Go Back N - ARQ

Duration: 13 min

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Inside: a video lesson and guided study material.

Module outline

  1. Paper - 1 | Unit - 1 | Teaching Aptitude: Concept and Objectives of Teaching / शिक्षण की अवधारणा एवं उद्देश्य, Levels of Teaching / शिक्षण के स्तर, Learner's Characteristics / शिक्षार्थी की विशेषताएँ, Learning: Nature and Theories / अधिगम: प्रकृति एवं सिद्धांत, Cognition, Memory and Metacognition / संज्ञान, स्मृति एवं अधिसंज्ञान, Factors Affecting Teaching / शिक्षण को प्रभावित करने वाले कारक, Effective Teaching and the Teacher / प्रभावी शिक्षण एवं शिक्षक, Instructional Objectives and Lesson Planning / अनुदेशनात्मक उद्देश्य एवं पाठ नियोजन, Methods of Teaching / शिक्षण विधियाँ, Offline and Online Teaching Methods / ऑफ़लाइन एवं ऑनलाइन शिक्षण विधियाँ, Teaching Support System / शिक्षण सहायक प्रणाली, Evaluation Systems / मूल्यांकन प्रणाली, Biological Basis of Emotion / संवेग का जैविक आधार, Central and Peripheral Nervous Systems / केन्द्रीय और परिधीय तंत्रिका तंत्र
  2. Paper - 1 | Unit - 2 | Research Aptitude: Research: Meaning, Features and Scientific Method / अनुसंधान: अर्थ, लक्षण व वैज्ञानिक विधि, Research Paradigms and Approaches / अनुसंधान के प्रतिमान एवं उपागम, Types of Research / अनुसंधान के प्रकार, Variables and Measurement / चर एवं मापन, Methods of Research / अनुसंधान की विधियाँ, Steps of Research / अनुसंधान के चरण, Sampling / प्रतिचयन, Tools and Methods of Data Collection / आँकड़ा संग्रह के उपकरण एवं विधियाँ, Data Analysis and Statistics in Research / आँकड़ा विश्लेषण एवं शोध सांख्यिकी, Thesis and Article Writing / शोध-प्रबंध एवं लेख लेखन, Application of ICT in Research / अनुसंधान में ICT का अनुप्रयोग, Research Ethics / शोध नैतिकता
  3. Paper - 1 | Unit - 3 | Comprehension: Literal Comprehension, Vocabulary and Language in Context, Inferential Comprehension, Critical Comprehension, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions)
  4. Paper - 1 | Unit - 4 | Communication: Communication: Meaning, Nature and Process / संचार: अर्थ, प्रकृति एवं प्रक्रिया, Types and Levels of Communication / संचार के प्रकार एवं स्तर, Verbal and Non-verbal Communication / मौखिक एवं अमौखिक संचार, Semiotics and Meaning / संकेत विज्ञान एवं अर्थ, Models and Theories of Communication / संचार के मॉडल एवं सिद्धांत, Effective Communication / प्रभावी संचार, Barriers to Communication / संचार की बाधाएँ, Classroom Communication / कक्षा संचार, Mass Media: Types and Evolution / जनसंचार माध्यम: प्रकार एवं विकास, Mass Media and Society / जनसंचार एवं समाज, Digital and New Media / डिजिटल एवं नव माध्यम, General Awareness (Legacy Paper 1) / सामान्य जागरूकता (पुराना पेपर 1)
  5. Paper - 1 | Unit - 5 | Mathematical Reasoning and Aptitude: Number System and Simplification / संख्या पद्धति एवं सरलीकरण, Algebra and Ages / बीजगणित एवं आयु, Percentage / प्रतिशतता, Ratio, Proportion, Partnership and Mixtures / अनुपात, समानुपात, साझेदारी एवं मिश्रण, Averages / औसत, Profit, Loss and Discount / लाभ, हानि एवं बट्टा, Simple and Compound Interest / साधारण एवं चक्रवृद्धि ब्याज, Time and Work / समय एवं कार्य, Speed, Time and Distance / चाल, समय एवं दूरी, Mensuration and Geometry / क्षेत्रमिति एवं ज्यामिति, Series / श्रेणी, Coding-Decoding / कूटलेखन-कूटवाचन, Relationships, Directions and Ranking / संबंध, दिशा एवं क्रम, Arrangements, Puzzles, Clock and Calendar / व्यवस्था, पहेलियाँ, घड़ी एवं कैलेंडर, Mathematical Foundations, जीवनी, Philosophy of the Constitution / संविधान का दर्शन, Analysis, Indian Polity and Governance (Legacy Unit 10) / भारतीय राजव्यवस्था और शासन (पुराना यूनिट 10)
  6. Paper - 1 | Unit - 6 | Logical Reasoning: Structure of Arguments / युक्ति की संरचना, Terms, Definitions and Uses of Language / पद, परिभाषा एवं भाषा के उपयोग, Categorical Propositions / निरुपाधिक प्रतिज्ञप्तियाँ, Categorical Syllogism / निरुपाधिक न्यायवाक्य, Venn Diagrams / वेन आरेख, Deduction, Induction and Analogy / निगमन, आगमन एवं सादृश्यता, Fallacies / तर्कदोष, Indian Logic: Pramanas / भारतीय तर्कशास्त्र: प्रमाण, Anumana and Vyapti / अनुमान एवं व्याप्ति, Hetvabhasa / हेत्वाभास, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Aristotle / अरस्तू, Western Schools of Philosophy / पाश्चात्य दर्शन की विचारधाराएँ, Kant / कांट, Sadhana Paada, Vaiśeṣika / वैशेषिक
