A Level Computer Science Paper 1: 1.3.3 Networks - The Internet

A network of interconnected devices

A collection of resources accessible via the internet

A set of dedicated connectors that connect several large networks at different points on the globe

A unique identifier for each device on a network, IPv4 has four 8-bit values separated by dots

Specifies the means of accessing a resource across a network as well as its location
Handled by internet registries

The architecture used to map a URL to an IP address. Stored in a DNS server

Checked by the local DNS, the client’s known DNS server, the root DNS then the .co DNS until one can find the IP address

The first part of a URL, usually https:

The second part of a URL, the name of the server, often www.

The domain name is the name of the website e.g. ocr/bbc

The second domain name is usually the type e.g. .edu/.sch

Creating a communication connection between two endpoints for the duration of data transfer

The equal size chunks that data is broken down into and are received

The time taken for a packet to reach its endpoint

Routers store data about available routes to neighbouring routers in a routing table. The router will send the packet to the nearest router that doesn’t go backwards, this is repeated to the end destination.

A transfer of packets between routers

Tells the receiver which order the packets should be in

The sender and recipient’s IP address, the protocol being used, the time to live (hop limit) and packet number x of y

The end of packet flag and checksum/CRC (cyclic redundancy checking). Used to check the data has not been corrupted.

Typically 500-1500 bytes
Packets are small to ensure that packets don’t take too long to transfer but not too large that adding headers and trailers slows it down.

A set of rules, or a formal description, of the format of digital transmission

Transmission control protocol / internet protocol

A stack, top to bottom: application, transport, network, link

Defines what information is put together to send data and what protocol should be used, displays to the user on return

Splits the data into a series of packets and numbers each, requests retransmission of lost packets. Reorders packets upon receiving

Addresses packets with the source and destination IP addresses, removes on return.

Adds the MAC address of the source and destination or the router if across a different network, removes MAC address on return.

Media Access Control - Uniquely identifies a physical device with a network interface card.
A 48-bit 12-digit hexadecimal number

Used to alert a specific application to deal with data sent to a computer, used by a protocol to specify what data is sent

File transfer protocol - An application level protocol used to move files across a network

Use SMTP to send, POP3 to download from a mail server and IMAP to manage emails on a server. POP3 is only on one computer, IMAP across multiple.

Only open certain ports so only certain traffic can enter

Where the firewall inspects packets to see which port they are trying to enter

Makes a request on behalf of your computer, hides the request IP address from the recipient

Enables anonymous surfing, filters undesirable web content, logs user data with their request, produces a cache of previously visited sites

A collection of software robots which infect unknowing computers

Where a malicious user sabotages a network of infected computers to sabotage a website or server by sending many requests

The process by which cyber criminals take over a computer

Software which infects the computer that it is being run on

Redirecting a URL to send users to a malicious website

Fake emails or text messages created to look like they are from a legitimate source

Malware which requires you to pay a ransom to bypass it. Lock screen malware prevents access, encryption malware stops you accessing data

Mass distribution of unsolicited messages

A website or email address designed to appear like a legitimate source

Software which connects personal information without you knowing

A malicious program disguised as or embedded in legitimate software

Malicious computer programs intended to infect you and your contacts

Recording information communicated over an unsecure Wi-Fi network

A malicious program stored in memory which can self-replicate.

Hypertext Text Transfer Protocol

Simple Mixed Transfer Protocol

Internet Messaging Access Protocol

A type of attack in which the attacker creates a situation in which the user shares confidential information or performs actions that aren't usually performed

A device deigned to prevent unauthorised access to a network. Consists of two NICs between the user and the internet.