Internet-Draft ALTO O&M YANG July 2022
Zhang, et al. Expires 13 January 2023 [Page]
Workgroup:
ALTO WG
Internet-Draft:
draft-ietf-alto-oam-yang-01
Published:
Intended Status:
Standards Track
Expires:
Authors:
J. Zhang
Tongji University
D. Dhody
Huawei Technologies
K. Gao
Sichuan University
R. Schott
Deutsche Telekom

A Yang Data Model for OAM and Management of ALTO Protocol

Abstract

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

Discussion Venues

This note is to be removed before publishing as an RFC.

Discussion of this document takes place on the ALTO Working Group mailing list (alto@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/alto/.

Source for this draft and an issue tracker can be found at https://github.com/ietf-wg-alto/draft-alto-oam-yang.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 13 January 2023.

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Table of Contents

1. Introduction

This document defines a YANG data model for the Operations, Administration, and Maintenance (OAM) & Management of Application-Layer Traffic Optimization (ALTO) Protocol. The basic purpose of this YANG data model is discussed in Section 16 of [RFC7285]. The operator can use the data model to create and update ALTO information resources, manage the access control, configure server-to-server communication and server discovery, and collect statistical data.

The basic structure of this YANG data model is guided by Section 16 of [RFC7285] and [RFC7971]. Although the scope of the YANG data model in this document mainly focuses on the support of the base ALTO protocol [RFC7285] and the existing ALTO standard extensions (including [RFC8189], [RFC8895] and [RFC8896]), the design will also be extensible for future standard extensions (e.g., [I-D.ietf-alto-path-vector], [I-D.ietf-alto-unified-props-new], [I-D.ietf-alto-cdni-request-routing-alto], and [I-D.ietf-alto-performance-metrics]).

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. When the words appear in lower case, they are to be interpreted with their natural language meanings.

3. Terminology

This document uses the following acronyms:

3.1. Tree Diagrams

A simplified graphical representation of the data model is used in this document. The meaning of the symbols in these diagrams is defined in [RFC8340].

3.2. Prefixes in Data Node Names

In this document, names of data nodes and other data model objects are often used without a prefix, as long as it is clear from the context in which YANG module each name is defined. Otherwise, names are prefixed using the standard prefix associated with the corresponding YANG module, as shown in Table 1.

Table 1: Prefixes and corresponding YANG modules
Prefix YANG module Reference
yang ietf-yang-types [RFC6991]
inet ietf-inet-types [RFC6991]
key-chain ietf-key-chain [RFC8177]

4. Design Scope and Requirements

4.1. Scope of Data Model for ALTO O&M

What is in the scope of this document?

  • Data model for deploy an ALTO server/client.
  • Data model for operate and manage a running ALTO server/client.
  • Data model for functionality/capability configuration for ALTO services.
  • Data model for monitoring ALTO-related performance metrics.

What is not in the scope of this document?

This document does not define any data model related to specific implementation, including:

  • Data structures for how to store/deliver ALTO information resources (e.g., database schema to store a network map).
  • Data structures for how to store information collected from data sources. (e.g., database schema to store topology collected from an Interface to the Routing System (I2RS) client [RFC7921])

4.2. Basic Requirements

Based on discussions and recommendations in [RFC7285] and [RFC7971], the data model provided by this document satisfies basic requirements listed in Table 2.

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 provide metrics for server failures. Section 16.2.3 of [RFC7285], Section 3.3 of [RFC7971]
R5-1: The data model should support configuration for different data sources. Section 16.2.4 of [RFC7285], Section 3.2 of [RFC7971]
R5-2: The data model should support configuration for information resource generation algorithms. Section 16.2.4 of [RFC7285]
R5-3: The data model should support configuration for access control at information resource level. Section 16.2.4 of [RFC7285]
R6: The data model should provide performance monitoring for ALTO-specific metrics. Section 16.2.5 of [RFC7285], Section 3.4 of [RFC7971]
R7: The data model should support configuration for security policy management. Section 16.2.6 of [RFC7285]

4.3. Additional Requirements for Extensibility

R8: As the ALTO protocol is extensible, the data model for ALTO O&M should allow for augmentation to support potential future extensions.

