RESTCONF Protocol
draft-bierman-netconf-restconf-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|
|---|---|---|---|
| Authors | Andy Bierman , Martin Björklund , Kent Watsen , Rex Fernando | ||
| Last updated | 2013-09-09 | ||
| Replaced by | RFC 8040 | ||
| RFC stream | (None) | ||
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| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
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| Send notices to | (None) |
draft-bierman-netconf-restconf-01
Network Working Group A. Bierman
Internet-Draft YumaWorks
Intended status: Standards Track M. Bjorklund
Expires: March 13, 2014 Tail-f Systems
K. Watsen
Juniper Networks
R. Fernando
Cisco
September 9, 2013
RESTCONF Protocol
draft-bierman-netconf-restconf-01
Abstract
This document describes a RESTful protocol that provides a
programmatic interface over HTTP for accessing data defined in YANG,
using the datastores defined in NETCONF.
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-
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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 March 13, 2014.
Copyright Notice
Copyright (c) 2013 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
(http://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
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Simple Subset of NETCONF Functionality . . . . . . . . . . 5
1.2. Data Model Driven API . . . . . . . . . . . . . . . . . . 6
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.1. NETCONF . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.2. HTTP . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.3. YANG . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.4. Terms . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4.1. Resource URI Map . . . . . . . . . . . . . . . . . . . 11
1.4.2. RESTCONF Message Examples . . . . . . . . . . . . . . 11
2. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.1. Message Model . . . . . . . . . . . . . . . . . . . . . . 18
2.2. Notification Model . . . . . . . . . . . . . . . . . . . . 18
2.3. Resource Model . . . . . . . . . . . . . . . . . . . . . . 18
2.3.1. RESTCONF Resource Types . . . . . . . . . . . . . . . 18
2.3.2. Resource Discovery . . . . . . . . . . . . . . . . . . 19
2.4. Datastore Model . . . . . . . . . . . . . . . . . . . . . 19
2.4.1. Content Model . . . . . . . . . . . . . . . . . . . . 20
2.4.2. Editing Model . . . . . . . . . . . . . . . . . . . . 20
2.4.3. Locking Model . . . . . . . . . . . . . . . . . . . . 22
2.4.4. Persistence Model . . . . . . . . . . . . . . . . . . 22
2.4.5. Defaults Model . . . . . . . . . . . . . . . . . . . . 22
2.5. Transaction Model . . . . . . . . . . . . . . . . . . . . 23
2.6. Extensibility Model . . . . . . . . . . . . . . . . . . . 23
2.7. Versioning Model . . . . . . . . . . . . . . . . . . . . . 23
2.8. Retrieval Filtering Model . . . . . . . . . . . . . . . . 24
2.9. Access Control Model . . . . . . . . . . . . . . . . . . . 24
3. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.1. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.4. POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.4.1. Create Resource Mode . . . . . . . . . . . . . . . . . 29
3.4.2. Invoke Operation Mode . . . . . . . . . . . . . . . . 30
3.5. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.6. PATCH . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.8. Query Parameters . . . . . . . . . . . . . . . . . . . . . 31
3.8.1. "config" Parameter . . . . . . . . . . . . . . . . . . 31
3.8.2. "depth" Parameter . . . . . . . . . . . . . . . . . . 32
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3.8.3. "format" Parameter . . . . . . . . . . . . . . . . . . 34
3.8.4. "insert" Parameter . . . . . . . . . . . . . . . . . . 35
3.8.5. "point" Parameter . . . . . . . . . . . . . . . . . . 36
3.8.6. "select" Parameter . . . . . . . . . . . . . . . . . . 37
3.9. Protocol Operations . . . . . . . . . . . . . . . . . . . 37
4. Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.1. Request URI Structure . . . . . . . . . . . . . . . . . . 38
4.2. Message Headers . . . . . . . . . . . . . . . . . . . . . 39
4.3. Message Encoding . . . . . . . . . . . . . . . . . . . . . 40
4.4. RESTCONF Meta-Data . . . . . . . . . . . . . . . . . . . . 40
4.4.1. JSON Encoding of RESTCONF Meta-Data . . . . . . . . . 41
4.5. Return Status . . . . . . . . . . . . . . . . . . . . . . 42
4.6. Message Caching . . . . . . . . . . . . . . . . . . . . . 42
5. Resources . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.1. API Resource (/restconf) . . . . . . . . . . . . . . . . . 44
5.1.1. /restconf/datastore . . . . . . . . . . . . . . . . . 45
5.1.2. /restconf/modules . . . . . . . . . . . . . . . . . . 45
5.1.3. /restconf/operations . . . . . . . . . . . . . . . . . 46
5.2. Datastore Resource . . . . . . . . . . . . . . . . . . . . 47
5.3. Data Resource . . . . . . . . . . . . . . . . . . . . . . 47
