YANG Data Models for the Application-Layer Traffic Optimization (ALTO) Protocol

Internet-Draft	ALTO O&M YANG	January 2024
Zhang, et al.	Expires 22 July 2024	[Page]

Abstract

This document defines a YANG data model for Operations, Administration, and Maintenance (OAM) & Management of the Application-Layer Traffic Optimization (ALTO) Protocol. The operator of an ALTO server can use this data model to (1) set up the ALTO server, (2) configure server discovery, (3) create, update and remove ALTO information resources, (4) manage the access control of each ALTO information resource, and (5) collect statistical data from the ALTO server. The application provider can also use this data model to configure ALTO clients to communicate with known ALTO servers.¶

Table 1: Prefixes and corresponding YANG modules
Prefix	YANG module	Reference
yang	ietf-yang-types	[RFC6991]
inet	ietf-inet-types	[RFC6991]
ds	ietf-datastores	[RFC8342]
yp	ietf-yang-push	[RFC8641]
ts	ietf-truststore	[I-D.ietf-netconf-trust-anchors]
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]
ncc	ietf-netconf-client	[I-D.ietf-netconf-netconf-client-server]
rcc	ietf-restconf-client	[I-D.ietf-netconf-restconf-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 basic configuration to receive data from 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 is designed to fit all the requirements listed in Section 4.¶

As shown in Figure 1, the top-level container 'alto' in the "ietf-alto" module contains a single 'alto-server' and a list 'alto-client'.¶

'alto-client' defines a list of configurations for other applications to bootstrap an ALTO client. These data nodes can also be used by data sources and information resource creation algorithms that are configured by an ALTO server instance.¶

The container 'alto-server' contains both configuration and operational data of an administrated ALTO server instance.¶

module: ietf-alto
  +--rw alto!
     +--rw alto-client* [client-id] {alto-client}?
     |  ...
     +--rw alto-server {alto-server}?
        +...
        +--rw auth-client* [client-id]
        |  ...
        +--rw role* [role-name]
        |  +--rw role-name    role-name
        |  +--rw client*      client-ref
        +--rw data-source* [source-id]
        |  ...
        +--rw resource* [resource-id]
           ...

Figure 1: IETF ALTO Tree Structure

5.2. Data Model for ALTO Client Operation and Management

As shown in Figure 2, the 'alto-client' contains a list of client-side configurations. Each 'alto-client' entry contains the following data nodes:¶

'client-id':: A unique identifier that can be referenced by other applications.¶
'server-discovery-client':: A container that is used to configure how this ALTO client discovers an ALTO server.¶

module: ietf-alto
  +--rw alto!
     +--rw alto-client* [client-id] {alto-client}?
     |  +--rw client-id                  string
     |  +--rw server-discovery-client
     |     +---u alto-server-discovery-client
     ...

Figure 2: IETF ALTO Client Subtree Structure

5.3. Data Model for Server-level Operation and Management

The ALTO server instance contains a set of data nodes for server-level operation and management for ALTO that are shown in Figure 3. This structure satisfies R1 - R4 in Section 4.2.¶

module: ietf-alto
  +--rw alto!
     ...
     +--rw alto-server {alto-server}?
        +--rw listen
        |  +---u alto-server-listen-stack
        +--rw server-discovery
        |  +---u alto-server-discovery
        +--rw logging-system
        |  +---u alto-logging-system
        +--rw cost-type* [cost-type-name]
        |  +--rw cost-type-name    cost-type-name
        |  +--rw cost-mode         identityref
        |  +--rw cost-metric       identityref
        |  +--rw description?      string
        |  +--rw cost-context {performance-metrics}?
        |     +--rw cost-source    identityref
        |     +--rw parameters
        |        +--rw (parameters)?
        +--rw meta* [meta-key]
        |  +--rw meta-key      meta-key
        |  +--rw meta-value    binary
        ...

Figure 3: IETF ALTO Server Level Subtree Structure

5.3.1. Data Model for ALTO Server Setup

To satisfy R1 in Section 4.2, the ALTO server instance contains the basic data nodes for the server setup that are detailed in the following subsections.¶

5.3.1.1. ALTO Server Listen Stack

The container 'listen' contains all the data nodes for the whole server listen stack across TCP, TLS, HTTP and application layers (Figure 4).¶

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

Figure 4: IETF ALTO Server Groupings Structure

The 'transport' choice node enables which protocol layers to be configured. By default, two cases are defined for different deployment scenarios:¶

The 'http' case is provided to support scenarios where the TLS-termination is handled by other external components, e.g., reverse proxies or ingress controllers.¶
The 'https' case is provided to support scenarios where the whole HTTPS server listen stack including TLS is handled by the ALTO server itself.¶

5.3.1.2. ALTO Server Discovery Setup

In practice, for a large-scale network consisting of multiple administrative domains, the information about the network may be partitioned and distributed over multiple ALTO servers. That may require discovery and communication among different ALTO servers.¶

The "ietf-alto" module provides the configuration for how an ALTO server can be discovered by another ALTO server or client on demand (Figure 5). However, it does not contain any configuration for the communication among ALTO servers because the related solution has not become a standard. Future documents may extend it to fully support multi-domain scenarios.¶

  grouping alto-server-discovery:
    +-- (server-discovery-manner)?
       +--:(reverse-dns) {xdom-disc}?
          +-- rdns-naptr-records
             +-- static-prefix*           inet:ip-prefix
             +-- dynamic-prefix-source*   data-source-ref

Figure 5: IETF ALTO Server Discovery Grouping Structure

The 'server-discovery' node provides configuration for the discovery of ALTO servers using a variety of mechanisms. The initial version of the "ietf-alto" module only defines the 'reverse-dns' case that is used to configure DNS NAPTR records for ALTO server discovery as suggested by [RFC7286] and [RFC8686]. It configures a set of endpoints that can be served by this ALTO server. The node contains two leaf lists. The 'static' list contains a list of manually 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 of the endpoints configured by both 'static' and 'dynamic' lists will be translated into DNS NAPTR resource records for server discovery. The 'server-discovery-manner' choice can be augmented by the future modules to support other mechanisms.¶

5.3.2. Data Model for Logging Management

To satisfy R2 in Section 4.2, the ALTO server instance contains the the logging data nodes shown in Figure 6.¶

The 'logging-system' data node provides configuration to select a logging system to capture log messages generated by an 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 [RFC5424] server.¶

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

Figure 6: IETF ALTO Logging System Grouping Structure

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

5.3.4. 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.¶

5.4. Data Model for ALTO Server Configuration Management

5.4.1. 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 (Section 16.2.4 of [RFC7285]).¶

module: ietf-alto
  +--rw alto!
     ...
     +--rw alto-server {alto-server}?
        ...
        +--rw data-source* [source-id]
        |  +--rw source-id                    source-id
        |  +--rw source-type                  identityref
        |  +--rw source-params
        ...

