used for retrieving emails from a server. Email servers are responsible for receiving and sending emails. POP3 communicates with email servers to check for and download new messages.
180
What does SMTP stand for?
Simple Mail Transfer Protocol.
181
What are the port numbers for SMTP?
25, 587 and 465.
182
What is the purpose of SMTP?
Used for sending emails. SMTP is used between a client and an email server.
183
What the two parts an IP address is split into?
Network identifier and host identifier.
184
In a network, all the devices share the same ____ identifier, but have a different _____ identifier.
Network
Host
185
What is a subnet?
A smaller section of a network.
186
Every subnet has a different ___ identifier.
Network
187
What is the relationship between the number of bits allowed, devices and subnets?
The more bits assigned to the network identifier, the more different subnets that are available.
The more bits assigned to the host identifier, the more devices that can be connected to a subnet at one time.
188
What is IPv4 addresses?
Dotted quad numbers: consists of four parts that are separated by dots.
189
How many bits are assigned to each part of a IPv4 address?
8 bits (1 byte)
190
How many addresses can be represented on IPv4?
Over 4 billion (256^4)
191
Describe the appearance of IPv6 addresses.
Has 8 parts
Separated by colons
Uses hexadecimal
192
What is another term for a public IP address?
Routable
193
What is another term for a private IP address?
Non-routable
194
What a difference between routable and non-routable addresses? (Unique)
Routable IP addresses are globally unique, whereas devices can have the same non-routable IP addresses, as long as they are not on the same network.
195
What does DHCP stand for?
Dynamic Host Configuration Protocol.
196
What is the purpose of DHCP?
DHCP is used to assign IP addresses to devices as they join a network. DHCP uses a pool of available IP addresses to allocate IP addresses to new devices for the duration of their session. Once a device leaves the network, the IP address the device was using is returned to the pool for another device to use.
197
What does NAT stand for?
Network Address Translation.
198
Why does a router has two IP addresses?
One is a private address on the private network’s side and the other a public address on the Internet side.
199
Why do device on a private network have to send packets through the router and not directly to the server they wish to contact?
Because the device will be using a non-routable IP address, so won’t be unique. So the server cannot directly respond to the device, but the router’s public IP address is.
200
Describe the process of NAT.
1. Device wants to communicate with another device on the network.
2. Packets are sent to router.
3. Router makes a record of the packet and replaces the private IP address of the device with its own routable IP address.
4. When a response is received, it is sent to the router’s public IP address.
5. Router forwards the response to the correct private IP address by using the record it made when sending the packet.
201
When is port forwarding used?
When a client needs to communicate with a server that is connected to a private network.
202
Describe the process of port forwarding.
1. Client sends packets to the public IP address of the router on the private network.
2. Packets sent by the client contain the port number of the application running on the server that the client wants to access.
3. The private network’s routers forwards the packet to the server using NAT.
203
In client server models, what does messages sent contain?
Requested information, confirmation of the completion of the task or an explanation as to why the requested action hasn’t been completed.
204
Give three examples of different types of servers.
File server
Database server
Email server
205
What does API stand for?
Application Programming Interface.
206
What is API?
Set of protocols about how different applications communicate with each other. They define how interactions between applications should be carried out, allowing applications to make use of other applications.
207
What is the websocket protocol an example of?
An API which operates in the application layer.
208
Why is the websocket protocol used?
To provide a constant stream of information between two devices.
209
Describe the connection created by the websocket protocol.
Full-duplex, meaning that data can be transmitted in both direction at the same time.
210
What is the advantage of using the websocket protocol?
Reduces the size of packet headers, which allows for fast transmission of data.
211
In what scenarios is websocket protocol used?
Video streaming
Online games
Instant messaging
212
What does CRUD stand for?
Create, retrieve, update, delete
213
What the four commands CRUD used for?
Query online databases.
214
What is the SQL equivalent of Create?
INSERT
215
What is the SQL equivalent of Retrieve?
SELECT
216
What is the SQL equivalent of Update?
UPDATE
217
What is the SQL equivalent of Delete?
DELETE
218
What does REST stand for?
Representational State Transfer.
219
What is REST?
A design methodology for online database application that are queried with a web browser.
220
What four HTTP commands does REST use?
POST, GET, PUT, DELETE.
221
What is the SQL equivalent of POST?
INSERT
222
What is the SQL equivalent of GET?
SELECT
223
What is the SQL equivalent of PUT?
UPDATE
224
What is the SQL equivalent of DELETE?
DELETE
225
Describe the process of a client connecting a database.
1. Client-server request made by the client to the web browser.
2. Web browser responds with the requested web page, which is delivered as a text file.
3. This text file contains JavaScript which loads an API.
4. The API uses REST to enable the database server to be queried by the client with use of the HTTP request methods.
5. The client send HTTP requests to the database server.
6. The database server responds to the client’s request using either JSON or XML.
7. The client’s browser processes the JSON or XML and displays the response to the user.
226
What does XML stand for?
Extensible Markup Language
227
What does JSON stand for?
JavaScript Object Notation.
228
What are some advantages to using JSON?
More compact, easier for humans to read and debug and faster for computers to process.
229
What is an advantage of XML?
XML can be more flexible than JSON.
230
Describe a thin-client network.
Majority of the network’s processing power belongs to the server, which provides services and resources including storage and processing.
231
What are some advantages to using a thin-client network?
Easy to add new clients.
Clients are cheap.
Allows for greater centralised control.
232
What are some disadvantages of a thin-client network?
Require a powerful server, which is expensive and requires expertise to set up an maintain.
Suffer from high volumes of traffic communicating between client and server.
233
What are some advantages of thick-client networks?
Clients are powerful enough to do their own processing, so does not need a server.
No cost of having to set up and maintain a server.
Have quieter communication channels which reduces the likelihood of data collisions.
234
What are some disadvantages of thick-client network?
Clients are expensive to set up.
Harder to maintain because there is no facility to issue updates and manage security from a central server.
235
When is parallel data transmission commonly used?
Inside a computer for exchanging data between the processor and the main memory.
236
Why is parallel data transmission usually synchronous?
Usually used inside a computer, which has a clock signal to synchronise data transmission.
