1.4 Wired and Wireless Networks In this unit you will cover…

1. Types of Networks This lesson you will know: The purpose of networks The definition and difference between a WAN/LAN The definition of a Client-Server network The definition of a Peer-to-Peer network

L/O To be able to identify and describe basic characteristics of a computer network To be able to describe the main types of network infrastructure To identify the difference between the main types of network

Networks Networks are all around us; some are more obvious than others. You’d be pretty hopeless without them though Firstly; get it into your head that network isn’t exclusively a Computing term Think of all of the non-computer networks that we rely on daily… Friend/family groups Transport (roads, trains, busses, air-travel, etc.!) Electricity grid Without talking about computers, how could you define network?

Computer Networks We already have a nice idea of why Computer Networks are useful but that’s only scratching the surface of how much we use them 30 seconds – think of as many different different Computer Networks that you rely on from day-to- day

Networks You now know that a network is a group of things or people that are connected somehow A Computer Network is a set of devices (computers) connected together allowing them to communicate and share resources This isn’t limited to Desktop Computers. There are literally thousands of different networkable devices..

This astute lady is using her brain WAN/LAN You need to know the difference between a WAN and a LAN. It’s dead easy… WAN - Wide Area Network LAN – Local Area Network Switch-your-brain-on time; Look at both of them and take a wild stab in the dark as to what’s different about them – I’ve got all day This astute lady is using her brain

LAN Local Area Network These are Computer Networks that are restricted to a single geographic location Examples that you use all the time include your home wireless network and the school network

LAN - Characteristics Covers a small, local geographic area Ownership – usually the individual or organization owns and is responsible for all the equipment: Cables Switches Devices This equipment is dedicated – it’s not for anyone else! Administration – The owner is responsible for all administration of the network

WAN Wide Area Network These cover a large geographic area Some examples include: JANET (the academic network that links schools and universities) National Rail Network (tickets and times) Retail (stock management, statistics etc) The most obvious WAN that you probably didn’t think of is….

THE INTERNET (a WAN) The Internet is the biggest Computer Network in existence, and it is constantly growing The Internet is a collection of millions of computer networks that are connected together all across the world We’ll look at the Internet in a lot more depth in a later lesson

WAN - Characteristics Whereas a LAN depends on all its own network hardware a WAN will usually rely on external infrastructure For example; the school is connected to the JANET Academic WAN for internet however this network is carried over BT and Virgin’s cabling across the country Some WANs may use satellite, telephone lines, the internet. These links are SHARED and therefore not dedicated links.

Why different types? Why the different types of network? Some things we want to share with other networks, some we do not (internal/external) A way of identifying responsibility for different parts of large networks Do you want strangers half way across the world accessing your files or watching your network security camera?

Task Complete “activity 1” from the shared area Print and stick in your books

Exam Questions

Geographic!

Client-Server ¿Que? A server in a network provides a shared service or resource that is available to devices on that network The client (individual devices on the network) requests services from the server These could be; login; file; print; update; internet services (to name a few!)

Client-Server As the name suggests, a client-server network relies on a central server on the network Servers often need to be high-specification This is so they can run reliably and meet capacity requirements (all devices on the network are able to use them) They might have specialist networking hardware, additional processors, redundant hardware and backup power As a result they are often expensive and require maintaining to ensure consistent reliability

Real Life Let’s think about how school uses a Client-Server infrastructure Server: Login services File server Print server Internet filtering Software updates Security management Client Devices: All able to access the same resources Consistent whichever you logon to

Summary – Client Server A network which has one or more servers connected to it A server is a central point on the network which provides a function (e.g. log on, file storage) The server has control over the network This has significant advantages: Central security One point of back up Control over who can use the network and what they can do Central administration, distribution of software etc

Peer-to-Peer You may have heard the term “p2p” when talking about torrents/shady downloading Peer-to-Peer is when devices on the network ask other “equal” devices (“peers”) on the network for files or services There is no need for a central, super expensive server Each “peer” can act as a client and server; asking for and providing services

Peer-to-Peer Same with torrents Rather than the files all being stored and shared from one single location, the files are distributed from clients the same as your own on the internet This means the files may be available closer geographically No waiting for files to upload to a central server The demand for files can be distributed, avoiding congestion on individual servers or networks

Peer-to-Peer - Summary No central server; no need to keep a single computer running all the time No one machine is in control of the network Decreases time for data to send, fewer networks to send the call data through, reduced latency What does latency mean? An example of software that uses peer-to-peer is Skype

Peer-to-Peer vs Client-Server Complete the worksheet “Activity 2” Print and stick in your books When finished, expand on each type – give examples of where you would find them and explain why they are used in this situation – are there any negatives still?

Review You should know What a computer network is Why computer networks are so important The characteristics of the following common network infrastructures LAN/WAN Client-Server Peer-to-Peer Why some tasks require different types of network

Exam Questions Sample Question Paper - 8(a)