2.1. Networks including the Internet

Question 1

Networking devices

Answer 1

Interconnected devices that allow a fast means of data transmission within the network.

Question 2

Networking benefits

Answer 2

• File sharing - you can easily share data between
  different interconnected devices
• Resource sharing - using network-connected output
  devices like printers, or can share the same software
  within the network
• Higher storage - can store files in network-connected
  storage mediums.

Question 3

LAN

Answer 3

• Network that connects
  devices within a small
  geographical area
• Only private ownership
• Transmission medium:
  twisted pair cable, coaxial
  cable or Wi-Fi
• Higher data transfer rate
• Lesser congestion

Question 4

WAN

Answer 4

• Network that connects
  devices within a larger
  geographical area
• Private or public ownership
• Transmission medium: PSTN
  or satellite link
• Lower data transfer rate
• Higher congestion

Question 5

Client-server Model

Answer 5

Server based network: dedicated server provides an
application (administration of users, security and
resources) for the client computer to utilize

Question 6

Client-server Applications

Answer 6

• Printer: manages print jobs from client computers
• File Sharing: the client accesses software and user’s
  data files stored on the server
  Proxy server
• Email server: for sending, receiving & storing emails
• Database server: manages DBMS
• Domain controller server
• Management of user accounts (IDs & passwords)
• Client sends login request to server which
  processes and grants request if user ID &
  password recognized

Question 7

Thin Clients

Answer 7

• A client that solely runs on
  the resources provided by
  the server and has no local
  storage
• Only provides input and
  receives output; processing
  done by server
• Smaller purchase cost:
  expensive, demanding
  hardware is not required
• Improved security: cannot
  run unauthorized, harmful
  software

Question 8

Thick Clients

Answer 8

• An independent client that
  does not require the server
  to run
• Thick client processes most
  of the application
• Can function even if no
  server is connected (works
  offline)
• No lag related to network
  problems

Question 9

Peer-to-peer network model (P2P)

Answer 9

• Decentralised network where each connected
  computer stores data and operates independently as
  a ‘peer’, and can act as both a client & server.
• Applications: Internet and Ad hoc networks

Question 10

Client-server

Answer 10

• Centralized backup
• Files & resources centralized
  in server: prevents illegal
  resource usage
• Improved security: files are
  stored on central server
  which would be regularly
  scanned for malware

Question 11

Peer-to-peer

Answer 11

• Lesser initial setup cost
• Lesser network traffic: each
  peer can simultaneously
  receive data from different
  sources
• Can work even if a device
  goes down, but Client-server
  model can’t work if server
  goes down

Question 12

Network Topologies

Answer 12

• Bus
• Star
• Mesh
• Hybrid

Question 13

Bus

Answer 13

• Single line (bus) connecting all devices with
  terminators at each end.
• Other computers can read the data being sent
  from one to another computer.
• Unsuitable for heavy traffic since collisions occur.

Question 14

Star

Answer 14

• Consists of a central server (‘Switch’) and all other
  computers connected with a dedicated connection
  to each, hence server can send packets to
  different devices simultaneously and bidirectionally.
• No collisions possible.

Question 15

Mesh

Answer 15

• Network setup where every device (node) is
  directly interconnected to the each of the other
  devices (nodes)
• It is commonly used for wireless networks (such as
  the Internet), via the mesh connection of routers

Question 16

Hybrid

Answer 16

• Combination of two or more topologies.
• E.g. when there is a connection between 2 or
  more LANs of different topologies

Question 17

Wired Networks

Answer 17

Use (copper (twisted-pair cable or
coaxial cable) or fibre-optic) cables connected to an
Ethernet port on the network router

Question 18

Copper Cable

Answer 18

Benefits:
Less expensive and
easier to
install FlexibleEasier to
make terminations

Drawbacks:
Doesn’t perform well
with small
charges. Affected by
electromagnetism

Question 19

Fiber-Optic
Cables

Answer 19

Benefits:
Greater
bandwidthImproved
security Lightweight:
easy to installLess
signal boosting
required; used in long
distance comm.

Drawbacks:
Needs expensive
optical transmitters
and receivers.

Question 20

Wireless Networks

Answer 20

Use radio waves (including WiFi),
microwaves, satellites to connect devices to networks
without cables.

Answer 21

Benefits:

Drawbacks:

Question 22

Radio
waves

Answer 22

Benefits:
Can travel over large
distances since they
have largest range of
wavelengthRelatively
inexpensive.Used for TV
signals & mobile phone
comms.

Drawbacks:
Low frequency so
transmits less data at
one time.Affected by
radio stations with
similar frequency

Question 23

Microwaves

Answer 23

Benefits:
Larger bandwidth, can
transfer more data at a
time

Drawbacks:
Emitting towers
expensive to
build Physical obstacles
can interfere

Question 24

Satellites

Answer 24

Benefits:
Cheap with long
distanceUsed for
Satellite phones,
satellite radio broadcast

Drawbacks:
Easy to
interfere
Expensive set
up

Question 25

Ethernet

Answer 25

• Most common wired medium of transmission, that
  can be used to transfer data between LANs or WANs
• Usually used in bus topology; since all data travelled
  on a single wire there is a possibility of data
  corruption by the “collision” of signals
• This collision is prevented by the CSMA/CD (Carrier
  Sense Multiple Access Collision Detection) method:
  Before transmitting, device checks if channel is
  busy
• If busy, device calculates a random wait time and
  waits that time, after which it begins transmission
• Then during transmission, the device listens for
  other devices also beginning transmission
• If collision, transmission is aborted and both
  devices wait different random times, then tried
  again

Question 26

Bit Streaming

Answer 26

• Sequence of digital signals (bits) transferred over a
  communication path at high speeds
• Requires a fast broadband connection and some form
  of buffers (short-term memory)
• Bits arrive in the same order they are sent
• Bit rate: number of bits transmitted per second

Question 27

Real-time bit streaming

Answer 27

• Event captured live via video
  camera that is connected to a
  computer
• Video signal converted to an
  encoded streaming video
  signal
• Encoded video signal
  uploaded from computer to a
  dedicated streaming server
  via cables or high-speed
  wireless internet connection
• Server then sends live images
  to all users requesting it as a
  real-time video
• Cannot be paused, fastforwarded, etc.

Question 28

On-demand bit streaming

Answer 28

• Existing digital files converted
  to encoded bit-streaming
  format for broadcasting on
  the internet by uploading to a
  dedicated server
• A link for encoded video is
  placed on website and the
  user clicks on link to view
  encoded streaming video
• The data is streamed to a
  buffer in user’s computer and
  the buffer stops the video
  from being paused as the bits
  are streamed
• As the buffer is emptied, it’s
  filled again thus providing
  continuous viewing
• Can be paused, fastforwarded, etc.