> # About Reordering PortChannel Frames

> When a link change occurs in a PortChannel, the frames for the same exchange or the same flow can switch from one path to another faster path.

> The in-order delivery feature attempts to minimize the number of frames dropped during PortChannel link changes when the in-order delivery is enabled by sending a request to the remote switch on the PortChannel to flush all frames for this PortChannel.

> Note Both switches on the PortChannel must be running Cisco SAN-OS Release 3.0(1) for this IOD enhancement. For earlier releases, IOD waits for the switch latency period before sending new frames.

> When the in-order delivery guarantee feature is enabled and a PortChannel link change occurs, the frames crossing the PortChannel are treated as follows:

> - Frames using the old path are delivered before new frames are accepted.
> - The new frames are delivered through the new path after the switch latency drop period has elapsed and all old frames are flushed.

> Frames that cannot be delivered in order through the old path within the switch latency drop period are dropped. See the "Configuring the Drop Latency Time" topic.

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