Computer Networking: Data Communication, Switching, Topologies, and Transport Protocols

Comprehensive vocabulary flashcards covering computer networking principles including transmission media, signal processing, impairments, data link control, switching methodologies, network topologies, internetworking hardware, the OSI model, TCP/IP protocol suite, and IBM SNA.

Computer Network

A collection of interconnected devices (such as mobiles, laptops, printers, routers, and servers) that communicate and share resources.

Components of Data Communication

The four essential elements required for transmission: Sender (source device that generates data), Message (data/information to communicate), Transmission Medium (physical path carrying data), and Receiver (destination device).

Jitter

The variation in packet arrival times. High jitter causes uneven packet delivery and degrades quality in real-time voice and video communication.

Transmission Media

The physical path or channel carrying signals from sender to receiver, categorized into Wired (Guided) media like twisted pair, coaxial, and fiber optic, and Wireless (Unguided) media like radio waves, microwaves, and infrared.

Analog Signal

A continuous electrical or electromagnetic wave that changes smoothly over time and can take an infinite number of possible values within a given range.

Digital Signal

A discrete signal that has only two possible voltage levels or states, usually represented as binary $0$ (LOW) and $1$ (HIGH), changing in abrupt steps.

Attenuation

A transmission impairment characterized by the loss of signal strength (amplitude or power) as it propagates through a medium over distance, calculated in decibels as $\text{Attenuation (dB)} = 10 \log_{10}\left(\frac{P_{\text{in}}}{P_{\text{out}}}\right)$.

Distortion

The alteration of a signal's shape or waveform occurring when different frequency components travel at different speeds or encounter limited bandwidth, comprising amplitude, delay (phase), and frequency distortion.

Noise

Any unwanted, random electrical disturbance added to an original signal during transmission, quantified relative to signal power by the Signal-to-Noise Ratio: $\text{SNR (dB)} = 10 \log_{10}\left(\frac{P_{\text{signal}}}{P_{\text{noise}}}\right)$.

Data Encoding

The process of converting data into a suitable signal form for transmission across a medium, spanning four primary combinations: Digital-to-Digital, Digital-to-Analog, Analog-to-Digital, and Analog-to-Analog.

Analog-to-Digital Conversion (ADC)

The transformation of continuous analog signals into discrete binary sequences through three sequential stages: Sampling (measuring at regular intervals), Quantization (rounding samples to discrete levels), and Encoding (converting levels into binary $0$s and $1$s).

Asynchronous Transmission

A serial transmission mode where data is transmitted one character (byte) at a time, delineated by a Start bit ($0$) and one or more Stop bits ($1$), with variable idle gaps between characters and no shared clock.

Synchronous Transmission

A high-speed transmission mode where data is sent as an unbroken, continuous stream of bits organized into frames without start/stop bits per character, synchronized between transmitter and receiver using a shared common clock.

Interfacing

The connection and conditioning circuitry between two systems to resolve mismatches in voltage levels, logic levels, timing, data formats (serial vs. parallel), and transmission speeds.

OSI Reference Model

A 7-layer conceptual framework for network communication: Layer 7 Application, Layer 6 Presentation, Layer 5 Session, Layer 4 Transport, Layer 3 Network, Layer 2 Data Link, and Layer 1 Physical.

Framing

The Data Link Layer process of encapsulating network-layer bit streams into distinct transmission units (frames) with header and trailer control fields, using methods such as character counts, byte stuffing, or bit stuffing (inserting a $0$ after five consecutive $1$s).

MAC Address

A 48-bit (6-byte) unique hardware identifier embedded in a Network Interface Controller (NIC), formatted in hexadecimal with an Organizationally Unique Identifier (OUI) and a NIC-specific identifier, operating at the Data Link Layer.

Flow Control

A data link and transport layer mechanism designed to regulate data transmission rates, preventing a fast sender from overwhelming a slow receiver's buffer using schemes such as Stop-and-Wait or Sliding Window.

Packet vs Frame

A Packet is the Layer 3 (Network Layer) protocol data unit containing IP addresses for end-to-end delivery across networks; a Frame is the Layer 2 (Data Link Layer) unit containing MAC addresses for node-to-node delivery on a local link.

