IPv6 Source Address Rewrite for Multi-Uplink Connectivity
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Solution Overview
Problem
Existing IETF standards for multi-homed IPv6 networks fail to address scenarios where the selected uplink is down, does not provide internet access, requires load-balancing, or has a source address in a unique local address prefix, leading to broken end-to-end connectivity and complex address management.
Innovation Solution
Implement a deterministic and adaptive source address rewrite mechanism that uses provider-assigned IPv6 prefixes for internal VLANs, with stateless or stateful hashing to map invalid addresses to valid uplink addresses, and supports advanced SD-WAN policies for uplink selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If source address rewrite is performed for all packets, then uplink selection policy can be applied, but end-to-end connectivity is broken
Solution Approach 1:
The patent applies different source address rewrite strategies based on the validity of the source address on the selected uplink. When the source address is valid on the selected uplink, no rewrite is performed, preserving end-to-end connectivity. When the source address is invalid, rewrite is performed to enable uplink selection policy. This local differentiation resolves the contradiction between connectivity preservation and policy enforcement.
2Adaptability or versatility
If unique local addresses are used for internal VLANs, then addressing flexibility is improved, but address management complexity increases
Solution Approach 1:
The patent enables provider-assigned IPv6 prefixes to serve dual purposes: both for internal VLAN addressing and for uplink traffic. This eliminates the need for separate unique local addresses, simplifying address management while maintaining addressing flexibility through the universal use of provider-assigned prefixes.
3Device complexity
If provider-assigned prefixes are used for internal VLANs, then address management is simplified, but insufficient addressing space from ISPs may cause conflicts
Solution Approach 1:
The patent segments the address space by introducing a new flag bit in the IPv6 header to distinguish between packets that need source address rewrite and those that don't. This segmentation allows the system to efficiently manage address translation while preserving the simplicity of using provider-assigned prefixes for internal addressing.
4Reliability
If source address is kept when valid on selected uplink, then end-to-end connectivity is preserved, but uplink selection policy cannot be applied
Solution Approach 1:
The patent implements dynamic source address rewrite behavior based on real-time conditions. The system determines whether to rewrite the source address by checking validity on the selected uplink, allowing flexible adaptation between connectivity preservation and policy enforcement depending on the specific packet and uplink conditions.
Data Source
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AI summary
According to certain embodiments, a system comprises one or more processors and one or more computer-readable non-transitory storage media comprising instructions that, when executed by the one or more processors, cause one or more components of the system to perform operations. The operations comprise receiving a packet comprising a source address; selecting an uplink for the packet, the uplink selected from a plurality of uplinks based on an uplink selection policy; determining whether the source address is valid on the selected uplink; determining whether to keep or re-write the source address based on whether the source address is valid on the selected uplink; keeping the source address when the source address is valid on the selected uplink or re-writing the source address when the source address is not valid on the selected uplink; and sending the packet to the selected uplink.