Abstract: The controller may include a switch modeling interface that maintains switch models of switches in a network. The switch modeling interface may receive a desired network configuration from application modules that respond to network events. The switch modeling interface may compare the desired network configuration with the current network configuration represented by the switch models. The switch modeling interface may generate control messages to the switches for only identified differences between the desired network configuration and the current network configuration as identified by the switch models. The differences may be identified based on digest values retrieved from the switches. The switch modeling interface may determine whether the control messages were successfully received and processed by a switch and may indicate success or failure to the application module that provided the desired network configuration.

Abstract: A controller implemented on computing equipment may control switches in a network. The controller may provide flow tables that implement network policies to the switches to control packet forwarding through the network. The controller may provide debug table entries to the switches for use in a debug table that is separate from the flow table. The debug table entries may match incoming network packets and increment corresponding counters on the switches. The controller may retrieve count information from the counters for performing debugging operations on the network. For example, the controller may identify conflicts between fields of a selected flow table entry, determine whether elephant packet flows are present between switches, determine whether desired load balancing is being performed, determine whether a network path has changed, determine whether packet loss has occurred, and/or determine whether network packets are taking undesired paths based on the retrieved count information.

Abstract: A controller implemented on computing equipment may control switches in a network. The controller may provide flow tables that implement network policies to the switches to control packet forwarding through the network. The controller may provide debug table entries to the switches for use in a debug table that is separate from the flow table. The debug table entries may match incoming network packets and increment corresponding counters on the switches. The controller may retrieve count information from the counters for performing debugging operations on the network. For example, the controller may identify conflicts between fields of a selected flow table entry, determine whether elephant packet flows are present between switches, determine whether desired load balancing is being performed, determine whether a network path has changed, determine whether packet loss has occurred, and/or determine whether network packets are taking undesired paths based on the retrieved count information.