Figure 7: IETF ALTO Server Data Source Subtree Structure

As shown in Figure 7, a 'data-source' list entry includes:¶

A unique 'source-id' for resource creation algorithms to reference.¶
The 'source-type' attribute to declare the type of the data source.¶
The 'source-params' to specify where and how to query the data.¶

The 'data-source/source-params' node can be augmented for different types of data sources. Note that the purpose of this node is not to fully set up the communication mechanisms for specific data sources, but to maintain how data sources are configured and expose them to the ALTO server.¶

This data model only includes a basic structure 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.3.¶

5.4.2. ALTO Information Resources Configuration Management

To satisfy R5-2 and R-3 in Section 4.2, the ALTO server instance contains a list of 'resource' entries (Figure 8). Each 'resource' entry contains the data nodes 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 resources.¶

Each 'resource' entry provides data nodes 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.¶

module: ietf-alto
  +--rw alto!
     ...
     +--rw alto-server {alto-server}?
        ...
        +--rw resource* [resource-id]
           +--rw resource-id                 resource-id
           +--rw resource-type               identityref
           +--rw description?                string
           +--rw accepted-role*              role-ref
           +--rw dependency*                 resource-ref
           +--rw alto-ird-params
           |  +--rw delegation    inet:uri
           +--rw alto-networkmap-params
           |  +--rw is-default?   boolean
           |  +--rw filtered?     boolean
           |  +---u algorithm
           +--rw alto-costmap-params
           |  +--rw filtered?             boolean
           |  +---u filter-costmap-cap
           |  +---u algorithm
           +--rw alto-endpointcost-params
           |  +---u filter-costmap-cap
           |  +---u algorithm
           +--rw alto-endpointprop-params
           |  +--rw prop-type*   endpoint-property
           |  +---u algorithm
           +--rw alto-propmap-params {propmap}?
           |  +---u algorithm
           +--rw alto-cdni-params {cdni}?
           |  +---u algorithm
           +--rw alto-update-params {incr-update}?
           |  +---u algorithm
           +--rw resource-limits
              +--rw notify-res-mem-limit?      uint64
              +--rw notify-upd-stream-limit?   uint64
                      {incr-update}?

  notifications:
    +---n alto-resource-event {alto-server}?
       +--ro resource-id                    resource-ref
       +--ro notify-res-mem-threshold?      uint64
       +--ro notify-upd-stream-threshold?   uint64 {incr-update}?

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

Figure 8: IETF ALTO Resource Subtree Structure

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

It may also include an 'accepted-role' node containing a list of 'role-name's that is used by role-based access control for this ALTO information resource. See Section 5.4.3 for details of information resource access control.¶

For some 'resource-type', the 'resource' entry may also include a 'dependency' node containing the 'resource-id' of the dependent ALTO information resources (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 can be split into two categories:¶

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

Except for the 'ird' resource, all the other types of 'resource' entries have an augmented 'algorithm' node. The augmented 'algorithm' node can reference data sources subscribed by the 'data-source' entries (See Section 5.4.1). An example of extending the 'algorithm' node for a specific type of 'resource' is included in Appendix A.4.¶

The developer does not have to 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 (Section 9.2.4 of [RFC7285]).¶

Each 'resource' entry may also set thresholds of memory usage and active update streams (if "incr-update" feature is enabled). Table 3 describes limits that, once exceeded, will trigger notifications to be generated:¶

Table 3: Notification Thresholds.
Notification Threshold	Description
notify-res-mem-limit	Used to notify high memory utilization of the resource configured to an ALTO server instance. When exceeded, an alto-resource-event will be generated.
notify-upd-stream-limit	Used to notify a high number of active update streams that are serviced by an update resource configured to an ALTO server instance. When exceeded, an alto-resource-event will be generated.

5.4.3. ALTO Information Resource Access Control Management

To satisfy R-3 in Section 4.2 and as per Section 15.5.2 of [RFC7285], the "ietf-alto" module also defines authentication and authorization related configuration to employ access control at the information resource level. The ALTO server returns the IRD to the ALTO client based on its authentication information.¶

The information resource access control is supported using the structure shown in Figure 9.¶

module: ietf-alto
  +--rw alto!
     ...
     +--rw alto-server {alto-server}?
        ...
        +--rw auth-client* [client-id]
        |  +--rw client-id                  string
        |  +--rw (authentication)?
        |     +--:(http)
        |     |  +--rw http-auth-client
        |     |          {http-listen,http:client-auth-supported,
        |     |           http:local-users-supported}?
        |     |     +--rw user-id    http-user-id-ref
        |     +--:(https)
        |        +--rw https-auth-client
        |        |       {http:client-auth-supported,
        |        |        http:local-users-supported}?
        |        |  +--rw user-id?   https-user-id-ref
        |        +--rw tls-auth-client
        |                {http:client-auth-supported}?
        |           +--rw ca-cert {tls:client-auth-x509-cert}?
        |           |  +---u inline-or-truststore-ca-cert-ref
        |           +--rw ee-cert {tls:client-auth-x509-cert}?
        |           |  +---u inline-or-truststore-ee-cert-ref
        |           +--rw raw-public-key
        |           |       {tls:client-auth-raw-public-key}?
        |           |  +---u inline-or-truststore-public-key-ref
        |           +--rw tls12-psks?       empty
        |           |       {tls:client-auth-tls12-psk}?
        |           +--rw tls13-epsks?      empty
        |                   {tls:client-auth-tls13-epsk}?
        +--rw role* [role-name]
        |  +--rw role-name    role-name
        |  +--rw client*      client-ref
        ...

Figure 9: IETF ALTO Client Authentication Subtree Structure

The structure shown in Figure 9 can be used to configure the role-based access control:¶

'auth-client' declares a list of ALTO clients that can be authenticated by the internal or external authorization server. This basic model only includes authentication approach directly provided by the HTTP or TLS server, but the operators or future documents can augment the 'authentication' choice for different authentication mechanisms.¶
'role' defines a list of roles for access control. Each role contains a list of authenticated ALTO clients. Each client can be assigned to multiple roles. The 'role-name' can be referenced by the 'accepted-role' list of a 'resource'. If an authenticated ALTO client is included in any roles with access permission to a resource, the client is granted access to that resource.¶

7. ALTO OAM YANG Modules

7.1. The "ietf-alto" YANG Module

<CODE BEGINS> file "ietf-alto@2023-02-23.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, Section 4";
  }
  import ietf-truststore {
    prefix ts;
    reference
      "RFC BBBB: A YANG Data Model for a Truststore";
  }
  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 a set of configured and operational
     parameters of an administrated ALTO server instance.

     Copyright (c) 2023 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 2023-02-23 {
    description
      "Initial Version.";
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer Traffic
                 Optimization (ALTO) Protocol";
  }

  // Features

  feature alto-client {
    description
      "Indicates that the implementation embeds an ALTO client
       instance.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol";
  }

  feature alto-server {
    description
      "Indicates that the implementation embeds an ALTO server
       instance.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol";
  }

  feature http-listen {
    description
      "The 'http-listen' feature is only used for test deployment.
       This feature shouldn't be used in the production
       deployment.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 8.3.5 ";
  }

  feature xdom-disc {
    description
      "Indicates support of cross-domain server discovery.";
    reference
      "RFC 8686: Application-Layer Traffic Optimization (ALTO)
                 Cross-Domain Server Discovery";
  }

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

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

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

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

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

  feature path-vector {
    description
      "Indicates support of path vector extension.";
    reference
      "RFC 9275: An Extension for Application-Layer Traffic
                 Optimization (ALTO): Path Vector";
  }

  feature performance-metrics {
    description
      "Indicates support of performance metrics extension.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics";
  }

  // Base identities

  identity resource-type {
    description
      "Base identity for type of information resource.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 8.1 ";
  }

  identity source-type {
    description
      "Base identity for type of data source. A data source
       indicates the origin from which the ALTO information
       resources are derived.";
  }

  identity cost-metric {
    description
      "The cost metric indicates what the cost represents.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 6.1.1";
  }

  identity cost-mode {
    description
      "The cost mode indicates how costs should be interpreted.
       Specifically, the cost mode attribute indicates whether
       indicated costs should be interpreted as numerical
       values or ordinal rankings.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 6.1.2
       RFC 9274: A Cost Mode Registry for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

  identity cost-source {
    description
      "The cost source indicates the high-level type of the
       data source.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 3.1";
  }

