Fundamentals of Computer Networks for AQA GCSE Computer Science (8520) - Student Workbook, Study notes of Computer Networks

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Fundamentals ofTeach yourself^ the

Computer Networks for AQA GCSE Computer Science (8520)

Students Workbook By Nichola Lacey

Introduction Computer approach to help you learn networks surround u hows and computer this book has been written to give networks work and the different types of computer you a practical hands-on network b along. This helpsroken down into smaller, manageable chunks with practical tasks for you to perform as you gos there are to. Instead of chapters of technical jargon and mind ensure you understand the theory and remember it as you apply it to practical-numbing tedium the theory is

problems. How to use this book It is recommended that you start at the beginning and work through the chapters in order as each

chapter builds on the knowledge you have gained from the previous one. You are not expected to be a passive passenger on this journey computer networks work you will need to do a bit of work yourself. If you want to to achieve this. understand It is highly how recommended that you do perform the tasks as instructed, even if some of them seem a little bizarre. They are all included for a reason and will help you learn the theory behind representation given at the back (page. If you get stuck the answers, where there is a definite answer, to all the tasks are 36 ) of this book but try not to cheat and give the tasks a go. data

Who should use this book? This b examination (8520) and the objectives have been written specifically to match the syllabus, as ofook was specifically written to assist students preparing for their AQA GCSE Computer Science

February 2018. However, the theory and methods would be benefici know how computer networks work. al to anybody who wants to

What is a network? Objective: Define what a computer network is. Discuss the benefits and risks of computer networks.

A computer network is when two or more computers are connected so they ca each other. There are many ways this can be done and many forms that computer networks and we will be looking at these in this workbook. n communicate with take,

Server Most computer networks have at least one serve powerful computer that controls how the data movesr, a

around the network and allows the other computers on the network to store files on it. The server also often provides connections to other networks such as the internet and allows services such as email to be used. Servers can either be l accessed by highly trained technicians or on small networks one of the standard computers may takearge dedicated computers, locked away in air-conditioned rooms, and only on this role. Task 1: Make a list of advantages and disadvantages of using a computer network. Advantages Disadvantages

Computer network = when two or more computers are connected so they can communicate with each other

Types of network Objective: local area network (LAN), wide area network (WAN). Describe the main types of computer network including: personal area network (PAN),

Personal Area Network (PAN) Technology is surrounding us and many of our personal device communicate with each other. personal area network (PAN) is a computer network for an individual person and that's set up for A

personal use only. They typically invo connect to such as wireless headphones, a smart watch etc.lve a computer, phone, printer, tablet or anything else they

PANs often communicate with each other and will only work over a very small geographical area. use Bluetooth technology to

exchanging data over short distances using radio waves.^ Invented^ 1994, Bluetooth^ by the telecom vendor^ is a^ wireless^ technology for^ Ericsson^ in^ devices usually using^ PAN (Personal Area^ Network) connects^ Bluetooth

Local Area Network (LAN) A local area network (LAN) is a small network used by more than one person that covers a sma geographical area such as a single building. They are often owned or managed by a single person orll

organisation such as a business or school.

The LAN transmit which uses cables to transmit the data. later. s radio signals can either be wireless, in which to send data across We will look at these in more detail a little case a wirelessthe network or it may be a wired network access point (WAP) will

LANs (Local Area Networks) connect devices area such as a single building within a small geographical

Wired Objective: wireless networks as opposed to wired networks. and wireless networks Understand that networks can be wired or wireless. Discuss the benefits and risks of

