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The following is NOT an "official" answer - and is only for internal use.
As I understand it, the restriction is due to a hardware problem that was only
found recently and a business decision to ship on schedule.
The first units to ship will probably always have the restriction. The nature
of the hardware problem is such that it can't be worked around in firmware, so
any fix would involve upgrading or replacing hardware in the field.
Later units <may> lift this restriction, but I have no idea when.
If you want to know what to tell your customers, ask the product manager. I'm
not sure whether he follows this file.
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It is true that DAHSF is restriction to slots 7,8. Note that earlier
information was incorrect and listed other slots. The main
significance of this restriction is that a maximum of two DAHSF's may
be configureded into a single DEChub backplane. This gives 16 ATM
ports in a DEChub backplane at FRS. This shouldn't be
a major issue as the most interesting configuration is one or two
ATMswitch 900F's connecting a bunch of VNswitch 900's (Enet to ATM)
We can connect > 100 switched 10Mb Enet LAN segments to ATM.
The DAHST will allow additional ATM ports in a backplane.
The following information is for internal use only:
The restriction is necessary due to regulatory issues, not functional
issues. It will be fixed although we plan to issue the DAHST before
eliminating the slot restriction on the DAHSF. The DAHST is
expected to have no restriction.
The DAHSF with a slot restriction does not cause configuration limits
to other DEChub 900 products. DVNEA and DAHST may be placed in any
open slot.
There will be no way to upgrade the current DAHSF in the future
except to swap with the next revision. Contact
the product manager, Bernie Zarin, for more info.
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| Hi,
The restriction was announced at the SE Forum in January (although they gave
us the incorrect information about which slots). The restriction is because
the switch failed FCC tests (can't recall which tests), not because of any
architectural/firmware problem.
The restriction is actually enforced in firmware, that is if you plug it into
any slot other than 7 or 8, it will disable itself. Apparently the module LEDs
will give you some indication of the problem as well.
The restriction is hardly dramatic. In my opinion, no one should ever put
more than 2 ATMswitch 900's in a hub anyway. Remember that this gives you
no more than 14 ATM ports, not 16, since you have to redirect at least one
port on each module (probably more for performance) to the backplane, if you
want the switches to talk to each other. Also, there are only 4 ATM
connections
on the backplane, so you can't possibly connect more than for ATM devices on
the backplane - you'd probably want some VNswitch 900EA's in your hub as well.
If someone needs more than 14 ATM ports, then they should be looking at a
GIGAswitch, which will give you much better performance and scaleability
than a set of ATMswitch 900's in a DEChub 900. As far as I know, the
ATMswitch 900 is NOT intended to replace the GIGAswitch/ATM, and should not
be sold when the GIGAswitch is more appropriate.
Ryan
Network Consultant
NPBU, South Africa
[Posted by WWW Notes gateway]
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