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RIFT Auto-Flood Reflection
draft-head-rift-auto-fr-02

Document Type Active Internet-Draft (individual)
Authors Jordan Head , Tony Przygienda , Colby Barth
Last updated 2022-10-24
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draft-head-rift-auto-fr-02
RIFT                                                        J. Head, Ed.
Internet-Draft                                             T. Przygienda
Intended status: Standards Track                                C. Barth
Expires: 27 April 2023                                  Juniper Networks
                                                         24 October 2022

                       RIFT Auto-Flood Reflection
                       draft-head-rift-auto-fr-02

Abstract

   This document specifies procedures where RIFT can automatically
   provision IS-IS Flood Reflection topologies by leveraging its native
   no-touch ZTP architecture.

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
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   This Internet-Draft will expire on 27 April 2023.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Design Considerations . . . . . . . . . . . . . . . . . . . .   3
   3.  Auto-FR Device Roles  . . . . . . . . . . . . . . . . . . . .   4
     3.1.  All Participating Nodes . . . . . . . . . . . . . . . . .   4
     3.2.  Flood Reflectors  . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Flood Reflector Spines  . . . . . . . . . . . . . . . . .   5
     3.4.  Flood Reflectors Clients  . . . . . . . . . . . . . . . .   5
   4.  Auto-FR Variable Derivation . . . . . . . . . . . . . . . . .   5
     4.1.  RIFT System ID  . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Auto-FR Version . . . . . . . . . . . . . . . . . . . . .   6
     4.3.  Flood Reflection Cluster ID . . . . . . . . . . . . . . .   6
     4.4.  Flood Reflection Preference . . . . . . . . . . . . . . .   6
     4.5.  IS-IS System ID . . . . . . . . . . . . . . . . . . . . .   7
     4.6.  IS-IS NET Address . . . . . . . . . . . . . . . . . . . .   7
     4.7.  Loopback Address  . . . . . . . . . . . . . . . . . . . .   7
       4.7.1.  Leaf Nodes as Flood Reflector Clients . . . . . . . .   7
       4.7.2.  ToF Nodes as Flood Reflectors . . . . . . . . . . . .   8
         4.7.2.1.  Flood Reflector Election Procedures . . . . . . .   8
   5.  RIFT Requirements . . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  RIFT FSM / LIE Validation Requirements  . . . . . . . . .   9
     5.2.  RIFT Node-TIE Advertisements  . . . . . . . . . . . . . .   9
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .   9
     6.1.  RIFT Underlay and IS-IS Flood Reflection Topology . . . .   9
     6.2.  Auto-FR Analytics . . . . . . . . . . . . . . . . . . . .  11
       6.2.1.  Auto-FR Analytics (Global) Key/Value Pair . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  14
   Appendix A.  Thrift Models  . . . . . . . . . . . . . . . . . . .  14
     A.1.  common.thrift . . . . . . . . . . . . . . . . . . . . . .  14
     A.2.  encoding.thrift . . . . . . . . . . . . . . . . . . . . .  15
     A.3.  auto_flood_reflection_kv.thrift . . . . . . . . . . . . .  16
   Appendix B.  Auto-FR Variable Derivation  . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Introduction

   [RIFT] is a protocol that focuses heavily on operational simplicity.
   It natively supports Zero Touch Provisioning (ZTP) functionality that
   allows each node to automatically derive its place in the topology
   and configure itself accordingly when properly cabled as a Clos, Fat-
   Tree, or other similarly structured variant.

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   IS-IS Flood Reflection [IS-IS-FR] is a mechanism that enables flat
   single-area Level 2 IS-IS topologies to scale well beyond their
   typical properties when deployed in similar topological structures
   by:

   1.  Reducing the number of required links and adjacencies.

   2.  Reducing the size of the Link-State Database.

   3.  Reducing the amount of flooding.

   4.  Reducing the number of SPF computations.

   5.  Reducing the maximum SPF computation time.

   RIFT Auto-Flood Reflection (Auto-FR) combines these technologies by
   using RIFT's ZTP functionality in order to automatically provision
   IS-IS Flood Reflection topologies in a completely distributed
   fashion.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Design Considerations

   IS-IS Flood Reflection operates using Flood Reflectors at the top of
   the fabric and Flood Reflector Clients at the bottom of the fabric.
   Any nodes in the middle are not required to support Flood Reflection
   functionality, nor do they need to support Auto-FR.

   Nodes in a Flood Reflection topology require specific variables for
   deployment.  For example, a Cluster ID that is unique to the
   particular fabric or loopback addresses that are unique to a
   particular node.  RIFT has enough topological information to derive
   these variables with the appropriate scope in a distributed fashion
   automatically.

