2. Description of Related Art The purpose of a digital communication System is to enable the
exchange of bit-encoded information among various electronic devices located at various
places. The functions necessary to accomplish this purpose can be divided into Seven
groups, each group corresponding to one of the layers of a Seven-layer data-
communications protocol model adopted by the international Standards community, as
described in Section 3, 1 of Data Networks by Bertsekas and Gallagher (Prentice-Hall …