fast ethernet is a network technology specified by ieee standard 802.3u. it extends the traditional 10mbps (10 megabit/sec) ethernet technology to achieve 100mbps (100 megabit/sec) transmission and reception. because fast ethernet retains the traditional ethernet csma/cd (carrier sense, multiple access, and collision detect) protocol, it remains wholly compatible with 10mbps ethernet while providing a tenfold increase in network capacity.

    the fast ethernet standard specifies three subtypes, corresponding to three media types:

    1 100base-tx (using two twisted pairs in eia 568 category 5 utp or stp cable)

    2 100base-t4 (using four twisted pairs in a category 3, category 4, or category 5 utp cable)

    3 100base-fx (using two fiber-optic strands).

    the dfe-690txd provides full-duplex and half-duplex 100base-tx operation (in category 5 twisted-pair cable environments). it does not provide 100base- t4 or 100base-fx operation. to provide for traditional 10mbps ethernet operation in twisted-pair cable environments, the dfe-690txd also offers 10mbps ethernet operation, in full-duplex and half-duplex modes. the dfe-690txd's auto-negotiation capability provides for automatic selection of the best operation mode.