   Once the Flood Reflection topology is built, RIFT Key-Value TIEs can
   be used to distribute operational state information to allow for
   cluster-wide validation without any additional tooling.

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3.  Auto-FR Device Roles

   Auto-FR requires that each node understands its given role within the
   scope of the Flood Reflection deployment, so each node derives the
   necessary variables and resulting configuration.

3.1.  All Participating Nodes

   Not all nodes have to participate in Auto-FR, however, if a node does
   assume an Auto-FR role, it MUST be capable of deriving the following
   variables:

      *Flood Reflection Cluster ID*
         The Flood Reflection Cluster ID us to distinguish reflection
         domains (similar to the Cluster ID use in BGP Route
         Reflection).

      *IPv6 Loopback Address*
         Unique IPv6 loopback address.

      *IS-IS System ID*
         The IS-IS System Identifier used in deriving the IS-IS NET
         Address.

      *IS-IS NET Address*
         The IS-IS NET Address used to uniquely identify an IS-IS node.

3.2.  Flood Reflectors

   This section defines an Auto-FR role whereby some ToF (Top-of-Fabric)
   nodes act as IS-IS Flood Reflectors.  It is expected that Flood
   Reflectors will establish Level 2 IS-IS adjacencies with Flood
   Reflector Clients in the same area, in the same fabric.  The typical
   Flood Reflector requirements do not change, however, determining
   which specific values to use requires further consideration.

   ToF nodes performing Flood Reflector functionality MUST derive the
   following variables:

      *IPv6 Flood Reflector Loopback Address*
         Unique IPv6 loopback address.

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3.3.  Flood Reflector Spines

   In the context of Auto-FR, a "spine" can simply be desribed as an
   Auto-FR node not running as a Flood Reflector (ToF) or Flood
   Reflector Client (leaf).  While RIFT Auto-FR is not required to run
   on spine nodes and as such a spine role has no specific variables to
   derive at this time, it may be desirable to do so to facilitate the
   use of Auto-FR specific Key-Value TIEs.

   This section also serves as a placeholder for future considerations
   and enhancements.

      *Future Consideration*
         Future Consideration

3.4.  Flood Reflectors Clients

   Although no specific variables for Flood Reflector Clients are
   described at this time, the generic role is specified as a
   placeholder for future enhancements.

      *Future Consideration*
         Future Consideration

4.  Auto-FR Variable Derivation

   As previously mentioned, not all nodes are required to derive all
   variables in a network.  For example, spine nodes may only be
   required for transit traffic and not need to support Auto-FR at all.
   All variables are derived from RIFT's FSM or ZTP mechanism, so no
   additional flooding other than RIFT's typical flooding is required.

   It is also important to mention that all variable derivation is in
   some way based on the RIFT System ID and/or Cluster ID and MUST
   comply precisely with calculation methods specified in the Auto-FR
   Variable Derivation section to allow interoperability between
   different implementations.  All necessary foundational code elements
   are also mentioned there.

4.1.  RIFT System ID

   The 64-bit RIFT System ID that uniquely identifies a node as defined
   in RIFT [RIFT].  This not derived specifically for Auto-FR, but for
   all RIFT nodes and is used in the derivation procedures described in
   this section.

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4.2.  Auto-FR Version

   This section describes extensions to both the RIFT LIE and Node-TIE
   packet schemas in the form of a 16-bit value that identifies the
   Auto-FR Version.  Auto-FR capable nodes MUST support this extension,
   but MAY choose not to advertise it in LIEs and Node-TIEs when Auto-FR
   is not being utilized.

   The complete encoding.thrift schema documented in RIFT [RIFT]
   describes both major and minor protocol/schema versions.  Auto-FR
   Version calculation is done by multiiplying a static value of 256 by
   the major version then adding the minor version, that is to say - 256
   * MAJOR + MINOR.

   This section also describes an extension to the NodeCapabilities
   schema indicating whether or not a node supports Auto-FR.

   The appendix (Appendix A) details necessary changes to the LIEPacket,
   NodeTIEElement, and NodeCapabilities Thrift schemas.

4.3.  Flood Reflection Cluster ID

   This section describes extensions to both the RIFT LIE and Node-TIE
   packet schemas in the form of a 32-bit value that identifies the
   Auto-FR Cluster ID.  Auto-FR capable nodes MUST support this
   extension, but MAY choose not to advertise it in LIEs and Node-TIEs
   when Auto-FR is not being utilized.

   Deployments using more than one Auto-FR cluster MUST use different
   Cluster IDs.  Failure to do so may cause sub-optimal routing as L1/L2
   nodes from different clusters would belong to the same subnet.

   A Cluster ID with a value of 0 is considered invalid and MUST NOT be
   used for any purpose.

   The appendix (Appendix A) details necessary changes to the LIEPacket
   and NodeTIEElement Thrift schemas.

