Internet-Draft draft-ietf-rift-kv-tie-structure-and-pro July 2024
Head & Przygienda Expires 9 January 2025 [Page]
Workgroup:
RIFT
Internet-Draft:
draft-ietf-rift-kv-tie-structure-and-processing-01
Published:
Intended Status:
Standards Track
Expires:
Authors:
J. Head, Ed.
Juniper Networks
T. Przygienda
Juniper Networks

RIFT Key/Value TIE Structure and Processing

Abstract

The RIFT (Routing in Fat-Trees) protocol allows for key/value pairs to be advertised within Key-Value Topology Information Elements (KV-TIEs). The data contained within these KV-TIEs can be used for any imaginable purpose. This document defines the various Key-Types (i.e. Well-Known, OUI, and Experimental) and a method to structure corresponding values.

Requirements Language

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

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on 9 January 2025.

Table of Contents

1. Introduction

The Routing in Fat-Trees RIFT [RIFT] protocol allows for key/value pairs to be advertised within Key-Value Topology Information Elements (KV-TIEs). There are no restrictions placed on the type of data that is contained in KV-TIEs nor what the data is used for.

For example, it might be beneficial to advertise overlay protocol state from leaf nodes to the Top-of-Fabric (ToF) nodes. This would make it possible to view critical state of a fabric-wide service from a single ToF node rather than retrieving and reconciling the same state from multiple leaf nodes.

2. Key-Value Structure

This section describes the generic Key structure and semantics, Figure 1 further illustrates these components.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Key-Type    |               Key Identifier                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Values (variable)                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: Generic Key-Value Structure

where:

2.1. Key Sub-Type

The Key Sub-Type is an OPTIONAL mechanism to further describe the contained values and their structure. This is illustrated by Figure 2. While the Key Sub-Type is optional, it MUST be used when the Key-Type is either Well-Known or Experimental in order to avoid interoperability issues.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|   Key-Type    |  Key Sub-Type |        Key Identifier         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Values (variable)                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: Generic Key-Value Structure with Key Sub-Type

where:

2.2. Experimental Key-Type

This section reserves a value in the RIFT Key-Type Registry to indicate an Experimental Key-Type.

As shown in Figure 3, the Key-Type will be used to identify the Key-Type as Experimental. The Key Identifier will be used to identify the specific key and describe the structure of the contained values.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       1       |  Key Sub-Type |        Key Identifier         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                 Experimental Values (variable)                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: Experimental Key-Type

2.3. Well-Known Key-Type

This section reserves a value in the RIFT Key-Type Registry to indicate Well-Known Key-Types that all implementations SHOULD support.

As shown in Figure 4, the Key-Type will be used to identify the Key-Type as Well-Known. The Key Identifier will be used to identify the specific key and describe the structure of the contained values.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       2       |  Key Sub-Type |        Key Identifier         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                 Well-Known Values (variable)                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: Well-Known Key-Type

2.4. OUI Key-Type

This section reserves a value in the RIFT Key-Type Registry to indicate an OUI (vendor-specific) Key-Type that any implementation MAY support.

As shown in Figure 5, the Key-Type will be used to identify the Key-Type as OUI. The Key Identifier MUST use the implementing organization's reserved OUI space to indicate the key and value structure.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       3       |              OUI Key Identifier               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|               Vendor Specific Values (variable)               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: OUI Key-Type

3. Design Considerations

While no restrictions are placed on Key-Value data or what it is used for, it is RECOMMENDED that a serialized Thrift [THRIFT] model be used for simpler interoperability. [RIFT-AUTO-EVPN] is an example of this type of implementation.

Key-Value elements SHOULD NOT be used to carry topology information used by RIFT itself to perform distributed computations.

3.1. Tie-Breaking Considerations

In cases where KV-TIEs are flooded from north to south, policies SHOULD be implemented in order to avoid network-wide flooding.