  // Identities for ALTO information resources

  identity ird {
    base resource-type;
    description
      "Identity for information resource directory.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 9";
  }

  identity network-map {
    base resource-type;
    description
      "Identity for network map.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 5";
  }

  identity cost-map {
    base resource-type;
    description
      "Identity for cost map.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 6";
  }

  identity endpoint-prop {
    base resource-type;
    description
      "Identity for endpoint property service.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 11.4.1";
  }

  identity endpoint-cost {
    base resource-type;
    description
      "Identity for endpoint cost service.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 11.5.1";
  }

  identity property-map {
    base resource-type;
    description
      "Identity for property map.";
    reference
      "RFC 9240: An ALTO Extension: Entity Property Maps";
  }

  identity cdni {
    base resource-type;
    description
      "Identity for Content Delivery Network Interconnection (CDNI)
       advertisement service.";
    reference
      "RFC 9241: Content Delivery Network Interconnection (CDNI)
                 Request Routing: CDNI Footprint and Capabilities
                 Advertisement using ALTO";
  }

  identity update {
    base resource-type;
    description
      "Identity for update stream service.";
    reference
      "RFC 8895: Application-Layer Traffic Optimization (ALTO)
                 Incremental Updates Using Server-Sent Events
                 (SSE)";
  }

  // Identities for cost mode

  identity numerical {
    base cost-mode;
    description
      "This mode indicates that it is safe to perform numerical
       operations";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 6.1.2.1";
  }

  identity ordinal {
    base cost-mode;
    description
      "This mode indicates that the cost values in a cost map
       represent ranking";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 6.1.2.2";
  }

  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 is
       interpreted as a JSON array.";
    reference
      "RFC 9275: An Extension for Application-Layer Traffic
                 Optimization (ALTO): Path Vector, Section 6.5.2";
  }

  // 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.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 6.1.1.1";
  }

  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.";
    reference
      "RFC 9275: An Extension for Application-Layer Traffic
                 Optimization (ALTO): Path Vector, Section 6.5.1";
  }

  identity delay-ow {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "One-way delay.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 4.1";
  }

  identity delay-rt {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Round-trip delay.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 4.2";
  }

  identity delay-variation {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Delay variation.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 4.3";
  }

  identity lossrate {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Loss rate.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 4.4";
  }

  identity hopcount {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Hop count.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 4.5";
  }

  identity tput {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "TCP throughput.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 5.1";
  }

  identity bw-residual {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Residual bandwidth.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 5.2";
  }

  identity bw-available {
    if-feature "performance-metrics";
    base cost-metric;
    description
      "Available bandwidth.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 5.3";
  }

  // Identities for cost sources

  identity nominal {
    if-feature "performance-metrics";
    base cost-source;
    description
      "The 'nominal' category indicates that the metric value is
       statically configured by the underlying devices.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 3.1";
  }

  identity sla {
    if-feature "performance-metrics";
    base cost-source;
    description
      "The 'sla' category indicates that the metric value is
       derived from some commitment which this document refers to
       as service-level agreement (SLA).";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 3.1";
  }

  identity estimation {
    if-feature "performance-metrics";
    base cost-source;
    description
      "The 'estimation' category indicates that the metric value is
       computed through an estimation process.";
    reference
      "RFC 9439: ALTO Performance Cost Metrics, Section 3.1";
  }

  // Typedefs

  typedef resource-id {
    type string {
      length "1..64";
      pattern '[0-9a-zA-Z\-:@_]*';
    }
    description
      "Type for a resource ID that are used to reference an ALTO
       information resource.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 9.1.1";
  }

  typedef cost-type-name {
    type string {
      length "1..max";
    }
    description
      "Type for the name of a single CostType that can be
       referenced by other ALTO information resources.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 9.2.2";
  }

  typedef meta-key {
    type string {
      length "1..max";
    }
    description
      "Type for a custom meta key of an ALTO server.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 8.4.1";
  }

  typedef endpoint-property {
    type union {
      type resource-specific-endpoint-property;
      type global-endpoint-property;
    }
    description
      "Type for an endpoint property.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 10.8";
  }

  typedef resource-specific-endpoint-property {
    type string {
      length "1..97";
      pattern '[0-9a-zA-Z\-:@_]*\.[0-9a-zA-Z\-:_]*';
    }
    description
      "Type for a resource-specific endpoint property.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 10.8.1";
  }

  typedef global-endpoint-property {
    type string {
      length "1..32";
      pattern '[0-9a-zA-Z\-:_]*';
    }
    description
      "Type for a global endpoint property.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 10.8.2";
  }

  typedef source-id {
    type string {
      length "1..max";
    }
    description
      "Type for a data source ID that are used to reference a data
       source.";
  }

  typedef role-name {
    type string {
      length "1..max";
    }
    description
      "Type for a name of a role for role-based access control.";
  }

  // Typedefs for referencing purposes

  typedef cost-type-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:cost-type"
         + "/alto:cost-type-name";
    }
    description
      "Type to reference a cost type name.";
  }

  typedef data-source-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:data-source"
         + "/alto:source-id";
    }
    description
      "Type to reference a data source identifier.";
  }

  typedef http-user-id-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:listen"
         + "/alto:http/alto:http-server-parameters"
         + "/alto:client-authentication/alto:users"
         + "/alto:user/alto:user-id";
    }
    description
      "Type to reference an HTTP client user id.";
  }

  typedef https-user-id-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:listen"
         + "/alto:https/alto:http-server-parameters"
         + "/alto:client-authentication/alto:users"
         + "/alto:user/alto:user-id";
    }
    description
      "Type to reference an HTTPS client user id.";
  }

  typedef inline-ca-cert-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:listen"
         + "/alto:https/alto:tls-server-parameters"
         + "/alto:client-authentication/alto:ca-certs"
         + "/alto:inline-definition/alto:certificate"
         + "/alto:name";
    }
    description
      "Type to reference a TLS CA certificate.";
  }

  typedef inline-ee-cert-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:listen"
         + "/alto:https/alto:tls-server-parameters"
         + "/alto:client-authentication/alto:ee-certs"
         + "/alto:inline-definition/alto:certificate"
         + "/alto:name";
    }
    description
      "Type to reference a TLS EE certificate.";
  }

  typedef inline-raw-public-key-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:listen"
         + "/alto:https/alto:tls-server-parameters"
         + "/alto:client-authentication/alto:raw-public-keys"
         + "/alto:inline-definition/alto:public-key"
         + "/alto:name";
    }
    description
      "Type to reference a raw pubic key.";
  }

  typedef resource-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:resource"
         + "/alto:resource-id";
    }
    description
      "Type to reference a resource identifier.";
  }

  typedef role-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:role"
         + "/alto:role-name";
    }
    description
      "Type to reference a role.";
  }

  typedef client-ref {
    type leafref {
      path "/alto:alto/alto:alto-server/alto:auth-client"
         + "/alto:client-id";
    }
    description
      "Type to reference an authenticated client.";
  }

  // Groupings

  grouping filter-costmap-cap {
    description
      "This grouping defines a data model for
       FilteredCostMapCapabilities.";
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 11.3.2.4";
    leaf-list cost-type-name {
      type cost-type-ref;
      min-elements 1;
      description
        "Supported cost types.";
    }
    leaf cost-constraints {
      type boolean;
      default false;
      description
        "If set to true, then the ALTO server allows cost
         constraints to be included in requests to the
         corresponding URI.";
    }
    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 and can return a
         multi-cost map with any combination of N or
         fewer cost types in the 'cost-type-names' list.";
    }
    leaf-list testable-cost-type-name {
      if-feature "multi-cost";
      type cost-type-ref;
      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";
      description
        "Configuration for CalendarAttributes.";
      reference
        "RFC 8896: Application-Layer Traffic Optimization (ALTO)
                   Cost Calendar, Section 4.1";
      leaf-list cost-type-name {
        type cost-type-ref;
        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;
        }
        units "seconds";
        mandatory true;
        description
          "The duration of an ALTO Calendar time interval.";
      }
      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.";
      }
    }
  }

  grouping algorithm {
    description
      "This grouping defines the base data model for information
       resource creation algorithm.";
    choice algorithm {
      mandatory true;
      description
        "Information resource creation algorithm to be augmented.";
    }
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer Traffic
                 Optimization (ALTO) Protocol, Section 5.4.2";
  }

