Fabric Manager Users Guide, Version 6.1, Revision A - QLogic

3–Fabric Manager Configuration
Configuring the QLogic Fabric Manager
Table 3-7. Sm Multicast Routing Parameters (Continued)
Parameter
Default
Value
Description
MinCostImprovement 50% When using LeastTotalCost or
LeastWorstCaseCost, the MinCost-
Improvement parameter controls when
the multicast spanning tree root should
be changed if there are changes in the
number of switches in the fabric. The root
will be changed only if in the new topology
a switch's cost is MinCostImprovement
(expressed as a percentage)
better than that of the current root switch
or when the current root switch goes
offline.
A higher value of MinCostImprovement
would result in the multicast spanning
tree root not being changed too
frequently and therefore would cause
less disruptions in multicast traffic. A
smaller value would select the best
switch and provide better multicast
latency but can cause disruptions to multicast
traffic upon fabric changes.
Fabric Multicast MLID Sharing
IPv6 (and possibly other applications) can create numerous Multicast groups.
Each Multicast group needs an MLID.
In the case of IPv6, there is one Solicited-Node multicast group per CA port. This
results in an excessively large number of multicast groups. Also in large fabrics,
this quickly exceeds MLIDTableCap. To address this situation, the MLIDShare
fields allow groups of Multicast GIDs to share a limited number of MLIDs. This can
conserve the Hardware MLID tables so other uses of Multicast can be optimized
and efficient.
the MLIDShare fields allow specification of 32 separate groups of MGIDs. Each
group of MGIDs are combined into its own unique set of MLIDs. Each MGID is
ANDed with MGIDMask then compared to MGIDValue. On a match the MGID will
be given a MLID within a pool of MaxMLIDs.
MGIDs are 128 bits specified as two colon separated, 64-bit values, IPv6
Solicited-Node multicast, combined to 500 MLIDs
#SM_0_mcastGrpMGidLimitValue_0#!
IB0054608-01 B 3-25