Re: RF modem PPP support



On 5 Oct 2006, in the Usenet newsgroup comp.os.linux.hardware, in article
<1160034451.344833.315650@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, Eduardo Marques wrote:

Can anyone point me to information on setting up PPP for RF modems
(radio-frequency spread spectrum modems), or any other protocols for
enabling TCP/IP over RF modems.

1598 PPP in X.25. W. Simpson. March 1994. (Format: TXT=13835 bytes)
(Status: PROPOSED STANDARD)

That's RFC1598, which should be easy to find on the net. Now, if you
are talking about using ANU ppp (ftp://ftp.samba.org/pub/ppp/) that is
the standard application used in nearly all Linux distributions, you
may want to ask in the newsgroup 'comp.protocols.ppp' but you need to
supply a LOT more details.

The short version - ANU ppp requires an 8 bit clean link in both
directions with _relatively_ low latency. The link should look
like a serial port - hardware flow control would be nice, but you can
use software (XON/XOFF) flow control. The link has to be run at one
of the following _port_ speeds: 134, 150, 200, 300, 600, 1200, 1800, 2000,
2400, 3600, 4800, 7200, 9600, 19200, 38400, 57600, 115200, 230400 and
460800 bits per second (set in pppd/sys-linux.c based on values set in
/usr/include/termbits.h). Most radio modems I'm aware of do not have
the complex modulation schemes needed for speeds over 2400 BPS - you'll
want to check that. At those top-end speeds, check the specifications
of the serial interface - not many handle the 230.4 or 460.8 kilobit
speeds.

You may also want to look at two HOWTOs:

* AX25-HOWTO, Linux Amateur Radio AX.25 HOWTO
Updated: Sep 2001. How to install and configure support for the AX. 25
packet radio protocol utilized by Amateur Radio Operators worldwide.

* Netrom-Node, Netrom-Node mini-Howto
Updated: Oct 1998. How to setup the ax25-utilities package for Amateur
Radio such that it makes Netrom Nodes for the Node program and the BBS
software from John-Paul Roubelat, F6FBB.

-rw-rw-r-- 1 gferg ldp 219433 Sep 20 2001 AX25-HOWTO
-rw-rw-r-- 1 gferg ldp 10842 Apr 26 2001 Netrom-Node

Old guy
.



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