Networks - By Junior, Shabazz and Ferdinand

LAN- Local Area Network
1. Covers a small geographical area
  1. LANs are either wired with ethernet cables or wireless using Wi-Fi
    1. Will often find LANs in businesses, schools and universities
      1. Why Use A LAN?
        Sharing files is easier as network users can access the same files
        You can share the same hardware like printers
        The internet connection can be shared between every device connected to the LAN
        You can work collaboratively on files at the same time
        You can install and update software on all computers at once rather than one-by-one
        You can communciate with LAN user cheaply and easily for example with internet messaging
WAN- Wide Area Network
1. A WAN connects LANs that are different geographical locations
  1. Organisations hire infrastructures (e.g. communication lines) from telecommunications companies who own and manage the WAN
    1. This is because a WAN is much more expensive to set up than a LAN
    2. WANs may be connected by fibre or copper telephone lines, satellite links or radio links
    3. The biggest WAN is the Internet
Factors Affecting The Performance Of Networks
1. Bandwidth, which is the amount of data that can be transferred in a given time
  1. The greater the bandwidth, the better the network can perform
  2. The amount of users on a network; too many users or heavy use may cause congestion and slow the network
    1. Wired/Wireless connection; wired connections are generally faster and more reliable. Wireless connection performance depends on signal quality which can be affected by range and physical obstructions
      1. Type of cable; Fibre optic cables give much better performance than copper cables
      2. Wi-Fi is the standard used for wireless networks.
        -uses two radio frequency bands — 2.4 GHz & 5GHz
        Bands are split into numbers channel that each cover small frequency
        Wi-Fi performance is affected by interference between networks using adjacent channels
  3. Choice of hardware and network topology can also have a big effect on the performance of a network
Hardware
1. NIC- Network Interface Controller; an internal piece of hardware that allows the device to connect to a network
  1. Coaxial Cables- made of a single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference:
2. Switches- connects devices to a LAN. They receive data in frames from one device on the network with the correct MAC address
  1. Cables — CAT 5e/6, Coaxial and Fibre Optic
    1. Ethernet cables are used to connect devices to a LAN; are CAT 5e and 6, are twisted pair cables containing four pairs of copper wires twisted together to reduce internal interference
      1. Fibre Optic Cables- transmit data as light pulses, are high performance cables that don’t suffer interference and can transmit data over very large distances without loss of signal quality
3. Routers- responsible for transmitting data between networks; always connected to atleast two networks
  1. Wireless uses Radio Waves to transmit data
    1. To set up a wireless network you need a WAP (Wireless Access Point) device which is basically a switch that allows devices to connect wirelessly (devices with wireless capabilities) but if you don’t have a WAP you can use a USB dongle or HDMI dongles
Client Server
1. managed by a server
  1. Files and software stored centrally
    1. clients send requests to the server e.g. asking for data
      1. the server then processes the request and responds
        server stores user profiles, passwords and access information
        it may request a password before fulfilling certain requests or deny requests to users without the right access level
        web browsers are client-server relationships as websites fulfil requests (e.g. by sending web pages) for thousands or hundreds of thousands of clients
Peer-to-Peer
1. - in P2P networks all devices are equal in status, connecting directly to eachother without a sever
  1. - you store files on individual devices and share them with others
    1. you may use a P2P network at home to share files between devices, or connect devices to a printer
Topologies
1. Star Topology- all devices are connected to the centre; connected to the central switch or server that controls the network
  1. the central switch allows many devices to access the server simultaneously
2. Mesh Topology - all devices are connected to eachother.
  1. It is decentralised— networking devices are either directly or indirectly connected to every other one without the need for one central server or switch.
  2. mesh networks work by sending data along the fastest route from one device to another. if the central server or switch of a star topology fails then the whole network fails — in a mesh network, if one device fails then the data is sent along a different route to get to its target
Protocols
1. A protocol is a set of rules for how devices communicate and how data is transmitted across a network
  1. Protocols cover how communication between two devices should start and end, how the data should be organised, and what the devices should do if data goes missing
    1. Communication on the same network uses MAC addresses — MAC addresses are assigned to all network-enables devices by the manufacturer which are unique and cannoy be changed
      1. MAC Addresses are 48 or 64 bit binary numbers which are converted into hexadecimals
        MAC addresses are mainly used by the Ethernet protocol on LANs. LAN switches read the MAC address and use them to direct data to yhe right device
        Communication between different networks uses IP Addresses — IP addresses are used when sending data between TCP/IP networks e.g. over the Internet. IP addresses aren’t linked to hardware as they are assigned manually (static) or automatically (dynamic) before the device can access the network
        Static addresses are permanent which are used to connect to printers on a LAN and for hosting websites on the Internet
        Dynamic IP addresses are assigned to the device by a network server, meaning your device might have a different IP address every time you log on to the network.
        Inside a LAN (Ethernet), data is sent in frames and directed by switches using MAC addresses. Between networks (e.g. over the Internet), data is sent in packets and directed by routers using IP addresses
        Protocol Names: HTTP- Hyper Text Transfer — Used by web browsers to access websites and communicate with web servers. HTTPS- HTTP Secure — a more secure version of HTTP. encrypts all information sent and received. FTP- File Transfer Protocol — Used to access, edit and move files between devices on a network. POP3- Post Office Protocol (Version 3) — Used to retrieve emails from the server; server holds the email until you download it, at which point it is deleted from the server. IMAP- Internet Message Access Protocol— Used to retrieve emails; server holds information until you actually delete it- you only download a copy. SMTP- Simple Mail Transfer Protocol — Used to send emails; also used to transfer emails between servers
        TCP/IP is the most important protocol- the protocol which dictates how data is sent between networks which is made up of two protocols; TCP(Transmission Control Protocol) & IP(Internet Protocol). TCP-sets rules for how devices connect on the network, in charge of splitting data packets and reassembling the packets back into the original data once it reaches the receiving device. IP - responsible for packet switching.
Layers - Layer 1: Data Link Layer-passing data over the physical network(Ethernet) Layer 2: Network Layer- making connections between networks, directing data packets and handling traffic. used by routers(IP) Layer 3: Transport Layer — Controlling data flow; e.g. splitting data into packets and checking packets are correctly sent and delivered.(TCP) Layer 4- Application Layer — Turning data into websites and other applications and vice versa

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Networks - By Junior, Shabazz and Ferdinand

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	Created by Kavutse Manzi almost 5 years ago