Networks

A local area network (LAN) is a group of computers and devices that are connected together within a small geographical area, such as a home, school, or office building.

Owner of LAN is responsible for connections

Wide Area Network

A wide area network (WAN) is a group of computers and devices that are connected together over a large geographic area, such as a city, a country or even across the world. For example the internet

The owners of the WAN use existing network infrastructure to connect the sites together

Factors that affect network performance

Bandwidth

Bandwidth refers to the amount of data that can be transmitted over a network in a given amount of time. Networks with higher bandwidths can transmit more data, which can improve performance.

Measured in bits per second, referred to as bit rate

The number of devices on the network

Too many users or devices on a network can cause the network to slow down, if there is insufficient bandwidth for the data

Transmission Media

Wired Connections have a higher bandwidth than wireless connections.

Fibre optic cables have higher bandwidth than copper cables

Latency

Latency is the delay from transmitting data to receiving it

Latency is caused by bottlenecks in the infrastructure of the network
For example, by not using switches appropriately segment traffic on a network
Hardware such as switches and transmission media may not operate at the same speed

Client and peer-to-peer networks

Client - A device capable of obtaining information from a server.

Server - A computer which manages access to a centralised resource.

Peer - Someone/something of the same status or ability.

Client - Server

The network relies on a central server.
All clients (devices) request services from the server (e.g. print services/file services).
Additional hardware would be needed e.g. high end powerful servers.

Advantages

Easier to manage security files.
Easier to take backups of all shared data.
Easier to install software updates to all computers.

Disadvantages

Can be expensive to setup and maintain.
Requires IT specialists to maintain.
The server is a single point of failure.
Users will lose access if the server fails.

Peer-to-peer

All computers have equal status.
Each device can act as a client and a server.
All devices can request and provide network services.
No additional hardware/software needed to set up this type of network.

Advantages

Very easy to maintain.
Specialist staff are not required.
No dependency on a single computer.
Cheaper to set up.
No expensive hardware required.

Disadvantages

The network is less secure.
Users will need to manage their own backups.
Can be difficult to maintain a well ordered file store.

Network Hardware

Wireless Access Point (WAP)

allows wireless enabled devices to connect to a network without cables
more convenient
They have less bandwidth than a wired connection
Security is more of a concern with wireless connections
Connection is sometimes not as strong or reliable as wired connections

Switch

Sends data between computers on a LAN
They segment the network by forwarding traffic to the correct location.
Switches learn which devices are connected and understand how to forward traffic in an intelligent way.

Router

Sends data between networks

It creates a WAN from a number of LANSs
You cannot connect to a WAN without a router.
A router uses an IP address (Internet Protocol) to route traffic

Network Interface Card (NIC)

A network interface card allows a computer to connect to a wired network.
A NIC allows data packets to travel to and from a computer
A NIC contains a MAC address which is a physical hardware address
A NIC allows an Ethernet cable to be plugged into this

Transmission media

Ethernet(cat 5e/Cat6)
Known as twisted pair
A networking standard
Fibre optic
Very fast cable but also more expensive(often used with WAN or larger LANs)
Coaxial Cable
An older networking standard

Topologies

What is a Topology?

A network topology describes the way the network is arranged / laid out

Star Topology

A star topology is a type of computer network topology in which all devices are connected to a central device or switch. In a star topology, each device is connected to the hub or switch using a separate cable.

Advantages:

needs fewer cables (cheaper)
is easier to add and remove devices
it is easy to troubleshoot

Disadvantages:

if the central switch fails, the entire network fails
causes a bottleneck when the network is busy

Mesh Topology

A mesh topology is a type of computer network topology in which each device on the network is connected to every other device.

Messages can find different routes
The internet is an example of a mesh

Partial Mesh

In a partial mesh, most devices are connected to several other devices
In a full , every device is connected to all other devices

Advantages of mesh topology:

allows packets to be routed around bottlenecks
is more reliable as a single failure won't stop the rest of the network

Disadvantages:

needs more cabling (expensive)
is more complicated to add or remove devices
is more complicated to understand and troubleshoot

Physical Bus Topology

In a BUS Topology all computers are connected to a single cable, the ends of the cables are plugged into a terminator.

Advantages

Inexpensive to install as it requires less cable than a star topology and does not require any extra hardware

Disadvantages

If the main cable fails, no network data can be transmitted to any of the nodes
Performance degrades with heavy traffic
Low Security - all computers on the network can see the data transmissions.

The Internet

What is the internet

The Internet is a collection of inter-connected networks.

The internet is a Wide Area Network (WAN)
A WAN uses cables, telephone lines, satellites and radio waves to connect, usually spread over a wide geographical area

Packet Switching

When you want to send a file of 4Mb across the Internet, the file is broken up into data "packets" of 512 packets.

Each packet is given a header containing

The IP (internet protocol) address it is going to
The IP address it has come from
The sequence number of the packet
The number of packets in the whole communication
Error checking data

The these packets are then forwarded to their destinations using routers

Uniform Resource Locators (URLs)

A uniform resource locator (URL) is the full address of an internet resource. It specifies the location of a resource on the internet, including the resource name and typically the file type, so that a browser can request it from the website server.