  grouping alto-server {
    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 {
    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;
          }
        }
      }
      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 alto-server-discovery {
    description
      "Grouping for the configuration of how to set up server
       discovery for clients or other ALTO servers to discovery the
       URI of this ALTO server.";
    choice method {
      description
        "Selects among available server discovery methods.";
      case reverse-dns {
        if-feature "xdom-disc";
        description
          "Configures DNS NAPTR records for cross-domain ALTO server
           discovery using reverse DNS lookup.";
        reference
          "RFC 8686: Application-Layer Traffic Optimization (ALTO)
                     Cross-Domain Server Discovery.";
        container rdns-naptr-records {
          description
            "Configuration parameters for DNS NAPTR records.";
          leaf-list static-prefix {
            type inet:ip-prefix;
            description
              "Specifies a list of static IP prefixes.";
          }
          leaf-list dynamic-prefix-source {
            type data-source-ref;
            description
              "Dynamic IP prefixes collected from data sources.";
          }
        }
      }
    }
  }

  grouping alto-server-discovery-client {
    description
      "Grouping for configuration of how a client can discover
       an ALTO server.";
    choice method {
      description
        "Selects among available server discovery methods.";
      case reverse-dns {
        if-feature "xdom-disc";
        description
          "Uses reverse DNS lookup to discover an ALTO server.";
        reference
          "RFC 8686: Application-Layer Traffic Optimization (ALTO)
                     Cross-Domain Server Discovery.";
        container rdns-params {
          description
            "Defines a set of parameters for reverse DNS
             lookups.";
          leaf-list dns-server {
            type inet:host;
            description
              "Provides a DNS server list for reverse DNS lookup.";
          }
        }
      }
    }
  }

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

  grouping inline-or-truststore-ca-cert-ref {
    description
      "Grouping for the reference of a CA certificate to
       authenticate the TLS client.";
    choice inline-or-truststore {
      description
        "Selects between inline and truststore";
      case inline {
        if-feature "ts:inline-definitions-supported";
        leaf inline {
          type inline-ca-cert-ref;
          description
            "Reference to an inline CA certificate configured by
             the TLS server.";
        }
        description
          "Reference of an inline CA certificate to authenticate
           the TLS client.";
      }
      case central-truststore {
        if-feature "ts:central-truststore-supported";
        if-feature "ts:certificates";
        uses ts:certificate-ref-grouping;
        description
          "Reference of a CA certificate in the truststore to
           authenticate the TLS client.";
      }
    }
  }

  grouping inline-or-truststore-ee-cert-ref {
    description
      "Grouping for the reference of a EE certificate to
       authenticate the TLS client.";
    choice inline-or-truststore {
      description
        "Selects between inline and truststore";
      case inline {
        if-feature "ts:inline-definitions-supported";
        leaf inline {
          type inline-ee-cert-ref;
          description
            "Reference to an inline EE certificate configured by
             the TLS server.";
        }
        description
          "Reference of an inline EE certificate to authenticate
           the TLS client.";
      }
      case central-truststore {
        if-feature "ts:central-truststore-supported";
        if-feature "ts:certificates";
        uses ts:certificate-ref-grouping;
        description
          "Reference of a EE certificate in the truststore to
           authenticate the TLS client.";
      }
    }
  }

  grouping inline-or-truststore-public-key-ref {
    description
      "Grouping for the reference of a raw public key to
       authenticate the TLS client.";
    choice inline-or-truststore {
      description
        "Selects between inline and truststore";
      case inline {
        if-feature "ts:inline-definitions-supported";
        leaf inline {
          type inline-raw-public-key-ref;
          description
            "Reference to an inline public key configured by the
             TLS server.";
        }
        description
          "Reference of an inline public key to authenticate the
           TLS client.";
      }
      case central-truststore {
        if-feature "ts:central-truststore-supported";
        if-feature "ts:public-keys";
        uses ts:public-key-ref-grouping;
        description
          "Reference of a raw public key in the truststore to
           authenticate the TLS client.";
      }
    }
  }

