HP StorageWorks 2/140 FW 08.01.00 McDATA Products in a SAN Environment Plannin - Page 111

Planning Considerations for Fibre Channel Topologies 3 ATTENTION ! Activating a preferred path can result in receipt of out-oforder frames if the preferred path differs from the current path, if input and output (I/O) is active from the source port, and if congestion is present on the current path. A rerouting delay parameter can be enabled at the Element Manager application to ensure a director or switch provides correct frame order delivery. The delay period is equal to the error detect time out value (E_D_TOV) specified in the Element Manager application. Class 2 frames transmitted into the fabric during this delay period are rejected; Class 3 frames are discarded without notification. By default, the rerouting delay parameter is disabled. NOTE: To prevent E_Port segmentation, the same E_D_TOV and resource allocation time out value (R_A_TOV) must be specified for each fabric element. • E_Port segmentation - When an ISL activates, the two fabric elements exchange operating parameters to determine if they are compatible and can join to form a single fabric. If the elements are incompatible, the connecting E_Port at each director or switch segments to prevent the creation of a single fabric. A segmented link transmits only Class F traffic; the link does not transmit Class 2 or Class 3 traffic. The following conditions cause E_Ports to segment: - Incompatible operating parameters - Either the R_A_TOV or E_D_TOV is inconsistent between the two fabric elements. - Duplicate Domain_IDs - One or more Domain_ID conflicts are detected. - Incompatible zoning configurations - Zoning configurations for the two fabric elements are not compatible. For an explanation, refer to Configuring Zones. - Build fabric protocol error - A protocol error is detected during the process of forming the fabric. - No principal switch - No director or switch in the fabric is capable of becoming the principal switch. Planning Considerations for Fibre Channel Topologies 3-27