GCSE CS Communication and the internet

GCSE CS Communication and the internet

1. Types of networks

   • WAN
     • A wide area network. It covers a large geographical area which may be a city or the world! The internet is the ultimate WAN. This can be made up of interconnected LANs and makes use public telecoms facilities.
   • LAN
     • a local area network. Most organisations have a LAN, which is confide to one site e.g. an office or university. It also connect all the organisations equipment together.
   • Network speeds
   • Client-server
     • Is the most common network, this has one or more servers providing services to many clients’ machines where the user works. Servers are used to do different jobs in the network.
   • Peer-to-peer
     • In a Peer-to-peer network, all computers are equal, each computer serves the needs of the users as well as carrying out network functions.

2. Wired and wireless connectivity

   • Wired
     • Whereas wired uses cables like copper (cheaper than fibre) or fibre optic (fibre being much faster at transiting signals) this is a physical connection tot he network
   • Wireless
     • Wireless uses radio waves to send data through wireless access points or a router.
   • Network hardware
     • Network interface controller cards (NIC’s)  Cables  Hubs  Switches  Wireless access points  Routers  Server

3. Data transmission

   • Packet switching - Packets are sent individually across a network. Packets form a message may take different routes according to the traffic within the network. They are forwarded from one router to the next. This improves the reliably of sending the messages as many route may be used if one way is down.
   • Packets contain – Protocol; total length; senders address; receivers address; time to live; packet number and data.
   • Calculation transmission time  Step 1 – Convert the file size back to bits  Step 2 – convert the transmission speed from Mbps to bits per second  Step 3 – Divide the bits by bits per second  This will find out the transmission time
   • TCP/IP Model - is the set of protocols used over the internet. It organises how data packets are communicated and makes sure packets have the following information: source - which computer the message came from; destination - where the message should go; packet sequence

4. Protocols

   • are the rules that computers must follow when they are communicating and sending and receiving data over a network
     • Needed to ensure that data is sent and received across a network

5. Topologies

   • Bus: the computers and devices are attached to a single backbone, where terminator are attached to prevent reflection of signal.
   • Star: Client machines are connected to a central switch or hub.
   • Ring: Data passes through each node, carried in data units called tokens, traffics is one-way.
   • Mesh: where each computers is connected to all the other computers in the network

6. Network security

   • Access Control
     • Setting users to have different rights to files and data stored on a network e.g. read, write or read write to folders
   • Ethical computer hacker
     • A security hacker (or ethical computer hacker) is someone who seeks to breach defences and exploit weaknesses in a computer system or network to testing and in other testing methodologies to ensure the security of an organization's information systems.
   • The importance of network security:
     • Confidentiality - An organisation's computer system often holds data about its people (employees and customers). It could not run efficiently if its customer’s data is breached
     • Correctness - Data is useless unless it is correct. Use of the network to communicate and store data must not change the data or allow the date to be changed.
     • Availability - A network is useless if data cannot be accessed when it is needed. If it fails it can affect the business and customers.
   • Authentication
     • through username and password
   • Physical security
     • Locked doors
     • CCTV
     • Biometric security recognition
   • Firewalls
     • Protects a network connected to a WAN, preventing program and user accessing the network or internet

7. Cyberattacks

   • A cyberattack is any kind of electronic attacks on a computer system, server, network or other IT device. To gain access to data, Delete or modify data or Physically damage a device
     • Types of attacks
       • Technical weakness
         • Unpatched software: Software that hasn't has the latest security update applied to it, making it vulnerable to attack.
         • USB devices: USBs that could contain malware that could be transferred to your system or copy data to the attacker via the internet
         • Eavesdropping: Intercepting data being sent to/from other computers systems.
       • Human behaviour weakness
         • Social engineering: This exploits human behaviour are often referred to as social engineering attacks that attacked will engineer a situation where the target person gives away confidential information or access to a system
         • Phishing: Attempt to give sensitive, confidant information from the user (e.g. username and password) via email or fake websites.
         • Solder surfing: To gain access to information by directly observing a user as they enter personal detail (e.g. PIN number or username/password)
   • NAS: Network-attached storage (NAS) - this is hardware that is connected to the network (this is a hard drive or multiple hard drives), uses can access their data via the internet through apps. However they can be more hackers

8. The internet

   • WWW
     • World Wide Web (WWW) – This is one facilities that makes use of the internet with billions of web pages written in HTML
   • Is the connecting of millions of computers and computer networks across the world through routers, servers and cabling.
   • ISP – Internet services provider. -
   • DNS – Domain name system(this matched the URL with the IP address, like an address book)
   • - HTML – hypertext Mark-up Language (this is a way of using text files in order to show them on the web)
   • URL - Uniform resource locator(this is the domain name remember the domain name relates to the IP)
   • Assessing the World Wide Web 1. The user of a computer enters the web address. A web address is also known as a URL 2. The computer uses a system called the Domain Name Service (DNS) to find the IP address of the required web server. 3. The web browser connects to the web server using the IP address and requests the relevant web page or other object (picture, sound or video file). 4. A web page is transferred from one computer (normally a web server) to another using HTTP or HTTPS. 5. Data sent from a web server to a web browser is in HyperText Markup Language (HTML) format. The web browser displays the web page as described by the HTML.

9. A networking is a collection of connected computers plus their peripheral, with each device on a network called a node.

Images and files in the map

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• GCSE 1.4 Client server and peer to peer networks (Embed)
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• Wifi vs. Ethernet! (Embed)
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• Network Theory Topology (Embed)
• GCSE 1.5 The concept of layers (Embed)
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• GCSE 1.5 The uses of IP, MAC addressing and protocols (Embed)
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• Cybersecurity: Crash Course Computer Science #31 (Embed)
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