Communications technology

• File server 


  Stores and manages data files. This saves the need for extensive storage

  space on client computers. They allow a user to use any client computer in

  the network and still be able to access their files and also any publicly

  shared files available. They also allow a central backup of all data to be

  made.
• Web server


  Stores, processes and transmits web pages.
• Mail Server


  Sends and receives emails. It stores incoming emails for the user that can

  be downloaded when requested. It forwards outgoing messages to the

  correct destination. Most mail servers have security checking software

  that will scan emails for issues such as known viruses and malware. They

  can also be set to check for inappropriate content and spam.
• Application server


  Installs and runs software applications. They provide a platform to run

  both desktop and web applications.
• Print server


  Receives print jobs from client computers and sends them to the correct

  printer. This allows many client computers in a network to use the range

  of printers available. They can be set to print to a specific printer. They

  can also be set to find the next available printer or the closest printer to

  the client. If many jobs are sent to the print server at a time, it will queue

  the jobs until it can deliver them to a printer.
• Network


  Two or more computers or devices connected together so they can communicate and share data and resources
• Local Area Network (LAN)


  • A network that is limited to a small geographic area, such as a single building, a campus or a group of closely located buildings
  • Has high data transfer speeds of up to 1 GB per second
  • Data transmission errors are fewer because data is transferred over a short distance
  • Normally connected using copper wire, fibre optics cables or radio waves
  • Can be kept more secure as a smaller number of devices need securing
  • There is usually private ownership as they are often owned, setup and maintained by a single organization or individual
• Wide Area Network (WAN)

  • A type of computer network that spans a large geographical area, connecting multiple LANs and other network devices
  • It can be within a country or can spread across several countries
  • Internet is the largest WAN
  • It is often restricted to lower transfer speeds normally less than 200 mb
  • It has greater chance of errors occurring as data is transferred over longer distance
  • Connections could include physical connections such as copper wire,etc and others like radio waves, microwaves, transmission towers and satellites
  • It is more susceptible to security issues as a large number of devices need securing
  • Elements of the network are often owned by a third party, so they have to rely on the control and maintenance of others
• Client-Server network


  • A network that contains two types of computers, a client and a server
  • The server(s) in a client-server network are a central point of control and provide a dedicated function for the network
  • All other computers in the network are all connected to the server to allow it to perform its dedicated function
  • Most client server networks operate using a request response method
• Server Types


  • File Server
  • Web Server
  • Mail Server
  • Application Server
  • Print Server
  • FTP Server
  • Proxy Server
  • Virtual Server
• File Server


  Stores and manages data files. This saves the need for extensive storage space on client computers. They allow a user to use any client computer in the network and still be able to access their files and also any publicly shared files available. They also allow a central backup of all data to be made.
• Web Server


  Stores, processes and transmits web pages.
• Mail Server


  Sends and receives emails. It stores incoming emails for the user that can be downloaded when requested. It forwards outgoing messages to the correct destination. Most mail servers have security checking software that will scan emails for issues such as known viruses and malware. They can also be set to check for inappropriate content and spam.
• Application Server


  Installs and runs software applications. They provide a platform to run both desktop and web applications.
• Print Server


  Receives print jobs from client computers and sends them to the correct printer. This allows many client computers in a network to use the range of printers available. They can be set to print to a specific printer. They can also be set to find the next available printer or the closest printer to the client. If many jobs are sent to the print server at a time, it will queue the jobs until it can deliver them to a printer.
• FTP Server


  Manages the transfer of data that uses the file transfer protocol (FTP). It keeps a log of all activity involving FTP. Uses a lot in the transfer of files over the internet.
• Proxy Server


  Acts as an intermediary between clients and other servers by receiving client requests and forwarding them on to the relevant server. It provides an added level of security in a network, protecting clients directly accessing resources on another server. For this reason, it can also be set to act as a firewall.
• Virtual Server


  Shares the hardware of another server. Created using virtualization software on another server. Multiple virtual servers could be created on one physical server. A virtual server can be given the capabilities of any of the above physical servers. Businesses sometimes use third party virtual servers that will act as a web server, for the business to host its website. This allows the hosting company the ability to host several businesses websites on the hardware of a single physical server.
• Peer-to-Peer network


