OPSAWG B. Claise Internet-Draft J. Quilbeuf Intended status: Standards Track Huawei Expires: 11 February 2023 P. Lucente NTT P. Fasano TIM S.p.A T. Arumugam Cisco Systems, Inc. 10 August 2022 YANG Modules for Service Assurance draft-ietf-opsawg-service-assurance-yang-07 Abstract This document specifies YANG modules for representing assurance graphs. These graphs represent the assurance of a given service by decomposing it into atomic assurance elements called subservices. A companion document, Service Assurance for Intent-based Networking Architecture, presents an architecture for implementing the assurance of such services. The YANG data models in this document conforms to the Network Management Datastore Architecture (NMDA) defined in RFC 8342. 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 11 February 2023. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. Claise, et al. Expires 11 February 2023 [Page 1] Internet-Draft YANG Modules for Service Assurance August 2022 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. YANG Modules Overview . . . . . . . . . . . . . . . . . . . . 3 3. Base IETF Service Assurance YANG Module . . . . . . . . . . . 4 3.1. Concepts . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. Tree View . . . . . . . . . . . . . . . . . . . . . . . . 6 3.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 10 3.4. Rejecting Circular Dependencies . . . . . . . . . . . . . 18 4. Subservice Augmentation: ietf-service-assurance-device YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.1. Tree View . . . . . . . . . . . . . . . . . . . . . . . . 19 4.2. Concepts . . . . . . . . . . . . . . . . . . . . . . . . 19 4.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 19 5. Subservice Augmentation: ietf-service-assurance-interface YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.1. Tree View . . . . . . . . . . . . . . . . . . . . . . . . 21 5.2. Concepts . . . . . . . . . . . . . . . . . . . . . . . . 21 5.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 22 6. Security Considerations . . . . . . . . . . . . . . . . . . . 23 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 7.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 24 7.2. The YANG Module Names Registry . . . . . . . . . . . . . 25 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 8.1. Normative References . . . . . . . . . . . . . . . . . . 25 8.2. Informative References . . . . . . . . . . . . . . . . . 26 Appendix A. Vendor-specific Subservice Augmentation: example-service-assurance-device-acme YANG module . . . . 27 A.1. Tree View . . . . . . . . . . . . . . . . . . . . . . . . 27 A.2. Concepts . . . . . . . . . . . . . . . . . . . . . . . . 27 A.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 27 Appendix B. Further Augmentations: IP Connectivity and IS-IS subservices . . . . . . . . . . . . . . . . . . . . . . . 29 B.1. IP Connectivity Tree View . . . . . . . . . . . . . . . . 29 B.2. IS-IS Tree View . . . . . . . . . . . . . . . . . . . . . 29 B.3. Global Tree View . . . . . . . . . . . . . . . . . . . . 30 B.4. IP Connectivity YANG Module . . . . . . . . . . . . . . . 31 B.5. IS-IS YANG Module . . . . . . . . . . . . . . . . . . . . 33 Claise, et al. Expires 11 February 2023 [Page 2] Internet-Draft YANG Modules for Service Assurance August 2022 Appendix C. Example of YANG instances . . . . . . . . . . . . . 34 Appendix D. YANG Library for Service Assurance . . . . . . . . . 38 Appendix E. Changes between revisions . . . . . . . . . . . . . 39 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 41 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 1. Introduction [I-D.ietf-opsawg-service-assurance-architecture] specifies an architecture and a set of involved components for service assurance. This document complements the architecture by specifying a data model for the interfaces between components. More specifically, the document provides YANG modules for the purpose of service assurance in a format that is: * machine readable * vendor independent * augmentable 1.1. Terminology 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 13 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. The terms used in this document are defined in [I-D.ietf-opsawg-service-assurance-architecture]. The meanings of the symbols in the tree diagrams are defined in [RFC8340]. 2. YANG Modules Overview The main YANG module, "ietf-service-assurance" (Section 3), defines objects for assuring network services based on their decomposition into so-called subservices. The subservices are hierarchically organised by dependencies. The subservices, along with the dependencies, constitute an assurance graph. This module should be supported by an agent, able to interact with the devices in order to produce a health status and symptoms for each subservice in an assurance graph. This module is intended for the following use cases: * Assurance graph configuration: Claise, et al. Expires 11 February 2023 [Page 3] Internet-Draft YANG Modules for Service Assurance August 2022 - Subservices: configure a set of subservices to assure, by specifying their types and parameters. - Dependencies: configure the dependencies between the subservices, along with their type. * Assurance telemetry: export the assurance graph with health status and symptoms for each node. The modules presented in this document conform to the Network Management Datastore Architecture defined in [RFC8342]. The second YANG module, "ietf-service-assurance-device" (Section 4), augments the "ietf-service-assurance" module by adding support for the device subservice. Additional subservice types might be added following a similar approach. The third YANG module, "ietf-service-assurance-interface" (Section 5), is another example that augments the "ietf-service- assurance" module, by adding support for the interface subservice. We provide additional examples in the appendix. The module "example- service-assurance-device-acme" (Appendix A) augments the "ietf- service-assurance-device" module to customize it for devices of the fictional ACME Corporation. Additional vendor-specific parameters might be added following a similar approach. We also provide the modules "example-service-assurance-ip-connectivity" and "example- service-assurance-is-is" (Appendix B) to model the example in Figure 2 from Section 3.1 of [I-D.ietf-opsawg-service-assurance-architecture]. 