Brocade Fabric OS Administrators Guide (Supporting Fabric OS v7.3.0) - Manual (Page 113)

3. If IOD is enabled, waits for sufficient time for frames already received to be transmitted. This is
needed to maintain IOD.
4. Resumes traffic.
The following table shows the effect of frames when you have a specific routing policy turned on with
IOD.
Combinations of routing policy and IOD with Lossless DLS enabled TABLE 14
Policy IOD Rebalance result with Lossless DLS enabled
Port-based Disabled No frame loss, but out-of-order frames may occur.
Port-based Enabled No frame loss and no out-of-order frames. Topology restrictions apply. Intended for
FICON environment.
Exchange-based Disabled No frame loss, but out-of-order frames may occur.
Exchange-based Enabled No frame loss and no out-of-order frames. Topology restrictions apply. Intended for
FICON environment.
Device-based Disabled No frame loss, but out-of-order frames may occur.
Device-based Enabled No frame loss and no out-of-order frames. Topology restrictions apply. Intended for
FICON environment.
NOTE
Not only the link cost has influence to DLS but the order of ports that become online, and speeds of
each E_port/F_port also have impact on how the switch calculates or chooses the path using DLS.
Lossless core
Lossless core works with the default configuration of the Brocade DCX 8510-8 and DCX 8510-4
hardware to prevent frame loss during a core blade removal and insertion. This feature is on by default
and cannot be disabled. Lossless core has the following limitations:
• Only supported with IOD disabled, which means Lossless core cannot guarantee in-order delivery of
exchanges
• ICL limitations
• Traffic flow limitations
ICL limitations
If ICL ports are connected during a core blade removal, it is equivalent to removing external E_Ports
which may cause I/O disruption on the ICL ports that have been removed.
If ICL ports are connected during a core blade insertion, it is equivalent to adding external E_Ports
which may cause I/O disruption because of reroutes. Lossless DLS, if enabled, takes effect to prevent
I/O disruption.
Traffic flow limitations
FA4-18 AP blades, which are supported on the Brocade DCX and DCX-4S devices, may continue to
experience frame drops after core blade removal or insertion. The path between an FA4-18 blade and
Lossless core
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