> It really really looks like some kind of weird protocol incompatibility.  I
> have no idea if it's NetBSD's fault or Xylogics' fault; all I know is that the
> NetBSD machine sends stuff, and gets nothing back.  (As the modem lights are my
> witness. :-)  Next step, I guess, is to upgrade the Annexes to _yet_another_
                                                                 ^^^^^^^^^^^^^
> unofficial_Xylogics_patch_release, and call Xylogics tech support and get them
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> in on the act.
> 
> Still, if this Annex can talk to anything _but_ my NetBSD machine, it seems 
> likely that there's something different about what the NetBSD machine's sending
> it.  So I'll ask again:  What's "different" about NetBSD slip/ppp?

When clark.net was my Internet provider, they had a round of these 'unoffical'
patches to get PPP/SLIP to work for various people.  I really don't know
all the details, but you can contact the admin at jamie@clark.net.  This 
problem sounds suspiciously familar...