资料来源 : Free On-Line Dictionary of Computing

Maximum Transmission Unit
     
         (MTU) The largest number of bytes of "payload"
        {data} a {frame} can carry, not counting the frame's header
        and trailer.
     
        A frame is a single unit of transportation on the {data link
        layer}.  It consists of header data plus data which was passed
        down from the {network layer} (e.g. an {IP} {datagram}) plus
        sometimes trailer data.
     
        An Ethernet (V2) frame has a MTU of 1500 bytes but the size of
        the frame can be up to 1526 bytes (22 byte header, 4 byte CRC
        trailer).
     
        See also {fragmentation}.
     
        (2000-10-07)