OpenFlow Switch Graceful Restart via Flow Table Preservation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current OpenFlow switch technologies do not support Graceful Restart (GR), leading to network topology re-computation and service interruption during restart, as they lack specifications for maintaining flow tables and external connections during the restart process.

Innovation Solution

Implementing a method to mark the OpenFlow switch as being in a GR state, keeping flow tables and external connections valid, and prohibiting modifications during restart, using notification messages and extended OpenFlow protocol mechanisms to manage the GR process without re-computing network routes or updating flow tables.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the OpenFlow switch is restarted without GR support, then the control software can be reinstalled or upgraded, but the forwarding function fails and triggers re-convergence of forwarding routes affecting service traffic

Engineering Contradiction:

Improvesoftware reinstallation or upgradeVSAvoidforwarding function

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent segments the control plane and forwarding plane into separate entities (OpenFlow controller and OpenFlow switch). The control plane can be restarted independently while the forwarding plane continues to operate using the existing flow table, thus allowing software reinstallation or upgrade without affecting forwarding functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent establishes a GR state before the control software restart, during which the flow table is preserved and marked as valid. This preliminary preparation ensures that when the control plane restarts, the forwarding plane can continue to use the existing flow table without interruption, avoiding service traffic impact.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the OpenFlow switch enters fail secure mode or fail standalone mode upon connection interruption, then the forwarding function continues to run, but the network topology must be re-computed and flow tables updated after restart

Engineering Contradiction:

Improveforwarding functionVSAvoidroute re-computation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent introduces a GR state mechanism with feedback between the OpenFlow switch and controller. The switch notifies the controller of the GR state, and the controller responds by preserving the flow table and not triggering route re-computation. This feedback loop ensures that the system recognizes the intentional restart and avoids unnecessary re-computation, saving time.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the state parameter of the OpenFlow switch to indicate GR mode. This parameter change triggers different behavior in the controller, which then preserves the flow table and avoids route re-computation, thereby reducing the time loss associated with network convergence.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the OpenFlow controller deletes the OpenFlow switch from network topology upon connection interruption, then the controller can re-compute routes, but service traffic is interrupted during the process

Engineering Contradiction:

Improveroute re-computation efficiencyVSAvoidservice traffic

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent establishes the GR state before the control software restart, during which the flow table is preserved and marked as valid. This preliminary preparation ensures that when the control plane restarts, the forwarding plane can continue to use the existing flow table without interruption, avoiding service traffic impact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The GR state acts as an intermediary mechanism between the OpenFlow switch and controller during restart. It mediates the interaction by signaling the controller to preserve the flow table and avoid deleting the switch from the network topology, thus maintaining service traffic continuity while allowing route re-computation to proceed efficiently after restart.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP3110082B1Processing method and device for graceful restart of open flow switch, and open flow controller

Publication Date: 2023.10.04 ZTE CORP

Figure 1~2
Figure 3~4
Figure 5

AI summary

Provided are a method and device for processing a Graceful Restart (GR) of an OpenFlow switch, and an OpenFlow controller. The method includes that: the OpenFlow switch is determined being in a GR state; and the state of the OpenFlow switch is marked as the GR state, wherein marking the state as the GR state includes: keeping a flow table and external connection of the OpenFlow switch before GR still valid, and prohibiting the flow table from being modified. Through the present disclosure, the problem in the related art that GR of an OpenFlow switch cannot be achieved is solved, thereby achieving the effect of effectively implementing the GR of the OpenFlow switch.