A Yang Data Model for OAM and Management of ALTO Protocol

Internet-Draft	ALTO O&M YANG	October 2022
Zhang, et al.	Expires 27 April 2023	[Page]

Abstract

This document defines a YANG data model for Operations, Administration, and Maintenance (OAM) & Management of Application-Layer Traffic Optimization (ALTO) Protocol. The operator can use the data model to create and update ALTO information resources, manage the access control, configure server-to-server communication and server discovery, and collect statistical data.¶

Table 1: Prefixes and corresponding YANG modules
Prefix	YANG module	Reference
yang	ietf-yang-types	[RFC6991]
inet	ietf-inet-types	[RFC6991]
key-chain	ietf-key-chain	[RFC8177]
tcp	ietf-tcp-server	[I-D.ietf-netconf-tcp-client-server]
tls	ietf-tls-server	[I-D.ietf-netconf-tls-client-server]
http	ietf-http-server	[I-D.ietf-netconf-http-client-server]

Table 2: Basic Requirements of Data Model for ALTO O&M.
Requirement	Reference
R1: The data model should support configuration for ALTO server setup.	Section 16.1 of [RFC7285]
R2: The data model should provide logging management.	Section 16.2.1 of [RFC7285]
R3: The data model should provide ALTO-related management information.	Section 16.2.2 of [RFC7285]
R4: The data model should support configuration for security policy management.	Section 16.2.6 of [RFC7285]
R5-1: The data model should support configuration for different data sources.	Section 16.2.4 of [RFC7285], Section 3.2 of [RFC7971]
R5-2: The data model should support configuration for information resource generation algorithms.	Section 16.2.4 of [RFC7285]
R5-3: The data model should support configuration for access control at information resource level.	Section 16.2.4 of [RFC7285]
R6: The data model should provide metrics for server failures.	Section 16.2.3 of [RFC7285], Section 3.3 of [RFC7971]
R7: The data model should provide performance monitoring for ALTO-specific metrics.	Section 16.2.5 of [RFC7285], Section 3.4 of [RFC7971]

5. Design of ALTO O&M Data Model

5.1. Overview of ALTO O&M Data Model

The ietf-alto module defined in this document provide all the basic ALTO O&M data models fitting the requirements listed in Section 4.¶

The container "alto-server" in the ietf-alto module contains all the configured and operational parameters of the adminstrated ALTO server instance.¶

module: ietf-alto
  +--rw alto-server
     +--rw listen
     |  +---u alto-server-listen-stack-grouping
     +--rw server-discovery
     |  +---u alto-server-discovery-grouping
     +--rw logging-system
     |  +---u alto-logging-system-grouping
     +--rw cost-type* [cost-type-name]
     |  +--rw cost-type-name    string
     |  +--rw cost-mode         identityref
     |  +--rw cost-metric       identityref
     +--rw meta* [meta-key]
     |  +--rw meta-key      string
     |  +--rw meta-value    string
     +--rw data-source* [source-id]
     |  +--rw source-id              string
     |  +--rw source-type            identityref
     |  +--rw (update-policy)
     |  |  +--:(reactive)
     |  |  |  +--rw reactive         boolean
     |  |  +--:(proactive)
     |  |     +--rw poll-interval    uint32
     |  +--rw (source-params)?
     +--rw resource* [resource-id]
        +--rw resource-id                       resource-id
        +--rw resource-type                     identityref
        +--rw description?                      string
        +--rw accepted-group*                   string
        +--rw dependency*
        |       -> /alto-server/resource/resource-id
        +--rw auth
        |  +--rw (auth-type-selection)?
        |     +--:(auth-key-chain)
        |     |  +--rw key-chain?   key-chain:key-chain-ref
        |     +--:(auth-key)
        |     +--:(auth-tls)
        +--rw (resource-params)?
           +--:(ird)
           |  +--rw alto-ird-params
           |     +--rw delegation    inet:uri
           +--:(networkmap)
           |  +--rw alto-networkmap-params
           |     +--rw is-default?   boolean
           |     +--rw filtered?     boolean
           |     +---u algorithm
           +--:(costmap)
           |  +--rw alto-costmap-params
           |     +--rw filtered?             boolean
           |     +---u filter-costmap-cap
           |     +---u algorithm
           +--:(endpointcost)
           |  +--rw alto-endpointcost-params
           |     +---u endpoint-cost-cap
           |     +---u algorithm
           +--:(endpointprop)
           |  +--rw alto-endpointprop-params
           |     +--rw prop-types*   string
           |     +---u algorithm
           +--:(propmap) {propmap}?
           |  +--rw alto-propmap-params
           |     +---u algorithm
           +--:(cdni) {cdni}?
           |  +--rw alto-cdni-params
           |     +---u algorithm
           +--:(update) {incr-update}?
              +--rw alto-update-params
                 +---u algorithm

5.2. Data Model for Server-level Operation and Management

The ALTO server instance contains the following configuration parameters for server-level operation and management for ALTO, which satisfies R1 - R4 in Section 4.2.¶

module: ietf-alto
  +--rw alto-server
     +--rw listen
     |  +---u alto-server-listen-stack-grouping
     +--rw server-discovery
     |  +---u alto-server-discovery-grouping
     +--rw logging-system
     |  +---u alto-logging-system-grouping
     +--rw cost-type* [cost-type-name]
     |  +--rw cost-type-name    string
     |  +--rw cost-mode         identityref
     |  +--rw cost-metric       identityref
     +--rw meta* [meta-key]
     |  +--rw meta-key      string
     |  +--rw meta-value    string
     ...

