[3c509] N-Way Auto Negotiation and Full Duplex

[Donald Becker]

On Mon, 16 Sep 2002, Wm. G. McGrath wrote:

> "Correct.  And pre-NWay full duplex is non-standard.
> 
> So what did the 3Com 509B's connect to to achieve full duplex before
> NWay?

Other gear with the  ability to be set to full duplex.  The way to
implement full duplex was obvious enough that the implementations were
compatible.

The problem comes when mixing gear that has set to forced full duplex,
and normal Ethernet.  There are serious network problems, and those
problems break the "plug and play" nature of Ethernet.  So full duplex
was accepted into the standard only when NWay autonegotiation was
developed, and full duplex is always tied to autonegotiation (on twisted
pair).

> "Read
> "  http://scyld.com/expert/NWay.html

> Very clear. 3.2 and 4.4. Auto negotiation's backward compatability
> is limited to half duplex modes. Sparse.

Note that I can't take the credit for writing this -- Bill Bunch at
NatSemi did all of the writing and I just made a few minor changes.

-- 
Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993