Internet Registries and Registrars

Internet registrars hold records of all existing website names and the details of those domains that are currently available to purchase. These are companies that act as resellers for domain names and allow companies and people to buy them. All registrars must be accredited by their governing registry.

There are only 5 Internet Registrars around the world and are governed by the Internet Corporation for Assigned Names and Numbers (ICANN) each of these registrars covers certain regions of the planet. Below is a map of the regions covered by their assigned Registrars

Attribution: Rir.gif: Dork BlankMap-World6,_compact.svg: Canuckguy et al. derivative work: Sémhur (talk), Regional Internet Registries world map, CC BY-SA 3.0

Domain Name System (DNS) and Domain Names

A domain name identifies a the area of domain that an Internet resource is located. These are structured into a hierarchy of domains and written as a string separated by full stops as specified in the rules of the Domain Name System (DNS). Where TLDs stands for Top Level Domains , 2LD - 2nd Level Domain and 3LD - 3rd level domain.

Geek Fact - Tuvalu has the country code top-level domain ".tv" which is sold to television broadcasters and media companies

Here is a breakdown of the URL for this website

Fully Qualified Domain Name (FQDN)

A fully qualified domain name is one that includes the host server name, e.g www. , .mail etc... This can be written as www.websitename.co.uk

IP Addresses

An IP (Internet Protocol) address is a unique address that is assigned to a network device. An IP address is similar to a home postal address.

142.250.179.179 is the IP address of the website at the time of writing

An IP address indicates where packets of data are to be sent or where they have been sent from. Routers can use this address to direct the data packets accordingly.

IP addressing - IPv4

Stands for Internet Protocol version 4
It is written as 4 blocks of denary number between 0 and 255, separated by full stops.
E.g. 192.164.0.1
It provides over 4 billion unique addresses - which sounds a lot - but there are are over 8 billion people on the planet and every phone, laptop, smart plug , computer and router needs its own address

IP addressing - IPv6

Due to the shortage of IPv4 addresses, IPv6 is now used as well, though some older devices don't support the new format.
To solve this problem, new devices have both IPv4 and an IPv6 address so that they can work on any network
IPv6 addresses are represented using 8 blocks of 4 hexadecimal digits, separated by colons
E.g. 4164:3122:6C6F:8665:6C62:6365:2043:4B3B
When displayed, an IPv6 address will often miss leading zeroes, so ... :6365:0001:2043: … might appear as … :6365:1:2043: …
This gives us 3.4x1038 unique addresses – which means that we are very unlikely to run out of IP addresses in the near future.

MAC addressing

MAC stands for Media Access Control
Written as 12 hexadecimal digits, usually grouped in pairs.
Every MAC address is completely unique
E.g. E0-26-D4-6C-A7-44
MAC addresses are static - they can never change. No matter which network you are on, your MAC address will stay the same.

Hosting

Hosting is the storing of files and data on a web server. The web server is referred to as a host.

The URL (uniform resource locator) for a website includes the host name. For example, the host name GeekResources.co.uk is included in the URL www.GeekResources.co.uk.

The process

Web server hosts the websites
User enters URL in web browser (google , Bing ,etc..)
Web browser sends request to the DNS for the IP address that matches the URL entered
A request for that IP address is then sent to the web server, and the webpage is returned to the user to view

Protocols

A protocol is a set of rules designed to ensure everyone involved is on the same page - e.g fire alarm protocols
Networks which control the communication between devices on a network.

TCP ( Transmission Control Protocol)

Breaks up messages sent over the Internet into small chunks called packets
Reassembles the packets at the other end
Detects errors
Resends lost messages

HTTP - Hyper Text Transfer Protocol

Used by web browsers to access websites and communicates with webs servers.

HTTPS - HTTP Secure

A more secure version of HTTP. Encrypts all information sent and received.

FTP - File Transfer Protocol

Used to access, edit and move files between devices on a network, e.g. to access files on a server from a client computer.

POP3 - Post Office Protocol- version 3

Used to retrieve emails from a server. The server holds the email until you download it, at which point it is deleted from the server

IMAP - Internet Message Access Protocol

Used to retrieve emails from a server. The server holds the email until you delete it - you only download a copy. Used by most web-based email clients.

SMTP - Simple Mail Transfer Protocol

Used to send emails. Also used to transfer emails between servers.

The Cloud

Server can be used to store programs and data that can be accessed and used over the internet

This is known as "The Cloud"

Advantages of The Cloud:

access any time
access anywhere (with connection to internet)
access from any device
a large storage capacity
automatic backup
easy online collaboration

Disadvantages:

Not in control of back ups
Need the internet to access
Cost is not fixed, may change
Security and privacy concerns: Cloud services require users to store their data on third-party servers, which can lead to security and privacy concerns. There is a risk of data breaches, hacking, and unauthorized access to sensitive data.

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