Solving Disconnect Problems

A disconnect is simply a broken connection. In LANtastic, when
your computer loses its connection to the rest of the network, you
get an error message like "Server connection to network node ????
broken".  There are quite a few situations in which you might
expect to be disconnected -- for example, if the node you were
connected to has been turned off. Intermittent, apparently random
disconnects however, can be symptoms of a hidden network
configuration problem. This bulletin presents a discussion of the
most common causes of intermittent disconnects and presents some
possible solutions. 

Unique Node Addresses

To ensure that network data gets to its proper destination, the
network has to have a way to tell the computers that are hooked to
it apart.  LANtastic does this by assigning a unique node address
to each station. While many LAN adapters require you to manually
set this number with switches, Artisoft's 2mbps adapter boards
running LANBIOS or LANBIOS2 can, in most cases, pick a random
nonconflicting number automatically.

Sometimes, especially when there are many stations being started
at about the same time or when the network is nearing its maximum
cable length, the automatic process can be fooled into giving the
same number to more than one station.  If this occurs, the
stations that have the same number may periodically lose their
network connection. 

This problem is easy to detect and correct. Run LANCHECK,
Artisoft's network diagnostic program, on all your stations. If
the same adapter number (the A# field in the LANCHECK display)
shows up more than once, you can fix the problem by manually
assigning a unique number to each of your adapters. You can do
this from the LANBIOS or LANBIOS2 command line with the NODE=
command line switch. The number that you specify must be from 0001
to FFFE (hexadecimal). Note that NODE=0000 and NODE=FFFF are not
acceptable values.

DOS 3.2

If you are using MS-DOS version 3.2, you should switch back to 3.1
or upgrade to 3.3 or a 4.xx version.  There is an error in DOS
3.2's internal stack handler that can cause disconnects and even
occasional lockups.

Memory Conflicts

If you are using an EMS driver or other memory management
software, be sure that you are excluding your network adapter's
memory from the EMS page frame. For example, if you are using
Quarterdeck's QEMM, the correct CONFIG.SYS command to exclude an
Enhanced 2mbps adapter (at the default RAMBASE) is

DEVICE=C:\QEMM.SYS RAM X=D800-DFFF

If the adapter's memory is not excluded, your network may work
perfectly until you run a program that tries to access expanded
memory. After that, your computer may lose its network connection
or even lock up. 

Quite a few 16-bit VGA cards can also cause unexpected memory
conflicts, particularly in graphics mode. If your computer loses
its connection after running a graphics program, try forcing the
VGA board to 8 bit mode, either by setting its jumper or switch,
or by putting the board in an 8 bit slot. 

If you have Artisoft Enhanced 2mbps adapters and you do not plan
to use the monochrome (MDA) or hercules video modes, you can also
try setting the adapter's RAMBASE to RAMBASE=B000 (monochrome
video memory) to avoid the conflict.

Cabling

Cable, connector and terminator problems can cause a wide range of
symptoms, ranging in severity from an occasional disconnect to
complete network failure. If you have cable running through high
traffic areas, check to make sure that the cable isn't shorting
when someone walks or rolls over it. Use a multimeter to check the
continuity of the signal conductors and the shield and, especially
in the case of coaxial cables, make sure that the shield isn't
shorted to the signal conductor.  

Intermittent disconnects can also result if your network exceeds
the recommended maximum length for your adapter and cable type. In
the case of our 2mbps adapters, the cable types and lengths that
we support are: 

       Cable type                         Max.Length
       ---------------------------------------------                                                                                                     Maximum Length
       LANtastic cable (Artisoft)         1500 feet
       Belden 9729                        1000 feet
       AT&T Telephone grade wire           300 feet

If necessary, you can expand your network beyond these limits with
a LANtastic hub.

Our Ethernet adapters should be wired to conform with the IEEE
802.3 standard -- segment lengths of no more than 185 meters
(about 607 feet) for thin Ethernet, using RG-58 A/U cable, and
segments lengths of no more than 500 meters (about 1641 feet) for
standard Ethernet using thick coaxial cable. There are a
tremendous number of hubs, repeaters, concentrators, etc.
available for expanding your Ethernet network beyond the single
segment limits.