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

Steve Dimse steve at dimse.com
Tue Jun 28 12:51:24 EDT 2016

> On Jun 28, 2016, at 9:26 AM, Lynn W. Deffenbaugh (Mr) via aprssig <aprssig at tapr.org> wrote:
> On 6/28/2016 9:00 AM, John Langner WB2OSZ via aprssig wrote:
>> 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?
> For APRSISCE/32 I count only the APRS Message packets for MSG_CNT. And only those gated from the APRS-IS to RF for local stations since it is afterall an IGate status packet.

That is the original intent, a count of the messages sent to RF from the internet. In the early days we used it as a way to see if an IGate was sending packets, look at the IGate message count before and after an attempt to reach an RF station. Now there is so much activity that is not reliable for that purpose. It also helped with the first APRServ hub, if the station count dropped to zero I knew I had a radio problem and had to head to the Miami Museum of Science.
>> What are "local" stations?  Anything heard over the radio or
>> only those we hear directly without going thru a digipeater?
> For APRSISCE/32, "Local" is defined as those stations to which messages would be gated if any are received from the APRS-IS.  This currently means unique stations heard within the past 30 minutes with at most two used path hops.

The number of hops defining local should match the number of hops of the outgoing packets from the IGate. So if the path is only WIDE, then local should only be stations heard direct or through one hop. From the beginning I was very much against on a standardization of the outgoing IGate path, hams should be free to manage their local RF network in a way that works for them. Busy areas one hop may be best, I lived in an area where three was a much better choice. I avoided as much as possible prescribing anything that might change between locations.
>> Do we count
>> stations heard in the last hour?  Last 24 hours?  A year ago?
> This was completely unspecified as far as I could tell, so APRSISCE/32 simply counts them per activation.  If the IGate is restarted, the counts start over at zero.

The intent was how many stations are there for which messages could be IGated. IGate software keeps an internal list of the 'local' stations so it knows when to IGate a message, and this number should be the length of that list. Some IGates have a parameter for local timeout, 1 hour was the original default, so if in an hour the IGate has not heard another local packet the station is dropped from the local list. Messages will no longer be IGated to that station and the station count would drop by one. The number should not just continue to rise.

>> Are the counts since the system started up or are they for some interval?
> APRSISCE/32 starts counting at zero for each execution of the program.  Of course the DIR/LOC/RF_CNTs are instantaneous at the time of transmission.

As originally implemented the message count was since startup, but the station count was always moving up and down.
>> Is any of this defined anywhere?  What other statistics are commonly used?
>> What new statistics would be useful?
> Not that I know of!
I can't seem to find it on my computer but I think this was in the DCC presentation that announced two-way APRS messaging via the internet, 1998 if I remember correctly, or perhaps the following year. Many brain cells have died since then and the memory is unclear!

It is good an IGate sends the message as it makes it clear the IGate is two way (the message should not be sent by one-way IGates, or at least the station count should always be zero), but other than the occasional debugging by IGate operators the numbers aren't globally valuable. And for this reason there is not any problem with altering the meaning of the original intents or adding more fields.

findU keeps a list of IGates sending those messages here for whatever use it is


Steve K4HG

More information about the aprssig mailing list