Dual Homing Ethernet Interconnection via Bridge Priority
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Solution Overview
Problem
Existing methods for dual homing in Ethernet and VPLS networks require complex signaling protocols like xSTP, which complicates interconnection between networks under different administrations and does not support full redundancy, while simpler approaches lack the ability to prevent layer 2 loops effectively.
Innovation Solution
A method that uses bi-directional virtual links with Hello signaling between peer elements to elect a designated forwarder, eliminating the need for xSTP and ensuring loop-free operation by blocking unnecessary connections, thereby simplifying network interconnection and reducing switchover times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If xSTP signaling protocol is used to prevent layer 2 loops in dual homing configurations, then loop-free operation is ensured, but device complexity and signaling overhead increase significantly
Solution Approach 1:
The patent extracts the loop prevention function from the complex xSTP signaling protocol and implements it through a simpler mechanism using bridge priority values in LDP auto-discovery messages. Instead of running full xSTP signaling between all PE-CE interfaces, the solution extracts only the essential loop prevention capability by comparing bridge priority values, thereby reducing signaling complexity while maintaining reliability.
Solution Approach 2:
The patent introduces bridge priority values as an intermediary mechanism to mediate loop prevention. Rather than direct complex signaling between peers, each PE/CE device independently determines its role (root or non-root) based on comparing bridge priority values, acting as a simple mediator that prevents loops without requiring ongoing complex signaling interactions.
2Reliability
If xSTP protocol is deployed across all networks for full redundancy support, then fault tolerance is improved, but implementation complexity and operational difficulty increase
Solution Approach 1:
The patent enables networks to self-determine their roles in the dual homing configuration through automatic comparison of bridge priority values. Each PE/CE device independently identifies itself as root or non-root based on its own bridge priority value relative to its peer, eliminating the need for manual configuration or complex operational intervention to establish redundant paths.
Solution Approach 2:
The patent changes the operational approach from manual xSTP protocol management to automatic parameter-based role assignment. By using bridge priority values as a simple parameter to determine root/non-root status, the system automatically configures redundant paths without requiring operators to manage complex xSTP signaling, thereby improving ease of operation while maintaining full redundancy.
3Device complexity
If simpler connection methods are used instead of xSTP, then device complexity is reduced, but ability to prevent layer 2 loops effectively is compromised
Solution Approach 1:
The patent introduces bridge priority values as a simple intermediary parameter that enables loop prevention without complex signaling. Each device compares its bridge priority value with its peer's value to determine whether to act as root or non-root, providing a mathematically guaranteed loop-free topology through this simple numerical comparison mechanism.
Solution Approach 2:
The patent changes from complex protocol-based loop prevention to a simple parameter comparison approach. By using bridge priority values (numerical parameters) to determine forwarding behavior, the system achieves loop prevention through a simple parameter change mechanism that is far less complex than xSTP signaling while maintaining equivalent or superior reliability.
4Reliability
If dual homing connections are established for full redundancy, then fault tolerance is improved, but risk of creating layer 2 loops increases
Solution Approach 1:
The patent applies preliminary anti-action by pre-configuring bridge priority values that automatically prevent loops before they can form. When dual homing connections are established, the bridge priority comparison mechanism proactively determines which PE/CE interface should forward traffic and which should block it, preventing loop formation in advance rather than reacting to loops after they occur.
Solution Approach 2:
The bridge priority value acts as an intermediary that mediates between the need for redundant connections and the need to prevent loops. By introducing this simple numerical parameter as a mediator, the system can establish dual homing connections for redundancy while the bridge priority comparison automatically prevents harmful loop formation through this intermediary control mechanism.
Data Source
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AI summary
Technique for interconnecting a first communication network and a second communication network, for example layer 2 Ethernet networks, which uses a fully or partially redundant dual homing configuration. The configuration includes: at least three network elements where at least two of them are peer elements belonging to the second network, and at least two traffic lines respectively associated with the peer elements and connecting the first and the second networks via the three network elements. The technique comprises establishing a bi-directional signaling between the peer elements and, based on the signaling information, deciding which traffic line should forward the traffic.