smiller@umn-cs.CS.UMN.EDU (Steven M. Miller) (10/29/89)
About a week ago I posted a request asking for folks opinions on
thick,thin and twisted pair solutions for wiring up a network.
Here's all the responses that I have recieved so far. Not everyone
agrees on everything, but there was an overwhelming favor for
twisted pair.
Thanks everyone for the responses. I will continue accepting
other folks war stories and opinions and I will post them as they
come in.
-Steve
From: Wayne Sung <sung@mcnc.org>
Subject: Re: Lan Options (Network of Suns)
option 1: thick wire should never have existed.
option 2: my own preference. You have no impact on error and throughput,
although since you have far fewer mangled cable pieces errors may actually
go down. Two days ago we measured 6 errors in over 600k packets with a peak
rate of 40% in a totally thin installation. My primary reason for liking thin
is that you can daisy chain units in one room. UTP requires separate
transceivers for each unit. Also, if you put thin wire heads on your old
transceivers they will work on thin wire just fine.
option 3: Farallon's product, I believe, is for hanging multiple LocalTalk
nets off an Ethernet, i.e. the tp side is LocalTalk, so it will help your
Mac situation but nothing else. What you are looking for is UTP equipment by
Cabletron, Lattisnet and others. It's actually a little expensive to start
since you have to buy a big concentrator but otherwise there should be no
performance penalties. I am just now trying some of these, but what I'm trying
to do is eliminate using short pieces of coax. All these devices will be in
adjacent racks, and the cost of making short coax pieces is too high. Oh yes,
watch your distances and wire quality if using UTP Ethernet. In particular,
the two pairs must be exactly that - you can't have any four wires, it must be
two pairs - and you will cut your distance down to 300 ft or so.
From: blyon@legato.com (Bob Lyon)
Subject: Re: Lan Options (Network of Suns)
Option 1:
Thick Net.
Works well, but is very expensive to grow and maintain.
Option 2:
Thin Net.
We at Legato have found Thin Net to be very easy with network node
counts of less than five machines. After that number, it suddenly gets
close impossible to build and maintain a near error-free network.
Option 3:
Twisted pair. Farallon supposedly has a new product that allows me
to use a phone system type connection that is supposedly trivial
to reconfigure. I know next to nothing about this and don't know
what the major disadvantages are let along error rates, cable distances
and throughput. Using twisted pair also makes our appletalk network
easier to deal with. We can use the connections for either atalk or
enet.
DO IT! Farallon is OEMing the David Systems "David ExpressNet"
twisted pair ethernet product.
This is what Legato uses. We started with six nodes and are now
up to nineteen - two Sun 3/160's, a Sun 4/110, four diskless
PCs (we use PC/NFS), four diskless 3/80's and eight diskless 3/50's.
Growth has been trivial. We use existing phone lines which were
installed in our building over a decade ago.
There are twelve ports per hub box. Each hub has a cheaper net
connector coming out its back so you can chain many hubs
together. Alteratively, you can use hub ports themselves to tie
the hubs together. You reconfigure the hub-box via a simple to
use dumb tty interface. We tip to the hubs via an RS232 line
hooked into our 3/160's ALM ports.
The product is new to Farallon, but a very mature product from
David's point of view. David has been around for eight years
in the "voice & data" PBX arena. Their ExpressNet product has been
one of the companies' better kept secrets. I believe that their
product is compliant with the emerging twisted pair standard; I
know their folks are on the committee.
David is located either in Cupertino or Santa Clara (area code 408).
Legato is a very happy David customer. There are other firms
that do twister pair, the most famous being Synoptics.
/Bob Lyon
Legato Systems, Inc.
From smb@ulysses.att.com
Subject: Re: Lan Options (Network of Suns)
Thinwire Ethernet can be used either like thick, or it can be run
in a star to DEMPRs (DEC's thinwire multiport repeater) or equivalents.
This, in effect, gives you a star configuration. Twisted pair
Ethernet is also a star.
For the reasons you mention, and a lot of others, I've become very
fond of star-configured Ethernet. I strongly recommend that you
wire things that way; thinwire or twisted pair is less important a
criterion. (There are other tradeoffs there; twisted pair is cheaper,
and may already be present for phone and in any event could be used
for phones or RS-232; with thinwire, you can have multiple devices
on one repeater port.)
If you go with twisted pair, make absolutely certain that you buy
stuff that's compatible with the draft 802.3 "10BaseT" standard.
A number of vendors make this gear, including AT&T (STARLAN 10).
I have no idea if the vendor you named uses 10BaseT or a proprietary
scheme; there are several of those around, too.
From: Geoffrey Kratz <KRATZ@BNR.CA>
Subject: LAN Options and UTP
We are using UTP here at BNR almost exclusively (the last of the
coax comes out in the next few months). I can tell you that we have
had nothing but good luck with it.
You can run it at full ethernet speeds (10 Mbps) but it means that
the ethernet hardware manufacturers have to be right on the specs
for clocking. Throughput has never been a problem in properly
engineered subtrees of the network. Distances, though, aren't too
bad. They are enough to cover large buildings (something like
200 feet from the node to the first hub, then another 200 feet
from that hub to the next, then to a bridge and a fan-out box). We
have been able to cover 5 story office towers (average floor area)
with no problems at all. The distance, though, is WAY too short
for use between buildings. PVC coax or some other solution is
needed for outside plant.
We are using HP bridges, hubs and MAUs, and with the exception of a
local mod on the UTP drop cables (BNR uses the standard Northern
Telecom RJ-11 four pin phone jack, and the HP equipment uses an
RJ-45), we have used existing 4-pair phone cables from the wiring
closets out to the floor.
