Router Bad Link State Request Handling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In packet networks using link state protocols like OSPF, bad link state advertisement requests can cause router adjacencies to fail, leading to delayed convergence and increased network loads, as there is no standardized way to handle erroneous requests without terminating adjacency formation.
Innovation Solution
A router responds to a bad link state request with a no-effect link state update having a specific sequence number and age, ensuring it appears older than valid updates, allowing adjacency formation to continue without affecting the network, and implementing policies to manage erroneous requests based on error profiles and authorization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a router terminates adjacency formation upon receiving a bad link state request, then the network maintains strict protocol compliance, but network convergence is delayed and router loads increase
Solution Approach 1:
The patent converts the harmful effect of bad link state requests into a beneficial mechanism by implementing a no-effect link state update response. Instead of terminating the adjacency when a bad request is detected, the router sends a special response packet that acknowledges the request but ensures it has no effect on the link state database. This allows the adjacency formation to continue successfully while maintaining protocol integrity, thereby reducing convergence time and avoiding unnecessary router load.
2Productivity
If a router sends a no-effect link state update with specific sequence number and age, then adjacency formation continues without disruption, but the protocol complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the sequence number and age fields in the link state update packet to specific values that indicate a no-effect response. The sequence number is set to a value greater than the requesting router's current sequence number, and the age is set to a value that ensures the update will not be installed in the link state database. These parameter modifications allow the router to maintain compatibility with existing OSPF implementations while implementing the no-effect response mechanism, thus avoiding excessive protocol complexity.
Data Source
AI summary
A link-state protocol running on a router requires that an adjacent neighbor router in the same network maintain a synchronized link state database in order to form the adjacency. Should the neighbor request link state information that the router does not possess, normally the adjacency is broken, causing a restart and network instability. The described embodiments allow adjacencies to form and be maintained even when the neighbor makes at least some types of “bad” requests for link state information. Embodiments that operate with and without the knowledge and cooperation of the neighbor are described.