========
Ethernet
========

.. warning:: Under progress!

History
=======
Bob Metcalfe first described the ethernet system in a memo while working at
the Xerox Palo Alto Research Center in 1973 ([oreilly]_). It was based on
the earlier *Aloha* system developed by Norman Abramson at the University of
Hawaii. *Aloha* was a radio network for inter-island communications.

Structure
=========

Data Frames
~~~~~~~~~~~
The frame format is the same for ethernet systems of any speed.

====================       ===========
Section                    Size (bits)
====================       ===========
Preamble                   64
Destination Address        48
Source Address             48
Type Length                16
Data                       46 to 1500
Checksum                   32
====================       ===========

.. topic:: Preamble

    The preamble originally served as a "warm up" period for hardware to 
    stabilize and prepare for the rest of the frame.

.. topic:: Source and Destination addresses

    Manufacturers are given a 24 bit id (first half), and are expected to
    ensure the uniqueness of the second half of each device's address.

    The IEEE-SA (Standards Association) delegates addresses.

.. topic:: Checksum

    The checksum (or Frame Check Sequence) is a Cyclic Redundancy Checksum.

.. [oreilly] `Ethernet: The Definitive Guide`:title:, by Charles Spurgeon.
              O'Reilly, 2000