Layer 2 Network Device Fast Proposal Message Retransmission
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Solution Overview
Problem
The existing Rapid Spanning Tree Protocol (RSTP) standard requires a minimum of 1 second for network recovery after a lost proposal or agreement message, leading to network traffic outages due to delayed port transition from discarding to forwarding state.
Innovation Solution
Implementing a fast retransmission method in Layer 2 network devices that transmits proposal messages more frequently than the standard RSTP interval, using a configurable timer system to retransmit messages before the expiration of the Bridge Hello Time, thereby reducing network recovery time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the L2D transmits proposal messages at the standard RSTP interval (Hello Time), then the protocol maintains compatibility with the standard, but the network recovery time is delayed by at least 1 second when messages are lost
Solution Approach 1:
The patent implements periodic retransmission of proposal messages at intervals shorter than the standard Bridge Hello Time. The L2D transmits proposal messages repeatedly at a reduced interval (e.g., 0.5 seconds instead of 2 seconds) when operating in rapid convergence mode, thereby increasing the probability of successful message delivery and reducing network recovery time when messages are lost.
Solution Approach 2:
The patent changes the transmission interval parameter from the standard Bridge Hello Time value to a shorter custom interval. By modifying this timing parameter, the system achieves faster retransmission capability while maintaining the same message format and protocol structure, thus improving recovery speed without breaking protocol compatibility.
2Productivity
If the L2D retransmits proposal messages more frequently than the standard interval, then the network recovery time is reduced, but the message transmission frequency exceeds the standard RSTP definition
Solution Approach 1:
The patent implements dynamic retransmission behavior that adapts to the operational mode. When rapid convergence mode is enabled, the system dynamically switches to a shorter retransmission interval. This dynamic adjustment allows the system to optimize for speed when needed while maintaining standard behavior otherwise, managing complexity through conditional logic rather than fixed behavior.
Solution Approach 2:
The system performs preliminary configuration by setting the rapid convergence mode flag in advance. When this flag is set, the L2D pre-configures itself to use the shorter retransmission interval, preparing the system for faster operation before actual message loss occurs. This preliminary setup simplifies the control mechanism by using a single flag to trigger the behavioral change.
Data Source
AI summary
In one aspect, the invention provides a layer 2 network device that implements a fast retransmission method that causes the layer 2 network device to transmit proposal messages more frequently than defined in the RSTP standard. By transmitting proposal messages (e.g., proposal RST BPDUs) more frequently, the network device can significantly reduce the duration of a network traffic outage caused by a lost proposal message or a lost agreement message.