FICON Administrator's Guide v6.4.0 (53-1001771-01, June 2010)

FICON Administrator’s Guide 41
53-1001771-01
Configuration requirements for switches and directors
4
Configuration of sufficient buffer credits
The 7500 defaults to 8 BB credits per port. If the performance for a specific port is not sufficient
for FICON, increasing the BB credits can improve performance. It is recommended that FICON ISLs
or CHPID ports should be configured to 16 BB credits or greater.
High integrity fabric requirements for cascaded configurations
Extended FICON connections between or through Brocade 7500,7800 SAN routers or FR4-18ior
FX8-24 blade Ethernet interfaces to create a cascaded FICON switched configuration. The fabric
must be set up to provide a secure, or high integrity, fabric to enable this configuration to operate in
an IBM environment. See Chapter 2, “Administering FICON Fabrics” for an explanation of these
requirements.
FICON emulation requirement for a determinate path
FICON emulation processing creates FICON commands and responses on extended CHPIDs, and
intercepts all exchanges between a channel and a CU. For FICON Emulation processing to function
correctly, all the exchanges between a channel and CU must take a single GE tunnel path.
There are two ways to ensure a determinate path for FICON commands and responses:
• Define only one IP route and one FCIP tunnel between sites.
• Use a Traffic Isolation zone (TI zone) to assign a specific GE tunnel to Channel and control unit
ports.
FCIP tunnel between sites
The Brocade 7800 and FX8-24 uses FCIP Trunking features to overcome the limitation of one
Ethernet interface, one IP address and one FCIP tunnel. In Fabric OS v6.3 and later an FCIP Tunnel
is created with multiple FCIP circuits over different IP interfaces to provide WAN load balancing and
failover recovery in the event of a limited WAN outage. This provides a highly redundant WAN
configuration for all FICON or FCP emulation technologies with Fabric OS. Figure 13 shows that a
tunnel can have up to 4 circuits per GbE port.
FIGURE 13 FCIP tunnel and circuits