5.2.1. Data Model for ALTO Server Setup

To satisfy R1 in Section 4.2, the ALTO server instance contains the following basic configurations for the server setup.¶

5.2.1.1. ALTO Server Listen Stack

The "listen" contains all the configurations for the whole server listen stack across HTTP layer, TLS layer and TCP layer.¶

  grouping alto-server-grouping:
    +-- base-uri?   inet:uri
  grouping alto-server-listen-stack-grouping
    +-- (transport)
       +--:(http) {http-listen}?
       |  +-- http
       |     +-- tcp-server-parameters
       |     |  +---u tcp:tcp-server-grouping
       |     +-- http-server-parameters
       |     |  +---u http:http-server-grouping
       |     +-- alto-server-parameters
       +--:(https)
          +-- https
             +-- tcp-server-parameters
                +---u tcp:tcp-server-grouping
                +-- tls-server-parameters
                |  +---u tls:tls-server-grouping
                +-- http-server-parameters
                |  +---u http:http-server-grouping
                +-- alto-server-parameters

5.2.1.2. ALTO Server Discovery Setup

In practice, multiple ALTO servers can be deployed for scalability. That may require communication among different ALTO servers.¶

The YANG module defined in this document does not contain any configuration for the communication between two ALTO servers. Instead, it provides the configuration for how an ALTO server can be discovered by another ALTO server on demand.¶

  grouping alto-server-discovery-grouping:
    +-- (server-discovery-manner)?
       +--:(reverse-dns)
       |  +-- rdns-naptr-records
       |     +-- static-prefix*           inet:ip-prefix
       |     +-- dynamic-prefix-source*
       |             -> /alto-server/data-source/source-id
       +--:(internet-routing-registry)
       |  +-- irr-params
       |     +-- aut-num?   inet:as-number
       +--:(peeringdb)
          +-- peeringdb-params
             +-- org-id?   uint32

The server-discovery node provides configuration for ALTO server discovery using different mechanisms.¶

The reverse-dns case is used to configure DNS NAPTR records for ALTO server discovery, which is suugested by [RFC7286] and [RFC8686]. It configures a set of endpoints in the scope of the network domain serving this ALTO server. The node contains two leaf lists. The static list contains a list of manual configured endpoints. The dynamic list points to a list of data sources to retrieve the endpoints dynamically. As suggested by [RFC7286] and [RFC8686], the IP prefixes in the scope will be translated into DNS NAPTR resource records for server discovery.¶
The internet-routing-registry case is used to configure objects in an Internet Routing Registry (IRR) database. Other ALTO servers/clients can query an IRR database using the Routing Policy Specification Language (RPSL) [RFC2622] to get the corresponding ALTO server to a given Autonomous System (AS).¶
The peeringdb case is used to configure organization records in PeeringDB. Other ALTO servers/clients can directly query the PeeringDB to get the corresponding ALTO server to a given network.¶

5.2.2. Data Model for Logging Management

To satisfy R2 in Section 4.2, the ALTO server instance contains the following configuration parameters for the logging management.¶

The logging-system node provides configuration to select a logging system to capture log messages generated by the ALTO server.¶

By default, syslog is the only supported logging system. When selecting syslog, the related configuration is delegated to the configuration file of the syslog server.¶

  grouping alto-logging-system-grouping:
    +-- (logging-system)?
       +--:(syslog)
          +-- syslog-params
             +-- config-file?   inet:uri

A specific server implementation can extend the logging-system node to add other logging systems.¶

5.2.4. Data Model for Security Management

To satisfy R4 in Section 4.2, the data model leverages HTTP and TLS to provide basic security management for an ALTO server. All the related configurations are covered by the server listen stack.¶

5.3. Data Model for ALTO Server Configuration Management

5.3.1. Data Source Configuration Management

To satisfy R5-1 in Section 4.2, the ALTO server instance contains a list of data-source entries to subscribe the data sources from which ALTO information resources are derived (See Section 16.2.4 of [RFC7285]).¶

A data-source entry MUST include:¶

a unique source-id for resource creation algorithms to reference,¶
the source-type attribute to declare the type of the data source,¶
the update-policy to specify how to get the data update from the data source,¶
the source-params to specify where and how to query the data.¶

The update policy can be either reactive or proactive. For the reactive update, the ALTO server gets the update as soon as the data source changes. For the proactive update, the ALTO server has to proactively fetch the data source periodically.¶

To use the reactive update, the reactive attribute MUST be set true. To use the proactive update, the poll-interval attribute MUST be greater than zero. The value of poll-interval specifies the interval of fetching the data in milliseconds. If reactive is false or poll-interval is zero, the ALTO server will not update the data source.¶

The data-source/source-params node can be augmented for different types of data sources.¶

module: ietf-alto
  +--rw alto-server
     ...
     +--rw data-source* [source-id]
     |  +--rw source-id              string
     |  +--rw source-type            identityref
     |  +--rw (update-policy)
     |  |  +--:(reactive)
     |  |  |  +--rw reactive         boolean
     |  |  +--:(proactive)
     |  |     +--rw poll-interval    uint32
     |  +--rw (source-params)?
     ...

This data model only includes common configuration parameters for an ALTO server to correctly interact with a data source. The implementation-specific parameters of any certain data source can be augmented in another module. An example is included in Appendix A.1.¶

5.3.2. ALTO Information Resources Configuration Management

To satisfy R5-2 and R-3, the ALTO server instance contains a list of resource entries. Each resource entry contains the configurations of an ALTO information resource (See Section 8.1 of [RFC7285]). The operator of the ALTO server can use this model to create, update, and remove the ALTO information resource.¶

Each resoruce entry provides configurations defining how to create or update an ALTO information resource. Adding a new resource entry notifies the ALTO server to create a new ALTO information resource. Updating an existing resource entry notifies the ALTO server to update the generation parameters (e.g., capabilities and the creation algorithm) of an existing ALTO information resource. Removing an existing resource entry will remove the corresponding ALTO information resource.¶

A resource entry MUST include a unique resource-id and a resource-type.¶

It can also include an accepted-group node containing a list of user-groups that can access this ALTO information resource. As section 15.5.2 of [RFC7285] suggests, the module also defines authentication related configuration to employ access control at information resource level. The ALTO server returns the IRD to the ALTO client based on its authentication information.¶

