Project 3 Overview

Wednesday, April 22, 2026

General Concept

  • Layer 5: Add HTTP POST functionality to your server
  • Layer 4: Replace Go-Back-N with Selective Repeat
  • Layer 3: Dynamic Routing
  • Layer 2: Switch: Learning and Forwarding
  • Security: add encryption to HTTP server + client

No Autograder!

  • Develop your report.
  • Graded on completeness, correctness, and clarity.
  • Nice to have the project fully working, but not required.

Use of Generative AI

  • Coding Portion: Standard Restrictions Apply
    • Link must work in private / incognito mode
  • Report Portion: Not Authorized. Write it yourself.

Warning

Use of Generative AI is not authorized for the report portion of the project.

Application Layer: HTTP POST

  • The server should handle POST requests by receiving the data sent by the client and processing it.
  • POST request should result in an update to the resources available to the server.
  • The server should then send an appropriate response back to the client (e.g., confirming the data was received).
  • Next GET request should return the updated content.

Transport Layer: Flow Control

  • Modify SABRE sender to implement Selective Repeat instead of Go-Back-N

  • Run your receiver locally for testing: python receiver.pyc

Network Layer: Dynamic Routing

  • No coding required.
  • Analyze how router class will need to be modified to support topology changes or link-cost changes at runtime.
  • Explain how you would test these changes!

Link Layer: Switch

  • Update switch.py
    • Implement forward_frame() to forward frames appropriately
    • Write your tests in main() to demonstrate that your switch is learning and forwarding frames correctly

Security: Encryption

  • Implement encryption messaging capabilities for your HTTP server and client
  • HTTP Client sends encrypted messages
  • HTTP Server receives encrypted messages and decrypts them before processing
  • Symmetric encryption is sufficient.

Important

Do not use the Fernet algorithm.

Useful Hints

  • Can implement each section separately

    • This means if you screw up one part, you don’t suffer on other parts!

  • Not required to tackle each part in order

    • Layer 5 -> Layer 4 -> Layer 2 -> Security -> Layer 3

  • Every section requires you to describe testing! Plan out how you will test it in advance. It will make your job of coding easier!!!

  • Report is what I am primarily grading. Use code as evidence. Provide screenshots of your code running in the terminal or wireshark captures.