Book Image

OpenFlow Cookbook

Book Image

OpenFlow Cookbook

Overview of this book

Table of Contents (17 chapters)
16
Index

Modifying a flow entry in a flow table

When the controller wants to modify a flow table entry, it sends a flow entry modification message (OFPT_FLOW_MOD) to the switch, with the command value set as OFPFC_MODIFY or OFPFC_MODIFY_STRICT. This flow table modification message contains the information required to identify and modify the entry from the flow table.

The OpenFlow specification defines two different variants for modifying a flow entry: strict and non-strict versions.

How to do it...

When the switch receives the OFPT_FLOW_MOD message with the command field set as OFPFC_MODIFY_STRICT, all the fields in the flow modification message should be matched strictly against the flow table entry, and should be modified from the flow table.

When the switch receives the OFPT_FLOW_MOD message with the command field set as OFPFC_MODIFY, then the switch should select the flow entry to be modified, which either exactly matches or has more match fields present in it than the flow modification message...