GCSE J277 Unit 1.3 Computer Networks PDF

GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Name: Deepak Loganathan Specification and learning objectives By the end of this topic, you will have studied: Types of netwo...

GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Name: Deepak Loganathan Specification and learning objectives By the end of this topic, you will have studied: Types of network: LAN, WAN Factors that affect network performance The different roles of computers in a client-server and peer-to-peer network The hardware required to connect standalone computers to a LAN: Wireless access points, routers, switches, NIC, transmission media The internet as a worldwide collection of computer networks: DNS, hosting, the cloud, web servers and clients Star and mesh network topologies Modes of connection: Wired (Ethernet), wireless (Wi-Fi, Bluetooth) Encryption IP and MAC addressing Standards Common protocols: TCP/IP, HTTP, HTTPS, FTP, POP, IMAP, SMTP The concept of layers Resources We recommend the OCR-endorsed text book from PG Online for use during your GCSE studies. Craig ‘n’ Dave videos for SLR 1.3 GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Types of networks Representation of a local area network (LAN): Representation of a wide area network (WAN): Description of a local area network: Description of a wide area network: Covers a small geographical area. Covers a large geographical area All the hardware for a LAN is owned by the organisation using Infrastructure between the LAN’s is leased from it. telecommunication companies who own and manage it. It is usually wired with fibre optic and wireless using wifi etc. WAN’s are connected with telephone lines or satellite links. Computers in LAN are connected with a switch. Computers that are not connected to a network are called standalone computers. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave The advantages and disadvantages of networks The advantages of networks include: Users can share files,peripherals : printers and connections to other networks. Users can access their files from any computer on the network. Communication with other people Servers can control security, software updates. The disadvantages of networks include: Increased security risk to data Malware and viruses spread very easily between computers If the servers fail the computer connected to it may not work The computer may run more slowly if there is a lot of data travelling on the network. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Factors that affect network performance Too many users on the same device on the same network can cause the network to slow down if there is insufficient Number of users bandwidth for the data Less reliable connections increase the number of errors that occur when data is transferred. Error rate The signal quality of wireless connections is dependant on the range of devices from the wireless access point and other environmental factors. Wired connections have a higher bandwidth than wireless connections Transmission media Fibre Optic cables have a higher bandwidth than copper cables Bandwidth Amount of data that can be sent and receive successfully in a short period of time. The delay between data being transmitted and a user’s device receiving it, latency is caused by bottlenecks in Latency network infrastructure. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave The different roles of computers in a client-server and a peer-to-peer network Both local area networks and wide area networks can use either a client-server or a peer-to-peer approach when sharing data. Client server Peer to peer on cti ne n co al gic Lo A server controls access and security to one shared file storage A peer is a computer on a network and is equal to all other A server manages access to the internet peers Server manages printing jobs Peers serve their own files to others Server provides email services Each peer is responsible for its own backup and security Server runs a backup for data Peers usually have their own printers A client makes requests to the server for data and connections You can send print jobs to another peer to process but that peer would need to be switched on to be able to communicate with the connected printer GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Advantages and disadvantages of client-server and peer-to-peer approaches to data sharing Client-server model Peer-to-peer model Advantages Advantages Easier to manage file security. No dependency on a single machine. Easier to take backups of all shared data. Very easy to maintain – specialist staff are not required. Easier to install software updates. Cheaper to set up – no expensive hardware required. Disadvantages Disadvantages Can be expensive to set up and maintain. Less secure. Requires IT specialists to maintain. Users need to manage their own backups. Single point of failure. Difficult to maintain a well-ordered file store. