UNIVERSITY OF WEST ATTICA
SCHOOL OF ENGINEERING
DEPARTMENT OF COMPUTER ENGINEERING AND INFORMATICS

University of West Attica · Department of Computer Engineering and Informatics

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Computer Networks II

TCP

Vasileios Evangelos Athanasiou
Student ID: 19390005

GitHub · LinkedIn

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Supervision

Supervisor: Adonis Bogris, Professor

UNIWA Profile · LinkedIn

Co-supervisor: Rania Garofalaki, Laboratory Teaching Staff

UNIWA Profile · LinkedIn

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Athens, June 2022

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README

TCP

The project involves a technical examination of TCP behavior through a series of structured questions based on a real network trace.
The analysis focuses on the TCP three-way handshake and the subsequent data transfer phase between a client PC and a web server.

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Table of Contents

Section	Folder / File	Description
1	assign/	Assignment material
1.1	assign/Askisi6_TCP.pdf	Assignment description in English
1.2	assign/Άσκηση6_TCP.pdf	Assignment description in Greek
2	docs/	Project documentation
2.1	docs/Transmission_Protocol_System.pdf	TCP protocol analysis and operation (English)
2.2	docs/Σύστημα_Πρωτοκόλλου_Μετάδοσης.pdf	TCP protocol analysis and operation (Greek)
3	README.md	Repository overview and usage instructions

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1. Network Entities

• Client PC

  • IP Address: 192.168.1.102
  • TCP Port: 1161

• Server

  • IP Address: 128.119.245.12
  • Hostname: gaia.cd.umass.edu
  • TCP Port: 80

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2. Key Analysis Components

2.1 TCP Three-Way Handshake

The report identifies and analyzes the three TCP segments used to establish a reliable connection:

• SYN Segment
  Initiated by the client with a relative Sequence Number = 0.
  The SYN flag is set, indicating a request to establish a connection.

• SYN–ACK Segment
  Sent by the server in response to the client’s SYN.

  • Sequence Number: 0
  • Acknowledgment Number: 1 (calculated as 0 + 1, acknowledging the client’s SYN)

• ACK Segment
  The final segment of the handshake, where the client acknowledges the server’s SYN–ACK and completes the connection setup.

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3. Protocol Details

• TCP Flags
  Detailed analysis of flags such as SYN, ACK, PSH, and others to determine the role and purpose of each segment.

• Sequence Management
  Tracking of both relative and raw sequence numbers throughout the TCP session to understand data ordering and reliability.

• HTTP Integration
  Identification of an HTTP POST command encapsulated within the TCP stream.
  The POST request appears in the 4th TCP segment with a sequence number of 1, demonstrating the interaction between the transport and application layers.

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4. Document Structure

• Question 1
  Analysis of the initial connection request (SYN segment).

• Question 2
  Examination of the server’s response (SYN–ACK) and the acknowledgment mechanism.

• Question 3
  Identification of specific application-layer commands (HTTP POST) within transport-layer TCP segments.

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5. Conclusion

This laboratory analysis provides a clear and structured understanding of how TCP establishes reliable connections and transports application-layer data.
By examining real packet traces, the report highlights the interaction between TCP mechanisms and HTTP communication, reinforcing key concepts of transport-layer networking.