2400 Baud Modems with MNP \"Protocol\"

[fischer at RAND-UNIX.ARPA]

I looked (briefly) into the new 2400 baud modems for use with my Xenix
system.  The dealers all push versions with a built-in protocol called
MNP.  This protocol handles retries of bad characters, BUT (e.g., beware)
it is not really suitable for use on communications where the underlying
software already has a protocol.

With uucp, the MNP flow control will be incompatible, and thus one will
have to disable MNP.  

With Kermit, MNP is likely to play havoc particularly where the end-to-end
flow control needs to be preserved (likely at 2400 baud on systems which
might become busy), because MNP only appears to support modem to computer
flow control.

For interactive computer access, if you need control-s or control-q,
e.g., if you use an editor like emacs ever, then again you might have
difficulties.

The people who produced the MNP protocol, and whose marketing has
caused the modem suppliers to energetically advertise it's features
(without being knowledgable of its operation), ended up recommending
that I buy some other modem without the feature.

Finally, be aware that MNP is only a retry on error protocol;  it is not
a forward error correction device with hamming codes (as I expected from
its sales literature).