[aprssig] Aprx v2 beta, now with Viscous Digipeater

Scott Miller scott at opentrac.org
Thu Oct 22 12:38:49 EDT 2009

> I was thinking more of the buffer for the packets being held for
> delayed digipeating.  Matti's web page refers to a "4-8 second" hold,
> which sounds reasonable in operation, but that means a worst case of
> up to eight 256 byte packets, or 2k RAM.  Even a minimum 4s hold is 1k
> of buffer space.  This is all in addition to the dupe hash table.

Yes, but in the T2 the buffer space (not a full 2K) is already there. 
Certainly a 4-8 second hold (I think 3 or 4 seconds ought to do it) is 
going to put a lot more load on the buffer.  But it can immediately drop 
anything that isn't eligible for digipeating, and it can drop packets 
that it hears as dupes.

The biggest problem that's going to cause for the T2 is buffer 
fragmentation.  It's a circular buffer and it can only delete from 
either end - it can't reuse space from the middle of the buffer until 
one end or the other shrinks down.


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