1.3 Networks, Connection & Protocols

• LAN


  Local Area Network - One which covers a small geographical area and whose equipment is owned by the organisation/individual.
• Node


  The name given to any device attached to a network
• Switch


  A device, which connects the computers in a local area network together that is considered intelligent, as it will route data to the correct destination.
• LAN characteristics


  - Covers a small geographical area located on a single site.

  - All the hardware for a LAN is owned by the organisation using it.

  - LANs are wired with UTP cable, fibre optic or wireless using Wi-Fi.
• Where are LAN's used?


  - A school network

  - An office network

  - A home network
• WAN characteristics


  -Covers a large geographical area, connecting LANs together.

  - Infrastructure between the LANs is leased from telecommunication companies who own and manage it.

  - WANs are connected with telephone lines, fibre optics cables or satellite links.
• What are the advantages of networking?


  - Users can share files

  - Users can share peripherals: printers and connections to other networks, e.g. The Internet.

  - Users can access their files from any computer on the network

  - Servers can control security, software updates and backup of data

  - Communication with other people, e.g. email and social networking.
• What are the disadvantages of networking?


  - Increased security risks to data

  - Malware and viruses spread very easily between computers

  - If a server fails, the computers connected to it may not work

  - The computer may run more slowly if there is a lot of data travelling on the network.
• What are network interface cards/controller?


  - Every computer connecting to a network will need one of these.

  - These days they are not physically separate cards, they are integrated.

  - These connect a device to wired or wireless controller

  - They use a protocol (a set of rules) to determine how the connection should work.

  - They allow a device to connect to either a wired or wireless network.
• Wireless Access Point (WAP)


  - Allows wireless enabled devices to connect to a network without cables

  - More convenient

  - Security is more of a concern with wireless connections

  - Connection is sometimes not as strong or reliable as wired connections

  - At home, your hub acts as your wireless access point
• Switch


  - Sends data between computers on a Local Area Network.

  - They segment the network by forwarding traffic to the correct location/device.

  - Switches learn which devices are connected and understand how to forward traffic in an intelligent way.
• Router


  - Sends data between networks.

  - It creates a WAN from a number of LANs.

  - You cannot connect to a WAN without using a router.

  - A router uses an IP address (Internet Protocol) to route traffic.
• Transmission Media: Copper cables (UTP)


  - Wired connections assure maximum bandwidth, security and reliability

  - With twisted pair cables the wires are twisted around each other to reduce interference

  - Normally a set of wires for transmission and receiving.

  - The grade of copper and insulating material affects the quality of the overall cable and therefore the bandwidth.
• Transmission Media: Fibre optic cables


  - Uses light to transmit data

  - Cover much longer distances and greater bandwidth than copper

  - The backbone of The Internet uses fibre optic cables
• Bandwidth


  The maximum rate of data transfer on a network
• Latency


  The time it takes for data to be transferred between one computer and its destination
• Error rate


  Number of errors encountered during transmission
• How does bandwidth effect performance of a network?


  - The amount of data that can be sent and received successfully in a given time across a network line

  - This is not a measure of how fast data travels, but how much data can be sent on the transmission media

  - Measured in bits per second

  - Often called the bit rate
• How does the number of users/devices effect the performance of a network?


  - Too many users or devices on the same network can cause the network to slow down if there is insufficient bandwidth for the data.
• How does transmission media effect the performance of a network?


  - Wired connections have a higher bandwidth than wireless connections

  - Fibre optic cables have a higher bandwidth than copper cables
• How does the error rate effect the performance of a network?


  - Less reliable connections increase the number of errors that occur when data is transferred

  - This means the data has to be resent until it arrives correctly

  - The signal quality of wireless connections is dependant on the range of devices from the wireless access point and other environmental factors

  - The signal quality of copper cables is determined by the grade of material used which reduces interference

  - The length of the cable is also a factor
• How does the latency effect the performance of a network?


  -The delay from transmitting data to receiving it

  - Latency is caused by bottlenecks in the infrastructure of the network

  - For example, by not using switches to appropriately segment traffic on a network

  - Hardware such as switches and transmission media may not operate at the same speed
• What is a client-server model?


  - A server is a special computer on a network not used as a workstation

  - Dedicated to storing files and managing other services on a network

  - A server controls access and security to one shared file storage system

  - Networks that use servers are called client-server networks
• What does a client-server model do?


  - A server manages access to The Internet

  - A server manages printing jobs

  - A server provides email services

  - A server runs a backup of data

  - A client makes requests to the server for data and connections
• What are the advantages of a client-server model?


  - Easier to manage security files

  - Easier to take backups of all shared data

  - Easier to install software updates to all computers
• What are the disadvantages of a client-server model?


  - Can be expensive to setup and maintain

  - Requires IT specialists to maintain

  - The server is a single point of failure

  - Users will lose access if the server fails
• What is a peer-to-peer model?


  - A peer is a computer on a network, and is equal to all other peers

  - Peers store their own files

  - Peers share their own files to each other

  - Each peer is responsible for its own security

  - Each peer is responsible for its own backup

  - Peers usually have their own printers

  - You can send print jobs to another peer to process, but that peer would need to be switched on to be able to communicate with the connected printer
• What are the advantages of a peer-to-peer model?


  - Very easy to maintain

  - Specialist staff are not required

  - No dependency on a single computer

  - Cheaper to set up

  - No expensive hardware required
• What are the disadvantages of a peer-to-peer model?


  - The network is less secure

  - Users will need to manage their own backups

  - Can be difficult to maintain a well ordered file store
• WAN


  Wide Area Network - A network that covers are large geographical area and whose equipment (phone lines / satellites) is usually owed by third party telecommunication companies often supply
• Cloud computing


  A term used to describe online services and applications
• URL


  Uniform Resource Locator - a fancy name for the web address of a website
• What is the internet?


  - Most well known Wide Area Network (WAN)

  
  

  - A collection of interconnected networks spanning the world

  
  

  - The internet is not the same as the "World Wide Web" which is just a service on The Internet. The internet is just the hardware
• The home router is connected to ....


  an Internet Service Provider (ISP) typically by telephone connection or fibre optic cable
• What is the backbone of the internet?


  Our Internet service provider is then connected to a Domain Name Server (DNS) which connected to Domain name servers
• What does an IP Address stand for?

  Internet Protocol Address
• What is the IP Address?


  - This is a unique number given to every computer on the internet - no two computers can have the same address

  
  

  - It acts like a postal address - Data and information is sent to your computer's IP Address

  
  

  - A computer has 2 addresses. A MAC address is hardwired by manufacturers into computers and this CANNOT change - this makes your computer unique. An IP address is given to a computer when they join a particular network.

  
  

  - IP addresses allow network managers to sort computers into areas
• What does URL stand for?

  Uniform Resource Locator
• What is a URL?


  A web address
• Hoe do web servers work?


  - We mainly use the internet to browse web pages on a web browser

  - Web servers carry out many functions, but by far their most common is:

  Hosting websites

  
  

  - The webpage, stored as text (HTML, CSS, JavaScript) is sent to a web browser which uses rules to render it correctly for the user.