For some resource-type, the resource entry MUST also include the a dependency node containing the resource-id of the dependent ALTO information resources (See Section 9.1.5 of [RFC7285]).¶

For each type of ALTO information resource, the resource entry MAY also need type-specific parameters. These type-specific parameters include two categories:¶

One categories of the type-specific parameters are common for the same type of ALTO information resource. They declare the Capabilities of the ALTO information resource (See Section 9.1.3 of [RFC7285]).¶
The other categories of the type-specific parameters are algorithm-specific. The developer of the ALTO server can implement their own creation altorithms and augment the algorithm node to declare algorithm-specific input parameters.¶

Except for the ird resource, all the other types of resource entries have augmented algorithm node. The augmented algorithm node can reference data sources subscribed by the data-source entries (See Section 5.3.1). An example of extending algorithm node for a specific type of resource is included in Appendix A.2.¶

The developer cannot customize the creation algorithm of the ird resource. The default ird resource will be created automatically based on all the added resource entries. The delegated ird resource will be created as a static ALTO information resource (See Section 9.2.4 of [RFC7285]).¶

module: ietf-alto
  +--rw alto-server
     ...
     +--rw resource* [resource-id]
        +--rw resource-id                       resource-id
        +--rw resource-type                     identityref
        +--rw description?                      string
        +--rw accepted-group*                   string
        +--rw dependency*
        |       -> /alto-server/resource/resource-id
        +--rw auth
        |  +--rw (auth-type-selection)?
        |     +--:(auth-key-chain)
        |     |  +--rw key-chain?   key-chain:key-chain-ref
        |     +--:(auth-key)
        |     +--:(auth-tls)
        +--rw (resource-params)?
           +--:(ird)
           |  +--rw alto-ird-params
           |     +--rw delegation    inet:uri
           +--:(networkmap)
           |  +--rw alto-networkmap-params
           |     +--rw is-default?   boolean
           |     +--rw filtered?     boolean
           |     +---u algorithm
           +--:(costmap)
           |  +--rw alto-costmap-params
           |     +--rw filtered?             boolean
           |     +---u filter-costmap-cap
           |     +---u algorithm
           +--:(endpointcost)
           |  +--rw alto-endpointcost-params
           |     +---u endpoint-cost-cap
           |     +---u algorithm
           +--:(endpointprop)
           |  +--rw alto-endpointprop-params
           |     +--rw prop-types*   string
           |     +---u algorithm
           +--:(propmap) {propmap}?
           |  +--rw alto-propmap-params
           |     +---u algorithm
           +--:(cdni) {cdni}?
           |  +--rw alto-cdni-params
           |     +---u algorithm
           +--:(update) {incr-update}?
              +--rw alto-update-params
                 +---u algorithm

  grouping filter-costmap-cap:
    +-- cost-type-names*            string
    +-- cost-constraints?           boolean
    +-- max-cost-types?             uint32 {multi-cost}?
    +-- testable-cost-type-names*   string {multi-cost}?
    +-- calendar-attributes {cost-calendar}?
       +-- cost-type-names*       string
       +-- time-interval-size     decimal64
       +-- number-of-intervals    uint32
  grouping endpoint-cost-cap:
    +---u filter-costmap-cap
  grouping algorithm:
    +-- (algorithm)

7. ALTO OAM YANG Module

7.1. The ietf-alto Module

<CODE BEGINS> file "ietf-alto@2022-07-11.yang"

module ietf-alto {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-alto";
  prefix "alto";

  import ietf-inet-types {
    prefix "inet";
    reference
      "RFC 6991: Common YANG Data Types";
  }

  import ietf-key-chain {
    prefix key-chain;
    reference
      "RFC 8177: YANG Data Model for Key Chains";
  }

  import ietf-tcp-server {
    prefix tcp;
    reference
      "RFC DDDD: YANG Groupings for TCP Clients and TCP Servers";
  }

  import ietf-tls-server {
    prefix tls;
    reference
      "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
  }

  import ietf-http-server {
    prefix http;
    reference
      "RFC GGGG: YANG Groupings for HTTP Clients and HTTP Servers";
  }

  organization
    "IETF ALTO Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/alto/about/>
     WG List:  <alto@ietf.org>";

  description
    "This YANG module defines all the configured and operational
     parameters of the administrated ALTO server instance.

     Copyright (c) 2022 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.

     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 (RFC 2119) (RFC 8174) when, and only when,
     they appear in all capitals, as shown here.";

  revision "2022-10-24" {
    description
      "Initial Version.";
    reference
      "RFC XXXX: A YANG Data Model for OAM and Management of ALTO
       Protocol.";
  }

  typedef resource-id {
    type string {
      length "1..64";
      pattern "[0-9a-zA-Z\\-:@_]*";
    }
    description
      "Format of Resource ID";
    reference
      "Section 9.1.1 of RFC 7285.";
  }

  // Base identities

  identity resource-type {
    description
      "Base identity for type of information resource.";
  }

  identity source-type {
    description
      "Base identity for type of data source.";
  }

  identity cost-mode {
    description
      "The cost mode attribute indicates how costs should be
       interpreted. Specifically, the cost mode attribute indicates
       whether returned costs should be interpreted as numerical
       values or ordinal rankings.";
    reference
      "Section 6.1.2 of RFC 7285.";
  }

  identity cost-metric {
    description
      "The cost metric attribute indicates what the cost
       represents.";
    reference
      "Section 6.1.1 of RFC 7285.";
  }

  // Identities for ALTO information resources

  identity network-map {
    base resource-type;
    description
      "Identity for network map.";
  }

  identity cost-map {
    base resource-type;
    description
      "Identity for cost map.";
  }

  identity property-map {
    base resource-type;
    description
      "Identity for property map.";
  }