  • A decentralized network where each computer in it known as peers has equal status
  • Each computer shares its data and resources directly with each other without the need of a server
  • Similarly each peer stores its data on its own computer but may allow access to it to other peers or chose to keep it private
  • Each computer operates independently and there is no central dependency
  • It's easier to join/add more peers or remove them
  • Peers with varying processing powers can join and work on a collaborative task
• BitTorrent


  • A communication protocol often used in peer to peer file sharing
  • In it peers/nodes share the workload without the need for a central server
  • They work as both client and server for other nodes/peers
  • Several sources known as hosts are collated to create a swarm
  • Each host will be given pieces of the file
  • The BitTorrent protocol allows users to join the swarm and download the file from the available hosts
  • For it a peer to peer/ Bit torrent client software is run on computer
  • The protocol downloads the file in pieces, simultaneously from various hosts in the swarm
  • The protocol can then rearrange the pieces to create a completed file
  • Each piece of the file is protected to stop it from being modified by any users
  • Each user trying to download the file is called a peer and each user providing the upload of the file is called is called a seed
  • Tracker keeps record of all the peers and the parts of the file they have and can pause and restart at any time
  • Used to stream videos and transfer large files using minimum bandwidth
  • Used by social media to distribute updates to servers
• Virtual Private Network (VPN)

  • A secure technology that encrypts internet connections, providing privacy, anonymity and secure access to remote networks
  • It enables users to browse privately, access geographically restricted content and connect securely to corporate networks from anywhere
• How a VPN works

  1. Open VPN Server creates a VPN

  2. Software encrypts your data

  3. Sends it to VPN server

  4. VPN server forwards it to destination

  5. Same happens in reverse
• Internet Protocol Security (IPSec)


  • Network protocol that is designed to encrypt and authenticate data packets that are sent across the internet
  • Encryption of keys at start of session/digital certificates are used for authentication/pre-shared keys (to be used) are negotiated/established at start of session
  • All data (that is exchanged) during session is encrypted for different sessions
  • Can support (both) pre-shared key/private and public key encryption of data so that the data is not understandable without the keys
  • Works at Internet layer of protocol suites/stacks so encryption is at device level/supports VPNS
• Tunneling


  • Data is broken into (small) packets/datagrams for transfer over IP network
  • (IP) packets are encapsulated by Tunneling Protocol/L2TP inside (public) IP packets and sent out over public communication channels (to internet)
  • Data is/may be encrypted using a secure shell (SSH)/IPSec protocol
  • Packets are decapsulated and unencrypted at destination
• Mobile Network


  • A wireless WAN that uses radio waves to transmit and receive communications from portable devices such as smartphones
  • Mobile networks are broken down into small areas called cells which is the geographical area covered by a radio transmitter
  • At the heart of each cell is a radio base station that transmits and receives messages
  • The base stations connection to public telecommunication services allowing access to the internet
  • There have been several generations of mobile networks each providing faster access speeds and greater reliability (1G, 2G, 3G, 4G, 5G)
• 1G


  First generation of mobile networks uses analogue signals. It's also largely limited to voice and text message communications
• 2G


  Second generation which uses digital transmission, improving signal quality. It is able to connect with each other, allowing a phone to use other networks.
• 3G


  It increased data transmission speeds up to 2 Mbps, allowing mobile internet access, video transmission and online gaming.
• 4G


  Allows data transmission speeds of up to 1Gbps, allowing greater use of high quality video streaming facilities and advanced mobile services and online gaming.
• 5G


  Latest generation offering the fastest and most reliable connections available. It supports technologies like augmented reality, virtual reality and the internet of things (IoT). They have tested speeds up to 1.5 Gbps at present but could be even faster. Very large capacity for connection of devices/up to a million devices per km2. Very high bandwidth for transferring data between multiple devices. Very low latency in the connections for fast/instant responses. Seamless handover between base stations. Use of 'beam-forming' techniques (by base stations) to direct signal/improve connections to (specific) devices.
• Wireless / Network Interface Cards (WNIC and NIC)


