                Using the Wisconsin Network - Part 27
                      by Andy Nemec, KB9ALN
 
     Lately we've been looking at several enticing possi-
bilities of automating packet radio. Most operators don't
realize it, but there is a fair amount of automation of the
mail system built right into most every TNC these days. It was
the vision of the first packeteers to have "door-to-door" mail
service with packet radio in the very beginning. In this
installment, we will explain how your local BBS and your
station can work together to make this door-to-door delivery a
reality. Yes, we want your TNC to become part of the BBS
Network and interact automatically with your local BBS so that
you can enjoy a more automatic packet E-mail service.

     The concepts used in BBS mail forwarding might be a little
foreign to most people, and one can easily "upturn the apple
cart" if you do not know how the system works. For that reason,
we will explore a bit of how BBS mail gets from point A to
point B. This will help you to understand how your TNC will
interact with the BBS network, and help stop problems before
they start.

     First, we'll talk about how a BBS gets packet mail and
flood messages, and what it does with these messages once it
has them. Notice that you may see messages from all over the
country, maybe even all over the world on your local BBS. They
arrive through the "store-and-forward" system. This system is
simple enough in concept. Messages are stored on a BBS, and
sent to the next BBS down the line in a large group or batch.
One BBS will automatically connect to another to establish a
"forwarding session" when messages are exchanged. When the
sending BBS is through with it's work, the it asks "Do you have
anything for me?". If so, messages are "reverse-forwarded" to
the originator of the forwarding session. Messages are stored
on the BBS, and the next BBS down the line does the same thing
until it gets to the last BBS in the line.

     While this seems simple enough, there are a large number
of packet radio BBS's present world-wide and a large number of
paths to get to a BBS. This means that there is a possibility
of a message reaching a BBS through mulitiple forwarding
routes. How does your local BBS know not to accept a duplicate
message? Each message has a unique message identification
number called a "MID", or a Bulletin Identifier called a "BID".
This is sort of a unique serial number that accomanies a
message. It is generated by the originating BBS or TNC when the
message is created.  Your local BBS keeps a list of these
"BIDs" and compares what the BBS is proposed to receive during
a forwarding session to what it already has. If it sees that
unique "BID" on a message it already has, it refuses that
message and asks for the next one in the batch to be forwarded.

     If you've been a regular reader of this series, you
already know about the hierarchical addressing scheme that
BBS's use world-wide. If you do not, please consult part 15 of
"Using the Wisconsin Network" before proceeding. This is very
important, and cannot be overlooked. If you're not familiar
with the casual operation of your TNC's mailbox, and how to
command your TNC, stop right here and either read up on this,
or obtain the help of an experienced operator.  Mistakes made
here can show up world-wide, and may cause you to be the
recipient of some unfriendly advice.

     Once you are at the stage where you are comfortable with 
these concepts, you can proceed. You will also need the
following to properly set up your TNC:

    1) The permission and participation of your local BBS
       Sysop. 
    2) To know if your TNC's mailbox supports forwarding and
       reverse forwarding.
    3) Knowlege of the size of your TNC's mailbox. How much can
       it hold?
    4) Your packet station to be "on the air" when you expect to
       participate in a forwarding session.
    5) Knowlege of the times that your LAN frequency is least
       busy.
    6) The call-sign of the BBS you intend to exchange mail
       with. This should be your "home" BBS.
    7) The path you use to connect to it, and the command you
       use to connect to your BBS through a node, if you use
       one when accessing your local BBS.
    8) Knowlege of your home BBS's hierarchical address.

     Now the "why" of all of this. 

     You need the permission and participation of your local
BBS Sysop because he or she has to set up the BBS both
originate a forwarding session and to accept a proposed
forwarding session from your station. Keep in mind that some
BBS's are set up with limited capabilities and a big upgrade
may be in order to accomadate your request.

     Obviously, you need to know if your packet TNC can
forward. Most will accept a reverse forward. You can often
find information concerning this in the "PBBS Sysop" section of
your TNC's commands manual.

     You need to know how big your mailbox size is in bytes
because this has a direct bearing on how much incoming mail you
can receive. You can usually find this out by logging onto your
mailbox when it is empty. It will tell you how many bytes are
"free". Keep in mind that a typical typewritten page formatted
at 80 columns by 54 lines is between 2000 and 3000 bytes. If
you expect to accept mail in any quantity, make sure your TNC's
mailbox is suffuciently large to accept what you want to get.
Remember to keep your mailbox clean of old messages.  Otherwise
it will take multiple forwarding sessions to get your messages.
This also has a direct bearing on whether you will tell your
TNC to kill off any messages that have been forwarded.

     Likewise, you would expect to keep your packet station
available for BBS connects in order to receive your mail. If
yours is a part-time packet station, perhaps you should
consider leaving the messages on the BBS for manual retrieval.

     You also would want to keep mail forwarding resticted to
the times when your LAN frequency is least congested. Involved
forwarding sessions can reduce someone else's packet through-
put. Your BBS Sysop may also have forwarding to other BBS's
scheduled for a particular time. Consult your BBS Sysop when
deciding what time to forward.

     Obviously, you need to know the call-sign of the BBS and
how to get to it. If you use a node to get to the BBS, you have
to know just what text to send to the node in order to get to
the BBS. Most TNC's that accomadate node connections to a BBS
for forwarding can only utilize one node connection. If your
BBS is some distance away from you and requires multiple node
connections to reach it, you might best use a BBS closer to
you. If you connect to your local BBS directly or through just
one node, then you are a good candidate to interact with the
BBS network.

     It is best to have your home BBS the same as the one you
intend to forward with. Otherwise, things may get confusing
for respondents of your messages. Therefore, you may get your
messages out, but not back. This may also leave some poor BBS
Sysop down the line wondering what to do with your mail. He may
not know how to get it to you.

     The last item you will need to know is the correct,
complete hierarchical address of your home BBS. This is entered
into your outgoing messages so that people may respond to your
messages correctly. The BBS network may know very little about
your mailbox-in-a-TNC, but it will know how to forward to your
home BBS. It is your home BBS that knows enough to pass a
message along to you.

     In the next few installments, we will look at some of the
most common TNC's and how to specifically set them up for
door-to-door mail service. 

Until next time, 73 from Andy.
