VRRP Master Controller Stability via STP Convergence Check
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless local area networks, when VRRP pre-emption is disabled, network controllers may inadvertently preempt a pre-existing master network controller due to delayed receipt of VRRP advertisements during spanning tree protocol convergence, leading to disruptions.
Innovation Solution
A network device determines a bake-off time and refrains from sending packets during this period, then checks for received packets to confirm STP convergence before starting the VRRP state machine and transmitting a heartbeat message to indicate its role as a master controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a network controller waits for a predetermined period after powering up before participating in VRRP, then it avoids immediate pre-emption, but it may still inadvertently preempt a pre-existing master controller due to delayed receipt of VRRP advertisements during STP convergence
Solution Approach 1:
The patent applies preliminary action by having the network controller wait for STP convergence confirmation before participating in VRRP master elections. The controller sends a bridge protocol data unit (BPDU) upon powering up and only transitions to VRRP state machine after receiving a BPDU response, ensuring the network path is stable before attempting to become master. This preliminary STP convergence check prevents premature VRRP participation that could cause inadvertent pre-emption.
Solution Approach 2:
The patent uses feedback mechanisms where the network controller monitors for BPDU responses from other controllers before proceeding with VRRP state transitions. The controller continuously checks for STP convergence status and only advances to VRRP master election when feedback confirms network stability. This feedback loop ensures the controller has accurate information about network state before making master controller decisions.
2Reliability
If VRRP pre-emption is disabled to prevent inadvertent pre-emption, then master controller stability improves, but the system loses the ability to recover from failed masters through pre-emption
Solution Approach 1:
The patent applies dynamics by making the pre-emption behavior conditional rather than static. The system dynamically determines whether pre-emption should occur based on STP convergence status. When STP has not converged, pre-emption is effectively blocked regardless of the pre-emption configuration setting. When STP has converged, the normal pre-emption behavior is allowed. This dynamic approach resolves the contradiction by adapting pre-emption behavior to network conditions.
Solution Approach 2:
The patent introduces STP convergence status as an intermediary condition between the pre-emption disable setting and actual pre-emption behavior. Even when pre-emption is disabled in configuration, the STP convergence check acts as an additional intermediary layer that prevents pre-emption until network stability is confirmed. This intermediary mechanism provides dual protection against inadvertent pre-emption while preserving the intended pre-emption functionality when appropriate.
3Productivity
If the network controller immediately starts the VRRP state machine after powering up, then it can quickly assume master role, but it risks preempting a pre-existing master due to network instability
Solution Approach 1:
The patent applies preliminary action by requiring STP convergence confirmation before allowing VRRP state machine initiation. The controller sends a BPDU upon powering up and waits for a response indicating network path stability. Only after this preliminary STP check succeeds does the controller proceed to start the VRRP state machine. This ensures rapid but safe master controller establishment without risking pre-emption of existing masters.
Data Source
AI summary
The present disclosure relates to a network device that indicates a master network controller in a virtual redundant router protocol (VRRP) peer. In example implementations, the network device determines a bake-off time and refrains from sending packets during the bake-off time to a network. Also, the network device determines whether a first packet is received from the network. If either the bake-off time expires or the first packet is received from the network, the network device determines whether a spanning tree protocol (STP) convergence has completed. If so, the network device starts a VRRP state machine. If both the STP convergence has completed and the VRRP state machine has been started, the network device transmits a broadcast message indicating that the network device acts as a master network controller in the network.