Dynamic SR-TE Policy Computation Across Mixed Network Segments
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Solution Overview
Problem
In computer networks, especially those using segment routing for traffic engineering, there is a challenge in dynamically computing segment routing policies when routers along the path are not enabled for segment routing, leading to failures in establishing end-to-end SR-TE paths.
Innovation Solution
The solution involves generating an SR-TE MPLS OAM traceroute packet that includes a list of SR-enabled routers and a flag to trigger the dynamic creation of a resource reservation LSP through RSVP-enabled devices, allowing the establishment of a segment routed LSP to tunnel through the resource reservation LSP, even when non-SR enabled routers are present in the path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If segment routing policies are dynamically computed in networks with non-SR enabled routers, then SR-TE path establishment fails, but network compatibility is maintained
Solution Approach 1:
The patent introduces border routers as intermediary devices between SR-enabled and non-SR-enabled network segments. These border routers receive SR-TE packets, compute the SR portion of the path to the border router, and then handle the non-SR portion using traditional routing protocols. This intermediary approach allows SR-TE paths to be established reliably while maintaining compatibility with networks containing non-SR enabled routers.
2Adaptability or versatility
If manual configuration of resource reservation LSPs is used, then network compatibility is maintained, but operational complexity increases
Solution Approach 1:
The patent enables border routers to automatically perform the functions that would otherwise require manual configuration. When an SR-TE packet arrives at a border router, the system automatically computes the path, establishes the resource reservation LSP through non-SR enabled routers using RSVP-TE, and configures the necessary forwarding state. This self-service mechanism eliminates manual configuration complexity while maintaining network compatibility.
3Extent of automation
If on-demand RSVP LSP creation is implemented, then dynamic SR-TE policy establishment is enabled, but signaling overhead increases
Solution Approach 1:
The patent implements a caching mechanism that stores computed paths and established LSP information from previous SR-TE operations. When subsequent SR-TE packets arrive for similar destinations or paths, the border router can retrieve pre-computed information from the cache, avoiding the need to generate new RSVP signaling packets. This preliminary action significantly reduces signaling overhead while maintaining dynamic policy establishment capability.
Data Source
AI summary
Techniques are described for dynamically computing a segment routing policy for a segment routing for traffic engineering (SR-TE) path. For example, in a discontinuous SR network in which SR islands (e.g., groups of neighboring routers that are enabled for segment routing) are separated by one or more routers not enabled for segment routing, instead of returning a failure because one or more routers along a path are not enabled for SR, an ingress router may generate an SR-TE operations, administrations, and management (OAM) Multi-Protocol Label Switching (MPLS) traceroute packet send the packet to a first border router of the RSVP-enabled devices along a computed path to trigger the creation of a resource reservation Label Switched Path (LSP) through the RSVP-enabled devices. In this way, segment routed LSP may be established to tunnel through the resource reservation LSP for a SR-TE path used in an SR-TE policy.