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Time-Variant Routing

Document Charter Time-Variant Routing WG (tvr)
Title Time-Variant Routing
Last updated 2024-03-20
State Approved
WG State Active
IESG Responsible AD Gunter Van de Velde
Charter edit AD Gunter Van de Velde
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Existing IETF routing protocols expect to maintain contemporaneous, end-to-end connected paths across a network. Changes to that connectivity, such as the loss of an adjacent peer, need the routing protocols to react to reduce the impact on the network traffic.

However, a growing number of use cases exist where predicted variations (restoration, activation, or loss) to the topology are an expected part of normal network operations. For example, in networks with mobile nodes, such as aerial vehicles and some orbiting spacecraft constellations, links can be lost and re-established, or neighbors may change as a function of their mobility. Similarly, network traffic might be routed based on energy costs or expected user data volumes, which may vary predictably over time in networks prioritizing green computing and energy efficiency. In these cases, the predicted loss and restoration of an adjacency, or formation of an alternate adjacency, should be seen as non-disruptive events. Support for such use cases and expected changes in a routing system is called Time-Variant Routing (TVR).

The Time-Variant Routing Working Group (TVR WG) is chartered to define information and data models that address time-based, scheduled changes to a network. Time-based changes may include changes to links, adjacencies, cost, and - in some cases - traffic volumes. The models are expected to satisfy the non-terrestrial networks' requirements as their main driver. Still, they should be general enough to encompass other types of networks and use cases. They should also be agnostic with respect to other control plane elements.

The WG may also define terminology and concepts where needed, as well as address the impacts of a continually changing topology on the hierarchical structure of the network.

The TVR WG will collaborate with groups working on non-terrestrial networks, including DTN, CCAMP, DETNET, RAW, and DRIP. In addition, the outputs from the WG will be provided to other working groups for consideration, which may use the material to incorporate time-variant attributes and behaviors into individual protocols.

Specifically, the TVR WG will work on these items:

(1) Problem Statement and Use cases

This document (or set of documents) should include a description of the problem statement and related use cases to guide the remaining work. It exists to support the efforts of the Working Group and help newcomers, and it might not be published as an IETF Stream RFC.

(2) Requirements

This document should include definitions, requirements, notes, rationales, and examples.

(3) Information Model

This document (or set of documents) should describe the attributes needed, and the relationship between them, to enable routing and forwarding decisions in the presence of time-variant network parameters.

(4) Data Model

This document (or set of documents) should specify a YANG Data Model (or multiple modules), based on the Information Model, for configuration and monitoring.

(5) Applicability Statement

This document should provide an applicability statement on how the information and data models may be used, along with required ancillary IETF technology, to solve the use cases and requirements.

(6) Implementation and Operational Considerations

This document should provide advice and guidance to implementors and operators.