4.4.  Flood Reflection Preference

   This section describes extensions to the Node-TIE packet schema in
   the form of a 32-bit value that indicates a Flood Reflection
   Preference value to be used during Flood Reflector election
   procedures with the higher value being preferred.  Auto-FR capable
   nodes MUST support this extension.

   The appendix (Appendix A) details necessary changes to the
   NodeTIEElement Thrift schemas.

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4.5.  IS-IS System ID

   Auto-FR nodes MUST derive a unique 8-byte IS-IS System ID for use in
   deriving the IS-IS NET Address.  Calculation is done using the 8-byte
   RIFT System ID and 4-byte Cluster ID.

   In order for nodes to derive an IS-IS System ID, the following
   algorithms are required - auto_fr_cidsid2isissid (Figure 9) and
   auto_fr_v6hash (Figure 14).

4.6.  IS-IS NET Address

   Auto-FR nodes MUST derive a unique 10-byte IS-IS NET (Network Entity
   Title) Address to uniquely identify itself within the Flood
   Reflection topology.  The 1st byte (which indicates the AFI) MUST
   have a value of "49".  The last byte (i.e. the NSEL) MUST have a
   value of 0.  Remaining calculation is done using the 8-byte RIFT
   System ID and 4-byte Cluster ID.

   In order for nodes to derive an IS-IS NET Address, the following
   algorithms are required - auto_fr_cidsid2isisnet (Figure 8) and
   auto_fr_cidsid2isissid (Figure 9).

4.7.  Loopback Address

   Auto-FR nodes MUST derive a ULA-scoped IPv6 loopback address to be
   used in IS-IS.  Calculation is done using the 6-bytes of reserved ULA
   space, the 4-byte Cluster ID, and the node's 8-byte RIFT System ID.
   Derivation of the IS-IS System ID varies slightly depending upon the
   node's location/role in the fabric and will be described in
   subsequent sections.

4.7.1.  Leaf Nodes as Flood Reflector Clients

   Leaf Nodes acting as Flood Reflector Clients MUST derive their
   loopback address according to the specific section describing the
   algorithm.  Calculation is done using the 6-bytes of reserved ULA
   space, the 4-byte Cluster ID, and the 8-byte RIFT System ID.

   In order for leaf nodes to derive IPv6 loopbacks, the following
   algorithms are required - auto_fr_cidsidv6loopback (Figure 11) and
   auto_fr_v6prefixcidsid2loopback (Figure 15).

   IPv4 addresses MAY be supported, but it should be noted that they
   have a higher likelihood of collision.  The appendix contains the
   required auto_fr_cidsid2v4loopback (Figure 10) algorithm to support
   IPv4 loopback derivation.

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4.7.2.  ToF Nodes as Flood Reflectors

   ToF nodes acting as Flood Reflectors MUST derive their loopback
   address according to the specific section describing the algorithm.
   Calculation is done using the 6-bytes of reserved ULA space, the
   4-byte Cluster ID, and the 8-byte RIFT System ID.

   In order for ToF nodes to derive IPv6 loopbacks, the following
   algorithms are required - auto_fr_cidsidv6loopback (Figure 11),
   auto_fr_v6prefixcidsid2loopback (Figure 15), and
   auto_fr_cidfrpref2frloopback (Figure 7).

   IPv4 addresses MAY be supported, but it should be noted that they
   have a higher likelihood of collision.  The appendix contains the
   required auto_fr_cidsid2v4loopback (Figure 10) algorithm to support
   IPv4 loopback derivation.

4.7.2.1.  Flood Reflector Election Procedures

   Each ToF performs the election independently based on the RIFT System
   IDs and a Flood Reflection preference value of other ToF nodes in the
   fabric obtained via southbound reflection.  The Flood Reflector
   election procedures are defined as follows:

   1.  Highest System ID with the highest preference.

   2.  Lowest System ID with the highest preference.

   3.  2nd highest System ID with the 2nd highest preference.

   4.  etc.

   This ordering is necessary to prevent a single node with either the
   highest or lowest System ID from triggering changes to flood
   reflector loopback addresses as it would result in all IS-IS
   adjacencies flapping.

   For example, if ToF01 (System ID: 002c6af5a281c000 / FR Preference:
   100) and ToF02 (System ID: 002c6bf5788fc000 / FR Preference: 1) went
   through the election process, ToF02 would be elected due to it having
   the highest System ID.  If a ToF determines that it is elected as a
   Flood Reflector, it uses the knowledge of its position in the list to
   derive Flood Reflector IPv6 loopback address.

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   A topology MUST elect at least 1 ToF node as an IS-IS Flood
   Reflector, but SHOULD elect 3.  The election process varies depending
   upon whether or not the topology is comprised of a single plane or
   multiple planes.  The multiplane election procedure will be described
   in a future version of this document.

