[aprssig] Question about 'H-bit' handling and WIDEn-N paths

[AE5PL Lists]

Good question.  Dupe check for APRS should be based on callsign-SSID,
unproto (no SSID), and the I-field.  The via path should be ignored as
this changes with digipeating (as you noted).  The SSID on the unproto
is ignored because this could be changed SSID routing.  The unproto
should be part of the CRC because it is used as data in APRS (Mic-E, for
example).

73,

Pete Loveall AE5PL 

> -----Original Message-----
> From: James Washer
> Posted At: Friday, January 28, 2005 10:19 AM
> Subject: Re: [aprssig] Question about 'H-bit' handling and 
> WIDEn-N paths
> 
> Ok.. you bring up another interesting question. You say that 
> by keeping a history of 30seconds worth of CRC's we can avoid 
> sending dupes, but setting the H-bit OR decrementing 
> WIDEn-N/TRACEn-N will change the CRC. So what are they doing? 
> Calculating a special CRC on the payload or something?