  // Top-level container

  container alto {
    presence "The ALTO service is enabled";
    description
      "Indicates a set of parameters for both ALTO clients and
       servers. A single device can implement either alto-client or
       alto-server. No need to implement both.";
    list alto-client {
      if-feature alto-client;
      key "client-id";
      description
        "The ALTO client configuration.";
      leaf client-id {
        type string;
        description
          "A unique identifier of a client that can be referenced
           by a data source or a resource creation algorithm to
           communicate with other ALTO servers.";
      }
      container server-discovery {
        description
          "Specifies a set of parameters for ALTO server discovery.";
        uses alto-server-discovery-client;
      }
    }
    container alto-server {
      if-feature alto-server;
      description
        "The ALTO server instance configuration.";
      container listen {
        description
          "Configure the ALTO server to listen for ALTO clients.";
        uses alto-server-listen-stack;
      }
      container server-discovery {
        description
          "Configures how the ALTO server to be discovered by
           others.";
        uses alto-server-discovery;
      }
      container logging-system {
        description
          "Configure logging system to capture log messages
           generated by the ALTO server.";
        uses alto-logging-system;
      }
      list cost-type {
        key "cost-type-name";
        description
          "Mapping between name and referenced cost type.";
        leaf cost-type-name {
          type cost-type-name;
          description
            "The name to reference a 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.";
        }
        leaf description {
          type string;
          description
            "A human-readable description fo the 'cost-mode' and
             'cost-metric'.";
        }
        container cost-context {
          if-feature "performance-metrics";
          description
            "Context of how the metric is obtained.";
          leaf cost-source {
            type identityref {
              base cost-source;
            }
            mandatory true;
            description
              "The referenced cost source.";
          }
          container parameters {
            description
              "Additional computation parameters for the cost
               source.";
            choice parameters {
              description
                "Cases of parameters to be augmented.";
            }
          }
        }
      }
      list meta {
        key "meta-key";
        description
          "Mapping of custom meta information";
        reference
          "RFC 7285: Application-Layer Traffic Optimization
                     (ALTO) Protocol, Section 8.4.1";
        leaf meta-key {
          type meta-key;
          description
            "Custom meta key";
        }
        leaf meta-value {
          type binary;
          mandatory true;
          description
            "Custom meta value encoded with the base64 encoding
             schema. The encoded value must be a valid JSON
             value.";
        }
      }
      list auth-client {
        key "client-id";
        description
          "List of authenticated ALTO clients.";
        leaf client-id {
          type string;
          description
            "Identifier to reference an ALTO client.";
        }
        choice authentication {
          description
            "Choice of authentication methods to identify this
             ALTO client. If no authentication method is
             configured, the client must be ignored.";
          case http {
            description
              "The client is authenticated by the HTTP server.";
            container http-auth-client {
              if-feature "http-listen";
              if-feature "http:client-auth-supported";
              if-feature "http:local-users-supported";
              description
                "Parameters of the authenticated HTTP client.";
              leaf user-id {
                type http-user-id-ref;
                mandatory true;
                description
                  "Reference of the user-id for the authenticated
                   HTTP client.";
              }
            }
          }
          case https {
            description
              "The client is authenticated by the HTTP server.";
            container https-auth-client {
              if-feature "http:client-auth-supported";
              if-feature "http:local-users-supported";
              description
                "Parameters to identify an authenticated HTTPS
                 client.";
              leaf user-id {
                type https-user-id-ref;
                description
                  "Reference of the user-id for the authenticated
                   HTTPS client.";
              }
            }
            container tls-auth-client {
              if-feature "tls:client-auth-supported";
              description
                "Parameters to identify na authenticated TLS
                 client.";
              container ca-cert {
                if-feature "tls:client-auth-x509-cert";
                description
                  "Reference of the CA certificate to authenticate
                   the TLS client.";
                uses inline-or-truststore-ca-cert-ref;
              }
              container ee-cert {
                if-feature "tls:client-auth-x509-cert";
                description
                  "Reference of the EE certificate to authenticate
                   the TLS client.";
                uses inline-or-truststore-ee-cert-ref;
              }
              container raw-public-key {
                if-feature "tls:client-auth-raw-public-key";
                description
                  "Reference of the raw public key to authenticate
                   the TLS client.";
                uses inline-or-truststore-public-key-ref;
              }
              leaf tls12-psks {
                if-feature "tls:client-auth-tls12-psk";
                type empty;
                description
                  "Identicate that the client is authenticated by
                   the TLS server using the configured PSKs
                   (pre-shared or pairwise-symmetric keys).";
              }
              leaf tls13-epsks {
                if-feature "tls:client-auth-tls13-epsk";
                type empty;
                description
                  "Identicate that the client is authenticated by
                   the TLS 1.3 server using the configured external
                   PSKs (pre-shared keys).";
              }
            }
          }
        }
      }
      list role {
        key "role-name";
        description
          "List of roles for access control.";
        leaf role-name {
          type role-name;
          description
            "Name of a role for access control.";
        }
        leaf-list client {
          type client-ref;
          description
            "List of authenticated ALTO clients assigned to the
             role.";
        }
      }
      list data-source {
        key "source-id";
        description
          "List of subscribed data sources.";
        leaf source-id {
          type source-id;
          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.";
        }
        container source-params {
          description
            "Data source specific configuration.";
          reference
            "RFC XXXX: YANG Data Models for the Application-Layer
                       Traffic Optimization (ALTO) Protocol,
                       Section 5.4.1";
        }
      }
      list resource {
        key "resource-id";
        description
          "ALTO information resources to be defined";
        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-role {
          type role-ref;
          description
            "Roles allowed to access this information resource.";
        }
        leaf-list dependency {
          type resource-ref;
          description
            "A list of dependent information resources.";
        }
        container alto-ird-params {
          when 'derived-from-or-self(../resource-type,'
             + '"alto:ird")';
          description
            "IRD-specific configuration.";
          leaf delegation {
            type inet:uri;
            mandatory true;
            description
              "Upstream IRD to be delegated.";
          }
        }
        container alto-networkmap-params {
          when 'derived-from-or-self(../resource-type,'
             + '"alto:network-map")';
          description
            "Filtered Network Map specific configuration.";
          reference
            "RFC 7285: Application-Layer Traffic Optimization
                       (ALTO) Protocol, Sections 11.2.1 and
                       11.3.1";
          leaf is-default {
            type boolean;
            description
              "Sets whether this is the default network map.";
          }
          leaf filtered {
            type boolean;
            default false;
            description
              "Configures whether filtered network map is
               supported.";
          }
          uses algorithm;
        }
        container alto-costmap-params {
          when 'derived-from-or-self(../resource-type,'
             + '"alto:cost-map")';
          description
            "Filtered Cost Map specific configuration.";
          reference
            "RFC 7285: Application-Layer Traffic Optimization
                       (ALTO) Protocol, Sections 11.2.2 and
                       11.3.2";
          leaf filtered {
            type boolean;
            description
              "Configures whether filtered cost map is supported.";
          }
          uses filter-costmap-cap;
          uses algorithm;
        }
        container alto-endpointcost-params {
          when 'derived-from-or-self(../resource-type,'
             + '"alto:endpoint-cost")';
          description
            "Endpoint Cost Service specific configuration.";
          reference
            "RFC 7285: Application-Layer Traffic Optimization
                       (ALTO) Protocol, Section 11.5";
          uses filter-costmap-cap;
          uses algorithm;
        }
        container alto-endpointprop-params {
          when 'derived-from-or-self(../resource-type,'
             + '"alto:endpoint-prop")';
          description
            "Endpoint Cost Service specific configuration.";
          reference
            "RFC 7285: Application-Layer Traffic Optimization
                       (ALTO) Protocol, Section 11.5";
          leaf-list prop-type {
            type endpoint-property;
            min-elements 1;
            description
              "Supported endpoint properties.";
          }
          uses algorithm;
        }
        container alto-propmap-params {
          when 'derived-from-or-self(../resource-type,'
             + '"alto:property-map")';
          if-feature "propmap";
          description
            "(Filtered) Entity Property Map specific
             configuration.";
          reference
            "RFC 9240: An ALTO Extension: Entity Property Maps";
          uses algorithm;
        }
        container alto-cdni-params {
          when 'derived-from-or-self(../resource-type,'
             + '"alto:cdni")';
          if-feature "cdni";
          description
            "CDNi specific configuration.";
          reference
            "RFC 9241: Content Delivery Network Interconnection
                       (CDNI) Request Routing: CDNI Footprint and
                       Capabilities Advertisement using ALTO";
          uses algorithm;
        }
        container alto-update-params {
          when 'derived-from-or-self(../resource-type,'
             + '"alto:update")';
          if-feature "incr-update";
          description
            "Incremental Updates specific configuration.";
          reference
            "RFC 8895: Application-Layer Traffic Optimization
                       (ALTO) Incremental Updates Using Server-Sent
                       Events (SSE)";
          uses algorithm;
        }
        container resource-limits {
          description
            "Sets resource limits.";
          leaf notify-res-mem-limit {
            type uint64;
            units "bytes";
            description
              "Notification of resource memory usage.

               Notification must be generated when the defined
               threshold is reached.";
          }
          leaf notify-upd-stream-limit {
            when 'derived-from-or-self(../../resource-type,'
               + '"alto:update")';
            if-feature "incr-update";
            type uint64;
            description
              "Notification of number of active update streams.

               Notification must be generated when the defined
               threshold is reached.";
          }
        }
      }
    }
  }

  // Notifications

  notification alto-resource-event {
    if-feature alto-server;
    description
      "Notifications must be generated when notify-res-mem-limit
       and/or notify-upd-stream-limit thresholds are reached.";
    leaf resource-id {
      type resource-ref;
      mandatory true;
      description
        "Resource identifier.";
    }
    leaf notify-res-mem-threshold {
      type uint64;
      units "bytes";
      description
        "The notify-res-mem-limit threshold has been fired.";
    }
    leaf notify-upd-stream-threshold {
      if-feature "incr-update";
      type uint64;
      description
        "The notify-upd-stream-limit threshold has been fired.";
    }
  }
}

<CODE ENDS>

7.2. The "ietf-alto-stats" YANG Module

<CODE BEGINS> file "ietf-alto-stats@2023-02-23.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, Section 3";
  }
  import ietf-alto {
    prefix alto;
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (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 a set of statistics of an ALTO
     server instance.

     Copyright (c) 2023 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 2023-02-23 {
    description
      "Initial Version.";
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

  // Groupings

  grouping server-level-stats {
    description
      "This grouping defines statistics for server-level
       monitoring.";
    leaf discontinuity-time {
      type yang:timestamp;
      description
        "The time on the most recent occasion at which the ALTO
         server suffered a discontinuity. This must be initialized
         when the ALTO server is configured or rebooted.";
    }
    leaf last-report-time {
      type yang:timestamp;
      description
        "The time on the most recent occasion at which the
         statistics were reported.";
    }
    leaf num-total-req {
      type yang:counter64;
      description
        "The total number of ALTO requests received by the ALTO
         server.";
    }
    leaf num-total-succ {
      type yang:counter64;
      description
        "The total number of successful responses sent by the ALTO
         server.";
    }
    leaf num-total-fail {
      type yang:counter64;
      description
        "The total number of failed responses sent by the ALTO
         server.";
    }
    leaf num-total-last-req {
      type yang:gauge64;
      description
        "The total number of ALTO requests received by the ALTO
         server within the last time window. The duration of the
         time window is configured by time-window-size parameter.";
    }
    leaf num-total-last-succ {
      type yang:gauge64;
      description
        "The total number of successful responses sent by the ALTO
         server within the last time window. The duration of the
         time window is configured by time-window-size parameter.";
    }
    leaf num-total-last-fail {
      type yang:gauge64;
      description
        "The total number of failed responses sent by the ALTO
         server within the last time window. The duration of the
         time window is configured by time-window-size parameter.";
    }
  }

  grouping network-map-stats {
    description
      "This grouping defines resource-specific statstics for the
       network map service only.";
    leaf num-map-pid {
      type yang:gauge64;
      description
        "Number of PIDs contained in the network map.";
    }
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 5";
  }

