SDN Controller Unreachable OpenFlow Rule Removal
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Solution Overview
Problem
In software-defined networks (SDN) using OpenFlow, the limited capacity of ternary content addressable memories (TCAMs) leads to complexity in managing unreachable OpenFlow rules, which occupy space and complicate debugging and diagnostics due to the need to examine all rules, including those that are masked by higher-priority rules.
Innovation Solution
A method and system for an SDN controller to query, mark, and remove unreachable OpenFlow rules from OpenFlow network devices, allowing for efficient management of TCAM space by determining rule reachability and automatically removing or caching unreachable rules, thereby simplifying diagnostics and reducing the number of rules that need to be examined.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unreachable OpenFlow rules are kept in TCAM, then rule persistence is maintained, but TCAM space is wasted and debugging complexity increases
Solution Approach 1:
The patent extracts and removes unreachable rules from the TCAM storage. The controller identifies rules that are no longer reachable (masked by higher-priority rules) and actively removes them from the network device, separating the useful reachable rules from the useless unreachable rules to reduce storage waste and debugging complexity
Solution Approach 2:
The patent implements preliminary identification and marking of unreachable rules before removal. The controller queries rule reachability status in advance, marks unreachable rules for removal, and then executes the removal operation. This preliminary action ensures that only truly unreachable rules are removed, maintaining rule persistence for reachable rules while cleaning up unreachable ones
2Measurement precision
If all OpenFlow rules are examined for debugging, then complete diagnostics are achieved, but diagnostic time increases
Solution Approach 1:
The patent extracts unreachable rules from the complete rule set and separates them from reachable rules. By removing unreachable rules from TCAM, the system reduces the number of rules that need to be examined during debugging, allowing diagnostic tools to focus only on reachable rules that actually affect packet forwarding
Solution Approach 2:
The patent segments the OpenFlow rules into two distinct sets: reachable rules and unreachable rules. This segmentation is achieved through controller queries that identify rule reachability status, allowing the system to treat these two sets differently - keeping reachable rules for active forwarding while removing unreachable rules from diagnostic scope
3Quantity of substance
If unreachable rules are removed from TCAM, then TCAM space is optimized, but rule management complexity increases
Solution Approach 1:
The patent implements self-service through automatic rule reachability detection and removal. The controller automatically queries rule status, identifies unreachable rules, and removes them without manual intervention. This automation reduces the burden on administrators while optimizing TCAM space utilization
Solution Approach 2:
The patent uses feedback mechanisms where the controller continuously queries the network device about rule reachability status. Based on this feedback, the controller determines which rules are unreachable and removes them, creating a closed-loop system that automatically adapts to changing network conditions and maintains optimal TCAM utilization
Data Source
AI summary
Methods and systems are provided. A method includes managing, by a software defined network (SDN) controller, OpenFlow rules stored on an OpenFlow network device having a ternary content addressable memory (TCAM). The OpenFlow rules include unreachable OpenFlow rules and reachable OpenFlow rules. The managing step includes querying at least one OpenFlow rule from among the unreachable OpenFlow rules and the reachable OpenFlow rules on the at least one OpenFlow network device. The managing step further includes determining whether any of the OpenFlow rules are reachable or unreachable from indicia used to mark the OpenFlow rules as reachable or unreachable. The managing step also includes causing a removal of the unreachable OpenFlow rules from the OpenFlow network device.