  // Identities for cost mode

  identity numerical {
    base cost-mode;
    description
      "This mode indicates that it is safe to perform numerical
       operations";
  }

  identity ordinal {
    base cost-mode;
    description
      "This mode indicates that the cost values in a cost map
       represent ranking";
  }

  identity array {
    if-feature "path-vector";
    base cost-mode;
    description
      "This mode indicates that every cost value in the response body
       of a (Filtered) Cost Map or an Endpoint Cost Service MUST be
       interpreted as a JSON array.";
  }

  // Identities for cost metrics

  identity routingcost {
    base cost-metric;
    description
      "This metric conveys a generic measure for the cost of routing
       traffic from a source to a destination.";
  }

  identity ane-path {
    if-feature "path-vector";
    base cost-metric;
    description
      "This metric indicates that the value of such a cost type
       conveys an array of Abstract Network Element (ANE) names,
       where each ANE name uniquely represents an ANE traversed by
       traffic from a source to a destination.";
  }

  identity delay-ow {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Section 4.1 of RFC XXXX";
  }

  identity delay-rt {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Section 4.2 of RFC XXXX";
  }

  identity delay-variation {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Section 4.3 of RFC XXXX";
  }

  identity lossrate {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Section 4.4 of RFC XXXX";
  }

  identity hopcount {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Section 4.5 of RFC XXXX";
  }

  identity tput {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Section 5.1 of RFC XXXX";
  }

  identity bw-residual {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Section 5.2 of RFC XXXX";
  }

  identity bw-available {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Section 5.3 of RFC XXXX";
  }

  // Features

  feature http-listen {
    description
      "The 'http-listen' feature is only used for test depolyment.
       According to Sec 8.3.5 of RFC 7285, it shouldn't be used in
       the production depolyment.";
  }

  feature multi-cost {
    description
      "Support multi-cost extension.";
    reference
      "RFC 8189: Multi-Cost Application-Layer Traffic Optimization
       (ALTO)";
  }

  feature incr-update {
    description
      "Support incremental update extension.";
    reference
      "RFC 8895: Application-Layer Traffic Optimization (ALTO)
       Incremental Updates Using Server-Sent Events (SSE)";
  }

  feature cost-calendar {
    description
      "Support cost calendar extension.";
    reference
      "RFC 8896: Application-Layer Traffic Optimization (ALTO) Cost
       Calendar";
  }

  feature propmap {
    description
      "Support entity property map extension.";
    reference
      "RFC 9240: An ALTO Extension: Entity Property Maps";
  }

  feature cdni {
    description
      "Support CDNi extension.";
    reference
      "RFC 9241: Content Delivery Network Interconnection (CDNI)
       Request Routing: CDNI Footprint and Capabilities
       Advertisement using ALTO";
  }

  feature path-vector {
    description
      "Support path vector extension.";
    reference
      "RFC XXXX: An ALTO Extension: Path Vector";
  }

  feature performance-metrics {
    description
      "Support performance metrics extension.";
    reference
      "RFC XXXX: ALTO Performance Cost Metrics";
  }

  // Groupings

  grouping filter-costmap-cap {
    description
      "This grouping defines data model for
       FilteredCostMapCapabilities.";
    reference
      "Sec 11.3.2.4 of RFC 7285.";
    leaf-list cost-type-names {
      type string;
      min-elements 1;
      description
        "Supported cost types";
    }
    leaf cost-constraints {
      type boolean;
      description
        "If true, then the ALTO server allows cost
         constraints to be included in requests to the
         corresponding URI. If not present, this field MUST
         be interpreted as if it specified false.";
    }
    leaf max-cost-types {
      if-feature "multi-cost";
      type uint32;
      default 0;
      description
        "If present with value N greater than 0, this resource
         understands the multi-cost extensions in this document and
         can return a multi-cost map with any combination of N or
         fewer cost types in the 'cost-type-names' list. If omitted,
         the default value is 0.";
    }
    leaf-list testable-cost-type-names {
      if-feature "multi-cost";
      type string;
      description
        "If present, the resource allows constraint tests, but only
         on the cost type names in this array.";
    }
    container calendar-attributes {
      if-feature "cost-calendar";
      leaf-list cost-type-names {
        type string;
        min-elements 1;
        description
          "An array of one or more elements indicating the cost type
           names in the IRD entry to which the values of
           'time-interval-size' and 'number-of-intervals' apply.";
      }
      leaf time-interval-size {
        type decimal64 {
          fraction-digits 4;
        }
        mandatory true;
        description
          "The duration of an ALTO Calendar time interval in a unit
           of seconds.";
      }
      leaf number-of-intervals {
        type uint32 {
          range "1..max";
        }
        mandatory true;
        description
          "A strictly positive integer (greater or equal to 1) that
           indicates the number of values of the Cost Calendar
           array.";
      }
      description
        "Configuration for CalendarAttributes.";
      reference
        "Section 4.1 of RFC 8896.";
    }
  }

  grouping endpoint-cost-cap {
    uses filter-costmap-cap;
    description
      "This grouping defines EndpointCostCapabilities as the same as
       FilteredCostMapCapabilities defined by the grouping
       filter-costmap-cap.";
    reference
      "Section 11.5.1.4 of RFC 7285";
  }

  grouping algorithm {
    choice algorithm {
      mandatory true;
      description
        "Information resource creation algorithm to be augmented.";
    }
    description
      "This grouping defines base data model for information
       resource creation algorithm.";
  }

  grouping alto-server-grouping {
    description
      "A reuseable grouping for configuring an ALTO server without
       any consideration for how underlying transport sessions are
       established.";
    leaf base-uri {
      type inet:uri;
      description
        "The base URI for the ALTO server.";
    }
  }

