Conference netcad::hub_mgnt

1116.0. "DECbridge 900MX redundancy validity check" by NWD002::KOPEC_ST (Squash:Racketball::Chess:Checkers) Tue Jun 14 1994 13:09

I have a customer who is very interested in the DECbridge 900MX product and 
wanted to verify the following config and get his question answered on 
spanning tree failover time (see bottom of note) before he put the money in 
the budget for FY95.  The potential for Digital product here is high as they 
must have redundancy throughout their plant.

					Thank You, Stan



			============FDDI ring==================
			"				      "
DEChub 900 with DECbridge 900MX		DEChub 900 with DECbridge 900MX
                 !	!				  !     !
		 !	-----------------		  !     !
		 !			!		  !     !
		 !	    -------------------------------     !
                 !	    !		!			!		
-----------------*----------*--		*-----------------------*-------
	Ethernet LAN 1				Ethernet LAN 2


DEChub #1 has 1 DECbridge 900 MX 
DEChub #2 has 1 DECbridge 900 MX

Ethernet LAN 1 is an existing thickwire & contains 6 very essential 
devices in a lab.

Ethernet LAN 2 is also an existing thickwire & contains 6 other very essential 
devices in the same lab.

LAN 1 and LAN 2 are tapped into an AUI port on each of the 2 DECbridges via a 
simple transceiver cable and H4005 transceiver on the thickwire 
(H4005's are depicted by the four *'s above).

The DECbridges are connected via a physical dual counter rotating ring 
running FDDI, using their front panel A/B ports.

High speed Alpha systems will be directly connected to this physical FDDI 
ring via DECconcentrators (which are not pictured here).  Thus, the Alphas 
will not be directly connected to the ring, but rather will connect to the M 
ports of the concentrator.  The concentrators will connect to the FDDI ring 
via its A and B ports.

It is essential that both "LAN 1 to LAN 2 connectivity" as well as 
"LANs 1/2 to Alpha connectivity" is fully redundant.

The questions are:
------------------
1) Is this config valid?
   It certainly seems to meet the redundancy criteria.

2) In the case of a DECbridge 900 MX going bad, what would be the estimated 
   spanning tree reconfiguration time before the above stated 
   connectivity requirements were back online?

    This is perfectly valid configuration (one might even be tempted to
    call it a 'classic' :-).
    
    The failover time is a function of the configuration of some of the
    bridge parameters - what is the requirement?

    The failover default parameter times are for the Listen Time and
    Forwarding Delay. These I believe default to 15 seconds for
    Listen Time and 30 seconds for Forwarding Delay. So the redundant
    bridge will by default probably take 45 seconds to take over.
    The Listen time must be greater than (4X Hello Interval) + (maximum
    delay
    in network). The Forwarding Delay must be greater than or equal to
    (Listen Time) + (maximum delay in network)
    So I believe these parameters can be tuned to a specific network
    config.
    
    Bob