🚀 go-pugleaf

If we are not allowed to use "live" cable (ie Ethernet), then
we have used a pair of Codenol modems to a fiber (since this was
all in a PacBell conduit, they sort of do the work if you tell them
what needs to be done).  [Can't run Etthernet across our street].

If the buildings are adjacent, it is cheaper to just run the Ethernet
(if you have a distance problem, I don't believe the fiber helps unless
 you get something smarter like a Vitalink or somesuch that does something
 like repeat the packets; this is where you begin to need gateways to
 keep your protocols happy with extended delays, and/or internetwork
 routers to move across non-homogenous media; not to mention that local
 protocols like "get me a printer" are confused if "local" isn't).

We also use our internetwork router over microwave and leased lines to
extend our net, but that sounds like overkill for two adjacent 
buildings.

> We are in need of a way to extend our network across a conduit to an
> adjacent building.  To simplify matters, we'd like to use an "ethernet
> extender" device that hooks two halves of an ethernet together
> with a fiber optic cable and looks like a repeater (?).  I seem to
> remember that something like this exists, but I don't remember much
> about it.  Does anyone know about such a product?
> 
> Does anyone have clever ideas of how to connect two ethernets in
> different but adjacent buildings (don't bother to tell me about
> gateways, I know about them).
>  
> - Geof Cooper
>   Imagen

In article <3732@sun.uucp> djc@sun.uucp (David J. Cardinal) writes:
>If the buildings are adjacent, it is cheaper to just run the Ethernet
>(if you have a distance problem, I don't believe the fiber helps unless
> you get something smarter like a Vitalink or somesuch that does something

You believe wrong. If you will check your Ethernet or IEEE 802.3 spec
you will see that a coax segment has a length limit of 500 meters.
Coax segments can be connected together with repeaters. There can be
up to two local repeaters between any two stations. An Ethernet is
limited to 1500 meters of coax between any two stations. In addition
you get up to 1000 meters of point to point link between two halves of
a remote repeater. The max distance between any two stations is
therefore 1500 plus 1000 plus 50 * 6 = 2800 meters. In such a max'd
out system, there would be six 50 meter transceiver cables.

By the way, Belden 9880 is not rated waterproof. Belden tells me the
presence of pinholes in the PVC jacket can allow water to enter and
cause corrosion. You can use the teflon plenum cable but it costs $4
per foot. If you have conduit between buildings be sure that water
doesn't condense from the air moving between buildings.

Some electrical codes require a cable to be grounded at one point in
each building. DEC recommends this. If this causes ground loop
problems, then you can not run Ethernet coax trunk cable between
buildings.

Our production Ethernet does not use coax between buildings, although
we have an experimental Ethernet which does and works fine. For now.

By the way, why do people feel compelled to post on things they know
nothing about?
-- 
 Vote Yes on Proposition 51!

 Phil Ngai +1 408 749 5720
 UUCP: {ucbvax,decwrl,ihnp4,allegra}!amdcad!phil
 ARPA: amdcad!phil@decwrl.dec.com

Digital makes two products you may be interested in:

1:  Ethernet Repeater (DEREP) and

2:  Lan Bridge 100 (DEBET).

Both have options which allows two of them to be connected together
with a fiber cable forming a single "virtual" repeater.

The difference is that the DEREP blindly repeats all packets onto both
sides, while the DEBET only passes packets that are aimed for the
other segment.  In another words, the DEBET is sort of like a ethernet
level gateway.  The net will appear as one to higher levels, but the
segments will have reduced load.

I am told there are other manufacturers of similar products.  I have
no experience with either yet, although I am about to install 8
DEREPS.  Amusingly enough, they were aquired from Hewlett Packard as
part number 92223A.  When the units arrived they looked uncomfortably
familiar (anyone who owns lots of dec equipment will recognize a DEC
enclosure anywhere), so I (well, actually, someone else beat me to
it) peeled off the HP label and it said DIGITAL DEREP underneath.  The
trancievers were also DEC H4000's with a label covering the name and
part number.

-Henry