TCP Header-Window Size Field

Duration: 8 min

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Module outline

  1. HPSC Interview Preparation: Interview Preparation
  2. Python Language: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis, DSA using Python
  3. Data Structure & Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Sorting Algorithms, Minimum Spanning Trees, Time Complexity Analysis, Graph Theory, Shortest Path Algos
  4. Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security
  5. Computer System & Organisation: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Programming the Basic Computer
  6. Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, SQL, File Organization & Indexing, Transaction Management, Concurrency Control
  7. Operating Systems: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling
  8. Digital Logic & Circuits: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  9. Theory Of Computation: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Pushdown Automata & CFG, Turing Machines, Moore & Mealy Machines
  10. Compiler Design: 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
  11. Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management, Data Warehousing & Mining
  12. Introduction to Emerging Trends: Emerging Tech Trends
  13. Digital Society & Cyber Law: Society, Law & Ethics
  14. HPSC PGT Previous Year Paper:
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  16. Live Sessions: HPSC Live Sessions, EMRS TGT/PGT Live Class
  17. Full Mock Test:
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AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The lecture introduces TCP flow control via the Window Size field, emphasizing that a sender must never transmit data exceeding what the receiver can accept. The 16-bit field defines the number of bytes reserved by the receiver, capping the window at 2^16 = 65,535 bytes. The instructor maps this to a sender-receiver diagram (RC/RS) and notes that the receiver determines the window size. Later, the slide explains that 14 additional bits can be taken from options to extend the window size to 30 bits, allowing up to approximately 1GB of advertised data.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The slide titled "Window Size/Advertisement window(Flow control)" presents the core principle: "Basics idea is a sender should never send what a receiver can not receive." A TCP header table lists "Window size 16 bits" alongside "Sequence number 32 bits" and a blue bar for "Options and padding (up to 40 bytes)." A segment diagram shows a Header box and Data bar marked "20 to 60 bytes." The instructor begins explaining that the window size field defines the receiver's reserved buffer space.

  2. 2:00 – 5:00 02:00-05:00

    The instructor draws a whiteboard diagram with labels "RC" (receiver) and "RS" (sender) to illustrate flow control. Handwritten annotations show the calculation "2^16 = 65,535" and a box labeled "16KB," linking the 16-bit field length to its maximum byte capacity. The instructor points directly at the "Window size 16 bits" field in the TCP header table, emphasizing that this value is determined by the receiver and dictates how much data the sender may transmit. The slide text reiterates: "Note that the length of this field is 16 bits, which means that the maximum size of the window is 65,535 bytes."

  3. 5:00 – 7:49 05:00-07:49

    The lecture transitions to extending the window size. The slide states that the 16-bit field advertises very little data, but "additional 14 bits can be taken from options so total size become 30 bits or 1GB." Red pen marks circle "14 bits can be taken" and underline the second bullet. Handwritten notes on the right show "2^" next to a circled "1GB," with a crossed-out boxed "64." The segment diagram and TCP header table remain visible, reinforcing that the options field (up to 40 bytes) provides space for these extra bits.

The lecture progresses from defining the TCP Window Size field to calculating its maximum capacity and finally extending it via options. Key concepts include: (1) Flow control principle—sender must not exceed receiver capacity; (2) The 16-bit window size field limits the advertised window to 65,535 bytes (2^16); (3) The receiver determines the window size; and (4) 14 additional bits from options extend the field to 30 bits, enabling up to ~1GB of advertised data. The worked example involves computing 2^16 = 65,535 and recognizing the limitation of 16 bits for modern high-bandwidth links. The transition from basic definition to extension via options highlights a practical TCP design consideration.

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