VPLS Packet Forwarding via Dynamic Path Selection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for address learning in network elements, such as IEEE 802.1ad and IETF full-meshed VPLS, either fail to guarantee shortest paths for packet forwarding due to tree-based structures or do not scale well due to broadcast reliance, leading to potential traffic black-holing and partial mesh connectivity issues.
Innovation Solution
A method that allows packets to be forwarded directly over a shortest path if a direct link is available, and falls back to a tree-based forwarding if the link is unreachable, while maintaining mappings between MAC and IP addresses to ensure robust address learning and avoid looping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tree-based forwarding is used for address learning, then loops are avoided, but shortest path forwarding is not guaranteed
Solution Approach 1:
The patent implements dynamic path selection by maintaining both tree-based and direct routing information in the forwarding table. The system dynamically chooses between tree-based forwarding (for loop avoidance) and direct shortest path forwarding (for optimality) based on real-time link status and routing information, making the forwarding behavior adaptable rather than static
Solution Approach 2:
The forwarding decision process is segmented into multiple independent components: tree-based forwarding entries, direct routing entries, and failure detection mechanisms. This segmentation allows the system to independently manage loop prevention and path optimization functions without one compromising the other
2Speed
If full-meshed VPLS with broadcast to all NEs is used, then shortest path forwarding is achieved, but the method does not scale well
Solution Approach 1:
Instead of implementing uniform broadcast to all network elements, the patent applies different forwarding strategies to different destinations based on local forwarding table entries. Each NE maintains specific direct routing information for known destinations, applying optimal direct forwarding locally rather than universal broadcast, thus improving scalability while maintaining path optimality where applicable
3Reliability
If pseudowires are required for full connectivity, then VPLS can emulate LAN service, but partial mesh connectivity causes traffic black-holing
Solution Approach 1:
The patent prepares for potential link failures by maintaining alternative tree-based forwarding entries in advance. When direct pseudowire links fail, the system already has pre-configured tree-based paths available to redirect traffic, preventing black-holing without requiring complex real-time rerouting decisions
Solution Approach 2:
The patent introduces tree-based forwarding as an intermediary mechanism between direct pseudowire links and final destination delivery. When direct links are unavailable, traffic is routed through intermediate nodes via tree-based paths, allowing partial mesh connectivity to still achieve full service coverage
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A system and method are provided for forwarding packets through a fully meshed communication network when the destination MAC address may not be known. Each network element maintains a mapping of MAC addresses and IP addresses, each MAC address having an associated IP address which indicates to where packets are to be forwarded. If a network element receives a packet but has not yet associated an IP address with the destination MAC address of the packet, then the network element forwards the packet along a tree. If a network element receives a packet and has associated an IP address with the destination MAC address, in other words has learned of the IP address for the MAC address, the network element sends the packet directly to the IP address unless a direct link to the IP address is not available. If a direct link is not available, the network element forwards the packet along the tree. A network element receiving a packet from an attachment circuit encapsulates its own IP address in the message, permitting other network elements to learn of the IP address associated with the source MAC address. The invention provides reliable forwarding of packets to both known and unknown destination MAC addresses, while taking advantage of shortest paths provided by a fully meshed network.