  7. Paper - 1 | Unit - 7 | Data Interpretation: Data and Graphical Representation / आँकड़े एवं आलेखीय निरूपण, Data Interpretation: Tables / आँकड़ा निर्वचन: तालिका
  8. Paper - 1 | Unit - 8 | Information and Communication Technology: Computer Fundamentals and Hardware, Memory, Storage and Data Representation, Computer Software, Office Applications, Multimedia and File Formats, Computer Networks, Internet and World Wide Web, Email and Online Communication, Cyber Security, Digital Ethics, IPR and Society, Cloud and Distributed Computing, Emerging Technologies, ICT in Education and Governance, Cyber Threats and Malware Attacks, Role of Internet and Web Services, Electronic Data Interchange and E-Commerce, Internet Fundamentals, Web Design & Development, Web Publishing & Hosting, Emerging Technologies, Terms & Abbreviations, Society, Law & Ethics, Keyboard Shortcuts, Website, Browser & Services, Protection of Geographical Indications / भौगोलिक संकेतों का संरक्षण
  9. Paper - 1 | Unit - 9 | People Development and Environment: Ecosystems and Biodiversity / पारितंत्र और जैव विविधता, Human and Environment Interaction / मानव और पर्यावरण की अंतःक्रिया, Development and Environment / विकास और पर्यावरण, Natural Resources – Forests, Water and Soil / प्राकृतिक संसाधन: वन, जल और मृदा, Energy Resources / ऊर्जा संसाधन, Air Pollution / वायु प्रदूषण, Water Pollution and Treatment / जल प्रदूषण और उपचार, Noise Pollution / ध्वनि प्रदूषण, Waste Management / अपशिष्ट प्रबंधन, Environmental Health and Toxicology / पर्यावरणीय स्वास्थ्य और विषविज्ञान, Climate Change and Global Environmental Issues / जलवायु परिवर्तन और वैश्विक पर्यावरणीय समस्याएँ, Natural Hazards and Disaster Management / प्राकृतिक प्रकोप और आपदा प्रबंधन, Indian Environmental Laws and Policies / भारतीय पर्यावरण कानून और नीतियाँ, International Environmental Agreements / अंतर्राष्ट्रीय पर्यावरण समझौते, Environment / पर्यावरण, Geography / भूगोल, Factory and Industry Systems / कारखाना और उद्योग व्यवस्थाएँ, Earth Materials, Surface Features and Processes, Communicable Diseases and Immunization / संक्रामक रोग और प्रतिरक्षण
  10. Paper - 1 | Unit - 10 | Higher Education System: Education in Ancient India / प्राचीन भारत में शिक्षा, Ancient Centres of Higher Learning / प्राचीन भारत के उच्च शिक्षा केंद्र, Colonial Education Policies and Commissions / औपनिवेशिक काल की शिक्षा नीतियाँ और आयोग, Colonial Colleges, Universities and Reformers / औपनिवेशिक कॉलेज, विश्वविद्यालय व सुधारक, Education Commissions and Policies after Independence / स्वतंत्र भारत में शिक्षा आयोग और नीतियाँ, National Education Policy 2020 / राष्ट्रीय शिक्षा नीति 2020, Types of Higher Education Institutions / उच्च शिक्षा संस्थानों के प्रकार, Learning Programmes and Academic Credits / अधिगम कार्यक्रम और अकादमिक क्रेडिट, Professional, Technical and Skill-Based Education / व्यावसायिक, तकनीकी और कौशल आधारित शिक्षा, Value Education and Environmental Education / मूल्य शिक्षा और पर्यावरण शिक्षा, Governance, Administration and Financing / शासन, प्रशासन और वित्तपोषण, Regulation, Accreditation and Ranking / उच्च शिक्षा का नियमन, प्रत्यायन और रैंकिंग
  11. Paper 2 | Unit 1 | Discrete Structures and Optimization: Propositional and Predicate Logic, Set Theory, Relations, Functions, Permutation, Combination and Probability / क्रमचय, संचय एवं प्रायिकता, Graph Theory, Group Theory, Digital Systems & Boolean Basics, Boolean Expression, Boolean Minimization, Optimization, Markov Chains
  12. Paper 2 | Unit 2 | Computer System Architecture: Logic Gates & Hardware, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep, Basics of COA, Register Transfer and Microoperations, Programming the Basic Computer, Instr Formats & Modes, Control Unit Design, Pipelining, Input Output Organisation, Cache Memory Organization, Multiprocessors
  13. Paper 2 | Unit 3 | Programming Languages and Computer Graphics: Language Design, C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, HTML Basics, XML, JavaScript-Basics, Java, Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, 3-D Object Representation, Geometric Transformations and Viewing, OOPS with C++, Java Fundamentals, Array, String, IO & References, OOPS with Java
  14. Paper 2 | Unit 4 | Database Management Systems: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, ORDBMS, Database Security & Authorization, Query Processing & Optimization, Enhanced Data Models, Data Warehousing & Mining, Big Data Systems, NoSQL