  • NIC assumes a vital role in the network communication by serving as an essential link between a device and the network infrastructure
  • Operating at the Data Link Layer, the NIC encapsulates data into frames, assigning source and destination MAC addresses for proper addressing within the local network
  • With a unique MAC address, the NIC enables the device to be identified and communicated with on the network
• Cellular networks


  • Larger geographical areas can be covered than by using a single transmitter
  • Even high power transmitters are limited in range
  • By using several low power transmitters, a wider area can be covered
• Network Interface Cards (NIC)


  • Serves as an essential link between a device and the network infrastructure
  • Operates at the Data Link Layer
  • Encapsulates data into frames, assigning source and destination MAC addresses for proper addressing within the local network
  • Establishes physical connectivity, whether through wired (Ethernet cable) or wireless (wifi) means
  • Prepares data for transmission, converts it into frames, and transmits them onto the network
  • Monitors the network for incoming frames, processes them and delivers the data to the devices operating system
  • Requires driver software to communicate with the operating system, ensuring proper configuration
  • Collaborates with switches, routers and firewalls, to contribute to efficient, secure and seamless communication within the network infrastructure
• Wireless Network Interface Cards (WNIC)

  • Provides the same function as a NIC by using radio waves to transmit and receive data
  • Works along a WAP (wireless access point)
• Repeaters


  • Serve as a signal booster in a network, extending the reach and coverage of the network by amplifying and retransmitting signals
  • Operate at the physical layer of the OSI model
  • Receive incoming signals, amplify them to compensate any signal degradation over distances and regenerate the signals to remove any noise and retransmit them back into the network
  • In wireless networks, wireless repeaters are utilized to amplify and retransmit wifi signals, particularly in areas with no or weak signal coverage
  • May introduce latency (delay)
• Hubs


  • Used to connect a device to the network if there are multiple as they can't be connected via Ethernet connection
  • If a data needs to be send to a device in the network, it will be first be sent to the hub which will forward the data to all connected devices
  • Operate at the physical layer (layer 1) of the OSI model
  • Can be passive or active, a passive hub just sends data to all devices while an active hub will amplify and regenerate the signal used to send the data in order to make it stronger
• Switches


  • Similar to hub as it connects multiple devices to a network and helps communicate data between a network
  • Operate at the data link layer (layer 2) of the OSI model
  • Examine each data packet it receives and forwards it to the intended devices only
  • Use a MAC address source table of the connected devices
  • Look at the mac address of the intended destination of the packet and compare it against it stored mac address table
  • Send frames to the known addresses where its intended while all unrecognized data is sent to all addresses
  • Reduces the possibility of data collision and increases network performance than a hub
• Wireless Access Points (WAP)

  • Allow a wireless device to connect to a wired network within a designated coverage area
  • Receive wireless data signals and then use the wired network to transmit them to their destination often via a switch
  • Devices with wnic can connect to a network via WAP's SSID (service set identifier)
  • Support the connection of multiple devices to the same WAP, allowing them to connect to a network and effectively creating a wireless LAN
  • The connectable devices often have a limit
  • Extend the network so that computers don't need to be in a fixed place
  • The signals deteriorate with distance hence for large establishments multiple WAPs are used that may centrally managed by a wireless controller for coordinated performance
• Gateways


  • A device or software that allows two or more different networks to connect to each other, enabling communication and data transfer
  • Router is a common gateway that connects two or more similar network
  • Important in network connection as different network have different protocols and enables communication between them
• Bridges


  • Network component that joins different LANs together
  • Responsible for segmenting and managing network traffic efficiently
  • Divide a larger network into smaller segments, creating separate collision domains to minimize the chance of data collisions
  • Operate at data link layer (layer 2) of the OSI model, filtering and forwarding traffic based on MAC addresses
  • Maintain a MAC address table, containing the addresses of the connected devices of each network segment
  • Examine data packets as it receives and checks them against the MAC address source table, if they are intended for another network segment, it forwards it to that part of the LAN acting as a bridge
  • If it happens to be in the same segment, then it simply ignores it and lets it travel to its destination like the switch