Port Mapping for Bonded ECMP Interfaces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Providing a stateful service across multiple equal cost multipathing (ECMP) paths is challenging due to the inability of service engines to track state information when different paths are selected for forward and return data messages, leading to incorrect path selection and loss of state information.
Innovation Solution
A network edge device bonds interfaces using a bonding module that maintains a mapping between ingress and egress interfaces, ensuring deterministic forwarding and maintaining state information by associating an identifier with each data message, allowing all traffic to go through the same set of logical switches and service engine, even if separate paths are used for forward and return messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different ECMP paths are selected for forward and return data messages, then path selection flexibility is improved, but state tracking capability deteriorates because service engines cannot track state information when messages take different paths
Solution Approach 1:
The system segments the ECMP path selection by creating separate logical paths for forward and return traffic through interface bonding. Each bonded interface group maintains independent path selection, allowing forward traffic to use one ECMP path while return traffic uses another, yet both remain associated with the same service engine through the bonding relationship.
Solution Approach 2:
The interface bonding mechanism acts as an intermediary between the ECMP path selection and the service engine. It intercepts data messages, associates them with specific ingress interfaces, and ensures they are forwarded to the correct egress interfaces while maintaining state information at the service engine regardless of which ECMP path is used.
2Reliability
If ECMP paths are combined to pass through the same service engine, then state tracking capability is improved, but path selection is not respected because combined paths redistribute messages among interfaces
Solution Approach 1:
The system performs preliminary association of data messages with ingress interface identifiers before ECMP path selection occurs. By tagging messages with their ingress interface information and maintaining a mapping table of ingress-egress interface pairs, the system ensures that messages are deterministically forwarded through the same service engine while still allowing ECMP to select different physical paths.
Solution Approach 2:
The interface bonding applies different forwarding behaviors to different interface groups. Each bonded interface group maintains its own mapping table and association rules, allowing localized path determination that respects ECMP selections while ensuring stateful service processing at the appropriate service engine.
3Reliability
If interface bonding is implemented with deterministic forwarding, then state information accuracy is improved, but device complexity increases due to mapping tables and association maintenance
Solution Approach 1:
The interface bonding mechanism maintains its own mapping tables and association data structures independently within the forwarding element. The bonding module autonomously manages ingress-egress interface mappings and message associations without requiring external control plane intervention for each message, reducing overall system complexity while maintaining accurate state information.
Data Source
AI summary
Some embodiments of the invention provide novel methods for providing a stateful service at a network edge device (e.g., an NSX edge) that has a plurality of north-facing interfaces (e.g., interfaces to an external network) and a plurality of corresponding south-facing interfaces (e.g., interfaces to a logical network). A set of interfaces on each side of the network edge device for a set of equal cost paths, in some embodiments, are bonded together in the network edge device to correspond to a single interface on either side of a logical bridge including at least one logical switch providing a stateful service implemented by the network edge device. The bond is implemented, in some embodiments, by a bonding module executing on the network edge device that maintains a mapping between ingress and egress interfaces to allow deterministic forwarding through the network edge device in the presence of bonded interfaces.