A YANG Data Model for Border Gateway Protocol (BGP) Topology

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Table of Contents

1. Introduction

Network operators perform the capacity planning for their networks and run regular what-if scenarios analysis based on representations of the real network. Those what-if analysis and capacity planning processes require, among other information, a topological view (domains, nodes, links, network interconnection) of the deployed network.¶

This document defines a YANG data model representing an abstracted view of a network topology containing Border Gateway Protocol (BGP) with the following assumption: * Areas can be explicit, depending on which IGP protocol is used. + Metrics can be provided to the operations team for greater control of the network. - A view of the topology of the network built on the basis of the neighbors can be presented.¶

This YANG data model can be used to export the BGP related topology directly from a network controller to Operation Support System (OSS) tools or to a higher level controller.¶

This document defines a YANG data model for representing, managing and controlling the BGP topology. The data model augments ietf-network module [RFC8345] by adding the BGP information.¶

This document explains the scope and purpose of the BGP topology model and how the topology and service models fit together.¶

The YANG data model defined in this document conforms to the Network Management Datastore Architecture [RFC8342].¶

2. Use Cases

Use cases for this document are the same than explained in [I-D.draft-ogondio-nmop-isis-topology]. Here are included for completeness and discussion. Future versions may consider removing them.¶

This information is required in the IP/MPLS planning process to properly assess the required network resources to meet the traffic demands in normal and failure scenarios. Network operators perform the capacity planning for their networks and run regular what-if scenarios analysis based on representations of the real network. Those what-if analysis and capacity planning processes require, among other information, a topological view (domains, nodes, links, network interconnection) of the deployed network.¶

The standardization of an abstracted view of the BGP topology model as NorthBound Interface (NBI) of Software Defined Networking (SDN) controllers allows the unified query of the BGP topology in order to inject this information into third party tools covering specialized cases.¶

The BGP topological model should export enough BGP information to permit these tools to simulate the IP routing. By mapping the traffic demand, ideally at the IP flow level, to the topology, we can simulate the traffic growth, evaluating this way its effect on the routing and quality of service. That is, simulating how IP-level traffic demands would be forwarded, after BGP convergence is reached, and from there estimating, using appropriate mathematical models, related KPIs like the occupation in the links or end-to-end latencies.¶

In summary, the network-wide view of the BGP topology enables multiple use cases:¶

• Network design: verifying that the actual deployed BGP network conforms to the planned design.¶

• Capacity planning. Dimensioning or redesign of the IP infrastructure to satisfy target KPI metrics under existing or forecasted traffic demands.¶

• What-if analysis. Estimation of the network KPIs in modified network situations. For instance, failure situations, traffic anomaly situations, addition or deletion of new adjacencies, IGP weight reconfigurations, etc.¶

• Failure analysis. Systematic and massive test of the network under multiple simulated failure situations, evaluating the network fault tolerance properties, and using mathematical models to derive statistical network availability metrics.¶

3. Description of the YANG Data Model for BGP Topology

The abstract (base) network data model is defined in the "ietf-network" module of [RFC8345]. The BGP-topology builds on the network data model defined in the "ietf-network" module [RFC8345], augmenting the nodes with BGP information, which anchor the links and are contained in nodes.¶

There is a set of parameters and augmentations that are included at the node level. Each parameter and description are detailed following:¶

• Network-types /restconf/data/ietf-network:networks/network/network-types: Its presence identifies the BGP topology type. Thus, the network type MUST be bgp-topology.¶

• Local-as /restconf/data/ietf-networks/network/node/l3t:l3-node-attributes/bgp:local-as: Identifies the Local-AS configured in the Network-Element.¶

• Neighbors /restconf/data/ietf-network:networks/network/node/l3t:l3-node-attributes/bgp:neighbours: list of Neighbors of the Node. Each Neighbor has the same set of parameters to describe the BGP session.¶

• Neighbour neighbour is identified by the IP address. Description for troubleshooting purposes.¶

• Peer-As attributes/bgp:neighbours/bgp:peer-as: Autonomous System of the peer. In case of iBGP sessions the Local -As and Peer-As is the same.¶

