Subject: Re: What's "different" about NetBSD slip/ppp?
To: Thor Lancelot Simon <>
From: Michael L. VanLoon -- <>
List: current-users
Date: 12/07/1994 11:42:47
>My NetBSD machine has no problems doing SLIP or PPP with plenty of other
>terminal servers, including other Xylogics Annexes configured damn' near the
>same right down to the IP addresses on both ends of the link.  The Annex I 
>*can't* connect to has no trouble connecting to anything _else_.  It's not
>a routing problem; trying to get things going immediately after a "route flush
>with either a default route added by hand or with the pppd defaultroute option
>doesn't work -- though this works fine with other Annexes, as I said above.
>It really really looks like some kind of weird protocol incompatibility.  I

I've noticed something similar.  We use Xyplex terminal servers at
Iowa State.  One of the head Telecommm engineers and I spent a good
half hour with a sniffer one day trying to figure out why the Xyplex
cards would reboot every time we tried to telnet to them from a NetBSD
box (each card has eight ports and its own CPU).

We ended up capturing a packet and playing it back, both modified and
unmodified to see the results.  It turns out that the Xyplex couldn't
handle the new timestamp TCP option field in the TCP packet.
Sometimes it would reboot the Xyplex card being telnetted to, and
sometimes it would "just work".  My theory is that it threw away the
TCP option and choked on the following bytes (the time-stamp data).
Depending on what the actual data was in the time-stamp field, it
either ignored it, or crashed the card.  The sniffer didn't know what
the time-stamp field was supposed to be, and obviously, neither did
the Xyplex.

This happened on our older Xyplex 5000 boxes.  The newer 9000 doesn't
exhibit this behaviour.  Dan (the telecomm engineer) is working on
getting new software for the 5000 from Xyplex.

This might be related to your problem.

   Michael L. VanLoon
  Free your mind and your machine -- NetBSD free un*x for PC/Mac/Amiga/etc.
     Working NetBSD ports: 386+PC, Mac, Amiga, HP300, Sun3, Sun4c, PC532
               In progress: DEC pmax (MIPS R2k/3k), VAX, Sun4m