Wireless different sign • Bluetooth local areaals: networks (WLAN) can use

• Wi-Fi Bluetooth 4.0 geographical area such as a PAN. together, but only if they are close together. has speeds of up to Bluetooth can connect 24 Mbp and is better over a very small up to seven devices Wi (WLAN). Wi uses a wireless access point to transmit data to multiple devices and are a better choice for WLANs.-Fi is a brand name which peopl-Fi allows device-to-device transfer speeds of up toe have adopted to mean wireless network 54 Mbps and Wired networks can use Copper “ethernet” cables are a popular • • Copper “Ethernet” cablesFiber Optic different types of physical connectionchoice for LANs. They transmit electric signal through the. Two of the most common are: central copper conductor. They are cheaper than fibre optic howeve high capacity if you need a very fast connection. r they do not allow the same

Fibre Optic cable using light pulses. They have a much higher bandwidth than ethernet ca connection. s are more expensive per meter than ethernet copper cables and transferbles and allow a fasters data

Networks) do not use cables to^ WLAN (Wireless Local Area connect devices together

Task How it works 3 : Complete the table below. You may have to do some research. Benefits Risks

Wireless

Bluetooth Wi-Fi

Wired^ Ethernet copper cables Fibre Optic

Star network topology

With a star topology every the centre of the network. Hub or Switch device on the network has its own dedicated line to the hub or switch at – This is a specific piece of hardware that is used in star pass that data onto the recipient computer.^ networks. All the data that travels around the network^ this piece of hardware. The difference between a hub or switch is how they^ must^ pass through A recipient A hubswitch will send the me (^) will pass the message ONLY to the correct recipient and will not send it anywherewill accept the message and all the other devices will ignore the message.ssage it receives to ALL the devices on that network and trust that the correct else.

• It is very reliable. If a connection between one computer and the hub/switch is broken the rest of the network will continue to^ Advantages^ Disadvantages
• workIt is easy to connect or remove devices without affecting rest of the network.
• There are controlled through the hub/switch which speeds up the data transfer around the network no collisions of data as it is all
  • • If the central hub/switch stops working the whole network will stop workingPurchasing the hub/switch is an additional
  • cost and this t^ cable and so is the most expensiveThe speed of the network depends on theype of network uses the most
  • capacity of the hub/switchWith a hub data on the network which can be a, all the devices are sent all the security concern. This does not happen with a switch

Star topology = all the devices connect to a

central hub or switch

Bus network topology

With a bus network each end of the cable a computer is responsible for sending message and listening to see if any messages on the network, all the device terminators “are connected to one central main cable called the “bus”. ”, which is fitted to stop signals reflecting down the bus. AtEach are meant for them. When a computer sends a message the bus and the device it is addressed to will pick it up using the bus topology,. All the other devices ignore the message and they transmit it in both directions along the terminators absorb the messages that get to the ends and stop them from bouncing back along the cable. Advantages Disadvantages the data

• • It is easy to install a bus networkIt is cheaper than a star netwo requires less cabling and does not need ark as it hub or a switch - • If the main bus is broken the whole network stops workingAs more devices are added the network will - become slower as there will be more data^ collisionsAll the devices are sent all the data on the network which can be a security concern.

Bus topology = all the devices connect to a

central cable

Task suitable to use 5 : Read the scenarios and decide which network topology would be most Scenario Star Bus A school classrooms and some computers in the library along with a teacher’s computer in ea spend. A large company want wants (^) ch classroom. They do not have much money toto set up a LAN which will connect three computings a reliable network for their staff and wants to minimise possible breakdowns and data clashes. Money is no object. A hospital need computer and printer in each ward to the LAN. If the system breaks down patients lives can be put at risk. There will be lots of devices on the network. s a high-speed reliable network that will connect a A factory need a few computers and a computer and printer in the manager’s office.s to link one computer and printer in the warehouse to printer in the accounts department and one

End of chapter recap Task 6 : Draw a line to link the phrase to the correct description

