Data Comm & Network Fundamentals

Cheatsheet Content

1.1 Data Communication Process & Components Data Communication: Exchange of data between two devices via some form of transmission medium. Components: Message: The information to be communicated (text, numbers, pictures, audio, video). Sender (Transmitter): Device that sends the data message. Receiver: Device that receives the data message. Medium: Physical path over which a message travels (e.g., twisted-pair wire, fiber-optic cable, radio waves). Protocol: A set of rules governing data communication. It represents an agreement between communicating devices. 1.2 Protocols, Standards & Rates Protocols: Rules that allow devices to communicate. They define: What is communicated. How it's communicated. When it's communicated. Standards: Agreed-upon rules for data communication. Ensure interoperability. De Facto: Standards that have not been endorsed by an organized body but have been adopted widely (e.g., TCP/IP). De Jure: Standards that have been legislated by an officially recognized body (e.g., IEEE 802.3 for Ethernet). Standard Organizations: ISO: International Organization for Standardization IEEE: Institute of Electrical and Electronics Engineers ANSI: American National Standards Institute ITU-T: International Telecommunication Union - Telecommunication Standardization Sector Bandwidth: The range of frequencies contained in a composite signal, or the capacity of a link. Measured in Hertz (Hz) for analog, bits per second (bps) for digital. Data Transmission Rate (Bit Rate): The number of bits transmitted per second. Measured in bps. Baud Rate: The number of signal units (symbols) transmitted per second. Each signal unit can carry one or more bits. Bits per second (bps): The actual data speed. If one baud carries $n$ bits, then bps = baud rate $\times n$. 1.3 Modes of Communication Simplex: Unidirectional communication. Only one device can transmit, the other can only receive. Example: Radio broadcast, television broadcast, keyboard to computer. Half-Duplex: Bidirectional communication, but not simultaneously. Devices can transmit and receive, but not at the same time. Example: Walkie-talkie, CB radio. Full-Duplex: Bidirectional simultaneous communication. Both devices can transmit and receive at the same time. Example: Telephone conversation, Ethernet. 1.4 Analog & Digital Signals/Transmission Analog Signal: Continuous wave that constantly varies with time. Characterized by amplitude, frequency, and phase. Example: Voice, traditional radio waves. Digital Signal: Discrete signal composed of a finite number of values (typically 0 and 1). Represented by pulses. Example: Computer data. Analog Transmission: Transmitting analog signals over analog channels. Can be susceptible to noise. Digital Transmission: Transmitting digital signals over digital channels. More robust to noise. Analog to Digital (A/D) Conversion: Process of converting an analog signal into a digital signal. Methods: Pulse Code Modulation (PCM), Delta Modulation (DM). PCM Steps: Sampling, Quantization, Encoding. Device: Analog-to-Digital Converter (ADC). Digital to Analog (D/A) Conversion: Process of converting a digital signal into an analog signal. Methods: Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), Phase Shift Keying (PSK). Device: Digital-to-Analog Converter (DAC). 1.5 Fundamentals of Computer Network Definition: A computer network is a group of interconnected computers and other devices that can share resources and data. Need for Computer Network: Resource Sharing (printers, scanners, storage). Information Sharing (databases, files). Communication (email, instant messaging, video conferencing). Centralized Management (data backup, security). Cost Reduction (shared hardware/software). Reliability (alternative sources of data). Applications: Email, Web browsing, E-commerce. Online banking, Social media. Cloud computing, Online gaming. Voice over IP (VoIP), Video streaming. Network Benefits: Increased efficiency and productivity. Enhanced collaboration. Access to a wider range of information. Reduced operational costs. Improved data security and backup options. 1.6 Classification of Network Local Area Network (LAN): Covers a small geographical area (e.g., home, office building, campus). Privately owned and managed. High data transfer rates. Technologies: Ethernet, Wi-Fi. Metropolitan Area Network (MAN): Covers a city or a large campus. Larger than a LAN, smaller than a WAN. Often interconnects several LANs. Typically owned by a single organization or a consortium. Wide Area Network (WAN): Covers a large geographical area (e.g., countries, continents). Interconnects multiple LANs and MANs. Often uses public telecommunication lines (e.g., Internet). Lower data transfer rates compared to LANs, higher latency.