SDN Link Failure Recovery via Pre-configured Backup Flowtables
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Solution Overview
Problem
Existing SDN networks face longer recovery times after interruptions due to the inability to immediately identify and switch to alternative paths, leading to potential network disruptions until flowtables expire and are updated.
Innovation Solution
A method and device for detecting link interruptions in SDN networks, determining a single replacement link, connecting it, and forwarding packets through this link, while also backing up reserved flowtables to expedite the update process, thereby reducing network recovery time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the aging time is shortened to enable faster flowtable updates, then the network recovery time is improved, but the flowtable requests on the controller are greatly increased, causing an increase in the burden to the controller
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-configuring backup flowtable entries in the switches before link failures occur. The controller proactively sets up alternative paths and stores them in the flowtables with appropriate timeout values, so that when a link failure occurs, the switches can immediately use the pre-prepared backup entries without waiting for the aging process or generating new requests to the controller.
Solution Approach 2:
The patent uses copying by creating backup copies of flowtable entries for alternative paths. When a primary link is working, the flowtable contains both the primary path entry and backup path entries (copies). Upon link failure, the backup copies are already available in the switch memory and can be activated immediately by clearing the timeout field, eliminating the need for real-time controller intervention.
2Device complexity
If the aging time is extended to reduce flowtable requests on the controller, then the controller burden is reduced, but the network recovery time is increased
Solution Approach 1:
The controller performs preliminary actions by pre-configuring backup flowtable entries during normal operation. These backup entries are prepared in advance with timeout values set to a specific duration. When a link failure occurs, the switches can immediately activate these pre-prepared entries by resetting their timeout counters, achieving fast recovery without requiring extended aging times or frequent controller requests.
3Duration of action of stationary object
If the switches continue to forward packets according to existing flowtable items after link interruption, then the forwarding continuity is maintained, but packets are forwarded to wrong paths causing network interruptions
Solution Approach 1:
The patent applies preliminary action by pre-configuring backup flowtable entries with alternative paths before link failures occur. The switches maintain forwarding continuity by having ready-to-use backup entries, while ensuring packet forwarding accuracy through the use of pre-calculated alternative paths that are guaranteed to be valid. The timeout mechanism ensures that backup entries are only activated when needed, maintaining both continuity and accuracy.
4Adaptability or versatility
If all flowtable items are maintained in the switches, then the network can handle all traffic patterns, but the switch memory is exceeded since the traffic capacity is limited
Solution Approach 1:
The patent extracts only the essential backup flowtable entries needed for failure recovery, rather than storing all possible flowtable items. The controller identifies and stores only the critical alternative paths in the switch flowtables, removing unnecessary entries. This selective extraction maintains adaptability for handling traffic patterns while respecting the limited switch memory capacity.
Data Source
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AI summary
The present invention provides a package forwarding method and device, an SDN and a system, wherein the method includes: detecting that a link in an SDN is interrupted; determining a replacement link which is used for replacing the interrupted link and in which number of segment of link in a blocked state is only one; conducting connection processing on the replacement link in the blocked state; and forwarding a package via the replacement link after connection. The present invention solves the problem of longer recovery time of the network after interruption in relevant technologies, so as to achieve an effect of shortening the recovery time of the network after interruption.