Communication Networks, including the Internet(Znote)
Aaron
Networking devices
Interconnected devices that enable fast data transmission within a
network.
Networking benefits
File sharing: Easily share data between different
interconnected devices.
Resource sharing: Use network-connected output
devices like printers or share software within the network.
Higher storage: Files can be stored in
network-connected storage mediums.
LAN
WAN
A network that connects devices within a small geographical area,
often within the same building.
A network that connects devices within a larger geographical area,
such as a city, country, or globally.
Only private ownership.
Private or public ownership.
Transmission medium: Twisted Pair Cables, Coaxial Cables or
Wi-Fi.
Transmission medium: PSTN or Satlink.
Higher data transfer rate.
Lower data transfer rate.
Less congestion.
Higher congestion.
Client-Server Model
Server-based network: A dedicated server provides
applications (administration of users, security, and resources) for the
client computer to utilize.
Client-server Applications
Printer: Manages print jobs from client
computers.
File Sharing: Clients access software and user data
files stored on the server.
Proxy server.
Email server: For sending, receiving, and storing
emails.
Database server: Manages DBMS.
Domain controller server:
Manages user accounts (IDs & passwords).
The client sends a login request to the server, which processes and
grants the request if the user ID & password are recognized.
Thin Clients vs. Thick
Clients
Thin Clients
Thick Clients
A client that solely runs on the resources provided by the server
and has no local storage.
An independent client that does not require the server to run.
Only provides input and receives output; processing is done by the
server.
Thick client processes most of the application locally.
Smaller purchase cost: expensive, demanding hardware is not
required.
Can function even if no server is connected (works offline).
Improved security: Cannot run unauthorized, harmful software.
No lag related to network problems.
Peer-to-Peer network model
(P2P)
Definition: A decentralized network where each
connected computer stores data and operates independently as a ‘peer’,
acting as both a client and a server.
Applications: Internet and Ad hoc networks.
Client-Server vs.
Peer-to-Peer models
Client-Server
Peer-to-Peer
Centralized backup.
Lesser initial setup cost.
Files & resources centralized in server: Prevents illegal
resource usage.
Lesser network traffic: Each peer can simultaneously receive data
from different sources.
Improved security: Files are stored on a central server, which would
be regularly scanned for malware.
It can work even if a device goes down, but the client-server model
can’t work if the server goes down.
Network Topologies
Bus
A single line (bus) connects all devices with terminators at each
end.
Other computers can read data being sent between any two
computers.
Unsuitable for heavy traffic due to frequent collisions.
Star
Consists of a central server (switch) with all other computers
connected via dedicated connections.
The server can send packets to different devices simultaneously and
bidirectionally.
No collisions are possible.
Mesh
Every device (node) is directly interconnected with each of the
other devices (nodes).
Commonly used for wireless networks, such as the Internet, through
the mesh connection of routers.
Hybrid
A combination of two or more topologies.
Example: A connection between two or more LANs of different
topologies.
Wired Networks
Copper cables (twisted-pair cable or coaxial cable)
or fiber-optic cables.
Cables are connected to an Ethernet port on the network router.
Benefits and Drawbacks
Copper Cable
Fiber-Optic Cables
Less expensive and easier to install. Flexible. Easier to make
terminations.
Greater bandwidth, improved security, lightweight, easy to install,
and less signal boosting required; used in long-distance
communications.
Doesn’t perform well with small charges. Affected by
electromagnetism.
Needs expensive optical transmitters and receivers.
Wireless Networks
Use radio waves (including WiFi), microwaves, and satellites to
connect devices to networks without cables.
Benefits and Drawbacks 1
Radio Waves
Microwaves
Satellites
Can travel over large distances with a wide range of wavelengths.
Relatively inexpensive. Used for TV signals and mobile phone
communications.
Larger bandwidth allows more data transfer.
Cost-effective for long-distance communication, used in satellite
phones and radio broadcasts.
Low frequency means less data can be transmitted at one time.
Affected by interference from radio stations with similar
frequencies.
Expensive to build emitting towers. Physical obstacles can interfere
with signals.
Susceptible to interference. Expensive setup.
Ethernet
The most common wired medium for data transmission in LANs or
WANs.