3. Base IETF Service Assurance YANG Module 3.1. Concepts The "ietf-service-assurance" YANG module assumes a set of subservices, to be assured independently. A subservice is a feature or a subpart of the network system that a given service instance depends on. Examples of subservices include: * device: whether a device is healthy, and if not, what are the symptoms. Potential symptoms are "CPU overloaded", "Out of RAM", or "Out of TCAM". * ip-connectivity: given two IP addresses bound to two devices, what is the quality of the IP connectivity between them. Potential symptoms are "No route available" or "ECMP Imbalance". Claise, et al. Expires 11 February 2023 [Page 4] Internet-Draft YANG Modules for Service Assurance August 2022 The first example is a subservice representing a subpart of the network system, while the second is a subservice representing a feature of the network. In both cases, these subservices might depend on other subservices, for instance, the connectivity might depend on a subservice representing the routing system and on a subservice representing ECMP. The two subservices presented above need different sets of parameters to fully characterize one of their instance. An instance of the device subservice is fully characterized by a single parameter allowing to identify the device to monitor. For ip-connectivity subservice, at least the device and IP address for both ends of the link are needed to fully characterize an instance. Therefore, the "ietf-service-assurance" module is intended to be augmented for each type of subservice, so that the needed parameters are modelled in the augmenting module. The only "built-in" type available represents service instances. A service instance is represented as a subservice instance of type "service". The parameters required to fully identify a service instance are the type of the service and the name of the service instance. The dependencies are modelled as an adjacency list, in the sense that each subservice contains a list of pointers to its dependencies. That list can be empty if the subservice instance does not have any dependencies. By specifying service instances and their dependencies in terms of subservices, one defines a global assurance graph. That assurance graph is the result of merging all the individual assurance graphs for the assured service instances. Each subservice instance is expected to appear only one in the global assurance graph even if several service instances depend on it. For example, an instance of the device subservice is a dependency of every service instance that rely on the corresponding device. The assurance graph of a specific service instance is the subgraph obtained by traversing the global assurance graph through the dependencies starting from the specific service instance. An assurance agent configured with such a graph is expected to produce, for each configured subservice: a health-status indicating how healthy the subservice is and when the subservice is not healthy, a list of symptoms explaining why the subservice is not healthy. Claise, et al. Expires 11 February 2023 [Page 5] Internet-Draft YANG Modules for Service Assurance August 2022 3.2. Tree View The following tree diagram [RFC8340] provides an overview of the "ietf-service-assurance" module. module: ietf-service-assurance +--ro assurance-graph-last-change yang:date-and-time +--rw subservices | +--rw subservice* [type id] | +--rw type identityref | +--rw id string | +--ro last-change? yang:date-and-time | +--ro label? string | +--rw maintenance-contact? string | +--rw (parameter) | | +--:(service-instance-parameter) | | +--rw service-instance-parameter | | +--rw service string | | +--rw instance-name string | +--ro health-score? union | +--ro symptoms-history-start? yang:date-and-time | +--ro symptoms | | +--ro symptom* [start-date-time agent-id symptom-id] | | +--ro symptom-id | | | -> /agents/symptoms-description/symptom-id | | +--ro agent-id -> /agents/agent-id | | +--ro health-score-weight? uint8 | | +--ro start-date-time yang:date-and-time | | +--ro stop-date-time? yang:date-and-time | +--rw dependencies | +--rw dependency* [type id] | +--rw type | | -> /subservices/subservice/type | +--rw id leafref | +--rw dependency-type? identityref +--ro agents* [agent-id] | +--ro agent-id string | +--ro symptoms-description* [symptom-id] | +--ro symptom-id string | +--ro description string +--ro assured-services* [service] +--ro service leafref +--ro instances* [instance-name] +--ro instance-name leafref +--ro subservices* [type id] +--ro type -> /subservices/subservice/type +--ro id leafref Claise, et al. Expires 11 February 2023 [Page 6] Internet-Draft YANG Modules for Service Assurance August 2022 The date of last change "assurance-graph-last-change" is read only. It must be updated each time the graph structure is changed by addition or deletion of subservices, dependencies or modification of their configurable attributes. Such modifications correspond to a structural change in the graph. The date of last change is useful for a client to quickly check if there is a need to update the graph structure. A change in the health-score or symptoms associated to a service or subservice does not change the structure of the graph and thus has no effect on the date of last change. The "subservice" list contains all the subservice instances currently configured on the server. A subservice declaration MUST provide: * A subservice type ("type"): reference to an identity that inherits from "subservice-base", which is the base identity for any subservice type. * An id ("id"): string uniquely identifying the subservice among those with the same type, The type and id uniquely identify a given subservice. The "last-change" indicates when this particular subservice was modified for the last time. The "label" is a human-readable description of the subservice. The presence of "maintenance-contact" field inhibits the emission of symptoms for that subservice and subservices that depend on them. See Section 3.6 of [I-D.ietf-opsawg-service-assurance-architecture] for a more detailed discussion. The "parameter" choice is intended to be augmented in order to describe parameters that are specific to the current subservice type. This base module defines only the subservice type representing service instances. Service instances MUST be modeled as a particular type of subservice with two parameters, "service" and "instance- name". The "service" parameter is the name of the service defined in the network orchestrator, for instance "point-to-point-l2vpn". The "instance-name" parameter is the name assigned to the particular instance to be assured, for instance the name of the customer using that instance. The "health-score" contains a value normally between 0 and 100 indicating how healthy the subservice is. The special value -1 can be used to specify that no value could be computed for that health- score, for instance if some metric needed for that computation could not be collected. Claise, et al. Expires 11 February 2023 [Page 7] Internet-Draft YANG Modules for Service Assurance August 2022 The "symptoms-history-start" is the cutoff date for reporting symptoms. Symptoms that were terminated before that date are not reported anymore in the model. The status of each subservice contains a list of symptoms. Each symptom is specified by * an identifier "symptom-id" which identifies the symptom locally to an agent, * an agent identifier "agent-id" which identifies the agent raising the symptom, * a "health-score-weight" specifying the impact to the health score incurred by this symptom, * a "start-date-time" indicating when the symptom became active and * a "stop-date-time" indicating when the symptom stopped being active, that field is not present if the symptom is still active. In order for the pair "agent-id" and "symptom-id" to uniquely identify a symptom, the following is necessary: * The "agent-id" MUST be unique among all agents of the system * The "symptom-id" MUST be unique among all symptoms raised by the agent Note that "agent-id" and "symptom-id" are leafrefs pointing to the objects defined later in the document. While the combination of "symptom-id" and "agent-id" is sufficient as an unique key list, the "start-date-time" second key help sorting and retrieving relevant symptoms. The "dependency" list contains the dependencies for the current subservice. Each of them is specified by a leafref to both "type" and "id" of the target dependencies. A dependency has a type indicated in the "dependency-type" field. Two types are specified in the model: * Impacting: such a dependency indicates an impact on the health of the dependent, * Informational: such a dependency might explain why the dependent has issues but does not impact its health. Claise, et al. Expires 11 February 2023 [Page 8] Internet-Draft YANG Modules for Service Assurance August 2022 To illustrate the difference between "impacting" and "informational", consider the interface subservice, representing a network interface. If the device to which the network interface belongs goes down, the network interface will transition to a "down" state as well. Therefore, the dependency of the interface subservice towards the device subservice is "impacting". On the other hand, a dependency towards the ecmp-load subservice, which checks that the load between ECMP remains stable throughout time, is only "informational". Indeed, services might be perfectly healthy even if the load distribution between ECMP changed. However, such an instability might be a relevant symptom for diagnosing the root cause of a problem. The list "agents" at the top level contains the list of symptoms per agent. As stated above, the key of the list is the "agent-id", which MUST be unique among agents of a given assurance system. For each agent, the list "symptoms-description" maps a "symptom-id" to its "description". The "symptom-id" MUST be unique among the symptoms raised by the agent. The list "assured-services" presents the subservices indexed by assured service instances. For each service type, identified by the "service" leaf, all instances of that service are listed in the "instances" list. For each instance, identified by the "instance" leaf, the "subservices" list contains all subservices part of the assurance graph for that specific instance. These imbricated lists provide a query optimization to get the list of subservices in that assurance graph in a single query, instead of recursively querying the dependencies of each subservice, starting from the node representing the service instance. The relation between the health score ("health-score") and the health-score-weight of the currently active symptoms is not explicitly defined in this document. The only requirement is that a health score that strictly smaller than 100 (the maximal value) must be explained by at least one symptom. A way to enforce that requirement is to first detect symptoms and then compute the health score based on the health-score-weight of the detected symptoms. As an example, such a computation could be to sum the health-score- weight of the active symptoms, subtract that value from 100 and change the value to 0 if negative. The relation between health-score and health-score-weight is left to the implementor (of an agent [I-D.ietf-opsawg-service-assurance-architecture]). Keeping the history of the graph structure is out of scope for this YANG module. Only the current version of the assurance graph can be fetched. In order to keep the history of the graph structure, some time-series database (TSDB) or similar storage must be used. Claise, et al. Expires 11 February 2023 [Page 9] Internet-Draft YANG Modules for Service Assurance August 2022 3.3. YANG Module file "ietf-service-assurance@2022-04-07.yang" module ietf-service-assurance { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-service-assurance"; prefix sain; import ietf-yang-types { prefix yang; reference "RFC 6991: Common YANG Data Types"; } organization "IETF OPSAWG Working Group"; contact "WG Web: WG List: Author: Benoit Claise Author: Jean Quilbeuf "; description "This module defines objects for assuring services based on their decomposition into so-called subservices, according to the SAIN (Service Assurance for Intent-based Networking) architecture. The subservices hierarchically organised by dependencies constitute an assurance graph. This module should be supported by an assurance agent, able to interact with the devices in order to produce a health status and symptoms for each subservice in the assurance graph. This module is intended for the following use cases: * Assurance graph configuration: - subservices: configure a set of subservices to assure, by specifying their types and parameters. - dependencies: configure the dependencies between the subservices, along with their type. * Assurance telemetry: export the health status of the subservices, along with the observed symptoms. 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 Claise, et al. Expires 11 February 2023 [Page 10] Internet-Draft YANG Modules for Service Assurance August 2022 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; see the RFC itself for full legal notices. "; revision 2022-08-10 { description "Initial version."; reference "RFC xxxx: YANG Modules for Service Assurance"; } identity subservice-base { description "Base identity for subservice types."; } identity service-instance-type { base subservice-base; description "Identity representing a service instance."; } identity dependency-type { description "Base identity for representing dependency types."; } identity informational { base dependency-type; description "Indicates that symptoms of the dependency might be of interest for the dependent, but the status of the dependency should not have any impact on the dependent."; } identity impacting { base dependency-type; description "Indicates that the status of the dependency directly impacts the status of the dependent."; } grouping symptom { description "A grouping for the symptoms for a specific subservice."; leaf symptom-id { Claise, et al. Expires 11 February 2023 [Page 11] Internet-Draft YANG Modules for Service Assurance August 2022 type leafref { path "/agents/symptoms-description/symptom-id"; } description "Identifier of the symptom, to be interpreted according to the agent identified by the agent-id."; } leaf agent-id { type leafref { path "/agents/agent-id"; } description "Identifier of the agent raising the current symptom."; } leaf health-score-weight { type uint8 { range "0 .. 100"; } description "The weight to the health score incurred by this symptom. The higher the value, the more of an impact this symptom has. If a subservice health score is not 100, there must be at least one symptom with a health score weight larger than 0."; } leaf start-date-time { type yang:date-and-time; description "Date and time at which the symptom was detected."; } leaf stop-date-time { type yang:date-and-time; description "Date and time at which the symptom stopped being detected. must after the start-date-time."; } } grouping subservice-reference { description "Reference to a specific subservice, identified by its type and identifier"; leaf type { type leafref { path "/subservices/subservice/type"; } description "The type of the subservice to refer to (e.g., device)."; } Claise, et al. Expires 11 February 2023 [Page 12] Internet-Draft YANG Modules for Service Assurance August 2022 leaf id { type leafref { path "/subservices/subservice[type=current()/../type]/id"; } description "The identifier of the subservice to refer to."; } } grouping subservice-dependency { description "Represents a dependency