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96257 Sun Confidential: Internal Only B-81
Revision A
McData/CNT Channel Extension Interoperability
■ McData/CNT Channel Extension Interoperability
The following interoperability and configuration information and guidelines apply when us-
ing McData/CNT USD-X and Edge3000 channel extenders with a VSM-VTSS.
Set Buffer-to-Buffer Credits at Director Ports
In FICON fabric topology, configure buffer-to-buffer (BB) credits on all director ports that
are part of all channel-extended end-to-end paths to ‘extended distance’, i.e.,
≥ 60 BB
credits. This includes host ports, CU ports, and ISL
1
ports that carry I/O on a channel-ex-
tended path, regardless of which link is physically extended. For example, consider a sin-
gle director configuration with three CHPIDs configured to perform I/O with two CU ports,
where one CU port is channel-extended. In this case, four director ports should have their
BB credits set to ‘extended distance’: Each of the three F_Ports attached to the three
hosts, and the F_Port attached to the extension equipment that extends to the CU port.
Set Extension-Attached Director Ports to Fixed Speeds
When channel extension is added to a FICON link, the result is two FICON links which are
coupled by the two channel extension chassis through a WAN. The link speed setting on
at least one side of the pair of FICON links must be set to a fixed speed to avoid exposure
to an issue where the link may not initialize once a fibre/SFP
2
cable is attached, or where
the link may not reinitialize after a loss of synchronization during operations.
Figure B-6. VTSS-to-VTSS Channel Extension – Between Cascaded FICON Switches / Directors
Channel
Extender
CLINKs
CLINKs
Channel
Extender
A502
_
053
z/OS
Host
Local
Clustered
VTSS
Remote
Clustered
VTSS
Local
Tape Silo
Remote
Tape Silo
with RTDs
Channel
Extender
FI
CO
N
Director/Switch
FI
CO
N
Director/Switch
1. Inter-switch link; the fibre channel link providing connectivity between two switches
2. Short form factor pluggable connectors