1.3 | Computer networks, connections and protocols

• The Internet is a huge network of networks. The World Wide Web makes us able to connect and communicate with people and services throughout the world.
• A network is two or more computers/devices that are connected together for the purpose of communication. They are connected by a wired medium e.g., cables or by a wireless medium e.g., Wi-Fi.
• A Local Area Network is a computer network within a small geographical area. For example, a school, office or at home. It is used for data transmission by computing devices within one building or site.
• A Wide Area Network is a network that is spread over a wide geographical areas. It can cover more than one site, or be spread across the world. It connects separate LANs over a large geographical area.
• A server is a computer that provides files on demand to client machines. It also manages and stores the files.
• A client is a computer that acts as a desktop for users and which relies on a server for its operations.
• Client-server networks are a type of network topology that is used in a network where a server is responsible for providing services to clients.
• File servers are responsible for holding and maintaining user files.
• Applications servers allow programs to be run over a network.
• Web servers hold and share web pages.
• Print servers manage printing across a network.
• Mail servers handle emails between users.
• Servers make communication with other users easier.
• Security in servers are better as users can not access each other's files, unlike stand alone computers.
• Servers can be very expensive due to the network cabling and switches also being expensive.
• Larger networks require dedicated staff to manage and maintain them.
• Large networks are a target for viruses.
• In a LAN, the organisation owns all the hardware (cabling, switches, servers etc.)
• Peer-to-peer networks are a type of network topology where devices are directly connected to each other. All of the computers on this network are equal.
• Each computer in a peer-to-peer network act as both a client and a server and can communicate directly with all of the others.
• Computers on a peer-to-peer network are responsible for backing up procedures.
• The most common way of connecting computers into a network is to use star topology.
• A cheap or overloaded switch will slow the network down for everyone.
• Fibre optic cables have the advantage of being able to transport data over much greater distances. They are also not affected by electrical interference.
• Network performance are affected by

  • The number of users using the network
  • Bandwidth
• Bandwidth is how much data the network is capable of transmitting.
• The client is dependent on the server to provide and manage the information in a client-server model.
• An example of a client-server model is when websites are stored on web servers. The web browser is the client which makes requests to the server and the server sends the website to the browser.
• Peer-to-peer is ideal for sharing files. Though it would be unsuitable for services such as booking tickets. This is because one server needs to keep track of how many tickets are left.
• A Network Interface Card (NIC) is a device that connects a computer to a network. This can be for connecting using a cable to a wired network or connecting using a wireless network. The NIC has a circuitry to convert the signals from the network into a form that can understand.
• On wired networks, NICs will use a RJ45 connector on an ethernet cable. The cable may plug into a wall socket but will eventually be connected to a hub or switch.
• Wireless Access Points transmit signals from the network so that they can be read by the wireless NIC on the computer system.
• Computers on a wireless network will connect to a wireless router. A router is a device that joins different networks together.
• The access medium is the wires, cables and fibre. This is the actual connection. This may be wired with a (ethernet cable) fibre optic cable. Often it can be wireless using radio waves to connect devices together.
• Networks use a switch, which is ver similar to a router, to connect devices together. It consists of many sockets allowing ethernet cables to be plugged in.
• In home networks, the router and the WAP are often in the same box.
• All wired networks use transmission media to connect the network components.
• The simplest transmission media is an ethernet cable, which has a standard plug at each end and is very simple to configure.
• Fibre optic cables are a type of transmission media that are more difficult to install and require special equipment. These provide higher speeds and can be used over greater distances.
• Mobile phones, tablets and laptops use a wireless NIC to connect to a Wireless Access Point.