Typically used in bus topology; data collisions are managed by the
CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
method.
CSMA/CD Process
Device checks if the channel is busy before transmitting.
If busy, the device waits a random time before retrying.
During transmission, the device listens for other
transmissions.
If a collision occurs, transmission is aborted, and both devices
wait random times before retrying.
Bit Streaming
Sequence of digital signals (bits) transferred over a communication
path at high speeds, requiring a fast broadband connection and
buffers.
Bit Streaming Types
Real-time: Live events captured and transmitted
directly.
On-demand: Pre-existing files are converted and
streamed as requested.
Importance of High
Broadband Speed/Bit-Rate
The user has to download and display bits at the same time.
Higher quality media requires faster speeds due to larger data
frames.
Real-time streaming needs higher speeds due to simultaneous data
requests coming from multiple different users.
Real-time
On-demand
The event is captured live via a video camera that is connected to a
computer.
Existing digital files are converted to encoded bit-streaming format
for broadcasting on the internet by uploading to a dedicated
server.
Video signal converted to an encoded streaming video signal.
A link for encoded video is placed on the website, and the user
clicks on the link to view encoded streaming video.
Encoded video signal uploaded from computer to a dedicated streaming
server via cables or high-speed wireless internet connection.
The data is streamed to a buffer in the user’s computer, and the
buffer stops the video from being paused as the bits are streamed.
The server then sends live images to all users requesting them as a
real-time video.
As the buffer is emptied, it’s filled again, thus providing
continuous viewing.
It cannot be paused, fast-forwarded, etc.
Can be paused, fast-forwarded, etc.
Cloud Computing
On-demand provision of computing services over the internet,
including infrastructure, and platforms.
Public cloud vs. Private
cloud
Public cloud
Private Cloud
Access provided by third-party service providers, shared among
multiple users.
Owned and maintained by a single organization, providing exclusive
access.
Managed by cloud service providers using large server farms.
Can be managed internally by the organization itself, or
outsourced.
Benefits and Drawbacks 2
Benefits
Drawback
Less technical knowledge required, easy to implement.
Cannot access the resources/data stored on the cloud if there are
bandwidth issues.
Flexibility to scale with organization’s growth mindset.
Poor data privacy, since there may be data leakage in the
multi-tenant architecture (public clouds).
World Wide Web (WWW)
Description: Collection of web pages stored on
websites.
Function: Protocols are used to transmit data
across the WWW.
Internet (Interconnected
Network)
Description: Massive, open network of
networks.
Protocol: Uses TCP/IP protocol, which uses IP
addresses to identify devices connected to the internet.
Access: Provided by Internet Service Provider.
Communication Methods: Wired, radio, and
satellite.
Router in a Network
Function: Connects two networks together which
operate under the same protocols (for example, IP).
Connections: Allows internal connections between
LANs or external connection from the main LAN to a WAN.
Additional Roles: Acts as a gateway and
firewall.
Setup: Usually attached to a server or switch in a
LAN.
IP Address Translation: Translates private IP
addresses to public IP addresses and vice versa.
LAN-Supporting Hardware
Switch
Connected to all devices in a LAN.
Can simultaneously broadcast information to all devices.
Server
Device/software that provides specific functions for computers in
the network.
Network Interface Card (NIC)
Provides each device (end-system) in the wired LAN with a unique MAC
address to uniquely identify it on the network.
Allows each device to connect to the## Static vs. Dynamic IP
addresses
Static
Dynamic
IP address never changes.
The IP address will change at regular periods.
Static IP addresses are valid when websites need to remember a
device for a long time, e.g VPNs whitelisting.
Dynamic IP address is relatively more secure, hence used where data
privacy is quite important.
Faster upload/download speeds.
Maintaining the cost of the dynamic IP address is lesser.
URL (Uniform Resource
Locator)
Unique reference address for the exact location of an internet
resource on the WWW.
Components
Protocol: Enables the browser to know what protocol
is used to access information in the domain.
Host-name: The domain name.
Location of Server: The path indicating the server
location.
Domain Name Service (DNS)
Definition: A naming system used for computers or
resources having an internet connection.
Structure: Consists of a hierarchy of DNS servers
which have a URL database and their corresponding IP addresses.
