Bridge Assurance Sub-Engine for Unidirectional Failure Detection
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Solution Overview
Problem
Conventional spanning tree protocols in computer networks may fail to detect unidirectional failures and loops, leading to network congestion and outages, especially due to faulty network interface cards, busy microprocessors, or software errors, which can cause undetected failures and formation of loops.
Innovation Solution
A bridge assurance sub-engine is integrated into intermediate network devices to periodically send BPDU messages from Root, Alternate, and Backup ports, and utilize timers to detect failures, preventing ports from transitioning to forwarding states if errors are detected, thus maintaining a loop-free topology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spanning tree protocol is used to prevent loops, then network topology is maintained loop-free, but unidirectional failures and software errors cannot be detected, leading to undetected loops and network congestion
Solution Approach 1:
The patent introduces BPDU messages as intermediary carriers that transport assurance information between bridges. These messages serve as a mediator to convey the operational status and topology information, enabling detection of unidirectional failures without requiring direct inspection of link physical states. The BPDU messages carry assurance data that allows bridges to verify bidirectional communication functionality.
Solution Approach 2:
The patent implements a feedback mechanism where bridges send assurance BPDUs periodically and monitor the receipt of these messages from neighboring bridges. If a bridge stops receiving assurance BPDUs from a neighbor, it detects a unidirectional failure. This feedback loop enables continuous monitoring of bridge operation and automatic detection of failures that would otherwise remain undetected by conventional STP.
2Reliability
If bridges send BPDUs only from designated ports, then protocol overhead is reduced, but failures at non-designated ports cannot be detected
Solution Approach 1:
The patent makes BPDU messages multi-functional by using them for both conventional spanning tree operation and bridge assurance monitoring. The same BPDU messages serve dual purposes: maintaining the spanning tree topology and providing failure detection capability. This eliminates the need for separate assurance messages, so the quantity of messages sent increases minimally while achieving enhanced reliability.
Solution Approach 2:
The patent employs preliminary action by having bridges send assurance BPDUs from all ports (not just designated ports) before failures occur. This proactive sending of assurance messages from multiple ports enables pre-detection of potential failure conditions. By maintaining this continuous assurance message transmission, bridges can detect failures immediately when messages stop arriving, rather than waiting for topology changes to manifest.
Data Source
AI summary
A system and method assures the proper and continued operation of intermediate network devices, such as bridges, in a computer network. The bridge includes a spanning tree protocol (STP) engine, which is configured to have a bridge assurance (BA) sub-engine. The STP engine assigns the bridge's ports to one of a Root, Alternate, Designated or Backup Role. The BA sub-engine directs the STP engine to issue configuration messages from all ports to which neighboring bridges are coupled, including ports assigned to the Root and Alternate roles. The BA sub-engine further looks for the receipt of BPDU messages from neighboring bridges and employs one or more timers to determine whether the neighboring bridges are continuing to operate properly.