to another subservice."; uses subservice-reference; leaf dependency-type { type identityref { base dependency-type; } description "Represents the type of dependency (e.g., informational, impacting)."; } } leaf assurance-graph-last-change { type yang:date-and-time; config false; mandatory true; description "Date and time at which the assurance graph last changed after the changes (dependencies and/or maintenance windows parameters) are applied to the subservice(s). These date and time must be more recent or equal compared to the more recent value of any changed subservices last-change"; } container subservices { description "Root container for the subservices."; list subservice { key "type id"; description "List of configured subservices."; leaf type { type identityref { base subservice-base; } description "Type of the subservice, for instance, device or interface."; } Claise, et al. Expires 11 February 2023 [Page 13] Internet-Draft YANG Modules for Service Assurance August 2022 leaf id { type string; description "Identifier of the subservice instance. Must be unique among subservices of the same type."; } leaf last-change { type yang:date-and-time; config false; description "Date and time at which the structure for this subservice instance last changed, i.e., dependencies and/or maintenance windows parameters."; } leaf label { type string; config false; description "Label of the subservice, i.e., text describing what the subservice is to be displayed on a human interface. It is not intended for random end users but for network/system/software engineers that are able to interpret it. Therefore, no mechanism for language tagging is needed."; } leaf maintenance-contact { type string; description "A string used to model an administratively assigned name of the resource that is performing maintenance. The presence of this field indicates that the current subservice is under maintenance. It is suggested that this name contain one or more of the following: IP address, management station name, network manager's name, location, or phone number. In some cases the agent itself will be the owner of an entry. In these cases, this string shall be set to a string starting with 'monitor'."; } choice parameter { mandatory true; description "Specify the required parameters per subservice type. Each module augmenting this module with a new subservice type, that is a new identity based on subservice-base should augment this choice as well, by adding a container Claise, et al. Expires 11 February 2023 [Page 14] Internet-Draft YANG Modules for Service Assurance August 2022 available only if the current subservice type is the newly added identity."; container service-instance-parameter { when "derived-from-or-self(../type, 'sain:service-instance-type')"; description "Specify the parameters of a service instance."; leaf service { type string; mandatory true; description "Name of the service."; } leaf instance-name { type string; mandatory true; description "Name of the instance for that service."; } } // Other modules can augment their own cases into here } leaf health-score { type union { type uint8 { range "0 .. 100"; } type enumeration { enum missing { value -1; description "Explictly represent the fact that the health score is missing. This could be used when metrics crucial to establish the health score are not collected anymore."; } } } config false; description "Score value of the subservice health. A value of 100 means that subservice is healthy. A value of 0 means that the subservice is broken. A value between 0 and 100 means that the subservice is degraded."; } leaf symptoms-history-start { type yang:date-and-time; config false; description Claise, et al. Expires 11 February 2023 [Page 15] Internet-Draft YANG Modules for Service Assurance August 2022 "Date and time at which the symptoms history starts for this subservice instance, either because the subservice instance started at that date and time or because the symptoms before that were removed due to a garbage collection process."; } container symptoms { config false; description "Symptoms for the subservice."; list symptom { key "start-date-time agent-id symptom-id"; description "List of symptoms the subservice. While the start-date-time key is not necessary per se, this would get the entries sorted by start-date-time for easy consumption."; uses symptom; } } container dependencies { description "Indicates the set of dependencies of the current subservice, along with their types."; list dependency { key "type id"; description "List of dependencies of the subservice."; uses subservice-dependency; } } } } list agents { key "agent-id"; config false; description "Contains symptoms of each agent involved in computing the health status of the current graph. This list act as a glossary for understanding the symptom ids returned by each agent."; leaf agent-id { type string; description "Id of the agent for which we are defining the symptoms. This identifier must be unique among all agents."; } list symptoms-description { key "symptom-id"; description "List of symptoms raised by the current agent, identified Claise, et al. Expires 11 February 2023 [Page 16] Internet-Draft YANG Modules for Service Assurance August 2022 by their symptom-id."; leaf symptom-id { type string; description "Id of the symptom for the current agent. The agent must guarantee the unicity of this identifier."; } leaf description { type string; mandatory true; description "Description of the symptom, i.e., text describing what the symptom is, to be computer-consumable and be displayed on a human interface. It is not intended for random end users but for network/system/software engineers that are able to interpret it. Therefore, no mechanism for language tagging is needed."; } } } list assured-services { key "service"; config false; description "Types of service that are currently part of the assurance graph. The list must contain an entry for every service type that is currently present in the assurance graph. This list presents an alternate access to the graph stored in /subservices that optimizes querying the assurance graph of a specific service instance."; leaf service { type leafref { path "/subservices/subservice/service-instance-parameter/" + "service"; } description "Name of the service type."; } list instances { key "instance-name"; description "Instances of the parent service type. The list must contain an entry for every instance of the parent service."; leaf instance-name { type leafref { path "/subservices/subservice/service-instance-parameter/" + "instance-name"; Claise, et al. Expires 11 February 2023 [Page 17] Internet-Draft YANG Modules for Service Assurance August 2022 } description "Name of the service instance. The leafref must point to a service-instance-parameter whose service leaf matches the parent service."; } list subservices { key "type id"; description "Subservices that appear in the assurance graph of the current service instance. The list must contain the subservice corresponding to the service instance, that is the subservice that matches the service and instance-name keys. For every subservice in the list, all subservices listed as dependencies must also appear in the list."; uses subservice-reference; } } } } 3.4. Rejecting Circular Dependencies The statuses of services and subservices depend on the statuses of their