Networks

Unfinished. These only include Year 10 content, sorry.

Reasons to use networks

• Share data and information

• Share resources

• Communicate and socialise

• Collaborate

• Centralised admin and security

Disadvantages of networks

• Cost

• Management

• Spread of malware

• Hacking risks

LAN

Local area network

Single, small geographical area

WAN

Wide area network

Large geographical area

Multiple LANs connected together

Protocol benefits

• Compatibility of devices between manufacturers

• Same order (broken into packets, sent, reassembled)

• Error-checking for corrupted / lost data

• Security - handles data encryption

Node

A device connected to a network

Computer adresses

IP addresses - LANs and internet - v4 has 2³² options, v6 has 2¹²⁸ options

MAC adresses - LANs

Bandwidth

Maximum amount of data that can be transmitted per second

Latency

Time taken for a transmission to reach its destination

Can be measured using ping

Transmission time

File size (bits) / network speed (bps)

Copper cables

Data transmitted as electrical pulses

More common than fibre optic

100m range

Slower transmission speed

Fibre optic cables

Data transmitted as pulses of light

More modern

Higher bandwidth, lower latency

Better range

Ethernet

A network protocol for wired LANs

Broadband types

Type of high-capacity internet connetivity

• FTTC (fibre to the cabinet) - used by homes

• FTTP (fibre to the premises) - used by businesses

Wireless transmissions

Done without cables, use micro and radio waves

Wireless limitations

• Limited range

• Easily interrupted and intercepted

• Lower bandwidth

WLAN

Wireless local area network

WAP

Wireless access point

Connects a WLAN to the internet

Wired vs Wireless

Wired:

• Expensive and difficult to install

• Not portable

• Large range

• Higher bandwidth

• Lower latency

• High reliability

• More secure

Wireless:

• Easier to install

• Portable

• Limited range

• Lower bandwidth

• Higher latency

• Reasonably reliable

• Less secure

Types of wireless connection

• Wi-Fi - high bandwidth / range / energy

• Bluetooth - medium

• RFID - very low

• NFC - very low

• Zigbee - low bandwidth / energy, medium range

Bus topology

Backbone which all computer are connected to with terminators at either end

If backbone breaks, network goes down, all devices see all data traffic

Star topology

Computer connected to one central hub / switch

Data sent directly to recipient, if hub breaks network goes down, lots of cables

(Partial) Mesh

All computers are (indirectly) connected to one another

Only achievable wirelessly, data takes the shortest route but is still seen by other computers

The internet

Each country has a backbone which is connected by NAPs

Networks connect by a PoP which is provided by an ISP

DNS convert URLs into IP addresses

Hacker

A person who attempts to gain unauthorised access to a computer system

Zero day vulnerability

A vulnerability the developers are unaware of / have not patched

Patch

Security fixes for existing software

Vulnerabilities easily exploited - can be found on the CVE database

Firewalls

Monitor and block incoming and outgoing connections to a network

Apply rules to data packets to check if they are authorised

Prevent access + prevent damage

Ethical hacking

Hacking in order to help organisations protect themselves from malicious hackers

E.g. penetration testing

Packets

Broken down parts of a file for transmission

Header features

• Addresses (sender and destination)

• Sequence number

• Checksum

• Type of packet

• Time to live

Email protocols

SMTP (simple mail transfer protocol)

POP3 (post office protocol 3)

IMAP (internet message access protocol)

Example file transfer steps

1. Click download file button on a website

2. Server connecting to file receives a request via internet

3. File broken down into smaller parts

4. Each part is put in a packet with correct information

5. Packets travel across internet to your IP via different paths and arrive in the wrong order

6. Computer reassembles packets into the file and missing packets are requested to be resent

Packet switching

Routers pass packets to other routers along the network - generally where there is the least traffic

Routing table

List of routes to other network destinations that helps routers determine where to send packets

NAP

Specialised high-performance routers that handle high-speed network traffic between countries

Layered protocol stack

Set of protocols that interact with one another but are not concerned with how the others work

Benefits of a layered protocol stack

Hardware/software for each layer has a defined responsibility

• Reduces complexity

• Devices can be manufactured for particular layers

• Devices from different vendors can work together

TCP/IP

Layered protocol stack that enable communication on the internet

Sender—>application—>transport—>internet—>link—>

link—>internet—>transport—>application—>receiver

Application layer

TCP/IP layer that has protocols responsible for user-based interaction

E.g. HTTP(S) - web, FTP - files, SMTP/POP3/IMAP - mail

Transport layer

TCP/IP layer that establishes a virtual connection between two devices and breaks down / joins together data packets

Uses TCP

Internet / network layer

TCP/IP layer that adds source and destination addresses and routing protocol identifier to the packet

Uses IP

Link / network interface layer

TCP/IP layer that defines how data is transmitted across connections

Mainly uses Ethernet and Wi-Fi