Conference 7.286::fddi

I haven't heard any; do you have people asking for it?

	paul

Probably the first available method of carrying FDDI over a microwave link will
be through an FDDI-to-T3 (DS3) bridge.  There are any number of T3 microwave
products on the market now.

The FDDI-to-T3 device (bridge/router/gateway/...) is on a lot of drawing boards,
and Proteon claims to have one in some of their literature.  I'm pretty leery of
the performance of anything currently available, but have no direct experience.

Paul Knight

I am involved with a five site campus LAN. We are currently looking to install
FDDI backbones in each facility. Two of the facilities are remote and connect 
back to the main facility via Metrowave. As it stands now, the 10mbps link will
probably handle the traffic requirements but may become a bottleneck in the next
6 to 12 months. The bottom line is; Are we planning on providing a migration
path from Metrowave to FDDI? 

Thanks,

Andy

P.S. I have researched installing some SM fiber between the sites. The initial
figures were between $250,000.00 and $400,000.00 depending on the available 
route. Obviously, we would like to be able to re-use our Micro Wave gear...

    It should be possible (I've not tested it) to replace the Lanbridge 100
    in the Metrowave product (DEMWB) by the FDDI DECbridge 500. Since the
    connection between the LB100 and the DEMWA is through a Ethernet drop
    cable replacing one bridge by another should work.
    
    Note that the microwave link will then provide a half-duplex 10Mbps
    bandwidth between 2 FDDI rings. Possible bottleneck.

I, too, have a customer that is currently using a Metro Wave setup to link two
sites. The customer is inquiring about ways to connect the sites with FDDI.
Certainly cost would be a factor but a bigger head ache is the railroad yard
between the two sites. Metro Waves are quite handy for these right of way 
issues. We are actually looking at using the utility poles for stringing up
the fiber.

Any ideas or suggestions would be appreciated.

Rob

    If you can obtain the right-of-way for installing fibre on the utility
    poles then go for it. The key concern is that you use a fibre that is
    suitable for FDDI, as well as being suitable for the spanning the
    distance between poles.
    
    Another alternative to poles would be installing the fibre underground
    (????). 
    
    If you choose to go the fibre route, your NWSS organization should be
    able to help you.
    
    
    John

    Has there been any movement on this ? I have a customer who is
    interested in carrying FDDI over microwave at full transmission 
    speeds. Is this even technically viable ?
    
    Thanks - Francis Bryan (Telco account group - UK)

Sure it's possible in principle, but I don't know if anyone has done it.
What you need is a two-way microwave link that can carry a 125 Mb/s data
stream with a BER of 10^-11 or better, worst case.  The bit error rate
requirement seems like a rather tough one, especially given the associated
data rate requirement.  Also, your favorite government agency in charge of
frequency allocations may not have a wide enough channel to give out; I don't
think that typical microwave allocations come in 150-200 MHz width!  (You can
push that down some but at the expense of complexity and even more trouble
around bit error rate.)

	paul

    The CCIR channel plan for microwave links specify '40 Mhz for 140
    Mbit/s', or minimum 3.5 bit/hz modulation efficiency.
    
    The conclusion is that there is fullduplex equipment available for
    standard phone trunk transmission. Since FDDI could be carried over
    any fullduplex link with suitable error and delay characteristics,
    it should be quite feasible to modify a standard phone-link and
    REDUCE transmission rate from 140 Mbit/sec to FDDI speeds.
    
    My opinion is that it would be a reasonably 'simple' modification,
    provided you can work closely with the mfgr. of the microwave gear.
    
    Gullik
    

Maybe so, but remember that the phone company bit error rate requirements
are a LOT less strict than those for FDDI.  Especially for the complex
modulation required to get the bandwidth you mentioned, I wuld be pessimistic.
If you want to pursue this further, be sure to do a thorough study of
the bit error rates -- both what's promised and what's actually delivered.
Remember to check during rain, fog, and snow (if applicable), not just during
nice weather!

	paul

    Hello,
    
    a big customer of mine would also like to know about the present status
    of FDDI over microwave. 
    In Germany the PTT restricts us to use 38GHZ as carrier. Does anybody
    know about some equipment that would suit this requirement?
    
    Thanks in advance
    
    
    	Ulrich

    Contact Shelly Speer @SNO. He is working on the test site for MDF over
    FDDI over Microwave in Australia. He should be able to give you the
    latest status and microwave vendor name.
    
    Debbie
    

    re .12
    
    The VAXc MDF site in Australia is actually using a T3 microwave link.
    There is a DL3000 for the FDDI to T3 at each site.