2.1. Networks including the Internet Flashcards
Networking devices
Interconnected devices that allow a fast means of data transmission within the network.
Networking benefits
- 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.
LAN
- 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
WAN
- 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
Client-server Model
Server based network: dedicated server provides an
application (administration of users, security and
resources) for the client computer to utilize
Client-server Applications
- 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
Thin Clients
- 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
Thick Clients
- 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
Peer-to-peer network model (P2P)
- 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
Client-server
- 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
Peer-to-peer
- 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
Network Topologies
- Bus
- Star
- Mesh
- Hybrid
Bus
- 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.
Star
- 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.
Mesh
- 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
Hybrid
- Combination of two or more topologies.
- E.g. when there is a connection between 2 or
more LANs of different topologies
Wired Networks
Use (copper (twisted-pair cable or
coaxial cable) or fibre-optic) cables connected to an
Ethernet port on the network router
Copper Cable
Benefits:
Less expensive and
easier to
install FlexibleEasier to
make terminations
Drawbacks:
Doesn’t perform well
with small
charges. Affected by
electromagnetism
Fiber-Optic
Cables
Benefits:
Greater
bandwidthImproved
security Lightweight:
easy to installLess
signal boosting
required; used in long
distance comm.
Drawbacks:
Needs expensive
optical transmitters
and receivers.
Wireless Networks
Use radio waves (including WiFi),
microwaves, satellites to connect devices to networks
without cables.
Benefits:
Drawbacks:
Radio
waves
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
Microwaves
Benefits:
Larger bandwidth, can
transfer more data at a
time
Drawbacks:
Emitting towers
expensive to
build Physical obstacles
can interfere
Satellites
Benefits:
Cheap with long
distanceUsed for
Satellite phones,
satellite radio broadcast
Drawbacks:
Easy to
interfere
Expensive set
up
Ethernet
- 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
Bit Streaming
- 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
Real-time bit streaming
- 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.
On-demand bit streaming
- 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.
