Application Protocol Data Unit
<networking> (APDU) A {packet} of data exchanged between two
{application} programs across a {network}. This is the
highest level view of communication in the {OSI} {seven layer
model} and a single packet exchanged at this level may
actually be transmitted as several packets at a lower layer as
well as having extra information (headers) added for {routing}
etc.
(1995-12-19)