go-back-n-arq-protocol

In this lab experiment, you are required to design and develop a sender function (primary.c) to implement the GoBack-N ARQ protocol, with a Primary function (which will act as a client or sender) while the Secondary function (which will act as a server or receiver) is given to you. This Go-Back-N ARQ protocol is a revised version from the one we learned in class. One difference is that it uses both ACK and NAK packets; this is to simplify the implementation and avoid having to implement the timeout mechanism.

Primary Function:

• Send the alphabet, ABCDEFGHIJKLMNOPQRSTUVWXYZ, to the Secondary in a total of 13 packets (2 characters per packet, NOTE: the total number of packets sent may be higher since the packets may be corrupted by IntroduceError() and thus need to be redelivered).
• Use function “buildPacket” that found in “utilities.c” to build a packet of the following format:

Packet Type	Packet Number	Data	CRC
1 byte	1 byte	2 bytes	2 bytes

• Packet Type
  • 1: Data Packet(sent from Primary to Secondary)
  • 2: Acknowledgement Packet (ACK) (sent from Secondary to Primary)
  • 3: Negative Acknowledgment Packet (NAK) (sent from Secondary to Primary)
• Packet Number
  • Starts from 0 and increments sequentially to 12
• Data
  • Two alphabet characters (sent from Primary to Secondary)
  • No data is sent from Secondary to Primary
• CRC
  • CRC generated for this entire packet, including Packet Type, Packet Number, and Data fields
• Display the packet. (printPacket(.))
• Apply the “IntroduceError(., .)” routine to the entire packet. Pass the BER value to the program as an argument in the command line.
• Implement the Go-Back-N ARQ protocol with a send window of size N = 3

Secondary Function:

• Accept packers from the Primary
• Run the CRC check
  • If the packet is received error free and in sequence, it displays the packet content and sequence number, then sends back an ACK.
  • If the packet is received error free but out of sequence, it does not display the packet content but displays the sequence number, then sends back an ACK.
  • If the packet is received in error, it does not display the packet content but displays the sequence number if possible, then sends back a NAK.