   The algorithm shown in "auto_fr_sids2frs" (Figure 12) is required to
   perform the Flood Reflector election procedures.

5.  RIFT Requirements

5.1.  RIFT FSM / LIE Validation Requirements

   RIFT FSM adjacency rules MUST consider Auto-FR Version (Section 4.2)
   and Auto-FR Cluster ID (Section 4.3) values so that nodes that do not
   support Auto-FR can interoperate with nodes that do.  The LIE
   validation is extended with the following clause and if it is not
   met, miscabling should be declared:

   (if auto_flood_reflection_version is not advertised by either node OR
    if auto_flood_reflection_version is identical on both nodes)
       AND
   (auto_flood_reflection_cluster_id is not advertised by either node OR
    auto_flood_reflection_cluster_id is identical on both nodes)

5.2.  RIFT Node-TIE Advertisements

   All nodes utilizing Auto-FR MUST advertise their Auto-FR Version
   (Section 4.2), Flood Reflection Cluster ID (Section 4.3), and Flood
   Reflection Preference (Section 4.4) values in at least one Node-TIE
   in each direction (i.e.  North and South).

6.  Operational Considerations

   To fully realize the benefits of Auto-FR, it may help to describe the
   high-level method.  Simply put, RIFT automatically provisions the
   underlay and Auto-FR provisions the Flood Reflection topology.  The
   goal of this section is to draw simple lines between general fabric
   concepts, RIFT, and Auto-FR and how they fit into current network
   designs and practices.

   This section also describes a set of optional Key-Value TIEs
   [RIFT-KV] that leverages the variables that have already been derived
   to provide further operational enhancement to the operator.

6.1.  RIFT Underlay and IS-IS Flood Reflection Topology

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                      +-----------------+   +-----------------+
                      | ToF-01          |   | ToF-02          |
                      | L1 / L2         |   | L1 / L2         |  ]----------------------+
                      | Flood Reflector |   | Flood Reflector |                         |
                      +-+--+------+--+--+   +-+--+------+--+--+                         |
                        |  |      |  |        |  |      |  |                            |
  +---------------------+  |      |  |        |  |      |  |                            |
  |                        |      |  |        |  |      |  +---------------------+      |
  |            +-----------)------)--)--------+  |      |                        |      |
  |            |           |      |  |   +-------+      |                        |      |
  |            |           |      |  |   |              |                        |      |
  |            |           |      |  +---)--------------)-----------+            |      |
  |            |           |      |      |              |           |            |      |
  |            |        +--+      +------)----+         +--+        |            |      |
  |            |        |                |    |            |        |            |      |
  |            |        |            +---+    |            |        |            |      | Level 2 Mesh of
  |            |        |            |        |            |        |            |      | Flood Reflection
+-+------------+-+    +-+------------+-+    +-+------------+-+    +-+------------+-+    | Adjacencies
| Spine-1-1      |    | Spine-1-2      |    | Spine-2-1      |    | Spine-2-2      |    | Between ToFs/Leafs
| L1             |    | L1             |    | L1             |    | L1             |    |
| N/A            |    | N/A            |    | N/A            |    | N/A            |    |
+--+----------+--+    +--+----------+--+    +--+----------+--+    +--+----------+--+    |
   |          |          |          |          |          |          |          |       |
   |          +----------)---+      |          |          +----------)---+      |       |
   |                     |   |      |          |                     |   |      |       |
   |          +----------+   |      |          |          +----------+   |      |       |
   |          |              |      |          |          |              |      |       |
+--+----------+--+    +------+------+--+    +--+----------+--+    +------+------+--+    |
| Leaf-1-1       |    | Leaf-1-2       |    | Leaf-2-1       |    | Leaf-2-2       |    |
| L1 / L2        |    | L1 / L2        |    | L1 / L2        |    | L1 / L2        |  ]-+
| FR Client      |    | FR Client      |    | FR Client      |    | FR Client      |
+--+-------------+    +--------------+-+    +--+-------------+    +----------------+
   |                                           |
   |                                           |
   |                                           |
   |                                           |
+--+-------------+                          +--+-----------+-+
| Node A         |                          | Node Z         |
| L2             |                          | L2             |
+----------------+                          +----------------+

                  Figure 1: Auto-FR Example Topology

   Figure 1 illustrates a typical 5-stage Clos IP fabric.  Each node is
   named and labelled in such a way that conveys:

   1.  The node's generic placement within the context of the RIFT
       underlay

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   2.  The node's level(s) within the IS-IS area.

   3.  The node's role within the IS-IS Flood Reflection topology.

   Table 1 should help further align these concepts.

