Using IS-IS To Advertise Power Group Membership

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Table of Contents

1. Introduction

This document introduces Power Groups. A Power Group is a hierarchical abstraction of power consumed by hardware components. In IS-IS, interfaces can reference the Power Group to which they belong. Therefore, Power Groups provide a method of organizing interfaces into groups by power characteristics.¶

The TE path placement algorithm can use Power Group membership information to implement TE policy. Power Group information is particularly useful when implementing TE policies that support power-savings and sustainability.¶

2. Conventions and Definitions

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 BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

3. Example Architecture

                           *------------*
                           |     LC1    |
                           |  100 watts |
                           *------------*
                               /    \
                  -------------      -------------
                  |                               |
           *------------*                  *------------*
           |    FE1     |                  |    FE2     |
           |  300 watts |                  |  300 watts |
           *------------*                  *------------*
          /              \                /              \
         /                \              /                \
    *----------*    *----------*    *----------*    *----------*
    | INTCOMP1 |    | INTCOMP2 |    | INTCOMP3 |    | INTCOMP4 |
    | 15 watts |    | 20 watts |    | 15 watts |    | 20 watts |
    | 400 Gbps |    | 800 Gbps |    | 400 Gbps |    | 800 Gbps |
    | (optics  |    | (no      |    | (optics  |    | (no      |
    | included)|    |  optics) |    | included)|    |  optics) |
    *----------*    *----------*    *----------*    *----------*
     /       \            |            /     \             |
    /         \           |           /       \            |
 INT1        INT2       INT3      INT4       INT5        INT6
 0 watts     0 watts    5 watts   0 watts    0 watts     5 watts
 No optics   No optics  Optics    No optics  No optics   Optics

Line Card 1 (LC1) consumes 100 watts

Figure 1 depicts a line card (LC1). LC1 contains two forwarding engines (FE1 and FE2) and four interface complexes (INTCOMP1 through INTCOMP4). INTCOMP1 supports in two interfaces (INT1 and INT2). Likewise, INTCOMP3 supports in two interfaces (INT4 and INT5). INTCOMP2 and INTCOMP4 support one interface each (INT3 and INT6).¶

An interface complex includes PHY, MAC, encryption, gearbox, and other related circuitry. INTCOMP1 and INTCOMP3 also contain optics. INTCOMP2 and INTCOMP4 do not contain optics. Therefore, the interfaces that they support have their own optics.¶

INTCOMP1 and INTCOMP3 provide 400 Gbps of forwarding capacity each, while INCOMP2 and INTCOMP4 provide 800 Gbps of forwarding capacity each.¶

Each hardware component consumes power. LC1 consumes 100 watts while FE1 and FE2 consume 300 watts each. INTCOMP1 and INTCOMP3 consume 15 watts each, while INTCOMP2 and INTCOMP4 consume 20 watts each. INT3 and INT6 contain optics that consume 5 watts each. INT1, INT2, INT4 and INT5 do not do separate optics. Therefore, they do not consume power beyond what is consumed by the complex.¶

INT1 and INT2 depend upon INTCOMP1. If INTCOMP1 fails, so do INT1 and INT2. Likewise, INT3 depends upon INTCOMP2. If INTCOMP2 fails, so does INT3.¶

INTCOMP1 and INTCOMP2 depend on FE1. If FE1 fails, so do INTCOMP1, INTCOMP2, INT1, INT2, and INT3. Likewise, INTCOMP3 and INTCOMP4 depend on FE2. If FE2 fails, so do INTCOMP3, INTCOMP4, INT4, INT5, and INT6.¶

FE1 and FE2 depend on LC1. If LC1 fails, so do all of the forwarding engines, interface complexes, and interfaces in the diagram.¶

4. Power Groups

A Power Group is a hierarchical abstraction of power consumed by hardware components. Each Power Group, except for the one at the top of the hierarchy, has exactly one parent. The Power Group at the top of the hierarchy does not have a parent. Many Power Groups can have the same parent.¶

Each Power Group has one or more components and each component consumes power. The power consumed by a Power Group is equal to the sum of the power consumed by each of its components. The power consumed by a Power Group does not include the power consumed by its ancestors or by its children.¶

The parent-child relationship reflects dependency. One Power Group is the child of another if any one of the child components depends upon any one of the parent components.¶

