IP Routed Virtual Private LAN via ARP Mediation
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Solution Overview
Problem
Legacy PE routers in layer-2 VPNs face complexity in MAC learning and maintaining VSI tables, requiring advanced functionalities that are difficult to implement and maintain, especially in scenarios where PE routers need to perform MAC-based routing and keep MAC tables up to date.
Innovation Solution
A hybrid approach between layer-3 and layer-2 VPNs is implemented, using layer-3 information for routing instead of layer-2 headers, allowing existing layer-3 PE routers to bypass complex MAC/layer-2 tunnel binding operations, and introducing ARP request handlers for cross-location MAC/layer-2 address resolution, enabling encapsulation of layer-2 headers in layer-3 VPNs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If legacy PE routers implement layer-2 VPN with MAC learning and VSI tables, then layer-2 VPN functionality is achieved, but device complexity and difficulty of maintenance increase significantly
Solution Approach 1:
The patent introduces an ARP request handler as an intermediary component that mediates between layer-2 MAC address resolution and layer-3 IP routing. The handler intercepts ARP requests, performs cross-location address resolution, and returns IP addresses to the PE router, thereby eliminating the need for complex MAC learning and VSI tables while maintaining layer-2 VPN functionality
Solution Approach 2:
The patent changes the routing parameter from layer-2 MAC addresses to layer-3 IP addresses. Instead of performing MAC-based routing and maintaining MAC tables, the system uses IP address-based routing with an ARP handler that resolves MAC addresses when needed, simplifying the routing mechanism to standard layer-3 operations
2Reliability
If PE routers perform MAC-based routing and maintain MAC tables, then layer-2 address resolution is achieved, but ease of operation and maintenance deteriorate
Solution Approach 1:
The ARP request handler implements self-service by automatically performing address resolution when ARP requests are intercepted. The handler autonomously queries remote ARP handlers or centralized resolution systems to obtain IP addresses, eliminating the need for manual MAC table configuration and simplifying PE router operation
3Device complexity
If existing layer-3 PE routers are used without MAC learning capabilities, then device simplicity is maintained, but layer-2 VPN functionality is insufficient
Solution Approach 1:
The patent makes existing layer-3 PE routers universal by enabling them to handle both layer-3 IP routing and layer-2 VPN functions through the ARP request handler. The handler allows standard layer-3 routers to perform layer-2 address resolution and MAC/IP binding without requiring specialized MAC learning hardware or software
Data Source
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AI summary
A method of implementing a virtual private network (VPN) at a provider edge network node, including: receiving a data packet from a customer edge network node that includes layer-2 header information including a destination MAC address and a source MAC address; encapsulating the data packet, including layer-3 and layer-2 headers in another data packet; selecting a provider interface based upon the destination IP address, when the data packet has a destination IP address; selecting multiple provider interfaces that belong to the VPN, when the data packet has no destination IP address; and transmitting the encapsulated data packet to the selected provider interface(s).