YANG Notification Transport Capabilities

Notification capabilities model defined in allows a client to discover a set of capabilities supported by the server (e.g., basic system capabilities and YANG-Push related capabilities) both at implementation time and at runtime. These capabilities allow the client to adjust its behavior to take advantage of the features exposed by the server. However the client and the server may still support various different transport specific parameters (e.g., transport protocol, encoding format, encryption). As described in , a simple negotiation (i.e., inserting hints into error responses to a failed RPC request) between subscribers and publishers for subscription parameters increases the likelihood of success for subsequent RPC requests, but not guaranteed, which may cause unexpected failure or additional message exchange between client and server. This document defines a corresponding solution by proposing a YANG module for YANG notifications transport capabilities that is built on top of . The module can be used by the client to discover capability information from the server at runtime or at implementation time, by making use of the YANG instance data file format.

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.

The YANG module "ietf-notification-capabilities" defined in specifies the following server capabilities related to YANG Push: Supported (reporting) periods for "periodic" subscriptions Maximum number of objects that can be sent in an update The set of datastores or data nodes for which "periodic" or "on-change" notification is supported Supported dampening periods for "on-change" subscriptions These server capabilities are transport independent, session level capabilities. They can be provided either at the implementation time or reported at runtime. This document augments System Capabilities model and provides additional transport related attributes associated with system capabilities: Specification of transport protocols the client can request to establish a HTTPS-based or UDP-based configured transport connection; Specification of transport encoding, such as JSON or XML as defined in or CBOR as defined in the client can request to encode YANG notifications; Specification of secure transport mechanisms that are needed by the client to communicate with the server such as DTLS as defined in TLS as defined in or SSH as defined in ;

The following tree diagram provides an overview of the data model.

WG List: Authors: Qin Wu Qiufang Ma Alex Huang Feng Thomas Graf "; description "This module defines an extension to System Capability and YANG Push Notification Capabilities model and provides additional transport specific capabilities for YANG notifications. Copyright (c) 2024 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://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 2024-10-14 { description "Initial revision."; reference "RFC XXXX: YANG Notifications Transport Capabilities"; } identity security-protocol { description "Identity for security protocols."; } identity tls { base security-protocol; description "Identity for TLS security protocol."; } identity dtls12 { base security-protocol; description "Identity for DTLS 1.2 security protocol."; } identity dtls13 { base security-protocol; description "Identity for DTLS 1.3 security protocol."; } identity ssh { base security-protocol; description "Identity for ssh transport protocol."; } augment "/sysc:system-capabilities/notc:subscription-capabilities" { description "Add system level capability."; container transport-capabilities { description "Capabilities related to YANG-Push transports."; list transport-capability { key "transport-protocol"; description "Capability list related to notification transport capabilities."; leaf transport-protocol { type identityref { base sn:transport; } description "Supported transport protocol for YANG-Push."; } leaf security-protocol { type identityref { base security-protocol; } description "Type of secure transport."; } leaf-list encoding-format { type identityref { base sn:encoding; } description "Supported encoding formats."; } } } } } ]]>

This document registers a URI in the "IETF XML Registry" [RFC3688]. Following the format in [RFC3688], the following registration has been made:

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

This document registers one YANG module in the "YANG Module Names" registry [RFC6020]. Following the format in [RFC6020], the following registration has been made:

name: ietf-notification-transport-capabilities namespace: urn:ietf:params:xml:ns:yang:ietf-notification-transport-capabilities prefix: ntc reference: RFC XXXX (RFC Ed.: replace XXX with actual RFC number and remove this note.)

This section is modeled after the template described in The "ietf-notification-transport-capabilities" YANG module defines a data model that is designed to be accessed via YANG-based management protocols, such as NETCONF and RESTCONF . These protocols have to use a secure transport layer (e.g., SSH , TLS , and QUIC ) and have to use mutual authentication. The Network Configuration Access Control Model (NACM) 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. All protocol-accessible data nodes are read-only and cannot be modified. The data in the module is not security sensitive. It inherits all the security considerations of .

