barry@adelie.UUCP (Barry A. Burke) (02/16/86)
My company is relocating in a couple of months into a brand-spankin' new
office space, which is this minute being constructed to our specs. I am
responsible for specifiying all the data pre-wiring, and I'm not sure
about what transceiver cables to spec (I'm gonna go ahead and have the
xcvr cables installed in all the areas that may one day have Ethernet
devices).
Background:
My current network consists of two Ultrix VAXen: aVAX 11/750 and a
uVAX-II, and two Bridge CS/100-TCP terminal servers. All four
devices are currently interconnected via a DEC DELNI (they're all in
the computer room)- everything's TCP/IP.
I will soon add 2 or 3 more CS/100's, 2 CS/1-SNA's, a SUN 2/160M
workstation, and an Imagen 8/300 Laser printer w/ethernet interface,
all TCP/IP
In the new facilities, I plan on putting all the Bridge equipment on
the DELNI, and connecting the DELNI to the (new) coax backbone. The
VAXen, the SUN, and the Imagen will all be cabled directly to the
coax.
Current administration plans are to also introduce several XEROX
6085's and a XEROX laser printer to the shop- I'd like to hang them
off of the same Ethernet coax (yes I realize they won't talk
TCP/IP).
The Questions
If I look at the DEC Comms guide, I see three different transcievers
and two different cables available:
H4000 - the `original' DEC no-frills xcvr
H4005 - the `new' DEC xcvr with post-amble/trailer checking (?)
H4005 - " " " " without " " " "
...... - `original' DEC xcvr cable
,,,,,, - "802.3" xcvr cables
And of course, if I look into the details, the DEC guide gives no
recommendations for which to use with Ultrix+DEUNA/DEQNA. And there
is some obscure warning about not using the H4005 with the DELNI
under certain circumstances.
Q0. What's the difference between the xcvrs and cables mentioned?
Q1. Which xcvr+cables should I use for:
the VAXen?
the SUN?
the Imagen?
the DELNI?
(NOTE: I'm using the `original' DEC xcvr cables now- both for
the VAXen and the Bridges).
On to XEROX. The XEROX xcvr cables are somewhat different (at least
in spec) than the DEC cables in that while there seems to be the
same number of wires, they are paired and shielded differently.
Q2. Despite the differences, can I use DEC xcvr cables to connect
XEROX equipment to my coax?
Q3. Can I use DEC xcvrs? Which one?
Q4. Is there really a "standard"? I'd like to pre-run the xcvr
cables without regard to which vendors equipment is gonna get
used where- I also thought that was the intent of Ethernet
(semi- ;-).
Q5. Any other things I should watch out for?
Administrivia:
For the record, I probably won't actually buy cable from DEC, but
the place I do buy from will build "identical" cables to any of the
above (DEC or XEROX)- usually for about 1/2 DEC's price and with 1
week delivery.
I've no qualms in using any other xcvr that might be recommended, as
I'm resigned to the fact that DEC probably won't give me HOOT for
support of this LAN anyway.
Q6. Anybody know where to get "DEC EtherJack" equivalents for less &
quicker? They're sure a nice way to hide the place where the
TEFLON cables meet the (flexible) office cables)
I've set this article to be followed up in "net.lan", in case you
want to follow any discussions it may create. I would prefer direct
mail responses, however; I will summarize for the net as needed.
Hopefully, I can get some quick answers, as I only have 1 1/2 weeks
to get the specs to the laborers...
THANKS!
--
LIVE: Barry A. Burke, (617) 965-8480 x26
USPS: Adelie Corporation, 288 Walnut St., Newtonville, MA 02160
UUCP: ..!{harvard | decvax!linus!axiom}!adelie!barry
ARPA: adelie!barry@harvard.HARVARD.EDU, barry%adelie.UUCP@harvard.HARVARD.EDUscarter@caip.RUTGERS.EDU (Stephen M. Carter) (02/17/86)
In article <585@adelie.UUCP> barry@adelie.UUCP (Barry A. Burke) writes: > >Q0. What's the difference between the xcvrs and cables mentioned? >Q1. Which xcvr+cables should I use for: > > On to XEROX. The XEROX xcvr cables are somewhat different (at least > in spec) than the DEC cables in that while there seems to be the > same number of wires, they are paired and shielded differently. > >Q2. Despite the differences, can I use DEC xcvr cables to connect > XEROX equipment to my coax? >Q4. Is there really a "standard"? I'd like to pre-run the xcvr > cables without regard to which vendors equipment is gonna get > used where- I also thought that was the intent of Ethernet > (semi- ;-). > Another difference between the "Dec" and the "Xerox" is that "Dec" likes to use one gauge heavier wire. As far as most things go, the good ole Xerox works fine for version 1/2. We use them for our Dec machines without problems. Now, on to IEEE. The major difference between IEEE and Xerox is the ground shield pin. In Xerox, they use pin 1 and in IEEE, pin 4. Also in IEEE the ground is not shield. (ie pin 4 is isolated from case/shield/case). In most cases, you can mix without problems. However, one high-level guru told me that he has seen cases where it has caused problems. I have seen machines where the bulkhead<-->board cable does not even run ground and is had from the chassis/connector. This would be one example where the cable type doesn't matter much. But to answer your question, you can get a cable to handle everything. This is by having a "IEEE/Xerox" cable. To get these, you can: 1) Buy pre-assembled. I know Cabletron offers these 2) Make your own. Use IEEE format (ie isolate ground and shield), then jumper pin 1 to pin 4. Note the drain wire on this cable is wrapped with one of the pairs and isolated from outer shield. 3) Use IEEE cables, either jumper 1 and 4 before you install, or do it as needed. and on a final note, be sure to use Teflon if your building code requires it, and keep maximum lengths < 50 meters.. (and if you will be getting close to this length, consider the heavier wire....) -SCarter uucp: ...{harvard, seismo, ut-sally, sri-iu, ihnp4!packard}!topaz!scarter arpa: SCARTER@RUTGERS or SCARTER@RED.RUTGERS.EDU