Administering Extended Fabrics; About Extended Link Buffer Allocation - HP A7533A - Brocade 4Gb SAN Switch Base Administrator's Manual

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Administering Extended Fabrics

This chapter contains procedures for using the Extended Fabrics licensed feature, which extends the
distance that interswitch links (ISLs) can reach over a dark fiber or DWM connection. The Extended Fabrics
feature is not used over FCIP connections over IP WANs. To use extended ISL modes, you must first install
the Extended Fabrics license. For details on obtaining and installing licensed features, refer to
"Maintaining licensed software

About extended link buffer allocation

As the distance between switches and the link speed increases, additional buffer-to-buffer credits are
required to maintain maximum performance. The number of credits reserved for a port depends on the
switch model and on the extended ISL mode for which it is configured.
For the following switches, each port group contains four ports and uses a common pool of credits.
• 4/8 SAN Switch or 4/16 SAN Switch
• MSA SAN Switch 2/8
• SAN Switch 2/8 EL
• SAN Switch 2/8V
• SAN Switch 2/16V
• SAN Switch 2/32
• Core Switch 2/64
• SAN director 2/128
Because the number of credits available for use within each port group is limited, configuring ports for
extended links on these models might cause other ports to become disabled if there are not enough buffer
credits available; for example:
• If two 2-Gbps ports in a group are configured for L1 mode, each will be allocated enough
buffer-to-buffer credits to cause the other two ports in the group to become disabled.
• A port connected to a device that is in loopback mode might become disabled for lack of buffers if
another port in that group is set to L2 mode.
For the following switches, each port group contains eight ports and uses a common pool of credits.
• Brocade 4Gb SAN Switch for p-Class BladeSystem
• Brocade 4Gb SAN Switch for c-Class BladeSystem
• SAN Switch 4/32
• 4/64 SAN Switch
• 4/32B SAN Switch
• 400 Multi-protocol Router
• 4/256 SAN Director, using the following port blades:
• FC4- 1 6
• FC4- 1 6IP
• FC4-32
• FC4-48
• FR4- 1 8i
features" on page 36.
Fabric OS 5.3.0 administrator guide 351