  grouping prop-map-stats {
    description
      "This grouping defines resource-specific statstics for the
       endpoint property or property map service only.";
    leaf num-map-entry {
      type yang:gauge64;
      description
        "Number of ALTO entities contained in the property map.";
    }
    reference
      "RFC 7285: Application-Layer Traffic Optimization (ALTO)
                 Protocol, Section 11.4.1
       RFC 9240: An ALTO Extension: Entity Property Maps";
  }

  grouping cdni-stats {
    description
      "This grouping defines resource-specific statstics for the
       CDNI advertisement service only.";
    leaf num-base-obj {
      type yang:gauge64;
      description
        "Number of base CDNi advertisement objects contained in the
         CDNI resource.";
    }
    reference
      "RFC 9241: Content Delivery Network Interconnection (CDNI)
                 Request Routing: CDNI Footprint and Capabilities
                 Advertisement using ALTO";
  }

  grouping upd-stream-stats {
    description
      "This grouping defines resource-specific statstics for the
       update stream service only.";
    leaf num-upd-stream {
      type yang:gauge64;
      description
        "Number of active update streams connected to the update
         stream service.";
    }
    leaf num-upd-msg-total {
      type yang:gauge64;
      description
        "Total number of update messages sent to all the active
         update streams.";
    }
    leaf num-upd-msg-max {
      type yang:gauge64;
      description
        "The maximum value over the total number of update messages
         sent to each active update stream. Assume there are 3
         active update streams A, B, and C with 4, 3, and 2 update
         messages sent to them respectively, the value of this
         metric is 4. After a while, if there is no new update
         message sent to any update stream, but the update stream A
         is closed, then the value of this metric is updated to
         3.";
    }
    leaf num-upd-msg-min {
      type yang:gauge64;
      description
        "The minimum value over the total number of update messages
         sent to each active update stream. The procedure is similar
         to num-msg-max.";
    }
    leaf num-upd-msg-avg {
      type yang:gauge64;
      description
        "The average value over the total number of update messages
         sent to each active update stream. The procedure is similar
         to num-msg-max.";
    }
    leaf num-upd-msg-total-last {
      type yang:gauge64;
      description
        "Total number of update messages sent to all the active
         update streams within the last time window. The duration
         of the time window is configured by time-window-size
         parameter.";
    }
    leaf num-upd-msg-max-last {
      type yang:gauge64;
      description
        "The maximum value over the number of update messages sent
         to each active update stream within the last time window.
         The procedure is similar to num-msg-max, but only count
         the update messages within the last time window. The
         duration of the time window is configured by
         time-window-size parameter.";
    }
    leaf num-upd-msg-min-last {
      type yang:gauge64;
      description
        "The minimal value over the number of update messages sent
         to each active update stream within the last time window.
         The procedure is similar to num-msg-max, but only count
         the update messages within the last time window. The
         duration of the time window is configured by
         time-window-size parameter.";
    }
    leaf num-upd-msg-avg-last {
      type yang:gauge64;
      description
        "The average value over the number of update messages sent
         to each active update stream within the last time window.
         The procedure is similar to num-msg-max, but only count
         the update messages within the last time window. The
         duration of the time window is configured by
         time-window-size parameter.";
    }
    reference
      "RFC 8895: Application-Layer Traffic Optimization (ALTO)
                 Incremental Updates Using Server-Sent Events
                 (SSE)";
  }

  grouping resource-level-stats {
    description
      "This grouping defines statistics for resource-level
       monitoring.";
    leaf discontinuity-time {
      type yang:timestamp;
      description
        "The time on the most recent occasion at which the ALTO
         service providing the information resource suffered a
         discontinuity. This must be initialized when the ALTO
         information resource is configured or the ALTO server is
         rebooted.";
    }
    leaf last-report-time {
      type yang:timestamp;
      description
        "The time on the most recent occasion at which the
         statistics are reported.";
    }
    leaf num-res-upd {
      type yang:counter64;
      description
        "The number of version updates since the information
         resource was created.";
    }
    leaf res-mem-size {
      type uint64;
      units "bytes";
      description
        "Memory size utilized by the information resource.";
    }
    leaf res-enc-size {
      type uint64;
      units "bytes";
      description
        "Size of JSON encoded data of the information resource.";
    }
    leaf num-res-req {
      type yang:counter64;
      description
        "The total number of ALTO requests to this information
         resource.";
    }
    leaf num-res-succ {
      type yang:counter64;
      description
        "The total number of successful responses for requests to
         this information resource.";
    }
    leaf num-res-fail {
      type yang:counter64;
      description
        "The total number of failed responses for requests to this
         information resource.";
    }
    leaf num-res-last-req {
      type yang:gauge64;
      description
        "The number of ALTO requests to this information resource
         within the last time window. The duration of the time
         window is configured by time-window-size parameter.";
    }
    leaf num-res-last-succ {
      type yang:gauge64;
      description
        "The number of successful responses for requests to this
         information resource within the last time window. The
         duration of the time window is configured by
         time-window-size parameter.";
    }
    leaf num-res-last-fail {
      type yang:gauge64;
      description
        "The number of failed responses for requests to this
         information resource within the last time window. The
         duration of the time window is configured by
         time-window-size parameter.";
    }
    container network-map-stats {
      when 'derived-from-or-self(../../alto:resource-type,'
         + '"alto:network-map")';
      description
        "Resource-specific statistics for network map
         service only.";
      uses network-map-stats;
    }
    container endpoint-prop-stats {
      when 'derived-from-or-self(../../alto:resource-type,'
         + '"alto:endpoint-prop")';
      description
        "Resource-specific statistics for endpoint property
         service only.";
      uses prop-map-stats;
    }
    container property-map-stats {
      when 'derived-from-or-self(../../alto:resource-type,'
         + '"alto:property-map")';
      description
        "Resource-specific statistics for entity property map
         service only.";
      uses prop-map-stats;
    }
    container cdni-stats {
      when 'derived-from-or-self(../../alto:resource-type,'
         + '"alto:cdni")';
      description
        "Resource-specific statistics for CDNI advertisement
         service only.";
      uses cdni-stats;
    }
    container upd-stream-stats {
      when 'derived-from-or-self(../../alto:resource-type,'
         + '"alto:update")';
      description
        "Resource-specific statistics for update stream service
         only.";
      uses upd-stream-stats;
    }
  }

  // Augment modules to add statistics

  augment "/alto:alto/alto:alto-server" {
    description
      "Augmenting statistics and configuration parameters for
       server-level monitoring.";
    container server-level-monitor-config {
      description
        "Configuration parameters for server-level monitoring.";
      leaf time-window-size {
        type uint32;
        units "seconds";
        default "300";
        description
          "Duration of the time window within that the statistics
           are reported.";
      }
    }
    container server-level-stats {
      config false;
      description
        "Top-level statistics for the whole ALTO server.";
      uses server-level-stats;
    }
  }

  augment "/alto:alto/alto:alto-server/alto:resource" {
    description
      "Augmenting statistics and configuration parameters for
       resource-level monitoring.";
    container resource-level-stats {
      config false;
      description
        "Common statistics for each information resource.";
      uses resource-level-stats;
    }
  }
}