5.3.1. Encoding YANG Instance Identifiers in the Request
URI . . . . . . . . . . . . . . . . . . . . . . . . . 48
5.3.2. Data Resource Retrieval . . . . . . . . . . . . . . . 51
5.4. Operation Resource . . . . . . . . . . . . . . . . . . . . 52
5.4.1. Encoding Operation Input Parameters . . . . . . . . . 52
5.4.2. Encoding Operation Output Parameters . . . . . . . . . 53
5.5. Event Resource . . . . . . . . . . . . . . . . . . . . . . 54
6. Error Reporting . . . . . . . . . . . . . . . . . . . . . . . 55
6.1. Error Response Message . . . . . . . . . . . . . . . . . . 56
7. YANG Patch . . . . . . . . . . . . . . . . . . . . . . . . . . 58
7.1. Why not use JSON Patch? . . . . . . . . . . . . . . . . . 58
7.2. YANG Patch Target Data Node . . . . . . . . . . . . . . . 59
7.3. YANG Patch Edit Operations . . . . . . . . . . . . . . . . 59
7.4. YANG Patch Error Handling . . . . . . . . . . . . . . . . 59
7.5. YANG Patch Response . . . . . . . . . . . . . . . . . . . 60
7.6. YANG Patch Examples . . . . . . . . . . . . . . . . . . . 60
7.6.1. Continue-on-error Example . . . . . . . . . . . . . . 60
7.6.2. Move list entry example . . . . . . . . . . . . . . . 63
8. RESTCONF module . . . . . . . . . . . . . . . . . . . . . . . 65
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 78
9.1. YANG Module Registry . . . . . . . . . . . . . . . . . . . 78
10. Security Considerations . . . . . . . . . . . . . . . . . . . 79
11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 80
11.1. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . . 80
11.2. YANG-API-01 to RESTCONF-00 . . . . . . . . . . . . . . . . 80
12. Closed Issues . . . . . . . . . . . . . . . . . . . . . . . . 82
13. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 84
14. Example YANG Module . . . . . . . . . . . . . . . . . . . . . 86
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15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 91
15.1. Normative References . . . . . . . . . . . . . . . . . . . 91
15.2. Informative References . . . . . . . . . . . . . . . . . . 91
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 92
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1. Introduction
There is a need for standard mechanisms to allow WEB applications to
access the configuration data, operational data, data-model specific
protocol operations, and notification events within a networking
device, in a modular and extensible manner.
This document describes a RESTful protocol called RESTCONF, running
over HTTP [RFC2616], for accessing data defined in YANG [RFC6020],
using datastores defined in NETCONF [RFC6241].
The NETCONF protocol defines configuration datastores and a set of
Create, Retrieve, Update, Delete (CRUD) operations that can be used
to access these datastores. The YANG language defines the syntax and
semantics of datastore content, operational data, custom protocol
operations, and notification events. RESTful operations are used to
access the hierarchical data within a datastore.
A RESTful API can be created that provides CRUD operations on a
NETCONF datastore containing YANG-defined data. This can be done in
a simplified manner, compatible with HTTP and RESTful design
principles. Since NETCONF protocol operations are not relevant, the
user should not need any prior knowledge of NETCONF in order to use
the RESTful API.
Configuration data and state data are exposed as resources that can
be retrieved with the GET method. Resources representing
configuration data can be modified with the DELETE, PATCH, POST, and
PUT methods. Data-model specific protocol operations defined with
the YANG "rpc" statement can be invoked with the POST method. Data-
model specific notification events defined with the YANG
"notification" statement can be accessed (delivery method TBD).
1.1. Simple Subset of NETCONF Functionality
The framework and meta-model used for a RESTful API does not need to
mirror those used by the NETCONF protocol. It just needs to be
compatible with NETCONF. A simplified framework and protocol is
needed that utilizes the three NETCONF datastores (candidate,
running, startup), but hides the complexity of multiple datastores
from the client.
A simplified transaction model is needed that allows basic CRUD
operations on a hierarchy of conceptual resources. This represents a
limited subset of the transaction capabilities of the NETCONF
protocol.
Applications that require more complex transaction capabilities might
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consider NETCONF instead of RESTCONF. The following transaction
features are not directly provided in RESTCONF:
o datastore locking (full or partial)
o candidate datastore
o startup datastore
o validate operation
o confirmed-commit procedure
It is possible that a server could expose NETCONF operations as data-
model specific operation resources, but that is out of scope within
this document.
