[Xastir] Smart RELAY digipeating

[Bob Nielsen]

On Wed, Jan 05, 2005 at 09:14:54AM -0800, BDonnell at ar-northwest.com wrote:
> 
> 
> > -----Original Message-----
> > From: Wes Johnston [mailto:wes at kd4rdb.com]
> > Sent: Wednesday, January 05, 2005 4:30 AM
> > To: Bob Donnell
> > Cc: archer at eskimo.com; oh2kku at iki.fi; xastir at xastir.org
> > Subject: RE: [Xastir] Smart RELAY digipeating
> > 
> > 
> > Ummm.... I've been watching this thread and think the idea is 
> > to not digipeat
> > RELAY by a home station if you have already heard the same 
> > packet digipeated by
> > the local WIDE.  That's a great idea.  So your station sits 
> > on the packet for 3
> > to 5 seconds before digipeating.
> > 
> > In the past few days is where I've gotten confused.  There 
> > seems to be talk
> > about KISS tncs delaying the delivery of a packet to the 
> > network.  If what I've
> > seen is correct, it is being said that the kiss tnc can cause 
> > the delay.  Yes,
> > it can, but if the packet is heard digipeated from the WIDE, 
> > that KISS mode tnc
> > isn't going to care... it's got "data" in queue and is just 
> > waiting for access
> > to the channel.
> > 
> > The trick to make this work _correctly_ is to use 6-pack 
> > TNCs.  They communicate
> > the busy/clear status back to the host computer.  Unlike KISS 
> > tncs, you can't
> > queue a packet in the tnc for minutes at a time... the host 
> > must watch for the
> > channel to be free, and as soon as it is, the host must start 
> > sending data
> > forcing the TNC on air.  This of course moves the host 
> > computer one step closer
> > to the radio and allows us to abort digipeating a relay packet.
> > 
> > Sure is a shame that KISS tnc's don't communicate the CD led 
> > status via one of
> > the rs232 handshake lines.
> 

>From the old (I don't have a date, but it is pre-1990) Mike 
Chepponis/Phil Karn paper on KISS:

"It should be stressed that the KISS TNC is intended only as stopgap."

> I think SOME TNC's can be configured to communicate the status of the
> CD line.  However you still have the delays imposed by transferring
> the entire packet to the computer (and that has to be allowed for) and
> transferring the entire packet from the computer back to the TNC.  If
> the RS-232 data rate is fast, say 19200 baud or faster, the delay is
> pretty small, but still present. 
> 
> If the duplex state of the TNC isn't modified, or alternatively, the
> p-persistence, to make the TNC very aggressive, then the TNC can still
> add in significant delay.
> 
> Curt and I had an off-list discussion some time ago (a year?) about
> adding 6-pack into xastir, for this very reason. 

Would it be as simple as using the kernel 6pack.ko module with AX.25 
networking set up?

Bob, N7XY