computer networks, connections + protocols

What are the two types of networks?

• LAN (Local Area Network)

• WAN (Wide Area Network)

What are the characteristics of a LAN?

• It connects computer systems over a small geographical area, like in a school

• It is owned and managed by the network owner

What are the characteristics of a WAN?

• It connects computer systems over a large geographical area, like in a country

• It is often managed by internet service providers like BT

What is the largest WAN?

The internet.

What factors affect the performance of networks?

• Number of devices connected

• Bandwidth

What are the roles of computers in a client-server network?

The client is the computer that makes requests to the server.

The server is the computer that manages said requests and responds to them.

What are the roles of computers in a peer-peer network?

Each computer can act as a client or server.

What are the key pieces of network hardware?

• WAP (wireless access point)

• Router

• Switch

• NIC (Network Interface Controller/Card)

• Transmission media

What is the role of a WAP?

To allow wireless (Wi-fi enabled) devices to connect to a wired network by creating a wireless local area network.

What is the role of a router?

To transfer data packets between different networks by:

• connecting networks to the internet

• assigning computers IP addresses

• directing data packets using IP addresses

• storing IP addresses in a routing table (to calculate most efficient way to transfer data)

What is the role of a switch?

To connect computers within a LAN by:

• using MAC addresses to identify devices

• sending data directly to an intended destination

What is the role of an NIC?

To allow a computer to connect to a network by having a unique MAC address and exchanging data between the device + network.

What is the role of transmission media?

To connect devices in a network together.

EX: ethernet cables

What is network topology?

The way in computers are connected in a network.

How are computers connected in a star topology?

Each computer is connected to a central server such as a hub or switch.

What are the advantages of a star topology?

• If one device fails, all others are unaffected

• Computers can be added to the network by directly connecting them to the switch

• Improved security and performance as data is sent directly to the switch

What are the disadvantages of a star topology?

• If the central server fails, the whole network will fail

• Expensive to install wiring in larger networks as each computer requires a cable

How are computers connected in a mesh topology?

Each computer is connected to every other computer.

What are the advantages of a mesh topology?

• If one cable/computer fails, data packets can take an alternative route

• Traffic can take multiple other paths due to the number of possible routes

What are the disadvantages of a mesh topology?

• Expensive and complex to set up due to the number of cables

• Some connections may be unnecessary where the computers are unlikely ever to communicate

• High maintenance due to the number of connections

What is the internet?

It is a global network made up of many other networks.

What is a domain name service (DNS) made up of?

Multiple domain name servers.

What is the role of a domain name server (DNS)?

To convert website URLs into IP addresses.

How does a DNS convert website URLs into IP addresses?

1. A domain name is searched in a browser.

2. A query is sent to the local DNS server for the corresponding IP address of the domain name.

3. The local DNS checks whether it stores an IP address corresponding to that domain name.

4. If yes, it passes the IP address to the browser.

5. The browser then accesses the website by connecting to the IP address of the server.

What is the role of web hosting?

To provide clients with access to web pages 24/7 by storing website files on servers.

How does web hosting work?

A client requests access to a web page.

As a result, the server transfers the website file to the client in response.

What is the cloud?

A remote service provision that has multiple purposes like storing data, running applications and processing on remote severs.

What are the advantages of the cloud?

• Ability to access files from anywhere and any device (with an internet connection)

• Automatic built-in backups

• Huge capacity and ability to increase it

What are the disadvantages of the cloud?

• Require internet connection

• No control over the way data your data is stored and high risk of a data breach by hackers

What are the two ways in which a network can be connected?

• Wired connection (requires NIC)

• Wireless connection (requires WNIC)

What is the most common type of wired connection?

Ethernet

What are the two most common types of wireless connection?

• Wi-fi

• Bluetooth

What are the benefits of using a wired connection over a wireless connection?

• Faster data transfer speeds

• More secure

What are the weaknesses of using a wired connection over a wireless connection?

• Restricted movement of devices as they must stay connected

• More expensive as it requires the physical installation of cables

What are the benefits of using a wireless connection over a wired connection?

• Cheaper to install and easier to connect (more) devices as no cables needed

• Free movement of devices as they are not restricted by a cable

What are the weaknesses of using a wireless connection over a wired connection?

• Slower data transfer speeds

• Less secure

• Prone to interference

What is encryption?

The process of scrambling data into a coded format that can only be decoded using the correct decryption key.

What is the purpose of encryption?

To secure data across network connections (particularly wireless ones which are less secure).

How does encryption make a network more secure?

It ensures only authorised users have access to confidential data.

It protects data if it is intercepted during transmission as the attacker cannot decipher the data without the correct decryption key.

What is a (network) protocol?

A set of rules for transferring data across a network that enable computers to communicate with each other.

What are the most common protocols?

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

• HTTP (Hyper Text Transfer Protocol)

• HTTPS (Hyper Text Transfer Protocol Secure)

• FTP (File Transfer Protocol)

• POP (Post Office Protocol)

• IMAP (Internet Message Access Protocol)

• SMTP (Simple Mail Transfer Protocol)

What is the purpose of the TCP/IP?

The TCP divides data into packets and reorders them back into the original data at the destination.

The IP uses the IP addresses of the devices on the network to route and address the data packets so that they arrive to the correct destination.

What is the purpose of the HTTP?

It transfers web pages from servers to browsers.

It’s used when you see "http://" at the start of a URL.

What is the purpose of the HTTPS?

It is the secure version of HTTP that encrypts data during transmission.

What is the purpose of FTP?

It enables the transfer of files between computers over a network.

It is commonly used to upload/download files to/from a web server.

What is the purpose of POP?

It deletes emails stored in the mail server once they have been received and downloaded to the device.

What is the purpose of IMAP?

It stores emails on a remote mail server so that they can be accessed from any device.

What is the purpose of SMTP?

It is used to send an email to or between mail servers.

What are the two types of IP addressing currently used?

• IPv4

• IPv6

What are the key features of IPv4 addressing?

• Each address has 32 bits

• Represented in denary

• Four 8-bit segments (0-255)

• Separated by full stops

EX: 145.13.218.102

What are the key features of IPv6 addressing?

• Each address has 128 bits

• Represented in hexadecimal

• Four 16-bit segments (0000-FFFF)

• Separated by colons

EX: 2001:DB8:3333:4444:5555:6666:7777:8888.

What is a MAC address?

A unique hexadecimal number assigned to an NIC inside a networked device.

What is the purpose of a MAC address?

It allows a network to uniquely identify any device each time it connects to it.

It cannot be changed like an IP address.

What is the format of a MAC address?

It is a 48-bit address made up of 8-bit hexadecimal pairs, separated by dashes.

EX: 00-1B-63-84-45-E6

What are standards?

A set of rules for computing that allow hardware and software to interact across different manufacturers/producers.

What is a protocol layer?

A division of network functionality.

What are the key features of protocol layers?

• Each layer provides a specific network function to assist the transmission of the data being sent

• Layers operate independently but work together

• Data passes through multiple layers when sent over a network

What are the benefits of using layers in protocols?

• Each layer functions independently:

  • allowing changes to one layer without affecting others

  • enabling developers to specialise in specific layers

• Enables standards development for individual layers, ensuring compatibility

• Allows manufacturers to develop hardware specifically for particular layers

• Groups similar protocols together for better organization