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Hardware for a local area network Transmission media Copper cables UTP Transmission media Wired connections assure maximum (Fiber Optic cables) bandwidth,security and reliability. The Uses light to transmit Switch grade of copper and insulating material data. Cover much longer Sends data between computers on a affects the quality of the overall cable and distances and greater LAN. They segment the network by therefore the bandwidth. With twisted bandwidth than copper. forwarding traffic to the correct pair cables the wires are twisted around The backbone of The location. each other to reduce inference Internet uses fibre optic cables. Network interface card Router Wireless access point Every computer connecting to Sends data between networks. It Allows a wireless enabled devices to network will need one of these. creates a WAN from a number of LANs connect to a network without cables. More They use a protocol to determine how You cannot connect to a WAN without convenient. They have less bandwidth than the connection should work. using a router. A router uses an IP a wired connection. Security is more of a They allow a device to connect to address to route traffic concern with wireless connections. either a wired or wireless network. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave The internet The internet is: A collection of interconnected networks spanning across the world. Google server Internet service provider Domain name service Request www.google.com www.google.com → 8.8.8.8 Domain name service Hosting The cloud A DNS server translates a domain name Storing of files and data on a web server. Servers can be used to store data and into an internet address. The web server is referred to as host. programs that can be accessed and used Every website on internet has a network The URL of a website includes the host over Internet. address - four digits. name. Advantages - Addresses like this are hard for user to Host name - 3 levels - reverse Access anytime remember - instead websites use Top -.com;.uk;.net;.gov Access anywhere domain names - for ex: bbc.co.uk Second -.co;.org;.sch Access from any device Third - bbc, ocr, apple Large storage capacity Automatic backup Easy online collaboration GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Domain Name Service URL in: www.google.com How a domain name service works: 1. The URL is received by a DNS resolver/server. 2. The server then queries a DNS root name server. 3. The root server responds with address of Domain name service top-level domain server -.com 4. The resolver then makes a request to the.com TLD server. 1. DNS recursive/resolver server 5. The TLD server then responds with IP address Receives URL request from client browser. of domain’s name server, google.com 6. Lastly, the recursive resolver sends a query to the domain’s name server. 7. The IP address google.com is then returned to the resolver from name server. 8. The DNS resolver then responds to the web browser with IP address of google.com 2. Root name server 3..com top level domain server 4. Authoritative name server Hold the records for holds records for all.com Holds the IP address of.com,.org,.gov etc. domains google.com domain → 8.8.8.8 GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Web servers, clients and the cloud The cloud The relationship between servers and clients on the internet: Web servers carry out many functions: - Hosting websites Excellent backup and recovery options. - Dealing with client req. - HTTP get req, for page/resource Web Page stored as text is sent to browser which uses rules to Accessibility – access your data anywhere, anytime. render it correctly for the user. Room for growth – easy to scale up/expand. Url request made from client. Browser sends domain name to a DNS. No hardware required – everything is hosted in the cloud. DNS maps the domain name to an IP address and returns to the browser. Web server Client Disadvantages Ongoing monthly/annual cost for hosting data. Get request for webpage/resources is returned to clients web browser Requested webpage / resource is returned to clients web browser. Bandwidth is dependent on network speed. Client File server Relies on a stable internet connection. Less control over data. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Star network topology GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Star network topology The biggest weakness of a star network topology is: the whole network fails if the switch fails as no node can communicate Full mesh network topology The advantage of connecting computers together in a full mesh topology is: If you get a break in any of the connections you can still route your traffic via another route. The disadvantages of connecting computers together in a full mesh topology are that: There is a lot more cabling and switch hardware required which will add cost for large networks. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Partial mesh network topology The internet is an example of a partial mesh network: GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Mesh wireless network topology GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Mesh wireless network topology The advantages of a wireless mesh network topology are: - require only one node in the network to be physically wired for internet connection - can be configured dynamically for speed - Use less power - They offer reliability as each node is connected to several other nodes. The disadvantages of a wireless network topology are: - Lack of centralization can also make routing and resource management processes difficult. - Have more latency as data must hop through several different nodes. - Lack of central system make mesh systems more complicated to monitor, troubleshoot. - Initial network setup can be complex GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Wired modes of connection – Ethernet Ethernet is a Standard for networking used for communication on a Wired local area network technologies Ethernet has largely replaced competing wired LAN technologies. The original Ethernet used Coaxial cable as a shared medium while the newer Ethernet uses Twisted pair and fibre optic links with a switch to connect components together. Over the course of its history, Ethernet data transfer rates have increased from the original 2.94 megabits per second to 100 gigabits per second. Systems communicating over Ethernet divide a stream of data into shorter pieces called Source and destination address Each contains a frame and a Cyclic redundancy check used for error-checking so that damaged transmissions can be detected. Ethernet provides networking protocols up to the Data link layer of the open standards interconnection model. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Wireless modes of connection – Wifi and Bluetooth - It avoids the need to install - Ideal for connecting personal cables. devices. - Bandwidth low than a wired - Short range connection. - Ideal for connecting wireless - Users can move freely keyboard, or a wireless - Relies on signal strength to the headphone. wireless access point (WAP) Wi-Fi Bluetooth Range 100 meters Range 10 meters Bandwidth high Bandwidth Low Power consumption high Power consumption Low GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Benefits and drawbacks of wired versus wireless connections Wired networks Wireless networks Advantages Advantages Transfer speeds tend to be faster. Users can access the network from anywhere in range. Connections tend to be more reliable. Sharing files tends to be easier. More secure/easier to secure. Less physically complicated and disruptive to set up. Disadvantages Disadvantages Lots of physical hardware required. Transfer speeds to be slower. Connection tends to be less reliable and can be blocked User’s location is limited by the need for a cable connection. by walls and other physical infrastructure. Sharing files tends to be more difficult. Less secure/more difficult to secure. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Recommending a connection for a specific scenario A local school comprises a set of very old buildings that were built long before the modern internet took shape. The school wants to install a teacher’s PC in each classroom, and students should be able to connect to the network from any location. Reliable connections are required, but fast data transfer speeds are not essential. State whether you would recommend a wired, wireless or hybrid solution and provide reasons to back this up. A brand-new, state-of-the-art building is being designed for a large-scale corporate business. It is essential that the business has a very reliable, fast and secure data transfer on its network. State whether you would recommend a wired, wireless or hybrid solution and provide reasons to back this up. GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Wi-Fi encryption A wireless device broadcasts an SSID to other devices, enabling connections to be made between devices on the same network. An older encryption method called WEP has been replaced by a more secure method called WPA. A master key is created and used to encrypt and decrypt data between two wireless devices. A simple illustration of how master keys can work using a substitution cipher: character B A S I C S U B S T I T U T I O N C I P H E R key 1 3 4 8 7 3 4 3 7 6 1 7 6 8 8 9 6 9 1 3 4 8 7 cipher text C D W Q J V Y E Z Z J A A B Q A S L J R L M Y character s h e b i n t h a t i s w h a t s h e s a i d key 1 5 8 3 4 2 6 8 5 9 4 3 5 7 2 7 8 5 3 1 4 6 9 cipher text S F R W G J I K U X B G A W Q N M L O P G T H GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Wi-Fi encryption Wireless device Before communication between devices takes place, each wireless Wireless device device is authenticated as having the correct master key using a four-way handshake – this ensures that data can only be sent and received by devices who have the correct master key. ⓿ ⓿ Master key is generated from the STA wireless password. ANonce ❶ STA constructs