Entropy Label Pointer for Segment Routing Overhead
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Solution Overview
Problem
Existing segment routing methods using entropy labels for multi-protocol label switching (MPLS) data planes face inefficiencies due to increased memory access costs and label stack overhead, particularly in high-speed networks like Radio Access Networks (RAN) and Mobile Backhaul Networks (MBH), where bandwidth is scarce and payload is small.
Innovation Solution
The introduction of re-usable entropy labels (ELs) that maintain a single EL throughout the label stack, with additional metadata stored on the forwarding path to efficiently process packets without extra memory accesses, adhering to RFC 3031 processing rules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single entropy label is used for all segments, then the label stack size is reduced, but intermediate LSRs have to walk the label stack deeper to access the EL, increasing memory access time and cost
Solution Approach 1:
The patent introduces an Entropy Label Pointer (ELP) as an intermediary element in the label stack. The ELP stores the position (offset) of the entropy label, allowing intermediate LSRs to directly access the EL without walking through the entire label stack. This mediator enables fast random access to the EL while maintaining a compact single-EL label stack structure.
2Adaptability or versatility
If an entropy label is used per segment, then ECMP load balancing is improved, but the label stack size grows significantly, increasing packet header overhead
Solution Approach 1:
The patent merges the functionality of multiple per-segment entropy labels into a single shared entropy label that is reused across all segments. The ELP mechanism allows this single EL to serve multiple segments by providing direct access, eliminating the need to duplicate EL/ELI pairs for each segment while maintaining ECMP load balancing capabilities.
Solution Approach 2:
The single entropy label serves a universal function across all segments in the label stack, rather than being dedicated to a specific segment. The ELP enables this universal EL to be efficiently accessed for ECMP decisions at any segment boundary, making the EL multi-functional across different segments without requiring separate EL instances.
3Adaptability or versatility
If the label stack is made deeper to include multiple EL/ELI pairs, then ECMP load balancing per segment is enabled, but memory access complexity and cost increase significantly
Solution Approach 1:
The ELP acts as a mediator that simplifies memory access complexity. Instead of requiring deep label stack walks to access ELs buried beneath multiple SIDs, the ELP provides a direct pointer to the EL location, reducing memory access complexity from O(n) proportional to label stack depth to O(1) constant time access.
Data Source
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AI summary
A method and apparatus for using entropy labels in segment routed networks is disclosed. A single entropy label identifier (ELI) and a single entropy label (EL) are provided for a label stack. The ELI and EL are inserted directly below a top-most label in the label stack. Furthermore, a method and apparatus for using entropy labels in segment routed networks is described. A top-most label of a label stack of a packet is examined. A NHLFE for the packet is determined. A determination is made as to whether or not an ELI is below the top-most label. An EL is re-used when the ELI is determined to be present. The ELI and the re-used EL are inserted directly below a label associated with the NHLFE in a new label stack.