Conference 7.286::fddi

490.0. "Update on copper FDDI (TP-PMD)" by LEVERS::B_CRONIN () Wed Mar 04 1992 15:06

    For those who are wondering, here is what happened at the last TP-PMD
    meeting, on Feb 19 1992, in Austin TX.
    
    The committee decided to develop a standard for 150 ohm STP and 100
    Ohm Category 5 UTP. Datagrade UTP is a name frequently used as a 
    synonym for Category 5 cable. The category refers to the EIA/TIA 
    categorization of the cable. The committee has spent the last 4 months
    looking at whether it is possible to develop a satisfactory standard
    for more than the two cable types, and has decided that it is not possible
    at this time, so forward progress should be made. 
    
    The committee also decided that it should continue to hear information
    on the results of work being done to run FDDI over EIA/TIA category 3 
    cables. These are the type of cables specified for 10Base-T installations. 
    This is in response to the desire to develop a good standard for those 
    cables; good meaning that it can support 100 meter distances, have good 
    error rates, etc, etc, etc. Such a standard will probably require
    digital signal processing chipsets. There is still a lot of preliminary
    work to be done in this area. 
    
    The committee hopes to be able to choose the encoding technique for the
    STP/Category 5 standard at its next meeting. The choice will be between 
    the MLT-3 and pre-emphasized NRZI coding schemes, unless someone shows 
    up with something of such importance that people vote for it. After the
    coding is chosen, the committee will move on to the details of
    scrambling, connectors, etc. While the goal is to try to get a standard 
    ballotted by December 1992, this is becoming less likely. I won't
    hazard a guess as to when a standard will be ready, but I don't expect 
    it to be too much of a slip beyond December. 
    
    

A couple of customers have asked about our current ST offering inlight of
this standard. Obviously we will adher to the final standard but what sort 
of changes will this necesitate on our ST card ??

    Its too early to guess. Basically, we will need to redesign the
    existing stp card. (I assume here that you meant STP, not ST as in
    optical connector). 

    
    Hi,
    
    We are now helping some of our customers to plan their cabling network
    and they are very interested in FDDI on UTP.  Implementation will be
    started by the end of this year.
    
    Do you think level 5 UTP is a good choice for them ?  Fiber is not
    acceptable as it is too expensive.
    
    Thanks.
    
    Kin 

    Here's what you want to tell the customer. 
    
    1) The copper FDDI standard will be using category 5 cable, so they
    will be consistent with the standard's requirements for UTP cable. 
    Category 5 is the best choice for a UTP cable. 
    
    2) If their installation is prone to excessive noise hits, then they 
    will still have a chance that FDDI on copper wouldn't work for them, 
    even with the category 5 UTP. The actual numbers are still being
    developed, so I can't yet tell you how to test for this. But, keep in 
    mind that link error rates of 1E-12 correspond to one bit in error
    every three hours, per link. 
    
    3) Now, if they are in the typical edge city office environment, they 
    will probably be safe. BUT, at this point we are not just blanketly
    telling people to pull in the category 5 cable. As soon as the noise
    numbers can be explained, we can tell people what environments will or
    won't work. In the meantime, they need to make their own call.