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rfc:rfc8542

Internet Engineering Task Force (IETF) Y. Zhuang Request for Comments: 8542 D. Shi Category: Standards Track Huawei ISSN: 2070-1721 R. Gu

                                                          China Mobile
                                                    H. Ananthakrishnan
                                                               Netflix
                                                            March 2019
   A YANG Data Model for Fabric Topology in Data-Center Networks

Abstract

 This document defines a YANG data model for fabric topology in data-
 center networks and represents one possible view of the data-center
 fabric.  This document focuses on the data model only and does not
 endorse any kind of network design that could be based on the
 abovementioned model.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 https://www.rfc-editor.org/info/rfc8542.

Copyright Notice

 Copyright (c) 2019 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
 Provisions Relating to IETF Documents
 (https://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Zhuang, et al. Standards Track [Page 1] RFC 8542 Data Model for DC Fabric Topology March 2019

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
 2.  Definitions and Acronyms  . . . . . . . . . . . . . . . . . .   3
   2.1.  Key Words . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
 3.  Model Overview  . . . . . . . . . . . . . . . . . . . . . . .   4
   3.1.  Topology Model Structure  . . . . . . . . . . . . . . . .   4
   3.2.  Fabric Topology Model . . . . . . . . . . . . . . . . . .   4
     3.2.1.  Fabric Topology . . . . . . . . . . . . . . . . . . .   5
     3.2.2.  Fabric Node Extension . . . . . . . . . . . . . . . .   6
     3.2.3.  Fabric Termination-Point Extension  . . . . . . . . .   7
 4.  Fabric YANG Modules . . . . . . . . . . . . . . . . . . . . .   8
 5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
 6.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
 7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
   7.1.  Normative References  . . . . . . . . . . . . . . . . . .  23
   7.2.  Informative References  . . . . . . . . . . . . . . . . .  24
 Appendix A.  Non-NMDA-State Modules . . . . . . . . . . . . . . .  25
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  32
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  32

1. Introduction

 A data-center (DC) network can be composed of single or multiple
 fabrics, which are also known as Points Of Delivery (PODs).  These
 fabrics may be heterogeneous due to implementation of different
 technologies when a DC network is upgraded or new techniques and
 features are rolled out.  For example, within a DC network, Fabric A
 may use Virtual eXtensible Local Area Network (VXLAN) while Fabric B
 may use VLAN.  Likewise, an existing fabric may use VXLAN while a new
 fabric (for example, a fabric introduced for DC upgrade and
 expansion) may implement a technique discussed in the NVO3 Working
 Group, such as Geneve [GENEVE].  The configuration and management of
 such DC networks with heterogeneous fabrics could result in
 considerable complexity.
 For a DC network, a fabric can be considered as an atomic structure
 for management purposes.  From this point of view, the management of
 the DC network can be decomposed into a set of tasks to manage each
 fabric separately, as well as the fabric interconnections.  The
 advantage of this method is to make the overall management tasks
 flexible and easy to extend in the future.
 As a basis for DC fabric management, this document defines a YANG
 data model [RFC6020] [RFC7950] for a possible view of the fabric-
 based data-center topology.  To do so, it augments the generic

Zhuang, et al. Standards Track [Page 2] RFC 8542 Data Model for DC Fabric Topology March 2019

 network and network topology data models defined in [RFC8345] with
 information that is specific to data-center fabric networks.
 The model defines the generic configuration and operational state for
 a fabric-based network topology, which can subsequently be extended
 by vendors with vendor-specific information as needed.  The model can
 be used by a network controller to represent its view of the fabric
 topology that it controls and expose this view to network
 administrators or applications for DC network management.
 Within the context of topology architecture defined in [RFC8345],
 this model can also be treated as an application of the Interface to
 the Routing System (I2RS) network topology model [RFC8345] in the
 scenario of data-center network management.  It can also act as a
 service topology when mapping network elements at the fabric layer to
 elements of other topologies, such as L3 topologies as defined in
 [RFC8346].
 By using the fabric topology model defined in this document, people
 can treat a fabric as a holistic entity and focus on its
 characteristics (such as encapsulation type and gateway type) as well
 as its connections to other fabrics, while putting the underlay
 topology aside.  As such, clients can consume the topology
 information at the fabric level with no need to be aware of the
 entire set of links and nodes in the corresponding underlay networks.
 A fabric topology can be configured by a network administrator using
 the controller by adding physical devices and links into a fabric.
 Alternatively, fabric topology can be learned from the underlay
 network infrastructure.

2. Definitions and Acronyms

2.1. Key Words

 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.

2.2. Terminology

 POD: a module of network, compute, storage, and application
 components that work together to deliver networking services.  It
 represents a repeatable design pattern.  Its components maximize the
 modularity, scalability, and manageability of data centers.
 Fabric: composed of several PODs to form a data-center network.

Zhuang, et al. Standards Track [Page 3] RFC 8542 Data Model for DC Fabric Topology March 2019

3. Model Overview

 This section provides an overview of the DC fabric topology model and
 its relationship with other topology models.