4.4. Overview of ALTO O&M Data Model for Reference ALTO Architecture

Figure 1 shows a reference architecture for ALTO server implementation and YANG modules that server components implement. The server manager, information resource manager and data source listeners need to implement ietf-alto.yang (see Section 5). The performance monitor and logging and fault manager need to implement ietf-alto-stats.yang (see Section 6).

The data broker and algorithm plugins are not in the scope of the data model defined in this document. But user specified YANG modules can be applied to different algorithm plugins by augmenting the data model defined in this document (see Section 7).

  +----------------------+      +-----------------+
  | Performance Monitor: |<-----| Server Manager: |
  | ietf-alto-stats.yang |<-+ +-| ietf-alto.yang  |
  +----------------------+  | | +-----------------+
                          report
  +----------------------+  | | +-------------------+
  | Logging and Fault    |  +---| Information       |
  | Manager:             |<---+ | Resource Manager: |
  | ietf-alto-stats.yang |<-----| ietf-alto.yang    |
  +----------------------+      +-------------------+
                                         ^|
                                         || callback
                                         |v
     .............          ..............................
    /             \ ------> . Algorithm Plugin:          .
    . Data Broker .  read   . example-ietf-alto-alg.yang .
    ...............         ..............................
           ^
           | write
  +----------------+  Southbound  ++=============++
  | Data Source    |     API      ||             ||
  | Listener:      | <==========> || Data Source ||
  | ietf-alto.yang |              ||             ||
  +----------------+              ++=============++
Figure 1: A Reference ALTO Server Architecture and YANG Modules

5. Design of ALTO O&M Data Model

5.1. Overview of ALTO O&M Data Model

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

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

NOTE: So far, the ALTO YANG module only focuses on the ALTO server related configuration. The ALTO client related configuration will be added in a future version of the document.

module: ietf-alto
  +--rw alto-server
     +--rw listen
     |  +---u alto-server-listen-stack-grouping
     +--rw cost-type* [cost-type-name]
     |  +--rw cost-type-name    string
     |  +--rw cost-mode         identityref
     |  +--rw cost-metric       identityref
     +--rw meta* [meta-key]
     |  +--rw meta-key      string
     |  +--rw meta-value    string
     +--rw resource* [resource-id]
     |  +--rw resource-id                       resource-id
     |  +--rw resource-type                     identityref
     |  +--rw description?                      string
     |  +--rw accepted-group*                   string
     |  +--rw dependency*                       resource-id
     |  +--rw auth
     |  |  +--rw (auth-type-selection)?
     |  |     +--:(auth-key-chain)
     |  |     |  +--rw key-chain?   key-chain:key-chain-ref
     |  |     +--:(auth-key)
     |  |     +--:(auth-tls)
     |  +--rw (resource-params)?
     |     +--:(ird)
     |     |  +--rw alto-ird-params
     |     |     +--rw delegation    inet:uri
     |     +--:(networkmap)
     |     |  +--rw alto-networkmap-params
     |     |     +--rw is-default?   boolean
     |     |     +--rw filtered?     boolean
     |     |     +---u algorithm
     |     +--:(costmap)
     |     |  +--rw alto-costmap-params
     |     |     +--rw filtered?           boolean
     |     |     +---u filt-costmap-cap
     |     |     +---u algorithm
     |     +--:(endpointcost)
     |     |  +--rw alto-endpointcost-params
     |     |     +---u filt-costmap-cap
     |     |     +---u algorithm
     |     +--:(endpointprop)
     |     |  +--rw alto-endpointprop-params
     |     |     +--rw prop-types*   string
     |     |     +---u algorithm
     |     +--:(propmap) {propmap}?
     |     |  +--rw alto-propmap-params
     |     |     +---u algorithm
     |     +--:(cdni) {cdni}?
     |     |  +--rw alto-cdni-params
     |     |     +---u algorithm
     |     +--:(update) {incr-update}?
     |        +--rw alto-update-params
     |           +---u algorithm
     +--rw data-source* [source-id]
        +--rw source-id                             string
        +--rw source-type                           identityref
        +--rw (update-policy)
        |  +--:(reactive)
        |  |  +--rw reactive                        boolean
        |  +--:(proactive)
        |     +--rw poll-interval                   uint32
        +--rw (source-params)?
           +--:(yang-datastore)
           |  +--rw yang-datastore-source-params
           |     +--rw source-path
           |     |       yang:xpath1.0
           |     +--rw (restconf-endpoint)?
           |        +--:(local)
           |        +--:(remote)
           |           +--rw restconf-endpoint-params
           |              +---u rcc:restconf-client-listen-stack-grouping
           +--:(prometheus)
              +--rw prometheus-source-params
                 +--rw source-uri    inet:uri
                 +--rw query-data?   string

