dot3(6P)                         DG/UX 5.4.2                        dot3(6P)


NAME
       dot3 - IEEE 802.3 carrier sense multiple access with collision
       detection

DESCRIPTION
       IEEE project 802 has defined specifications for the lowest two layers
       of an OSI model network architecture, the physical layer and the data
       link layer.  Project 802 focuses on the implementation of these
       layers for a local area network.  It divides the data link layer into
       a logical link control (LLC) sublayer and a media access control
       (MAC) sublayer.

       802.3 is a MAC sublayer that operates below the LLC sublayer.  802.3
       is a standard for providing carrier sense multiple access with
       collision detection (CSMA/CD).

       Data General's dot3 is a Streams module that sits on top of the
       Ethernet device driver to provide 802.3 functionality to upper-level
       protocols.  This module, when used with the llc(7) multiplexor,
       allows the dgen, hken, or inen Ethernet device driver to be used to
       provide IEEE 802.3 functionality to one stream while providing
       Ethernet functionality to other streams.

       Because of the fact that the 802.3 standard uses a length field
       instead of a type field in its header (as in Ethernet), it is not
       possible for more than one stream to the ethernet device to have the
       dot3 module in it.  The reason for this is that it is not possible to
       demultiplex based on the length field of the 802.3 packet.  The
       implication of this is that if a stream is open to the inen device
       that has llc and dot3 in the stream, another stream to the same inen
       device that tries to push the dot3 module on it will never receive
       packets upstream, until the first stream with the dot3 is closed.

SEE ALSO
       netinit(1M), llc(7), dgen(7), hken(7), inen(7).






















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