         +================+=============+========================+
         | RIFT Placement | IS-IS Level | IS-IS FR Role          |
         +================+=============+========================+
         | ToF Nodes      | L1/L2       | Flood Reflector        |
         +----------------+-------------+------------------------+
         | Spine Nodes    | L1          | N/A                    |
         +----------------+-------------+------------------------+
         | Leaf Nodes     | L1/L2       | Flood Reflector Client |
         +----------------+-------------+------------------------+

                         Table 1: Role Associations

   Connections between various nodes can be understood in two different
   ways:

   1.  Lines between ToF and leaf nodes are Level 2 IS-IS Flood
       Reflection adjacencies.

   2.  Lines between spine and leaf are part of the physically connected
       underlay.

   3.  Lines between ToF and spine are part of the physically connected
       underlay.

   It is important to remember that Auto-FR is not altering the way in
   which IS-IS Flood Reflection operates in any way, it simply takes
   existing deployment scenarios and simplifies the provisioning
   process.

6.2.  Auto-FR Analytics

   Leaf nodes MAY optionally advertise analytics information about the
   Auto-FR fabric to ToF nodes using RIFT Key-Value TIEs [RIFT-KV].
   This may be helpful in that validation and troubleshooting activities
   can be performed on the ToF nodes rather than manually verifying the
   state separately on multiple leaf nodes.

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6.2.1.  Auto-FR Analytics (Global) Key/Value Pair

   This Key/Value pair describes node level information within the
   context of the Flood Reflection topology.  The RIFT System ID of the
   advertising leaf node MUST be used to differentiate the node among
   other nodes in the fabric.

   The Auto-FR Analytics (Global) Key/Value pair MUST be advertised with
   the 3rd and 4th bytes of the Key Identifier consisting of all 0s.

      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  |           Auto-FR Analytics (Global)           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     (Auto-FR Role,                                            |
     |      Flood Reflection Cluster ID,                             |
     |      Established IS-IS FR L2 Adjacencies,                     |
     |      Total IS-IS FR L2 Adjacencies,                           |
     |      Established IS-IS FR L1 Shortcut Adjacencies,            |
     |      Total IS-IS FR L1 Shortcut Adjacencies,                  |
     |      Established IS-IS L1 Adjacencies,                        |
     |      Total IS-IS L1 Adjacencies,)                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 2: Auto-FR Global Key/Value Pair

   *where:*

      *Auto-FR Role:*
         A REQUIRED value indicating the node's Auto-FR role within the
         fabric.

         *0:*  Illegal value, MUST NOT be used.

         *1:*  Auto-FR Flood Reflector Client

         *2:*  Auto-FR Flood Reflector

         *3:*  Auto-FR Spine (i.e. a non-ToF / non-Leaf node)

      *Auto-FR Cluster ID*
         A REQUIRED 32-bit integer indicating the Auto-FR Cluster ID of
         the local node.

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      *Established IS-IS Flood Reflector Adjacency Count*
         A RECOMMENDED 16-bit integer indicating the number of IS-IS
         Level 2 Flood Reflector adjacencies in the "Up" state on the
         local node.

      *Total IS-IS Flood Reflector Adjacency Count*
         A RECOMMENDED 16-bit integer indicating the total number of IS-
         IS Level 2 Flood Reflector adjacencies on the local node
         regardless of state.

      *Established IS-IS Level 1 Shortcut Count*
         A RECOMMENDED 16-bit integer indicating the number of
         functional IS-IS Level 1 "shortcuts" on the local node.

      *Total IS-IS Level 1 Shortcut Count*
         A RECOMMENDED 16-bit integer indicating the total number of IS-
         IS Level 1 "shortcuts" the local node regardless of state.

      *Established IS-IS Level 1 Adjacency Count*
         A RECOMMENDED 16-bit integer indicating the number of IS-IS
         Level 1 adjacencies in the "Up" state on the local node.

      *Total IS-IS Level 1 Adjacency Count*
         A RECOMMENDED 16-bit integer indicating the total number of IS-
         IS Level 1 adjacencies on the local node regardless of state.

   Implementations leveraging Thrift for Key-Value functionality SHOULD
   refer to the auto_flood_reflection_kv.thrift (Appendix A.3) schema in
   the appendix.

7.  IANA Considerations

   This section requests the following suggested values from the RIFT
   Well-Known Key-Type Registry.

   +=======+================+==============================+===========+
   | Value | Key-Identifier | Description                  | Status/   |
   |       |                |                              | Reference |
   +=======+================+==============================+===========+
   | 5     | Auto-FR        | Key/Value pair               | This      |
   |       | Analytics      | containing operational       | document. |
   |       | (Global)       | state of a Flood             |           |
   |       |                | Reflector Client node.       |           |
   +-------+----------------+------------------------------+-----------+

      Table 2: Auto-FR Suggested Value(s) for RIFT Well-Known Key-Type
                                  Registry

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8.  Security Considerations

   This document introduces no new security concerns to RIFT or other
   specifications referenced in this document as RIFT natively secures
   LIE and TIE packets as described in [RIFT].

