Ethernet Ring Interworking with Spanning Tree via BPDU Transport
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Solution Overview
Problem
Interconnecting an Ethernet ring network with a spanning tree controlled Ethernet network creates a single point of failure, as the two networks running different control planes require nodes on the ring to determine which nodes are part of the spanning tree, while maintaining the integrity of both network operations.
Innovation Solution
Transporting spanning tree control packets as data frames over the Ethernet ring allows the ring to appear as a single link to the spanning tree protocol, enabling its extension without affecting the ring's internal structure, and using bridge nodes to interconnect the networks while decoupling the Ethernet ring control protocol from the spanning tree protocol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an Ethernet ring network is interconnected with a spanning tree controlled Ethernet network at multiple nodes, then network reliability and redundancy are improved through dual homing, but the complexity of control plane management increases due to the need to determine which nodes are part of the spanning tree while maintaining integrity of both network operations
Solution Approach 1:
The patent introduces a virtual link as an intermediary between the Ethernet ring network and the spanning tree controlled network. This virtual link abstracts the complex multi-node interconnection into a single logical connection, allowing the ring network to appear as a single link to the spanning tree protocol while enabling dual homing at multiple physical nodes. The virtual link mediates between the two different control planes, preventing complexity from propagating into both networks.
2Adaptability or versatility
If spanning tree control packets are transported as data frames over the Ethernet ring, then the ring network can be integrated with the spanning tree protocol without affecting the ring's internal control structure, but the ring nodes must forward these control packets without processing them, requiring careful protocol handling
Solution Approach 1:
The patent segments the control plane functions by separating spanning tree control packet forwarding from ring control packet processing. Ring nodes are configured to recognize spanning tree control packets transported as data frames and forward them without processing, while maintaining full processing capability for ring control packets. This segmentation allows both protocols to coexist on the same physical infrastructure without interference, enabling network integration while simplifying node operation.
Data Source
AI summary
To enable an Ethernet ring to be dual homed into a spanning tree protocol controlled Ethernet network, spanning tree control packets (Bridged Protocol Data Units or BPDUs) are transported as data frames over the Ethernet ring. This allows the Ethernet ring to appear as a single link to the spanning tree protocol so that the spanning tree can extend over the link. However, since the spanning tree does not have visibility as to the internal structure of the ring, the spanning tree cannot block links on the Ethernet ring network. Conversely, BPDUs from the Ethernet ring are not transmitted into the Ethernet domain that is implementing the spanning tree, so that the spanning tree is not affected by the control mechanism in place on the Ethernet ring network.