OSPF Sub-TLV for SR-MPLS Path Stitching
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Solution Overview
Problem
Current technologies lack a definitive mechanism for flexible path stitching and selection between Segment Routing (SR) and Multiprotocol Label Switching (MPLS) networks, particularly when border nodes have clients other than Label Distribution Protocol (LDP), and there is no way to indicate path preference, leading to interoperability issues and inability to maintain Service Level Agreements (SLAs).
Innovation Solution
The introduction of a new sub-Type-Length-Value (TLV) element within Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS) messages allows operators to specify path preferences, enabling flexible path stitching and selection between SR and MPLS networks by identifying preferred path types such as RSVP, static MPLS, or labeled BGP paths, thereby enhancing interoperability and maintaining SLA guarantees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mapping server is used to interoperate SR and LDP domains, then interoperability between SR and MPLS networks is achieved, but there is no mechanism to indicate path preference leading to inability to maintain SLAs
Solution Approach 1:
The patent introduces a mapping server as an intermediary component that sits between the SR domain and MPLS domain. The mapping server receives path preference information from the SR domain through extended IGP messages and translates/adapts it into appropriate MPLS path selections. This intermediary enables SLA guarantee by mediating the path selection process based on advertised preferences without requiring direct integration between SR and MPLS control planes.
Solution Approach 2:
The patent extends existing IGP message parameters by introducing new sub-TLV elements that carry path preference information. These parameter extensions allow the network to encode specific path requirements (such as bandwidth, delay, or preferred path type) within standard IGP advertisement messages. The mapping server interprets these extended parameters to make informed path selection decisions, thereby maintaining SLAs through parameter-driven path optimization.
2Adaptability or versatility
If existing MPLS network infrastructure is used, then network stability is maintained, but flexible path stitching and selection between SR and MPLS networks is not possible
Solution Approach 1:
The mapping server is designed as a universal component that can handle multiple path types (RSVP, static MPLS, labeled BGP) and multiple path preference indications within a single platform. It provides multi-functional capability to stitch SR paths to various MPLS path types based on advertised preferences, thereby enabling flexible path stitching without requiring separate specialized mechanisms for each path type, reducing overall system complexity.
Solution Approach 2:
The system enables self-service path stitching by allowing SR-capable routers to autonomously advertise their path preferences through extended IGP messages. The mapping server automatically processes these advertisements and configures appropriate MPLS paths without manual intervention. This self-configuring mechanism reduces operational complexity while enabling flexible path stitching between SR and existing MPLS infrastructure.
3Ease of operation
If path preference indication is added to IGP messages, then operators can specify preferred path types, but message complexity increases
Solution Approach 1:
The patent segments path preference information into hierarchical sub-TLV structures within IGP messages. Instead of adding monolithic complex fields, the preference information is divided into modular sub-components (such as path type preferences, metric preferences, and specific path identifiers) that can be independently processed. This segmentation allows operators to specify path preferences in a structured manner while keeping message processing manageable through hierarchical parsing at the mapping server.
Data Source
AI summary
A router operates in both a Segment Routing (SR) network portion and a Multiprotocol Label Switching (MPLS) network portion of a network that utilizes Open Shortest Path First (OSPF). The router receives an OSPF advertisement message originated by a mapping server that includes a sub-Type-length-value (sub-TLV) element that identifies a preferred type of path across the MPLS network portion for an identifiable set of traffic that is to be received by the router from the SR network portion. The router identifies, based at least in part upon the sub-TLV element, one path of a plurality of available paths across the MPLS network portion for the identifiable set of traffic, and configures its forwarding plane to utilize the identified one path accordingly for the identifiable set of traffic. The OSPF advertisement message can be an OSPF LSA, and can carry an Extended Prefix Range TLV including the sub-TLV element.