Users Guide

1720 OpenFlow
If an unknown interface is used in the match criteria for a new flow, the flow
is held in the application table until the interface is attached. Dell EMC
Networking OpenFlow Hybrid does not generate any error for the flow. Once
the interface is attached, the flow is added to the hardware.
If the flow is already installed and the interface in the match criteria goes
away, the flow is removed from the hardware. Dell EMC Networking
OpenFlow Hybrid keeps the flow in the application table and reinserts it into
the hardware when the interface becomes attached again.
If an interface specified in the action list for the new flow is not attached, the
flow is added to the hardware. If the missing interface is the only egress
interface for the flow, the flow is configured to drop matching packets. If the
missing interface is one of several egress interfaces, it is simply excluded from
the egress interface list.
The OpenFlow application monitors for interface creation and removal
events and modifies the flows as needed.
Flow Status and Statistics Collection
The OpenFlow Controller can ask the switch to send it the list of flows that
match certain criteria. The switch sends the matching flows with one or more
messages.
Flows support packet and byte counters. The switch polls the hardware
counters periodically and stores the counter values in the application table.
When sending messages to the controller, the switch retrieves the counter
values from the application table. The switch does not read the hardware
counters when sending flow statistics to the controller.
To avoid performance problems, the counter collection is rate-limited. The
switch polls counters for 100 flows every 10 seconds. This means that if the
flow table has one to 100 entries, the counters are updated every 10 seconds
for all flows. If the flow table has 3000 entries, the counters are updated every
300 seconds for all flows.
The statistics poll rate and the number of flows per poll cycle are porting
parameters that can be tuned as needed. When the switch is busy
manipulating flows, the statistics update may take longer.
If a flow is removed from the hardware, the packet counters are reported as 0.
If the flow is added back to the hardware, the counters start counting from 0.