Single-Bit Error vs Burst Error

A single-bit error is corruption where only one bit in a data block changes from $0$ to $1$ or $1$ to $0$; a burst error occurs when two or more consecutive or non-consecutive bits are corrupted due to noise or interference.

Parity Bit

A single redundant bit appended to a data word to make the total count of $1$s either even (Even Parity) or odd (Odd Parity), capable of detecting single-bit errors but unable to catch an even number of bit inversions.

Cyclic Redundancy Check (CRC)

An error-detection technique treating binary data as a polynomial and dividing it by an agreed-upon generator polynomial using modulo-2 (XOR) arithmetic; the generated remainder is appended as the Frame Check Sequence (FCS).

Automatic Repeat reQuest (ARQ)

A feedback-based error-control technique at the Data Link Layer combining error detection with acknowledgments (ACK/NAK) and retransmissions, executed via Stop-and-Wait ARQ, Go-Back-N ARQ, or Selective Repeat ARQ.

Forward Error Correction (FEC)

An error-control method that appends redundant check bits ($r$ bits added to $k$ data bits to form an $n = k + r$ codeword) enabling the receiver to autonomously detect and correct errors without requesting retransmission.

Data Link Control (DLC) Protocol

A Layer 2 set of rules managing framing, addressing, error control, flow control, and medium access control over point-to-point or multipoint connections, exemplified by HDLC, PPP, and IEEE 802.3 Ethernet.

High-Level Data Link Control (HDLC)

An ISO-standardized, bit-oriented synchronous data link protocol supporting point-to-point and multipoint configurations, utilizing flag bytes ($01111110$), CRC error detection, sliding window flow control, and three frame types: I-frames, S-frames, and U-frames.

Point-to-Point Protocol (PPP)

A byte-oriented Data Link Layer protocol designed for direct point-to-point connections, featuring framing with flag byte $0\text{x}7\text{E}$, protocol multiplexing, link quality testing, and authentication protocols such as PAP and CHAP.

Multiplexing

The technique of combining multiple input signals or data streams from different sources via a Multiplexer (MUX) for simultaneous transmission over a single shared physical channel, separated at the receiver by a Demultiplexer (DMUX).

Frequency Division Multiplexing (FDM)

An analog multiplexing technique in which the total available channel bandwidth is subdivided into distinct, non-overlapping frequency bands separated by unused guard bands, allowing all signals to transmit concurrently.

Time Division Multiplexing (TDM)

A digital multiplexing method where users take turns sharing a communication channel by allocating the entire frequency bandwidth to each signal within designated, repeating cyclic time slots.

Circuit Switching

A connection-oriented networking approach establishing a dedicated, physical end-to-end circuit across switches with reserved bandwidth and constant delay before communication commences, requiring three phases: Setup, Data Transfer, and Release.

Packet Switching

A method of network transmission where messages are divided into small, independent data blocks (packets) containing address headers that are routed dynamically across a shared network without dedicated end-to-end paths.

Virtual Circuit (VC)

A connection-oriented packet-switching technique where a predetermined logical path is established across routers using VC identifiers before data transfer; all packets travel sequentially along this identical route.

Open-Loop Traffic Control

Congestion prevention mechanisms operating proactively according to fixed, predefined rules without using network feedback, including Admission Control, Resource Reservation, Traffic Shaping (Leaky Bucket), and Packet Discard policies.

Closed-Loop Traffic Control

Congestion management mechanisms that monitor the active network, detect congestion states, and transmit feedback signals back to senders to adjust transmission rates (e.g., via Backpressure, Choke Packets, or Explicit Rate Control).

X.25

An ITU-T (formerly CCITT) standard for packet-switched communication over public networks using connection-oriented virtual circuits, providing end-to-end error control, flow control, and interfacing between DTE and DCE devices.

Switching Fabric

The internal hardware and connection matrix inside a digital switch or router that directs incoming data from any input port directly to its designated output port.

Control Signaling

The exchange of non-payload operational messages between network switches to coordinate call setup, path auditing, active connection management, and call teardown.

Ethernet (IEEE 802.3)

The standard wired LAN technology using switch-based star topologies and UTP or optical cables, transmitting data in frames structured with MAC addressing, a $46\text{--}1500\,\text{byte}$ payload, and a $4\text{-byte}$ CRC trailer.