  15. Paper 2 | Unit 5 | System Software and Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS, Linux OS, Security, Distributed Systems, Virtual Machines
  16. Paper 2 | Unit 6 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  17. Paper 2 | Unit 7 | Data Structures and Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  18. Paper 2 | Unit 8 | Theory of Computation and Compilers: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines, Complexity Theory, Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  19. Paper 2 | Unit 9 | Data Communication and Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security, Cloud Computing, Mobile Computing
  20. Paper 2 | Unit 10 | Artificial Intelligence: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Planning, Multi Agent Systems, Fuzzy Sets, Natural Language Processing, Artificial Neural Networks, Genetic Algorithms
  21. Full Notes: Paper 1 Full Notes
  22. Paper 1 | Full Mock Tests:
  23. Paper 2 | Full Mock Tests:
  24. Paper 1 | Previous Year Papers:
  25. Paper 2 | Previous Year Papers:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture introduces Go-Back-N Automatic Repeat Request (ARQ), a sliding-window protocol used to keep the channel busy by allowing multiple frames to be in transit while waiting for acknowledgments. The instructor begins with a slide titled “Go-Back-N Automatic Repeat Request,” which explains that multiple frames must be in transition to fill the pipe. A horizontal number-line diagram is used throughout, showing a sequence of numbered frame cells (e.g., 13–15, then 0 through 14). A central orange block highlights the send window (frames 0–6), with arrows labeled S_i and S_{i+1} marking the first outstanding frame and the next frame to send. A bottom bracket states “Send window, size S_max = 2^m - 1.” Region captions under the diagram distinguish “Frames already acknowledged,” “Frames sent, but not acknowledged (outstanding),” “Frames that can be sent, but not received from upper layer,” and “Frames that cannot be sent.” The instructor handwrites notes near the board, including binary-style labels such as “0 (111)” and “15 (111),” likely illustrating sequence-number encoding. The lecture then transitions to a “Timers” slide, which explains that although a timer could exist per frame, the protocol uses only one because “the timer for the first outstanding frame always expires first.” Two side-by-side sender/receiver timing diagrams are shown: “a. Window size < 2^m” and “b. Window size = 2^m.” Each diagram includes numbered frames, frame arrows (e.g., “Frame 0/1/2”), and a “Time-out” marker. Yellow callout boxes at the bottom read “Correctly discarded” (left) and “Erroneously accepted” (right), highlighting the ambiguity problem when window size equals 2^m. The instructor circles and annotates parts of these diagrams, emphasizing the timeout behavior and receiver acceptance decisions. A later slide on “Acknowledgment” states that the receiver is silent and discards subsequent frames until it receives the expected one, which causes the sender’s timer to expire. The final sampled slide revisits the window diagram with numbered cells from 1 through 15, then 0 and 1, with several early cells marked by red X symbols, reinforcing the four-region division of sequence numbers and the send-window constraints.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The lecture opens with the slide “Go-Back-N Automatic Repeat Request,” explaining that multiple frames must be in transition to fill the pipe while waiting for acknowledgment. A horizontal number-line diagram shows a dashed block (13, 14, 15), an orange send-window block of numbered cells (0 through 6), a gray block, and a trailing dashed block. Arrows labeled S_i and S_h mark “Send window, first outstanding frame” and “Send window, next frame to send,” while a bottom bracket reads “Send window, size S_max = 2^m - 1.” Region captions under the diagram include “Frames already acknowledged,” “Frames sent, but not ... (outstanding),” “Frames that can be sent, but not received from upper layer,” and “Frames that cannot be sent.” A hand holding a pen appears at the right edge, then moves up to sketch between handwritten “S” and “R” labels on the whiteboard.

