CompSci Theory 2

Questions on the Internet

Collection of web pages stored on computers all around the world and accessed via the internet

World Wide Web

Inter-connected networks

Internet

A unique number assigned to any item that is connected to the Internet.

IP address

Used to request and transfer hypertext data between clients and servers

HTTP

Used to write and create web pages.

HTML

A company that provides Internet access. BT is one example.

ISP

Secure version of HTTP. Encrypts communication between computers to protect from hackers.

HTTPS

Hypertext transfer protocol secure

HTTPS

The phone book of the internet. The service translates URLs to IP addresses.

DNS

Guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

TCP

Unit of data made into a single package that travels along a network path from one IP address to another.

Packets

A mode of data transmission in which a message is broken into a number of parts that are sent independently, over whatever route is optimum for each packet, and reassembled at the destination.

Packet Switching

A location or address identifying where documents can be found on the Internet; a Web address

URL

The portion of a web site address that identifies the type of site it is (.gov, .edu, .com).

Domain Name

Uniform resource locator

URL

Hypertext transfer protocol

HTTP

Internet Service Provider

ISP

Domain Name System

DNS

Transmission Control Protocol

TCP

Bandwidth

The amount of data that can be transmitted over a network in a given amount of time.

Latency

The delay before a transfer of data begins following an instruction for its transfer.

Speed of data transmission

Measured in Mbps (Megabits per Second)

Buffering

When a movie or music track plays faster than it downloads.

Time In Seconds (for download speed)

File Size In Megabytes / (Download Speed In Megabits / 8)

Coaxil cable

Carries signals from an aerial to electrical appliances including the television, cctv and digital satellite.

Ethernet or CAT-5 Cable

Cable that connects computers to the LAN that allows the computers to communicate with each other and other peripherals.

Fibre optic cable

A high performance cable that uses light to carry data

Broadband connection

A high speed connection to the Internet

Advantages of WiFi

No need to be physically connected

Disadvantages of WiFi

Must be close to a WiFi hotspot or router, slower than a wired connection, interference from walls and furniture, greater security risk

1 Byte =

8 bits \=

Network

A chain of communication that connects devices

LAN

A network of computers and other devices that is confined to a relatively small space, such as one building or even one office.

WAN

A network that spans a long distance and connects two or more LANs.

Topology

The physical layout of computers on a network.

Bus network topology

Computers in such a network are linked using a single cable.

Ring Network Topology

The network is configured in the shape of a circle with each node connecting to the next node. Messages travel around the circle in one direction.

Star Network Topology

Computers connected to a central switch. If one computer fails no others are affected. If the switch fails all connections are affected.

Switch

It stores the addresses of devices on a network and filters data packets to see which devices have asked for them. It will reduce latency.

Hub

Central, multi-plug adaptor for computers and printers in a network, enables communication between devices. A hub broadcasts data to all devices on a network.

Router

A device that transfers data from one network to another. Homes and businesses use this to connect to the internet.

Network Interface Card

A hardware component that enables computers to communicate over a network. Found inside computers, tablets and mobile phones.

Server

A computer designed to process requests and deliver data to another computer over the internet or a local network.

Wide Area Network

WAN

Local Area Network

LAN

Client/server network

A network that uses centrally administered computers, known as servers, to enable resource sharing for and to facilitate communication between the other computers on the network.

Peer-to-peer network

Any network without a central file server and in which all computers in the network have access to the public files located on all other workstations

Cloud computing

A system in which all computer programs and data is stored on a central server owned by a company (e.g. Google) and accessed virtually

Query

to ask, inquire

Database

A collection of organised data that allows access, retrieval, and use of data

Advantage of Client Server Network (backing up)

All data can be backed up centrally rather than on each individual computer.

Advantage of Client Server Network (protection from malware)

Anti-virus software can be kept up to date and run centrally.

Advantage of Client Server Network (security)

Security is better because data is held in one location rather than all over the organisation.

Advantage of Client Server Network (logging in)

Users can log in from any computer on the network.

Disadvantages of a client server network (cost)

Expensive to install as additional equipment is required

Disadvantages of a client server network (reliance on server)

If the server goes down the whole network is out of action

Disadvantages of a client server network (number of users)

Server can be overloaded and be slow if too many clients are using it.

Disadvantages of a client server network (additional staff)

Needs a network manager.

Network Interface Card aka..

NIC

Encryption

Process of converting readable data into unreadable characters to prevent unauthorised access.

Ciphers

A message in which letters or symbols replace the actual letters in the message

HTTPS

Hypertext Transfer Protocol Secure

Plaintext

Normal text that has not been encrypted

Ciphertext

Data that has been encrypted.

Encryption key

Used to encrypt and decrypt data.

Decryption

A process that reverses encryption, taking a secret message and reproducing the original plain text

Brute-force attack

A password-cracking program that tries every possible combination of characters.

Non-brute-force attack

Using clues such as a repeating phrase to get a starting point. Used at Bletchley Park during World War 2.

Caesar Shift Cipher

Each letter is replaced by the letter n positions further on in the alphabet.