• Address-Family: Address Families shared by the nodes in the session. This is a leaf-list, because more than one AFI + SAFI address family can be shared. The options are alligned to the ones available in the IETF-BGP-TYPES (ipv4-unicast, ipv6-unicast, ipv4-labeled-unicast, ...)¶

The following figure is based on the Figure 1 from [RFC8346], where the example-bgp-topology is replaced with ietf-l3-bgp-topology and where arrows show how the modules augment each other.¶

                      +-----------------------------+
                      |  +-----------------------+  |
                      |  |      ietf-network     |  |
                      |  +----------^------------+  |
                      |             |               |
                      |  +-----------------------+  |
                      |  | ietf-network-topology |  |
                      |  +----------+------------+  |
                      +-------------^---------------+
                                    |
                                    |
                       +------------^-------------+
                       | ietf-l3-unicast-topology |
                       +------------^-------------+
                                    |
                                    |
                        +-----------^-----------+
                        | ietf-l3-bgp-topology  |
                        +-----------------------+

4. BGP Topology Tree Diagram

Figure 2 below shows the tree diagram of the YANG data model defined in module ietf-l3-bgp-topology.yang (Figure 3).¶

module: ietf-l3-bgp-topology
  augment /nw:networks/nw:network/nw:network-types:
    +--rw bgp-topology!
  augment /nw:networks/nw:network/nw:node/l3t:l3-node-attributes:
    +--rw local-as?     uint32
    +--rw neighbours
       +--rw neighbor?         inet:ip-address
       +--rw description?      string
       +--rw peer-as?          uint32
       +--rw address-family*   identityref

5. YANG Model for BGP topology

This module imports types from [RFC8343] and [RFC8345].¶

<CODE BEGINS> file "ietf-l3-bgp-topology@2024-07-23.yang"

module ietf-l3-bgp-topology {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-l3-bgp-topology";
  prefix "bgpnt";
  import ietf-yang-types {
          prefix "yang";
      }
  import ietf-network {
    prefix "nw";
  }
  import ietf-l3-unicast-topology {
    prefix "l3t";
  }
  import ietf-inet-types {
    prefix "inet";
  }
  organization
    "IETF NMOP (Network Management Operations) Working Group";
  contact
    "WG Web:  <https://datatracker.ietf.org/wg/nmop/>
    WG List:  <mailto:nmop@ietf.org>

    Editor:   Oscar Gonzalez de Dios
              <mailto:oscar.gonzalezdedios@telefonica.com>
    Editor:   Samier Barguil
              <mailto:samier.barguil_giraldo@nokia.com>
    Editor:   Victor Lopez
              <mailto:victor.lopez@nokia.com>";
  description
    "This module defines a model for Layer 3 BGP
     topologies.

    Copyright (c) 2024 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 Revised 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 XXXX
     (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
     for full legal notices.";

  revision 2024-07-23 {
    description
      "Initial version";
    reference
      "RFC XXXX: A YANG Data Model for Border Gateway Protocol (BGP) Topology";
  }

  typedef area-id-type {
    type yang:dotted-quad;
    description
      "Area ID type";
  }

  identity afi-safi-type {
    description
      "Base identity type for AFI,SAFI tuples for BGP-4";
    reference
      "RFC4760: Multi-protocol extensions for BGP-4";
  }

  identity ipv4-unicast {
    base afi-safi-type;
    description
      "IPv4 unicast (AFI,SAFI = 1,1)";
    reference
      "RFC4760: Multi-protocol extensions for BGP-4";
  }

  identity ipv6-unicast {
    base afi-safi-type;
    description
      "IPv6 unicast (AFI,SAFI = 2,1)";
    reference
      "RFC4760: Multi-protocol extensions for BGP-4";
  }

  identity ipv4-labeled-unicast {
    base afi-safi-type;
    description
      "Labeled IPv4 unicast (AFI,SAFI = 1,4)";
    reference
      "RFC 3107: Carrying Label Information in BGP-4.";
  }

  identity ipv6-labeled-unicast {
    base afi-safi-type;
    description
      "Labeled IPv6 unicast (AFI,SAFI = 2,4)";
    reference
      "RFC 3107: Carrying Label Information in BGP-4";
  }

