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Conference netcad::hub_mgnt

Title:DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:NETCAD::COLELLADT
Created:Wed Nov 13 1991
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:4455
Total number of notes:16761

952.0. "DB900MX and Full Duplex Mode" by DPDMAI::DAVIES (Mark, SCA Area Network Consultant) Mon May 02 1994 18:24

    A simple question, I hope.
    
    1. Does the DECbridge 900MX support Digital Full Duplex mode on the
       FDDI ports.
    
    Thanks,
    
    Mark
    
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952.1LEVERS::ANILTue May 03 1994 18:565
    Not in the first release, but the intent is to support this in a
    future one.  I'm curious why this would be considered useful given
    that the max forwarding throughput is 60 Mbps (6 Ethernets)?
    
    Anil
952.2ThanksDPDMAI::DAVIESMark, SCA Area Network ConsultantThu May 05 1994 09:407
    Just a question from a customer who had just been given a GIGAswitch
    and FDDI presentation and they were on a Full Duplex "feeding frenzy".
    
    Thanks,
                                                             
    Mark
    
952.3STRWRS::KOCH_PIt never hurts to ask...Thu Mar 09 1995 11:2611
    Did we ever get FFDT for the DECswitch 900EF or PEswtich 900TX?
    
    The question came up in that we realize that thruput wouldn't be
    affected, but could latency be cut down if full duplex was turned on. I
    am of course also assuming a point-to-point link between a GIGAswitch
    port and DECswitch 900EF port.
    
    Does it even make sense?
    
    If not, if we do support it, why don't we have higher density switches
    to fully load the FDDI pipe?
952.4FDX Ethernet on Switches?TRUCKS::EVANS_MAIt's all out there somewhere!Tue Mar 21 1995 09:348
>    Did we ever get FFDT for the DECswitch 900EF or PEswtich 900TX?
>    

Knowing this to be a yes, will the switches have FDX Ethernet capability in the
not too distant future, to link with the FDX NICs (DE425/DE435) we already
ship?

Regards, Martin
952.5Full Duplex SupportDELNI::PIEPERWed Apr 05 1995 11:2212
    The current DECswitch 900EF and PEswitch 900TX do support Full Duplex
    FDDI connections but I'm not sure what benefit you will gain.  While
    the latency will be lower, the latency due to the rotation of the token
    on FDDI is negligible compared to the "delay" of getting a packet to or
    from FDDI to Ethernet (the "delay" is equal to one packet length plus
    the latency of the store and forward switch (aka bridge))  So worrying 
    about the advantage of Full Duplex FDDI connection to the switches is
    like worrying about an inch when you've missed the target by a yard!
    
    There is no plan to support Full Duplex Ethernet on the current
    switches - it would require hardware changes.  But future switches will
    support Full Duplex Ethernet connections.
952.6Negotiation or dip switch?NAC::LICAUSESat May 13 1995 19:0413
    When both sides are full duplex capable, will there be some form of
    negotiation that will take place or must everyone make certain that
    they have set their dip switches correctly?
    
    If the later, how will one be able to determine if this capability has
    been setup correctly on either side?
    
    I can see the hotline lighting up now with questions about "my
    throughput isn't what I expect and I just know I have a full 
    duplex interface....."
    
    Al