FSC-0016

FidoNet mail session startup
by
Bob Hartman, 1:132/101

Presently, FSC001 contains no provisions for what actually happens
when a call is received. All it says is that the baud rate is determined,
and a netmail session starts. Currently, this is one of the most difficult
sections of a netmail program to get working. All programs have different
timeouts, different ways of determining baud rates, not to mention the fact
that MNP modems talking to non-MNP modems can cause problems. For these
reasons, I propose the following "standard" for netmail programs that deal
with the beginning of a netmail session:

1. When carrier is detected, all input should be deleted by the receiver
for a period of 2 seconds (I would even be comfortable with 5 seconds,
but it makes human callers a bit unhappy). This enables most MNP
modems to send their string of MNP "garbage" and not cause spurious
characters to impact the netmail startup logic.

2. The sender should send ONLY carriage return and space characters as
"whacking return" until the receiver acknowledges by sending a string
containing a carriage return or space character.

3. The sender should whack return at the rate of one character per second.
This gives Fido 11w and other implementations time to purge buffers if
line noise is received which would screw up the baud rate detection
logic.

4. After recognizing the "whack" of the sender, the receiver should
disregard all characters except the following:

TSYNC - start of an FSC001 session (a delay of at least one second
should appear here so the sender can recognize a valid NAK -
otherwise, it could still be the banner file being displayed).
WaZOO mailers should disregard the first TSYNC in the hopes that
a YooHoo will appear. If a YooHoo is not received within 2
seconds, or a second TSYNC appears, an FSC001 session should be
started.

YooHoo - signals the start of a WaZOO netmail session. FSC001 mailers
should just ignore this character as noise.

Carriage return, space - Send message containing carriage return
and/or space. The sender may have missed it the first time
around and is still "whacking return".

Line feed - This is probably a user, and a message explaining things
to him/her should be sent out.

Escape - This character is currently used by at least one front end as
a quick method for users to enter the BBS. If received in "mail
mode", it should always be ignored. (I propose this as a
"standard" so that all front-ends can use this feature. If it is
not standardized now, all front-ends could conceivably use
different characters and further muddle the picture when a
netmail session is starting.)

5. After the sender has started sending TSYNC and/or YooHoo, the responses
must be looked at very carefully. A line with no activity for at
least .5 seconds must be seen. Otherwise, it is possible that a
banner file is still being displayed and a 'C' is meaningless.

If all FidoNet compatible mail programs were to follow these
conventions, I believe that the start of a netmail session would be much
more reliable than it is right now. Too often we see front end packages
fall through to the underlying BBS because of MNP negotiation, or one end
taking longer than the other to give a connect message.