The RESTful API is not intended to replace NETCONF, but rather
provide an additional simplified interface that follows RESTful
principles and is compatible with a resource-oriented device
abstraction. It is expected that applications that need the full
feature set of NETCONF such as notifications will continue to use
NETCONF.
The following figure shows the system components:
+-----------+ +-----------------+
| WEB app | <-------> | |
+-----------+ HTTP | network device |
| |
+-----------+ | +-----------+ |
| NMS app | <-------> | | datastore | |
+-----------+ NETCONF | +-----------+ |
+-----------------+
1.2. Data Model Driven API
RESTCONF combines the simplicity of a RESTful API over HTTP with the
predictability and automation potential of a schema-driven API.
A RESTful client using HATEOAS principles would not use any data
modelling language to define the application-specific content of the
API. The client would discover each new child resource as it
traverses the URIs return as Location IDs to discover the server
capabilities.
This approach has 3 significant weaknesses wrt/ control of complex
networking devices:
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o inefficient performance: configuration APIs will be quite complex
and may require thousands of protocol messages to discover all the
schema information. Typically the data type information has to be
passed in the protocol messages, which is also wasteful overhead.
o no data model richness: without a data model, the schema-level
semantics and validation constraints are not available to the
application.
o no tool automation: API automation tools need some sort of content
schema to function. Such tools can automate various programming
and documentation tasks related to specific data models.
Data model modules such as YANG modules serve as an "API contract"
that will be honored by the server. An application designer can code
to the data model, knowing in advance important details about the
exact protocol operations and datastore content a conforming server
implementation will support.
RESTCONF provides the YANG module capability information supported by
the server, in case the client wants to use it. The URIs for custom
protocol operations and datastore content are predictable, based on
the YANG module definitions. Note that the YANG modules and
predictable URIs are optional to use by the client. They can be
completely ignored without any loss of protocol functionality.
Operational experience with CLI and SNMP indicates that operators
learn the 'location' of specific service or device related data and
do not expect such information to be arbitrary and discovered each
time the client opens a management session to a server.
1.3. Terminology
The keywords "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].
1.3.1. NETCONF
The following terms are defined in [RFC6241]:
o candidate configuration datastore
o client
o configuration data
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o datastore
o configuration datastore
o protocol operation
o running configuration datastore
o server
o startup configuration datastore
o state data
o user
1.3.2. HTTP
The following terms are defined in [RFC2616]:
o entity tag
o fragment
o header line
o message body
o method
o path
o query
o request URI
o response body
1.3.3. YANG
The following terms are defined in [RFC6020]:
o container
o data node
o key leaf
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o leaf
o leaf-list
o list
o presence container (or P-container)
o RPC operation (now called protocol operation)
o non-presence container (or NP-container)
o ordered-by system
o ordered-by user
1.3.4. Terms
The following terms are used within this document:
o API resource: a resource with the media type "application/
vnd.yang.api+xml" or "application/vnd.yang.api+json". API
resources can only be edited by the server.
o data resource: a resource with the media type "application/
vnd.yang.data+xml" or "application/vnd.yang.data+json". Data
resources can be edited by clients or the server. Only YANG
containers and lists can be data resources. Top-level YANG
terminals are treated as fields within the datastore resource.
o datastore resource: a resource with the media type "application/
vnd.yang.datastore+xml" or "application/vnd.yang.datastore+json".
Datastore resources can only be edited by the server.
o edit operation: a RESTCONF operation on a data resource using the
POST, PUT, PATCH, or DELETE method.
o event resource: a resource with the media type "application/
vnd.yang.event+xml" or "application/vnd.yang.event+json". It
represents a conceptual system or data-model specific event that
is delivered within a notification message.
o field: a YANG terminal node within a resource.
o operation: the conceptual RESTCONF operation for a message,
derived from the HTTP method, request URI, headers, and message
body.
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o operation resource: a resource with the media type "application/
vnd.yang.operation+xml" or "application/vnd.yang.operation+json".
o patch: a generic PATCH operation on the target datastore. The
media type of the message body content will identity the patch
type in use.
o plain patch: a PATCH operation where the media type is
"application/vnd.yang.data+xml" or "application/
vnd.yang.data+json".
o query parameter: a parameter (and its value if any), encoded
within the query portion of the request URI.
o resource: a conceptual object representing a manageable component
within a device. Refers to the resource itself of the resource
and all its fields.
o retrieval request: an operation using the GET or HEAD methods.
o target resource: the resource that is associated with a particular
message, identified by the "path" component of the request URI.
o unified datastore: A conceptual representation of the device
running configuration. The server will hide all NETCONF datastore
details for edit operations, such as the ":candidate" and
":startup" capabilities.
o YANG Patch: a PATCH operation where the media type is
"application/vnd.yang.patch+xml" or "application/
vnd.yang.patch+json".
o YANG terminal node: a YANG node representing a leaf, leaf-list, or
anyxml definition.
