ISDN modem problems

[chl@tbit.dk (Christian Lynbech on satellite)]

I have just got myself an ISDN line and a Zyxel Omni.net plus modem,
but I have problems in getting it to work smoothly.

The problem is that I keep getting error messages saying something to
the effect of:

    ppp: frame with bad fcs, excess = 4de9

The more trafic (for instance with ping) I generate, the less packages
comes through. The limit seems to be around packet sizes of 2048/4096.

If I stress my machine (which is a pentium 75 with 48Mb of RAM, a
couple of years old), more packages are dropped.

If my machine is only lightly loaded, pppd will only come up if I use
the option:

    kdebug 7

Otherwise it fails rather eraly in the initial negotiations when a
ConfReq never sees the corresponding ConfAck.

However, if I run a heavy job (such as a kernel compilation), the
kdebug is not necessary to get pppd up. It will drop a few packages
with ping -s 4096, but now silently. With ping -s 8192, almost nothing
gets through.

If I run X11, the connection can not get up (with kdebug 7).

Does anybody have an idea where and how I should investigate? Should I
suspect my serial port? Is my machine simply too slow to handle a
64kps connection? Is there any kernel option I can set?


---------------------------+--------------------------------------------------
Christian Lynbech          | Telebit Communications A/S                       
                           | Fabrikvej 11, DK-8260 Viby J                 
Phone: +45 8628 8176       | email: chl@tbit.dk --- URL: http://www.tbit.dk
---------------------------+--------------------------------------------------
Hit the philistines three times over the head with the Elisp reference manual.
                                        - petonic@hal.com (Michael A. Petonic)




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