Re: ppp and dialin server

[Hugo Villeneuve <hugo_villeneuve@yahoo.com>]

I also found out that it's all in the little details.

On Sun, Apr 08, 2001 at 11:03:22PM -0700, a hafiz wrote:
> wish i read your email first, when i had the same problem,
> i wasted a whole week trying different ppp configs.
> then it occured to me that the problem is not ppp
> but getty not negotiating the correct modem 'speed'

Todays modems are async devices. They can work with different speed
for the link and for the serial port. And option like link compression
usually means that the throughput on the serial port can be higher
the connection speed.

[Null-modem cable are syncronous, the same speed (and other settings)
must be use at both side of the cable.]

That's why most modem are set to use 115200 serial speed so they
never run short of the link speed (after decompression or not).

But for this to work correctly, you must use RTSCTS hardware flow
control.

"std.115200" doesn't use RTSCTS flow control.

You can do this test with hyperterminal and login in on your server:

# uuencode /bin/ksh ksh

(ctrl-c when you are tired of looking at the output.)

At one point, you'll see the output break and data will being lost.
Now you can see the difference with rtscts by doing:

# stty crtscts
# uuencode /bin/ksh ksh

There will be no break in the output. Every thing will be fine.

So I had to change a little bit my gettytab entry to add rtscts
flow control.

Here's my gettytab entry, with rtscts, timeout after 30 seconds and
ppp detection capabilities:

modem.115200:\
        :sp#115200:to#30:c2#0245400:i2#025402:l2#02713:o2#07:\
        :pp=/usr/local/bin/ppplogin:

[Note: It isn't clear from the gettytab man page that the [cilo]2
capabilities must be all set or they are just ignored.]

This is for the console mode, ppp will set rtscts by default (if I
remember).

> took me another week of frustration and tears to realise i have to
> turn on the ipforwading in the /etc/syscont file to enable ipforwarding.

Yes, you need ip forwarding. And for me, because I use non-public IPs
on the ppp link, I also need to setup ipnat rules and enable IPNAT
and IPFILTER in /etc/rc.conf.


Hugo Villeneuve