Delaying Route Calculations in OSPF Virtual Aggregation
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Solution Overview
Problem
In virtually aggregated networks using the Open Shortest Path First (OSPF) protocol, data loss occurs when the central network device, acting as a Designated Router (DR), becomes inactive due to hardware faults, reboots, or software updates, leading to a brief downtime as other network devices immediately withdraw route information and take time to elect a new DR, resulting in dropped data requests during the transition.
Innovation Solution
Implementing a system where network devices delay route calculations until a new central network device is elected, generating and sharing link state information to maintain continuous data flow by postponing the withdrawal of route information, thereby reducing downtime and ensuring uninterrupted data communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If network devices immediately withdraw route information upon DR inactivity detection, then network convergence speed is improved, but data loss occurs during the transition period
Solution Approach 1:
The patent applies preliminary action by having the backup Designated Router (BDR) pre-calculate and prepare routing information before the current DR fails. When the DR becomes inactive, the BDR can immediately take over with pre-computed routing data, eliminating the need for other devices to withdraw and re-calculate routes, thus preventing data loss while maintaining fast convergence.
2Loss of information
If route calculations are delayed until new DR election, then data flow continuity is maintained, but network convergence time increases
Solution Approach 1:
The BDR performs preliminary route calculations and maintains routing information in advance, so when DR election is needed, the transition is immediate without delaying data flow. This resolves the contradiction by having routing information ready beforehand, eliminating both data loss and convergence delay.
Solution Approach 2:
The BDR acts as an intermediary that bridges the gap between DR failure and new DR election. It maintains routing information and can immediately assume the DR role, serving as a mediator that prevents both data flow interruption and excessive convergence time.
3Productivity
If Link Aggregation is used for node redundancy, then bandwidth and load balancing are improved, but re-convergence time during node failure is not sub-second
Solution Approach 1:
The patent implements preliminary action by pre-configuring a backup Designated Router that maintains routing information and adjacency data before failure occurs. When the active DR fails, the BDR can immediately take over without waiting for route recalculation, achieving sub-second convergence while maintaining the bandwidth and load balancing benefits of the multi-chassis aggregation.
Data Source
AI summary
A system and a method for eliminating data loss in a virtually aggregated network are described. A first network device may identify inactivity of a central network device present in a communication network. The central network device is responsible for distributing routing information between a plurality of network devices including the first network device. The first network device delays network route calculations until a second network device is elected from the plurality of network devices to perform functions of the central network device. The second network device generates link state information related to the plurality of network devices, and shares the link state information with the plurality of network devices. Upon receiving the link state information, the plurality of network device may resume the route calculations.