Dynamic Graceful Restart Time Renegotiation
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Solution Overview
Problem
In computer networks, double failures of primary and secondary routing control units can lead to significant traffic loss due to the incorrect expectation of neighboring routers that the failed router will reestablish the routing communication session, causing them to wait for an extended period before selecting alternative routes.
Innovation Solution
A network device dynamically renegotiates the restart period upon failure of the primary controller, reducing the restart time for the secondary routing control unit to a shorter duration, allowing neighboring routers to quickly select alternative routes in case of a double failure, and resetting the restart time to the original value upon recovery of the primary unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the router advertises a long restart time to support graceful restart, then the router can recover from primary controller failure, but neighboring routers will wait too long to select alternative routes in case of double failure
Solution Approach 1:
The patent applies dynamics by making the restart time parameter adjustable and renegotiable. The router can dynamically change the restart time value based on operational status - using a long restart time during normal operation to support graceful restart, and switching to a short restart time upon detecting controller failure to enable quick failover. This dynamic parameter adjustment resolves the contradiction between maintaining reliability and minimizing time loss.
Solution Approach 2:
The patent changes the restart time parameter from a fixed value to a variable that can be renegotiated. By implementing parameter changes, the system transitions from advertising a static long restart time to dynamically advertising either a long or short restart time based on the operational state of the primary controller, thus resolving the contradiction between graceful restart support and quick failover capability.
2Duration of action of stationary object
If the router uses a long restart time for graceful restart, then routing session reestablishment is supported, but network traffic convergence is delayed
Solution Approach 1:
The patent makes the restart time duration dynamic rather than static. The router advertises different restart time durations based on its operational state - a long duration when the primary controller is functional to enable graceful restart, and a short duration when the primary controller has failed to enable rapid traffic convergence. This dynamic adjustment resolves the contradiction between maintaining adequate restart time and achieving fast traffic convergence.
Solution Approach 2:
The patent implements feedback by monitoring the operational status of the primary controller and adjusting the advertised restart time accordingly. The router continuously assesses whether the primary controller is operational and provides feedback to the routing protocol by advertising appropriate restart time values, thus optimizing both graceful restart support and traffic convergence speed based on real-time system state.
3Reliability
If the router advertises support for graceful restart with standard restart time, then routing communication session can be reestablished, but double failure causes extended traffic loss
Solution Approach 1:
The patent applies dynamics by making the restart time parameter adjustable based on operational status. The router advertises a long restart time when the primary controller is operational to support graceful restart, but switches to advertising a short restart time upon detecting primary controller failure to minimize traffic loss in case of double failure. This dynamic parameter adjustment resolves the contradiction between maintaining session reestablishment capability and reducing traffic loss.
Solution Approach 2:
The patent applies preliminary action by pre-negotiating a short restart time with neighboring routers in advance of any actual failure event. When the primary controller fails, the router immediately utilizes this pre-negotiated short restart time value, allowing neighboring routers to quickly select alternative routes without waiting for an extended period, thus minimizing traffic loss while maintaining graceful restart capability.
Data Source
AI summary
Techniques are described for reducing the impact of failure of a primary and a secondary routing control unit within a network device, i.e., a double-failure of the network device. For example, a network device, such as a router, initially establishes a routing communication session between a primary routing control unit of the router and a neighboring router. The initial routing communication session has a first restart time in the event of a session failure. The router reestablishes the routing communication session with a secondary routing control unit upon failure of the primary routing control unit. The reestablished routing communication session has a second restart time that is less than first restart time. Upon recovery of the failed routing control unit, the secondary routing control unit renegotiates the restart time associated with the session to an increased value with the neighboring routers to which the reduced restart time was initially advertised.