[OZAPRS] some comments re the ongoing findu discussion

John Williams vk5zty at bigpond.com
Thu Mar 18 14:24:36 EST 2004


The comments about preserving the digipeat bit or flag on systems that
have already digpeated 
a packet seems the be handled differently by aprs digipeater
implementations or is it the 
application used to monitor these frames.

I don't have the ax25 spec to hand, but the address field does have one
bit reserved to indicate 
if a station has digipeated a packet and I can see no reason once this bit
has been set why it 
would be reset by the next station to receive this packet.  In fact
evidence would suggest that 
the digipeated bit state is maintained or can be maintained and it is
perhaps up to the 
application to check to complete address field and test every address in
the repeater sub field.

Here is an example frame from digi_ned. 

This is the output from the BRC digi monitored on the igate port.

1: fm VK5EX-1 to APNU19 via VK5RNE-1* VK5BRC-7* ctl UI^ pid=F0(Text) len
50
0000  _03191313c331s000g000t077r000p000P000b10170h32uRSW


This frame is montor direct from  BRC box using listen (a linux
application) to view the frames.
1: fm VK5EX-1 to APNU19 via VK5RNE-1* TRACE ctl UI^ pid=F0(Text) len 50
0000  _03191328c200s003g000t080r000p000P000b10170h31uRSW
1: fm VK5EX-1 to APNU19 via VK5RNE-1* VK5RMB-1* ctl UI^ pid=F0(Text) len
50
0000  _03191328c200s003g000t080r000p000P000b10170h31uRSW

The RNE and RMB digis are both uidigi and you can see the the digipeated
bit is seen on both
digis in the last frame.

The position frame for EX-1 is seen on findu as
Raw packet: VK5EX-1>APNU19,VK5RNE-1,VK5BRC-7*,qAO,VK5UJ-
1:=3457.57S\13837.87E_ UIDIGI 1.9 & WM918 (R,WX)

So in this case only the last digi is shown as already discussed. 

Geoff mentioned that the uidigi systems in Sydney on show the last digi
that handled the 
packet
VK2EO>APU16N,TCPIP*,VK2XJG*:!3245.00s/15145.00e- Raymond Terr
Wed Mar 17 21:11:46 2004  VK2XJG>APRS,VK2RSW-1,VK2JPJ-1*,TRACE1-1/1:}

I wonder if this is a case of the application used to monitor the packet
rather than what is really 
happening.

Now regarding messages.

My understanding was that if a station from outside your filtered feed
sent you a message that 
their position would be sent and away you went.    Did the servers run
something other than 
javAPRSsrvr originally.   I think aprsd worked in this fashion.

Aprs email servers aside, most people would only think of messaging a
station that appeared 
on their map. So messaging within VK should work all the time for stations
connected to an 
igate and possibly on RF also depending on the igates RF out going path.

What is involved in setting up an aprs email server. May be one could be
run within VK.
If the available software is able to run on a linux box. I could look at
running it on our gate or 
perhaps Geoff could run it at the national server. 

Problem solved in that case.

Cheers
John
  


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