Transcript Networks
Week 1 Lesson 1 Computer Networks – the basics In this project, you will be learning about the computer networks which we use every day – when we log on at school, go on the internet at home or school, send an email, do a web search We’ll be investigating some important questions such as … • How does the internet work? • How does data get from one computer to another? • How do emails send? • How does the data/emails know Starter – getting connected Write down all of the devices in your household which are connected to the internet or to each other. In today’s lesson: Lesson Objectives • Understand what a network is and the 2 main types of network • Understand the advantages and disadvantages of networking • Understand the devices needed to create a computer network Success Criteria ALL: Successfully demonstrate an understanding of what a network is MOST: Successfully explain the advantages and disadvantages of networking and will state some devices needed for networking SOME: Be able to explain the purpose of the devices needed to create a local area network. Literacy -Today’s key words What is a Computer Network? Two or more computers connected together to share information and resources. This could be by physical cables or wireless connections, or both Local Area Networks - LANs • A LAN is a Local Area Network. • It is a connected set of computers and other devices. • Each device is called a node (e.g. computer, printer, etc.). The computers are called workstations • A LAN is installed on one site. – Relatively small – It is owned by the organisation Local Area Networks- LANs A school network A home network An local office network Wide Area Networks - WANs • A WAN is a Wide Area Network. • It created when LANs are connected. • You need media such as broadband cables to connect up the networks • Which is the biggest WAN of them all?? A WAN is installed across more than one site. – Could be very large – Could go across several countries/businesses – Might not be owned by anyone – which WAN would this be? Networks- the basics Learning Check … On your whiteboard: 1. What is a Computer Network? 2. What does LAN stand for? 3. Give an example 4. What does WAN stand for? 5. Give an example Advantages / Disadvantages It’s a lot of work and expense to set up a network, and you need someone to manage it. So why bother? What do you think the advantages and disadvantages are of having computers networked instead of having lots of ‘stand alone’ computers? Think about your devices at home or the school network/ Discuss with a partner and be ready to share your thoughts. Local Area Networks - LANs Advantages • It allows communication between people using the devices eg staff or students • It allows data to be shared between users • It allows peripherals (e.g. printers) to be shared • It allows computers to be upgraded more easily • It allows a single program to be run simultaneously at various computers. Local Area Networks - LANs Disadvantages • Expertise required to set up and maintain a large network (costly) • If the network ‘goes down’, everything comes to a stop! • Security issues from unauthorised access to data – Measures to secure a network include: • • • • Passwords – strong passwords use a range of character types Changing passwords frequently Not allowing users to install software With wireless access, use encryption What hardware is needed to create a network? + + + + You’ll need • At least two computers or other devices (also known as Nodes in a network) • Each having a NIC – network interface card (either wired or wireless, aerial might be built in) – The NICs convert the data signals from the nodes into data signals that can be transferred across the network. • You might need a server - A computer that holds data to be shared with other computers. A web server stores and shares websites. What hardware is needed to create a network? You’ll also need a way to transfer the data from one device to the router then onto the next device/network (also known as Data Transfer Media) – Wires: usually an Ethernet cable – Wireless Technology: Wi-Fi, Bluetooth What hardware is needed to create a network? Hub A device that connects nodes together. OR Not intelligent – data is sent to all nodes across the whole of the network. Cheap devices – USB hubs useful in home computer installations. Switch A device that connects nodes together. An intelligent device that can sends data to the nodes that the data is intended for. This reduces network traffic because making the network run faster. What hardware is needed to create a network? You’ll also need a router to “route” the data around your network This might be provided by your ISP…… You also need an ISP if you want to connect to the Internet • ISP = Internet Service Provider • For a monthly fee, they will provide broadband internet access, which might be by fibre optic which is very fast! • They might provide you with other services too eg phone, TV. • Who is your ISP? Networks- the hardware Learning Check … On your whiteboard: 1. What is the name of the commonly used cable used to connect up a network? 2. Which device sends the data around the network? 