[aprssig] Definition of IGate status messages? ("Station Capabilities")

[John Langner WB2OSZ]

IGate stations often send packets like this:

		<IGATE MSG_CNT=1238 LOC_CNT=0 FILL_CNT=0
		<IGATE,MSG_CNT=1,LOC_CNT=25
	
<IGATE,MSG_CNT=0,LOC_CNT=46,DIR_CNT=13,RF_CNT=49,RFPORT_ID=0,DX=1

What does it all mean?

The APRS Protocol Reference ( http://www.aprs.org/doc/APRS101.PDF ),
section 15, briefly discusses station capabilities

		"MSG_CNT is the number of messages transmitted, and
		LOC_CNT is the number of 'local' stations (those to which
		the IGate will pass messages in the local RF network)."

and gives the example,

		IGATE,MSG_CNT=n,LOC_CNT=n

IGate Design ( http://www.aprs-is.net/IGating.aspx ) barely mentions
<IGATE,MSG_CNT=n,LOC_CNT=n and doesn't describe what it means.

This leaves many questions.  Does "number of messages transmitted" mean only
the APRS "Message" (data type indicator ":") or does it mean any type of
APRS packet?   What are "local" stations?   Anything heard over the radio or
only those we hear directly without going thru a digipeater?  Do we count
stations heard in the last hour?  Last 24 hours?  A year ago?

What are DIR_CNT, RF_CNT, RFPORT_ID, ...?  

Are the counts since the system started up or are they for some interval?

Is any of this defined anywhere?  What other statistics are commonly used?
What new statistics would be useful?