Internet Engineering Task Force (IETF)
Request for Comments: 8527
Updates: 8040
Category: Standards Track
ISSN: 2070-1721

M. Bjorklund
Tail-f Systems
J. Schoenwaelder
Jacobs University
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.

Copyright Notice

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.

   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

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.

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.

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:

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".

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:

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].

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

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>.
   
   [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>.

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