Networks

Networks

1. Networks allow devices to share information and resources.

   • LAN is a local area network located on a single site. All hardware is owned by the organisation that uses it such as a school.
   • WAN is a wide area network that connects LAN's that are in different geograpical locations. The internet is the biggest WAN.
   • PAN is a personal area network that belongs to a single user and user between mobile/wearable devices. Bluetooth can connect devices to make a PAN

2. Wired and Wireless

   • Network Interface Cards are a piece of hardware inside a device that allows it to connect to network. Used for both wired and wireless.
   • Switches are used to connect devices on LAN while routers transmit data between different networks and are most commonly used to connect to the internet.
   • Wired networks use cables to connect devices. E.g. Fibre optic, ethernet etc.
   • Wireless networks use radio waves. Local wireless networks are called WLANs . To set up a wireless network you need a Wireless Access Point device which is a switch. To connect devices need wireless capability or a dongle.
   • Wireless networks allow you to move around and are cheaper. Wired networks are more secure and less likely to be interfered with.

3. Topologies

   • Star topologies are devices connect using a central switch or server
     • No other devices fail if one does. Adding more devices is easy. Better performance than other topologies. Very few data collisions.
     • Can be expensive if wired. Switch is expensive. Whole program is affected if switch is. Max number of devices is deterimined by switch.
   • Bus topologies use a single backbone called a bus with devices connected to it. There are terminators on either side.
     • Rest of the network is unaffected if one device fails. Devices don't rely on switch. Relatively cheap.
     • Data collisions more common so slower. More devices means more data collisions. If bus gets broken then system may shut down.
   • Essential layout of the network.

4. Protocols

   • A protocol is a set of rules for communication of devices and transmittion of data across a network.
   • Network protocols are divided onto layers. A layer is a group of protocols with similar functions. Layers are self contained, protocols in each layer do their jobs without interfering with other layers. Each layer serves the layer above it. There are four layers.
     • Layer 4- Application layer: Providing networking services to applications. E.g. HTTP, FTP, SMTP
     • Layer 3- Transport Layer: Setting up communications between two devices, splitting data into packets and checking packets are correctly sent and delivered. E.g. TCP, UDP.
     • Layer 2- Internet Layer: Adding IP addreses to data packets, directing them between devices and handling traffic. Used by routers. E.g. IP
     • Layer 1- Link Layer: Passing data over the physical network. Responsible for how data is sent as electrical signals over cables, wireless and other hardware. E.g. Wi-Fi, Ethernet.
     • Layers breaks network communication into manageable pieces. Self-contained and can be changed without affecting others. Forces companies to make compatible and universal hardware and software.
   • TCP ans UDP are transport layer protocols. Control packaging and unpackaging of data.
     • . Transmission Control Protocol establishes connection between sending and recieving devices, splits data into numbered packets to be reassembled at destination. It communicates wihth recieving device to check all packets have been transferred correctly. Better when you need reliable connection.
     • User Datagram Protocol breaks data down into packets without numbering. Read by recieving device in order recieved. Only sends data once and doesn't check if data has been recieved. Better when you need fast, efficient transmission.
   • IP (Internet Protocol) is on internet layer and is responsible for establishing connection between routers and handling network traffic. IP addresses are unique numbers assigned to every device connected to an ip network. Responsible for directing data packets accross the internet using a process called packet switching. Which way data is sent depends on data traffic.
   • Wi-Fi is a family of protocols used in WLANs and operates on link layer. Units of data sent are called frames instead of packets. Wi-Fi uses two frequency bands- 2.4GHz for greater ranger and through walls or 5GHz for faster and shorter distances. The bands are split into channels. Networks using overlapping or adjacent channels can cause interference. It is important that data is encrypted.