dependencies, and thus circular dependencies between them prevents the computation of statuses. The SAIN architecture document [I-D.ietf-opsawg-service-assurance-architecture] discusses in Section 3.1.1 how such dependencies appear and how they could be removed. The responsibility of avoiding such dependencies falls to the SAIN orchestrator. However, we specify in this section the expected behavior when a server supporting the ietf-service-assurance module receives a data instance containing circular dependencies. Enforcing the absence of circular dependencies as a YANG constraint falls back to implementing a graph traversal algorithm with XPath and checking that the current node is not reachable from its dependencies. Even with such a constraint, there is no guarantee that merging two graphs without dependency loops will result in a graph without dependency loops. Indeed, the Section 3.1.1 of [I-D.ietf-opsawg-service-assurance-architecture] presents an example where merging two graphs without dependency loops results in a graph with a dependency loop. Claise, et al. Expires 11 February 2023 [Page 18] Internet-Draft YANG Modules for Service Assurance August 2022 Therefore, a server implementing the ietf-service-assurance module MUST check that there is no dependency loop whenever the graph is modified. A modification creating a dependency loop MUST be rejected. 4. Subservice Augmentation: ietf-service-assurance-device YANG module 4.1. Tree View The following tree diagram [RFC8340] provides an overview of the "ietf-service-assurance-device" module. module: ietf-service-assurance-device augment /sain:subservices/sain:subservice/sain:parameter: +--rw parameters +--rw device string A complete tree view of the base module with all augmenting modules presented in this draft is available in Appendix B.3. 4.2. Concepts As the number of subservices will grow over time, the YANG module is designed to be extensible. A new subservice type requires the precise specifications of its type and expected parameters. Let us illustrate the example of the new device subservice type. As the name implies, it monitors and reports the device health, along with some symptoms in case of degradation. For our device subservice definition, the new identity "device-type" is specified, as an inheritance from the base identity for subservices. This indicates to the assurance agent that we are now assuring the health of a device. The typical parameter for the configuration of the device subservice is the name of the device that we want to assure. By augmenting the parameter choice from ietf-service-assurance YANG module for the case of the "device-type" subservice type, this new parameter is specified. 4.3. YANG Module file "ietf-service-assurance-device@2022-04-07.yang" Claise, et al. Expires 11 February 2023 [Page 19] Internet-Draft YANG Modules for Service Assurance August 2022 module ietf-service-assurance-device { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-service-assurance-device"; prefix sain-device; import ietf-service-assurance { prefix sain; reference "RFC xxxx: YANG Modules for Service Assurance"; } organization "IETF OPSAWG Working Group"; contact "WG Web: WG List: Author: Benoit Claise Author: Jean Quilbeuf "; description "This module augments the ietf-service-assurance module with support of the device subservice. 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; see the RFC itself for full legal notices. "; revision 2022-08-10 { description "Initial revision."; reference "RFC xxxx: YANG Modules for Service Assurance"; } identity device-type { base sain:subservice-base; description "Identity of device subservice."; } Claise, et al. Expires 11 February 2023 [Page 20] Internet-Draft YANG Modules for Service Assurance August 2022 augment "/sain:subservices/sain:subservice/sain:parameter" { when "derived-from-or-self(sain:type, 'device-type')"; description "Augments the parameter choice from ietf-service-assurance module with a case specific to the device subservice."; container parameters { description "Parameters for the device subservice type"; leaf device { type string; mandatory true; description "Identifier of the device to monitor. The identifier (device id, hostname, management IP) depends on the context."; } } } } 5. Subservice Augmentation: ietf-service-assurance-interface YANG module 5.1. Tree View The following tree diagram [RFC8340] provides an overview of the ietf-service-assurance-interface data model. module: ietf-service-assurance-interface augment /sain:subservices/sain:subservice/sain:parameter: +--rw parameters +--rw device string +--rw interface string A complete tree view of the base module with all augmenting modules presented in this draft is available in Appendix B.3. 5.2. Concepts For the interface subservice definition, the new interface-type is specified, as an inheritance from the base identity for subservices. This indicates to the assurance agent that we are now assuring the health of an interface. Claise, et al. Expires 11 February 2023 [Page 21] Internet-Draft YANG Modules for Service Assurance August 2022 The typical parameters for the configuration of the interface subservice are the name of the device and, on that specific device, a specific interface. By augmenting the parameter choice from ietf- service-assurance YANG module for the case of the interface-type subservice type, those two new parameters are specified. 5.3. YANG Module file "ietf-service-assurance-interface@2022-04-07.yang" module ietf-service-assurance-interface { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-service-assurance-interface"; prefix sain-interface; import ietf-service-assurance { prefix sain; reference "RFC xxxx: YANG Modules for Service Assurance"; } organization "IETF OPSAWG Working Group"; contact "WG Web: WG List: Author: Benoit Claise Author: Jean Quilbeuf "; description "This module extends the ietf-service-assurance module to add support for the interface subservice. Checks whether an interface is healthy. 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; see the RFC itself for full legal notices. "; revision 2022-08-10 { Claise, et al. Expires 11 February 2023 [Page 22] Internet-Draft YANG Modules for Service Assurance August 2022 description "Initial revision."; reference "RFC xxxx: YANG Modules for Service Assurance"; } identity interface-type { base sain:subservice-base; description "Checks whether an interface is healthy."; } augment "/sain:subservices/sain:subservice/sain:parameter" { when "derived-from-or-self(sain:type, 'interface-type')"; description "Augments the parameter choice from ietf-service-assurance module with a case specific to the interface subservice."; container parameters { description "Parameters for the interface subservice type."; leaf device { type string; mandatory true; description "Device supporting the interface."; } leaf interface { type string; mandatory true; description "Name of the interface."; } } } } 6. Security Considerations The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446]. Claise, et al. Expires 11 February 2023 [Page 23] Internet-Draft YANG Modules for Service Assurance August 2022 The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. There are a number of data nodes defined in this YANG module that are writable/ creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability: * /subservices/subservice/type * /subservices/subservice/id * /subservices/subservice/maintenance-contact Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability: * /subservices/subservice : Each of these nodes might be a service or a subservice and by following the dependencies, one might get information about the underlying network. For instance, a customer might be given access to monitor their services status (e.g. via model-driven telemetry). In that example, the customer access should be restricted to nodes representing their services, so as not to divulge information about the underlying network structure or others customers services. 