For networks with more than one ToF node, it is RECOMMENDED that those ToF nodes contain identical KV-TIE information when being distributed from north to south. RIFT [RIFT] requires that only one KV-TIE is selected when identical keys are received from multiple northbound neighbors. If this is not considered then the tie-breaking rules may cause a node to select a suboptimal KV-TIE. Consider a case where failure conditions cause the ToF nodes to become split-brained. While the Key-Type and Key Identifier will be identical, the value(s) contained within may differ. The node(s) receiving these differing KV-TIEs will select the one from the ToF node with the highest System ID, potentially leading to unintended effects.

3.1.1. Southbound Key-Value TIE Tie-Break Sub-Type

This Key-Value pair contains information that allows an implementation to test and verify proper tie-breaking behavior for the Southbound Key store.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Well-Known   |   Tie Break   |        Key Identifier         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     (System ID,                                               |
|      Level),                                                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Southbound Tie-Break (Global) Sub-Type

where:

  • System ID:
    A REQUIRED value indicating the node's unique System ID.
    Level:
    A RECOMMENDED value indicating the node's level.

3.2. Key Target

The Key Target is an OPTIONAL value that identifies group(s) of node(s) that are intended to receive a given Key-Value TIE. Key Targets are 64-bits in length with a valid range of 0 - 18446744073709551615 (2^64-1), this will reduce the chances that Key Target values collide.

A value of all 0s represent that every node is intended to receive this Key-Value TIE and MUST NOT be used for any other reason.

A value of all 1s represent that all leaf nodes are intended to receive this Key-Value TIE and MUST NOT be used for any other reason.

Any other value MUST be derived from the following normative algorithm.

/// random seeds used in algorithms to increase entropy
pub const RANDOMSEEDS: [UnsignedSystemID; 3] = [
    67438371571u64,
    37087353685,
    88675895388,
];

/// given a system ID delivers the bits set by the according Bloom Filter in the southbound
/// key value target.
///
/// @note: This is standardized and cannot be changed between releases!
pub (crate) fn target2bits(target: UnsignedSystemID) -> KeyValueTargetType {
    (0 as usize .. 3)
        .map(|s| {
            let rot = (target ^ RANDOMSEEDS[s]).rotate_left(s as _);
            rot.to_ne_bytes().iter().fold(0, |v: u8, nv| v.rotate_right(4) ^ *nv) % 64
        })
        .fold(0, |v, nv| v | v | (1 << nv))
}
Figure 7: Key Target Standard Algorithm

3.2.1. Key Target Processing

Nodes that support the processing of Key Targets MUST only do so on KV-TIEs in the southbound direction. Key Targets MUST NOT be present on KV-TIEs in the northbound direction and are otherwise ignored and logged.

Nodes that do not support the processing of Key Targets MUST continue to send KV-TIEs to all nodes in the appropriate direction. Additionally, Key Targets MUST be preserved when KV-TIEs are re-originated in the southbound direction.

3.2.1.1. Purging/Rollover

There are several reasons a node may select a different KV-TIE. For example, the KV-TIE is considered newer due to the sequence number incrementing, there was a change in the original tie-breaking result between multiple KV-TIEs, or a loss of northbound connectivity to the node that advertised the previously selected KV-TIE.

Consider a case where Leaf-1, Leaf-2, and Leaf-3 are members of a group of nodes represented by Key Target KT1. If Leaf-2 is removed from that group and a newer instance of the KV-TIE needs to be flooded Leaf-2 will have to maintain the older KV-TIE in the LSDB until the lifetime expires. This could lead to suboptimal behavior in the fabric.

If the new KV-TIE being flooded does not include the previous Key Target value, then implementations SHOULD flood the newer instance of the KV-TIE with a very short lifetime to nodes that belonged to the previous Key Target but not the new Key Target. This logic only applies to KV-TIEs being flooded in the southbound direction.

4. IANA Considerations

Per [RFC8126], IANA is requested to create two new registries under the top-level "RIFT" category:

The following sections detail each registry's individual requirements and suggested values.

Experts reviewing requests for new values to either registry MUST consider the items in the Expert Review Guidance (Section 4.3) section.

