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rfc:rfc8527

Internet Engineering Task Force (IETF) M. Bjorklund Request for Comments: 8527 Tail-f Systems Updates: 8040 J. Schoenwaelder Category: Standards Track Jacobs University ISSN: 2070-1721 P. Shafer

                                                      Juniper Networks
                                                             K. Watsen
                                                       Watsen Networks
                                                             R. Wilton
                                                         Cisco Systems
                                                            March 2019
                 RESTCONF Extensions to Support the
             Network Management Datastore Architecture

Abstract

 This document extends the RESTCONF protocol defined in RFC 8040 in
 order to support the Network Management Datastore Architecture (NMDA)
 defined in RFC 8342.
 This document updates RFC 8040 by introducing new datastore
 resources, adding a new query parameter, and requiring the usage of
 the YANG library (described in RFC 8525) by RESTCONF servers
 implementing the NMDA.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 https://www.rfc-editor.org/info/rfc8527.

Bjorklund, et al. Standards Track [Page 1] RFC 8527 RESTCONF Extensions for the NMDA March 2019

Copyright Notice

 Copyright (c) 2019 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 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 Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................3
    1.1. Terminology ................................................3
 2. Datastore and YANG Library Requirements .........................3
 3. RESTCONF Extensions .............................................4
    3.1. New Datastore Resources ....................................4
    3.2. Protocol Operations ........................................5
         3.2.1. The "with-defaults" Query Parameter on the
                Operational State Datastore .........................5
         3.2.2. New "with-origin" Query Parameter ...................6
 4. IANA Considerations .............................................7
 5. Security Considerations .........................................7
 6. Normative References ............................................7
 Authors' Addresses .................................................9

Bjorklund, et al. Standards Track [Page 2] RFC 8527 RESTCONF Extensions for the NMDA March 2019

1. Introduction

 This document extends the RESTCONF protocol defined in [RFC8040] in
 order to support the Network Management Datastore Architecture (NMDA)
 defined in [RFC8342].
 This document updates [RFC8040] in order to enable RESTCONF clients
 to discover which datastores are supported by the RESTCONF server,
 determine which modules are supported in each datastore, and interact
 with all the datastores supported by the NMDA.  Specifically, the
 update introduces new datastore resources, adds a new query
 parameter, and requires the usage of the YANG library [RFC8525] by
 RESTCONF servers implementing the NMDA.
 The solution presented in this document is backwards compatible with
 [RFC8040].  This is achieved by only adding new resources and leaving
 the semantics of the existing resources unchanged.

1.1. Terminology

 This document uses the terminology defined by the NMDA [RFC8342].
 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.

2. Datastore and YANG Library Requirements

 An NMDA-compliant RESTCONF server MUST support the operational state
 datastore and MUST implement at least revision 2019-01-04 of the
 "ietf-yang-library" module defined in [RFC8525].
 Such a server identifies that it supports the NMDA both by
 implementing the {+restconf}/ds/ietf-datastores:operational resource
 and by implementing at least revision 2019-01-04 of the
 "ietf-yang-library" module.
 A RESTCONF client can test if a server supports the NMDA by using
 either the HEAD or GET methods on {+restconf}/ds/ietf-
 datastores:operational.
 A RESTCONF client can discover which datastores and YANG modules the
 server supports by reading the YANG library information from the
 operational state datastore.

Bjorklund, et al. Standards Track [Page 3] RFC 8527 RESTCONF Extensions for the NMDA March 2019

3. RESTCONF Extensions

 This section describes the RESTCONF extensions needed to support the
 NMDA.

3.1. New Datastore Resources

 This document defines a set of new resources representing datastores
 as defined in [RFC8342].  These resources are available using the
 following resource path template:
   {+restconf}/ds/<datastore>
 The <datastore> path component is encoded as an "identityref"
 according to the JSON encoding rules for identities, defined in
 Section 6.8 of [RFC7951].  The namespace-qualified form MUST be used.
 Such an identity MUST be derived from the "datastore" identity
 defined in the "ietf-datastores" YANG module [RFC8342].
 Specifically:
 o  The resource {+restconf}/ds/ietf-datastores:operational refers to
    the operational state datastore.
 o  The resource {+restconf}/ds/ietf-datastores:running refers to the
    running configuration datastore.
 o  The resource {+restconf}/ds/ietf-datastores:intended refers to the
    intended configuration datastore.
 An NMDA-compliant server MUST implement {+restconf}/ds/ietf-
 datastores:operational.  Other datastore resources MAY be
 implemented.
 YANG actions can only be invoked in {+restconf}/ds/ietf-
 datastores:operational.
 As an example, if a server implements a datastore called
 "ds-ephemeral", defined in a module called "example-ds-ephemeral",
 then the server would implement the resource {+restconf}/ds/example-
 ds-ephemeral:ds-ephemeral.

Bjorklund, et al. Standards Track [Page 4] RFC 8527 RESTCONF Extensions for the NMDA March 2019

3.2. Protocol Operations

 The protocol operations available for the new datastore resources
 (see Section 3.1) are the same as the protocol operations defined in
 [RFC8040] for the {+restconf}/data resource with the following
 exceptions:
 o  Dynamic configuration datastores are excluded, as each dynamic
    configuration datastore definition needs to be reviewed for what
    protocol operations it supports.
 o  Some datastores are read-only by nature (e.g., <intended>); hence,
    any attempt to modify these datastores will fail.  A server MUST
    return a response with a "405 Method Not Allowed" status-line and
    an error-tag value of "operation-not-supported".
 o  The semantics of the "with-defaults" query parameter
    (Section 4.8.9 of [RFC8040]) differ when interacting with the
    operational state datastore.  The semantics are described in
    Section 3.2.1.
 o  [RFC8040], Section 3.5.4, paragraph 3 does not apply when
    interacting with any resource under {+restconf}/ds.

