Chapter 21
| Data Center Bridging Commands
Openflow Commands
– 570 –
Openflow Commands
OpenFlow enables remote controllers to determine the path of network packets
through the network of switches. This separation of the control from the
forwarding allows for more sophisticated traffic management than is feasible using
access control lists and routing protocols.
OpenFlow allows remote administration of a switch's packet forwarding tables, by
adding, modifying and removing packet matching rules and actions. This way,
routing decisions can be made periodically or ad hoc by the controller and
translated into rules and actions with a configurable lifespan, which are then
deployed to a switch's flow table, leaving the actual forwarding of matched packets
to the switch at wire speed for the duration of those rules. Packets which are
unmatched by the switch can be forwarded to the controller. The controller can
then decide to modify existing flow table rules on one or more switches or to
deploy new rules, to prevent a structural flow of traffic between the switch and
controller. It could even decide to forward the traffic itself, provided that it has told
the switch to forward entire packets.
The following table is from the Openflow standard. It illustrates how flow decisions
are made at each table, and then passed on to the next table for subsequent
processing. To ensure no looping occurs in the flow process, a table with a lower ID
cannot pass control data onto a table with a larger ID.
Set Point The set-point for the queue. This is the target number of octets in the CP’s
queue. (Default: 26000)
Feedback Weight Variable used in calculation or Quantized Feedback and New Sample Base. If
the queue length is moving toward the set point, the feedback weight will be
closer to 0 than if the queue length is moving away from the set point.
Minimum Sample
Base
The minimum number of octets to enqueue in the CP’s queue between CNM
PDU transmissions. (Default: 150,000 bytes)
Discarded Frames The number of frames offered to this CP that were discarded because of a full
output queue.
Transmitted Frames The number of data frames enqueued for transmission on this CP’s output
queue.
Transmitted CNMs The number of CNMs transmitted by this CP.
Table 113: show cn cp - display description (Continued)
Field Description
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