5.2. Meta Information of ALTO Server

The ALTO server instance contains the following basic configurations for the server setup.

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

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

TODO: A "base-uri" for ALTO clients to access may still be needed.

The "cost-type" list is the registry for the cost types that can be used in the ALTO server.

The "meta" list contains the customized meta data of the ALTO server. It will be populated into the meta field of the default Information Resource Directory (IRD).

TODO: As suggested by [RFC7286] and [RFC8686], the configuration related to ALTO server discovery should also be included here.

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

5.3. ALTO Information Resources Configuration Management

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

Each resoruce entry provide configuration defining how to create or update an ALTO information resource. Adding a new resource entry will submit an ALTO information resource creation intent to the intent system to create a new ALTO information resource. Updating an existing resource entry will update the corresponding ALTO information resource creation intent. Removing an existing resource entry will remove the corresponding ALTO information resource creation intent and also the created ALTO information resource.

The parameter of the intent interface defined by a resource entry MUST include a unique resource-id and a resource-type.

It can also include an accepted-group node containing a list of user-groups that can access this ALTO information resource.

As section 15.5.2 of [RFC7285] suggests, the module also defines authentication related configuration to employ access control at information resource level. The ALTO server returns the IRD to the ALTO client based on its authentication information.

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

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

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

Except for the ird resource, all the other types of resource entries have augmented algorithm node. The augmented algorithm node can reference data sources subscribed by the data-source entries (See Section 5.4).

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

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

  grouping filt-costmap-cap
    +-- cost-type-names*            string
    +-- cost-constraints?           boolean
    +-- max-cost-types?             uint32 {multi-cost}?
    +-- testable-cost-type-names*   string {multi-cost}?
    +-- calendar-attributes {cost-calendar}?
       +-- cost-type-names*       string
       +-- time-interval-size     decimal64
       +-- number-of-intervals    uint32

5.4. Data Sources

The ALTO server instance contains a list of data-source entries to subscribe the data sources from which ALTO information resources are derived (See Section 16.2.4 of [RFC7285]).

A data-source entry MUST include:

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

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

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

The data-source/source-params node can be augmented for different types of data sources. This data model only includes import interfaces for a list of predefined data sources. More data sources can be supported by future documents and other third-party providers.

module: ietf-alto
  +--rw alto-server
     ...
     +--rw data-source* [source-id]
        +--rw source-id                             string
        +--rw source-type                           identityref
        +--rw (update-policy)
        |  +--:(reactive)
        |  |  +--rw reactive                        boolean
        |  +--:(proactive)
        |     +--rw poll-interval                   uint32
        +--rw (source-params)?
           +--:(yang-datastore)
           |  +--rw yang-datastore-source-params
           |     +--rw source-path
           |     |       yang:xpath1.0
           |     +--rw (restconf-endpoint)?
           |        +--:(local)
           |        +--:(remote)
           |           +--rw restconf-endpoint-params
           |              +---u rcc:restconf-client-listen-stack-grouping
           +--:(prometheus)
              +--rw prometheus-source-params
                 +--rw source-uri    inet:uri
                 +--rw query-data?   string

Note: Current source configuration still has limitations. It should be revised to support more general southbound and data retrieval mechanisms.

5.4.1. Yang DataStore Data Source

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

It supports two types of endpoints: local and remote.

