Cisco DS-C9216I-K9, Руководство по настройке

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21-9
Cisco MDS 9000 Fabric Manager Switch Configuration Guide
OL-7753-01
Chapter 21 Configuring Fibre Channel Routing Services and Protocols
In-Order Delivery
Figure 21-5 Route Change Delivery
In Figure 21-5 , the new path from Switch 1 to Switch 4 is faster. Hence, 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 treated as specified below:
• Frames in the network are delivered in the order in which they are transmitted.
•
Frames which can not be delivered in-order within the network latency drop period are dropped
inside the network.
• The number of dropped frames are reduced by slowing down the traffic at the frame source.
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.
Figure 21-6 Link Congestion Delivery
In Figure 21-6 , the port of the old path (red dot) is congested. Hence Frame 3 and Frame 4 can be
delivered before Frame 1 and Frame 2.
When the in-order guarantee feature is enabled, the frames crossing a PortChannel are treated as
specified below:
•
Frames using the old path are delivered before new frames are accepted.
• Frames which cannot be delivered in-order, through the old path, within the switch latency drop
period are dropped.
•
The new frames are delivered through the new path after the switch latency drop period has elapsed.
Switch 1 Switch 2 Switch 3
Switch 4
Frame 2 Frame 1
Frame 4 Frame 3
Old path
New path
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Switch 1 Switch 2
Frame 2 Frame 1
Frame 4 Frame 3
Old path
New path
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