Deterministic BIER Forwarding via Consolidated ECMP Tables
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Solution Overview
Problem
The Bit Index Explicit Replication (BIER) forwarding method in networks with Equal Cost Multipath (ECMP) or Link Aggregation Groups (LAGs) results in non-deterministic paths, making network operations, administration, and management difficult, and leading to inconsistent performance and out-of-order packet delivery due to path fluctuations with changes in multicast group membership.
Innovation Solution
Creating multiple forwarding tables with information associated with destinations, determining next hops and equal cost multipath next hops, and combining them into a single forwarding table that includes separate entries for multiple choices of routes, ensuring deterministic path selection based on hash values for ECMP packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If BIER forwarding method is used in networks with ECMP or LAGs, then forwarding speed is improved, but path determination becomes non-deterministic
Solution Approach 1:
The patent pre-calculates and stores multiple possible paths in the forwarding table before packets arrive. Each entry contains predetermined next-hop information for different destination combinations, eliminating the need for real-time path calculation and ensuring deterministic forwarding decisions while maintaining high forwarding speed.
Solution Approach 2:
The patent segments the path selection problem by creating separate forwarding table entries for different destination combinations. Each segment (table entry) contains pre-determined next-hop information for specific destination sets, allowing independent optimization and stable path determination for each segment while maintaining overall forwarding efficiency.
2Adaptability or versatility
If BIER forwarding method is used, then multicast group support is improved, but network management complexity increases
Solution Approach 1:
The forwarding table automatically adapts to different multicast group configurations through pre-calculated entries. When network topology or multicast group membership changes, the control plane regenerates the forwarding table with updated pre-computed paths, eliminating the need for manual configuration and simplifying network management while supporting flexible multicast groups.
Solution Approach 2:
The patent performs preliminary path calculation and stores results in the forwarding table before actual packet forwarding. This pre-computation handles the complexity of determining optimal paths for various multicast group combinations, allowing the forwarding plane to operate simply by looking up pre-determined next hops, thus reducing operational complexity.
3Measurement precision
If multiple forwarding tables are created and combined, then path determination accuracy is improved, but storage requirements increase
Solution Approach 1:
The patent merges multiple forwarding tables into a single consolidated forwarding table. Each entry in the combined table contains pre-calculated next-hop information for specific destination combinations, achieving accurate path determination while consolidating storage requirements into a single data structure that can be efficiently managed and updated.
Solution Approach 2:
The single forwarding table serves multiple functions by containing pre-computed next-hop information for various destination combinations. Each table entry is multi-functional, supporting different multicast group configurations and destination sets, thus reducing overall storage requirements compared to maintaining separate tables for each function.
Data Source
AI summary
A network device creates a forwarding table that includes information associated with a set of destinations in a network, and determines next hops for the set of destinations. The network device populates the forwarding table with information associated with the next hops, and stores the forwarding table. The forwarding table is used to forward a multicast packet toward a multiple destinations, and includes separate entries that depend upon routes the multicast packet is to traverse towards destinations with multiple choices for next hops.