Reliable Data Transfer Protocol Implementation

A network simulation project implementing a reliable data transfer protocol using OMNeT++ framework. The implementation includes selective repeat ARQ with sliding window mechanism for error control and flow control.

Features

• Selective Repeat ARQ protocol implementation
• Sliding window mechanism
• Error simulation including:
  • Message modification
  • Message loss
  • Message duplication
  • Message delay
• ACK/NACK control frames
• Timeout-based retransmission
• Frame checksum verification
• Byte stuffing for frame delimiting

Project Structure

• src/ - Source code files

  • node.{h,cc} - Node implementation for sender/receiver
  • coordinator.{h,cc} - Coordinator module for simulation control
  • CustomMessage.msg - Message definition
  • utilities.{h,cc} - Helper functions
  • Logger.{h,cc} - Logging functionality
  • ErroredMsg.{h,cc} - Error simulation

• simulations/ - Simulation configuration

  • omnetpp.ini - Main configuration file
  • package.ned - Network definition

• inputs/ - Test input files

Configuration Parameters

The following parameters can be configured in omnetpp.ini:

• WS - Window size (default: 3)
• TO - Timeout duration (default: 10.0)
• PT - Processing time (default: 0.5)
• TD - Transmission delay (default: 1.0)
• ED - Extra delay for delayed messages (default: 5.0)
• DD - Duplication delay (default: 0.1)
• LP - Loss probability (default: 0.3)

Building and Running

1. Install OMNeT++ 6.0 or later
2. Build the project:

make

3. Run simulation:

./simulations/run

Error Codes

Messages in input files use 4-bit error codes in the format:

[Modification, Loss, Duplication, Delay]

For example:

• 1000 - Message modification only
• 0011 - Message duplication and delay
• 0100 - Message loss only

Test Cases

The project includes various test scenarios in the tests.txt file covering:

• Simple timeouts
• NACK retransmissions
• Different error combinations
• ACK/NACK loss scenarios
• Window sliding behavior