  identity l3vpn-ipv4-unicast {
    base afi-safi-type;
    description
      "Unicast IPv4 MPLS L3VPN (AFI,SAFI = 1,128)";
    reference
      "RFC 4364: BGP/MPLS IP Virtual Private Networks (VPNs)";
  }

  identity l3vpn-ipv6-unicast {
    base afi-safi-type;
    description
      "Unicast IPv6 MPLS L3VPN (AFI,SAFI = 2,128)";
    reference
      "RFC 4659: BGP-MPLS IP Virtual Private Network (VPN) Extension
                 for IPv6 VPN";
  }
  identity l3vpn-ipv4-multicast {
    base afi-safi-type;
    description
      "Multicast IPv4 MPLS L3VPN (AFI,SAFI = 1,129)";
    reference
      "RFC 6514: BGP Encodings and Procedures for Multicast in MPLS/BGP
       IP VPNs.";
  }

  identity l3vpn-ipv6-multicast {
    base afi-safi-type;
    description
      "Multicast IPv6 MPLS L3VPN (AFI,SAFI = 2,129)";
    reference
      "RFC 6514: BGP Encodings and Procedures for Multicast in
                 MPLS/BGP IP VPNs.";
  }

  identity l2vpn-vpls {
    base afi-safi-type;
    description
      "BGP-signalled VPLS (AFI,SAFI = 25,65)";
    reference
      "RFC 4761: Virtual Private LAN Service (VPLS) Using BGP for
                 Auto-Discovery and Signaling.";
  }

  identity l2vpn-evpn {
    base afi-safi-type;
    description
      "BGP MPLS Based Ethernet VPN (AFI,SAFI = 25,70)";
    reference
      "RFC 7432: BGP MPLS-Based Ethernet VPN";
  }

  grouping bgp-topology-type {
    description "Identifies the topology type to be BGP.";
    container bgp-topology {
      presence "Indicates BGP topology";
      description
        "The presence of the container node indicates BGP
        topology";
    }
  }

  grouping bgp-node-attributes {
    description "BGP node scope attributes";
    leaf local-as {
        type uint32;
        description
          "Local Autonomous System (AS) number";
    }
    container neighbours {
      description
        "Contains node timer attributes";
      leaf neighbor {
        type inet:ip-address;
        description
          "Neighbor IP address";
      }
      leaf description {
        type string;
        description
          "Neighbor description";;
      }
      leaf peer-as {
        type uint32;
        description
          "Peer autonomous system (AS) number";
      }
      leaf-list address-family {
        type identityref {
          base afi-safi-type;
        }
        description
          "Address Family type";
      }
    }
  }

  augment "/nw:networks/nw:network/nw:network-types" {
    description
      "Introduces new network type for L3 Unicast topology";
    uses bgp-topology-type;
  }

  augment "/nw:networks/nw:network/nw:node/l3t:l3-node-attributes" {
    when "/nw:networks/nw:network/nw:network-types/bgp:bgp-topology" {
      description
        "Augmentation parameters apply only for networks with
        BGP topology";
    }
    description
        "BGP node-level attributes ";
    uses bgp-node-attributes;
  }
}
<CODE ENDS>

6. Security Considerations

The YANG module specified in this document defines a schema for data that 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.¶

7. IANA Considerations

This document registers the following namespace URIs in the IETF XML registry [RFC3688]:¶

--------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-l3-bgp-topology
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
--------------------------------------------------------------------

This document registers the following YANG module in the YANG Module Names registry [RFC6020]:¶

--------------------------------------------------------------------
name:         ietf-l3-bgp-topology
namespace:    urn:ietf:params:xml:ns:yang:ietf-l3-bgp-topology
maintained by IANA: N
prefix:       ietf-l3-bgp-topology
reference:    RFC XXXX
--------------------------------------------------------------------

8. Implementation Status

This section will be used to track the status of the implementations of the model. It is aimed at being removed if the document becomes RFC.¶

9. References

Acknowledgments

The authors of this document would like to thank XXX.¶

Authors' Addresses