Spanning Tree Protocol State Machine Distribution
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Solution Overview
Problem
The Spanning Tree Protocol requires significant processing load to maintain a loop-free topology in networks, especially when topology changes occur, which can lead to delays and the risk of creating switching loops due to the complex interconnectedness of state machines across central controllers and line cards.
Innovation Solution
A method is introduced where the Spanning Tree Protocol process is managed by distributing state machines between a central controller's Protocol Manager and port controllers' Neighbour Managers, with the Protocol Manager handling the UPDATE state and Neighbour Managers handling other states, allowing asynchronous information exchange and minimizing load on the central controller while preventing loop creation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the Spanning Tree Protocol uses a centralized state machine processing model on the central controller, then the protocol implementation is simple to manage, but the processing delays increase and network responsiveness deteriorates
Solution Approach 1:
The patent segments the Spanning Tree Protocol state machines into two categories: UPDATE state machines that remain on the central controller, and other state machines (such as Port Information, Port Role Selection, Port Timers) that are distributed to line cards. This segmentation allows parallel processing of state machine updates across multiple processing elements, reducing processing delays while maintaining manageable complexity through clear division of responsibilities.
2Speed
If the Spanning Tree Protocol distributes state machines across multiple processing elements, then the network responsiveness improves, but the risk of creating switching loops increases due to complex interconnectedness
Solution Approach 1:
The patent implements preliminary action by requiring the central controller to execute UPDATE state machine processing first, determining port role changes and topology updates before line cards execute their state machines. Line cards receive updated configuration information from the central controller before making local state transitions, ensuring that loop-free topology is maintained while still enabling parallel processing for improved responsiveness.
Solution Approach 2:
The patent implements feedback mechanisms where line cards report their state machine execution results and port status changes back to the central controller. The central controller uses this feedback to verify topology consistency and coordinate further updates, ensuring that distributed processing does not compromise the loop-free guarantee while maintaining high network responsiveness.
3Stability of the object's composition
If the central controller processes all state machine updates, then the protocol consistency is maintained, but the processing load on the central controller increases
Solution Approach 1:
The patent segments processing load by assigning UPDATE state machine execution to the central controller while distributing other state machine execution to line cards. This segmentation reduces the central controller's processing load by moving routine state transitions to distributed processing elements, while the central controller maintains protocol consistency through centralized UPDATE processing and coordination.
Solution Approach 2:
The patent uses the UPDATE state machine on the central controller as an intermediary that coordinates between the centralized protocol management function and distributed line card processing. The UPDATE state machine processes topology changes and generates update messages that are sent to line cards, which then execute their state machines based on these updates, effectively mediating between consistency requirements and load distribution.
Data Source
AI summary
The invention relates to managing operation of a spanning tree protocol process in a network bridge having a central controller and one or more port controllers, each for controlling one or more ports of said network bridge. The spanning tree protocol process comprises a plurality of state machines including a Port Information state machine. The Port Information state machine comprises an UPDATE state and a plurality of other states. The invention involves running a Protocol Manager on a central controller, wherein the Protocol Manager owns the UPDATE state such that updates are carried out by the Protocol Manager. The Neighbor Managers on each of the port controllers owns the plurality of other states of the Port Information state machine, such that updates are carried out by the respective Neighbor Manager on said port controller. This allows the Protocol Manager and the Neighbor Managers to operate without having to force one to pause whilst work is done on the other.