Data Communications and Networks

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A comprehensive set of vocabulary flashcards covering fundamental concepts, components, transmission modes, network types, topologies, media, protocols, OSI/TCP-IP models, addressing, and common network applications from the lecture notes.

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31 Terms

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Data communications

Exchange of data between two devices via a transmission medium using hardware and software in a communication system.

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Computer Network

A system of interconnected computers and devices that share resources using a communication channel

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Intermediary Devices vs End devices

End devices are source or destination of data in a network while Intermediary connect end devices

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Data Flow

Simplex - Data moves inly one way

Half duplex - Data moves both ways but one at a time

Duplex - Data moves both ways simultaneously

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Elements that a pritocol controls

Encoding

Formatting

Timing

Size

Delivery options

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Media

Refers to means used to transmit data between devices in a network.

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Wavelength

Distance a simple signal travels during one period; λ = c / f; related to propagation in media.

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Guided media

Also wired media. Transmission media that guide signals along a physical path (twisted-pair, coax, fiber, ethetnet, fiber optic, USB cable).

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Unguided media

Wireless transmission through air/space without a physical conductor. Uses electromagnetic waves like radio, Infrared, Microwaves, Satellite

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Twisted-pair

Two copper conductors twisted to reduce interference; used in telephony and LANs.

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Repeater

Physical-layer device that regenerates signals to extend the distance of a network.

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Network Topologies

Physical or logical arrangement of network components

Bus, Star, Ring, Mesh, Tree, Hybrid

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Network connecting devices

Hub – Connects multiple devices and broadcasts data to all,

Switch – Connects devices and sends data only to the intended device,

Router – Connects different networks and directs data between them,

Bridge – Connects and filters traffic between two network segments,

Gateway – Connects networks using different protocols,

Access Point – Provides wireless connectivity to devices,

Modem – Converts digital signals to analog and vice versa for internet access

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Network security threats

Trojans – Malicious programs disguised as legitimate software that give attackers access to your system,

Worms – Self-replicating malware that spreads across networks without user intervention,

Ransomware – Malware that encrypts files and demands payment to restore access,

Spam – Unsolicited messages, often emails, used to advertise, scam, or deliver malware

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Modulation techniques

Analogue- Amplitude Modulation (AM), Frequency Modulation (FM), Phase Modulation (PM),

Digital - Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), Phase Shift Keying (PSK)

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Encoding

Process of converting data into a specific format for efficient transmission, storage, or security e.g ASII

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Security Measures

Firewall, Antivirus, Encryption, Access Control, Intrusion Detection System (IDS), Strong Passwords, Updates/Patching

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Coaxial Bus

network topology where all devices are connected to a single coaxial cable (the bus) that carries data in both directions.

  • Pros: Simple to install, uses less cable than star topology.

  • Cons: A break in the main cable stops the entire network, performance decreases with more devices.

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Peer-to-Peer (P2P) Workgroup

a type of network where all computers have equal status and can share resources (files, printers) directly without a central server.

  • Pros: Easy to set up, low cost, suitable for small networks.

  • Cons: Harder to manage as the network grows, less secure than server-based networks.

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Conglomeration

refers to the combination of several different companies or entities into a single larger organization, often operating in diverse industries.

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Client-Server Paradigm

a network model where clients (users’ devices) request services from a central server, which processes and provides the requested resources or data.

  • Pros: Centralized management, better security, and easier maintenance.

  • Cons: Server failure can disrupt the entire network; can be expensive to set up.

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Wireless Communication

is the transfer of information between devices without physical cables, using electromagnetic waves such as radio, microwave, or infrared.

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Physical Networks

refer to the actual hardware and layout of a network, including cables, devices, and connection points that enable communication.

Examples of physical network types:

  • LAN (Local Area Network) – Network confined to a small area like an office or building.

  • WAN (Wide Area Network) – Covers large geographical areas, e.g., the internet.

  • MAN (Metropolitan Area Network) – Spans a city or large campus.

  • PAN (Personal Area Network) – Small network for personal devices, e.g., Bluetooth connections.

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Logical Network

Logical Network refers to the virtual or conceptual arrangement of devices and data flow in a network, regardless of the physical connections. It defines how data moves and how devices communicate.

Examples:

  • IP addressing schemes – Defines how devices are identified on the network.

  • VLANs (Virtual LANs) – Groups devices logically even if they are physically apart.

  • Subnets – Divides a network into smaller, manageable segments.

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Open Systems Interconnection (OSI) Reference Model

is a conceptual framework that standardizes how different network systems communicate in seven layers.

Seven layers of OSI

Application Layer → Presentation Layer –> Session Layer –> Transport Layer –> Network Layer –> Data Link Layer → Physical Layer

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Error division strategies

are techniques used in networks to identify and fix errors that occur during data transmission.

Common strategies:

  • Parity Check – Adds a parity bit (even or odd) to detect single-bit errors.

  • Checksum – Sums data values and sends the result; receiver checks for consistency.

  • Cyclic Redundancy Check (CRC) – Uses polynomial division to detect errors in data blocks.

  • Hamming Code – Adds redundant bits to detect and correct single-bit errors.

  • Automatic Repeat Request (ARQ) – Requests retransmission when errors are detected.

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Logical vs Physical topologies

Logical Topology – Shows how data flows in a network, regardless of physical connections, e.g., token passing in a ring network.

Physical Topology – Shows the actual layout of cables and devices in a network, e.g., star or bus layout.

Key Difference: Logical focuses on data movement, physical focuses on device connections.

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Types of Casting

Types of Casting – Methods of delivering data to devices in a network:

  • Unicast – Data sent from one sender to one specific receiver.

  • Broadcast – Data sent from one sender to all devices in the network.

  • Multicast – Data sent from one sender to a specific group of devices.

  • Anycast – Data sent from one sender to the nearest or best receiver in a group.

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Protocols

are rules and standards that govern how data is transmitted and received over a network. They ensure devices can communicate effectively.

Common network protocols:

  • HTTP/HTTPS – For web browsing and secure web communication.

  • FTP – For transferring files between devices.

  • SMTP – For sending emails.

  • IMAP/POP3 – For receiving emails.

  • TCP – Ensures reliable data transmission.

  • UDP – Sends data quickly without guaranteed delivery.

  • IP – Addresses and routes packets across networks.

  • DNS – Converts domain names into IP addresses.

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Multiplexing

combine multiple signals or data streams over a single communication channel to optimize resource use.

Common types of multiplexing:

  • Frequency Division Multiplexing (FDM) – Different signals use different frequency bands.

  • Time Division Multiplexing (TDM) – Signals take turns using the channel in time slots.

  • Wavelength Division Multiplexing (WDM) – Used in fiber optics; signals use different light wavelengths.

  • Code Division Multiplexing (CDM) – Signals are encoded with unique codes to share the same channel.

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Bandwidth

is the maximum amount of data that can be transmitted over a network channel in a given time, usually measured in bits per second (bps).

  • Higher bandwidth → More data can be sent quickly.

  • Lower bandwidth → Slower data transmission.