<CODE ENDS>

10. References

10.1. Normative References

[I-D.ietf-netconf-http-client-server]: Watsen, K., "YANG Groupings for HTTP 1.1/2.0 Clients and HTTP Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-http-client-server-14, 28 December 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-http-client-server-14>.
[I-D.ietf-netconf-netconf-client-server]: Watsen, K., "NETCONF Client and Server Models", Work in Progress, Internet-Draft, draft-ietf-netconf-netconf-client-server-30, 28 December 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-netconf-client-server-30>.
[I-D.ietf-netconf-restconf-client-server]: Watsen, K., "RESTCONF Client and Server Models", Work in Progress, Internet-Draft, draft-ietf-netconf-restconf-client-server-30, 28 December 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-restconf-client-server-30>.
[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-17, 28 December 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-tcp-client-server-17>.
[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-34, 28 December 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-tls-client-server-34>.
[I-D.ietf-netconf-trust-anchors]: Watsen, K., "A YANG Data Model for a Truststore", Work in Progress, Internet-Draft, draft-ietf-netconf-trust-anchors-22, 28 December 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-trust-anchors-22>.
[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>.
[RFC5424]: Gerhards, R., "The Syslog Protocol", RFC 5424, DOI 10.17487/RFC5424, March 2009, <https://www.rfc-editor.org/rfc/rfc5424>.
[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>.
[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/rfc/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/rfc/rfc6242>.
[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>.
[RFC8040]: Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, <https://www.rfc-editor.org/rfc/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/rfc/rfc8174>.
[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>.
[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/rfc/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/rfc/rfc8342>.
[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/rfc/rfc8446>.
[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>.
[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>.
[RFC9274]: Boucadair, M. and Q. Wu, "A Cost Mode Registry for the Application-Layer Traffic Optimization (ALTO) Protocol", RFC 9274, DOI 10.17487/RFC9274, July 2022, <https://www.rfc-editor.org/rfc/rfc9274>.
[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>.
[RFC9439]: Wu, Q., Yang, Y., Lee, Y., Dhody, D., Randriamasy, S., and L. Contreras, "Application-Layer Traffic Optimization (ALTO) Performance Cost Metrics", RFC 9439, DOI 10.17487/RFC9439, August 2023, <https://www.rfc-editor.org/rfc/rfc9439>.

10.2. Informative References

[I-D.ietf-alto-new-transport]: Gao, K., Schott, R., Yang, Y. R., Delwiche, L., and L. Keller, "The ALTO Transport Information Publication Service", Work in Progress, Internet-Draft, draft-ietf-alto-new-transport-22, 3 January 2024, <https://datatracker.ietf.org/doc/html/draft-ietf-alto-new-transport-22>.
[RFC6291]: Andersson, L., van Helvoort, H., Bonica, R., Romascanu, D., and S. Mansfield, "Guidelines for the Use of the "OAM" Acronym in the IETF", BCP 161, RFC 6291, DOI 10.17487/RFC6291, June 2011, <https://www.rfc-editor.org/rfc/rfc6291>.
[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>.
[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>.
[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>.
[RFC8641]: Clemm, A. and E. Voit, "Subscription to YANG Notifications for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641, September 2019, <https://www.rfc-editor.org/rfc/rfc8641>.

Appendix A. Examples of Extending the ALTO O&M Data Model

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

The server-discovery-manner choice of the server-discovery.¶
The authentication choice of each auth-client.¶
The data-source node.¶
The algorithm choice of the resource-params of each resource.¶

A.1. An Example Module for Extended Server Discovery Manners

The base module "ietf-alto" only includes a reverse DNS based server discovery manner. The following example module demonstrates how additional server discovery methods can be augmented into the base data model.¶

The case internet-routing-registry allows the ALTO server to update the server URI to the attribute of the corresponding aut-num class in IRR.¶

The case peeringdb allows the ALTO server to update the server URI to the org object of the organization record in PeeringDB.¶

module example-alto-server-discovery {
  yang-version 1.1;

  namespace "https://example.com/ns/example-alto-server-discovery";
  prefix ex-alto-disc;

  import ietf-alto {
    prefix alto;
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

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

  organization
    "Example, Inc.";

  contact
    "Example, Inc.
     Customer Service

     E-mail: alto-oam-yang@example.com";

  description
    "This module contains a collection of vendor-specific cases of
     server discovery mechanisms for ALTO.";

  revision 2023-02-28 {
    description
      "Version 1.0";
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

  augment "/alto:alto/alto:alto-server/alto:server-discovery"
        + "/alto:method" {
    description
      "Examples of server discovery mechanisms provided by the ALTO
       server.";
    case internet-routing-registry {
      description
        "Update descr attributes of an aut-num class in an Internet
         Routing Registry (IRR) database for ALTO server discovery
         using Routing Policy Specification Language (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) number 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
            "Specifies an identifier that refers to the org object
             of the organization record in PeeringDB.";
        }
      }
    }
  }

  augment "/alto:alto/alto:alto-client"
        + "/alto:server-discovery/alto:method" {
    description
      "Examples of server discovery mechanisms used by an ALTO
       client.";
    case internet-routing-registry {
      description
        "Use IRR to discover an ALTO server.";
      reference
        "RFC 2622: Routing Policy Specification Language (RPSL).";
      container irr-params {
        description
          "Configuration for IRR query using RPSL.";
        leaf whois-server {
          type inet:host;
          description
            "Whois server for an IRR query using RPSL.";
        }
      }
    }
    case peeringdb {
      description
        "Use PeeringDB to discover an ALTO server.";
      container peeringdb-params {
        description
          "Configuration for PeeringDB queries.";
        leaf peeringdb-endpoint {
          type inet:uri;
          description
            "Endpoint of PeeringDB API server.";
        }
      }
    }
  }
}

A.2. An Example Module for Extended Client Authentication Approaches

The base module "ietf-alto" only includes the client authentication approaches directly provided by the HTTP server. However, an implementation may authenticate clients in different ways. For example, an implementation may delegate the authentication to a third-party OAuth 2.0 server. The following example module demonstrates how additional client authentication approaches can enrich the base data model.¶

In this example, the oauth2 case includes the URI to a third-party OAuth 2.0 based authorization server that the ALTO server can redirect to for the client authentication.¶

module example-alto-auth {
  yang-version 1.1;

  namespace "https://example.com/ns/example-alto-auth";
  prefix ex-alto-auth;

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

  import ietf-alto {
    prefix alto;
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

  organization
    "Example, Inc.";

  contact
    "Example, Inc.
     Customer Service

     E-mail: alto-oam-yang@example.com";

  description
    "This module contains a collection of vendor-specific cases of
     client authentication approaches for ALTO.";

  revision 2023-02-28 {
    description
      "Version 1.0";
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

  augment "/alto:alto/alto:alto-server/alto:auth-client"
        + "/alto:authentication" {
    description
      "Example of extended ALTO client authentication approaches.";
    case oauth2 {
      description
        "Example of authentication by a third-party OAuth 2.0
         server.";
      container oauth2 {
        description
          "Parameters for authentication by a third-party OAuth 2.0
           server.";
        leaf oauth2-server {
          type inet:uri;
          description
            "The URI to the authorization server.";
        }
      }
    }
  }
}

A.3. Example Module for Extended Data Sources

The base module "ietf-alto" 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 datastore. It includes:¶

datastore to indicate which datastore is fetched.¶
target-paths to specify the list of nodes or subtrees in the datastore.¶
protocol to indicate which protocol is used to access the datastore. Either restconf or netconf can be used.¶

module example-alto-data-source {
  yang-version 1.1;

  namespace "https://example.com/ns/example-alto-data-source";
  prefix ex-alto-ds;

  import ietf-alto {
    prefix alto;
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

  import ietf-datastores {
    prefix ds;
    reference
      "RFC 8342: Network Management Datastore Architecture (NMDA)";
  }

  import ietf-yang-push {
    prefix yp;
    reference
      "RFC 8641: Subscription to YANG Notifications for Datastore
                 Updates";
  }

  import ietf-netconf-client {
    prefix ncc;
    reference
      "RFC HHHH: NETCONF Client and Server Models";
  }

  import ietf-restconf-client {
    prefix rcc;
    reference
      "RFC IIII: YANG Groupings for RESTCONF Clients and RESTCONF
                 Servers";
  }

  organization
    "Example, Inc.";

  contact
    "Example, Inc.
     Customer Service

     E-mail: alto-oam-yang@example.com";

  description
    "This module contains a collection of vendor-specific cases of
     data sources for ALTO.";

  revision 2023-02-28 {
    description
      "Version 1.0";
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

