1.3.1 Networks and topologies

What is a Stand alone device?

any computer or device that is not connected to any other computer or device via a network

What is a computer network?

two or more computers that are connected together to allow the sharing of resources and information

What are the two types of networks? Explain each one?

• LAN(Local Area Network) - computers connected over a small geographical area or a single site eg. home, school, small business, it has its own infrastructure of cabling and network hardware in each site

• WAN(Wide Area Network) - computers are connected over a large geopgraphical area, collection of LANs joined together eg. large multi-site businesses, The Internet, uses external infrastructure that is leased to people like satellites and phone lines

What does infrastructure mean?

The basic systems and services, such as transport and power supplies, that a country or organization uses in order to work effectively.

What are the advantages of networks?

• sharing resources eg. files, peripherals like printers/scanners

• centralised management eg. managed user profiles and security, software distribution, backup of files

• communication eg. email, instant messaging, file transfer

what are the disadvantages of networks?

• increased security risk

• servers and switches could fail

• factors can impact peformance of network

What factors affect the performance of a network?

• Number of users

• Bandwidth

• Latency

• Error rate

• Transmission

• Interference

• distance to travel/ signal strength

How does number of users affect performance of a network?

too many users on a network at the same time can cause the network to slow down if there is not enough bandwidth for all data being sent and received

What is bandwidth? How does it affect network performance?

The number of bits of data that can be transmitted at the same time measured in megabits per second (Mbps)

higher the bandwidth, the faster the data is transferred

What is latency? How does it affect network performance?

the delay between data being sent and received

if there is a big delay between te two, more data will be on the network causing collisions

What is error rate? How does it affect network performance?

measure of how many packets of data do not reach their destination

an increased error rate occurs in less reliable connections

What is transmission media? How does it affect network performance?

the type of media used to transmit data eg. wired/wireless

different media have different bandwidths such as wired connections offer higher bandwidth

What hardware is required to make a Local Area Network?

• router

• Wireless Access Point (WAP)

• Switch

• Network Interface Card(NIC)

• transmission media

What is a Network Interface Card(NIC)?

internal piece of hardware with a MAC address that allows a device to connect to a network either wired or wireless

What is a switch?

device that connects multiple wired devices together on a computer network with packet switching and uses MAC address to route data to correct destination avoiding data collisions

What is a router?

device that forwards data packets between computer networks using IP addresses to route traffic and connects LAN to WAN

What is a Wireless Access Point(WAP)?

device that allows wireless devices to connect to a wired network using Wi-Fi

What is an IP address?

unique address assigned to a device on a network

identifies location on a network

What is a MAC address?

unique identifier assigned to a device an cannot be changed

identifies device

What are the types of transmission media?

• Ethernet/ twisted pair

  • affordable

  • networking standard

  • low bandwidth

  • twisted to reduce interference

• coaxial

  • older networking standard

  • large and chunky

  • used in large scale networks and industry eg. satlelite TV, telephone networks

• Fire optic

  • high bandwidth

  • very expensive

  • durable

  • unaffected by interference

  • uses light to transmit data

  • fast transmission speeds

How can computers be connected over a network?

• In a client-server network

• In a peer-to-peer network

What is a client-server network?

• a powerful computer with a specialised role known as the server which provides services and resouces that is requested by the clients

What are the typical servers?

• file servers - hold and maintain user files

• applications servers - allow programs to be run over a network

• web servers - hold and share web pages

• print servers - manage printing across a network

• mail servers - handle emails between users

Advantages and Disadvantages of a client-server network?

Advantages

• central backing up for all computers

• central installing and updating of software

• Security controlled by central server

• scalable as it is easy to add clients

Disadvantages

• servers are a single point of failure

• expensive to set up and maintain

• requires specialists

• users lose access if server fails

What is a peer-to-peer server?

• computers connected together where all computers are equal and act as both client and servers

What are the advantages of peer-to-peer networks?

Advantages

• simple setup and maintainance

• clients are not dependent on single server

• cheap setup

Disadvantages

• no central device to manage security or backups

• each device must be individually backed up/updated

• performance decreases with more devices connected, especially if other devices are slow

• network can be less secure

What is the internet?

a world wide connection of computer networks

• refers to network infrastructure not content stored on it

• example of a WAN

• largely works on client server model

• purpose is to enable communication on an international level

What is the World Wide Web(WWW)?

all the web pages that are accessible via the internet

What is a node?

each connection point/device on a network

What is a topology?

layout/pattern/physical tructure in which nodes are connected in a network

Examples of topologies?

• star

• mesh

• bus

• ring

What is a star topology?

a topology with a central switch which all the other devices connect to

Advantages of a star topology? Disadvantages?

Advantages

• if one cable fails, other nodes are unaffected

• good performance as few data collisions

Disadvantages

• expensive to install

• if central switch/ server fails, whole network fails

What is a mesh topology?

a topology where all nodes are connected together

Advantages of a mesh topology? Disadvantages?

Advantages

• if one cable fails, nodes are unaffected as data can find another route

• more nodes makes faster wireless network

• best suited to wireless networks

• new nodes automatically added to wireless network

Disadvantages

• expensive to install

What is a partial mesh topology?

a mesh topology but where some nodes are notconnected