Open trunking – HP StorageWorks 2.140 Director Switch User Manual
Page 210
Optional Features
208
Director Element Manager User Guide
Open Trunking
Interswitch links (ISLs) connect ports between E_Ports on Fibre Channel switches
and link these switches into a multiswitch fabric. Multiple ISLs may be connected
between the switches in the fabric. Data from an attached end device (server or
storage) flows through these ISLs to a target end-device connected to a switch
somewhere in the fabric. A data flow is data received from a specified receive port
that is destined for a port in a specified target domain (switch). The list of ISLs
that are candidates for being rerouted (to or from) is derived from the fiber
shortest path first (FSPF) algorithm.
The Open Trunking feature monitors the average data rates of all traffic flows on
ISLs (from a receive port to a target domain), and periodically adjusts routing
tables to reroute data flows from congested links to lightly loaded links and
optimize bandwidth use. The objective of Open Trunking is to make the most
efficient possible use of redundant ISLs between neighboring switches, even if
these ISLs have different bandwidths.
Load-balancing among the ISLs does not require user configuration, other than
enabling Open Trunking. However, if desired, you can modify default settings for
congestion thresholds (per port) and low BB_Credit threshold.
In particular, you do not need to manually configure ISLs into trunk groups of
redundant links where data can be off-loaded. Candidate links for rerouting flow
are identified and maintained automatically. This means that flow may be rerouted
onto a link that goes to a different adjacent switch, as long as that link is on the
least cost/shortest path to the destination domain ID.
To install and enable this option, choose the Configure Feature Key option under
the Element Manager’s Configure menu. See “