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

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

5.4.2. Prometheus Data Source

The prometheus-source-params is used to import common performance metrics data which is provided by a Prometheus server. The source-uir is used to establish the connection with the Prometheus server. The query-data is used to speficify the potential query expression in PromQL.

5.5. Model for ALTO Server-to-server Communication

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

The YANG module defined in this document contains the configuration for the communication between two ALTO servers.

TODO: this is still under the open discussion status.

6. Design of ALTO O&M Statistics Data Model

6.1. Model for ALTO Logging and Fault Management

As section 16.2.1 and section 16.2.3 of [RFC7285] suggest, the YANG data module defined in this document contains statistics for logging and failure detection.

NOTE: The detailed YANG module will appear in the future version.

6.2. Model for ALTO-specific Performance Monitoring

As section 16.2.5 of [RFC7285] suggests, the YANG data module defined in this document also contains statistics for ALTO-specific performance metrics.

More specifically, this data model contains the following measurement information suggested by [RFC7971]:

  • Measurement of impact

    • Total amount and distribution of traffic
    • Application performance

  • System and service performance

    • Requests and responses for each information resource
    • CPU and memory utilization
    • ALTO map updates
    • Number of PIDs
    • ALTO map sizes

Besides the measurement information suggested by [RFC7971], this data model also contains useful measurement information for other ALTO extensions:

The module, "ietf-alto-stats", augments the ietf-alto module to include statistics at the ALTO server and information resource level.

module: ietf-alto-stats

  augment /alto:alto-server:
    +--ro num-total-req?         yang:counter32
    +--ro num-total-succ?        yang:counter32
    +--ro num-total-fail?        yang:counter32
    +--ro num-total-last-req?    yang:counter32
    +--ro num-total-last-succ?   yang:counter32
    +--ro num-total-last-fail?   yang:counter32
  augment /alto:alto-server/alto:resource:
    +--ro num-res-upd?    yang:counter32
    +--ro res-mem-size?   yang:counter32
    +--ro res-enc-size?   yang:counter32
    +--ro num-res-req?    yang:counter32
    +--ro num-res-succ?   yang:counter32
    +--ro num-res-fail?   yang:counter32
  augment /alto:alto-server/alto:resource/alto:resource-params
            /alto:networkmap/alto:alto-networkmap-params:
    +--ro num-map-pid?   yang:counter32
  augment /alto:alto-server/alto:resource/alto:resource-params
            /alto:propmap/alto:alto-propmap-params:
    +--ro num-map-entry?   yang:counter32
  augment /alto:alto-server/alto:resource/alto:resource-params
            /alto:cdni/alto:alto-cdni-params:
    +--ro num-base-obj?   yang:counter32
  augment /alto:alto-server/alto:resource/alto:resource-params
            /alto:update/alto:alto-update-params:
    +--ro num-upd-sess?      yang:counter32
    +--ro num-event-total?   yang:counter32
    +--ro num-event-max?     yang:counter32
    +--ro num-event-min?     yang:counter32
    +--ro num-event-avg?     yang:counter32

7. Extension of ALTO O&M Data Model

As ALTO protocol is extensible, new protocol extensions can be developed after this data model is published. To support future ALTO protocol extensions, the extension documents can augment the existing cases of the resource-params choice with new configuration parameters for existing ALTO information resource extensions, or augment the resource-params with new cases for new ALTO information resources.

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

The following example shows how the developer augments the algorithm choice of alto-networkmap-params with a creation algorithm for the network map resource.

module: example-ietf-alto-alg

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

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

l3-unicast-topo

This parameter refers to the source id of a data source node subscribed in the data-source list (See Section 5.4). The corresponding data source is assumed to be an internel data source (See Section 5.4.1) for an IETF layer 3 unicast topology defined in [RFC8346]. The algorithm uses the topology data from this data source to compute the ALTO network map resource.

depth

This optional parameter sets the depth of the clustering algorithm. For example, if the depth sets to 1, the algorithm will generate PID for every l3-node in the topology.

The creation algorithm can be reactively called once the referenced data source updates. Therefore, the ALTO network map resource can be updated dynamically. The update of the reference data source depends on the used update-policy (See Section 5.4).

