Unit 5 Networks And Web Technologies

Question 1

Internet Service Providers

Answer 1

Connects directly to this backbone and distribute the Internet connection to smaller providers who in turn provide access to individual homes and business.

Question 2

Uniform Resource Locators

Answer 2

A Uniform Resource Locators is the full address of an internet resource. URLs are used to specify the means of accessing a resource across a network and its location. The protocol and the domain name of the resource together form the URL

Question 3

Domain Name System (DNS)

Answer 3

DNS servers are dedicated computers with an index of domain names and their corresponding IP addresses.

Question 4

DNS server structure

Answer 4

• There are 13 root DNS servers that work together to catalogue every domain name
• These are segmented into geographical groupings or levels
• When the IP address of a given domain is not known it is referred to a related domain server that may know

Question 5

Internet Register

Answer 5

Internet registrers hold records of all existing website names and the details of those domains that are currently available to purchase

Question 6

Internet Protocol

Answer 6

IP address is a unique address that is assigned to a network device. It indicates where a packet of data is to be sent or has been sent from. Routers can use address to direct the data packet accordingly.

Question 7

LAN

Answer 7

Local Area Network (LAN) is a network spread over a ​small geographical area

Question 8

WAN

Answer 8

Wide Area Network (WAN) is a network spread over a ​large geographical area​, that
typically requires ​extra hardware

Question 9

DNS

Answer 9

● Domain Name System
● The system given to the ​method of naming internet resources
● A hierarchy where each smaller domain is separated from the larger domain by a
full stop
● DNS server translates domain names into IP addresses when we access a website.

Question 10

Bus topology

Answer 10

Network topology where all ​terminals ​(devices) are connected to a
backbone cable

Question 11

Advantages of Bus Topology

Answer 11

Cheaper to set up, doesn’t require any

additional hardware

Question 12

Disadvantages of Bus Topology

Answer 12

If ​backbone cable fails​, the entire network gets disconnected
As traffic increases, ​performance decreases
All computers can ​see the data transmission

Question 13

Star Topology

Answer 13

Uses a central node (​switch/computer​) to direct the flow of data

Question 14

Advantages of Star Topology

Answer 14

Performance is ​consistent​ even if network is being ​heavily used
If one cable fails,​ only that station is affected
Transmits data faster​, so it gives better performance than bus topology
It’s easy to add new stations
No data collisions

Question 15

Disadvantages of Star Topology

Answer 15

Expensive​ due to switch and cabling

If the central ​switch fails,​ the rest of the network fails

Question 16

Mesh Topology

Answer 16

Every node is connected to every other node

Question 17

Advantages of Mesh Topology

Answer 17

No cabling cost
As nodes increase, the ​reliability and speed​ of network becomes better Nodes ​automatically get incorporated
It’s ​faster​ since nodes don’t go through a central switch

Question 18

Disadvantages of Mesh Topology

Answer 18

You have to purchase devices with wireless capabilities

Maintaining the network is ​difficult

Question 19

Circuit switching

Answer 19

It involves creating a communication connection between two endpoints for the duration of a phone call or transfer of data

Question 20

Packet switching

Answer 20

Packets are often sent across networks that have multiple connections with multiple routes through to a destination

Question 21

Data packets

Answer 21

When sending across a network, data is broken into chunks (units) called data packets and assembled again at the receiving end

Question 22

Routing

Answer 22

• Routers forward data packets from one network to another
• Each router stores data about the available routes to the destination node
• Looks up the destination IP address in its routing table to find the best router to forward the packet to
• Each transfer between routers is known as a hop
• Routers continue to forward the packet until it reaches its destination node

Question 23

Gateways

Answer 23

• A gateway is required where data is travelling from one network to another that use different protocols

Question 24

Circuit Switching advantages

Answer 24

The data arrives in a logical order which results in a ​quicker reconstruction​ of the data.

This enables two uses to hold a call without delay​ in speech.

Question 25

Circuit switching disadvantages

Answer 25

Bandwidth is wasted during periods of time where no data is sent. The devices must transfer and receive data at the ​same rate​. Since switches are used, electrical interference is produced which can corrupt​ or ​lose data​.

Question 26

Packet Switching advantages

Answer 26

There are multiple methods to ensure data arrives (check ​Checksum and ​Cyclic Redundancy Check​). There is more than one method of getting to the other devices, so if one path breaks you can use another. You can transfer packets over ​very large networks​ to allow communication globally.

Question 27

Packet Switching disadvantages

Answer 27

Time is spent deconstructing and reconstructing the data packets.

Question 28

Application Layer

Answer 28

. Based at the top of the stack . Specifies ​what protocol​ needs to be used in order to ​relate the application that’s being sent . Uses protocols relating to the application being used to transmit data over a network, usually the internet . For example, if the application is a browser then it would select a protocol such as HTTP, POP3, FTP

Question 29

Transport layer

Answer 29

* Uses the Transmission Control Protocol (TCP) to establish an end‐to‐end connection with the recipient computer * Splits data into packets and numbers them sequentially * Adds port number to be used based on HTTP protocol * At the receiving end this layer confirms that packets have been received and requests any missing packets be resent

Question 30

Internet layer

Answer 30

Uses the Internet Protocol (IP) to address packets with the source and destination IP addresses • A router forwards each packet towards an endpoint called a socket, defined by the combination of IP address and port number: 42.205.110.140:80

Question 31

Link Layer

Answer 31

The ​connection between the network devices Adds the ​MAC address​ identifying the ​Network Interface Cards​ of the source and destination computers

