Identifying streams more precisely

Two issues were raised about the use of the words "existing" and "current" to refer to streams.  These were a little squishy, so I tightened the language a little.  The text no longer uses either word to refer to streams, instead using stream states to describe where the relevant text applies and favouring "identified" as a fallback.
So as you note below, these are the only states in which the setting has any real meaning (you can't send DATA in any other state).  I'd be happy to drop the mention of states though.  I was only trying to be helpful.