  grouping alto-server-listen-stack-grouping {
    description
      "A reuseable grouping for configuring an ALTO server
       'listen' protocol stack for a single connection.";
    choice transport {
      mandatory true;
      description
        "Selects between available transports.";
      case http {
        if-feature "http-listen";
        container http {
          description
            "Configures ALTO server stack assuming that
             TLS-termination is handled externally.";
          container tcp-server-parameters {
            description
              "A wrapper around the TCP server parameters
               to avoid name collisions.";
            uses tcp:tcp-server-grouping {
              refine "local-port" {
                default "80";
                description
                  "The RESTCONF server will listen on the IANA-
                   assigned well-known port value for 'http'
                   (80) if no value is specified.";
              }
            }
          }
          container http-server-parameters {
            description
              "A wrapper around the HTTP server parameters
               to avoid name collisions.";
            uses http:http-server-grouping;
          }
          container alto-server-parameters {
            description
              "A wrapper around the ALTO server parameters
               to avoid name collisiions.";
            uses alto-server-grouping;
          }
        }
      }
      case https {
        container https {
          description
            "Configures ALTO server stack assuming that
             TLS-termination is handled internally.";
          container tcp-server-parameters {
            description
              "A wrapper around the TCP server parameters
               to avoid name collisions.";
            uses tcp:tcp-server-grouping {
              refine "local-port" {
                default "443";
                description
                  "The ALTO server will listen on the IANA-
                   assigned well-known port value for 'https'
                   (443) if no value is specified.";
              }
            }
            container tls-server-parameters {
              description
                "A wrapper around the TLS server parameters
                 to avoid name collisions.";
              uses tls:tls-server-grouping;
            }
            container http-server-parameters {
              description
                "A wrapper around the HTTP server parameters
                 to avoid name collisions.";
              uses http:http-server-grouping;
            }
            container alto-server-parameters {
              description
                "A wrapper around the ALTO server parameters
                 to avoid name collisions.";
              uses alto-server-grouping;
            }
          }
        }
      }
    }
  }

  grouping alto-server-discovery-grouping {
    description
      "Configure how to set up server discovery for clients or other
       ALTO servers to discovery the URI of this ALTO server.";
    choice server-discovery-manner {
      description
        "Selects among available server discovery manners";
      case reverse-dns {
        description
          "Configure DNS NAPTR records for cross-domain ALTO server
           discovery using reverse DNS lookup.";
        container rdns-naptr-records {
          description
            "Configuration parameters for DNS NAPTR records.";
          leaf-list static-prefix {
            type inet:ip-prefix;
            description
              "Static IP prefixes in the scope.";
          }
          leaf-list dynamic-prefix-source {
            type leafref {
              path "/alto:alto-server/alto:data-source/alto:source-id";
            }
            description
              "Dynamic IP prefixes collected from data sources.";
          }
        }
        reference
          "RFC 8686: Application-Layer Traffic Optimization (ALTO)
           Cross-Domain Server Discovery.";
      }
      case internet-routing-registry {
        description
          "Update descr attributes of a aut-num class in a Internet
           Routing Registry (IRR) database for ALTO server discovery
           using RPSL.";
        reference
          "RFC 2622: Routing Policy Specification Language (RPSL).";
        container irr-params {
          description
            "Configuration parameters for IRR database.";
          leaf aut-num {
            type inet:as-number;
            description
              "The autonomous system (AS) to be updated.";
          }
        }
      }
      case peeringdb {
        description
          "Update metadata of a network record in PeeringDB database
           for ALTO server discovery using PeeringDB lookup.";
        container peeringdb-params {
          description
            "Configuration parameters for PeeringDB database.";
          leaf org-id {
            type uint32;
            description
              "The ID referring to the org object of the
               organization record in PeeringDB.";
          }
        }
      }
    }
  }

  grouping alto-logging-system-grouping {
    description
      "Grouping for configuration of logging system used by the ALTO
       server.";
    choice logging-system {
      description
        "Selects among available logging systems";
      case syslog {
        description
          "Use syslog as logging system.";
        container syslog-params {
          description
            "Configuration parameters for syslog.";
          leaf config-file {
            type inet:uri {
              pattern 'file:.*';
            }
            description
              "The file location of the syslog configuration.";
          }
        }
      }
    }
  }