3.1. Topology Model Structure

 The relationship of the DC fabric topology model and other topology
 models is shown in Figure 1.
           +------------------------+
           |      network model     |
           +------------------------+
                        |
                        |
           +------------V-----------+
           | network topology model |
           +------------------------+
                        |
      +-----------+-----+------+-------------+
      |           |            |             |
  +---V----+  +---V----+   +---V----+   +----V---+
  |   L1   |  |   L2   |   |   L3   |   | Fabric |
  |topology|  |topology|   |topology|   |topology|
  |  model |  |  model |   |  model |   |  model |
  +--------+  +--------+   +--------+   +--------+
              Figure 1: The Network Data Model Structure
 From the perspective of resource management and service provisioning
 for a data-center network, the fabric topology model augments the
 basic network topology model with definitions and features specific
 to a DC fabric, to provide common configuration and operations for
 heterogeneous fabrics.

3.2. Fabric Topology Model

 The fabric topology model module is designed to be generic and can be
 applied to data-center fabrics built with different technologies,
 such as VLAN and VXLAN.  The main purpose of this module is to
 configure and manage fabrics and their connections.  It provides a
 fabric-based topology view for data-center applications.

Zhuang, et al. Standards Track [Page 4] RFC 8542 Data Model for DC Fabric Topology March 2019

3.2.1. Fabric Topology

 In the fabric topology module, a fabric is modeled as a node of a
 network; as such, the fabric-based data-center network consists of a
 set of fabric nodes and their connections.  The following depicts a
 snippet of the definitions to show the main structure of the model.
 The notation syntax follows [RFC8340].
     module: ietf-dc-fabric-topology
     augment /nw:networks/nw:network/nw:network-types:
        +--rw fabric-network!
     augment /nw:networks/nw:network/nw:node:
        +--rw fabric-attributes
           +--rw fabric-id?   fabric-id
           +--rw name?        string
           +--rw type?        fabrictype:underlay-network-type
           +--rw description?    string
           +--rw options
           +--...
     augment /nw:networks/nw:network/nw:node/nt:termination-point:
        +--ro fport-attributes
           +--ro name?          string
           +--ro role?          fabric-port-role
           +--ro type?          fabric-port-type
 The fabric topology module augments the generic ietf-network and
 ietf-network-topology modules as follows:
 o  A new topology type, "ietf-dc-fabric-topology", is defined and
    added under the "network-types" container of the ietf-network
    module.
 o  Fabric is defined as a node under the network/node container.  A
    new container, "fabric-attributes", is defined to carry attributes
    for a fabric such as gateway mode, fabric types, involved device
    nodes, and links.
 o  Termination points (in the network topology module) are augmented
    with fabric port attributes defined in a container.  The
    "termination-point" here is used to represent a fabric "port" that
    provides connections to other nodes, such as an internal device,
    another fabric externally, or end hosts.
 Details of the fabric node and the fabric termination point extension
 will be explained in the following sections.

Zhuang, et al. Standards Track [Page 5] RFC 8542 Data Model for DC Fabric Topology March 2019

3.2.2. Fabric Node Extension

 As an atomic network (that is, a set of nodes and links that composes
 a POD and also supports a single overlay/underlay instance), a fabric
 itself is composed of a set of network elements, i.e., devices and
 related links.  The configuration of a fabric is contained under the
 "fabric-attributes" container depicted as follows.  The notation
 syntax follows [RFC8340].
     +--rw fabric-attributes
        +--rw fabric-id?      fabrictypes:fabric-id
        +--rw name?           string
        +--rw type?           fabrictype:underlay-network-type
        +--rw vni-capacity
        |  +--rw min?   int32
        |  +--rw max?   int32
        +--rw description?    string
        +--rw options
        |  +--rw gateway-mode?           enumeration
        |  +--rw traffic-behavior?       enumeration
        |  +--rw capability-supported* fabrictype:service-capabilities
        +--rw device-nodes* [device-ref]
        |  +--rw device-ref    fabrictype:node-ref
        |  +--rw role*?         fabrictype:device-role
        +--rw device-links* [link-ref]
        |  +--rw link-ref    fabrictype:link-ref
        +--rw device-ports* [port-ref]
           +--rw port-ref     fabrictype:tp-ref
           +--rw port-type?   fabrictypes:port-type
           +--rw bandwidth?   fabrictypes:bandwidth
 In the module, additional data objects for fabric nodes are
 introduced by augmenting the "node" list of the network module.  New
 objects include fabric name, type of the fabric, and descriptions of
 the fabric, as well as a set of options defined in an "options"
 container.  The "options" container includes the gateway-mode type
 (centralized or distributed) and traffic behavior (whether an Access
 Control List (ACL) is needed for the traffic).  Also, it includes a
 list of device nodes and related links as "supporting-node" to form a
 fabric network.  These device nodes and links are represented as
 leaf-refs of existing nodes and links in the underlay topology.  For
 the device node, the "role" object is defined to represent the role
 of a device within the fabric, such as "SPINE" or "LEAF", which
 should work together with the gateway-mode.

