HP StorageWorks 64 - SAN Director Switch Planning Manual page 20

Introduction to HP Fibre Channel Products
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Multiple topology support — Directors support both point-to-point and
multi-switch fabric topologies, and indirectly support arbitrated loop
topology.
— Point-to-point topology provides a single direct connection between two
device N_Ports. This topology supports bidirectional transmission
between source and destination ports. Through dynamic switching,
directors configure different point-to-point transmission paths. In all
cases, connected N_Ports use 100% of the available bandwidth.
— A multi-switch fabric topology provides the ability to connect directors
and edge switches through expansion ports (E_Ports) and interswitch
links (ISLs) to form a Fibre Channel fabric. Directors receive data from a
device, and based on the destination N_Port address, route the data
through the fabric (and possibly through multiple switch elements) to the
destination device.
— An arbitrated loop topology connects multiple device node loop ports
(NL_Ports) in a loop (or hub) configuration without benefit of a
multi-switch fabric. Although directors do not support direct connection
of arbitrated loop devices, such devices can communicate with directors
through loop switches supplied by HP.
Multiple service class support — The Fibre Channel signaling protocol
provides several classes of transmission service that support framing protocol
and flow control between ports. Directors support:
— Class 2 transmission service that provides connectionless multiplexed
frame delivery service with acknowledgment. Class 2 Service is best
suited for mainstream computing applications.
— Class 3 transmission service that provides connectionless, best-effort
multiplexed datagram frame delivery with no acknowledgment. Class 3
service is best suited for mass storage or video applications.
— Class F transmission service that is used by multiple directors to
communicate across ISLs to configure, control, and coordinate the
behavior of a multi-switch fabric.
SAN High Availability Planning Guide