PTK ❷ SNonce + MIC AP constructs the PTK Group temporal key is calculated and sent with a message integrity code. ❸ ❹ Ack GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave The uses of IP addressing (IPv4 and IPv6) and MAC addressing There are two types of addressing used for local and wide area networks: MAC address Media Access Control Address - Used to route frames on a LAN IP address Internet Protocol Address - Identify a host computer or node which communicates over the Internet or IP The reason we have IPv6 is: - Due to exceeding number of IoT we had to replace IPv4 The results of the ipconfig /all command on a Windows machine showing an IPv4, IPv6 and MAC address: GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Standards and protocols The need for standards: Standards serve as benchmarks for the quality and performance of networking components and systems A network protocol is a set of rules governing the communication between devices on a network. Some protocols include: HTTP Hypertext Transfer Protocol A client-server method of requesting and delivering HTML files. HTTPS Hypertext Transfer Protocol Secure Encryption and authentication for client-server data. SMTP Simple Mail Transfer Protocol Sends mail to a mail server. Sending files between computers. FTP File Transfer Protocol Used for uploading web pages and associated files to a web server for hosting. POP Post Office Protocol Used by email clients to retrieve email from a mail server. Used by email clients to retrieve email from a mail server IMAP Internet Message Access Protocol and manage remote mailboxes. Better than POP. Transmission Control Protocol/ Provides an error-free transmission between two routers (TCP) TCP/IP Internet Protocol and routing of packets on a wide area network (IP). GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave The concept of layers The concept of layering is used to divide the complex task of networking into smaller, simpler tasks that work with each other. The hardware and/or software for each layer has a defined responsibility. Each layer provides a service to the layer above it. Browser The advantages of layering include: using Layer 4 HTTPS - Reduces the complexity of the problem into manageable sub-problems. - Devices can be manufactured to operates a particular layer. - Products from different vendors will work together TCP, Error- Layer 3 handling Layer 2 IP routing MAC, Layer 1 frames (Sent over fibre optic) GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Assessment Target: Overall grade: Minimum expectations by the end of this unit □ Learn terms 61-96 from GCSE Level Key Terminology. □ Complete all pages of the workbook. □ Score 80% in the end-of-unit test. Feedback Breadth Depth Understanding □ All aspects complete □ Excellent level of depth □ All work is accurate □ Most aspects complete □ Good level of depth □ Most work is accurate □ Some aspects complete □ Basic level of depth shown □ Some work is accurate □ Little work complete □ Little depth and detail provided □ Little work is accurate Comment and action Student response GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Reflection and Revision checklist Confidence Clarification ☹😐☺ I can explain what a LAN is. ☹😐☺ I can explain what a WAN is. ☹😐☺ I can explain factors that can affect network performance. ☹😐☺ I can explain the difference roles of computers in a client-server and peer-to-peer network. ☹😐☺ I can explain the hardware required to connect to standalone computers in a LAN. ☹😐☺ I can explain what a wireless access point is. ☹😐☺ I can explain what a router and switch is. ☹😐☺ I can explain what a network interface card is. ☹😐☺ I can explain what transmission media is. ☹😐☺ I can explain what the internet is. ☹😐☺ I can explain what DNS is. ☹😐☺ I can explain what hosting is. ☹😐☺ I can explain what the cloud is. ☹😐☺ I can explain what web servers and clients are. ☹😐☺ I can explain what a star network is. ☹😐☺ I can explain what a mesh network is. My revision focus: GCSE J277 Unit 1.3| Computer networks, connections and protocols Craig’n’Dave Reflection and Revision checklist Confidence Clarification ☹😐☺ I can explain what is meant by a wired and wireless network. ☹😐☺ I can explain various modes of connection such as Ethernet, Wi-Fi and Bluetooth. ☹😐☺ I can compare the benefits and drawbacks of a wired connection versus a wireless connection. ☹😐☺ I can recommend one or more connections for a specified scenario. ☹😐☺ I can explain what network encryption is. ☹😐☺ I can explain what IP addressing is and the IP address formats IPv4 and IPv6. ☹😐☺ I can explain what a MAC address is. ☹😐☺ I can explain the principle of a standard to provide rules for areas of computing. ☹😐☺ I can explain what the TCP/IP protocol. ☹😐☺ I can explain what the HTTP and HTTPS protocols are. ☹😐☺ I can explain what the FTP protocol is. ☹😐☺ I can explain what the POP protocol is. ☹😐☺ I can explain what the SMTP and IMAP protocols are. ☹😐☺ I can explain the concept of layers. My revision focus: