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Configuring Fibre Channel Routing Services and Protocols
Some Fibre Channel protocols or applications cannot handle out-of-order frame delivery. In these cases, Cisco
SAN switches preserve frame ordering in the frame flow. The source ID (SID), destination ID (DID), and
optionally, the originator exchange ID (OX ID) identify the flow of the frame.
On a switch with IOD enabled, all frames received by a specific ingress port and destined to a certain egress
port are always delivered in the same order in which they were received.
Use IOD only if your environment cannot support out-of-order frame delivery.
If you enable IOD, the graceful shutdown feature is not implemented.
Reordering Network Frames
When you experience a route change in the network, the new selected path might be faster or less congested
than the old route (See the following figure).
Figure 39: Route Change Delivery
In the figure above, the new path from Switch 1 to Switch 4 is faster. In this scenario, Frame 3 and Frame 4
might be delivered before Frame 1 and Frame 2.
If the in-order guarantee feature is enabled, the frames within the network are delivered as follows:
• Frames in the network are delivered in the order in which they are transmitted.
• Frames that cannot be delivered in order within the network latency drop period are dropped inside the
network.
OL-30895-01
Cisco Nexus 5500 Series NX-OS SAN Switching Configuration Guide, Release 7.x
In-Order Delivery
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