9.  Acknowledgements

   This section will be used to acknowledge major contributors.

10.  References

10.1.  Normative References

   [IS-IS-FR] Przygienda, A., Bowers, C., Lee, Y., Sharma, A., and R.
              White, "IS-IS Flood Reflection", Work in Progress, draft-
              ietf-lsr-isis-flood-reflection-07, November 2021.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", June
              2017, <https://www.rfc-editor.org/info/rfc8126>.

   [RIFT]     Przygienda, T., Sharma, A., Thubert, P., Rijsman, B., and
              D. Afanasiev, "RIFT: Routing in Fat Trees", Work in
              Progress, draft-ietf-rift-rift-15, December 2021.

   [RIFT-KV]  Head, J. and T. Przygienda, "RIFT Key/Value Structure and
              Registry", Work in Progress, draft-ietf-rift-kv-registry-
              01, June 2022.

Appendix A.  Thrift Models

   This section contains the normative Thrift models required to support
   Auto-FR.  Per the main RIFT [RIFT] specification, all signed values
   MUST be interpreted as unsigned values.

A.1.  common.thrift

   This section specifies extensions to RIFT common.thrift model.

   These extensions are REQUIRED in order to support Auto-FR.

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  ...
  enum AutoFRModel {
      TunnelMode      = 0,
      NoTunnelMode    = 1,
  }

  const AutoFRModel default_autofr_model = AutoFRModel.TunnelMode

  typedef i32          FloodReflectionClusterIDType

  const FloodReflectionClusterIDType  IllegalClusterID = 0
  const FloodReflectionClusterIDType  DefaultClusterID  = 1

  /// preference to become FR, higher is better
  typedef i32          FloodReflectionPreferenceType

  const   FloodReflectionPreferenceType MinFloodReflectionPreference = 0

  ...

                  Figure 3: RIFT Auto-FR: common.thrift

A.2.  encoding.thrift

   This section specifies extensions to RIFT encoding.thrift model.

   These extensions are REQUIRED in order to support Auto-FR.

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struct NodeCapabilities {
...
   /** indicates whether auto-flood-reflection feature is implemented on this node (but not necessarily enabled). */
   20: optional bool                           auto_flood_reflection_support = false;
...
}

struct LIEPacket {
...
   /** It provides optional version of FR ZTP as 256 * MAJOR + MINOR, indicates support for auto FR  */
   40: optional i16                                      auto_flood_reflection_version;

   41: optional common.FloodReflectionClusterIDType      auto_flood_reflection_cluster_id;
...
}

struct NodeTIEElement {
...
   /** All Auto FR elements MUST be present in at least one TIE in each direction if auto FR is running.  */
   /** It provides optional version of FR ZTP as 256 * MAJOR + MINOR, indicates support for auto FR  */
   30: optional i16                                     auto_flood_reflection_version;
   /** cluster ID of Auto FR */
   31: optional common.FloodReflectionClusterIDType     auto_flood_reflection_cluster_id;
   /** preference to become FR */
   32: optional common.FloodReflectionPreferenceType    auto_flood_reflection_preference;
...
}

               Figure 4: RIFT Auto-FR: encoding.thrift

A.3.  auto_flood_reflection_kv.thrift

   This section defines auto_flood_reflection_kv.thrift as a method of
   supporting Auto-FR analytics functionality.

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include "common.thrift"

namespace py auto_flood_reflection_kv
namespace rs models

typedef i32         AutoFRKeyIdentifier

typedef i16         AutoFRCounterType
typedef i32         AutoFRLongCounterType

const i8            GlobalAutoFRTelemetryKV  = 5

/** We don't need the full role structure, only an indication of the node's basic role */
enum AutoFRRole {
    ILLEGAL            = 0,
    auto_fr_leaf       = 1,
    auto_fr_reflector  = 2,
    auto_fr_spine      = 3, // i.e. non-(ToF|Leaf)
}

/** Auto-FR Global (Node) Telemetry

    1st     byte  MUST be = "Well-Known"
    2nd     byte  MUST be = "GlobalAutoFRTelemetryKV"
    3rd/4th bytes MUST be = all 0s

    Flooding Scope: Leaves only
*/
struct AutoFRTelemetryGlobalKV {
    1: required   set<AutoFRRole>                           auto_fr_roles,
    2: required   common.FloodReflectionClusterIDType       cluster_id,

    3: optional   AutoFRCounterType                         established_isis_fr_adjacencies_count,

    4: optional   AutoFRCounterType                         total_isis_fr_adjacencies_count,

    5: optional   AutoFRCounterType                         established_isis_l1_shortcut_adjacencies_count,

    6: optional   AutoFRCounterType                         total_isis_l1_shortcut_adjacencies_count,

    7: optional   AutoFRCounterType                         established_isis_l1_adjacencies_count,

    8: optional   AutoFRCounterType                         total_isis_l1_adjacencies_count,
}

       Figure 5: RIFT Auto-FR: auto_flood_reflection_kv.thrift

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Appendix B.  Auto-FR Variable Derivation

   This section contains the normative variable derivation algorithms
   that are REQUIRED to support Auto-FR.

