Newsgroups: bit.listserv.big-lan
Date:         Tue, 22 Dec 1992 12:54:19 EST
From:         BIG-REQ@SUVM.BITNET
Subject:      BIG-LAN Digest, Volume 4, Number 85, Tuesday, December 22, 1992

BIG-LAN DIGEST          Tuesday, 22 December 1992      Volume 4 : Issue 85

Today's Topics:

                      RE: Why just 30 thinnet nodes
        Ten Outlying Alaskan Schools Tie VINES WAN Over Satellite

Moderated by John Wobus, Syracuse University

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----------------------------------------------------------------------

Date: Mon, 21 Dec 1992 11:46:32 -0600 (CST)
From: sjulstad@stolaf.edu (Michael Sjulstad)
Subject:      RE: Why just 30 thinnet nodes

>Date: Wed, 16 Dec 92 10:12:58 KST
>From: ksn@giconet.gsic.co.kr
>Subject:     Why just 30 thinnet nodes?
>
>Hi!
>
>Does anyone know the reason that the maximum attachment is 30 for thin
>Ethernet/IEEE802.3?
>
>Please explain the reason.
>
>Soo N. Kim
>Goldstar Information and Communications

I'm no expert, but I've done some work in this area.

There may be a variety of reasons, but one that I perceive as
understandable is the amount of power transmitted by the thin-net
transmitter, along with load that the line, terminations, receivers,
etc.. represent to this transmitter.  Further, the tolerences for
collision detection are extremely tight, and it is (effectively) a dc
voltage on the transmission line.  Anything outside of threshold
voltage is considered a collision.  One can probably drive many more
than the maximum published value of 30 if one is careful with length,
quality of coax, terminations, connectors, etc... but IMHO, breaking
the rules generally isn't worth the headaches of strange things
happening later.

Anyone else know more?

Michael Sjulstad
sjulstad@stolaf.edu

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Date: Tue, 22 Dec 1992 15:31:33 GMT
From: IMAGING.CLUB@OFFICE.WANG.COM ("Imaging Club")
Subject: Ten Outlying Alaskan Schools Tie VINES WAN Over Satellite

A key element of the Alaskan Distance Education Delivery system is
a Banyan VINES wide area network (WAN).  Using a channel on the school's
designated bandwidth, the 10 schools are tied together over the Wang-
installed Banyan WAN using Wang PCs and integrated with three Wang
VS minicomputers in Barrow.  Two independent uses exist on the WAN:
one for administration and the other for educational purposes.  The
NSBSD owns the telecommunications equipment that interfaces with the
satellite system.

"Initially, our major problem was communications between our outlying
school sites and communication with teachers, principals, and maintenance
people," said Martin Cary, NSBSD coordinator for information and technology.
"We had been doing a dial-up log on to the VS because we didn't have the
kinds of communication infrastructure that was available in other parts
of the country."

School officials decided to install a WAN to interconnect everyone in the
district.  Cary said the WAN enables the district to accomplish three
goals: to communicate via electronic mail, to give access to applications
on the VS, and to offer data processing services district wide.

"We had decided in advance that we wanted to use Banyan VINES because of its
strong wide area networking capabilities," explained Cary.  Wang won the
contract to provide the Banyan WAN, PCs, servers, and installation of
hardware and software.  Wand did much of the initial design in conjunction
with the district.  In Barrow, the five servers are connected via fiber
optics, while the WAN interfaces with the VSs through LightSpeed Gateway
software.

The installation of the WAN presented a problem for Dave Thompson, Wang's
principal systems consultant, and his team consisting of Ted Israelson
and Michael Knobloch.  Dave has worked with the NSBSD since 1985 when the
district replaced its IBM System/34 with Wang VSs, which offered a more
complete office automation package.

"Most of the villages could only be reached by a small single-engine
airplane, which we chartered from Barrow," Dave said.  "We had to make
sure that we staged all the equipment properly and had everything with
us when we got ready to go.  We couldn't go back to the office if we
forgot something."

The Wang team started the installation in the summer, when there is
24 hours of daylight.  "You tend to work while the sun shines, so we
were able to put in 14-16 hours a day without even thinking about it,"
Dave explained.  They turned the WAN over to the school district two
months later.

An example of how the administrative network is used might be that a
principal in the village of Kaktovik, located on the Canadian border
300 air miles (483 km) away, would type in the attendance for the day
on her PC and send the file to a PACE RDBMS database on the VS.  The
student network is used by pupils to pass files among themselves and
by special resource teachers in the Distance Education studio to send
out tests or receive homework from individual students.

Administrative staff in the central offices also use the VS for
accounting, payroll, student records management, WP Plus, and Wang
OFFICE Email.  The installation of the WAN made the applications on the
VS available to everyone in the district.

Even though its primary task has been completed, Wang continues to work
closely with the NSBSD.  "Our network is growing at such a speed that
internally we just don't have the personnel to take care of everything
we want done in the timeframe available," Cary said.  "Consequently, we
bring in Wang specialists to take care of specific projects.  And that's
worked out very well."

Michael.Willett@OFFICE.Wang.com

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End of BIG-LAN Digest
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