Question 32

On the recipient’s computer the layers occur again in reverse:

Answer 32

``` ○ Link Layer ■ Removes the MAC addresses ○ Network Layer ■ Removes the IP addresses ○ Transport Layer ■ Removes the port number and reassembles the packets ○ Application layer ■ Presents the data to the recipient in the form it was sent ```

Question 33

Firewalls

Answer 33

● Devices designed to ​prevent unauthorised access​ to a network ● Consist of two network interface cards (NICs), in-between the user and their internet connection. ● Perform packet filtering / static filtering ○ Limit network access​ in accordance with ​administrator rules​ and policies

Question 34

Client-Server

Answer 34

● Client-Server networks have ​terminals​ known as clients connected to a ​server ● The server is just a​ powerful central computer ● The server holds all of the ​important information​ and has ​extra processing power and the clients can request to use it

Question 35

Advantages of Client-Server

Answer 35

● More ​secure ● Central backups ​eliminate the need for client backups ● Sharing data and resources between clients

Question 36

Disadvantages of Client-Server

Answer 36

● Expensive​ to set up | ● Staff with training are required to maintain the server

Question 37

Peer-to-Peer networks

Answer 37

● Computers are​ connected to each other​ so that they can share files ● Inexpensive ​to set up ● Allow users to ​share resources ● Easy to maintain

Question 38

Proxy Server

Answer 38

• A proxy server makes a web request on behalf of your own computer, hiding the true request IP addresses from the recipient

Question 39

Functions of a proxy server

Answer 39

* Enables anonymous surfing * Can be used to filter undesirable online content * Logs user data with their requests * Provides a cache of previously visited sites to speed access

Question 40

Encryption

Answer 40

The act of encoding a plaintext message so that it cannot be deciphered unless you have a numerical key to decrypt it • If the message is intercepted it cannot be understood • If the key can be intercepted, the encryption process is rendered useless

Question 41

Worms

Answer 41

A worm is a standalone program that does not require a user to run it in order for it to spread. • Worms exploit vulnerabilities in the destination system and spread automatically

Question 42

Trojans

Answer 42

Trojans are malicious software programs that masquerade as innocuous or useful applications • They cannot self-replicate • Often they serve to open up back doors in your computer to the Internet so that the processing power, Internet bandwidth and data can be exploited remotely

Question 43

Phishing

Answer 43

Phishing is using email to manipulate a victim into visiting a fake website and giving away personal information

Question 44

Code quality

Answer 44

* Improving code quality, together with monitoring attempts to gain unauthorised access and protection can significantly reduce threats from malware * Measures include: * Guarding against buffer overflow attack * Guarding against SQL injection attack * Use of strong passwords for login credentials * Two-factor authentication * Use of access rights (file system permissions)

Question 45

Buffer overflow

Answer 45

* Buffer overflow occurs when a program accidentally writes data to a location too small to handle it * As a result the overflowed data (written to location #3 below) may end up in a neighbouring instruction space * Malware can deliberately cause and manipulate overflow data which may then be read as a malicious ‘instruction’

Question 46

HTML

Answer 46

● HTML is the ​language/script​ that ​web pages​ are written in, ● It allows a browser to ​interpret​ and ​render​ a webpage for the viewer by describing the​ structure and order ​of the webpage. ● The language uses tags written in ​angle brackets​ (, ) there are two sections of a webpage, a body and head.

Question 47

CSS

Answer 47

● CSS is a ​script/language​ like HTML except is used to ​describe the style​ of a webpage. ● CSS can be used to specify the way HTML elements look, they can be applied to whole tags such as

,

or

. ● CSS can be used using two different form, internal/embedded or external CSS the internal CSS is when the style is placed. ● The ​internal/embedded CSS​ is placed inside the style tags and is ​entered directly within the HTML document.

Question 48

JavaScript

Answer 48

● JavaScript is a language which has a similar layout to languages like ​python​. The main function of JavaScript is to add ​interactivity​ to websites. ● JavaScript isn’t ​compiled​, instead it is ​interpreted​, this is so it can be interpreted in the browser every time the webpage is displayed. ● Javascript be used to ​input data​ on the ​client's computer​, this may change the local page interactively or post data to a server. The advantages: ○ The local computer can fix invalid data before sending it off to the servers, ○ It can ease the traffic off of the busy servers,

Question 49

Classes and Identifiers

Answer 49

``` ● Class and identifier selectors are the names which you style, this means groups of items can be styled, the selectors for html are usually the div tags. ● Identifiers are defined with an initial hashtag, and must be unique to each webpage. ● Classes are defined with a full stop as a prefix to the class name, classes can be used multiple times on a webpage. ```

Question 50

Network

Answer 50

A ​network​ is the name given to ​two or more​ computers connected together with the ability to ​transmit data​ between each other. There are two main types of networks: ​local area networks​ and ​wide area networks.

Question 51

HTTP (Hypertext Transfer Protocol)​

Answer 51

Used for web page rendering, an encrypted version, ​HTTPS (Secure)​, is becoming more common

Question 52

TCP/IP​ ​(Transmission Control Protocol / Internet Protocol)

Answer 52

This is a networking protocol used in the routing of packets through networks

Question 53

POP3 (Post Office Protocol)​ and ​IMAP (Internet Message Access Protocol)​

Answer 53

Mailing protocols, used for email access.

Question 54

FTP (File Transfer Protocol)​

Answer 54

Used for the transmission of files over networks.