/// indicates how many FRs we're computing in AUTO FR
pub const MAX_AUTO_FR_FRS: usize = 3;

/// indicates the cluster has no ID, used in computations to omit effects of cluster ID
pub const NO_CLUSTER_ID: FloodReflectionClusterIDType = 0;

/// unique v6 prefix for all nodes starts with this
pub fn auto_fr_v6pref(cid: FloodReflectionClusterIDType) -> String {
    format!("FD00:{:04X}:B1", cid)
}

/// how many bytes in a v6pref for different purposes
pub const AUTO_FR_V6PREFLEN: usize = 8 * 5;

/// unique v6 prefix for flood reflector purposes starts like this
pub fn auto_fr_v6frpref(cid: FloodReflectionClusterIDType) -> String {
    format!("FD00:{:04X}:B2", cid)
}

/// unique v4 prefix for IRB purposes
pub const AUTO_FR_V4LOOPBACKNET: u8 = 10;
pub const AUTO_FR_V4LOOPBACKMASK : usize = 8;

         Figure 6: RIFT Auto-FR: auto_fr_const_structs_types

/// auto FR V6 loopback for FRs
pub fn auto_fr_cidfrpref2frloopback(cid: FloodReflectionClusterIDType,
                                      preference: u8) -> Result<Ipv6Addr, ServiceErrorType> {
    auto_fr_v6prefixcidsid2loopback(&auto_fr_v6frpref(cid), cid, (1 + preference) as _)
}

         Figure 7: RIFT Auto-FR: auto_fr_cidfrpref2frloopback

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pub fn auto_fr_cidsid2isisnet(cid: FloodReflectionClusterIDType, sid: UnsignedSystemID) -> Vec<u8> {
    let mut r = vec![0x49]; // magic AFI

    // area ID derived from cluster ID
    r.extend(&cid.to_ne_bytes().iter().fold(0x77u16,
                                            |prev, val| (prev ^ (val.rotate_right(4) as u16))).to_ne_bytes());
    // ISIS ID derived from system ID + cid/sid
    r.extend(auto_fr_cidsid2isissid(cid, sid).into_iter());
    // selector non v-node
    r.push(0);

    r
}

            Figure 8: RIFT Auto-FR: auto_fr_cidsid2isisnet

   /// ISIS system ID derivation
   pub fn auto_fr_cidsid2isissid(
       cid: FloodReflectionClusterIDType,
       sid: UnsignedSystemID) -> Vec<u8> {

       let sb = auto_fr_v6hash(cid, sid);

       vec![sb[0],
            sb[1],
            sb[2],
            sb[3],
            sb[4] ^ sb[5].rotate_right(4),
            sb[6] ^ sb[7].rotate_right(4),
       ]
   }

               Figure 9: RIFT Auto-FR: auto_fr_cidsid2isissid

/// v4 loopback address derivation for every node in auto-fr, returns address and
/// subnet mask length.
pub fn auto_fr_cidsid2v4loopback(cid: FloodReflectionClusterIDType, sid: UnsignedSystemID) -> (IPv4Address, u8) {
    let mut derived = sid.to_ne_bytes().iter()
        .fold(0 as IPv4Address, |p, e| (p << 4) ^ (*e as IPv4Address));
    derived ^= cid as IPv4Address;
    // use the byte we loose for entropy
    derived ^= derived >> (32 - AUTO_FR_V4LOOPBACKMASK);
    // and sanitize for loopback range, we nuke 8 bits out
    derived &= (!U32MASKS[AUTO_FR_V4LOOPBACKMASK]) as IPv4Address;

    let m = ((AUTO_FR_V4LOOPBACKNET as IPv4Address) << (32 - AUTO_FR_V4LOOPBACKMASK)) | derived;
    (m as _, AUTO_FR_V4LOOPBACKMASK as _)
}

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          Figure 10: RIFT Auto-FR: auto_fr_cidsid2v4loopback