Bus Topology

A network layout where all devices are connected directly to a central shared transmission line (backbone cable) terminated at both ends to absorb signals and prevent reflection.

Star Topology

A network arrangement where all individual nodes connect via dedicated point-to-point links directly to a central hub, switch, or access point that directs all traffic.

Ring Topology

A closed-loop network configuration where each device connects to exactly two neighbors, circulating data unidirectionally or bidirectionally via token passing until reaching the destination.

Mesh Topology

A network topology where every node is interconnected to other nodes via point-to-point links; a fully connected mesh of $n$ devices requires $\frac{n(n-1)}{2}$ physical links.

Tree Topology

A hierarchical network architecture integrating star and bus topologies organized into root (core switch), branch (distribution switches), and leaf (access switches and end hosts) tiers.

Optical Fiber

A cylindrical transmission strand consisting of a glass/plastic Core surrounded by a Cladding layer of lower refractive index that propagates data as light pulses via total internal reflection, shielded by strength material and an outer jacket.

CSMA/CD

Carrier Sense Multiple Access with Collision Detection; a contention-based MAC protocol used in wired Ethernet where stations listen before sending, detect concurrent transmission collisions, halt, and retry after a random backoff period.

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance; a wireless MAC protocol used in Wi-Fi (IEEE 802.11) where devices verify medium availability and defer transmission using random backoff intervals to proactively avoid packet collisions.

WiMAX (IEEE 802.16)

Worldwide Interoperability for Microwave Access; a broadband wireless Metropolitan Area Network (MAN) standard delivering point-to-multipoint last-mile broadband connectivity across licensed frequency bands ($2\text{--}66\,\text{GHz}$).

Distributed Queue Dual Bus (DQDB)

An IEEE 802.6 metropolitan network backbone standard based on a dual-bus fiber-optic architecture (primary and secondary buses) providing fault-tolerant, bidirectional transmission at rates typically ranging from $34\,\text{Mbps}$ to $100\,\text{Mbps}$.

Repeater

A Physical Layer (OSI Layer 1) device that receives weakened or attenuated signals, cleans noise, regenerates their original electrical/optical amplitude, and retransmits them to extend coverage distance.

Bridge

A Data Link Layer (OSI Layer 2) internetworking device that segments local networks and filters/forwards data frames between segments based on learned MAC address tables.

Router

A Network Layer (OSI Layer 3) device that interconnects logically distinct networks, maintaining routing tables and evaluating destination IP addresses to determine the optimal next hop.

Gateway

An internetworking entity operating at Layer 3 or above that translates protocols, formats, or addressing systems between fundamentally disparate network architectures (e.g., LAN to Internet).

Communication Model

A framework outlining data exchange between systems consisting of a Source (generates message), Transmitter (encodes message into signals), Transmission Medium (carries signals subject to noise), Receiver (recovers data from signals), and Destination.

TCP/IP Protocol Suite

The foundational Internet communications framework organized into four functional layers: Application (services like HTTP, DNS, SMTP), Transport (process delivery via TCP/UDP), Internet (routing via IP/ICMP), and Network Access / Link (Ethernet, Wi-Fi).

Transmission Control Protocol (TCP)

A reliable, connection-oriented Transport Layer protocol providing ordered byte-stream delivery using three-way handshakes, sequence numbers, positive acknowledgments, dynamic retransmission, and flow/congestion controls.

User Datagram Protocol (UDP)

A lightweight, connectionless Transport Layer protocol that transmits independent datagrams without establishing a connection, offering low latency with no guarantees of ordering, delivery, or error recovery.

Internet Protocol (IP)

The principal connectionless protocol of the TCP/IP Internet Layer providing host logical addressing and packet routing across heterogeneous networks on a best-effort basis without delivery guarantees.

Internet Control Message Protocol (ICMP)

A network-layer companion protocol to IP used by network devices and utilities like ping to transmit operational diagnostics and error status messages.

Systems Network Architecture (SNA)

A proprietary 7-layer networking architecture designed by IBM for mainframe-terminal communications, structured into: Layer 7 Transaction Services, Layer 6 Presentation Services, Layer 5 Data Flow Control, Layer 4 Transmission Control, Layer 3 Path Control, Layer 2 Data Link Control, and Layer 1 Physical Control.