Zhuang, et al. Standards Track [Page 6] RFC 8542 Data Model for DC Fabric Topology March 2019

3.2.3. Fabric Termination-Point Extension

 Since a fabric can be considered as a node, "termination-points" can
 represent fabric "ports" that connect to other fabrics and end hosts,
 as well as devices inside the fabric.
 As such, the set of "termination-points" of a fabric indicate all of
 its connections, including its internal connections, interconnections
 with other fabrics, and connections to end hosts.
 The structure of fabric ports is as follows.  The notation syntax
 follows [RFC8340].
     augment /nw:networks/nw:network/nw:node/nt:termination-point:
         +--ro fport-attributes
            +--ro name?          string
            +--ro role?          fabric-port-role
            +--ro type?          fabric-port-type
            +--ro device-port?   tp-ref
            +--ro (tunnel-option)?
 This structure augments the termination points (in the network
 topology module) with fabric port attributes defined in a container.
 New nodes are defined for fabric ports, including fabric name, role
 of the port within the fabric (internal port, external port to
 outside network, access port to end hosts), and port type (L2
 interface, L3 interface).  By defining the device port as a tp-ref, a
 fabric port can be mapped to a device node in the underlay network.
 Additionally, a new container for tunnel-options is introduced to
 present the tunnel configuration on a port.
 The termination point information is learned from the underlay
 networks, not configured by the fabric topology layer.

Zhuang, et al. Standards Track [Page 7] RFC 8542 Data Model for DC Fabric Topology March 2019

4. Fabric YANG Modules

 This module imports typedefs from [RFC8345], and it references
 [RFC7348] and [RFC8344].

<CODE BEGINS> file "ietf-dc-fabric-types@2019-02-25.yang" module ietf-dc-fabric-types {

yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-dc-fabric-types";
prefix fabrictypes;
import ietf-network {
  prefix nw;
  reference
    "RFC 8345: A YANG Data Model for Network Topologies";
}
organization
  "IETF I2RS (Interface to the Routing System) Working Group";
contact
  "WG Web:    <https://datatracker.ietf.org/wg/i2rs/>
   WG List:   <mailto:i2rs@ietf.org>
   Editor:    Yan Zhuang
              <mailto:zhuangyan.zhuang@huawei.com>
   Editor:    Danian Shi
              <mailto:shidanian@huawei.com>";
description
  "This module contains a collection of YANG definitions for
   fabric.
   Copyright (c) 2019 IETF Trust and the persons identified
   as authors of the code.  All rights reserved.
   Redistribution and use in source and binary forms, with
   or without modification, is permitted pursuant to, and
   subject to the license terms contained in, the Simplified
   BSD License set forth in Section 4.c of the IETF Trust's
   Legal Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info).
   This version of this YANG module is part of RFC 8542;
   see the RFC itself for full legal notices.";
revision 2019-02-25 {
  description
    "Initial revision.";

Zhuang, et al. Standards Track [Page 8] RFC 8542 Data Model for DC Fabric Topology March 2019

  reference
    "RFC 8542: A YANG Data Model for Fabric Topology
     in Data-Center Networks";
}
identity fabric-type {
  description
    "Base type for fabric networks";
}
identity vxlan-fabric {
  base fabric-type;
  description
    "VXLAN fabric";
}
identity vlan-fabric {
  base fabric-type;
  description
    "VLAN fabric";
}
identity trill-fabric {
  base fabric-type;
  description
    "TRILL fabric";
}
identity port-type {
  description
    "Base type for fabric port";
}
identity eth {
  base port-type;
  description
    "Ethernet";
}
identity serial {
  base port-type;
  description
    "Serial";
}
identity bandwidth {
  description
    "Base for bandwidth";

Zhuang, et al. Standards Track [Page 9] RFC 8542 Data Model for DC Fabric Topology March 2019

}
identity bw-1M {
  base bandwidth;
  description
    "1M";
}
identity bw-10M {
  base bandwidth;
  description
    "10Mbps";
}
identity bw-100M {
  base bandwidth;
  description
    "100Mbps";
}
identity bw-1G {
  base bandwidth;
  description
    "1Gbps";
}
identity bw-10G {
  base bandwidth;
  description
    "10Gbps";
}
identity bw-25G {
  base bandwidth;
  description
    "25Gbps";
}
identity bw-40G {
  base bandwidth;
  description
    "40Gbps";
}
identity bw-100G {
  base bandwidth;
  description
    "100Gbps";

Zhuang, et al. Standards Track [Page 10] RFC 8542 Data Model for DC Fabric Topology March 2019

}
identity bw-400G {
  base bandwidth;
  description
    "400Gbps";
}
identity device-role {
  description
    "Base for the device role in a fabric.";
}
identity spine {
  base device-role;
  description
    "This is a spine node in a fabric.";
}
identity leaf {
  base device-role;
  description
    "This is a leaf node in a fabric.";
}
identity border {
  base device-role;
  description
    "This is a border node to connect to other
     fabric/network.";
}
identity fabric-port-role {
  description
    "Base for the port's role in a fabric.";
}
identity internal {
  base fabric-port-role;
  description
    "The port is used for devices to access each
     other within a fabric.";
}
identity external {
  base fabric-port-role;
  description
    "The port is used for a fabric to connect to

