Editing AppleTalk (section)

=== AppleTalk Data Stream Protocol ===
The AppleTalk Data Stream Protocol (ADSP) was a comparatively late addition to the AppleTalk protocol suite, done when it became clear that a [[Transmission Control Protocol|TCP]]-style reliable connection-oriented transport was needed. Significant differences from TCP were that:
* A connection attempt could be rejected.
* There were no "half-open" connections; once one end initiated a tear-down of the connection, the whole connection would be closed (''i.e.'', ADSP is [[duplex (telecommunications)|full-duplex]], not [[dual simplex]]).
* AppleTalk had an included attention message system which allowed short messages to be sent which would bypass the normal stream data flow. These were delivered reliably but out of order with respect to the stream. Any attention message would be delivered as soon as possible instead of waiting for the current stream byte sequence point to become current.{{sfn|Sidhu|Andrews|Oppenheimer|1989|p=12-19}}