SDN-Backed Bare-Metal Live Migration With Shadow Packet Forwarding
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Solution Overview
Problem
Existing live migration methodologies for bare-metal instances backed by SDN appliances result in significant data path downtime due to the disconnection and re-attachment of IP resources, leading to prolonged service unavailability, which is undesirable for mission-critical applications.
Innovation Solution
A phased approach is implemented, including shadow mapping, forwarder configuration, and optimized resource allocation to minimize downtime, ensuring minimal disruption during the migration process by enabling interim communication and correct routing of residual data packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional live migration methodology is used for bare-metal instances backed by SDN appliances, then migration can be completed, but data path downtime is significant (minutes)
Solution Approach 1:
The patent applies preliminary action by pre-configuring shadow mapping and forwarder rules before the actual migration occurs. The shadow mapping is created in advance to map client addresses to the destination SDN appliance's provider address, and the forwarder is pre-configured to intercept and forward packets to the destination. This preparation ensures that when migration happens, the data path can be switched with minimal downtime rather than minutes of disruption.
Solution Approach 2:
The patent introduces an intermediary mechanism through the forwarder that acts as a mediator between the source and destination SDN appliances. The forwarder intercepts packets destined for the source instance and forwards them to the destination instance, enabling seamless traffic redirection during migration. This intermediary approach allows the migration to occur without significant service interruption, resolving the contradiction between migration completion and service availability.
2Adaptability or versatility
If IP resources are disconnected and re-attached during migration, then bare-metal instance can be migrated, but service unavailability is prolonged
Solution Approach 1:
The patent implements continuity of useful action by maintaining packet forwarding throughout the migration process. The forwarder continues to intercept and forward packets to the destination instance even while the migration is in progress. This continuous packet forwarding ensures that network services remain available during migration, eliminating the prolonged service unavailability that would otherwise occur during IP resource disconnection and re-attachment.
Solution Approach 2:
The patent uses copying by creating a shadow mapping that replicates the address mapping relationship. The shadow mapping copies the client address to provider address mapping from the source SDN appliance to the destination SDN appliance, allowing the destination to assume the source's network identity. This copying mechanism enables the migration to proceed without breaking the network connection, thus reducing service unavailability while maintaining migration capability.
3Loss of time
If phased approach with shadow mapping and forwarder configuration is implemented, then data path downtime is reduced to seconds, but system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the migration process into distinct phases: preparation phase (creating shadow mapping and configuring forwarder), execution phase (migrating the bare-metal instance), and cleanup phase (removing shadow mapping and forwarder rules). This segmentation allows each phase to be handled independently with specific optimizations, reducing overall downtime to seconds. While it introduces procedural complexity, the structured approach makes the complex process manageable and repeatable.
Data Source
AI summary
According to examples, a network control apparatus executes the live migration of a source bare-metal instance backed by a source software defined networking (SDN) appliance to a destination bare-metal instance associated with a destination software defined networking (SDN) appliance while minimizing data path downtime. The network control apparatus initially performs network allocations which include creating a shadow mapping. The network control apparatus triggers a forwarder on the source SDN appliance to forward data packets from network hosts destined for the source bare-metal instance to the destination SDN appliance until live migration is completed or mapping policy is updated. The mapping policy is updated by deleting shadow mapping when the live migration is complete and the source bare-metal instance is de-allocated and removed. The network control apparatus executes the live migration while minimizing the data path downtime so that applications on the destination bare-metal instance may continue to execute with minimal or no interruptions.