Zhuang, et al. Standards Track [Page 11] RFC 8542 Data Model for DC Fabric Topology March 2019

     outside network.";
}
identity access {
  base fabric-port-role;
  description
    "The port is used for an endpoint to connect
     to a fabric.";
}
identity service-capability {
  description
    "Base for the service of the fabric ";
}
identity ip-mapping {
  base service-capability;
  description
    "NAT.";
}
identity acl-redirect {
  base service-capability;
  description
    "ACL redirect, which can provide a Service Function Chain (SFC).";
}
identity dynamic-route-exchange {
  base service-capability;
  description
    "Dynamic route exchange.";
}
/*
 * Typedefs
 */
typedef fabric-id {
  type nw:node-id;
  description
    "An identifier for a fabric in a topology.
     This identifier can be generated when composing a fabric.
     The composition of a fabric can be achieved by defining an
     RPC, which is left for vendor specific implementation
     and not provided in this model.";
}
typedef service-capabilities {

Zhuang, et al. Standards Track [Page 12] RFC 8542 Data Model for DC Fabric Topology March 2019

  type identityref {
    base service-capability;
  }
  description
    "Service capability of the fabric";
}
typedef port-type {
  type identityref {
    base port-type;
  }
  description
    "Port type: ethernet or serial or others.";
}
typedef bandwidth {
  type identityref {
    base bandwidth;
  }
  description
    "Bandwidth of the port.";
}
typedef node-ref {
  type instance-identifier;
  description
    "A reference to a node in topology";
}
typedef tp-ref {
  type instance-identifier;
  description
    "A reference to a termination point in topology";
}
typedef link-ref {
  type instance-identifier;
  description
    "A reference to a link in topology";
}
typedef underlay-network-type {
  type identityref {
    base fabric-type;
  }
  description
    "The type of physical network that implements
     this fabric.  Examples are VLAN and TRILL.";

Zhuang, et al. Standards Track [Page 13] RFC 8542 Data Model for DC Fabric Topology March 2019

}
typedef device-role {
  type identityref {
    base device-role;
  }
  description
    "Role of the device node.";
}
typedef fabric-port-role {
  type identityref {
    base fabric-port-role;
  }
  description
    "Role of the port in a fabric.";
}
typedef fabric-port-type {
  type enumeration {
    enum layer2interface {
      description
        "L2 interface";
    }
    enum layer3interface {
      description
        "L3 interface";
    }
    enum layer2Tunnel {
      description
        "L2 tunnel";
    }
    enum layer3Tunnel {
      description
        "L3 tunnel";
    }
  }
  description
    "Fabric port type";
}
grouping fabric-port {
  description
    "Attributes of a fabric port.";
  leaf name {
    type string;
    description
      "Name of the port.";

Zhuang, et al. Standards Track [Page 14] RFC 8542 Data Model for DC Fabric Topology March 2019

  }
  leaf role {
    type fabric-port-role;
    description
      "Role of the port in a fabric.";
  }
  leaf type {
    type fabric-port-type;
    description
      "Type of the port";
  }
  leaf device-port {
    type tp-ref;
    description
      "The device port it mapped to.";
  }
  choice tunnel-option {
    description
      "Tunnel options to connect two fabrics.
       It could be L2 Tunnel or L3 Tunnel.";
  }
}

}

<CODE ENDS>

 <CODE BEGINS> file "ietf-dc-fabric-topology@2019-02-25.yang"
 module ietf-dc-fabric-topology {
   yang-version 1.1;
   namespace "urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology";
   prefix fabric;
   import ietf-network {
     prefix nw;
     reference
       "RFC 8345: A YANG Data Model for Network Topologies";
   }
   import ietf-network-topology {
     prefix nt;
     reference
       "RFC 8345: A YANG Data Model for Network Topologies";
   }
   import ietf-dc-fabric-types {
     prefix fabrictypes;
     reference
       "RFC 8542: A YANG Data Model for Fabric Topology in
        Data-Center Networks";
   }

Zhuang, et al. Standards Track [Page 15] RFC 8542 Data Model for DC Fabric Topology March 2019

   organization
     "IETF I2RS (Interface to the Routing System) Working Group";
   contact
     "WG Web:    <https://datatracker.ietf.org/wg/i2rs/>
      WG List:   <mailto:i2rs@ietf.org>
      Editor:    Yan Zhuang
                 <mailto:zhuangyan.zhuang@huawei.com>
      Editor:    Danian Shi
                 <mailto:shidanian@huawei.com>";
   description
     "This module contains a collection of YANG definitions for
      fabric.
      Copyright (c) 2019 IETF Trust and the persons identified
      as authors of the code.  All rights reserved.
      Redistribution and use in source and binary forms, with
      or without modification, is permitted pursuant to, and
      subject to the license terms contained in, the Simplified
      BSD License set forth in Section 4.c of the IETF Trust's
      Legal Provisions Relating to IETF Documents
      (https://trustee.ietf.org/license-info).
      This version of this YANG module is part of RFC 8542;
      see the RFC itself for full legal notices.";
   revision 2019-02-25 {
     description
       "Initial revision.";
     reference
       "RFC 8542: A YANG Data Model for Fabric Topology
        in Data-Center Networks";
   }
   //grouping statements
   grouping fabric-network-type {
     description
       "Identify the topology type to be fabric.";
     container fabric-network {
       presence "indicates fabric Network";
       description
         "The presence of the container node indicates
          fabric topology";
     }
   }