  // Top-level container

  container alto-server {
    description
      "The ALTO server instance.";
    container listen {
      description
        "Configure the ALTO server to listen for ALTO clients.";
      uses alto-server-listen-stack-grouping;
    }
    container server-discovery {
      description
        "Configure how the ALTO server to be discovered by others.";
      uses alto-server-discovery-grouping;
    }
    container logging-system {
      description
        "Configure logging system to capture log messages generated
         by the ALTO server.";
      uses alto-logging-system-grouping;
    }
    list cost-type {
      key "cost-type-name";
      leaf cost-type-name {
        type string;
        description
          "The name to reference cost type";
      }
      leaf cost-mode {
        type identityref {
          base cost-mode;
        }
        mandatory true;
        description
          "The referenced cost mode";
      }
      leaf cost-metric {
        type identityref {
          base cost-metric;
        }
        mandatory true;
        description
          "The referenced cost metric";
      }
      description
        "Mapping between name and referenced cost type";
    }
    list meta {
      key "meta-key";
      leaf meta-key {
        type string;
        description
          "Custom meta key";
      }
      leaf meta-value {
        type string;
        mandatory true;
        description
          "Custom meta value";
      }
      description
        "Mapping of custom meta information";
      reference
        "Section 8.4.1 of RFC 7285.";
    }
    list data-source {
      key "source-id";
      leaf source-id {
        type string;
        description
          "Data source id that can be referenced by information
           resource creation algorithms.";
      }
      leaf source-type {
        type identityref {
          base source-type;
        }
        mandatory true;
        description
          "Identify the type of the data source.";
      }
      choice update-policy {
        mandatory true;
        case reactive {
          leaf reactive {
            type boolean;
            mandatory true;
            description
              "Reactive mode.";
          }
        }
        case proactive {
          leaf poll-interval {
            type uint32;
            mandatory true;
            description
              "Polling interval in seconds for proactive mode.";
          }
        }
        description
          "Policy to get updates from data sources.";
      }
      choice source-params {
        description
          "Data source specific configuration.";
      }
      description
        "List of subscribed data sources.";
    }
    list resource {
      key "resource-id";
      leaf resource-id {
        type resource-id;
        description
          "resource-id to be defined.";
      }
      leaf resource-type {
        type identityref {
          base resource-type;
        }
        mandatory true;
        description
          "identityref to be defined.";
      }
      leaf description {
        type string;
        description
          "The optional description for this information resource.";
      }
      leaf-list accepted-group {
        type string;
        description
          "Access list for authenticated clients.";
      }
      leaf-list dependency {
        type leafref {
          path "/alto:alto-server/alto:resource/alto:resource-id";
        }
        description
          "A list of dependent information resources.";
      }
      container auth {
        description
          "The authentication options";
        choice auth-type-selection {
          description
            "Options for expressing authentication
             setting.";
          case auth-key-chain {
            leaf key-chain {
              type key-chain:key-chain-ref;
              description
                "key-chain name.";
            }
          }
          case auth-key {
          }
          case auth-tls {
          }
        }
      }
      choice resource-params {
        description
          "Resource-specific configuration.";
        case ird {
          container alto-ird-params {
            leaf delegation {
              type inet:uri;
              mandatory true;
              description
                "Upstream IRD to be delegated.";
            }
            description
              "IRD-specific configuration.";
          }
        }
        case networkmap {
          container alto-networkmap-params {
            description
              "(Filtered) Network Map specific configuration.";
            reference
              "Section 11.2.1 and Section 11.3.1 of RFC 7285.";
            leaf is-default {
              type boolean;
              description
                "Set whether this is the default network map.";
            }
            leaf filtered {
              type boolean;
              default false;
              description
                "Configure whether filtered network map is
                 supported.";
            }
            uses algorithm;
          }
        }
        case costmap {
          container alto-costmap-params {
            description
              "(Filtered) Cost Map specific configuration.";
            reference
              "Section 11.2.2 and Section 11.3.2 of RFC 7285.";
            leaf filtered {
              type boolean;
              description
                "Configure whether filtered cost map is supported.";
            }
            uses filter-costmap-cap;
            uses algorithm;
          }
        }
        case endpointcost {
          container alto-endpointcost-params {
            description
              "Endpoint Cost Service specific configuration.";
            reference
              "Section 11.5 of RFC 7285.";
            uses endpoint-cost-cap;
            uses algorithm;
          }
        }
        case endpointprop {
          container alto-endpointprop-params {
            description
              "Endpoint Cost Service specific configuration.";
            reference
              "Section 11.5 of RFC 7285.";
            leaf-list prop-types {
              type string;
              min-elements 1;
              description
                "Supported endpoint properties.";
            }
            uses algorithm;
          }
        }
        case propmap {
          if-feature "propmap";
          container alto-propmap-params {
            uses algorithm;
            description
              "(Filtered) Entity Property Map specific
               configuration.";
          }
        }
        case cdni {
          if-feature "cdni";
          container alto-cdni-params {
            uses algorithm;
            description
              "CDNi specific configuration";
          }
        }
        case update {
          if-feature "incr-update";
          container alto-update-params {
            uses algorithm;
            description
              "Incremental Updates specific configuration";
          }
        }
      }
      description
        "ALTO information resources to be defined";
    }
  }
}

<CODE ENDS>

7.2. The ietf-alto-stats Module

<CODE BEGINS> file "ietf-alto-stats@2022-07-11.yang"

module ietf-alto-stats {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-alto-stats";
  prefix "alto-stats";

  import ietf-yang-types {
    prefix "yang";
    reference
      "RFC 6991: Common YANG Data Types";
  }

  import ietf-alto {
    prefix alto;
    reference
      "RFC XXXX: A YANG Data Model for OAM and Management of ALTO
       Protocol.";
  }

  organization
    "IETF ALTO Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/alto/about/>
     WG List:  <alto@ietf.org>";

  description
    "This YANG module defines all the configured and operational
     parameters of the administrated ALTO server instance.

     Copyright (c) 2022 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 "2022-07-11" {
    description
      "Initial Version.";
    reference
      "RFC XXXX: A YANG Data Model for Operations, Administration,
       and Maintenance of ALTO Protocol.";
  }

  augment "/alto:alto-server" {
    description
      "Top-level statistics for the whole ALTO server.";
    leaf num-total-req {
      type yang:counter32;
      config false;
      description
        "The total number of ALTO requests received by this ALTO
         server.";
    }
    leaf num-total-succ {
      type yang:counter32;
      config false;
      description
        "The total number of successful responses sent by this ALTO
         server.";
    }
    leaf num-total-fail {
      type yang:counter32;
      config false;
      description
        "The total number of failed responses sent by this ALTO
         server.";
    }
    leaf num-total-last-req {
      type yang:counter32;
      config false;
      description
        "The total number of ALTO requests received within the last
         5 minutes.";
    }
    leaf num-total-last-succ {
      type yang:counter32;
      config false;
      description
        "The total number of successful responses sent by this ALTO
         server within the last 5 minutes.";
    }
    leaf num-total-last-fail {
      type yang:counter32;
      config false;
      description
        "The total number of failed responses sent by this ALTO
         server within the last 5 minutes.";
    }
  }

  augment "/alto:alto-server/alto:resource" {
    description
      "Common statistics for each information resource.";
    leaf num-res-upd {
      type yang:counter32;
      config false;
      description
        "The number of version updates since the information resource
         was created.";
    }
    leaf res-mem-size {
      type yang:counter32;
      config false;
      description
        "Memory size (Bytes) utilized by the information resource.";
    }
    leaf res-enc-size {
      type yang:counter32;
      config false;
      description
        "Size (Bytes) of JSON encoded data of the information
         resource.";
    }
    leaf num-res-req {
      type yang:counter32;
      config false;
      description
        "The number of ALTO requests to this information resource.";
    }
    leaf num-res-succ {
      type yang:counter32;
      config false;
      description
        "The number of successful responses for requests to this
         information resource.";
    }
    leaf num-res-fail {
      type yang:counter32;
      config false;
      description
        "The total number of failed responses for requests to this
         information resource.";
    }
  }

