Dell PowerConnect Brocade 300 Fabric OS Administrator's Guide v7.1.0 - Page 553

Configuring an extended ISL 23 • Dynamic Mode (LD) - LD calculates buffer 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 buffer credits required in LD (dynamic) extended link mode based on a maximum Fibre Channel payload size of 2,112 bytes. 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 the specified desired distance, the desired distance (the smaller value) is used in the calculation. • Static Mode (LS) - LS calculates a static number of buffer 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. 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 for the same distance_level without compromising local switch performance. NOTE A long-distance link also can be configured to be part of a trunk group. Two or more long-distance links in a port group form a trunk group when they are configured for the same speed and distance, and their link distances are nearly equal. For information on trunking concepts and configurations, refer to Chapter 22, "Managing Trunking Connections". • Only qualified Brocade SFPs are used. Only Brocade-branded or certain Brocade-qualified SFPs are supported. 1. Connect to the switch and log in using an account assigned to the admin role. 2. Enter the switchDisable command. 3. Enter the configure command to set the switch fabric-wide configurations. You can set the following fabric-wide settings: (* = multiplication symbol) Field Domain R_A_TOV E_D_TOV WAN_TOV MAX_HOPS Type Number Number Number Number Number Default 1 10000 2000 0 7 Range Varies E_D_TOV * 2 to 120000 1000 to R_A_TOV/2 0 to R_A_TOV/4 7 to 19 4. For 8-Gbps platforms only, enter the portCfgFillword command to set ARB as the fill word. portcfgfillword [slot/]port, mode The mode parameter in this command should be set to 3 if the vc_translation_link_init parameter in the portCfgLongDistance command (in the next step) is set to 1. 5. Enter the portCfgLongDistance command. Fabric OS Administrator's Guide 553 53-1002745-02