Zhuang, et al. Standards Track [Page 16] RFC 8542 Data Model for DC Fabric Topology March 2019

   grouping fabric-options {
     description
       "Options for a fabric";
     leaf gateway-mode {
       type enumeration {
         enum centralized {
           description
             "The Fabric uses centralized
              gateway, in which gateway is deployed on SPINE
              node.";
         }
         enum distributed {
           description
             "The Fabric uses distributed
              gateway, in which gateway is deployed on LEAF
              node.";
         }
       }
       default "distributed";
       description
         "Gateway mode of the fabric";
     }
     leaf traffic-behavior {
       type enumeration {
         enum normal {
           description
             "Normal means no policy is needed
              for all traffic";
         }
         enum policy-driven {
           description
             "Policy driven means policy is
              needed for the traffic; otherwise, the traffic
              will be discarded.";
         }
       }
       default "normal";
       description
         "Traffic behavior of the fabric";
     }
     leaf-list capability-supported {
       type fabrictypes:service-capabilities;
       description
         "It provides a list of supported services of the
          fabric.  The service-capabilities is defined as
          identity-ref.  Users can define more services
          by defining new identities.";
     }

Zhuang, et al. Standards Track [Page 17] RFC 8542 Data Model for DC Fabric Topology March 2019

   }
   grouping device-attributes {
     description
       "device attributes";
     leaf device-ref {
       type fabrictypes:node-ref;
       description
         "The device that the fabric includes that refers
          to a node in another topology.";
     }
     leaf-list role {
       type fabrictypes:device-role;
       default "fabrictypes:leaf";
       description
         "It is a list of device roles to represent the roles
          that a device plays within a POD, such as SPINE,
          LEAF, Border, or Border-Leaf.
          The device role is defined as identity-ref.  If more
          than 2 stages are used for a POD, users can
          define new identities for the device role.";
     }
   }
   grouping link-attributes {
     description
       "Link attributes";
     leaf link-ref {
       type fabrictypes:link-ref;
       description
         "The link that the fabric includes that refers to
          a link in another topology.";
     }
   }
   grouping port-attributes {
     description
       "Port attributes";
     leaf port-ref {
       type fabrictypes:tp-ref;
       description
         "The port that the fabric includes that refers to
          a termination-point in another topology.";
     }
     leaf port-type {
       type fabrictypes:port-type;
       description
         "Port type is defined as identity-ref.  The current

Zhuang, et al. Standards Track [Page 18] RFC 8542 Data Model for DC Fabric Topology March 2019

          types include ethernet or serial.  If more types
          are needed, developers can define new identities.";
     }
     leaf bandwidth {
       type fabrictypes:bandwidth;
       description
         "Bandwidth of the port.  It is defined as identity-ref.
          If more speeds are introduced, developers can define
          new identities for them.  Current speeds include 1M, 10M,
          100M, 1G, 10G, 25G, 40G, 100G, and 400G.";
     }
   }
   grouping fabric-attributes {
     description
       "Attributes of a fabric";
     leaf fabric-id {
       type fabrictypes:fabric-id;
       description
         "An identifier for a fabric in a topology.
          This identifier can be generated when composing a fabric.
          The composition of a fabric can be achieved by defining an
          RPC, which is left for vendor-specific implementation and
          not provided in this model.";
     }
     leaf name {
       type string;
       description
         "Name of the fabric";
     }
     leaf type {
       type fabrictypes:underlay-network-type;
       description
         "The type of physical network that implements this
          fabric.  Examples are VLAN and TRILL.";
     }
     container vni-capacity {
       description
         "The range of the VXLAN Network Identifier
          (VNI) defined in RFC 7348 that the POD uses.";
       leaf min {
         type int32;
         description
           "The lower-limit VNI.";
       }
       leaf max {
         type int32;
         description

Zhuang, et al. Standards Track [Page 19] RFC 8542 Data Model for DC Fabric Topology March 2019

           "The upper-limit VNI.";
       }
     }
     leaf description {
       type string;
       description
         "Description of the fabric";
     }
     container options {
       description
         "Options of the fabric";
       uses fabric-options;
     }
     list device-nodes {
       key "device-ref";
       description
         "Device nodes that are included in a fabric.";
       uses device-attributes;
     }
     list device-links {
       key "link-ref";
       description
         "Links that are included within a fabric.";
       uses link-attributes;
     }
     list device-ports {
       key "port-ref";
       description
         "Ports that are included in the fabric.";
       uses port-attributes;
     }
   }
   // augment statements
   augment "/nw:networks/nw:network/nw:network-types" {
     description
       "Introduce a new network type for fabric-based topology";
     uses fabric-network-type;
   }
   augment "/nw:networks/nw:network/nw:node" {
     when '/nw:networks/nw:network/nw:network-types/'
        + 'fabric:fabric-network' {
       description
         "Augmentation parameters apply only for networks
          with fabric topology";
     }

