Chapter 1 Data Communication and Networking

Essential vocabulary flashcards covering the components of communication models, transmission types, network topologies, switching methods, access control, multiplexing techniques, and the OSI 7-layer architecture.

Data Communication Network

A collection of two or more computing devices interconnected to enable them to share data.

Source

The component that generates the raw information, such as text or voice.

Source Encoder

Converts information into an electrical form called a message signal, $m(t)$.

Transmitter (TX)

Converts the message signal into a form acceptable to the transmission channel.

Channel

The physical path or link connecting the transmitter and receiver, such as copper wire, optical fiber, or air.

Receiver (RX)

Performs the inverse function of the transmitter to recover the message signal from the channel.

Source Decoder

Converts the electrical signal back into a form acceptable and understandable to the final user.

Sink

The final user or destination of the information generated by the source.

Asynchronous Transmission

A transmission method in which data is sent one character at a time, with each character framed by a start bit and one or two stop bits, across irregular or indefinite time intervals.

Synchronous Transmission

A transmission method in which data is sent in continuous blocks called frames delimited by special multi-bit flag patterns, requiring synchronization between sender and receiver.

Asynchronous vs. Synchronous Transmission Schemes

Visual representation showing (a) character-oriented asynchronous transmission with start/stop bits and indefinite intervals, and (b) frame-oriented synchronous transmission delimited by start and end FLAG fields.

Simplex Transmission

A transmission mode where data flows in one direction only, permanently from the source to the sink.

Half-Duplex (HDX) Transmission

A transmission mode where data can flow in both directions, but never at the same time; stations must alternate turns transmitting and receiving.

Full-Duplex (FDX) Transmission

A transmission mode where data can flow in both directions simultaneously across the link.

Network Topology

The physical or logical geometrical arrangement or configuration of nodes and links in a network.

Point-to-Point (P2P) Topology

A topology where a single dedicated link permanently connects two individual nodes.

Point-to-Multipoint Topology

A configuration in which one central node is connected to multiple other nodes, each via an independent point-to-point connection.

Multidrop Topology

A configuration where all nodes share a single link, controlled by a single master node with all other nodes acting as slaves.

Bus Topology

A topology where all nodes share a single transmission medium (the bus) as peer devices with no master-slave relationship.

Ring Topology

A topology where nodes are connected serially in a point-to-point chain, with the last node looped back to the first to form a closed loop.

Star Topology

A topology where every node is connected via a dedicated point-to-point link to a central device called a hub that manages traffic.

Tree Topology

A hierarchical network structure formed by connecting multiple buses or stars, where data flows downward from a root headend node through branching links.

Mesh Topology

A network configuration where nodes are interconnected in an arbitrary structure, using internal switching nodes to route data toward the destination.

Personal Area Network (PAN)

A network covering approximately $10\,\text{meters}$ around an individual to connect personal devices such as a phone, laptop, and Bluetooth headset.

Local Area Network (LAN)

A network covering a restricted geographical scale such as a single room, building, floor, or small campus.

Metropolitan Area Network (MAN)

A network that interconnects multiple local area networks across a town, city, or large campus.

Wide Area Network (WAN)

A network providing communication coverage over large geographical spans, such as a country or the entire globe.

Guided Transmission (Wired)

A transmission approach where electromagnetic signals propagate through a solid physical path, such as twisted pair cable, coaxial cable, or optical fiber.

Unguided Transmission (Wireless)

A transmission approach where signals propagate freely through air or empty space using radio waves or microwaves.

Switched Network

A network in which data is routed from source to destination across a specific subset of intermediate switching nodes.

Broadcast Network

A network where a transmission from a source is received by all devices on the medium, requiring destination addressing within the message.

Circuit Switching

A switching technique that establishes a dedicated physical communication path between sender and receiver for the entire duration of a communication session.

Call Setup Phase

The initial phase of circuit switching used to establish the dedicated communication path between the source and the sink.

Call Teardown Phase

The final phase of circuit switching used to clear, release, or terminate the dedicated communication path after communication has finished.

Packet Switching

A data transfer technique where data is segmented into packets and routed across nodes via store-and-forward without reserving a dedicated path.

Store-and-Forward

A packet-switching technique where a network node receives an entire packet, checks it for errors, and forwards it to the subsequent node.

Virtual Circuit

A packet-switching mode where a single logical path is pre-established before data transmission, ensuring all session packets follow the exact same path.

Datagram Service

A packet-switching mode where every packet is addressed and routed independently, allowing packets of the same message to travel along different paths.

Centralized Polling (Roll-Call Polling)

A controlled access scheme used in master-slave networks where the central controller uses a round-robin schedule to invite each station to transmit.

Distributed Polling

A controlled access scheme typically using token passing in peer-to-peer networks, where stations transmit when in possession of a token and then pass it along in logical order.

Frequency-Division Multiplexing (FDM)

A media sharing technique where the channel frequency spectrum is divided into smaller discrete channels, giving each user part of the frequency all of the time.

Time-Division Multiplexing (TDM)

A media sharing technique where transmission time is sliced into distinct time slots assigned sequentially, giving each user all of the frequency for part of the time.

Spread Spectrum (SS)

A media sharing technique where a signal is spread across a broad frequency band using unique, uncorrelated codes, allowing all users to transmit simultaneously across the entire band.

Media Sharing Schemes

Graphical coordinate models depicting Frequency-Division Multiplexing (FDM), Time-Division Multiplexing (TDM), and Spread Spectrum (SS) allocations over frequency and time axes.

OSI Reference Model

A 7-layer architectural framework proposed by the ISO to standardize intercomputer communication by dividing functionality into distinct modular layers.

Physical Layer (Layer 1)

The OSI layer responsible for defining electrical and mechanical standards to transmit unstructured raw bit streams ($0$s and $1$s) over a physical medium.

Data Link Layer (Layer 2)

The OSI layer that organizes data bits into frames and detects transmission errors that occur across a single link.

Network Layer (Layer 3)

The OSI layer that assigns unique network addresses (e.g., IP) and determines routing paths across the network to the destination.

Transport Layer (Layer 4)

The OSI layer responsible for reliable, end-to-end data transfer, flow control, and error recovery between source and destination endpoints.

Session Layer (Layer 5)

The OSI layer that establishes, maintains, and terminates communication sessions and dialogues between software applications.

Presentation Layer (Layer 6)

The OSI layer that translates, encrypts, and compresses data, formatting it into a common representation understood by the receiving system.

Application Layer (Layer 7)

The top OSI layer that provides network services, protocols, and interfaces directly to end-user software applications.

Service Data Unit (SDU)

The raw data payload delivered from an adjacent upper layer to the layer immediately below it during protocol encapsulation.

Protocol Control Information (PCI)

Control information or header data added by a protocol layer containing instructions intended for its peer layer at the receiving entity.

Protocol Data Unit (PDU)

The combined data packet generated at a specific layer, consisting of the incoming Service Data Unit (SDU) packaged with that layer's Protocol Control Information (PCI).

Protocol

A formal set of rules and conventions that govern and ensure the effective exchange of information between devices.