"
Fall back" is a feature of a
modem protocol[?] where two modems which experience data corruption, e.g. due to line noise, can renegotiate to use a lower speed connection. "
Fall forward" is a corresponding feature where two modems which have fallen back to a lower speed because of data corruption can later return to the higher speed if the connection improves.
Article based on fall back (http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi?query=fall+back) and fall forward (http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi?query=fall+forward) at FOLDOC (http://www.foldoc.org), used with permission.