  augment "/alto:alto-server/alto:resource/alto:resource-params"
        + "/alto:networkmap/alto:alto-networkmap-params" {
    description
      "Augmented statistics for network maps only.";
    leaf num-map-pid {
      type yang:counter32;
      config false;
      description
        "Number of PIDs contained by the network map.";
    }
  }

  augment "/alto:alto-server/alto:resource/alto:resource-params"
        + "/alto:propmap/alto:alto-propmap-params" {
    description
      "Augmented statistics for property maps only.";
    leaf num-map-entry {
      type yang:counter32;
      config false;
      description
        "Number of ALTO entities contained by the property map.";
    }
  }

  augment "/alto:alto-server/alto:resource/alto:resource-params"
        + "/alto:cdni/alto:alto-cdni-params" {
    description
      "Augmented statistics for CDNi resources only.";
    leaf num-base-obj {
      type yang:counter32;
      config false;
      description
        "Number of base CDNi advertisement objects contained by the
         CDNi resource.";
    }
  }

  augment "/alto:alto-server/alto:resource/alto:resource-params"
        + "/alto:update/alto:alto-update-params" {
    description
      "Augmented statistics for incremental updates only.";
    leaf num-upd-sess {
      type yang:counter32;
      config false;
      description
        "Number of sessions connected to the incremental update
         service.";
    }
    leaf num-event-total {
      type yang:counter32;
      config false;
      description
        "Total number of update events sent to all the connected
         clients.";
    }
    leaf num-event-max {
      type yang:counter32;
      config false;
      description
        "The maximum number of update events sent to the connected
         clients.";
    }
    leaf num-event-min {
      type yang:counter32;
      config false;
      description
        "The minimum number of update events sent to the connected
         clients.";
    }
    leaf num-event-avg {
      type yang:counter32;
      config false;
      description
        "The average number of update events sent to the connected
         clients.";
    }
  }
}

<CODE ENDS>

10. References

10.1. 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/rfc/rfc2119>.
[RFC3688]: Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, <https://www.rfc-editor.org/rfc/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/rfc/rfc6020>.
[RFC6991]: Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, <https://www.rfc-editor.org/rfc/rfc6991>.
[RFC7285]: Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., Previdi, S., Roome, W., Shalunov, S., and R. Woundy, "Application-Layer Traffic Optimization (ALTO) Protocol", RFC 7285, DOI 10.17487/RFC7285, September 2014, <https://www.rfc-editor.org/rfc/rfc7285>.
[RFC7286]: Kiesel, S., Stiemerling, M., Schwan, N., Scharf, M., and H. Song, "Application-Layer Traffic Optimization (ALTO) Server Discovery", RFC 7286, DOI 10.17487/RFC7286, November 2014, <https://www.rfc-editor.org/rfc/rfc7286>.
[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/rfc/rfc8174>.
[RFC8177]: Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J. Zhang, "YANG Data Model for Key Chains", RFC 8177, DOI 10.17487/RFC8177, June 2017, <https://www.rfc-editor.org/rfc/rfc8177>.
[RFC8189]: Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost Application-Layer Traffic Optimization (ALTO)", RFC 8189, DOI 10.17487/RFC8189, October 2017, <https://www.rfc-editor.org/rfc/rfc8189>.
[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/rfc/rfc8340>.
[RFC8686]: Kiesel, S. and M. Stiemerling, "Application-Layer Traffic Optimization (ALTO) Cross-Domain Server Discovery", RFC 8686, DOI 10.17487/RFC8686, February 2020, <https://www.rfc-editor.org/rfc/rfc8686>.
[RFC8895]: Roome, W. and Y. Yang, "Application-Layer Traffic Optimization (ALTO) Incremental Updates Using Server-Sent Events (SSE)", RFC 8895, DOI 10.17487/RFC8895, November 2020, <https://www.rfc-editor.org/rfc/rfc8895>.
[RFC8896]: Randriamasy, S., Yang, R., Wu, Q., Deng, L., and N. Schwan, "Application-Layer Traffic Optimization (ALTO) Cost Calendar", RFC 8896, DOI 10.17487/RFC8896, November 2020, <https://www.rfc-editor.org/rfc/rfc8896>.

