[aprssig] are write-only APRS-IS clients valid?

Pete Loveall AE5PL Lists hamlists at ametx.com
Mon Dec 2 14:14:14 CST 2013


> -----Original Message-----
> From: Tom Hayward
> Sent: Monday, December 02, 2013 11:36 AM
> 
> The ambiguities in Pete's algorithm that you can see plainly in mine are:
> 1) Can a source be in more than one igate's heard list at a time? If
> yes, I don't think receive only igates will break 2-way messages. The
> other igate can still serve the area just fine, assuming there is at
> least one 2-way igate in the area.

Yes but your interpolation is incorrect.  Your assumption is that every server sees all packets and, as I have repeatedly stated, this is not always the case (and many times isn't the case on purpose).

> 2) Are stations added to the heard list before dupe filtering? If yes,
> both 2-way and rx-only gates can be connected to the same server
> without interfering with each other's heard lists.

Yes, in that specific configuration, it is ok.  But that is one configuration out of many and I have delineated where this assumption is invalid.

> 3) What is xx_minutes? How long do packets stay in each igate's heard list?

This is somewhat immaterial because it is implementation dependent.  javAPRSSrvr maintains a 1 hour recently heard list for each client (I think, it may be shorter) as that was generally agreed upon many years ago when we first addressed this issue of limited feed ports.  Other servers such as aprsc may use a different number.  Bottom line is a message addressed to a station heard in the relatively short past on RF should be gated to that station by the IGate and the server makes that message packet available to the client.  The other piece here is it is not up to the server to determine what gets gated to RF; it only determines to deliver the packet to the client so the client/IGate can make the determination if it wants to gate it to RF.  The IGate sysop fully controls their station; the server only ensures that proper messaging support is delivered to said IGate.

73,

Pete Loveall AE5PL
pete at ae5pl dot net




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