Ran Tao Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: taoran20@huawei.com Liang Geng China Mobile 32 Xuanwumen West St, Xicheng District Beijing 10053 China Email: gengliang@chinamobile.com Peng Liu China Mobile Beiqijia Town, Changping District Beijing 10053 China Email: liupengyjy@chinamobile.com Wei Wang China Telecom 32 Xuanwumen West St, Xicheng District Beijing 102209 China Email: wangw36@chinatelecom.cn

The following instance-data example describes the notification transport capabilities of a hypothetical "acme-router".

<?xml version="1.0" encoding="UTF-8"?> <instance-data-set xmlns= "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data"> <name>acme-router-notification-capabilities</name> <content-schema> <module>ietf-system-capabilities@2020-03-23</module> <module>ietf-notification-capabilities@2020-03-23</module> <module>ietf-notification-transport-capabilities@2024-10-14</module> </content-schema>  <description>Server Capability Discovery</description> <content-data> <system-capabilities xmlns="urn:ietf:params:xml:ns:yang:ietf-system\ -capabilities"> <subscription-capabilities xmlns="urn:ietf:params:xml:ns:yang:iet\ f-notification-capabilities"> <transport-capabilities xmlns="urn:ietf:params:xml:ns:yang:ietf\ -notification-transport-capabilities"> <transport-capability> <transport-protocol xmlns:hnt="urn:ietf:params:xml:ns:yang:\ ietf-https-notif-transport">hnt:https</transport-protocol> <encoding-format xmlns:sn="urn:ietf:params:xml:ns:yang:ietf\ -subscribed-notifications">sn:encode-xml</encoding-format> <encoding-format xmlns:sn="urn:ietf:params:xml:ns:yang:ietf\ -subscribed-notifications">sn:encode-json</encoding-format> </transport-capability> <transport-capability> <transport-protocol xmlns:unt="urn:ietf:params:xml:ns:yang:\ ietf-udp-notif-transport">unt:udp-notif</transport-protocol> <encoding-format xmlns:unt="urn:ietf:params:xml:ns:yang:iet\ f-udp-notif-transport">unt:encode-cbor</encoding-format> </transport-capability> </transport-capabilities> </subscription-capabilities> </system-capabilities> </content-data> </instance-data-set> In addition, the client could also query notification transport capabilities from the server. For example, the client sends <get> request message to the the server to query from the server.

<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <get> <filter type="subtree"> <system-capabilities xmlns="urn:ietf:params:xml:ns:yang:ietf-syste\ m-capabilities"> <subscription-capabilities xmlns="urn:ietf:params:xml:ns:yang:ie\ tf-notification-capabilities"> <transport-capabilities/> </subscription-capabilities> </system-capabilities> </filter> </get> </rpc> The server returns server data export capability using <rpc-reply> as follows:

<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="101"> <data> <system-capabilities xmlns="urn:ietf:params:xml:ns:yang:ietf-system\ -capabilities"> <subscription-capabilities xmlns="urn:ietf:params:xml:ns:yang:iet\ f-notification-capabilities"> <transport-capabilities xmlns="urn:ietf:params:xml:ns:yang:ietf\ -notification-transport-capabilities"> <transport-capability> <transport-protocol xmlns:hnt="urn:ietf:params:xml:ns:yang:\ ietf-https-notif-transport">hnt:https</transport-protocol> <encoding-format xmlns:sn="urn:ietf:params:xml:ns:yang:ietf\ -subscribed-notifications">sn:encode-xml</encoding-format> <encoding-format xmlns:sn="urn:ietf:params:xml:ns:yang:ietf\ -subscribed-notifications">sn:encode-json</encoding-format> </transport-capability> <transport-capability> <transport-protocol xmlns:unt="urn:ietf:params:xml:ns:yang:\ ietf-udp-notif-transport">unt:udp-notif</transport-protocol> <encoding-format xmlns:unt="urn:ietf:params:xml:ns:yang:iet\ f-udp-notif-transport">unt:encode-cbor</encoding-format> </transport-capability> </transport-capabilities> </subscription-capabilities> </system-capabilities> </data> </rpc-reply>