HP StorageWorks 1606 Brocade Fabric OS Administrator's Guide v6.3.0 (53-100133 - Page 499

Buffer credit recovery 20 TABLE 89 Configurable distances for Extended Fabrics (Continued) Maximum distances that can be configured assuming 2112 Byte Frame Size Switch/blade model 1 Gbps 2 Gbps 4 Gbps 8 Gbps FC8-48 FR4-18i FS8-18 FX8-24 2461 / 3149 500 3208 2125 1230 / 1574 250 1604 1062 615 / 787 100 802 531 307 / 393 N/A 401 265 NOTE QoS requires an additional 14 buffer credits per active port so maximum supported distances may be lower. The 10 Gbps FC10-6 blade has two port groups of three ports each. For extended ISLs, all buffers available to a group are used to support one port at up to 100 km. To get an estimated maximum equally distributed distance for n number of ports at a particular ("X") speed, divide the 1-port maximum distance of the switch at X speed by n. For example, for three ports running at 2 Gbps on a 300 switch, the maximum equally distributed distance is: 486 / 3 = 164 km. Buffer credit recovery Buffer credit recovery does not require configuration. This feature allows links to recover after R_RDYs are lost when the credit recovery logic is enabled. The buffer credit recovery feature also maintains performance. If a credit is lost, a recover attempt is initiated. During link reset, the frame and credit loss counters are reset without performance degradation. This feature is only supported on E_Ports that are configured for long distance and are connected between the following switch or blade models: • Brocade 300, 5100, 5300, 5410, 5424, 5450, 5480 • FC8-16, FC8-32, FC8-48 If a long-distance E_Port from one of these supported switches or blades is connected to any other switch or blade type, the buffer credit recovery feature is disabled. Virtual E_Ports and Virtual EX_Ports do not support long distance. The buffer credit recovery feature is enabled for the following flow control modes: Normal, Virtual Channel (VC), and Extended VC modes. An FC_Port that supports BB_Credit recovery maintains the following BB_Credit recovery values: • BB_SC_N is the log2 of BB_Credit recovery modules. • BB_RDY_N counts the number of R_RDY primitives received modulo 2BB_SC_N. • BB_FRM_N counts the number of frames received modulo 2BB_SC_N. Fabric OS Administrator's Guide 457 53-1001336-01