Zhuang, et al. Standards Track [Page 20] RFC 8542 Data Model for DC Fabric Topology March 2019

     description
       "Augmentation for fabric nodes created by
        fabric topology.";
     container fabric-attributes {
       description
         "Attributes for a fabric network";
       uses fabric-attributes;
     }
   }
   augment "/nw:networks/nw:network/nw:node/nt:termination-point" {
     when '/nw:networks/nw:network/nw:network-types/'
        + 'fabric:fabric-network' {
       description
         "Augmentation parameters apply only for networks
          with fabric topology";
     }
     description
       "Augmentation for port on fabric.";
     container fport-attributes {
       config false;
       description
         "Attributes for fabric ports";
       uses fabrictypes:fabric-port;
     }
   }
 }
 <CODE ENDS>

5. IANA Considerations

 This document registers the following namespace URIs in the "IETF XML
 Registry" [RFC3688]:
 URI:urn:ietf:params:xml:ns:yang:ietf-dc-fabric-types
 Registrant Contact: The IESG.
 XML: N/A; the requested URI is an XML namespace.
 URI:urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology
 Registrant Contact: The IESG.
 XML: N/A; the requested URI is an XML namespace.
 URI:urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology-state
 Registrant Contact: The IESG.
 XML: N/A; the requested URI is an XML namespace.

Zhuang, et al. Standards Track [Page 21] RFC 8542 Data Model for DC Fabric Topology March 2019

 This document registers the following YANG modules in the "YANG
 Module Names" registry [RFC6020]:
 Name: ietf-dc-fabric-types
 Namespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-types
 Prefix: fabrictypes
 Reference: RFC 8542
 Name: ietf-dc-fabric-topology
 Namespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology
 Prefix: fabric
 Reference: RFC 8542
 Name: ietf-dc-fabric-topology-state
 Namespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology-state
 Prefix: sfabric
 Reference: RFC 8542

6. Security Considerations

 The YANG module defined in this document is designed to be accessed
 via network management protocols such as NETCONF [RFC6241] or
 RESTCONF [RFC8040].  The lowest NETCONF layer is the secure transport
 layer, and the mandatory-to-implement secure transport is Secure
 Shell (SSH) [RFC6242].  The lowest RESTCONF layer is HTTPS, and the
 mandatory-to-implement secure transport is TLS [RFC8446].
 The Network Configuration Access Control Model (NACM) [RFC8341]
 provides the means to restrict access for particular NETCONF or
 RESTCONF users to a preconfigured subset of all available NETCONF or
 RESTCONF protocol operations and content.
 There are a number of data nodes defined in this YANG module that are
 writable/creatable/deletable (i.e., config true, which is the
 default).  These data nodes may be considered sensitive or vulnerable
 in some network environments.  Write operations (e.g., edit-config)
 to these data nodes without proper protection can have a negative
 effect on network operations.  The subtrees and data nodes and their
 sensitivity/vulnerability in the ietf-dc-fabric-topology module are
 as follows:
 fabric-attributes: A malicious client could attempt to sabotage the
 configuration of important fabric attributes, such as device nodes or
 type.
 Some of the readable data nodes in this YANG module may be considered
 sensitive or vulnerable in some network environments.  It is thus
 important to control read access (e.g., via get, get-config, or

Zhuang, et al. Standards Track [Page 22] RFC 8542 Data Model for DC Fabric Topology March 2019

 notification) to these data nodes.  The subtrees and data nodes and
 their sensitivity/vulnerability in the ietf-dc-fabric-topology module
 are as follows:
 fport-attributes: A malicious client could attempt to read the
 connections of fabrics without permission, such as device-port and
 name.

7. References

7.1. Normative References

 [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>.
 [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
            DOI 10.17487/RFC3688, January 2004,
            <https://www.rfc-editor.org/info/rfc3688>.
 [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
            the Network Configuration Protocol (NETCONF)", RFC 6020,
            DOI 10.17487/RFC6020, October 2010,
            <https://www.rfc-editor.org/info/rfc6020>.
 [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
            and A. Bierman, Ed., "Network Configuration Protocol
            (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
            <https://www.rfc-editor.org/info/rfc6241>.
 [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
            Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
            <https://www.rfc-editor.org/info/rfc6242>.
 [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
            RFC 7950, DOI 10.17487/RFC7950, August 2016,
            <https://www.rfc-editor.org/info/rfc7950>.
 [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
            Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
            <https://www.rfc-editor.org/info/rfc8040>.
 [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
            2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
            May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Zhuang, et al. Standards Track [Page 23] RFC 8542 Data Model for DC Fabric Topology March 2019

 [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
            Access Control Model", STD 91, RFC 8341,
            DOI 10.17487/RFC8341, March 2018,
            <https://www.rfc-editor.org/info/rfc8341>.
 [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
            and R. Wilton, "Network Management Datastore Architecture
            (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
            <https://www.rfc-editor.org/info/rfc8342>.
 [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
            Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
            Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
            2018, <https://www.rfc-editor.org/info/rfc8345>.
 [RFC8346]  Clemm, A., Medved, J., Varga, R., Liu, X.,
            Ananthakrishnan, H., and N. Bahadur, "A YANG Data Model
            for Layer 3 Topologies", RFC 8346, DOI 10.17487/RFC8346,
            March 2018, <https://www.rfc-editor.org/info/rfc8346>.
 [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
            Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
            <https://www.rfc-editor.org/info/rfc8446>.

