Active-Active Logical Service Router Session Consistency
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Solution Overview
Problem
Implementing active-active mode for logical routers in Software-Defined Networking (SDN) environments is challenging due to difficulties in maintaining consistency and session stickiness, leading to potential disruptions in stateful service insertion.
Innovation Solution
The solution involves configuring logical routers to maintain affinity with a particular router for packets belonging to the same flow by using hash functions to map tuple information, ensuring that the same router is selected for subsequent packets, thereby maintaining session consistency and reducing the need for costly session information exchange.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If active-active mode is implemented for logical routers, then service availability and throughput are improved, but maintaining session consistency and stateful service insertion becomes difficult
Solution Approach 1:
The patent segments the service insertion function by introducing a Service Insertion Manager (SIM) that operates independently from the logical routers. The SIM maintains session state information separately, while logical routers focus on packet forwarding. This segmentation allows multiple logical routers to operate in active-active mode without compromising session consistency, as the SIM centralizes the state management function.
Solution Approach 2:
The Service Insertion Manager acts as an intermediary between logical routers and service functions. It receives session state information from logical routers and distributes relevant state to appropriate routers handling specific flows. This intermediary mechanism enables session consistency to be maintained across multiple active routers without requiring direct communication between them.
2Reliability
If multiple logical routers operate in active-active mode, then service availability is improved, but complexity of maintaining stateful service insertion increases
Solution Approach 1:
The patent extracts the complex state management function from the logical routers and places it in a dedicated Service Insertion Manager. This extraction reduces the complexity of individual logical routers, as they no longer need to maintain session state information. Instead, they simply forward packets and receive instructions from the SIM, significantly simplifying their operation while maintaining high availability through multiple active instances.
3Reliability
If active-standby mode is used for logical routers, then session consistency is maintained, but service throughput and availability are limited
Solution Approach 1:
The patent introduces dynamic session affinity assignment where the Service Insertion Manager can flexibly assign session state to different logical routers based on current load conditions and flow characteristics. This dynamic approach allows the system to maintain session consistency (like active-standby) while enabling multiple routers to actively handle traffic (like active-active), thereby increasing throughput without sacrificing reliability.
Data Source
AI summary
Example methods and computer systems for packet handling for active-active stateful service insertion are disclosed. One example may involve a computer system detecting a packet addressed from a source address to a service endpoint address. Based on configuration information associated with the service endpoint address, the computer system may identify a first active logical service router (SR) and a second active logical SR that are both associated with the service endpoint address and configured to operate in an active-active mode. The first active logical SR may be selected over the second active logical SR by mapping tuple information to the first active logical SR. The computer system may generate an encapsulated packet by encapsulating the packet with an outer header addressed to an outer destination address associated with the first active logical SR and send the encapsulated packet towards the first active logical SR for processing according to a stateful service.