VM Migration with Preconfigured LFE During SDN Controller Outages
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Solution Overview
Problem
In software-defined networks (SDNs), controller outages lead to loss of datapath connectivity during virtual machine (VM) migration due to the destination host's inability to receive necessary configuration information from the controller.
Innovation Solution
A set of controllers identifies a subset of designated host computers in the SDN, pre-configures them with LFE information from a data store, enabling seamless VM migration without controller assistance by using a central control plane and local control plane modules to distribute this information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VM migration is performed during controller outage, then migration capability is maintained, but datapath connectivity is lost due to destination host inability to receive configuration information
Solution Approach 1:
The system performs preliminary actions by designating specific host computers as backup configuration sources before controller outages occur. These designated hosts pre-store LFE configuration information, enabling them to provide configuration data to destination hosts during migration even when the central controller is unavailable, thus preventing information loss while maintaining migration capability
Solution Approach 2:
The invention introduces intermediary elements (designated host computers) that act as mediators between the central controller and destination hosts during migration. When the controller is unavailable, these intermediary hosts provide the necessary configuration information to destination hosts, enabling migration to proceed without direct controller involvement and maintaining both connectivity and migration capability
2Loss of information
If configuration information is provided to destination host during migration, then datapath connectivity is maintained, but migration cannot proceed during controller outage
Solution Approach 1:
The system designates specific host computers in advance as backup configuration sources and pre-populates them with LFE configuration information. This preliminary action ensures that when controller outages occur, destination hosts can receive configuration data from these pre-designated intermediaries, maintaining datapath connectivity while enabling migration to proceed independently of the central controller
Solution Approach 2:
The invention changes the source parameter for configuration information from exclusively the central controller to include designated host computers. This parameter change enables the system to retrieve configuration data from alternative sources (designated hosts) when the primary source (controller) is unavailable, thus maintaining connectivity and migration availability simultaneously
Data Source
AI summary
Some embodiments provide a novel method for migrating a virtual machine (VM) from a first host computer to a second host computer in a software-defined network (SDN) when a set of controllers of the SDN, that configures several forwarding elements in the SDN to implement one LFE, is unavailable. The second host receives information regarding the VM from the first host. The VM is associated with the LFE. The second host retrieves, from a local data store of the second host, configuration information for configuring at least one software forwarding element executing on the second host to implement the LFE. The configuration information was previously received from the controller set when it was available to pre-configure the second host to implement the LFE without assistance from the controller set when the VM migrates to the second host. The second host uses the received information for the VM and the retrieved configuration information for the LFE to instantiate the VM on the second host without requesting any information from the controller set.