7.2. Informative References

 [GENEVE]   Gross, J., Ganga, I., and T. Sridhar, "Geneve: Generic
            Network Virtualization Encapsulation", Work in Progress,
            draft-ietf-nvo3-geneve-12, March 2019.
 [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
            L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
            eXtensible Local Area Network (VXLAN): A Framework for
            Overlaying Virtualized Layer 2 Networks over Layer 3
            Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
            <https://www.rfc-editor.org/info/rfc7348>.
 [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
            BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
            <https://www.rfc-editor.org/info/rfc8340>.
 [RFC8344]  Bjorklund, M., "A YANG Data Model for IP Management",
            RFC 8344, DOI 10.17487/RFC8344, March 2018,
            <https://www.rfc-editor.org/info/rfc8344>.

Zhuang, et al. Standards Track [Page 24] RFC 8542 Data Model for DC Fabric Topology March 2019

Appendix A. Non-NMDA-State Modules

 The YANG module, ietf-dc-fabric-topology, defined in this document
 augments two modules, ietf-network and ietf-network-topology, that
 are designed to be used in conjunction with implementations that
 support the Network Management Datastore Architecture (NMDA) defined
 in [RFC8342].  In order to allow implementations to use the model
 even in cases when NMDA is not supported, a set of companion modules
 have been defined that represent a state model of networks and
 network topologies: ietf-network-state and ietf-network-topology-
 state, respectively.
 In order to be able to use the model for fabric topologies defined in
 this document in conjunction with non-NMDA-compliant implementations,
 a corresponding companion module needs to be introduced as well.
 This companion module, ietf-dc-fabric-topology-state, mirrors ietf-
 dc-fabric-topology.  However, the ietf-dc-fabric-topology-state
 module augments ietf-network-state (instead of ietf-network and ietf-
 network-topology), and all of its data nodes are non-configurable.
 Like ietf-network-state and ietf-network-topology-state, ietf-dc-
 fabric-topology-state SHOULD NOT be supported by implementations that
 support NMDA.  It is for this reason that the module is defined in
 the Appendix.
 The definition of the module follows.  As the structure of the module
 mirrors that of its underlying module, the YANG tree is not depicted
 separately.

<CODE BEGINS> file "ietf-dc-fabric-topology-state@2019-02-25.yang" module ietf-dc-fabric-topology-state {

yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology-state";
prefix sfabric;
import ietf-network-state {
  prefix nws;
  reference
    "RFC 8345: A Data Model for Network Topologies";
}
import ietf-dc-fabric-types {
  prefix fabrictypes;
  reference
    "RFC 8542: A YANG Data Model for Fabric Topology in
     Data-Center Networks";
}
organization

Zhuang, et al. Standards Track [Page 25] RFC 8542 Data Model for DC Fabric Topology March 2019

  "IETF I2RS (Interface to the Routing System) Working Group";
contact
  "WG Web:    <https://datatracker.ietf.org/wg/i2rs/>
   WG List:   <mailto:i2rs@ietf.org>
   Editor:    Yan Zhuang
              <mailto:zhuangyan.zhuang@huawei.com>
   Editor:    Danian Shi
              <mailto:shidanian@huawei.com>";
description
  "This module contains a collection of YANG definitions for
   fabric state, representing topology that either is learned
   or results from applying topology that has been
   configured per the ietf-dc-fabric-topology model, mirroring
   the corresponding data nodes in this model.
   This model mirrors the configuration tree of ietf-dc-fabric
   -topology but contains only read-only state data.  The model
   is not needed when the implementation infrastructure supports
   the Network Management Datastore Architecture (NMDA).
   Copyright (c) 2019 IETF Trust and the persons identified as
   authors of the code.  All rights reserved.
   Redistribution and use in source and binary forms, with or
   without modification, is permitted pursuant to, and subject
   to the license terms contained in, the Simplified BSD
   License set forth in Section 4.c of the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info).
   This version of this YANG module is part of RFC 8542;
   see the RFC itself for full legal notices.";
revision 2019-02-25 {
  description
    "Initial revision.";
  reference
    "RFC 8542: A YANG Data Model for Fabric Topology in
     Data-Center Networks";
}
//grouping statements
grouping fabric-network-type {
  description
    "Identify the topology type to be fabric.";

Zhuang, et al. Standards Track [Page 26] RFC 8542 Data Model for DC Fabric Topology March 2019

  container fabric-network {
    presence "indicates fabric Network";
    description
      "The presence of the container node indicates
       fabric topology";
  }
}
grouping fabric-options {
  description
    "Options for a fabric";
  leaf gateway-mode {
    type enumeration {
      enum centralized {
        description
          "The fabric uses centralized
           gateway, in which gateway is deployed on SPINE
           node.";
      }
      enum distributed {
        description
          "The fabric uses distributed
           gateway, in which gateway is deployed on LEAF
           node.";
      }
    }
    default "distributed";
    description
      "Gateway mode of the fabric";
  }
  leaf traffic-behavior {
    type enumeration {
      enum normal {
        description
          "Normal means no policy is needed
           for all traffic";
      }
      enum policy-driven {
        description
          "Policy driven means policy is
           needed for the traffic; otherwise, the traffic
           will be discarded.";
      }
    }
    default "normal";
    description
      "Traffic behavior of the fabric";
  }