8. ALTO OAM YANG Module

8.1. The ietf-alto Module 

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

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

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

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

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

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

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

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

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

  organization
    "IETF ALTO Working Group";

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

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

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

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Revised BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX
     (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
     for full legal notices.

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
     'MAY', and 'OPTIONAL' in this document are to be interpreted as
     described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
     they appear in all capitals, as shown here.";

  revision "2022-07-11" {
    description
      "Initial Version.";
    reference
      "RFC XXXX: A YANG Data Model for OAM and Management of ALTO
       Protocol.";
  }

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

  // Base identities

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

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

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

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

  // Identities for ALTO information resources

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

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

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

  // Identities for predefined data sources

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

  identity prometheus {
    base source-type;
    description
      "Identity for data source of prometheus system.";
  }

  // Identities for cost mode

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

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

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

  // Identities for cost metrics

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

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

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

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

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

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

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

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

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

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

  // Features

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

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

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

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

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

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

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

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

  // Groupings

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

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

  grouping alto-server-grouping {
    description
      "A reuseable grouping for configuring an ALTO server without
       any consideration for how underlying transport sessions are
       established.";
    // TODO: ALTO specific server-level configuration
  }

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

  // Top-level container

  container alto-server {
    description
      "The ALTO server instance.";
    container listen {
      description
        "Configure the ALTO server to listen for ALTO clients.";
      uses alto-server-listen-stack-grouping;
    }
    list cost-type {
      key "cost-type-name";
      leaf cost-type-name {
        type string;
        description
          "The name to reference cost type";
      }
      leaf cost-mode {
        type identityref {
          base cost-mode;
        }
        mandatory true;
        description
          "The referenced cost mode";
      }
      leaf cost-metric {
        type identityref {
          base cost-metric;
        }
        mandatory true;
        description
          "The referenced cost metric";
      }
      description
        "Mapping between name and referenced cost type";
    }
    list meta {
      key "meta-key";
      leaf meta-key {
        type string;
        description
          "Custom meta key";
      }
      leaf meta-value {
        type string;
        mandatory true;
        description
          "Custom meta value";
      }
      description
        "Mapping of custom meta information";
      reference
        "Section 8.4.1 of RFC 7285.";
    }
    list resource {
      key "resource-id";
      leaf resource-id {
        type resource-id;
        description
          "resource-id to be defined.";
      }
      leaf resource-type {
        type identityref {
          base resource-type;
        }
        mandatory true;
        description
          "identityref to be defined.";
      }
      leaf description {
        type string;
        description
          "The optional description for this information resource.";
      }
      leaf-list accepted-group {
        type string;
        description
          "Access list for authenticated clients.";
      }
      leaf-list dependency {
        type resource-id;
        description
          "A list of dependent information resources.";
      }
      container auth {
        description
          "The authentication options";
        choice auth-type-selection {
          description
            "Options for expressing authentication
             setting.";
          case auth-key-chain {
            leaf key-chain {
              type key-chain:key-chain-ref;
              description
                "key-chain name.";
            }
          }
          case auth-key {
          }
          case auth-tls {
          }
        }
      }
      choice resource-params {
        description
          "Resource-specific configuration.";
        case ird {
          container alto-ird-params {
            leaf delegation {
              type inet:uri;
              mandatory true;
              description
                "Upstream IRD to be delegated";
            }
            description
              "IRD-specific configuration";
          }
        }
        case networkmap {
          container alto-networkmap-params {
            description
