Enhanced Spanning Tree Protocol for N-Node VLT Link Aggregation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional spanning tree protocols block Inter-Chassis Links (ICLs) between Virtual Link Trunking (VLT) nodes, even when there are no data loops, leading to unnecessary bandwidth waste and operational inefficiencies in n-node VLT systems.
Innovation Solution
An enhanced spanning tree protocol engine is implemented in link aggregation node devices, allowing multiple root ports and redesignating alternate ports as second root ports to prevent loop blocking, enabling the spanning tree protocol to operate without blocking ICLs and maintaining network convergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spanning tree protocol is used to prevent data loops, then network loop prevention is achieved, but Inter-Chassis Links are unnecessarily blocked causing bandwidth waste
Solution Approach 1:
The patent applies local quality by treating Inter-Chassis Links differently from regular network links. The spanning tree protocol is modified to recognize ICLs as special links that should not be blocked, even when they would normally be considered part of a loop. This localized differentiation allows the system to maintain loop prevention for regular traffic while preserving ICL bandwidth for synchronization and control traffic.
Solution Approach 2:
The patent segments the network into two functional zones: the VLT fabric interconnect (ICLs between VLT nodes) and the external network fabric. By separating these functions, the system can apply different spanning tree rules to each segment - allowing ICLs to remain active while blocking only those external links that would create loops in the broader network.
2Reliability
If conventional spanning tree protocol blocks ICLs to prevent loops, then loop prevention is maintained, but network convergence and resilience are reduced
Solution Approach 1:
The enhanced spanning tree protocol implements local quality by creating a special exception for ICL ports. These ports are marked with a unique identifier that prevents them from being selected as root ports or alternate ports, thereby excluding them from spanning tree blocking decisions. This allows the network to converge faster since ICLs remain continuously active for fabric synchronization.
3Productivity
If multiple root ports are allowed in enhanced spanning tree protocol, then ICL blocking is prevented, but protocol complexity increases
Solution Approach 1:
The patent applies dynamics by making the spanning tree protocol behavior adaptive based on link type. The system dynamically identifies ICL ports through special identifiers and adjusts its behavior accordingly - allowing multiple root ports when ICLs are detected, while maintaining traditional single-root-port behavior for regular network links. This dynamic adaptation resolves the contradiction between improved ICL utilization and protocol complexity.
Data Source
AI summary
A spanning tree enabled n-node VLT system includes the STP running on VLT node devices that include a first VLT node device coupled to a networking device by a LAG and designated as a root bridge via the STP. A second VLT node device coupled to the networking device is part of the LAG. ICLs couple the second VLT node device to the first VLT node device. An enhanced STP engine running on the each of the VLT node devices determines that the STP has designated a first port providing one of the ICLs as a first root port, and a second port providing one of the ICLs as an alternate port. In response, the enhanced STP engine redesignates the second port as a second root port.