  2. 2:00 – 5:00 02:00-05:00

    The instructor, wearing a black shirt with red trim and later a “KG” logo, stands at the whiteboard pointing to the slide. The numbered frame sequence 0–14 is shown with boxes 0–6 shaded orange, marked by arrows labeled “S_i Send window, first outstanding frame” and “S_{i+1} Send window, next frame to send.” Below the sequence, a bracket reads “Send window, size S_use = 2^m - 1,” with column captions including “Frames that can be sent, but not received from upper layer” and “Frames that cannot be sent.” The instructor writes binary-style notes such as “0 (111)” and “15 (111)” in the upper-right corner near handwritten “S” and “R.” At 205s, a hand-drawn oval encircles the caption “Frames sent, but not acknowledged (outstanding).” The instructor gestures toward the outstanding-frames region, emphasizing the send-window structure.

  3. 5:00 – 10:00 05:00-10:00

    The lecture transitions to a slide titled “Timers,” with left-side text stating that although a timer could exist per frame, the protocol uses only one because “the timer for the first outstanding frame always expires first.” Two timing diagrams sit side by side, captioned “a. Window size < 2^m” and “b. Window size = 2^m,” each with Sender and Receiver columns showing numbered frames, “Frame 0/1/2” arrows, and a “Time-out” marker. Yellow callout boxes at the bottom of each diagram read “Correctly discarded” (left) and “Erroneously accepted” (right). The instructor, in a black “KG KNOWLEDGE GATE” polo, points to diagram b where the receiver box is highlighted with “Erroneously accepted,” while diagram a shows a matching highlight reading “Correctly discarded.” The instructor circles a handwritten “1” near the top of diagram a and adds red marks on diagram b, illustrating the timeout and receiver-acceptance behavior.

  4. 10:00 – 12:34 10:00-12:34

    The presenter stands before Go Back N - ARQ slides, first centered, then on the right facing camera, and finally reaching across to point with a marker. The opening slide’s “Acknowledgment” text states the receiver is silent and discards subsequent frames until it receives the expected one, which makes the sender’s timer expire. Two Sender/Receiver timing diagrams show frame and R-number exchanges, with yellow boxes reading “Correctly discarded” and “Erroneously accepted” plus the label “b. Window size = 2^m.” A later slide says the window divides sequence numbers into four regions, illustrated by a numbered bar running 13–15 then an orange block over 0–6 and gray cells to 14. The final sampled slide shows numbered cells from 1 through 15, then 0 and 1, with several early cells marked by red X symbols. Labels above the diagram read “Send window, first outstanding frame” and “Send window, send frame to send,” reinforcing the four-region division and send-window constraints.

The lecture systematically builds understanding of Go-Back-N ARQ by first establishing the send-window structure and then analyzing timer behavior under different window sizes. The central concept is that multiple frames can be in transit to keep the channel busy, with the send window size constrained by S_max = 2^m - 1. The four-region division of sequence numbers—acknowledged, outstanding, sendable but not yet received from upper layer, and unsendable—is visually reinforced through the orange-highlighted send window and region captions. The timer discussion is critical: only one timer is used because the first outstanding frame’s timer always expires first. The two timing diagrams (window size < 2^m and window size = 2^m) illustrate the ambiguity problem, where a receiver may erroneously accept frames when window size equals 2^m. The “Acknowledgment” slide clarifies that the receiver remains silent and discards frames until it receives the expected one, triggering the sender’s timeout. The final slide revisits the window diagram with red X symbols on early cells, reinforcing the constraints on sendable frames. The lecture progresses from static window structure to dynamic timer and acknowledgment behavior, providing a complete picture of Go-Back-N ARQ operation.

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