              "(Filtered) Network Map specific configuration";
            reference
              "Section 11.2.1 and Section 11.3.1 of RFC 7285.";
            leaf is-default {
              type boolean;
              description
                "Set whether this is the default network map";
            }
            leaf filtered {
              type boolean;
              default false;
              description
                "Configure whether filtered network map is
                 supported.";
            }
            uses algorithm;
          }
        }
        case costmap {
          container alto-costmap-params {
            description
              "(Filtered) Cost Map specific configuration";
            reference
              "Section 11.2.2 and Section 11.3.2 of RFC 7285.";
            leaf filtered {
              type boolean;
              description
                "Configure whether filtered cost map is supported.";
            }
            uses filt-costmap-cap;
            uses algorithm;
          }
        }
        case endpointcost {
          container alto-endpointcost-params {
            description
              "Endpoint Cost Service specific configuration";
            reference
              "Section 11.5 of RFC 7285";
            uses filt-costmap-cap;
            uses algorithm;
          }
        }
        case endpointprop {
          container alto-endpointprop-params {
            description
              "Endpoint Cost Service specific configuration";
            reference
              "Section 11.5 of RFC 7285";
            leaf-list prop-types {
              type string;
              min-elements 1;
              description
                "Supported endpoint properties.";
            }
            uses algorithm;
          }
        }
        case propmap {
          if-feature "propmap";
          container alto-propmap-params {
            uses algorithm;
            description
              "(Filtered) Entity Property Map specific
               configuration";
          }
        }
        case cdni {
          if-feature "cdni";
          container alto-cdni-params {
            uses algorithm;
            description
              "CDNi specific configuration";
          }
        }
        case update {
          if-feature "incr-update";
          container alto-update-params {
            uses algorithm;
            description
              "Incremental Updates specific configuration";
          }
        }
      }
      description
        "ALTO information resources to be defined";
    }
    list data-source {
      key "source-id";
      leaf source-id {
        type string;
        description
          "Data source id that can be referenced by information
           resource creation algorithms.";
      }
      leaf source-type {
        type identityref {
          base source-type;
        }
        mandatory true;
        description
          "Source-type to be defined";
      }
      choice update-policy {
        mandatory true;
        case reactive {
          leaf reactive {
            type boolean;
            mandatory true;
            description
              "Reactive mode";
          }
        }
        case proactive {
          leaf poll-interval {
            type uint32;
            mandatory true;
            description
              "Polling interval in seconds for proactive mode";
          }
        }
        description
          "Policy to get updates from data sources";
      }
      choice source-params {
        case yang-datastore {
          container yang-datastore-source-params {
            leaf source-path {
              type yang:xpath1.0;
              mandatory true;
              description
                "XPath to subscribed YANG datastore node";
            }
            description
              "YANG datastore specific configuration";
            choice restconf-endpoint {
              case local {
                // Use local API to access YANG datastore
              }
              case remote {
                container restconf-endpoint-params {
                  uses rcc:restconf-client-listen-stack-grouping;
                }
              }
            }
          }
        }
        case prometheus {
          container prometheus-source-params {
            leaf source-uri {
              type inet:uri;
              mandatory true;
              description
                "URI to prometheus agent";
            }
            leaf query-data {
              type string;
              description
                "Query expression";
            }
            description
              "Prometheus specific configuration";
          }
        }
        description
          "Data source specific configuration";
      }
      description
        "List of subscribed data sources.";
    }
  }
}

<CODE ENDS>

8.2. The ietf-alto-stats Module 

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

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

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

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

  organization
    "IETF ALTO Working Group";

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

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

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

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Revised BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX
     (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
     for full legal notices.";

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

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

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

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

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

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

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

<CODE ENDS>

9. Security Considerations

TBD.

10. IANA Considerations

This document registers two URIs in the "IETF XML Registry" [RFC3688]. Following the format in RFC 3688, the following registrations are requested.

  URI: urn:ietf:params:xml:ns:yang:ietf-alto
  Registrant Contact: The IESG.
  XML: N/A; the requested URI is an XML namespace.

  URI: urn:ietf:params:xml:ns:yang:ietf-alto-stats
  Registrant Contact: The IESG.
  XML: N/A; the requested URI is an XML namespace.

This document registers two YANG modules in the "YANG Module Names" registry [RFC6020].

  Name: ietf-alto
  Namespace: urn:ietf:params:xml:ns:yang:ietf-alto
  Prefix: alto
  Reference: [RFCthis]

  Name: ietf-alto-stats
  Namespace: urn:ietf:params:xml:ns:yang:ietf-alto-stats
  Prefix: alto
  Reference: [RFCthis]

[RFC Editor: Please replace RFCthis with the published RFC number for this document.]