You will find that UTP is your cheaper solution in the long run, from
a cost point of view. A drop costs us about $400-$500 a seat. This
figure varies, of course, on how many units you are putting on the net
and how many hubs and bridges you need to cover your building(s).
From a maintenance point of view, UTP is a TREMENDOUS advantage over
either thick or thin. You don't get breaks in the bus the same way
you can in the coax-based solution (we have this especially troublesome
with the THIN wire installations we used to have. People were always
kicking the cables and pulling the cable out of the connectors!). As
well, moves of equipment is VERY trivial. Just a couple of punch-downs
of jumpers on the BIXX block in the wiring closet.
One drawback, of course, are that the MAUs use those stupid slide-lock
AUI connectors. You may want to get the screw-down kind (kinda rare,
but most cabling outfits can get them for you).
We at BNR decided that UTP was the best way to go, both from a technical
and a dollars point of view. We saved a LOT of money by being able to
use the existing building wiring, and by making maintenance of the
physical and link layer of the LAN very quick, easy and cheap. To be
honest, if I were wiring up a medium to large site, I would go with UTP,
and wouldn't even bother to look at a coax solution.
--
Geoff Kratz Bell-Northern Research, Ltd. Ph: (613) 763-5784
Internet Systems P.O. Box 3511, Station C FAX:(613) 763-3283
Ottawa Ontario Canada K1Y 4H7
BITNET: kratz@bnr.ca I can put my foot in my OWN mouth, thank you!
From: sdl!batgirl!gregt@uunet.UU.NET (Greg Tusar)
Subject: Re: Lan Options (Network of Suns)
The company I work for is also in the process of moving, and we're investigating
the same thing.. Twisted pair has the same 10 Mbps bandwith as thick-net, and
as you mentioned, it is extremely easy to reconfigure network topology by having
a ``wiring closet'' with lines to the net, and lines from each system that you
can connect with a RJ14 or whatever. If you're maintaining a backbone, you may
also want to look into Sun's FDDI/DX. It boasts an 100 Mbps bandwith (although
I've heard the 80 Mbps is a more realistic number).
sdl!gregt@uunet.uu.net // Gregory Tusar // Silicon Compiler Sys. // Warren, NJ
From: johnl@esegue.segue.boston.ma.us (John R. Levine)
Subject: Re: Lan Options (Network of Suns)
Organization: Segue Software, Cambridge MA
I'd suggest a thick net backbone with multiport repeaters fanning out
thinnet to a BNC plug in each office. People who have looked at
Synoptics twisted pair say that by the time you price it out, it's
awfully expensive and not worth it.
Bringing a thinnet to each office is nice. You run the cable from
the wall to your computer, with a terminator on the BNC at the
computer. If you have more than one computer in an office, you
daisychain them together without any extra equipment. If you step on
your cable, the repeater limits the damage to your segment. Pulling
thinnet is a lot easier than thicknet or transceiver cable since it's
thinner and more flexible. In fact, pulling transceiver cable is the
worst because you usually have to take the connector off the end
you're pulling, and then reconnect all those little wires in each
office. Attaching BNC connectors is a snap in comparison.
If your offices are close enough to each other, you can even dispense
with the thick backbone and tie all the repeaters together with a
DELNI or the equivalent.
Regards,
John Levine, johnl@esegue.segue.boston.ma.us, {spdcc|ima|lotus}!esegue!johnl
From: rutgers!eddie.mit.edu!bambi!sullivan!sullivan (Chris Sullivan)
Subject: RE: Lan Options (Network of Suns)
> Option 3:
> Twisted pair. Farallon supposedly has ...
There are several companies that do Ethernet over this existing
voice plant.
The restrictions are many (distances, cable types, ...),
but there can be real cost advantages IF your 'new' building
was sufficiently over-engineered on the voice plant. Many
offices built in the 70's are candidates.
-----
Another company to look at is LattisNet (sp?). I've seen their
stuff on-line.
Best of luck,
Christopher Sullivan Schlumbeger Technologies
CAD/CAM Division
From: glen@aecom.yu.edu (Glen M. Marianko)
Subject: Re: Lan Options (Network of Suns)
Personally, I get chills when I think of anyone still using thick
as a cabling medium to anything but concentrators in a wiring
closet. I think you know what I mean.
I am personally torn between twisted pair and thinnet. Torn beacuse
every time I think of standardizing on either one at a particular
site, I find some special case that needs the other. It is for this
reason that I like concentrators that give me the capability to
do BOTH out of the same chassis, and change my mind on an individual
leg when I want to.
For example, today I have one workstation on my desk in my office.
Ok - so I use the 2 spare pairs on my phone RJ-45 for the network
connection. Two months from now I get another workstation - I'm
moving up in the world. What now?? Run another twisted pair
line to the closet? NO! Convert that twisted pair line into
thin ethernet, and run both workstations on thin.
My company (a LAN/WAN systems integrator) carries Synoptics and
Cabletron. Both can do this - and both can have a choice of twisted
pair, thin, and fiber modules in the same wiring concentrator.
However, I lean heavily toward Cabletron, because they do it cheaper,
nicer, and cleaner.
So, my preference is actually both - if you think about it.
Hope this helps. If you would like more info, drop a land-line.
-- Glen M. Marianko Manager, LAN Services Glasgal Communications, Inc.
151 Veterans Drive Northvale, New Jersey 07647 201-768-8082
glen@aecom.yu.edu - {uunet}!aecom!glen (Courtesy of AECOM & unaffiliated)
--
-Steven M. Miller, U of MN