PE Router VRF Lookup via Logical Interface
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Solution Overview
Problem
Existing VPN technologies face challenges in establishing network tunnels between provider edge (PE) routers and customer edge (CE) routers across different service provider networks, especially when intermediate devices do not support certain services like multicast, leading to issues with logical isolation of virtual routing and forwarding (VRF) tables.
Innovation Solution
The techniques involve a PE router performing tunnel destination and output interface lookups using appropriate VRF tables corresponding to the VPN, allowing packets to be forwarded through a network tunnel that spans across service provider networks, even when intermediate devices do not support the requested service, by selecting a logical interface not associated with a physical output interface and determining the output interface from the VRF tables based on the packet's destination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If logical isolation of VRF tables is implemented within a router, then routing and forwarding information for different VPNs is isolated, but tunneling to remote CE routers associated with specific VRF instances becomes challenging
Solution Approach 1:
The patent introduces a default logical interface as an intermediary between the VRF table and physical output interfaces. This default logical interface acts as a mediator that allows the router to perform lookups in the VRF table without requiring a direct association between VRF instances and physical interfaces, thereby enabling tunnel establishment to remote CE routers while maintaining VRF isolation.
Solution Approach 2:
The patent segments the interface association by decoupling the default logical interface from specific physical output interfaces. Instead of directly associating VRF tables with physical interfaces, the system creates a separate layer with default logical interfaces that are not tied to specific physical outputs, allowing flexible routing decisions while preserving logical isolation.
2Ease of manufacture
If intermediate devices do not support certain services like multicast, then service provider network can operate with simpler devices, but services requiring those features cannot be provided to customers
Solution Approach 1:
The patent uses network tunnels as intermediaries to bypass intermediate devices that do not support certain services. By encapsulating traffic in tunnels, the system can transport service-specific traffic (such as multicast) through the network without requiring intermediate devices to understand or support those services, thus maintaining device simplicity while providing service versatility.
Solution Approach 2:
The patent creates virtual copies of service capabilities through tunneling. Instead of requiring physical service support at every intermediate device, the system creates virtual service instances through tunnel endpoints that can provide services like multicast by routing traffic through devices that do support them, effectively copying service functionality across the network.
3Adaptability or versatility
If tunneling is implemented across different service provider networks, then service coverage is expanded, but route leaking and table next hops become necessary which complicates the system
Solution Approach 1:
The patent extracts the routing decision logic from complex multi-table lookups by using the default logical interface as a unique key. Instead of requiring route leaking between multiple routing tables or complex next-hop calculations, the system takes out the complexity by allowing direct VRF table lookups using the default logical interface, thereby simplifying routing table management while maintaining expanded service coverage.
Data Source
AI summary
Selection of proper virtual routing and forwarding (VRF) tables is based on a logical interface that is not associated with a physical interface. The selected VRF table is used to perform an output interface lookup for outgoing packets. In one example, a router includes a plurality of network interfaces, and a processing unit configured to select a logical interface not associated with any of the plurality of network interfaces based on an association with a received packet of a virtual private network, select one of a plurality of VRF tables in which to perform an output interface lookup for the packet that corresponds to the selected logical interface, and determine one of the plurality of network interfaces from the one of the plurality of VRF tables based on a destination of the packet, wherein the determined one of the plurality of network interfaces is configured to forward the packet.