11. References

11.1. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3688]
Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, , <https://www.rfc-editor.org/rfc/rfc3688>.
[RFC6020]
Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, , <https://www.rfc-editor.org/rfc/rfc6020>.
[RFC6991]
Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, , <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, , <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, , <https://www.rfc-editor.org/rfc/rfc7286>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8177]
Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J. Zhang, "YANG Data Model for Key Chains", RFC 8177, DOI 10.17487/RFC8177, , <https://www.rfc-editor.org/rfc/rfc8177>.
[RFC8189]
Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost Application-Layer Traffic Optimization (ALTO)", RFC 8189, DOI 10.17487/RFC8189, , <https://www.rfc-editor.org/rfc/rfc8189>.
[RFC8340]
Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, , <https://www.rfc-editor.org/rfc/rfc8340>.
[RFC8686]
Kiesel, S. and M. Stiemerling, "Application-Layer Traffic Optimization (ALTO) Cross-Domain Server Discovery", RFC 8686, DOI 10.17487/RFC8686, , <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, , <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, , <https://www.rfc-editor.org/rfc/rfc8896>.

11.2. Informative References

[I-D.ietf-alto-cdni-request-routing-alto]
Seedorf, J., Yang, Y. R., Ma, K. J., Peterson, J., and J. J. Zhang, "Content Delivery Network Interconnection (CDNI) Request Routing: CDNI Footprint and Capabilities Advertisement using ALTO", Work in Progress, Internet-Draft, draft-ietf-alto-cdni-request-routing-alto-22, , <https://datatracker.ietf.org/doc/html/draft-ietf-alto-cdni-request-routing-alto-22>.
[I-D.ietf-alto-path-vector]
Gao, K., Lee, Y., Randriamasy, S., Yang, Y. R., and J. J. Zhang, "An ALTO Extension: Path Vector", Work in Progress, Internet-Draft, draft-ietf-alto-path-vector-25, , <https://datatracker.ietf.org/doc/html/draft-ietf-alto-path-vector-25>.
[I-D.ietf-alto-performance-metrics]
Wu, Q., Yang, Y. R., Lee, Y., Dhody, D., Randriamasy, S., and L. M. C. Murillo, "ALTO Performance Cost Metrics", Work in Progress, Internet-Draft, draft-ietf-alto-performance-metrics-28, , <https://datatracker.ietf.org/doc/html/draft-ietf-alto-performance-metrics-28>.
[I-D.ietf-alto-unified-props-new]
Roome, W., Randriamasy, S., Yang, Y. R., Zhang, J. J., and K. Gao, "An ALTO Extension: Entity Property Maps", Work in Progress, Internet-Draft, draft-ietf-alto-unified-props-new-24, , <https://datatracker.ietf.org/doc/html/draft-ietf-alto-unified-props-new-24>.
[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, , <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, , <https://www.rfc-editor.org/rfc/rfc7971>.
[RFC8346]
Clemm, A., Medved, J., Varga, R., Liu, X., Ananthakrishnan, H., and N. Bahadur, "A YANG Data Model for Layer 3 Topologies", RFC 8346, DOI 10.17487/RFC8346, , <https://www.rfc-editor.org/rfc/rfc8346>.

Appendix A. Example Module for Information Resource Creation Algorithm

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

module example-ietf-alto-alg {

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

  import ietf-alto {
    prefix "alto";
  }

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

Acknowledgements

The authors thank Qiufang Ma and Qin Wu for their help with drafting the initial version of the YANG modules. Thanks also to Adrian Farrel, Qiao Xiang, Qin Wu, and Qiufang Ma for their reviews and valuable feedback.

Authors' Addresses

Jingxuan Jensen Zhang
Tongji University
4800 Cao'An Hwy
Shanghai
201804
China
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore 560066
Karnataka
India
Kai Gao
Sichuan University
No.24 South Section 1, Yihuan Road
Chengdu
610000
China
Roland Schott
Deutsche Telekom
Heinrich-Hertz-Strasse 3-7
64295 Darmstadt
Germany