US-20260128979-A1 - Flexible and Scalable Automatic Next-Hop Resolution in Traffic Engineering Networks

US20260128979A1US 20260128979 A1US20260128979 A1US 20260128979A1US-20260128979-A1

Abstract

Systems and methods are provided for flexible and scalable Automatic Next-Hop Resolution (ANR) in Traffic Engineering (TE) networks using color-templates. A Customer Edge (CE) router associates a color with an advertised prefix and communicates the colored prefix to a node in a service provider network, such as a Provider Edge (PE) router or Border Router (BR). Upon receipt of the colored prefix, the node requests a controller to generate a Segment Routing (SR) policy or tunnel based on a color-template corresponding to the color. The controller maintains the color-templates, computes paths subject to template-defined parameters and constraints, and returns SR policy or tunnel information for installation at the requesting node. When the CE changes the color associated with the prefix, the node triggers generation of a new policy or tunnel based on the updated color-template. Default templates and template update handling are also supported, reducing provider-side configuration and improving operational scalability.

Inventors

Amila Pradeep Kumara Tharaperiya Gamage
Muthurajah Sivabalan

Assignees

CIENA CORPORATION

Dates

Publication Date: 20260507
Application Date: 20260105

Claims (20)

1 . A non-transitory computer-readable medium comprising instructions that, when executed at a controller, cause one or more processors to perform steps of: responsive to a Customer Edge Router advertising a prefix with an associated color to a node in a Service Provider Network, receiving a request to generate one of a Segment Routing policy and a tunnel based on a color-template for the associated color; providing the one of the Segment Routing policy and tunnel information for the tunnel to the node for installation thereon, wherein the node is one of a Provider Edge Router and a Border Router; and responsive to changing the prefix to another associated color at the Customer Edge Router and advertising to the node, receiving another request from the node to generate one of a Segment Routing policy and a tunnel based on another color-template for the another associated color.
2 . The non-transitory computer-readable medium of claim 1 , wherein the tunnel is based on Resource Reservation Protocol-Traffic Engineering (RSVP-TE).
3 . The non-transitory computer-readable medium of claim 1 , wherein the request is via a Type-Length-Value (TLV).
4 . The non-transitory computer-readable medium of claim 1 , wherein the steps further include responsive to the color-template not being configured or having been previously deleted, using a default color-template.
5 . The non-transitory computer-readable medium of claim 1 , wherein the steps further include responsive to the color-template being modified, pushing the modified one of the Segment Routing policy and the tunnel information to the node for installation thereon.
6 . The non-transitory computer-readable medium of claim 1 , wherein the color-template includes a plurality of candidate paths having different preference values, and wherein the controller generates the one of the Segment Routing policy and the tunnel by selecting at least one of the candidate paths based on the preference values.
7 . The non-transitory computer-readable medium of claim 1 , wherein the color-template includes at least one intent-template specifying (i) a path-metric-type and (ii) one or more administrative-group constraints, and wherein the controller computes a traffic-engineering path for the one of the Segment Routing policy and the tunnel using the path-metric-type and the one or more administrative-group constraints.
8 . The non-transitory computer-readable medium of claim 7 , wherein the one or more administrative-group constraints comprise at least one of (i) an exclude-all constraint that prevents use of links marked with a first administrative-group label and (ii) an include-all constraint that restricts the traffic-engineering path to links marked with a second administrative-group label.
9 . The non-transitory computer-readable medium of claim 1 , wherein the request received at the controller includes a source address of the node, a destination address for the one of the Segment Routing policy and the tunnel, and the associated color, and wherein the controller generates the one of the Segment Routing policy and the tunnel based on the source address, the destination address, and the associated color.
10 . The non-transitory computer-readable medium of claim 1 , wherein the Customer Edge Router advertises the prefix with the associated color to the node using at least one of an Interior Gateway Protocol and Border Gateway Protocol, and wherein the node advertises the prefix with the associated color to one or more additional nodes in the Service Provider Network using Border Gateway Protocol.
11 . A method comprising steps of: responsive to a Customer Edge Router advertising a prefix with an associated color to a node in a Service Provider Network, receiving a request to generate one of a Segment Routing policy and a tunnel based on a color-template for the associated color; providing the one of the Segment Routing policy and tunnel information for the tunnel to the node for installation thereon, wherein the node is one of a Provider Edge Router and a Border Router; and responsive to changing the prefix to another associated color at the Customer Edge Router and advertising to the node, receiving another request from the node to generate one of a Segment Routing policy and a tunnel based on another color-template for the another associated color.
12 . The method of claim 11 , wherein the tunnel is based on Resource Reservation Protocol-Traffic Engineering (RSVP-TE).
13 . The method of claim 11 , wherein the request is via a Type-Length-Value (TLV).
14 . The method of claim 11 , wherein the steps further include responsive to the color-template not being configured or having been previously deleted, using a default color-template.
15 . The method of claim 11 , wherein the steps further include responsive to the color-template being modified, pushing the modified one of the Segment Routing policy and the tunnel information to the node for installation thereon.
16 . The method of claim 11 , wherein the color-template includes a plurality of candidate paths having different preference values, and wherein the controller generates the one of the Segment Routing policy and the tunnel by selecting at least one of the candidate paths based on the preference values.
