Cisco Nexus 5000 Series Switch Fabric Manager Software Configuration Guide, NX-OS 4.0 (OL-16598-01, June 2008)

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18-13
Nexus 5000 Series Switch Fabric Manager Software Configuration Guide
OL-16598-01
Chapter 18 Configuring Fibre Channel Routing Services and Protocols
In-Order Delivery
Use IOD only if your environment cannot support out-of-order frame delivery.
Tip If you enable the in-order delivery feature, the graceful shutdown feature is not implemented.
This section includes the following topics:
• About Reordering Network Frames, page 18-13
• About Reordering SAN Port Channel Frames, page 18-13
• About Enabling In-Order Delivery, page 18-14
• Enabling In-Order Delivery Globally, page 18-15
• Enabling In-Order Delivery for a VSAN, page 18-15
• Configuring the Drop Latency Time, page 18-15
About Reordering Network Frames
When you experience a route change in the network, the new selected path may be faster or less
congested than the old route.
Figure 18-11 Route Change Delivery
In Figure 18-11, the new path from Switch 1 to Switch 4 is faster. In this scenario, Frame 3 and Frame
4 may 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.
About Reordering SAN Port Channel Frames
When a link change occurs in a SAN port channel, the frames for the same exchange or the same flow
can switch from one path to another faster path.
Switch 1 Switch 2 Switch 3
Switch 4
Frame 2 Frame 1
Frame 4 Frame 3
Old path
New path
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