Reordering Network Frames; Reordering Portchannel Frames - Cisco DS-X9530-SF1-K9 - Supervisor-1 Module - Control Processor Configuration Manual

Chapter 21 Configuring Fibre Channel Routing Services and Protocols
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m .
Some Fibre Channel protocols or applications cannot handle out-of-order frame delivery. In these cases,
switches in the Cisco MDS 9000 Family 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.
In case of a single switch, 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.
Tip If you enable the IOD feature, the graceful shutdown feature is not implemented.

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 (see
Figure 21-5
Switch 1
In Figure
delivered before Frame 1 and Frame 2.
If the in-order guarantee feature is enabled, the frames within the network are treated as follows:
•
•

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 (see
OL-6973-03, Cisco MDS SAN-OS Release 2.x
Route Change Delivery
Switch 2
Frame 2
21-5, the new path from Switch 1 to Switch 4 is faster. Hence, Frame 3 and Frame 4 may be
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.
Figure 21-5).
Switch 3
Frame 1
Frame 4 Frame 3
Figure 21-6).
Cisco MDS 9000 Family Configuration Guide
In-Order Delivery
Old path
New path
Switch 4
21-11