Networks

• Two or more devices are connected together using networks. Files are sent from one device to another in the form of data packets.
• Data packets: a file sent over a network that has been broken into small chunks of data.
• Data packets are transmitted by the sender. At the receiver end, the file is re-built by arranging data packets in order.
• Protocols define the set of rules that control the way the data is sent over the network.
• Digital data is transmitted through the network with the help of error-checking methods such as parity and checksum.
• Any error due to the transmission channel is identified and corrected at the receiver's end.
• Advantages and disadvantages of using networks:

  A) Communication

  B) Monitoring user activity

  C) Controlling and updating workstations

  D) Roaming

  E) Sharing information

  F) Resource sharing

  G) Software streaming

  H) Dependence

  I) Security issues

  J) Setting up hardware

  K) malware

  
• A network can be anything from a connection of two devices to millions of devices that are connected together using the Internet.
• Types of networks: LAN, WAN, PAN, MAN, SAN, WPAN, VPN.
• Local Area Network (LAN) is a network of devices connected together in one physical location.
• Devices in a LAN don't need to be connected to the Internet.
• Wide Area Network (WAN) is a network of LANs in different geographical locations.
• WAN is provided by telecom companies.
• Personal Area Network (PAN) is a wired network used to connect personal devices in a home.
• Metropolitan Area Network (MAN) is used to connect devices in a city.
• A Storage Area Network (SAN) provides servers that enable users to store files on a large scale.
• Wireless Personal Area Network (WPAN) is a short-distance wireless network to connect mobile computing devices such as smartphones to desktop machines.
• A Virtual Private Network (VPN) is a type of network that creates a safe and secure connection for an organisation over the Internet.
• Safety and security is provided by encryption algorithms.
• Types of network models:

  1. Client-server.
  2. Peer-to-peer (P2P).
• Clients are computers that request information.
• Servers are computers that provide information.
• A client depends on the server for information.
• Client-server model: types of servers.

  1. Web servers.
  2. Application servers.
  3. Network Attached Storage (NAS).
  4. Print servers.
  5. Mail servers.
• Web servers handle the user's requests and manage the websites.
• Servers allow users to view HTML pages, CSS stylesheets and other scripts to the user.
• Large files can be hosted and shared using FTP.
• File Transfer Protocol (FTP) is a standard network protocol used for the transfer of files from one host to another over a TCP based network.
• Some websites contain programs and scripts.
• Application servers organise and run web applications.
• A client's request from a web browser is sent to application servers.
• NAS is a server that is responsible for storing and sharing files. This does not include websites.
• Print servers enable various devices to connect to a printer without installing printer drivers or connecting physically to a printer.
• Browsers are used to place a request to retrieve an email message.
• Mail servers store email messages.
• In a P2P network, every computer is responsible for providing data equally.
• In a P2P network, any computer can request data to any computer.
• In a P2P network, due to a lack of a server, it may lead to illegal file sharing and difficulty in storing back-up.
• Client-server.

  • Security: server controls the security.
  • Management: a team is required to install and manage the server.
  • Dependency: clients are dependent on the server.
  • Performance: performance can be improved if the server is upgraded.
  • Backups: backup is stored in the server.
• P2P:

  • Security: no main server to control security.
  • Management: anyone can setup.
  • Dependency: clients are not dependent on any server.
  • Performance: if an individual computer becomes slow, the whole network slows down.
  • Backups: individual computer backs up its data. This data can be easily deleted by users.