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

  identity protocol-type {
    description
      "Base identity for protocol type.";
  }

  identity netconf {
    base protocol-type;
    description
      "Identity for NETCONF protocol.";
  }

  identity restconf {
    base protocol-type;
    description
      "Identity for RESTCONF protocol.";
  }

  augment "/alto:alto/alto:alto-server/alto:data-source"
        + "/alto:source-params" {
    when 'derived-from-or-self(../alto:source-type,'
       + '"yang-datastore")';
    description
      "Example data source for local or remote YANG datastore.";
    container yang-datastore-source-params {
      description
        "YANG datastore specific configuration.";
      leaf datastore {
        type ds:datastore-ref;
        mandatory true;
        description
          "Reference of the datastore from which to get data.";
      }
      list target-paths {
        key name;
        description
          "XML Path Language (XPath) to subscribed YANG datastore
           node or subtree.";
        leaf name {
          type string;
          description
            "Name of the supported XPath or subtree filters.";
        }
        uses yp:selection-filter-types;
      }
      leaf protocol {
        type identityref {
          base protocol-type;
        }
        description
          "Indicates the protocol that is used to access the YANG
           datastore.";
      }
      container restconf {
        uses rcc:restconf-client-app-grouping {
          when 'derived-from-or-self(../protocol, "restconf")';
        }
        description
          "Parameters for the RESTCONF endpoint of the YANG
           datastore.";
      }
      container netconf {
        uses ncc:netconf-client-app-grouping {
          when 'derived-from-or-self(../protocol, "netconf")';
        }
        description
          "Parameters for the NETCONF endpoint of the YANG
           datastore.";
      }
    }
  }
}

A.4. An Example Module for Information Resource Creation Algorithm

The base module "ietf-alto" does not include any choices cases for information resource creation algorithms. But developers may augment the "ietf-alto" module with definitions for 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-alto-alg

  augment /alto:alto/alto:alto-server/alto:resource
            /alto:alto-networkmap-params/alto:algorithm:
    +--:(l3-unicast-cluster)
       +--rw l3-unicast-cluster-algorithm
          +--rw l3-unicast-topo
          |  +--rw source-datastore    alto:data-source-ref
          |  +--rw topo-name?          leafref
          +--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 contains information referring to the target path name of an operational yang-datastore data source node (See Appendix A.3) subscribed in the data-source list (See Section 5.4.1). The referenced target path in the corresponding yang-datastore data source is assumed 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. 'source-datastore' refers to the 'source-id' of the operational yang-datastore data source node, and 'topo-name' refers to the 'name' of the target path in the source datastore.¶
'depth':: This optional parameter sets the depth of the clustering algorithm. For example, if the depth is set 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.¶

module example-alto-alg {
  yang-version 1.1;

  namespace "https://example.com/ns/example-alto-alg";
  prefix ex-alto-alg;

  import ietf-alto {
    prefix alto;
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

  import ietf-datastores {
    prefix ietf-datastores;
    reference
      "RFC 8342: Network Management Datastore Architecture (NMDA)";
  }

  import example-alto-data-source {
    prefix ex-alto-ds;
  }

  organization
    "Example, Inc.";

  contact
    "Example, Inc.
     Customer Service

     E-mail: alto-oam-yang@example.com";

  description
    "This module contains a collection of vendor-specific cases of
     information resource creation algorithms for ALTO.";

  revision 2023-02-28 {
    description
      "Version 1.0";
    reference
      "RFC XXXX: YANG Data Models for the Application-Layer
                 Traffic Optimization (ALTO) Protocol";
  }

  augment "/alto:alto/alto:alto-server/alto:resource"
        + "/alto:alto-networkmap-params/alto:algorithm" {
    description
      "Example of a network map creation algorithm.";
    case l3-unicast-cluster {
      description
        "Example algorithm translating a Layer 3 unicast topology
         of Interface to the Routing System (I2RS) to an ALTO
         network map.";
      container l3-unicast-cluster-algorithm {
        description
          "Parameters for l3-unicast-cluster algorithm.";
        container l3-unicast-topo {
          leaf source-datastore {
            type alto:data-source-ref;
            must 'deref(.)/../alto:source-params'
               + '/ex-alto-ds:yang-datastore-source-params'
               + '/ex-alto-ds:datastore '
               + '= "ietf-datastores:operational"'
               {
              error-message
                "The referenced YANG datastore MUST be
                 operational";
            }
            mandatory true;
            description
              "The data source to YANG datastore.";
          }
          leaf topo-name {
            type leafref {
              path '/alto:alto/alto:alto-server/alto:data-source'
                 + '[alto:source-id'
                 + ' = current()/../source-datastore]'
                 + '/alto:source-params'
                 + '/ex-alto-ds:yang-datastore-source-params'
                 + '/ex-alto-ds:target-paths/ex-alto-ds:name';
            }
            description
              "The name of the IETF Layer 3 unicast topology.";
          }
          description
            "The data source info to an IETF Layer 3 unicast
             topology.";
        }
        leaf depth {
          type uint32;
          description
            "The depth of the clustering.";
        }
      }
    }
  }
}

A.5. Example Usage

This section presents an example showing how the base data model and all the extended models above are used to set up an ALTO server and configure corresponding components (e.g., data source listener, information resource, and access control).¶

=============== NOTE: '\' line wrapping per RFC 8792 ================

{
  "ietf-alto:alto": {
    "alto-server": {
      "listen": {
        "https": {
          "tcp-server-parameters": {
            "local-address": "0.0.0.0"
          },
          "alto-server-parameters": {},
          "http-server-parameters": {
            "server-name": "alto.example.com",
            "client-authentication": {
              "users": {
                "user": [
                  {
                    "user-id": "alice",
                    "basic": {
                      "user-id": "alice",
                      "password": "$0$p8ssw0rd"
                    }
                  }
                ]
              }
            }
          },
          "tls-server-parameters": {
            "server-identity": {}
          }
        }
      },
      "server-discovery": {
        "example-alto-server-discovery:irr-params": {
          "aut-num": 64496
        }
      },
      "auth-client": [
        {
          "client-id": "alice",
          "https-auth-client": {
            "user-id": "alice"
          }
        },
        {
          "client-id": "bob",
          "example-alto-auth:oauth2": {
            "oauth2-server": "https://auth.example.com/login"
          }
        }
      ],
      "role": [
        {
          "role-name": "group0",
          "client": [
            "alice",
            "bob"
          ]
        }
      ],
      "data-source": [
        {
          "source-id": "test-yang-ds",
          "source-type": "example-alto-data-source:yang-datastore",
          "source-params": {
            "example-alto-data-source:yang-datastore-source-params"\
                                                                  : {
              "datastore": "ietf-datastores:operational",
              "target-paths": [
                {
                  "name": "network-topology",
                  "datastore-xpath-filter": "/network-topology:\
    network-topology/topology[topology-id=bgp-example-ipv4-topology]"
                }
              ],
              "protocol": "restconf",
              "restconf": {
                "listen": {
                  "endpoint": [
                    {
                      "name": "example restconf server",
                      "https": {
                        "tcp-server-parameters": {
                          "local-address": "192.0.2.2"
                        },
                        "http-client-parameters": {
                          "client-identity": {
                            "basic": {
                              "user-id": "carol",
                              "cleartext-password": "secret"
                            }
                          }
                        }
                      }
                    }
                  ]
                }
              }
            }
          }
        }
      ],
      "resource": [
        {
          "resource-id": "default-network-map",
          "resource-type": "network-map",
          "accepted-role": [
            "group0"
          ],
          "alto-networkmap-params": {
            "is-default": true,
            "example-alto-alg:l3-unicast-cluster-algorithm": {
              "l3-unicast-topo": {
                "source-datastore": "test-yang-ds",
                "topo-name": "network-topology"
              },
              "depth": 2
            }
          }
        }
      ]
    }
  }
}

Note that this example only uses a clear text password for demonstration purpose. In practice, it is NOT RECOMMENDED to use any clear text passwords when using this data model.¶