SECURING FIBRE CHANNEL FABRICS - Brocade

FC Fabric Features and ServicesWhen paths with equal costs are available, paths are assigned in a roundrobinfashion. Say that two paths are available between three hosts on aswitch to the disk storage on another switch. The first host will beassigned one path, the second the other path, and the third will roundrobinback to the first path. The Brocade implementation of this feature iscalled Dynamic Load Sharing (DLS). DLS does not use active load feedback,so the paths remain fixed regardless of the load on the link.Exchange-Based Routing or DPSOnce a path is determined for a connection between two devices byFSPF, it does not change until the devices log in once again. This maycause load balancing issues in which one path approaches saturationand other available paths carry almost no load. Exchange-based routingimproves load balancing over FSPF by sending an entire exchange,sequence of FC frames, through the most efficient path. An entire conversationthat consists of several exchanges can be transmittedthrough different paths. The Brocade implementation of this feature iscalled Dynamic Path Selection.TrunkingThe term trunking refers to consolidating several links into one linkresulting in a higher-bandwidth link. In the LAN world, trunking is oftenused to consolidate several ports on a network interface card (NIC)card to provide a larger pipe, or trunk, to the switch. In the FC world,trunking currently applies only in the consolidation of ISLs betweentwo switches. Trunking can be implemented in several ways and someFC switch vendors actually use the term “trunking” for exchange-basedrouting, which can be very confusing.Brocade implements trunking at the ASIC level in the hardware, whichwe believe is the only way to truly implement trunking. Hardware-basedtrunking takes load balancing to the highest level by providing thecapability to spread frames across multiple links simultaneously andobtain the best load balancing across available links.Frame RedirectionIn Brocade FOS 5.3 and M-Enterprise OS (M-EOS) 9.8, Brocade introduceda new technology with the capability to redirect frames using adifferent route than originally intended. This technology was necessaryto add a virtualization layer for certain types of applications that wouldnot normally be in the direct data path in the fabric. The Brocade DataMigration Manager (DMM) and EMC RecoverPoint, both of which runon the Brocade 7600 Application Platform, essentially behave as appliancesin a fabric, and frames need to be redirected through thesedevices to perform their intended function. The Brocade encryptionSecuring Fibre Channel Fabrics 33