Edge Services Gateway Traffic Hand-off via Pre-established Tunnels
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Solution Overview
Problem
In software-defined data centers, the hand-off of an edge services gateway (ESG) virtual computing instance from one host to another often results in data traffic downtime due to underlay network programming and convergence delays, leading to potential packet drops during the transition.
Innovation Solution
The method involves pre-establishing control and data tunnels between cloud managers and virtual routers to reroute traffic seamlessly, decoupling overlay convergence from underlay convergence, and using policy-based routing rules to redirect outbound traffic until the underlay converges, ensuring continuous data flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ESG VCI is activated on a new host and routing tables are reprogrammed to associate the third IP address with the second network interface, then the ESG can operate from the new host, but the underlay network convergence delay causes data traffic downtime and packet drops during the transition
Solution Approach 1:
The patent applies preliminary action by pre-establishing data tunnels between the old host and new host before the ESG VCI migration is complete. The forwarding rule is programmed in advance to redirect outbound data traffic from the new host through the data tunnel to the old host, ensuring continuous packet flow during the underlay convergence period. This proactive setup eliminates packet drops by having the traffic path ready before the routing table update completes.
Solution Approach 2:
The patent introduces a data tunnel as an intermediary element between the old host and new host. This tunnel acts as a mediator that carries data traffic during the transition period, allowing packets to flow from the new host through the tunnel to the old host and then to the underlay network. The tunnel bridges the gap caused by underlay convergence delays, maintaining connectivity without requiring immediate underlay routing updates.
2Reliability
If policy-based routing rules are used to redirect outbound traffic from the new host to the old host through data tunnels, then packet delivery is maintained during underlay convergence, but additional network complexity is introduced
Solution Approach 1:
The patent applies the discarding and recovering principle by implementing temporary forwarding rules that are discarded once underlay convergence is complete. The system monitors underlay convergence status and automatically removes the data tunnel forwarding rules when the routing tables are fully updated. This temporary addition of complexity is recovered by cleaning up the extra routing entries, maintaining long-term simplicity while solving the short-term convergence problem.
3Ease of operation
If the forwarding rule is programmed to redirect outbound data traffic from the new host to the old host, then seamless hand-off is achieved, but the forwarding rule must be dynamically updated based on underlay convergence status
Solution Approach 1:
The patent implements feedback by monitoring the underlay network convergence status and using this information to dynamically control the forwarding rule state. The system detects when routing table updates are complete and automatically adjusts the data tunnel forwarding rules accordingly - maintaining them during convergence and removing them after convergence. This feedback mechanism automates the complexity of dynamic rule management, making the seamless hand-off process self-regulating rather than manually controlled.
Data Source
AI summary
The disclosure provides an approach for seamless hand-off of data traffic in public cloud environments with reverse path filtering. Techniques are provided for activating an edge services gateway (ESG) virtual computing instance (VCI) on a new host in a data center. Before an underlay converges on the new host, inbound and outbound packets for the ESG VCI are sent by the underlay to the old host and the old tunnels the packets to the new host via a pre-created overlay tunnel. For outbound packets, the new host tunnels the packets back to the old host after the ESG VCI performs network address translation of the source address. Once the new host detects that the underlay converges, the new host stops redirecting the outbound packets to the old host.