Data Communication Basics

Data Communication

• Data communication is the transmission of digital or analog data between two or more devices.
• It enables the exchange of information, allowing computers, smartphones, servers, and other electronic devices to communicate with each other over networks.

Components of Data Transmission

• Analog signals: represent continuous waves
• Digital signals: comprise discrete bits (0s and 1s)
• Modulation: encoding digital data onto an analog signal for transmission
• Demodulation: reversing the modulation process to retrieve the original data

Transmission Media

• Guided media: physical pathways for signals, such as:
  • Twisted pair cables
  • Coaxial cables
  • Optical fibers
• Unguided media: wireless transmission mediums, such as:
  • Radio waves
  • Microwaves
  • Infrared signals

Networking Devices

• Routers: direct data packets between networks
• Switches: connect multiple devices within a local network
• Hubs: basic networking devices that broadcast data to all connected devices

Communication Protocols

• Rules and conventions governing the format and timing of data exchange between devices
• Examples:
  • TCP/IP (Transmission Control Protocol/Internet Protocol) for internet communication
  • OSI Model (Open Systems Interconnection) for standardizing the functions of a telecommunication or computing system

Data Transmission Modes

• Simplex: one-way communication (e.g., television broadcast)
• Half-Duplex: two-way communication, but only one device can transmit at a time (e.g., walkie-talkies)
• Full-Duplex: simultaneous two-way communication (e.g., telephone conversation)

Error Detection and Correction

• Methods to detect errors in transmitted data:
  • Parity Check
  • CRC (Cyclic Redundancy Check)
  • Checksum
• Protocols that request retransmission of data in case of errors:
  • ARQ (Automatic Repeat request)

Multiplexing

• Techniques to combine multiple signals into a single transmission medium:
  • Time-Division Multiplexing (TDM)
  • Frequency-Division Multiplexing (FDM)

Networks

• A collection of interconnected devices, such as computers, servers, routers, and switches that can exchange data with each other
• Networks can be categorized based on their geographic scope and the technologies they employ

Types of Networks

• LAN (Local Area Network): covers a limited geographical area, such as a single building or a campus
• WAN (Wide Area Network): spans a larger geographical area, often connecting multiple LANs across cities or countries
• MAN (Metropolitan Area Network): intermediate in size between LANs and WANs, typically covering a city or a large campus
• PAN (Personal Area Network): involves the connection of devices within an individual's personal space
• VLAN (Virtual Local Area Network): a logical subdivision of a LAN that allows for better organization and management of network traffic

Networking Devices

• Router: connects different networks and directs data packets between them
• Switch: connects devices within a local network
• Hub: basic networking device that broadcasts data to all connected devices
• Gateway: connects networks with different communication protocols
• Firewall: protects a network by monitoring and controlling incoming and outgoing network traffic

Network Topologies

• Bus Topology: all devices share a single communication line
• Star Topology: devices are connected to a central hub or switch
• Ring Topology: devices are connected in a circular fashion
• Mesh Topology: every device is connected to every other device
• Hybrid Topology: combines elements of different topologies to suit specific needs

Internet

• A global network of interconnected computers and devices that communicate using standardized protocols
• Enables the exchange of information, resources, and services across the globe

Internet Infrastructure

• Physical components: fiber optic cables, satellite links, and network routers
• Protocols and standards: TCP/IP, DNS, and HTTP

Accessing the Internet

• Methods to access the internet:
  • Broadband internet: DSL, cable, fiber-optic, and wireless
  • Mobile data networks: 3G, 4G/LTE, and 5G
  • Satellite internet: via satellite signals
  • Dial-up internet: using dial-up modems

Internet Standards

• Organizations involved in developing and maintaining internet standards:
  • IETF (Internet Engineering Task Force)
  • W3C (World Wide Web Consortium)
  • ICANN (Internet Corporation for Assigned Names and Numbers)
  • IANA (Internet Assigned Numbers Authority)

Internet Administration

• Organizations involved in coordinating and overseeing the internet's infrastructure:
  • ICANN (Internet Corporation for Assigned Names and Numbers)
  • IANA (Internet Assigned Numbers Authority)
  • RIRs (Regional Internet Registries)
  • ISPs (Internet Service Providers)

