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IETF RFC 8527
Last modified on Thursday, March 7th, 2019
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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/RFC 8527.
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 [RFC 8040] in
order to support the Network Management Datastore Architecture (NMDA)
defined in [RFC 8342].
This document updates [RFC 8040] 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 [RFC 8525] by
RESTCONF servers implementing the NMDA.
The solution presented in this document is backwards compatible with
[RFC 8040]. 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 [RFC 8342].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC 2119] [RFC 8174] when, and only when, they appear in all
capitals, as shown here.
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 [RFC 8525].
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 [RFC 8342]. 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 [RFC 7951]. The namespace-qualified form MUST be used.
Such an identity MUST be derived from the "datastore" identity
defined in the "ietf-datastores" YANG module [RFC 8342].
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
[RFC 8040] 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 [RFC 8040]) differ when interacting with the
operational state datastore. The semantics are described in
Section 3.2.1.
o [RFC 8040], 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
[RFC 8040]) 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 [RFC 8342], 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 [RFC 8040].
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 [RFC 8040].
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 [RFC 8342].
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 [RFC 8342].
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 [RFC 8040]:
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 [RFC 8446]. The
RESTCONF protocol uses the network configuration access control model
[RFC 8341], 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 [RFC 8040]) apply to the new RESTCONF datastore
resources defined in this document.
6. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<https://www.rfc-editor.org/info/RFC 2119>.
[RFC 7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC 7951, August 2016,
<https://www.rfc-editor.org/info/RFC 7951>.
[RFC 8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC 8040, January 2017,
<https://www.rfc-editor.org/info/RFC 8040>.
[RFC 8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC 8174,
May 2017, <https://www.rfc-editor.org/info/RFC 8174>.
Bjorklund, et al. Standards Track PAGE 7
RFC 8527 RESTCONF Extensions for the NMDA March 2019
[RFC 8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC 8341, March 2018,
<https://www.rfc-editor.org/info/RFC 8341>.
[RFC 8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC 8342, March 2018,
<https://www.rfc-editor.org/info/RFC 8342>.
[RFC 8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC 8446, August 2018,
<https://www.rfc-editor.org/info/RFC 8446>.
[RFC 8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
and R. Wilton, "YANG Library", RFC 8525,
DOI 10.17487/RFC 8525, March 2019,
<https://www.rfc-editor.org/info/RFC 8525>.
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
RFC TOTAL SIZE: 15757 bytes
PUBLICATION DATE: Thursday, March 7th, 2019
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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