Consideration for TVR (Time-Variant Routing) Requirements

Existing routing protocols are expected to maintain end-to-end connected paths across a network. There are cases where the end-to-end path can not be maintained, such as the loss of an adjacent peer. In these cases, corrections could be applied prior to the resumption of data transmission. Corrections may include attempting to re-establish lost adjacencies and recalculating or rediscovering a functional topology. There were three use cases had been defined in the TVR's use case document . The first is resource preservation; one example of a network where nodes must perform resource preservation is an energy-harvesting, wireless sensor network. The second is operating efficiency; one example of a network where nodes might seek to optimize operating cost is a set of nodes operating over cellular connections that charge both On-Peak and Off-Peak data rates. The third is mobile devices; some examples of this use case are vehicle-to-vehicle communications, Low Earth Orbit (LEO) networked constellation (LEO-NC), and so on. Recently, the document gave some TVR's requirements about general temporality , and this document makes some supplements for TVR's requirements.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Considering requirements for TVR (Time-Variant Routing) in the following aspects

In Time-Variant Routing, scheduling of the system are as expected. In practical situations, however, the attributes of nodes can be converted back and forth between Time-Variant and Non-Time-Variant nodes. For example, a mobile phone can be considered a Non-Time-Variant node in the network when charging. After unplugging the power cord, it can be considered a Time-Variant-Node because it starts to be powered by batteries. o MUST support the identification and advertisement of node attribute changes. Besides, If there are abnormal changes in the system, it is necessary to advertise them through the existing routing protocols in time to achieve the stability of Time-Variant Routing and avoid redundant advertisements. For example, a node in the system is suddenly damaged due to external factors. Therefore, o Should provide a advertisement methodology for responding to abnormal changes in the system.

Agent nodes can help to improve the efficiency of the network. There are some nodes in the network that do not have routing functions. When their attributes change, they are unable to notify other nodes in the network. Agent nodes can help nodes without routing functions to advertise information, thus improving the efficiency of the network. Therefore, o MUST support agent nodes to help non-routing nodes implement information advertisement.

The node attributes of the network may change as described in 3.1. If the system cannot timely identify and classify in a processing manner after the node attributes change, it will lead to suboptimal routing decisions. Therefore, o MUST provide a discovery and resolving methodology for the identification and classification of node attributes.

The system's schedule may change, requiring of to be reconfigured instead it being set once and not being able to be modified. Additionally, time-variant intervals in the system may also vary. Therefore, o MUST support system schedule changes. o MUST support time interval changes.

The accuracy of the time cannot be too large or too small; otherwise, convergence may not be possible. Therefore, o MUST support appropriate time accuracy.

This document makes some supplements to TVR's requirements.

TBD.