For the record, and it may be of help to some of the Apple II folks. With a TCP/IP to serial bridge, you have a set of libraries on the TCP/IP connected host which capture commands to a virtual serial port (sent as if you were using a VT terminal etc) and encapsulate them in TCP. I've seen device specs that list Linux and Windows support, but not Mac OS X or earlier. The TCP packets whizz along the network to the bridge, which assembles them into the right order, and then translates them back into serial.
And it obviously works in the opposite way.
From this we can assume that the bridges have some cache in order to re-order out of sync TCP packets. Probably enough to cope with out of sync TCP packets emulating a 9600bps connection, but not 230kbps.