Throwback Routers for Fault Tolerant Folded Clos Networks
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Solution Overview
Problem
Folded Clos networks face increased routing complexity and performance degradation due to the use of multiple routers and routing protocols, which can lead to undesirable performance degradation and reduced fault tolerance, especially under link failure conditions.
Innovation Solution
The implementation of throwback routers within the folded Clos network, functioning as modified tier 1 routers, allows for failover routing of unroutable packets by selecting alternative tier 2 routers, thereby maintaining network resilience without requiring modifications to existing routing protocols or devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multiple low-connectivity networking devices are used to reduce cost, then device cost is reduced, but routing complexity increases
Solution Approach 1:
The network is segmented into multiple tiers (tier-1, tier-2, tier-3) with specialized functions at each level. Tier-1 routers handle customer connections, tier-2 routers provide backbone connectivity, and tier-3 routers offer additional routing capacity. This segmentation allows each router to have fewer connections while maintaining overall network functionality through the hierarchical structure.
Solution Approach 2:
The patent introduces a vertical dimension to network routing by adding multiple tiers, transforming the traditional flat network structure into a three-dimensional hierarchical architecture. This allows traffic to flow through multiple levels (customer router → tier-1 → tier-2 → tier-3 → destination), reducing the connectivity requirements at each individual node while providing multiple path options.
2Device complexity
If routing protocols are simplified to reduce complexity, then routing complexity is reduced, but fault tolerance under link failure conditions deteriorates
Solution Approach 1:
The network establishes preliminary routing paths through the hierarchical structure before failures occur. Each tier is pre-configured with connectivity to multiple levels, creating redundant paths in advance. When a link failure occurs, traffic can immediately switch to alternative paths through different tiers without requiring complex real-time protocol negotiations.
Solution Approach 2:
The tier-2 and tier-3 routers act as intermediaries that simplify the routing burden on tier-1 customer routers. These intermediate routers absorb the complexity of path selection and failover logic, allowing customer routers to use simpler routing protocols while maintaining fault tolerance through the intermediary layers.
3Productivity
If link aggregation protocols are used to improve efficiency, then routing efficiency is improved, but fault tolerance capability is reduced
Solution Approach 1:
Instead of aggregating links into a single logical connection, the patent segments the network into multiple independent tier levels. Each tier provides separate routing capacity, and traffic can be distributed across tiers rather than being bound to a single aggregated link. This segmentation maintains efficiency through load distribution while preserving fault tolerance through independence.
Solution Approach 2:
The patent moves routing from a two-dimensional link aggregation model to a three-dimensional hierarchical model. Rather than combining multiple links into one logical path, traffic can traverse multiple dimensions (tiers) simultaneously, providing both efficiency through parallel paths and fault tolerance through dimensional diversity.
Data Source
AI summary
Systems and methods are described to provide fault tolerant folded Clos networks. A folded Clos network is disclosed including a set of tier 1 routers interconnected with a set of tier 2 routers. Tier 1 routers are configured to view a set of tier 2 routers as a single aggregate router. Accordingly, tier 1 routers are unaware of faults between tier 2 routers and additional tier 1 routers. A throwback router is connected to each tier 2 router to facilitate handling of data under such fault conditions. When a tier 2 router receives undeliverable data, the data is passed to a throwback router, which retransmits the data to an additional tier 2 router. Data that is retransmitted multiple times can be disregarded by the throwback router.