7. IANA Considerations 7.1. The IETF XML Registry This document registers two URIs in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registrations are requested: Claise, et al. Expires 11 February 2023 [Page 24] Internet-Draft YANG Modules for Service Assurance August 2022 URI: urn:ietf:params:xml:ns:yang:ietf-service-assurance Registrant Contact: The OPSAWG WG of the IETF. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-service-assurance-device Registrant Contact: The OPSAWG WG of the IETF. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-service-assurance-interface Registrant Contact: The OPSAWG WG of the IETF. XML: N/A, the requested URI is an XML namespace. 7.2. The YANG Module Names Registry This document registers three YANG modules in the YANG Module Names registry [RFC7950]. Following the format in [RFC7950], the following registrations are requested: name: ietf-service-assurance namespace: urn:ietf:params:xml:ns:yang:ietf-service-assurance prefix: sain reference: RFC XXXX name: ietf-service-assurance-device namespace: urn:ietf:params:xml:ns:yang:ietf-service-assurance-device prefix: sain-device reference: RFC XXXX name: ietf-service-assurance-interface namespace: urn:ietf:params:xml:ns:yang:ietf-service-assurance-interface prefix: sain-interface reference: RFC XXXX All these modules are not maintained by IANA. 8. References 8.1. Normative References [I-D.ietf-opsawg-service-assurance-architecture] Claise, B., Quilbeuf, J., Lopez, D. R., Voyer, D., and T. Arumugam, "Service Assurance for Intent-based Networking Architecture", Work in Progress, Internet-Draft, draft- ietf-opsawg-service-assurance-architecture-07, July 2022, . Claise, et al. Expires 11 February 2023 [Page 25] Internet-Draft YANG Modules for Service Assurance August 2022 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [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, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, . [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, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . 8.2. Informative References Claise, et al. Expires 11 February 2023 [Page 26] Internet-Draft YANG Modules for Service Assurance August 2022 [RFC7895] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module Library", RFC 7895, DOI 10.17487/RFC7895, June 2016, . [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, . Appendix A. Vendor-specific Subservice Augmentation: example-service- assurance-device-acme YANG module A.1. Tree View The following tree diagram [RFC8340] provides an overview of the "example-service-assurance-device-acme" module. module: example-service-assurance-device-acme augment /sain:subservices/sain:subservice/sain:parameter: +--rw parameters +--rw device string +--rw acme-specific-parameter string A complete tree view of the base module with all augmenting modules presented in this draft is available in Appendix B.3. A.2. Concepts Under some circumstances, vendor-specific subservice types might be required. As an example of this vendor-specific implementation, this section shows how to augment the "ietf-service-assurance-device" module to add custom support for the device subservice, specific to the ACME Corporation. The specific version adds a new parameter, named "acme-specific-parameter". It's an implementation choice to either augment the identity from ietf-service-assurance or to augment the parameters from ietf-service-assurance-device, here we choose to augment the identity. A.3. YANG Module module example-service-assurance-device-acme { yang-version 1.1; namespace "urn:example:example-service-assurance-device-acme"; prefix example-device-acme; import ietf-service-assurance { prefix sain; Claise, et al. Expires 11 February 2023 [Page 27] Internet-Draft YANG Modules for Service Assurance August 2022 reference "RFC xxxx: YANG Modules for Service Assurance"; } import ietf-service-assurance-device { prefix sain-device; reference "RFC xxxx: YANG Modules for Service Assurance"; } organization "IETF OPSAWG Working Group"; contact "WG Web: WG List: Author: Benoit Claise Author: Jean Quilbeuf "; description "This module extends the ietf-service-assurance-device module to add specific support for devices of ACME Corporation. "; revision 2022-08-10 { description "Initial revision"; reference "RFC xxxx: YANG Modules for Service Assurance"; } identity device-acme-type { base sain-device:device-type; description "Network Device is healthy."; } augment "/sain:subservices/sain:subservice/sain:parameter" { when "derived-from-or-self(sain:type, 'device-acme-type')"; description "Augments the parameter choice from ietf-service-assurance module with a case specific to the device-acme subservice."; container parameters { description "Parameters for the device-acme subservice type"; leaf device { type string; mandatory true; description "The device to monitor."; } leaf acme-specific-parameter { Claise, et al. Expires 11 February 2023 [Page 28] Internet-Draft YANG Modules for Service Assurance August 2022 type string; mandatory true; description "The ACME Corporation specific parameter."; } } } } Appendix B. Further Augmentations: IP Connectivity and IS-IS subservices In this section, we provide two additional YANG modules to completely cover the example in Figure 2 from Section 3.1 of [I-D.ietf-opsawg-service-assurance-architecture]. These modules are presented as examples, some future work is needed to propose a more complete version. B.1. IP Connectivity Tree View That subservice represents the unicast connectivity between two IP addresses located on two different devices. Such a subservice could report symptoms such as "No route found". The following tree diagram [RFC8340] provides an overview of the "example-service-assurance-ip- connectivity" module. module: example-service-assurance-ip-connectivity augment /sain:subservices/sain:subservice/sain:parameter: +--rw parameters +--rw device1 string +--rw address1 inet:ip-address +--rw device2 string +--rw address2 inet:ip-address To specify the connectivity that we are interested in, we specify two IP addresses and two devices. The subservice assures that the connectivity between IP address 1 on device 1 and IP address 2 on device 2 is healthy. B.2. IS-IS Tree View The following tree diagram [RFC8340] provides an overview of the "example-service-assurance-is-is" module. Claise, et al. Expires 11 February 2023 [Page 29] Internet-Draft YANG Modules for Service Assurance August 2022 module: example-service-assurance-is-is augment /sain:subservices/sain:subservice/sain:parameter: +--rw parameters +--rw instance-name string The parameter of this subservice is the name of the IS-IS instance to assure. B.3. Global Tree View The following tree diagram [RFC8340] provides an overview of the "ietf-service-assurance", "ietf-service-assurance-device", "example- service-assurance-device-acme", "example-service-assurance-ip- connectivity" and "example-service-assurance-is-is" modules. module: ietf-service-assurance +--ro assurance-graph-last-change yang:date-and-time +--rw subservices | +--rw subservice* [type id] | +--rw type identityref | +--rw id string | +--ro last-change? | | yang:date-and-time | +--ro label? string | +--rw maintenance-contact? string | +--rw (parameter) | | +--:(service-instance-parameter) | | | +--rw service-instance-parameter | | | +--rw service string | | | +--rw instance-name string | | +--:(example-ip-connectivity:parameters) | | | +--rw example-ip-connectivity:parameters | | | +--rw example-ip-connectivity:device1 string | | | +--rw example-ip-connectivity:address1 | | | | inet:ip-address | | | +--rw example-ip-connectivity:device2 string | | | +--rw example-ip-connectivity:address2 | | | inet:ip-address | | +--:(example-is-is:parameters) | | | +--rw example-is-is:parameters | | | +--rw example-is-is:instance-name string | | +--:(sain-device:parameters) | | | +--rw sain-device:parameters | | | +--rw sain-device:device string | | +--:(example-device-acme:parameters) | | | +--rw example-device-acme:parameters Claise, et al. Expires 11 February 2023 [Page 30] Internet-Draft YANG Modules for Service Assurance August 2022 | | | +--rw example-device-acme:device | | | | string | | | +--rw example-device-acme:acme-specific-parameter | | | string | | +--:(sain-interface:parameters) | | +--rw sain-interface:parameters | | +--rw sain-interface:device string | | +--rw sain-interface:interface string | +--ro health-score? union | +--ro symptoms-history-start? | | yang:date-and-time | +--ro symptoms | | +--ro symptom* [start-date-time agent-id symptom-id] | | +--ro symptom-id | | | -> /agents/symptoms-description/symptom-id | | +--ro agent-id -> /agents/agent-id | | +--ro health-score-weight? uint8 | | +--ro start-date-time yang:date-and-time | | +--ro stop-date-time? yang:date-and-time | +--rw dependencies | +--rw dependency* [type id] | +--rw type | | -> /subservices/subservice/type | +--rw id leafref | +--rw dependency-type? identityref +--ro agents* [agent-id] | +--ro agent-id string | +--ro symptoms-description* [symptom-id] | +--ro symptom-id string | +--ro description string +--ro assured-services* [service] +--ro service leafref +--ro instances* [instance-name] +--ro instance-name leafref +--ro subservices* [type id] +--ro type -> /subservices/subservice/type +--ro id leafref B.4. IP Connectivity YANG Module module example-service-assurance-ip-connectivity { yang-version 1.1; namespace "urn:example:example-service-assurance-ip-connectivity"; prefix example-ip-connectivity; import ietf-inet-types { prefix inet; Claise, et al. Expires 11 February 2023 [Page 31] Internet-Draft YANG Modules for Service Assurance August 2022 reference "RFC 6991: Common YANG Data Types"; } import ietf-service-assurance { prefix sain; reference "RFC xxxx: YANG Modules for Service Assurance"; } organization "IETF OPSAWG Working Group"; contact "WG Web: WG List: Author: Benoit Claise Author: Jean Quilbeuf "; description "This example module augments the ietf-service-assurance module to add support for the subservice ip-connectivity. Checks whether the ip connectivity between two ip addresses belonging to two network devices is healthy."; revision 2022-08-10 { description "Initial version"; reference "RFC xxxx: YANG Modules for Service Assurance"; } identity ip-connectivity-type { base sain:subservice-base; description "Checks connectivity between two IP addresses."; } augment "/sain:subservices/sain:subservice/sain:parameter" { when "derived-from-or-self(sain:type, 'ip-connectivity-type')"; description "Augments the parameter choice from ietf-service-assurance module with a case specific to the ip-connectivity subservice."; container parameters { description "Parameters for the ip-connectivity subservice type"; leaf device1 { type string; mandatory true; Claise, et al. Expires 11 February 2023 [Page 32] Internet-Draft YANG Modules for Service Assurance August 2022 description "Device at the first end of the connection."; } leaf address1 { type inet:ip-address; mandatory true; description "Address at the first end of the connection."; } leaf device2 { type string; mandatory true; description "Device at the second end of the connection."; } leaf address2 { type inet:ip-address; mandatory true; description "Address at the second end of the connection."; } } } } B.5. IS-IS YANG Module module example-service-assurance-is-is { yang-version 1.1; namespace "urn:example:example-service-assurance-is-is"; prefix example-is-is; import ietf-service-assurance { prefix sain; reference "RFC xxxx: YANG Modules for Service Assurance"; } organization "IETF OPSAWG Working Group"; contact "WG Web: WG List: Author: Benoit Claise Author: Jean Quilbeuf "; description "This example module augments the ietf-service-assurance module to Claise, et al. Expires 11 February 2023 [Page 33] Internet-Draft YANG Modules for Service Assurance August 2022 add support for the subservice is-is. Checks whether an IS-IS instance is healthy."; revision 2022-08-10 { description "Initial version"; reference "RFC xxxx: YANG Modules for Service Assurance"; } identity is-is-type { base sain:subservice-base; description "Health of IS-IS routing protocol."; } augment "/sain:subservices/sain:subservice/sain:parameter" { when "derived-from-or-self(sain:type, 'is-is-type')"; description "Augments the parameter choice from ietf-service-assurance module with a case specific to the is-is subservice."; container parameters { description "Parameters for the is-is subservice type."; leaf instance-name { type string; mandatory true; description "The instance to monitor."; } } } } Appendix C. Example of YANG instances This section contains examples of YANG instances that conform to the YANG modules. The validity of these data instances has been checked using yangson (https://yangson.labs.nic.cz/). Yangson requires a YANG library [RFC7895] to define the complete model against which the data instance must be validated. We provide in Appendix D the JSON library file, named "ietf-service-assurance-library.json", that we used for validation. Claise, et al. Expires 11 February 2023 [Page 34] Internet-Draft YANG Modules for Service Assurance August 2022 We provide below the contents of the file "example_configuration_instance.json" which contains the configuration data that models the Figure 2 from Section 3.1 of [I-D.ietf-opsawg-service-assurance-architecture]. The instance can be validated with yangson by using the invocation "yangson -v example_configuration_instance.json ietf-service-assurance- library.json", assuming all the files (YANG and JSON) defined in this draft reside in the current folder. { "ietf-service-assurance:subservices": { "subservice": [ { "type": "service-instance-type", "id": "simple-tunnel/example", "service-instance-parameter": { "service": "simple-tunnel", "instance-name": "example" }, "dependencies": { "dependency": [ { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer1/tunnel0", "dependency-type": "impacting" }, { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer2/tunnel9", "dependency-type": "impacting" }, { "type": "example-service-assurance-ip-connectivity:ip-connectivity-type", "id": "connectivity/peer1/2001:db8::1/peer2/2001:db8::2", "dependency-type": "impacting" } ] } }, { "type": "example-service-assurance-ip-connectivity:ip-connectivity-type", "id": "connectivity/peer1/2001:db8::1/peer2/2001:db8::2", "example-service-assurance-ip-connectivity:parameters": { "device1": "Peer1", "address1": "2001:db8::1", "device2": "Peer2", Claise, et al. Expires 11 February 2023 [Page 35] Internet-Draft YANG Modules for Service Assurance August 2022 "address2": "2001:db8::2" }, "dependencies": { "dependency": [ { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer1/physical0", "dependency-type": "impacting" }, { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer2/physical5", "dependency-type": "impacting" }, { "type": "example-service-assurance-is-is:is-is-type", "id": "is-is/instance1", "dependency-type": "impacting" } ] } }, { "type": "example-service-assurance-is-is:is-is-type", "id": "is-is/instance1", "example-service-assurance-is-is:parameters": { "instance-name": "instance1" } }, { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer1/tunnel0", "ietf-service-assurance-interface:parameters": { "device": "Peer1", "interface": "tunnel0" }, "dependencies": { "dependency": [ { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer1/physical0", "dependency-type": "impacting" } ] } }, { "type": "ietf-service-assurance-interface:interface-type", Claise, et al. Expires 11 February 2023 [Page 36] Internet-Draft YANG Modules for Service Assurance August 2022 "id": "interface/peer1/physical0", "ietf-service-assurance-interface:parameters": { "device": "Peer1", "interface": "physical0" }, "dependencies": { "dependency": [ { "type": "ietf-service-assurance-device:device-type", "id": "interface/peer1", "dependency-type": "impacting" } ] } }, { "type": "ietf-service-assurance-device:device-type", "id": "interface/peer1", "ietf-service-assurance-device:parameters": { "device": "Peer1" } }, { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer2/tunnel9", "ietf-service-assurance-interface:parameters": { "device": "Peer2", "interface": "tunnel9" }, "dependencies": { "dependency": [ { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer2/physical5", "dependency-type": "impacting" } ] } }, { "type": "ietf-service-assurance-interface:interface-type", "id": "interface/peer2/physical5", "ietf-service-assurance-interface:parameters": { "device": "Peer2", "interface": "physical5" }, "dependencies": { "dependency": [ Claise, et al. Expires 11 February 2023 [Page 37] Internet-Draft YANG Modules for Service Assurance August 2022 { "type": "ietf-service-assurance-device:device-type", "id": "interface/peer2", "dependency-type": "impacting" } ] } }, { "type": "ietf-service-assurance-device:device-type", "id": "interface/peer2", "ietf-service-assurance-device:parameters": { "device": "Peer2" } } ] } } Appendix D. YANG Library for Service Assurance This section provides the JSON encoding of the YANG library [RFC7895] listing all modules defined in this draft and their dependencies. This library can be used to validate data instances using yangson, as explained in the previous section. { "ietf-yang-library:modules-state": { "module-set-id": "ietf-service-assurance@2022-08-10", "module": [ { "name": "ietf-service-assurance", "namespace": "urn:ietf:params:xml:ns:yang:ietf-service-assurance", "revision": "2022-08-10", "conformance-type": "implement" }, { "name": "ietf-service-assurance-device", "namespace": "urn:ietf:params:xml:ns:yang:ietf-service-assurance-device", "revision": "2022-08-10", "conformance-type": "implement" }, { "name": "ietf-service-assurance-interface", Claise, et al. Expires 11 February 2023 [Page 38] Internet-Draft YANG Modules for Service Assurance August 2022 "namespace": "urn:ietf:params:xml:ns:yang:ietf-service-assurance-interface", "revision": "2022-08-10", "conformance-type": "implement" }, { "name": "example-service-assurance-device-acme", "namespace": "urn:example:example-service-assurance-device-acme", "revision": "2022-08-10", "conformance-type": "implement" }, { "name": "example-service-assurance-is-is", "namespace": "urn:example:example-service-assurance-is-is", "revision": "2022-08-10", "conformance-type": "implement" }, { "name": "example-service-assurance-ip-connectivity", "namespace": "urn:example:example-service-assurance-ip-connectivity", "revision": "2022-08-10", "conformance-type": "implement" }, { "name": "ietf-yang-types", "namespace": "urn:ietf:params:xml:ns:yang:ietf-yang-types", "revision": "2021-04-14", "conformance-type": "import" }, { "name": "ietf-inet-types", "namespace": "urn:ietf:params:xml:ns:yang:ietf-inet-types", "revision": "2021-02-22", "conformance-type": "import" } ] } } Appendix E. Changes between revisions v06 - v07 Claise, et al. Expires 11 February 2023 [Page 39] Internet-Draft YANG Modules for Service Assurance August 2022 * Addressed early YANG doctor comments from version -06: changed -idty for -type or -base in identity names and removed "under- maintenance" leaf * Add new list of services with the corresponding subservices * Remove assurance-graph-version and state the limitations of having only the current graph available in the module. * Added new list of agents to store symptom and guarantee unicity of symptom ids * Added security consideration for readable nodes * Added section on rejecting circular dependencies v05 - v06 * Remove revision history in modules * Present elements in order of the tree for the main module * Rewriting and rewording for clarity * Made parameters mandatory for the subservices v04 - v05 * Remove Guidelines section * Move informative parts (examples) to appendix * Minor text edits and reformulations v03 - v04 * Fix YANG errors * Change is-is and ip-connectivity subservices from ietf to example. * Mention that models are NMDA compliant * Fix typos, reformulate for clarity v02 - v03 * Change counter32 to counter64 to avoid resetting too frequently Claise, et al. Expires 11 February 2023 [Page 40] Internet-Draft YANG Modules for Service Assurance August 2022 * Explain why relation between health-score and symptom's health- score-weight is not defined and how it could be defined v01 - v02 * Explicitly represent the fact that the health-score could not be computed (value -1) v00 - v01 * Added needed subservice to model example from architecture draft * Added guideline section for naming models * Added data instance examples and validation procedure * Added the "parameters" container in the interface YANG module to correct a bug. Acknowledgements The authors would like to thank Jan Lindblad for his help during the design of these YANG modules. The authors would like to thank Stephane Litkowski, Charles Eckel, Mohamed Boucadair, Tom Petch and Dhruv Dhody for their reviews. Authors' Addresses Benoit Claise Huawei Email: benoit.claise@huawei.com Jean Quilbeuf Huawei Email: jean.quilbeuf@huawei.com Paolo Lucente NTT Siriusdreef 70-72 2132 Hoofddorp Netherlands Email: paolo@ntt.net Claise, et al. Expires 11 February 2023 [Page 41] Internet-Draft YANG Modules for Service Assurance August 2022 Paolo Fasano TIM S.p.A via G. Reiss Romoli, 274 10148 Torino Italy Email: paolo2.fasano@telecomitalia.it Thangam Arumugam Cisco Systems, Inc. Milpitas (California), United States Email: tarumuga@cisco.com Claise, et al. Expires 11 February 2023 [Page 42]