ISIS Route Selection Using External Metric Tie-Breaker
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Solution Overview
Problem
Conventional mechanisms for route selection in ISIS routing protocols rely heavily on internal costs, requiring cumbersome configuration of route policies and prior knowledge of router addresses, making it difficult to use external metrics as a primary tie-breaker.
Innovation Solution
Utilization of ISIS Type Length Variables (TLVs) and sub-TLVs to advertise routes with external metric information, allowing for dynamic selection based on external costs, eliminating the need for extensive router configuration and prior knowledge of router addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If route-policies and metric manipulations are used in ISIS to select routes based on external cost, then route selection can be controlled, but configuration complexity increases and requires prior knowledge of router addresses
Solution Approach 1:
The patent introduces an intermediary mechanism (route selector component) that mediates between the routing information base and the forwarding plane. This intermediary automatically selects routes based on external cost metrics without requiring manual route-policy configuration, thereby reducing configuration complexity while maintaining adaptability in route selection
Solution Approach 2:
The routing system performs self-service by automatically calculating and selecting routes based on external cost metrics. The route selector component autonomously evaluates available routes and selects the optimal path without requiring external configuration or prior knowledge of router addresses, eliminating the need for complex manual route-policy setup
2Adaptability or versatility
If route-policies are configured on all receiving routers, then route selection based on external cost is achieved, but the number of configuration steps and required information increases
Solution Approach 1:
The patent implements a universal route selector component that can be deployed in ISIS routers to provide external cost-based route selection functionality. This multi-functional component handles route selection across different scenarios and router types, eliminating the need for separate route-policy configurations on each receiving router and significantly reducing overall configuration effort
3Extent of automation
If internal cost is used as the primary tie-breaker in ISIS, then route selection is automatic, but external metrics cannot be prioritized for consistent primary/backup destination behaviors
Solution Approach 1:
The patent implements a dynamic route selection mechanism where the tie-breaker criterion can adapt based on the presence of external cost metrics. The route selector component dynamically adjusts its selection criteria: when external cost information is available, it prioritizes external metrics for consistent primary/backup destination behavior; when external cost is not available, it falls back to internal cost-based selection, thereby maintaining both automation and adaptability
Data Source
AI summary
A method, apparatus and computer program product for providing the use of an external metric as the primary tie-breaker in ISIS route selections is presented. A set of routes are identified that are to be advertised by the router as external routes within a network. The routes are advertised by the router using a Type Length Variable (TLV), wherein the TLV contains metric information to be used as a first tiebreaker when selecting routes. The network is running an Intermediate System To Intermediate System (ISIS) protocol. The TLV includes a 32-bit or a 64-bit administrative tag sub-TLV, the TLV comprising TLV#135, TLV#235, TLV#236, and TLV#237.