17 . The method of claim 11 , wherein the color-template includes at least one intent-template specifying (i) a path-metric-type and (ii) one or more administrative-group constraints, and wherein the controller computes a traffic-engineering path for the one of the Segment Routing policy and the tunnel using the path-metric-type and the one or more administrative-group constraints.
18 . The method of claim 17 , wherein the one or more administrative-group constraints comprise at least one of (i) an exclude-all constraint that prevents use of links marked with a first administrative-group label and (ii) an include-all constraint that restricts the traffic-engineering path to links marked with a second administrative-group label.
19 . The method of claim 11 , wherein the request received at the controller includes a source address of the node, a destination address for the one of the Segment Routing policy and the tunnel, and the associated color, and wherein the controller generates the one of the Segment Routing policy and the tunnel based on the source address, the destination address, and the associated color.
20 . The method of claim 11 , wherein the Customer Edge Router advertises the prefix with the associated color to the node using at least one of an Interior Gateway Protocol and Border Gateway Protocol, and wherein the node advertises the prefix with the associated color to one or more additional nodes in the Service Provider Network using Border Gateway Protocol.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) The present application is a continuation of U.S. patent application Ser. No. 18/594,797, filed Mar. 4, 2024, the contents of which are incorporated by reference in their entirety. FIELD OF THE DISCLOSURE The present disclosure relates generally to networking and computing. More particularly, the present disclosure relates to systems and methods for flexible and scalable Automatic Next-Hop Resolution (ANR) in Traffic Engineering (TE) networks. BACKGROUND OF THE DISCLOSURE Automatic Next-Hop Resolution (ANR) is a network feature designed to simplify and automate the process of determining the next-hop Internet Protocol (IP) address for a given destination, particularly in complex network scenarios such as those involving Virtual Private Networks (VPNs) or dynamically changing network topologies. This feature is particularly relevant in the context of Multiprotocol Label Switching (MPLS) networks and IP routing, where manual configuration of next-hop addresses for each possible destination can be cumbersome and prone to errors, especially in large-scale or rapidly evolving networks. ANR supports (1) scalability, reducing the administrative overhead associated with managing large or complex networks by automating the resolution of next-hop addresses; (2) flexibility, enhancing the network's ability to adapt to changes, such as route updates, topology changes, or network expansions, without the need for manual reconfiguration; and (3) efficiency, improving the overall efficiency of the routing process by ensuring that the most current and optimal next-hop routes are used, which can improve performance and reduce latency. ANR does not adhere to a single, specific standard but a concept that integrates with and relies on the broader standards and mechanisms of various routing and signaling protocols that facilitate dynamic routing and path determination in complex network architectures. Segment Routing (SR) simplifies the forwarding of packets within a network by encoding the path that a packet takes through the network as a list of segments, which are instructions on how to forward the packet. Segment Routing is described, e.g., in RFC 8402, “Segment Routing Architecture,” Internet Engineering Task Force (IETF), July 2018, the contents of which are incorporated herein by reference. Segment Routing inherently supports automatic next-hop determination within its architecture. Segment Routing Traffic Engineering (SR-TE) includes further extensions to support traffic engineering and advanced path selection. This concept also ties into the broader use in Software-Defined Networking (SDN) environments. In the context of SR-TE, a “color” is used as an abstract representation to match traffic flows to specific policies or paths through the network. These policies are defined by administrators to meet certain criteria like bandwidth, latency, or administrative preference. The concept of “color” allows for the simplification of traffic engineering policies by abstracting the details of the path characteristics into a color identifier. This identifier is then used to automatically resolve the next-hop or the specific path (list of segments) that the traffic should take to adhere to the defined policy. ANR with color-templates allows the automatically determination of the appropriate next-hop or path for traffic based on the color-template associated with the color. This is facilitated by control-plane protocols and software-defined networking controllers that compute optimal paths based on the network's current state and the policies defined in color-templates by network administrators. BRIEF SUMMARY OF THE DISCLOSURE The present disclosure relates to systems and methods for flexible and scalable Automatic Next-Hop Resolution (ANR) in Traffic Engineering (TE) networks, specifically with color-templates. ANR with color-templates requires a significant amount of configuration at Provider Edges (PEs) and Border Routers (BRs). Moreover, whenever end customers change their networks, service providers may also have to make changes to the service provider network. This leads to less flexibility and higher operational costs. The proposed mechanisms herein overcome these shortcomings. Specifically, the proposed mechanisms allow associating colors to prefixes at Customer Edges (CE). This allows customers to make any change to their network and assign/re-assign color values to prefixes as they wish, without requiring any changes to the service provider network. The proposed mechanisms also allow maintaining color-templates only at a controller, letting PEs/BRs request the controller to generate SR policies on demand. This reduces required configurations and scales well. In various embodiments, the present disclosure includes a method with steps, a controller or other processing device or service configured to implement the steps, and a non-transitory computer-readable medium storing instructi