ECE 544 Project 2: ARQ Scheme Design

Introduction

As part of project 2 you are required to design a protocol to transport a file from one end of a communication link to the other end over an unreliable link. The host which has the file is the "sender". The other host is the "receiver". Both directions of the link are lossy.
As the link is not perfect, you have to design an ARQ scheme to overcome possible packet loss. Stop-and-Wait, Go-back N, selective ACK, Sliding window..., using ACK or NACK?. It's all up to you. Any working link control scheme is acceptable.
However, to encourage you to design scheme with better performance, the designer of the program which spends least time to transport the given file (a 100KB-size file ) through the link will get extra credits.

Requirements:

The file must be transferred from sender to receiver without any distortion/damage. In a word, the content of the file in receiver side must be exactly as same as the original file. The file shall not be compressed before transmission.
Before the transfer of the file, the name of the file has to be sent to the receiver in a packet ahead.
You must design a packet header to carry some signaling information. It should at least includes

the sender's own identification/name (you could use characters or numbers)
message type (DATA, ACK, NACK....)
sequence number.

The packet header cannot exceed 256 bytes
Each packet's size (including header) cannot exceed 1,466 bytes. (Can you guess why? Include your answer in your project report.)
The filename of the transferred file cannot be hard-coded in your program. You must put the filename as a command-line argument of the sender program. Also, the receiver need to store the file in a name. This name shall be a command line argument of the receiver program, too.
When the transfer finishes, at least one of the two programs shall exit gracefully (not hanging).

Where to start

In the package you downloaded, you will find text2.dat. This is the file you need to transfer.
In src/ directory, there are two files: common.h and common.cpp, which provide some basic classes and functions. The documentation of them could be found in doc/ directory.

Please refer to the examples to learn how to use it.

Then, check newport.h to see how a child class is derived from the SendingPort class.

How to Test

If running the program only using the two application clients, setup the the used ports with the following characteristics:

The packet over the link is either lost or received completely.
Loss probability is 0.2.
No partial information is heard and no needs for a CRC check.

I suggest you test your own program and fix any errors before submission.
You can use the provided virtual machine to test your program. Run each program in a separate console. The sender need send to "localhost" (the destination address of the sending port). The receiver also needs to send to "localhost" if it sends back some feedback signaling.

Use "diff" command to see if the received file is as same as the original file.

Tips

There is one timer associated with each sending port. If you think your protocol programming need more timers, you can design a new class like SendingPort class, with more timers. Please place your design in a separate file. Then derive your working class from that class.
If you want to combine the functions of a sending port and a receiving port in a new class, e.g. "new_port", and use it in both sender and receiver side, go ahead to design it in a separate file.
You may wonder why the sender and receiver have different protocols(programs). They need not to be different and shall be same. But as we mixed application (a uni-directional file transfer) with a link layer protocol in a same C++ program, it turns out to be two different ones.
Use gdb for debugging purpose. If you use the "Makefile" I give, the compilation use -g option to enable gdb debugging by default.
Do not remove "-lpthread" part of the Makefile, it is mandatory when Linux threads are used.
The 256 byte for packet header size is only an upper bound. You can choose what any small number you want for header size. The PacketHdr class does not hard code any format. You can use its API to design your format.
To tar files under a specific directory into a file, use " tar -cvf project1.tar project1/"