Phrase PAN (^) transmit data. The data can be transmitted using A type of network that does not use cables t Bluetooth or Wi Description - Fi signals o WAN^ LAN^ A copper cable that is used in a wired network that^ transmits data using electronic pulses that canA network topology t the devices^ its signal if used over large distances directlyhat uses cables to connect all to a central switch or hub^ lose WLAN Wired A large network over a large geo technology, which links people personal devices^ A very small network, usually using Bluetooth such as mobile phone an internet is one of thesedgraphical area. The headphones Bluetooth Wi-fi A small network which is contained over a smallA wireless frequency that is used with a WAP to geographical area such as a single building transmit and receive the signals Fibre optic^ Ethernet^ the devices connect to and which has terminators at^ A netwA radio frequency that is usually used in a wireless^ either end to absorb the messages to stop themork topology that uses a central cable that all^ reflecting^ along the cable PAN Star Bus connect the device to the network. These can be A connection that is used in a wired network that transmits data using light pulses and can be used^ A type of network that uses physical wires to either Ethernet or Fibre Optic cables over great distances

Once the message has been received successfully a message is sent back from the recipient computer to the sending computer to tell them to stop trying to send the message. If no message is sent either indefinitely or, more commonly, for a set telling the sending computer that the message has number been received correctly of attempts. If the recipient computer did, it will keep trying

not send the “message received” message, it would add additional and unnecessary traffic to the network that c Bandwidth ould slow the time it takes for other messages to get to their destinations.

Bandwidth is the amount of data that can be transmitted in a fixed amount of time per second (bps). The average bandwidth of different communication methods are measured in bits as follows: Method Bluetooth (^) Bandwidth 24 Mbps Wi Ethernet cable Fibre Optic-Fi 54 Mbps (^10020) Ghz Mbps Often a message may have to travel over start on a WLAN using Wi another network using Fibre Optic and finally connect to the local LAN using ethernet before finding-fi and then connect to a LAN using several different media when traveling over a WAN. It may ethernet cable and then travel to its destination computer.

This means that the bandwidth can change as the message progresses an data appear in a jumbled order so it is vitally important that a message is sent telling the receiving computer how to unjumble the message it receives. d this can often make the

Bandwidth = the that can be sent bits per second

connection^ through a^ network

Common Objective: UDP, IP, HTTP, HTTPS, FTP and email protocols (SMTP and IMAP). Explain the purpose and use of common n network protocols etwork protocols include: Ethernet, Wi-Fi, TCP,

Protocol Ethernet Wi-Fi (^) This is a group of protocols that deal of a LAN.Wi sent across a WLAN.-Fi is a brand name which defines group It describes how the packets are formatted and how to upload data. Purpose and Use transfers of protocols that describering data over the ethernet sections how data is UDP^ TCP TCP (Transmission Control Protocol) defines how^ network conversation^ be sent (usually over the internet)UDP (User Datagram Protocol) is an alternative communication protocol to the TCP.^ through^ which.^ applications^ to establish and maintai^ can^ communicate^ and data cann a HTTP^ IP^ IP (Internet Protocol)^ theHTTP (Hypertext Transfer Protocol) defines how web pages are formatted and transmitted and how webservers should cope with commands on webpages.^ Internet and includes a standard way for how devices are addressed.^ defines^ how^ data is sent from one computer to another on HTTPS FTP HTTPS (Hypertext Transfer Protocol Secure) is a secure version of HTTP which encrypts all data sent between the browser and the webpage. These are often used for payment pages on websites.FTP (File Transfer Protocol) this is a standard network transfer files. It can be used on LANs and WANs such as the internet. protocol that is used to protocols^ Email^ Ther^ Transfer Protocol)^ how messages are stored on a mail server but allows the end user to view and manipulate the messages as though they were stored locally on the end user's computer.^ ee^ - are two email protocolsmail messages are sent between servers and IMAP defines how email^ and IMAP (Internet Message Access Protocol). SMTP d^ you need to be aware of:^ SMTP (Simple Mailefines Local data transfer^ Task^ protocols may occur in more than one column.^8 :^ Grou p the protocols Internet^ we have looked at data transfer^ into the following categories. Email^ Some