Preamble and SFD

Duration: 3 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):
  6. OOPs (Domain Test): Object Oriented Programming (OOPS)
  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 short lecture segment introduces the Preamble and Start Frame Delimiter (SFD) fields of an Ethernet frame. The instructor presents a slide titled “Preamble,” defining it as a 7-byte field containing alternating 0s and 1s, equivalent to 56 bits. The slide notes that the Preamble is added at the physical layer and serves synchronization purposes. An Ethernet frame diagram labels the fields in order: Preamble (7 bytes), SFD (1 byte), Destination address (6 bytes), Source address (6 bytes), Length (2 bytes), Data and padding, and CRC (4 bytes). The instructor circles the Destination and Source address fields. On-screen notes also mention minimum payload length of 46 bytes, maximum payload length of 1500 bytes, and minimum frame length of 512 bits or 64 bytes. The lesson then transitions to the SFD slide, stating that it is a 1-byte field always set to 10101011, with the final two bits “11” marking the beginning of the frame. The SFD is also added at the physical layer, and a note indicates that historically only the SFD existed before the Preamble was added later.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The slide titled “Preamble” defines the field as a 7-byte sequence of alternating 0s and 1s, shown on-screen as “Preamble: 56 bits of alternating 1s and 0s.” The instructor explains that the Preamble is added at the physical layer for synchronization. An Ethernet frame diagram displays labeled blocks: Preamble (7 bytes), SFD (1 byte), Destination address (6 bytes), Source address (6 bytes), Length (2 bytes), Data and padding, and CRC (4 bytes). Handwritten ovals circle the Destination and Source address fields. Additional on-screen notes state minimum payload length 46 bytes, maximum payload length 1500 bytes, and minimum frame length 512 bits or 64 bytes.

  2. 2:00 – 2:53 02:00-02:53

    The presentation switches to a slide titled “Start Frame Delimiter (SFD),” which states that the SFD is a 1-byte field always set to “10101011.” The slide highlights that the last two bits, “11,” mark the beginning of the frame and that the SFD is added at the physical layer. A note below reads “only SFD was there Preamble was added later,” indicating the historical development of these fields. The instructor gestures while explaining, and the frame diagram remains visible with Preamble labeled as 7 bytes and SFD as 1 byte.

The central teaching point is the structure and purpose of the Preamble and SFD in Ethernet framing. The Preamble provides synchronization through a 7-byte alternating bit pattern, while the SFD signals frame start with its fixed value 10101011, where the trailing “11” distinguishes it from the alternating pattern. Both fields are physical-layer additions, and the diagram situates them before the data-link layer addresses and payload. The historical note that SFD preceded Preamble adds context for why both exist.

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