Networks and Topologies

What is a network?

Network - A system that allows computer systems to communicate and share resources with each other

Advantages of Networks

Can share peripherals via the network - e.g. printers
Can share files easily
Anyone on network can access their files from any computer on the network
Can control backups and security centrally

Disadvantages

Security risk - if server is hacked all the information vulnerable
Costly to set up
If a server fails, computers may not work
Computers may run slowly if lots of network traffic

Local Area Network

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

The Internet

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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

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

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

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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