A YANG model for Power Management

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Table of Contents

1. Introduction

Network sustainability is a key issue facing the industry. Networks consume significant amounts of power at a time when the cost of power is rising and sensitivity about sustainability is very high. As an industry, we need to find ways to optimize the power efficiency of our networks both at a micro and macro level. We have observed that traffic levels fluctuate and when traffic ebbs there is much more capacity than is needed. Powering off portions of network elements could save a significant amount of power, but to scale and be practical, this must be automated.¶

The natural mechanism for enabling automation would be a Yet Another Next Generation (YANG) interface, so this document proposes a YANG model for power management.¶

[RFC8348] already provides a model for server hardware management, but does not naturally extend to routers and other network elements. That gap is currently being addressed by [I-D.ietf-ivy-network-inventory-yang]. This document extends the work presented there to include power management. Specifically, this document augments the 'component' object found at /ietf-network-inventory/network-elements/network-element/components/component.¶

This initial draft only provides a tree representation. When there is rough consensus on the tree represetnation, the details of the model will be fleshed out.¶

2. Power Management Elements

The models mentioned above already model a router or network element as a set of components. The details of those components are left to the specific implementation and can be at any level of specificity. Thanks to this flexibility, it is necessary and sufficient that we characterize power management relative to components.¶

The elements defined below allow management entities to understand how much power each component is using and whether the component can be placed into a 'power-save' mode where it would consume less power. Another element allows the management plane to put the component into power-save mode.¶

        Name: used-power
        Node Type: leaf
        Data Type: uint32
        Description: Power drawn by the component, in watts.

        Name: total-used-power
        Node Type: leaf
        Data Type: uint32
        Description: Power drawn by the component and its
          subcomponents, in watts.

        Name: power-save-capable
        Node Type: leaf
        Data Type: boolean
        Description: True if the component can be put into power-save
          mode.

        Name: power-save
        Node Type: leaf
        Data Type: Boolean
        Access: Read/write
        Description: True if the component is in power-save mode.

        Name: automatic-power-saving
        Node Type: leaf
        Data Type: Boolean
        Access: Read/write
        Description: True if the component is regulating its own
          power.

3. Functional Dependencies

Most inventory models have a hierarchy of components. This hierarchy reflects the physical structure of the system (e.g., a line card can physically contain a port).¶

With regard to physical containment, components maintain a one-to-many relationship. That is, Component A can contain many other components, including Component B. However, component B can be contain by only one component (i.e., Component A.)¶

However, legacy inventory models do not reflect functional dependencies. Specifically, they do not indicate which components obtain services from, and therefore depend, components other than their container. Because funtional dependencies are relavant to power management, they are included in the proposed model.¶

With regard to functional dependencies, components maintain a many-to-many relationship. That is, a component can reuire on many components and be required by many other components.¶

Functional dependencies may be updated dynamically.¶

        Name: required-components
        Node Type: list
        Description: A list of other components that are required for
          this component to operate.

        Name: dependent-components
        Node Type: list
        Description: A list of other components that are used by this
          component.

4. Tree Representation

 +--rw component* [component-id]
    +--rw component-id               string
    +--ro used-power?                uint32
    +--ro power-save-capable?        boolean
    +--rw power-save?                boolean
    +--ro required-components*       -> ../../component/component-id
    +--ro dependent-components*      -> ../../component/component-id

5. Traffic Planning

Some systems have the capability of automatically managing their power consumption if they have an understanding of the expected traffic loads. To provide this, we provide the expected input and output bandwidth for each interface and augment '/interfaces/interface' [RFC8343] with the following:¶

        Name: expected-input-bandwidth
        Node Type: leaf
        Data Type: yang:gauge64
        Default: 0
        Access: Read/write
        Description: The expected input bandwidth of the interface,
          in Mbps. A value of zero (0) indicates full bandwidth.

        Name: expected-output-bandwidth
        Node Type: leaf
        Data Type: yang:gauge64
        Default: 0
        Access: Read/write
        Description: The expected output bandwidth of the interface,
          in Mbps. A value of zero (0) indicates full bandwidth.

 +--rw interface* [name]
    +--rw expected-input-bandwidth?     yang:gauge64
    +--rw expected-output-bandwidth?    yang:gauge64

6. Security Considerations

YANG provides information about and configuration capabilities to the network management plane. Other mechanisms already exist that help secure these interactions. This document extends the scope of what can be controlled by the management plane, but creates no new access paths.¶

7. IANA Considerations

This document makes no requests for IANA.¶

Authors' Addresses