Zhuang, et al. Standards Track [Page 27] RFC 8542 Data Model for DC Fabric Topology March 2019

  leaf-list capability-supported {
    type fabrictypes:service-capabilities;
    description
      "It provides a list of supported services of the
       fabric.  The service-capabilities is defined as
       identity-ref.  Users can define more services
       by defining new identities.";
  }
}
grouping device-attributes {
  description
    "device attributes";
  leaf device-ref {
    type fabrictypes:node-ref;
    description
      "The device that the fabric includes that refers
       to a node in another topology.";
  }
  leaf-list role {
    type fabrictypes:device-role;
    default "fabrictypes:leaf";
    description
      "It is a list of device roles to represent the roles
       that a device plays within a POD, such as SPINE,
       LEAF, Border, or Border-Leaf.
       The device role is defined as identity-ref.  If more
       than 2 stages are used for a POD, users can
       define new identities for the device role.";
  }
}
grouping link-attributes {
  description
    "Link attributes";
  leaf link-ref {
    type fabrictypes:link-ref;
    description
      "The link that the fabric includes that refers to
       a link in another topology.";
  }
}
grouping port-attributes {
  description
    "Port attributes";
  leaf port-ref {
    type fabrictypes:tp-ref;

Zhuang, et al. Standards Track [Page 28] RFC 8542 Data Model for DC Fabric Topology March 2019

    description
      "The port that the fabric includes that refers to
       a termination-point in another topology.";
  }
  leaf port-type {
    type fabrictypes:port-type;
    description
      "Port type is defined as identity-ref.  The current
       types include ethernet or serial.  If more types
       are needed, developers can define new identities.";
  }
  leaf bandwidth {
    type fabrictypes:bandwidth;
    description
      "Bandwidth of the port.  It is defined as
       identity-ref.  If more speeds are introduced,
       developers can define new identities for them.  Current
       speeds include 1M, 10M, 100M, 1G, 10G,
       25G, 40G, 100G, and 400G.";
  }
}
grouping fabric-attributes {
  description
    "Attributes of a fabric";
  leaf fabric-id {
    type fabrictypes:fabric-id;
    description
      "Fabric ID";
  }
  leaf name {
    type string;
    description
      "Name of the fabric";
  }
  leaf type {
    type fabrictypes:underlay-network-type;
    description
      "The type of physical network that implements this
       fabric.  Examples are VLAN and TRILL.";
  }
  container vni-capacity {
    description
      "The range of the VXLAN Network
       Identifier (VNI) defined in RFC 7348 that the POD uses.";
    leaf min {
      type int32;
      description

Zhuang, et al. Standards Track [Page 29] RFC 8542 Data Model for DC Fabric Topology March 2019

        "The lower-limit VNI.";
    }
    leaf max {
      type int32;
      description
        "The upper-limit VNI.";
    }
  }
  leaf description {
    type string;
    description
      "Description of the fabric";
  }
  container options {
    description
      "Options of the fabric";
    uses fabric-options;
  }
  list device-nodes {
    key "device-ref";
    description
      "Device nodes that are included in a fabric.";
    uses device-attributes;
  }
  list device-links {
    key "link-ref";
    description
      "Links that are included within a fabric.";
    uses link-attributes;
  }
  list device-ports {
    key "port-ref";
    description
      "Ports that are included in the fabric.";
    uses port-attributes;
  }
}
// augment statements
augment "/nws:networks/nws:network/nws:network-types" {
  description
    "Introduce a new network type for fabric-based logical
     topology";
  uses fabric-network-type;
}

Zhuang, et al. Standards Track [Page 30] RFC 8542 Data Model for DC Fabric Topology March 2019

augment "/nws:networks/nws:network/nws:node" {
  when '/nws:networks/nws:network/nws:network-types'
     + '/sfabric:fabric-network' {
    description
      "Augmentation parameters apply only for
       networks with fabric topology.";
  }
  description
    "Augmentation for fabric nodes.";
  container fabric-attributes-state {
    description
      "Attributes for a fabric network";
    uses fabric-attributes;
  }
}

} <CODE ENDS>

Zhuang, et al. Standards Track [Page 31] RFC 8542 Data Model for DC Fabric Topology March 2019

Acknowledgements

 We wish to acknowledge the helpful contributions, comments, and
 suggestions that were received from Alexander Clemm, Donald E.
 Eastlake 3rd, Xufeng Liu, Susan Hares, Wei Song, Luis M. Contreras,
 and Benoit Claise.

Authors' Addresses

 Yan Zhuang
 Huawei
 101 Software Avenue, Yuhua District
 Nanjing, Jiangsu  210012
 China
 Email: zhuangyan.zhuang@huawei.com
 Danian Shi
 Huawei
 101 Software Avenue, Yuhua District
 Nanjing, Jiangsu  210012
 China
 Email: shidanian@huawei.com
 Rong Gu
 China Mobile
 32 Xuanwumen West Ave, Xicheng District
 Beijing, Beijing  100053
 China
 Email: gurong_cmcc@outlook.com
 Hariharan Ananthakrishnan
 Netflix
 Email: hari@netflix.com

Zhuang, et al. Standards Track [Page 32]

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