4.1. RIFT Key-Types

This section requests that IANA create and help govern the following registry:

  • Registry Name:
    RIFT Key-Types
    Registration Procedures:
    Expert Review
    Description:
    Key-Type registry for the RIFT protocol.
    Reference:
    This document.

4.1.1. RIFT Key-Types Requested Entries

This section requests that IANA register the following suggested values to the "RIFT Key-Types" registry.

Table 1
Value Key-Type Description Status/Reference
0 Illegal Not allowed. This document
1 Experimental Indicates that the Key-Type is Experimental. This document.
2 Well-Known Indicates that the Key-Type is Well-Known. This document.
3 OUI Indicates that the Key-Type is OUI (vendor specific). This document.

4.2. RIFT Well-Known Key Sub-Types

This section requests that IANA create and help govern the following registry:

  • Registry Name:
    RIFT Well-Known Key Sub-Types
    Registration Procedures:
    Expert Review
    Description:
    Well-Known Key Sub-Types registry for the RIFT protocol.
    Reference:
    This document.

4.2.1. RIFT Well-Known Key Sub-Types Requested Entries

This section requests that IANA register the following suggested values to the "RIFT Well-Known Key Sub-Types" Registry.

Table 2
Value Key-Identifier Description Status/Reference
0 Illegal Not allowed. This document.
1 MAC/IP Binding To be defined. To be defined.
2 FAM Security Roll-Over Key To be defined. To be defined.
127 Southbound Tie-Break Key Sub-Type Used for Southbound Keystore tie-breaking testing and verification. This document.

4.3. Expert Review Guidance

Experts reviewing requests for values from the "RIFT Key-Types" registry or the "RIFT Well-Known Key-Types" registry are responsible for the following:

  1. Determining the existence of a specification that clearly defines the purpose supporting the request and MUST contain all required fields for given registry.

    The document MUST also be permenent and publically available.

  2. Ensuring that any requests are made available to the RIFT working group for review should the work originate from outside of the RIFT Working Group.

  3. Ensuring that any work produce outside of the IETF does not conflict with any work that is already published or actively pursuing being published.

5. Security Considerations

This document introduces no new security concerns to RIFT or other specifications referenced in this document given that the Key-Value TIEs are already extensively secured by the RIFT [RIFT] protocol specification itself.

6. Acknowledgements

To be provided.

7. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC8126]
Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", , <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[RIFT]
Przygienda, T., Head, J., Sharma, A., Thubert, P., Rijsman, B., and D. Afanasiev, "RIFT: Routing in Fat Trees", Work in Progress draft-ietf-rift-rift-24, , <https://www.ietf.org/archive/id/draft-ietf-rift-rift-24.html>.

8. Informative References

[RIFT-AUTO-EVPN]
Head, J., Przygienda, T., and W. Lin, "RIFT Auto-EVPN", Work in Progress, draft-ietf-rift-auto-evpn-05, , <https://www.ietf.org/archive/id/draft-ietf-rift-auto-evpn-05.html>.
[THRIFT]
Apache Software Foundation, "Thrift Language Implementation and Documentation", <https://github.com/apache/thrift/tree/0.15.0/doc>.

Appendix A. Thrift Models

This section contains the Thrift models that MAY be used to test southbound Key-Value tie-breaking based on System ID. Per the main RIFT [RIFT] specification, all signed values MUST be interpreted as unsigned values.

A.1. southbound_kv.thrift

include "common.thrift"

namespace py southbound_kv
namespace rs models

const i8            GlobalSystemIdentifierKV  = 127

/** simple type to test correct tie-breaking based on system ID */
struct SystemIdentifierKV {
    1:  required   common.SystemIDType         system_id,
    2:  optional   common.LevelType            level,
}

Figure 8: RIFT Common Schema for Southbound Key-Value Tie-Break Key Sub-Type

Authors' Addresses

Jordan Head (editor)
Juniper Networks
1137 Innovation Way
Sunnyvale, CA
United States of America
Tony Przygienda
Juniper Networks
1137 Innovation Way
Sunnyvale, CA
United States of America