10.2. Informative References

[I-D.ietf-alto-performance-metrics]: Wu, Q., Yang, Y. R., Lee, Y., Dhody, D., Randriamasy, S., and L. M. Contreras, "ALTO Performance Cost Metrics", Work in Progress, Internet-Draft, draft-ietf-alto-performance-metrics-28, 21 March 2022, <https://datatracker.ietf.org/doc/html/draft-ietf-alto-performance-metrics-28>.
[I-D.ietf-netconf-http-client-server]: Watsen, K., "YANG Groupings for HTTP Clients and HTTP Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-http-client-server-11, 19 October 2022, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-http-client-server-11>.
[I-D.ietf-netconf-tcp-client-server]: Watsen, K. and M. Scharf, "YANG Groupings for TCP Clients and TCP Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-tcp-client-server-14, 19 October 2022, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-tcp-client-server-14>.
[I-D.ietf-netconf-tls-client-server]: Watsen, K., "YANG Groupings for TLS Clients and TLS Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-tls-client-server-31, 19 October 2022, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-tls-client-server-31>.
[RFC2622]: Alaettinoglu, C., Villamizar, C., Gerich, E., Kessens, D., Meyer, D., Bates, T., Karrenberg, D., and M. Terpstra, "Routing Policy Specification Language (RPSL)", RFC 2622, DOI 10.17487/RFC2622, June 1999, <https://www.rfc-editor.org/rfc/rfc2622>.
[RFC7921]: Atlas, A., Halpern, J., Hares, S., Ward, D., and T. Nadeau, "An Architecture for the Interface to the Routing System", RFC 7921, DOI 10.17487/RFC7921, June 2016, <https://www.rfc-editor.org/rfc/rfc7921>.
[RFC7971]: Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and S. Previdi, "Application-Layer Traffic Optimization (ALTO) Deployment Considerations", RFC 7971, DOI 10.17487/RFC7971, October 2016, <https://www.rfc-editor.org/rfc/rfc7971>.
[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/rfc/rfc8346>.
[RFC9240]: Roome, W., Randriamasy, S., Yang, Y., Zhang, J., and K. Gao, "An Extension for Application-Layer Traffic Optimization (ALTO): Entity Property Maps", RFC 9240, DOI 10.17487/RFC9240, July 2022, <https://www.rfc-editor.org/rfc/rfc9240>.
[RFC9241]: Seedorf, J., Yang, Y., Ma, K., Peterson, J., and J. Zhang, "Content Delivery Network Interconnection (CDNI) Footprint and Capabilities Advertisement Using Application-Layer Traffic Optimization (ALTO)", RFC 9241, DOI 10.17487/RFC9241, July 2022, <https://www.rfc-editor.org/rfc/rfc9241>.
[RFC9275]: Gao, K., Lee, Y., Randriamasy, S., Yang, Y., and J. Zhang, "An Extension for Application-Layer Traffic Optimization (ALTO): Path Vector", RFC 9275, DOI 10.17487/RFC9275, September 2022, <https://www.rfc-editor.org/rfc/rfc9275>.

Appendix A. Example: Extending the ALTO O&M Data Model

Developers and operators can also extend this ALTO O&M data model to align with their own implementations. Specifically, the following nodes of the data model can be augmented:¶

The data-source choice.¶
The algorithm choice of the resource-params of each resource.¶

A.1. Example Module for Extended Data Sources

The base data model defined by ietf-alto.yang does not include any choice cases for specific data sources. The following example module demonstrates how a implementation-specific data source can be augmented into the base data model.¶

The yang-datastore case is used to import the YANG data from a YANG model-driven data store.¶

It supports two types of endpoints: local and remote.¶

For a local endpoint, the YANG data is located the data from the same YANG model-driven data store supplying the current ALTO O&M data model. Therefore, the ALTO data source listener retrieves the data using the internal API provided by the data store.¶
For a remote endpoint, the ALTO data source listener establishes an HTTP connection to the remote RESTCONF server, and retrieve the data using the RESTCONF API.¶

The source-path is used to specify the XPath of the data source node.¶

module example-ietf-alto-data-source {

  namespace "urn:example:ietf-alto-data-source";
  prefix "alto-ds";

  import ietf-alto {
    prefix alto;
  }

  identity yang-datastore {
    base source-type;
    description
      "Identity for data source of YANG-based datastore.";
  }

  augment "/alto:alto-server/alto:data-source/alto:source-params" {
    case yang-datastore {
      when 'derived-from-or-self(source-type, "alto:yang-datastore"';
      container yang-datastore-source-params {
        leaf source-path {
          type yang:xpath1.0;
          mandatory true;
          description
            "XPath to subscribed YANG datastore node.";
        }
        description
          "YANG datastore specific configuration.";
        choice restconf-endpoint {
          case local {
            // Use local API to access YANG datastore
          }
          case remote {
            container restconf-endpoint-params {
              uses rcc:restconf-client-listen-stack-grouping;
            }
          }
        }
      }
    }
  }

A.2. Example Module for Information Resource Creation Algorithm

The base data model defined by ietf-alto.yang does not include any choice cases for information resource creation algorithms. But developers may augment the ietf-alto.yang data model with definitions for any custom creation algorithms for different information resources. The following example module demonstrates the parameters of a network map creation algorithm that translates an IETF layer 3 unicast topology into a network map.¶

module: example-ietf-alto-alg

  augment /alto:alto-server/alto:resource/alto:resource-params
            /alto:networkmap/alto:alto-networkmap-params
            /alto:algorithm:
    +--:(l3-unicast-cluster)
       +--rw l3-unicast-cluster-algorithm
          +--rw l3-unicast-topo
          |       -> /alto:alto-server/data-source/source-id
          +--rw depth?             uint32

This example defines a creation algorithm called l3-unicast-cluster-algorithm for the network map resource. It takes two algorithm-specific parameters:¶

l3-unicast-topo: This parameter refers to the source id of a data source node subscribed in the data-source list (See Section 5.3.1). The corresponding data source is assumed to be a yang-datastore data source (See Appendix A.1) for an IETF layer 3 unicast topology defined in [RFC8346]. The algorithm uses the topology data from this data source to compute the ALTO network map resource.¶
depth: This optional parameter sets the depth of the clustering algorithm. For example, if the depth sets to 1, the algorithm will generate PID for every l3-node in the topology.¶

The creation algorithm can be reactively called once the referenced data source updates. Therefore, the ALTO network map resource can be updated dynamically. The update of the reference data source depends on the used update-policy (See Section 5.3.1).¶

module example-ietf-alto-alg {

  namespace "urn:example:ietf-alto-alg";
  prefix "alto-alg";

  import ietf-alto {
    prefix "alto";
  }

  augment "/alto:alto-server/alto:resource/alto:resource-params"
        + "/alto:networkmap/alto:alto-networkmap-params"
        + "/alto:algorithm" {
    case l3-unicast-cluster {
      container l3-unicast-cluster-algorithm {
        leaf l3-unicast-topo {
          type leafref {
            path "/alto:alto-server/data-source/source-id";
          }
          mandatory true;
          description
            "The data source to an IETF layer 3 unicast topology.";
        }
        leaf depth {
          type uint32;
          description
            "The depth of the clustering.";
        }
      }
    }
  }
}