Congestion Window

Duration: 3 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:
  18. HPSC PGT - MOCK Test Series:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The lecture introduces TCP flow control and congestion control by explaining the two windows used in each direction of data transfer: the send window and the receive window. The instructor, wearing a black "KG KNOWLEDGE" polo shirt, presents slides titled "Windows in TCP" and "Congestion Window." The core teaching point is that the sender window size is determined by two factors: the receiver window size and the congestion window size. A hand-drawn diagram with nodes labeled S, N, and R is annotated step by step to illustrate the data flow between sender, network, and receiver. The instructor emphasizes that a sender must not send data greater than the congestion window size to avoid dropping TCP segments and causing retransmissions. The key formula presented is: Sender window size = Minimum (Receiver window size, Congestion window size). The congestion window is known only to the sender and is not sent over the links, with different TCP variants using different approaches to calculate its size.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The slide headed "Windows in TCP" states that "TCP uses two windows (send window and receive window) for each direction of data transfer." Under the "Send Window" heading, the slide lists "Receiver window size and Congestion window size," both underlined in red. A hand-drawn diagram below uses red circles labeled N and R, green and blue arrows, and handwritten labels such as "3.5KB," "16 KB," and "14B." At 45s, the slide briefly shows a "Receive Window" section with red underlines and a small red arrow on lines about not exceeding the receiver window size. From 55s, the slide returns to "Windows in TCP," and the diagram gains S, R, and N nodes joined by arrows, where the R boxes are circled and crossed out in red. The instructor shifts his gaze between the camera and the slide while annotating the diagram step by step.

  2. 2:00 – 3:24 02:00-03:24

    The focus shifts to the "Congestion Window" slide. The instructor explains that a sender should not send data greater than the congestion window size, otherwise it leads to dropping TCP segments which causes TCP retransmission. The text on screen states: "So, sender should always send data less than or equal to congestion window size." It also notes that different variants of TCP use different approaches to calculate the size of the congestion window, and that the congestion window is known only to the sender and is not sent over the links. A formula is shown with a red arrow pointing to the word "Minimum": "In general, Sender window size = Minimum (Receiver window size, Congestion window size)." Red underlines emphasize key terms like "congestion window size," "TCP segments," and "TCP Retransmission."

The lecture builds a clear progression from the general concept of TCP windows to the specific rule governing sender behavior. First, it establishes that TCP uses two windows per direction: send and receive. Then it identifies the two determinants of the sender window size: receiver window size (flow control) and congestion window size (congestion control). The hand-drawn diagram with S, N, and R nodes visually anchors the sender-network-receiver relationship. The critical takeaway is the formula: Sender window size = Minimum (Receiver window size, Congestion window size). The instructor stresses that exceeding the congestion window causes segment drops and retransmissions, so senders must always stay at or below that limit. The congestion window is sender-local and not transmitted over the network, with calculation methods varying by TCP variant. This distinction between flow control (receiver-driven) and congestion control (sender-driven, network-aware) is the central pedagogical goal.

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