Minipac

Minipac is a client-server protocol designed to be used with low-bandwidth packet radio.

Features:

• Compression

• Error detection

• Efficient packet resending

• Packet acknowledgement

Data Transfer

Here's roughly how a data transfer works:

• Node A sends a DataStart packet, indicating the number of packets that will be sent(not including this one) as well as the first chunk of data.
• Node B sends a DataStartAck packet, acknowledging the request. If Node A doesn't hear this, it will resend the DataStart packet several times before aborting.
• Node A sends all remaining packets in quick succession.
• Node B sends a list of packet ids to Node A. These are the packet ids is it missing(lost in transit, or checksum didn't match). If Node A doesn't hear this, it will resend the last packet.
• Node A resends the required packets, as well as a packet with the max ID to signify that it is done.
• This repeats several times until all packets have been received and decoded properly.
• Node B sends a DataResend packet, but with no ids. This tells Node A that it has received everything successfully.
• The data has been transferred.

Unlike with AX.25 or AX.26, there are no constant back-and-forths, greatly speeding up the maximum transfer rate.