info-vax@ucbvax.ARPA (10/17/84)
From: Art Berggreen <ART@ACC>
This is in response to an inquiry about tying T1 (1.544Mb/s) lines
to a VAX.
ACC developed a Front-End based around 68000 and VersaBus for
running the X.25 protocol over lines up to T1 rates. This FEP
is to be used in the NASA Space Telescope ground system to move
data from a ground station at NASA Goddard to the science institute
at Johns Hopkins University. The system has a measured VAX to VAX
(780s) throughtput of 800-900Kb/s over a 1 Mb/s line, using 1024
byte X.25 packets and 8192 byte VAX I/O requests under VMS. The
VAX loading was under 5 percent. The VAX interface is a single
quad card which plugs into the UNIBUS. The serial interface is
RS-422/449. The FEP itself is a 5-1/4 inch rack mount box.
We are stripping out X.25 level 3 and just running the HDLC level
2 for other projects. This gives a throughput advantage at the
highest line rates when the multiplexing of level 3 is not needed.
We don't currently have a UNIX driver, but plan to develop one
sometime in the future. We would be willing to work with anyone
interested in developing one.
It is conceivable to bridge two (or more) LANs by tying VAXs on
each LAN with a pair of the FEPs and make the VAXs gateways.
Contact me directly at ACC if interested in any more info.
ARPANet: Art@ACC.ARPA
Phone: (805) 963-9431
Art Berggreen
Advanced Computer Communication
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