SR Policy Path Computation for Incremental BGP-LU Elimination
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Solution Overview
Problem
The existing Border Gateway Protocol - Labeled Unicast (BGP-LU) is becoming an unwanted overhead as networks transition towards Segment Routing (SR) for Traffic Engineering (TE) due to scalability issues and the increasing demand for Service Layer Agreements (SLA) guarantees, necessitating a method to incrementally eliminate BGP-LU while maintaining end-to-end TE support.
Innovation Solution
Utilizing a Path Computation Element (PCE) to learn destination prefixes and BGP-LU labels from next-hop-self nodes, compute Segment Identifier (SID) lists, and incorporate Extended Accumulated Interior Gateway Protocol (AIGP) Type Length Values (TLVs) to form complete SID lists, enabling incremental displacement of BGP-LU with Segment Routing policies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BGP-LU is used to connect different MPLS domains, then network connectivity between domains is maintained, but network complexity and overhead increase
Solution Approach 1:
The patent extracts and removes BGP-LU protocol from the network architecture by implementing SR policies that compute end-to-end paths through multiple MPLS domains. The PCE computes Segment Identifier (SID) lists that traverse domain boundaries without requiring BGP-LU label distribution, thereby eliminating the unwanted protocol overhead while maintaining domain connectivity.
Solution Approach 2:
The patent introduces SR policies as an intermediary mechanism between different MPLS domains. Instead of using BGP-LU for inter-domain connectivity, the SR policy framework with PCE-computed SID lists acts as a mediator that establishes end-to-end paths across domain boundaries, simplifying the connectivity mechanism while maintaining reliability.
2Adaptability or versatility
If RSVP-TE is used for Traffic Engineering, then fine-grained TE control is achieved, but scalability deteriorates in large domains
Solution Approach 1:
The patent replaces the RSVP-TE signaling mechanism with SR policy-based path computation. Instead of using RSVP-TE's complex reservation and signaling protocols for TE, the system uses PCE to compute SID lists that encode TE constraints directly in the segment routing headers, eliminating per-flow state requirements and improving scalability while maintaining fine-grained TE control.
3Productivity
If LDP is used for label distribution, then label switching is enabled, but Traffic Engineering capability is lost
Solution Approach 1:
The patent merges label distribution functionality with Traffic Engineering capabilities by using SR policies. The SR policy framework combines the efficient label switching of LDP with TE constraints, where the PCE computes SID lists that encode both routing and TE requirements, eliminating the need for separate LDP and TE mechanisms.
Data Source
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AI summary
Systems and methods for incrementally eliminating Border Gateway Protocol - Labeled Unicast (BGP-LU) in a multi-region network (10) include receiving BGP-LU updates from one or more Area Border Router (ABR) nodes (ABR1, ABR2) in a multi-region network (10) with the ABR nodes (ABR1, ABR2) between two areas (12, 14) including a first area (12) utilizing Segment Routing without utilizing BGP-LU and a second area (14) utilizing BGP-LU; and, responsive to a request from a first node in the first area (12) to reach a second node in the second area (14), providing a Segment Identifier (SID) list to the first node where the SID list is determined based on the Segment Routing in the first area (12) and the BGP-LU updates from the second area (14).