Efficiency of Stop and Wait Protocol - ARQ

Duration: 6 min

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Module outline

  1. Quantitative Aptitude: Number System, Divisibility Rules, HCF LCM, Percentage, Ratio and Proportion (Ratios), Average, Profit and Loss, Simple Interest and Compound Interest, Mixture and Alligation, Partnership, Age Problems, Time and Work, Pipe and Cistern, Speed Time and Distance, Algebra, Arithmetic, Data Interpretation, Sequence and Series (Series), Logarithm, Powers and Exponents (Surds and Indices), Permutation and Combination, Probability, Speed Mathematics and Basic Mathematics, Trigonometry
  2. Logical Reasoning: Coding Decoding, Blood Relations, Directions (Direction Test), Ranking, Order and Sequence, Seating Arrangements, Puzzle Solving (Puzzles), Data Arrangement, Syllogisms, Inequality, Data Sufficiency, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Series (Number and Letter Series) (Numerical Relations and Reasoning), Venn Diagram, Logical Sequence Of Words, Calendar, Clock, Cubes & Dices, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning)
  3. Verbal Ability: Noun, Pronoun, Adjectives, Verb, Adverb, Tenses, Subject Verb Agreement (Verb Noun Agreement), Articles, Preposition, Conjunction, Modals, Determiner, Vocabulary, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Cloze Test (Cloze Passage), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Active Passive Voice (Voice), Direct and Indirect Speech, Sentence Construction
  4. Data Structures (Domain Test): Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  5. Algorithms (Domain Test):
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  7. DBMS (Domain Test): Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, 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
  8. SQL (Domain Test): SQL
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  10. Computer Networks (Domain Test): 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 and IoT, Cyber and Info Security
  11. Coding: Coding Questions by Yash Sir, C Programming by Yash Sir, Programming in C++, Java, Python for Placements by Yash Sir
  12. Written English Test: English Writing Ability
  13. Psychometric Test: Behavioral Assessment (Behavioral Competency Profiling) (Psychometric Test)
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture explains the efficiency of the Stop and Wait ARQ protocol, deriving the formula η = 1 / (1 + 2a) and calculating effective bandwidth. The instructor begins by defining efficiency as the ratio of useful transmission time (Tt) to total cycle time, which includes waiting periods for acknowledgments. Through algebraic simplification, the formula is reduced to a function of 'a', representing the ratio of propagation delay (Tp) to transmission time. The session concludes with a numerical example calculating throughput based on efficiency and bandwidth.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the concept of efficiency for Stop and Wait ARQ, displaying a slide titled "Efficiency(n):" with the initial formula Useful Time / Total Cycle time = Tt / (Tt + 2 * Tp). He explains that useful transmission time is Tt, while the remaining 2 * Tp represents waiting time for processing. The derivation proceeds by dividing both numerator and denominator by Tt, resulting in the simplified expression n = 1 / (1 + 2 * Tp/Tt). The variable 'a' is defined as the ratio Tp / Tt, leading to the final efficiency formula η = 1 / (1 + 2a).

  2. 2:00 – 5:00 02:00-05:00

    The lecture continues with the derivation of the efficiency formula η = 1 / (1 + 2a), emphasizing that total time consists of transmission and propagation delays while queuing and processing delays are negligible. A handwritten note on the slide identifies 2 * Tp as Round Trip Time (RTT). The instructor then transitions to defining Throughput or Effective Bandwidth using the formula: Throughput = η * B. This section solidifies the relationship between efficiency and actual data transfer rates, preparing for a numerical application.

  3. 5:00 – 5:43 05:00-05:43

    The instructor calculates the effective bandwidth for a Stop and Wait protocol by substituting values into the formula Throughput = η * B. With an efficiency (η) of 0.5 and bandwidth (B) of 10 Mbps, the calculation yields a final throughput of 5 Mbps. The result is written and underlined on screen as "5 x 10 Mbps = 5 Mbps". The instructor then begins to illustrate the concept with a diagram representing data frames, visualizing how efficiency impacts frame transmission.

The lecture systematically derives the efficiency metric for Stop and Wait ARQ, starting from fundamental time components. The core formula η = 1 / (1 + 2a) highlights how propagation delay relative to transmission time degrades performance. By defining 'a' as Tp/Tt, the instructor simplifies complex timing relationships into a single variable. The final application demonstrates that even with high bandwidth, low efficiency significantly reduces effective throughput, as shown in the 5 Mbps result from a 10 Mbps link. This progression from theoretical derivation to practical calculation reinforces the importance of minimizing propagation delay in network design.

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