Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!purdue!bu-cs!kwe
From: kwe@bu-cs.BU.EDU (kwe@bu-it.bu.edu (Kent W. England))
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet across the street
Message-ID: <38223@bu-cs.BU.EDU>
Date: 15 Sep 89 15:39:46 GMT
References: <2335@optilink.UUCP>
Reply-To: kwe@buit13.bu.edu (Kent England)
Followup-To: comp.dcom.lans
Distribution: na
Organization: Boston U. Information Technology
Lines: 57

In article <2335@optilink.UUCP> brad@optilink.UUCP (Brad Yearwood) writes:
>
>In the near future, we will be expanding operations into a second building
>located about 300 meters away, across a city street from our present
>location.  Both properties would be leased from the same owner.
>
>We would like to extend our Ethernet between the two buildings.  I
>foresee much of the traffic being NFS, which seems to argue for a
>10Mbit/sec facility rather than a bridge to something slower, like T1.
>
	10M is definitely feasible, but which technique?  See below.

>  1.  Run fiber optic cable under the street.  Does anybody know
>      what sort of permissions and processes would be necessary to
>      do this, or is it something that only Pacific Bell can do?

	In Boston, anyone can run a conduit if they coordinate with
the Public Improvement Commission.  The PIC wants to minimize the
street disruption, so they require you to ask their list of concerned
companies and accept anyone else's need for conduit in the area.  For
us, this means we can piggyback on the phone company's construction.
This is very useful.
	You might be able to rent duct from Pac Bell.  It depends on
their policy.
>
>  2.  Use an air path laser system.  This area gets fairly dense fog from
>      maybe 10PM-10AM several weeks of the year - is this likely to disable
>      the link?
>
	300 meters sounds reasonable but fog could be a problem.  You
would need to get a commitment from a vendor, but it is worth
pursuing.  There is no license required, or even roof access.  You can
shoot these things thru windows.  Chances are that the fog would be
temporarily disruptive and might be acceptable, so long as the link
comes back automatically.  Beware of equipment that does not squelch
noise when the carrier is lost.  This can cause grief in the Ethernet,
so this should be tested before acceptance.  Note that I am not saying
this is a problem, just that I wonder about how the vendors deal with
carrier loss.  No such problem in regular Ethernet.

>  3.  Use a microwave system.  Would dense fog disable microwave (maybe at
>      23GHz)?  What are the licensing issues?
>
	23GHz Microwave would work well.  You should find a vendor
that does turnkey installation, including the requisite FCC licensing.
Microwave Bypass of Braintree, MA sells Ethernet on microwave, so you
aren't limited to T1 anymore.  There are some other vendors, but I am
not aware of any other turnkey vendors of Ethernet-on-microwave.
Enlighten me.  :-) Licensing is not a bad thing.  If someone builds
something in your way, your FCC license requires them to accomodate
you.  Infrared does not require a license, so you are out of luck if
something "pops up" one day.

	So, the good news is; you have lots of options.  The bad news
is; you have to pick one.    :-)

	Kent England, Boston University