3. Which is more intelligent – a hub or a switch? Networks are represented in network diagrams What to do now • Make a new folder in your work area called Computer Networks • Log into Moodle • Go to ICT & Computing > Year 8 > Digital Networks > Week 1 • Download to your documents the presentation called Network Basics (not to downloads, put it in your newly created folder!) • Open it and complete slides 1 – 4, save it! Plenary – define today’s key words Week 1 Lesson 2 Computer Networks – network layouts Literacy -Today’s key words Starter Recap – on your whiteboards …. • List 3 hardware devices you’ll need to create a network • Explain what an ISP does • Give 1 advantage and 1 disadvantage of a network In today’s lesson: Lesson Objectives • Understand that networks can be laid out in different ways • Understand the advantages and disadvantages of different network layouts Success Criteria ALL: Successfully identify different network layouts MOST: Successfully explain the advantages and disadvantages of different network layouts SOME: Be able to explain how the data moves around each type of network layout, and the difference between P2P and Client-Server networks. NETWORK TOPOLOGY Topology is the mathematical study of shapes and nodes. In computing, devices are nodes and they can be connected together in different ways to create networks. The structure of a network is known as its topology. There are three main types of topology that you need to know. • Mini web and info on each type including an animation (no sound) which might be more interesting: • http://www.teachict.com/gcse_new/networks/topologies/miniweb /index.htm NETWORK TOPOLOGY BUS NETWORK A bus network has a central cable that all devices connect to. Only one device can access the bus at a time. There are terminators at each end of the bus network. If a device wishes to communicate on the network it first checks to see if there is any traffic on the network. If there is it waits a random period of time and tries again. If it can communicate then it will send the message to the device it wants to communicate with. NETWORK TOPOLOGY BUS NETWORK NETWORK TOPOLOGY BUS NETWORK Advantages Disadvantages Less cable need than other types. Heavy traffic can cause network failure and delays Relatively cheap and easier to install and maintain. If the main cable fails or gets damaged, the whole network will fail Easy to add new nodes by removing terminator As more workstations are connected, the performance of the network will become slower because of data collisions If a workstation/terminal goes down the others will continue. Every workstation on the network 'sees' all of the data on the network, which can be a security risk NETWORK TOPOLOGY RING NETWORK In a ring network, each device (eg workstation, server, printer) is connected in a ring so each one is connected to two other devices. A ring has no central host computer and none of the nodes need to have overall control of access to the network. Each data packet on the network travels in one direction. Each device receives each packet in turn until the destination device receives it. An imaginary token is continuously passed around the ring. A token is a small packet that contains bits of data which passes around the ring (Always the same way around). If a computer is waiting to transmit, it catches a token and with it the authority to send data. It attaches its data. The NETWORK TOPOLOGY RING NETWORK Advantages Very high transmission speeds are possible. Routing between devices is simple because messages normally travel in one direction. As data is in one direction it can transmit large volumes of data Disadvantages If the main cable fails or any device is faulty, then the whole network will fail - a serious problem in a company where communication is vital Cabling costs can be high. Difficult to extend the ring NETWORK TOPOLOGY STAR NETWORK The Star network is the most commonly used network topology in use today. Each device is connected directly to a central computer (usually through a switch). Your home network is a star, connecting through the wifi router. The school network is also a star network. NETWORK TOPOLOGY STAR NETWORK Advantages Very reliable – if one cable or device fails, then all the others will continue to work and the central CPU can identify any faults High performing as no data collisions can occur Central control of message switching allow a high degree of security Disadvantages Expensive to install as this type of network uses the most cable, and network cable is expensive Extra hardware is required hubs or switches - which add to the cost If a hub or switch fails, all the devices connected to it will have no network connection PEER TO PEER NETWORKS All stations are joined together in the network have equal status. If you have a number of computers at home on sharing a wireless router then this is the type of network you will probably have. Each device shares the connection to the Internet, whether that is a tablet, games console or computer. Each computer can give rights of access to other computers, so data or devices can be shared. CLIENT - SERVER NETWORKS • A client-server network has different types of computers. • A powerful central computer called a server manages the client computers the users use. • The data is stored centrally. This means that it does not matter which client computer the user logs on to, they can still access all their work. • The client machines can be controlled and managed from the central computer. • Data can be backed up centrally. • This is the network we have at school. Network layouts Learning Check … On your whiteboard, which networks do these describe? Put B for Bus, R for Ring, S for Star, P2P for Peer to Peer, C/S for client-Server 1. 2. 3. 4. 5. 6. 7. 8. Has a central cable that all devices connect to. Routing between devices is simple because messages normally travel in one direction If a hub or switch fails, all the devices connected to it will have no network connection There are terminators at each end Very reliable – if one cable or device fails, then all the others will continue to work Every workstation on the network 'sees' all of the data on the network, which can be a security risk All stations are joined together in the network have equal status This is the network we have at school. What to do now • Find your presentation from last lesson – Network Basics. • You should already have completed slides 1-4. You now need to complete slides 5-12. • Make sure your name is in each footer. • Print as handouts, back to back, to reduce paper use! o If you weren’t here: Make a new folder in your work area called Computer Networks o Log into Moodle. Go to ICT & Computing > Year 8 > Digital Networks > Week 1 o Download to your documents the presentation called Network Basics (not to downloads, put it in your newly created folder!) Open it and complete all slides!