Default Gateway Router Source Address Selection
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Solution Overview
Problem
Multi-homed sites face issues with routing stability and ingress filtering, where legacy host devices may encounter packet drops due to source address ingress filtering rules, and existing solutions do not effectively exploit redundancy or implement cost-based routing policies, leading to suboptimal source address selection.
Innovation Solution
A default gateway router configures a host device with multiple address prefixes from exit routers, ordering them based on preference, allowing the host device to select an appropriate source address that complies with ingress filtering rules and optimizes routing, without requiring complex routing protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a site advertises multiple address prefixes through multiple ISP connections, then routing redundancy and fault tolerance are improved, but the number of routes propagated throughout the DFZ increases, reducing overall routing stability
Solution Approach 1:
The invention extracts the source address selection function from the routing protocol and places it in the host device. The router no longer needs to propagate multiple prefixes throughout the DFZ, as the host device performs source address selection locally based on advertised prefixes. This removes the harmful effect of route propagation on routing stability while preserving fault tolerance.
Solution Approach 2:
The invention introduces an intermediary mechanism where the host device receives routing information from the router and performs source address selection locally. This intermediary approach allows the router to provide routing information without propagating multiple prefixes throughout the entire DFZ, thus maintaining routing stability while enabling redundancy.
2Object-affected harmful factors
If ingress filtering rules are applied to prevent spoofed source addresses, then security is improved, but legitimate packets are dropped when the source address belongs to another ISP's prefix range
Solution Approach 1:
The invention applies local quality by enabling the host device to select source addresses based on local routing information received from its default router. Each host device independently determines the appropriate source address prefix based on the routing advertisement, ensuring that selected addresses comply with ingress filtering rules of the local network while avoiding conflicts with other ISPs' prefixes.
Solution Approach 2:
The invention implements feedback by having the host device receive routing information from the router and use this information to make informed source address selections. The router provides feedback about available prefixes and routing preferences, enabling the host to select addresses that will not be blocked by ingress filtering while maintaining security.
3Ease of operation
If the router assigns source addresses to the host device, then source address selection is simplified, but the host device loses flexibility in using different source address values
Solution Approach 1:
The invention applies self-service by enabling the host device to autonomously select source addresses based on routing information received from the router. The host device maintains a local copy of routing information and independently determines the appropriate source address, eliminating the need for router intervention in each selection while preserving flexibility.
Solution Approach 2:
The invention implements preliminary action by having the router advertise routing information to the host device in advance. The host device stores this routing information locally and uses it for future source address selections, eliminating the need for real-time router intervention while maintaining flexibility and adaptability.
4Loss of information
If multiple routing protocol instances are executed for respective prefixes, then routing knowledge for each ISP is improved, but the system complexity increases and fails to exploit redundancy effectively
Solution Approach 1:
The invention merges multiple routing protocol instances into a single routing protocol execution in the router. The router collects routing information from multiple ISPs and presents it to the host device in an organized manner, eliminating the need for separate routing protocol instances for each prefix while preserving complete routing knowledge.
Solution Approach 2:
The invention applies universality by designing a single routing protocol implementation that handles multiple ISPs and prefixes universally. The router uses one routing protocol instance to gather information from all ISPs and then distributes this consolidated information to the host device, which performs source address selection based on the unified routing information.
Data Source
AI summary
A default gateway router of a multi-homed site is configured for supplying, to a host device, a plurality of address prefixes having been advertised by respective exit routers providing respective connecting links for the multi-homed site to a wide area network. The default gateway router sends the address prefixes to the host device in a determined order based on a determined preference in the default gateway router for reaching the respective exit routers. The host device is configured for selecting a source address according to the determined order supplied by the default gateway router. The address also prefixes may be grouped according to identified destination prefixes, enabling the host device to select, for a given identified destination prefix, the source address according to the ordering of address prefixes within the corresponding group.