3.2.1. The "with-defaults" Query Parameter on the Operational State

      Datastore
 Support for the "with-defaults" query parameter (Section 4.8.9 of
 [RFC8040]) is OPTIONAL when interacting with {+restconf}/ds/ietf-
 datastores:operational.  The associated capability to indicate a
 server's support is identified with the URI:
   urn:ietf:params:restconf:capability:with-operational-defaults:1.0
 For servers that support it, the behavior of the "with-defaults"
 query parameter on the operational state datastore is defined as
 follows:
 o  If no "with-defaults" query parameter is specified, or if it is
    set to "explicit", "report-all", or "report-all-tagged", then the
    "in use" values, as defined in Section 5.3 of [RFC8342], are
    returned from the operational state datastore, even if a node
    happens to have a default statement in the YANG module and this
    default value is being used by the server.  If the "with-defaults"
    parameter is set to "report-all-tagged", any values that match the
    schema default are tagged with additional metadata, as described
    in Section 4.8.9 of [RFC8040].

Bjorklund, et al. Standards Track [Page 5] RFC 8527 RESTCONF Extensions for the NMDA March 2019

 o  If the "with-defaults" query parameter is set to "trim", all "in
    use" values are returned, except that the output is filtered to
    exclude any values that match the default defined in the YANG
    schema.
 Servers are not required to support all values in the "with-defaults"
 query parameter on the operational state datastore.  If a request is
 made using a value that is not supported, then the error handling
 behavior is as described in Section 4.8.9 of [RFC8040].

3.2.2. New "with-origin" Query Parameter

 A new query parameter named "with-origin" is added to the GET
 operation.  If present, it requests that the server includes "origin"
 metadata annotations in its response, as detailed in the NMDA.  This
 parameter is only valid when querying {+restconf}/ds/ietf-
 datastores:operational or any datastores with identities derived from
 the "operational" identity.  Otherwise, if an invalid datastore is
 specified, then the server MUST return a response with a "400 Bad
 Request" status-line, using an error-tag value of "invalid-value".
 "origin" metadata annotations are not included unless a client
 explicitly requests them.
 Data in the operational state datatstore can come from multiple
 sources.  The server should return the "origin" metadata annotation
 value that most accurately indicates the source of the operational
 value, as specified in Section 5.3.4 of [RFC8342].
 When encoding the "origin" metadata annotation for a hierarchy of
 returned nodes, the annotation can be omitted for a child node when
 the value matches that of the parent node, as described in the
 "ietf-origin" YANG module [RFC8342].
 Support for the "with-origin" query parameter is OPTIONAL.  It is
 identified with the URI:
   urn:ietf:params:restconf:capability:with-origin:1.0

Bjorklund, et al. Standards Track [Page 6] RFC 8527 RESTCONF Extensions for the NMDA March 2019

4. IANA Considerations

 This document defines two capability identifier URNs in the "RESTCONF
 Capability URNs" registry defined in [RFC8040]:
   Index
   Capability Identifier
   ---------------------
   :with-origin
   urn:ietf:params:restconf:capability:with-origin:1.0
   :with-operational-defaults
   urn:ietf:params:restconf:capability:with-operational-defaults:1.0

5. Security Considerations

 This document extends the RESTCONF protocol by introducing new
 datastore resources.  The lowest RESTCONF layer is HTTPS, and the
 mandatory-to-implement secure transport is TLS [RFC8446].  The
 RESTCONF protocol uses the network configuration access control model
 [RFC8341], which provides the means to restrict access for particular
 RESTCONF users to a preconfigured subset of all available RESTCONF
 protocol operations and content.
 The security constraints for the base RESTCONF protocol (see
 Section 12 of [RFC8040]) apply to the new RESTCONF datastore
 resources defined in this document.

6. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <https://www.rfc-editor.org/info/rfc2119>.
 [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
            RFC 7951, DOI 10.17487/RFC7951, August 2016,
            <https://www.rfc-editor.org/info/rfc7951>.
 [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
            Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
            <https://www.rfc-editor.org/info/rfc8040>.
 [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
            2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
            May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Bjorklund, et al. Standards Track [Page 7] RFC 8527 RESTCONF Extensions for the NMDA March 2019

 [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
            Access Control Model", STD 91, RFC 8341,
            DOI 10.17487/RFC8341, March 2018,
            <https://www.rfc-editor.org/info/rfc8341>.
 [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
            and R. Wilton, "Network Management Datastore Architecture
            (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
            <https://www.rfc-editor.org/info/rfc8342>.
 [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
            Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
            <https://www.rfc-editor.org/info/rfc8446>.
 [RFC8525]  Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
            and R. Wilton, "YANG Library", RFC 8525,
            DOI 10.17487/RFC8525, March 2019,
            <https://www.rfc-editor.org/info/rfc8525>.

Bjorklund, et al. Standards Track [Page 8] RFC 8527 RESTCONF Extensions for the NMDA March 2019

Authors' Addresses

 Martin Bjorklund
 Tail-f Systems
 Email: mbj@tail-f.com
 Juergen Schoenwaelder
 Jacobs University
 Email: j.schoenwaelder@jacobs-university.de
 Phil Shafer
 Juniper Networks
 Email: phil@juniper.net
 Kent Watsen
 Watsen Networks
 Email: kent+ietf@watsen.net
 Robert Wilton
 Cisco Systems
 Email: rwilton@cisco.com

Bjorklund, et al. Standards Track [Page 9]

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