Path Selection And Isl Loading; Example Of Multiple Hops - EMC Connectrix EC-1200 Planning Manual

Path Selection and ISL Loading

Example of Hops
Figure 2-5
Connectrix Directors and switches use a number of algorithms to
distribute the load over a set of ISLs. These algorithms include:
Shortest Path First
Multiple Equal-Cost Paths
Load Assignment on World Wide Node Names
The ANSI standard for routing in a Fibre Channel fabric is Fibre
Channel Shortest Path First (FSPF). This standard measures routing
cost in terms of the number of hops a frame must take from its source
to its destination.
A hop is a direct path between two switches with no other switches in
between. A link between an end device and a switch does not count
as a hop.
Server Switch
X A
Server X to Storage D = 1 Hop
Server X to Storage E = 2 Hops

Example of Multiple Hops

The FSPF algorithm creates routes of minimum cost throughout the
fabric. Every entry port into a switch has a designated exit for each of
the possible destinations. These exit assignments change only if there
is a reconfiguration event in the fabric. This single-static exit ensures
in-order delivery of the frames within an exchange. If an ISL or a new
switch is added or removed, the assignments may change. These
assignments are done with logged-in N_Ports. No routing
assignments are done for F_Ports that have no logged-in ports.
Fibre Channel Switching Concepts
Switch Storage
B D
Storage
E

Path Selection and ISL Loading

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