Anycast Prefix Segment Path Computation Using Preferred Metrics

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Solution Overview

Problem

Current Segment Routing technologies lack a mechanism to select different metric types for path computation with anycast prefix segments, limiting flexibility in traffic engineering and practical use cases.

Innovation Solution

Incorporation of a new attribute in the Extended IP Reachability Type-Length-Value (TLV) for advertising a preferred metric type over Interior Gateway Protocol (IGP) for anycast groups, allowing a Path Computation Engine (PCE) to use this preferred metric for path computation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If IGP metric is used for path computation towards anycast prefixes, then path computation is simple and standardized, but traffic engineering flexibility is limited

Engineering Contradiction:

Improvetraffic engineering flexibilityVSAvoidpath computation complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces a new attribute in the Extended IP Reachability TLV that specifies a preferred metric type for anycast groups. This allows the metric parameter to be changed from the default IGP metric to other metrics (such as latency, bandwidth, or custom metrics) on a per-anycast-group basis, enabling flexible traffic engineering while maintaining standardized IGP operations for groups that don't require special metrics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The solution makes the metric selection dynamic by allowing different metric types to be advertised for different anycast groups through the TLV attribute. The Path Computation Engine can dynamically select the appropriate metric type based on the specific anycast group requirements, rather than using a static IGP metric for all anycast computations

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If multiple metric types are supported for path computation, then traffic engineering capability is improved, but protocol complexity increases

Engineering Contradiction:

Improvemetric type selectionVSAvoidprotocol structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent uses the existing Extended IP Reachability TLV structure as an intermediary to carry the preferred metric type attribute. This approach leverages the already-established IGP extension mechanism, avoiding the need for a completely new protocol structure. The TLV attribute acts as a mediator that conveys metric type information without disrupting the core IGP protocol operations

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The solution makes the Extended IP Reachability TLV multi-functional by adding the preferred metric type attribute to it. This existing TLV structure, already used for advertising anycast group information, now also carries metric type specifications, eliminating the need for separate protocol structures for metric advertisement

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250088451A1Extended shortest path first computation for anycast prefix segments

Publication Date: 2025.03.13 CIENA CORP

AI summary

Systems and methods for an extended shortest path first computation for anycast prefix segments using a preferred metric-type include receiving an Interior Gateway Protocol (IGP) update with anycast group information therein; creating or updating a record for an anycast group with the anycast group information; computing a route for the anycast group based on a preferred metric associated with the anycast group information; and installing the computed route. The preferred metric can be specifically defined in the anycast group information.