On Jun 23,  3:09pm, David Kelly wrote:
} Subject: Re: Sun 3/50 Ham Radio.
} "=?ISO-8859-1?Q?H=E5kan Th=F6rngren?=" writes:
} > >>>>> "David" == David Kelly <dkelly@hiwaay.net> writes:
} > 
} > David> needed then use the kernel's SL/IP, PPP, or BPF interface. Direct 
} > David> access to the 8530 serial port would be nice as then one could use a 
} > David> BayCom-ish radio modem without bit-banging the protocol.
} > 
} > I am no kernel expert in any way, but I think it would be nice to have
} > it in the kernel.  I would like to use it together with TCP/IP, can
} > that be done without having it inside the kernel?

     It can, but it hurts general system performance since you need to
move each packet between kernel and userland several times, which
necessitates multiple context switches per packet.

} How much does it hurt for pppd(8) or ppp(8) to be outside the kernel?

     ppp(4) is inside the kernel.  pppd(8)'s job is to dial the modem,
login,  and setup the connection.  Once the connection is established,
ppp(4) in the kernel takes over and handles the actual data transfer.

} > You should also
} > consider that many machines that run NetBSD are old and slow.  AX25
} > in itself is not slow, it depends on the communication hardware being
} > used.
} 
} 1200 bps is the definitive interface. 9600 can still be purchased out 

     Irregardless, you still don't want the system wasting time on
needless overhead.  Not everybody uses lightning fast machines.  Come
to think of it, this port-sun3, which means the machines we are talking
about aren't exactly modern speed demons.

} A major problem with using kernel TCP/IP stacks is the very long delays 
} which are typical of AX.25 RF links.

    So?  If there are problems, then the stack should be tuned.  TCP/IP
was designed to work over all sorts of links.

} Interesting that the entire 44.x.x.x net is ampr.org.

     Probably an artifact of history.  That net has been around for a
long time and dates back to the early days of the general Internet,
when it was still mainly educational institutions and the US military.
Back then, it wasn't nearly as hard as it is now to get a "Class A"
address.  Although, given that it is a worldwide semi-public network,
they just might qualify by today's rules.

} Routing is quite another issue.

     Why?  Routing is well establish.

}-- End of excerpt from David Kelly