Distributed SNAT Service Using IPv6 Steering Against Bottlenecks
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Solution Overview
Problem
Centralized SNAT architectures lead to bottlenecks and misdirection issues in network traffic, while distributed SNAT architectures face challenges with packet misrouting due to lack of state information at randomly selected instances.
Innovation Solution
Implement a distributed middlebox service, such as dSNAT, across multiple host computers, using locally unique IPv6 addresses and IPv6 encapsulation for IPv4 packets, with a gateway device identifying the correct host based on IPv4 addresses and ports, and host computers performing address replacements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If centralized SNAT is used, then stateful middlebox service is provided, but network bottleneck occurs and traffic must traverse single point
Solution Approach 1:
The patent divides the centralized SNAT service into multiple distributed SNAT instances across different host computers. Each host runs an independent SNAT instance that can process packets autonomously, eliminating the single point of congestion while maintaining stateful service capabilities through local connection tracking tables.
2Productivity
If distributed SNAT is used, then network bottleneck is avoided, but packet misrouting occurs due to random selection of SNAT instances
Solution Approach 1:
The patent implements feedback mechanisms where gateway devices track which SNAT instance processed a packet and use this information to ensure subsequent packets in the same flow are directed to the same instance. Connection tracking tables maintain state information about active flows, enabling the system to learn from past routing decisions and correct future misrouting attempts.
Solution Approach 2:
Each distributed SNAT instance maintains its own local connection tracking table with state information specific to that instance. This local quality ensures that packets are routed to the correct instance based on flow state rather than random selection, improving packet delivery accuracy while preserving the throughput benefits of distribution.
3Adaptability or versatility
If distributed SNAT with same IP address is used, then service availability is improved, but packet forwarding to wrong instances occurs (N-1 out of N times)
Solution Approach 1:
The patent introduces gateway devices as intermediaries between external networks and distributed SNAT instances. These gateways maintain mapping information that translates external IP addresses to specific internal SNAT instances, acting as mediators that prevent packets from being randomly distributed while preserving the ability for multiple instances to serve the same external address.
Solution Approach 2:
The system performs preliminary action by establishing connection tracking tables and routing mappings before packet processing begins. Gateway devices pre-configured with instance-to-IP mappings ensure that packets are directed to the correct SNAT instance from the outset, preventing misrouting before it occurs rather than correcting it afterward.
Data Source
AI summary
Some embodiments of the invention provide novel methods for facilitating a distributed SNAT (dSNAT) middlebox service operation for a first network at a host computer in the first network on which the dSNAT middlebox service operation is performed and a gateway device between the first network and a second network. The novel methods enable dSNAT that provides stateful SNAT at multiple host computers, thus avoiding the bottleneck problem associated with providing stateful SNAT at gateways and also significantly reduces the need to redirect packets received at the wrong host by using a capacity of off-the-shelf gateway devices to perform 1Pv6 encapsulation for 1Pv4 packets and assigning locally unique 1Pv6 addresses to each host executing a dSNAT middlebox service instance that are used by the gateway device.