Segment Routing Global Block Slicing for Label Allocation
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Solution Overview
Problem
In communications networks employing segment routing, existing prefix segment identifiers (SIDs) are limited in scope, requiring all nodes in an IGP domain to process and allocate unique labels for prefix SIDs, which can lead to unnecessary processing by nodes outside specific planes or paths, and prevent reassignment of labels across different planes or paths within the same domain.
Innovation Solution
A method is introduced to configure and use prefix SIDs by slicing the segment routing global block (SRGB) into multiple slices, each identified by a unique slice identifier, allowing nodes to determine if they belong to a specific slice and only process and allocate labels within that slice, thereby enabling reuse of SIDs across different prefixes or paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all nodes in an IGP domain process and allocate unique labels for prefix SIDs, then label uniqueness is ensured, but unnecessary processing occurs by nodes outside specific planes or paths
Solution Approach 1:
The patent segments the IGP domain into multiple planes or slices, where each plane is identified by a plane identifier. Nodes only process prefix SIDs relevant to their assigned plane, rather than processing all SIDs domain-wide. This segmentation allows nodes to filter and process only the subset of SIDs pertinent to their specific plane, reducing unnecessary processing while maintaining label uniqueness within each plane through plane-specific label allocation.
2Reliability
If unique labels are allocated for each prefix SID across the domain, then label uniqueness is maintained, but label reuse across different planes or paths is prevented
Solution Approach 1:
The patent implements local quality by allowing label values to be plane-specific rather than domain-wide. Each plane can allocate labels from its own label space, enabling the same label value to be reused in different planes without causing conflicts. This local quality approach maintains label uniqueness within each plane while enabling label reuse across planes, thereby increasing the versatility and adaptability of the label allocation system.
3Loss of information
If nodes process all prefix SIDs in the domain, then complete routing information is available, but processing overhead increases for nodes outside relevant planes
Solution Approach 1:
The patent applies preliminary action by pre-associating nodes with specific planes using plane identifiers before SID processing occurs. When a node receives routing information, it can immediately filter SIDs based on its plane assignment without processing all SIDs. This preliminary plane identification enables nodes to efficiently select and process only the routing information relevant to their plane, reducing processing overhead while ensuring that each node has complete routing information for its assigned plane.
Data Source
AI summary
The same prefix segment identifier (SID) may be configured and/or used for either (A) more than one prefix within an interior gateway protocol (IGP) domain, or (B) one prefix with more than one path computation algorithm within the IGP domain by: (a) receiving, by a node in the IGP domain, an IGP advertisement including both (1) a prefix SID and a segment routing global block (SRGB) slice identifier; (b) determining whether or not the SRGB slice identified by the SRGB slice identifier is provisioned on the node; and (c) responsive to a determination that the SRGB slice identified by the SRGB slice identifier is not provisioned on the node, not processing the prefix SID included in the received IGP advertisement, and otherwise responsive to a determination that the SRGB slice identified by the SRGB slice identifier is provisioned on the node, (1) processing the prefix SID and SRGB slice to generate a unique, per SRGB slice, MPLS label for the prefix, and (2) updating a label forwarding information base (LFIB) for the node using the unique, per SRGB slice, label for the prefix and the prefix.