TCP/IP Model

• A suite of protocols that governs the communication and networking on the Internet
• Consists of four conceptual layers:
  • Link Layer (or Network Interface Layer)
  • Internet Layer
  • Transport Layer
  • Application Layer

OSI Model

• A conceptual framework that standardizes the functions of a telecommunication or computing system into seven abstraction layers
• Layers:
  • Physical Layer (Layer 1)
  • Data Link Layer (Layer 2)
  • Network Layer (Layer 3)
  • Transport Layer (Layer 4)
  • Session Layer (Layer 5)
  • Presentation Layer (Layer 6)
  • Application Layer (Layer 7)### OSI Model and Encapsulation
• Each layer adds its own header (and sometimes a trailer) to the data it receives from the layer above, known as encapsulation.
• De-encapsulation occurs when data moves down the layers on the receiving side, and each layer removes its corresponding header.

Protocols

• Various communication protocols operate at different layers of the OSI model.
• Examples: Ethernet operates at the data link layer, while IP operates at the network layer.

Transmission Media

• Transmission media, also known as communication channels, are the physical pathways that carry signals between devices in a communication system.
• Classified into two main categories: guided media and unguided media.

Guided Media

• Use physical paths or wires for the transmission of signals.
• Examples: Twisted Pair Cable, Coaxial Cable, and Fiber-Optic Cable.

Twisted Pair Cable

• Consists of pairs of insulated copper wires twisted together.
• Commonly used for telephone lines and local area network (LAN) connections.
• Twisting helps reduce electromagnetic interference.

Coaxial Cable

• Has a central conductor surrounded by an insulating layer, a metallic shield, and an outer insulating layer.
• Used for cable television (CATV), broadband internet, and some LANs.
• Offers better shielding and higher bandwidth compared to twisted pair cables.

Fiber-Optic Cable

• Uses strands of glass or plastic fibers to transmit signals using light.
• Provides high bandwidth, low signal attenuation, and resistance to electromagnetic interference.
• Commonly used in long-distance communication, high-speed internet, and telecommunications networks.

Unguided Media

• Also referred to as wireless or unbounded media.
• Do not have a physical path for signal transmission.
• Examples: Wireless Transmission, Satellite Communication, Infrared Communication, Microwave Communication, and Radio Communication.

Wireless Transmission

• Involves the transmission of signals without the use of physical cables.
• Common wireless technologies include Wi-Fi (802.11), Bluetooth, and cellular networks (3G, 4G, and 5G).

Satellite Communication

• Uses communication satellites in Earth's orbit to relay signals between ground stations.
• Suitable for long-distance communication, television broadcasting, and global positioning systems (GPS).

Infrared Communication

• Utilizes infrared signals for short-range communication between devices.
• Commonly found in remote controls, short-range data transfer, and some wireless connectivity solutions.

Microwave Communication

• Involves the use of microwave frequencies for communication.
• Used in point-to-point communication links, such as microwave towers for long-distance communication.

Radio Communication

• Uses radio frequencies for wireless communication.
• Includes radio broadcasting, walkie-talkies, and various radio-based technologies.

Switching

• The process of directing data from one device to another within a network.
• Involves the selection of a specific communication path or route to enable the exchange of information between devices efficiently.

Circuit Switching

• A dedicated communication path or circuit is established between two devices for the duration of their conversation.
• Analogous to traditional telephone networks where a physical connection is established for the entire duration of a call.
• Provides a continuous and dedicated connection, suitable for real-time applications.

Packet Switching

• Data is divided into packets, each of which is sent independently to its destination.
• The packets may take different routes to reach the destination, and they are reassembled upon arrival.
• More efficient for handling bursty or non-continuous data traffic.
• Commonly used in modern computer networks, including the internet.

Types of Packet Switching

• Connectionless Packet Switching (Datagram Switching): Each packet is treated independently and routed based on the information within the packet itself.
• Connection-Oriented Packet Switching (Virtual Circuit Switching): Before data transfer begins, a virtual circuit or path is established between the sender and receiver.

Ethernet Switching

• A type of packet switching commonly used in local area networks (LANs).
• Ethernet switches operate at the data link layer (Layer 2) of the OSI model.
• Switches learn the MAC addresses of devices connected to them and make forwarding decisions based on these addresses.
• Provides more efficient and faster communication within a LAN compared to traditional hub-based networks.
• Reduces collision domains, improving network performance.