Virtual Port Channel Peer Failure Recovery via Cost Inflation
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Solution Overview
Problem
Virtual port channel peer failures in network switching lead to excessive and prolonged tenant traffic drops due to long recovery times, resulting in lost packets during the convergence process.
Innovation Solution
The system inflates the virtual address reachability cost for the failed vPC peer and delays its bring-up time until synchronization with the surviving peer is complete, allowing traffic to be diverted to the surviving peer and ensuring minimal disruption by maintaining the appearance of endpoint hosts behind the virtual IP address.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the failed vPC peer is immediately brought back online, then recovery time is reduced, but packet loss occurs during the convergence process
Solution Approach 1:
The system performs preliminary actions by inflating the reachability cost and delaying the bring-up time of the failed vPC peer until synchronization with the surviving peer is complete. This ensures that the peer is fully ready to handle traffic before it is brought online, preventing packet loss during the convergence process while maintaining minimal disruption to network operations
2Reliability
If traffic is immediately routed to the surviving peer upon failure detection, then service continuity is maintained, but the failed peer cannot synchronize its state information
Solution Approach 1:
The system uses an intermediary mechanism by inflating the reachability cost of the failed vPC peer, which acts as a mediator to divert traffic to the surviving peer. This allows the failed peer to synchronize its state information with the surviving peer without receiving traffic during the synchronization process, ensuring both service continuity and proper state synchronization
3Stability of the object's composition
If the vPC peer bring-up time is delayed for synchronization, then state consistency is ensured, but the convergence window increases
Solution Approach 1:
The system changes the reachability cost parameter of the failed vPC peer to an inflated value during the synchronization period. This parameter change allows the system to maintain state consistency by delaying bring-up time while minimizing the convergence window, as the inflated cost is a controlled adjustment that does not permanently affect system performance
Data Source
AI summary
Systems, methods, and non-transitory computer-readable storage media for recovering from a partial failure of a virtual port chain (vPC) domain. The first and second vPC peers may be paired to create a vPC having a virtual address. An endpoint host may communicate with a network via the virtual port channel. The system may detect that the first virtual port channel peer is down. During or after the first vPC reboots, the reachability cost for the first vPC with regards to the virtual address can be set to an inflated value. The first vPC peer may also delay its bring up time while it synchronizes its vPC state information with the second vPC peer. The second vPC can continue to advertise the association between the endpoint host and the virtual address. Upon completion of the synchronization, the first vPC peer may bring up the link and restore the reachability cost.