A network device's power consumption characteristics can be described by any number of equivalent Power Group hierarchies. The paragraphs below demonstrate how two equivalent Power Group hierarchies can describe the power consumption characteristics of the line card in Figure 1.¶

Table 1 describes the power consumption characteristics of the line card in Figure 1 using a granular Power Group hierarchy. We call it granular because each Power Group contains only one component. The power consumed by each Power Group is equal to the power consumed by its component.¶

In Table 1, Power Group 7 is the child of Power Group 3 because INTCOMP4 depends upon FE2. Likewise, Power Group 3 is the child of Power Group 1 because FE2 depends on LC1. Furthermore, Power Group 8 is the child of Power Group 5 because INT3 depends upon INCOMP2. Likewise, Power Group 9 is the child of Power Group 7 because INT6 depends on INTCOMP4.¶

Table 2 describes the power consumption characteristics of the line card in Figure 1 using a less granular Power Group hierarchy. We call it less granular because Power Group 1 contains three components (LC1, FE1 and FE2). Its power consumption is equal to the sum of the power consumed by LC1, FE1 and FE2 (i.e., 700 watts).¶

Power Group 2 and Power Group 3 are children of Power Group 1 because INTCOMP1 and INTCOMP2 depend on FE1. Likewise, Power Group 4 and Power Group 5 are children of Power Group 1 because INTCOMP3 and INTCOMP4 depend on FE2. Finally, Power Group 5 and Power Group 7 are children of Power Group 1 because INT3 and INT6 depend on INCOMP2 and INCOMP4..¶

Section 6 describes how a network device's power-save capability determines which of the equivalent Power Group hierarchies it should advertise.¶

Section 7.2.2 describes how IS-IS advertises Power Group information.¶

5. Interfaces and Power Groups

An interface is not part of a Power Group, even if it contains optics and consumes power. However, an interface can reference a Power Group. When it references a Power Group, it MUST reference the Power Group that contains the interface complex that supports it. See Section 7.2.1.¶

Therefore, Power Groups can be used to associate interfaces that depend on a common set of hardware components and have common power consumption characteristics.¶

A Link Aggregation Group (LAG) interface requires support from multiple interface complexes. Therefore a LAG interface references every Power Group that contains an interface complex that supports it.¶

Section 7.2.2 describes how an interface can advertise the power that it consumes.¶

6. Power-Save Capability and Power Group Hierarchies

A network device SHOULD advertise the least granular Power Group hierarchy that can exercise its complete power-savings capability.¶

Assume that a network contains line cards that are power-save capable. Those line cards contain forwarding engines and interface complexes that are also power-save capable. This means that the line cards, forwarding engines and interface complexes can be powered on and off independently of the chassis.¶

In order to exercise its complete power savings capability, information regarding line card, forwarding engine and interface complex dependencies is required. Therefore, the line card must advertise the granular Power Group hierarchy in Table 1.¶

Now assume that another network contains line cards that are power-save capable. Those line cards contain interface complexes that are also power-save capable. However, the forwarding engines are not power-save capable.¶

In order to exercise its complete power savings capability,
information regarding line card, and interface complex dependencies is required. However, information regarding forwarding engine dependencies is not required. Therefore, the line card could advertise either the granular Power Group hierarchy in Table 1 or the less granular Power Group hierarchy in Table 2.¶

7. Link State Database Elements

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Type      |     Length    |      Power Group Identifier
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  Power Group Identifier (cont.)|            Power
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Power (cont.)        |         Parent Identifier
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Parent Identifier (cont.)   |C|  Reserved   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Type      |     Length    |      Power Group Identifier
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  Power Group Identifier (cont.)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Type      |     Length    |            Power
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Power (cont.)        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Type      |     Length    |      Sleeping Bandwidth
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  Sleeping Bandwidth            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

8. Security Considerations

TBD¶

9. IANA Considerations

IANA is requested to add the following entry to the IS-IS Top-Level TLV Codepoints registry (https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-codepoints.xhtml#tlv-codepoints):¶

IANA is also requested to add the following entry to the IS-IS Sub-TLVs for TLVs Advertising Neighbor Information registry (https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-codepoints.xhtml#isis-tlv-codepoints-advertising-neighbor-information):¶

IANA is also requested to add the following entry to the IS-IS Neighbor Link-Attribute Bit Values registry (https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-codepoints.xhtml#isis-tlv-codepoints-19of22):¶

10. Acknowledgements

TBD¶

11. References

Authors' Addresses