| Internet-Draft | draft-ietf-rift-kv-tie-structure-and-pro | December 2025 |
| Head & Przygienda | Expires 12 June 2026 | [Page] |
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. It also defines a Well-Known Key Sub-Type used for testing tie-breaking behavior.¶
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.¶
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Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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The Routing in Fat Trees [RFC9692] 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.¶
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) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:¶
A 1-byte value that identifies the Key-Type. It MUST be a reserved value from the RIFT Key-Type Registry that is defined later in this document.¶
The range of valid values is 1 - 255 (2^8-1).¶
0 is an illegal value and MUST NOT be allocated to or used by any implementation. KV TIEs received with this value and MUST be discarded and logged on receipt.¶
A 3-byte value that identifies the specific key and describes and the semantics of any contained values. It SHOULD be unique within the context of the given Key-Type.¶
The range of valid values is 1 - 16777215 (2^24-1).¶
0 is an illegal value and MUST NOT be allocated to or used by any implementation. KV TIEs received with this value and MUST be discarded and logged on receipt.¶
The Key Sub-Type is a mechanism to further describe the key's semantics. This is illustrated by Figure 2. The Key Sub-Type MUST be used when the Key-Type is either Well-Known or Experimental in order to avoid interoperability issues, but is OPTIONAL for other Key-Types.¶
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) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:¶
A 1-byte value that identifies the Key Sub-Type which describes the key and its semantics.¶
The range of valid values is 1 - 255 (2^8-1).¶
0 is an illegal value and MUST NOT be allocated to or used by any implementation. KV TIEs received with this value and MUST be discarded and logged on receipt.¶
If the Key Sub-Type is used, it inherently reduces the Key Identifier space from 3-bytes to 2-bytes. The Key Identifier SHOULD be unique within the context of the given Key Sub-Type. The Key Identifier is otherwise unchanged.¶
The range of valid values is now 1 - 65535 (2^16-1).¶
0 is an illegal value and MUST NOT be allocated to or used by any implementation. KV TIEs received with this value and MUST be discarded and logged on receipt.¶
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 Experimental Key-Type MUST support the use of a Key Sub-Type. The Key Identifier will be used to identify the specific key and the semantics of any 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) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This section reserves a value in the RIFT Key-Type Registry to indicate a Well-Known Key-Type.¶
As shown in Figure 4, the Key-Type will be used to identify the Key-Type as Well-Known. The Well-Known Key-Type MUST support the use of a Key Sub-Type. The Key Identifier will be used to identify the specific key and the semantics of any 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) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 the semantics of any 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 3 | OUI Key Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vendor Specific Values (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NOTE: This document uses the terms to denote directionality, specifically, "northbound" meaning "toward the top of the fabric" and "southbound" meaning "toward the bottom of the fabric".¶
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.¶
It is possible that deployments may have nodes with differing software implementations where some nodes support a given KV TIE and others do not. In this scenario, nodes that receive KV TIEs that they don't recognize (e.g., an unknown Key-Type) will continue to flood them as specified in RIFT [RFC9692].¶
In cases where KV TIEs are flooded southbound, 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 southbound. RIFT [RFC9692] 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 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.¶
This section reserves a Key Sub-Type from the RIFT Well-Known Key Sub-Types registry.¶
This Key-Value pair contains information that allows implementations to test and verify proper tie-breaking behavior for the Southbound Key store. All implementations SHOULD support this Sub-Type.¶
All implementations SHOULD use the Appendix A.1 Thrift model¶
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 | 127 | Key Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (System ID, | | Level), | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
where:¶
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.¶
Figure 7 illustrates the format.¶
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 Target | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Key-Type | Key Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Values (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
A value of all 0s indicates 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 indicates 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. Note that while the algorithm is shown using example code written in [Rust], this document does not mandate the use of any particular language for implementation.¶
<CODE BEGINS>
/// 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 | (1 << nv))
}
<CODE ENDS>¶
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.¶
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.¶
Per [RFC8126], IANA is requested to create two new registries in the "Routing in Fat Trees (RIFT)" registry group at https://www.iana.org/assignments/rift¶
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.¶
This section requests that IANA create and help govern the following registry:¶
This section requests that IANA register the following suggested values to the "RIFT Key-Types" registry.¶
| Value | Key-Type | Description | 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. |
This section requests that IANA create and help govern the following registry:¶
This section requests that IANA register the following suggested values to the "RIFT Well-Known Key Sub-Types" Registry.¶
| Value | Key-Identifier | Description | Reference |
|---|---|---|---|
| 0 | Illegal | Not allowed. | This document. |
| 127 | Southbound Tie-Break Key Sub-Type | Used for Southbound Keystore tie-breaking testing and verification. | This document. |
Experts reviewing requests for values from the "RIFT Key-Types" registry or the "RIFT Well-Known Key-Types" registry are responsible for the following:¶
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 permanent and publicly available.¶
Ensuring that the specification properly defines if Key Sub-Types are used and how the Key Identifier value is derived.¶
Ensuring that any requests are made available to the RIFT working group for review should the work originate from outside the RIFT Working Group.¶
Ensuring that any work produce outside of the IETF does not conflict with any work that is already published or actively pursuing being published.¶
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 [RFC9692] protocol specification itself.¶
Thanks to Italo Busi for his very thoughtful review which yielded and improved spec.¶
This section contains the Thrift model that MAY be used to test southbound Key-Value tie-breaking based on System ID. Per the main RIFT [RFC9692] specification, all signed values MUST be interpreted as unsigned values.¶
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,
}
¶