Fabric OS Administrator's Guide v7.0.0 (53-1002148-02, June 2011)

448 Fabric OS Administrator’s Guide
53-1002148-02
Extended Fabrics device limitations
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Extended Fabrics device limitations
Extended Fabrics is not supported on the following devices:
• FC8-64 port blade
• Brocade 8000 FCoE switch
Long distance link modes
Use the portCfgLongDistance command to support long distance links and to allocate sufficient
numbers of full size frame buffers on a particular port. Changes made by this command are
persistent across switch reboots and power cycles. This command supports the following
long-distance link modes:
• Static Mode (LO) - L0 is the normal (default) mode for a port. It configures the port as a regular
port. A total of 20 full-size frame buffers are reserved for data traffic, regardless of the port
operating speed; therefore, the maximum supported link distance is up to 5 km at 2 Gbps, up
to 2 km at 4 Gbps, and up to 1 km at 8, 10, and 16 Gbps.
• Static Mode (LE) - LE configures an E_Ports distance greater than 5 km and up to 10 km. LE
does not require an Extended Fabrics license. The baseline for the calculation is one credit per
km at 2 Gbps. This yields the following values for 10 km:
- 5 credits per port at 1 Gbps.
- 10 credits per port at 2 Gbps.
- 20 credits per port at 4 Gbps.
- 40 credits per port at 8 Gbps.
- 50 credits per port at 10 Gbps
- 80 credits per port at 16 Gbps
• Dynamic Mode (LD) - LD calculates BB credits based on the distance measured during port
initialization. Brocade switches use a proprietary algorithm to estimate distance across an ISL.
The estimated distance is used to determine the BB credits required in LD (Dynamic) extended
link mode based on a maximum Fibre Channel payload size of 2,112. You can place an upper
limit on the calculation by providing a desired_distance value. Fabric OS confines user entries
to no larger than what it has estimated the distance to be. When the measured distance is
more than desired_distance, the desired_distance (the smaller value) is used in the
calculation.
• Static Long-Distance Mode (LS) - LS calculates a static number of BB credits based only on a
user-defined desired_distance value. LS mode also assumes that all FC payloads are 2112
bytes. Specify LS mode to configure a static long distance link with a fixed buffer allocation
greater than 10 km. Up to a total of 1452 full-size frame buffers are reserved for data traffic,
depending on the specified desired_distance value.
Configuring an extended ISL
Before configuring an extended ISL, ensure that the following conditions are met:
• The ports on both ends of the ISL are operating at the same port speed, and can be configured
at the same distance level without compromising local switch performance.