/// V6 loopback derivation for every node in auto fr
pub fn auto_fr_cidsidv6loopback(cid: FloodReflectionClusterIDType,
                                  sid: UnsignedSystemID) -> Result<Ipv6Addr, ServiceErrorType> {
    auto_fr_v6prefixcidsid2loopback(&auto_fr_v6pref(cid), cid, sid)
}

          Figure 11: RIFT Auto-FR: auto_fr_cidsidv6loopback

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/// Function sorts vector of system IDs first,
/// Followed by a shuffle taking largest/smallest/2nd largest/2nd smallest.
/// Preference is used to take the according subsets to run this algorithm
/// sequentially.
pub(crate) fn auto_fr_sids2frs(mut v: Vec<(FloodReflectionPreferenceType,
                                           UnsignedSystemID)>)
                                 -> Vec<UnsignedSystemID> {
    v.par_sort_by(|(p1, s1),
                   (p2, s2)|
        match p2.cmp(p1) {
            Ordering::Equal => s2.cmp(s1),
            e @ _ => e
        });

    let mut elected = vec![];

    while elected.len() < MAX_AUTO_FR_FRS && !v.is_empty() {
        let pref = (&v[0]).0;

        let mut splitat = 0;
        while splitat < v.len() && (&v[splitat]).0 == pref {
            splitat += 1;
        }

        let mut so = v.split_off(splitat);
        std::mem::swap(&mut v, &mut so);

        let mut mixed = if so.len() > 2 {
            let mut s = so.split_off(so.len() / 2);
            s.reverse();
            interleave(so.into_iter(), s.into_iter())
                .collect::<Vec<_>>()
        } else {
            so
        };

        elected.extend(mixed.drain(..))
    }

    elected.drain(..).map(|(_, sid)| sid).collect()
}

              Figure 12: RIFT Auto-FR: auto_fr_sids2frs

   pub(crate) fn auto_fr_v62octets(a: Ipv6Addr) -> Vec<u8> {
       a.octets().iter().cloned().collect()
   }

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                 Figure 13: RIFT Auto-FR: auto_fr_v62octets

/// generic bytes derivation used for different purposes
pub fn auto_fr_v6hash(cid: FloodReflectionClusterIDType, sid: UnsignedSystemID)
                        -> [u8; 8] {
    let sub = (cid as UnsignedSystemID) ^ sid.rotate_right(8);

    sub.to_ne_bytes()
}

               Figure 14: RIFT Auto-FR: auto_fr_v6hash

/// local address with encoded cluster ID and system ID for collision free identifiers. Basis
/// for several different prefixes.
pub fn auto_fr_v6prefixcidsid2loopback(v6pref: &str, cid: FloodReflectionClusterIDType,
                                       sid: UnsignedSystemID) -> Result<Ipv6Addr, ServiceErrorType> {
    assert!(cid != ILLEGAL_CLUSTER_I_D);
    let a = format!("{}00::{}",
                    v6pref,
                    sid.to_ne_bytes()
                        .iter()
                        .chunks(2)
                        .into_iter()
                        .map(|chunk|
                            chunk.fold(0u16, |v, n| (v << 8) | *n as u16))
                        .map(|v| format!("{:04X}", v))
                        .collect::<Vec<_>>()
                        .into_iter()
                        .join(":")
    );

    Ipv6Addr::from_str(&a)
        .map_err(|_| ServiceErrorType::INTERNALRIFTERROR)
}

       Figure 15: RIFT Auto-FR: auto_fr_v6prefixcidsid2loopback

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/// cluster prefixes derived instead of advertising default on the cluster to allow
/// for default route on ToF or leaves
pub fn auto_fr_cid2cluster_prefixes(cid: FloodReflectionClusterIDType) -> Result<Vec<IPPrefixType>, ServiceErrorType> {
    vec![
        (auto_fr_cidsidv6loopback(cid, ILLEGAL_SYSTEM_I_D as _), AUTO_FR_V6PREFLEN),
        (auto_fr_cidfrpref2frloopback(cid, 0 as _), AUTO_FR_V6PREFLEN),
    ]
        .into_iter()
        .map(|(p, _)|
            match p {
                Ok(_) => Ok(
                    IPPrefixType::Ipv6prefix(
                        IPv6PrefixType {
                            address: auto_fr_v62octets(p?),
                            prefixlen: AUTO_FR_V6PREFLEN as _,
                        })),
                Err(e) => Err(e),
            }
        )
        .collect::<Result<Vec<_>, _>>()
}

        Figure 16: RIFT Auto-FR: auto_fr_cid2cluster_prefixes

Authors' Addresses

   Jordan Head (editor)
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, CA
   United States of America
   Email: jhead@juniper.net

   Tony Przygienda
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, CA
   United States of America
   Email: prz@juniper.net

   Colby Barth
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, CA
   United States of America
   Email: cbarth@juniper.net

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