Exchanges that matter...

Stephen Stuart stuart at
Sun Dec 8 18:23:30 UTC 1996

> At the Atlanta-NAP we offer full duplex FDDI, why not try to get MFS to do
> it? Cisco now has a full duplex FDDI card, so you can do 200 Mbs into the
> NAP.

Every NAP with a GIGAswitch/FDDI offers full duplex FDDI; the MAEs,
Sprint, PAIX, and you. Buy a full-duplex-capable card, install it, and
you get full duplex. You, the NAP operator, do nothing; the devices
negotiate in and out of full duplex mode themselves.

I'm somewhat confused as to why you would say you offer full duplex
FDDI in a manner that implies no-one else does. If someone walked up
to your GIGAswitch/FDDI (or anyone's) with a full duplex line card,
they'd get full duplex unless you took some specific action to prevent
it (by, say, putting three stations on a ring), or if you disable it
in management (it comes enabled by default).

>From Chapter 1 of the Big Book of GIGAswitch/FDDI (June 1993):

"Point-to-point links can operate in a full-duplex mode to increase
bandwidth and reduce latency. Using FDDI, simultaneous transmission
and reception in a point-to-point connection between two FDDI adapters
that support full-duplex communication can provide twice the raw
bandwidth of the data link. When a point-to-point link is created with
a station that can use full-duplex mode, the communication mode is
changed from token ring to full-duplex. No token is passed in
full-duplex mode. Configurations can automatically move in and out of
full-duplex mode as the opportunity (two stations on a ring, both
capable) becomes available, or unavailable. Full-duplex mode can be
disabled using MIB objects in version 2.7 of the DEC Vendor MIB."

Since you point it out as a specific offering, does that mean you turn
it off by default? Do you charge more for it? 


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