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Packet Communication
Introduction
Packets: Dividing Messages into Segments
An efficient way to send a message from one place to another is to break the information into small segments, called packets or frames, and send each packet
separately.
Note: The correct technical term is “data frame”, not “packet” or “frame,” but we
will use the term “packet,” since that is familiar to most people and is common in
the field.
Your packet radio station automatically divides your communication
(e.g., a message or file) into small segments (see the PACLEN command for details) and puts each segment into it’s own “packet.”. Each packet includes information used for addressing and error correction.
Unconnected Packets
Packets do not need to be addressed to any particular station. Packets transmitted
without any established connection between sender and receiver are “unconnected” packets. “Unconnected” packets are just sent out without any
back-and-forth coordination with any receiving station. Stations receiving these
packets can check to see if the packets are correct (i.e., the same bit pattern is received as when they were sent), but they cannot request any retransmission of
faulty packets. Nor can they request re-transmission of any packets in a series
that are not received at all. This is because “unconnected” packets do not include
sequence information that could be used to track them in order and also because a
TNC sending or receiving “unconnected” packets is not set up to do any communicating about the success or failure of its packet transmissions.
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Note: Packets sent as “unconnected” are also called UNPROTO (non-protocol),
because the sender expects no response from the receiving station.
Connected Packets
Packet radio communication is often carried out between two stations that are
connected together. “Connected” communication using packet radio assures
transmission with virtually 100% accuracy by having the sender and receiver
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User’s Guide