Beginner questions about soundmodem and others

Beginner questions about soundmodem and others

[James Washer]

Perhaps I should have put these all in seperate mails... but here goes

1)I'm confused by this whole AX.25 kernel thing... I had assumed that (most) TNCs handled the AX.25 protocol themselves.
I understand that with a soundmodem, the linux system would have to do the AX.25, but what about if I use an off-the-shelf TNC ( kpc3 for example ). Does linux arrange to turn the AX.25 handling OFF in the TNC and do it in software?

2) Can I put more than one sound card in my linux box.. One for music, the other, perhaps multiple soundcards, for packet?

3) Anyone on this mailing list anywhere near Reno NV... I'd love to have someone local to work with to get started.


thanks
 - jim kg7hh

Re: Beginner questions about soundmodem and others

[mvw]

james

I can answer one of your questions:

> 1)I'm confused by this whole AX.25 kernel thing... I had assumed that
> (most) TNCs handled the AX.25 protocol themselves. I understand that
> with a soundmodem, the linux system would have to do the AX.25, but what
> about if I use an off-the-shelf TNC ( kpc3 for example ). Does linux
> arrange to turn the AX.25 handling OFF in the TNC and do it in software?

Yes. The TNC is put into "KISS" ('Keep It Simple St...') mode, and becomes 
a dumb bitmodem, in affect. The kernel then handles everything. The gives 
you much more control, of course - otherwise you could not have your PC 
directing (and driected by) ax25.

Alternately, you could use a TNC and its inbuilt ax.25 plus PBBS, and no 
PC at all except to read messages people leave you. But then you'd miss 
out on all this fun. ;)

Michael VA3MVW

Re: Beginner questions about soundmodem and others

[Tomi Manninen OH2BNS]

On Thu, 9 Jan 2003, James Washer wrote:

> 1)I'm confused by this whole AX.25 kernel thing... I had assumed that
> (most) TNCs handled the AX.25 protocol themselves. I understand that
> with a soundmodem, the linux system would have to do the AX.25, but
> what about if I use an off-the-shelf TNC ( kpc3 for example ). Does
> linux arrange to turn the AX.25 handling OFF in the TNC and do it in
> software?

Yes, typically the TNC is put to a so called KISS mode (6PACK is another
alternative). In KISS mode the TNC only handles modulation and
demodulation, HDLC en/decoding (bit stuffing and framing that is) and
AX.25 CRC checking. Everything else is left to the PC.

This is basically the only sane way to be able to support higher level
protocols on top of AX.25. Also it makes the simple text mode support much
more flexible.

> 2) Can I put more than one sound card in my linux box.. One for music,
> the other, perhaps multiple soundcards, for packet?

Yes.

-- 
Tomi Manninen           Internet:  oh2bns@sral.fi
OH2BNS                  AX.25:     oh2bns@oh2rbi.fin.eu
KP20ME04                Amprnet:   oh2bns@oh2rbi.ampr.org