1.4 Wired and Wireless Networks

1.4 Wired and Wireless Networks

1. LAN vs WAN

   • LAN- Local area network
     • Computers are connected together over a small geographical such as a single building or a single site
     • eg. Home network, school network, network in a shop
     • LAN has its own infrastructure of cabling and network hardware due to distance and practicalities.
   • WAN- Wide area network
     • Computers are connected over a large geographical area. this could be several buildings/sites, town wide, county wide or even country wide
     • The biggest WAN would be a global collection of network (known as The Internet)
     • WAN uses external hardware and external infrastructure eg. use of satellite, phone lines or The Internet.

2. CLIENT SERVER vs PEER-PEER

   • Client Server
     • The network relies on a central server.
     • All clients (devices) request services from the server (eg. print services / file services)
     • Additional hardware would be needed eg. high end powerful servers.
     • Workers can access files from any computer.
     • All computers can update central databases
     • All files can be stored centrally.
     • Back-ups are easily managed as they can be done centrally from the file server
       • All data is backed up in one go
       • Individual computers do not need to be backed up
     • Centralised security-antivirus and firewall can be installed and configured from a central locaton.
     • Useful for if there are lots of computers and it will be a high traffic environment
   • There are two ways of setting up a network to share data and services.
   • Peer-Peer
     • All computers have equal status.
     • Each device can act as a client and a server
     • All devices can request and provide network services.
     • Users have to log-in to the same computer every time.
     • All compters are responsible for backing up their own files
     • Individual security may need to be installed on individual machines
     • Appropriate for a small number of computers and a low traffic environment

3. PACKETS

   • Data transmitted over a network is broken down into packets
   • Each packet contains the address of the sender and the address of the receiver (IP addresses)
   • Packets will also contain a sequence number
   • Packets will have a time to live (how many hops around the network they can take before they disappear)

4. WAP- Wireless Access Point

   • Allows for wireless devices to connect to a network (LAN or WAN)
   • Includes connections through Wifi and Bluetooth
   • WAPs provide Internet access in public places (often known as Wi-Fi hotspots)

5. ROUTER

   • An interconnection device used on networks to connect two or more devices
   • Routers contain a routing table which has a list of IP addresses and common routes for packets to take
   • Routers examine packets IP addresses
   • The router will apply a subnet mask to identify a network and determine which network the packet should be forwarded to
   • If the packet is for this network- the router determines which host to send the packet to
   • Routers allow packets from different network types to be exchanged

6. SWITCH

   • If two or more computers place a packet onto a network at the same time- a data collision occurs.
   • A switch is an interconnection device that connects two or more devices together and helps in solving the issue of data collisions
   • As a data packet arrives at the switch- its destination address is examined and the switch creates a direct connection to that device
   • As far as the two devices are concerned there are no other computers on the network

7. NIC- Network Interface Card

   • A network interface card allows a computer to connect to a wired network
   • A NIC allows data packets to travel to and from a computer
   • A NIC contains a MAC address which is a physical hardware address
   • A NIC allows an Ethernet cable to be plugged into this

8. TRANSMISSION MEDIA

   • Ethernet (Car 5e / Cat6)
     • Known as twisted pair
     • A networking standard
   • Fibre optic
     • Very fast cable but also more expenxive (often used with WAN or larger LANs)
   • Coaxial Cable
     • An older networking standard

9. THE INTERNET

   • Worldwide collection of computer networks that are connected together (Inter-networking)
   • They operate on protocols such as TCP/IP

10. DNS SERVER

    • When accessing a webpage we use a URL to access the page e.g http://www.ocr.org.uk
      • http
        • tells the computer to use the hypertext transfer protocol which puts the packets together to be used in a web browser
      • www
        • tells us that this is a webpage and that it is located on the world wide web
      • ocr.org.uk
        • is the domain name
    • When you type that URL into the web browser the computer will query a DNS Server (Domain Name Server)
    • The DNS has a list of all domain names and their associated IP addresses
    • All packets are transmitted as IP addresses- therefore to access the server that holds the OCR website- we would need to know the IP address
    • Without a DNS server the user would have to type in IP addresses to access a webpage eg. 234.123.43.42

11. HOSTING

    • In order to let other people see your web site , it will be placed on a web server. This is known as hosting
    • You would select a suitable domain name eg, myInterestingNetworkSite.co.uk
    • You would need to register the domain name with a domain registrar- they would ensure that the domain name is unique and not already regiteres.
    • Each registered domain name would have an associated IP address- this would then be registered on a DNS

12. THE CLOUD

    • The cloud is a network of servers
      • Some servers will run applications
      • Some will store data
    • The benefits of the cloud is that you can...
      • incresase storage eg. from mobile phones
      • Access files from anywhere in the world
      • Collaborate with others from around the world

13. VIRTUAL NETWORKS

    • Within a LAN it is possible to break the network into virtual networks to allow one group of devices to not "see" another group of devices onto the network eg, administrators and school users
    • They share the same network hardware and cabling but software determines what the different virtual networks can access and see/use
    • Easier to maintain a network and also leads to a flexible network setup.
    • Machines can be added and removed from a virtual network without having to re-wire