RSVP Node Recovery Time Parameter for Label-Switched Path Rebuild
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Solution Overview
Problem
Existing RSVP protocols struggle to effectively restart multiple RSVP processes in a network, particularly when failures occur concurrently, leading to incomplete recovery of label-switched paths due to the inability to detect the recovery mode of neighboring nodes.
Innovation Solution
Implementing a method where RSVP nodes send Hello messages with a non-zero Recovery Time value during recovery mode and switch to zero Recovery Time value upon completion, allowing nodes to determine the recovery status and adjust label usage accordingly, and introducing a Recovery ERO object to ensure consistent ERO expansion during nodal fault recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RSVP nodes use traditional Hello messages without Recovery Time values, then message simplicity is maintained, but the ability to detect recovery mode of neighboring nodes is lost
Solution Approach 1:
The patent adds a Recovery Time parameter to the existing Hello message structure. This parameter changes state (non-zero during recovery, zero when normal) to indicate the recovery mode of the sending node, enabling reliable detection without fundamentally changing the message protocol
Solution Approach 2:
The Recovery Time value acts as an intermediary signal that carries recovery status information between RSVP nodes. Instead of requiring complex recovery mode detection mechanisms, the parameter serves as a simple mediator that conveys the necessary state information
2Reliability
If RSVP nodes restart concurrently without recovery status detection, then automatic restart is achieved, but incomplete recovery of label-switched paths occurs
Solution Approach 1:
The patent implements a feedback mechanism where RSVP nodes send Hello messages with Recovery Time values to indicate their recovery status. Receiving nodes use this feedback to determine whether to use recovery labels or suggested labels when forwarding PATH messages, ensuring complete and coordinated recovery across multiple nodes
Solution Approach 2:
The patent enables nodes to take preliminary actions based on the Recovery Time parameter. When a node detects that a neighbor is in recovery mode (non-zero Recovery Time), it can proactively prepare appropriate recovery labels and PATH message handling, ensuring seamless recovery without waiting for failure conditions
3Reliability
If nodes send PATH messages without checking neighbor recovery status, then message processing speed is maintained, but incorrect label usage occurs
Solution Approach 1:
The patent uses the Recovery Time parameter to control PATH message processing behavior. When Recovery Time is non-zero, nodes use recovery labels; when zero, nodes use suggested labels. This parameter-driven approach ensures label usage accuracy while keeping processing logic relatively simple
Solution Approach 2:
The patent applies different processing qualities to PATH messages based on the recovery status of neighboring nodes. Each node independently determines its processing mode (recovery or normal) based on local detection of neighbor Recovery Time values, allowing accurate label usage without requiring complex global coordination
Data Source
AI summary
An RSVP node that has crashed and restarted sends a non-zero Recovery Time value in a Restart_Cap object of a Hello message. Other nodes receiving such messages can detect, based on the non-zero Recovery Time value, that the sending node is restarting. In particular, a first RSVP node can detect whether a second, neighbor node has restarted regardless of the order of restart with respect to the first and second nodes. As a result, the first node can determine whether to forward PATH messages with Recovery Label or Suggested Label, as appropriate or necessary to rebuild label-switched paths with crashed and restarted nodes. Therefore, when multiple RSVP nodes crash relatively concurrently, the multiple nodes can restart gracefully and automatically detect what kind of communication to use in order to rebuild label-switched paths among themselves.