1.4. Overview
This document defines the RESTCONF protocol, a RESTful API for
accessing conceptual datastores containing data defined with YANG
language. RESTCONF provides an application framework and meta-model,
using HTTP methods.
The RESTCONF resources are accessed via a set of URIs defined in this
document. The set of YANG modules supported by the server will
determine the additional data model specific operations and top-level
data node resources available on the server.
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1.4.1. Resource URI Map
The URI hierarchy for the RESTCONF resources consists of an entry
point container, 3 top-level resources, and 1 field. Refer to
Section 5 for details on each URI.
/restconf
/datastore
/<top-level-data-nodes> (config=true or false)
/modules
/module
/name
/revision
/namespace
/feature
/deviation
/operations
/<custom protocol operations>
/version (field)
1.4.2. RESTCONF Message Examples
The examples within this document use the normative YANG module
defined in Section 8 and the non-normative example YANG module
defined in Section 14.
This section shows some typical RESTCONF message exchanges.
1.4.2.1. Retrieve the Top-level API Resource
By default, when a resource is retrieved, any nested resources are
also returned, using the default encoding, which is XML.
The client may start by retrieving the top-level API resource, using
the entry point URI "/restconf".
GET /restconf?format=json HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+json
The server might respond as follows:
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HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Content-Type: application/vnd.yang.api+json
{
"restconf": {
"datastore" : [ null ],
"modules": {
"module": [
{
"name" : "example-jukebox",
"revision" : "2013-09-04",
"namespace" : "example.com"
}
]
},
"operations" : {
"play" : [ null ]
},
"version": "1.0"
}
}
To request that the response content to be encoded in XML, the
"Accept" header can be used, as in this example request:
GET /restconf HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+xml
An alternate approach is provided using the "format" query parameter,
as in this example request:
GET /restconf?format=xml HTTP/1.1
Host: example.com
The server will return the same response either way, which might be
as follows :
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/vnd.yang.api+xml
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<restconf xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
<datastore />
<modules>
<module>
<name>example-jukebox</name>
<revision>2013-09-04</revision>
<namespace>example.com</namespace>
</module>
</modules>
<operations>
<play xmlns="http://example.com/ns/example-jukebox" />
</operations>
<version>1.0</version>
</restconf>
Refer to Section 3.3 for details on the GET method.
1.4.2.2. Create New Data Resources
To create a new "jukebox" resource, the client might send:
POST /restconf/datastore HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{ "example-jukebox:jukebox" : [null] }
If the resource is created, the server might respond:
HTTP/1.1 201 Created
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Location: http://example.com/restconf/datastore/
example-jukebox:jukebox
Last-Modified: Mon, 23 Apr 2012 17:01:00 GMT
ETag: b3a3e673be2
To create a new "artist" resource within the "library" resource, the
client might send the following request.
POST /restconf/datastore/example-jukebox:jukebox/library HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{ "artist" : {
"name" : "Foo Fighters"
}
}
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If the resource is created, the server might respond as follows.
Note that the "Location" header line is wrapped for display purposes
only:
HTTP/1.1 201 Created
Date: Mon, 23 Apr 2012 17:02:00 GMT
Server: example-server
Location: http://example.com/restconf/datastore/
example-jukebox:jukebox/library/artist/Foo%20Fighters
Last-Modified: Mon, 23 Apr 2012 17:02:00 GMT
ETag: b3830f23a4c
To create a new "album" resource for this artist within the "jukebox"
resource, the client might send the following request. Note that the
request URI header line is wrapped for display purposes only:
POST /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{
"album" : {
"name" : "Wasting Light",
"genre" : "example-jukebox:alternative",
"year" : 2012 // note this is the wrong date
}
}
If the resource is created, the server might respond as follows.
Note that the "Location" header line is wrapped for display purposes
only:
HTTP/1.1 201 Created
Date: Mon, 23 Apr 2012 17:03:00 GMT
Server: example-server
Location: http://example.com/restconf/datastore/
example-jukebox:jukebox/library/artist/Foo%20Fighters/
album/Wasting%20Light
Last-Modified: Mon, 23 Apr 2012 17:03:00 GMT
ETag: b8389233a4c
Refer to Section 3.4 for details on the POST method.
1.4.2.3. Replace an Existing Data Resource
Note: replacing a resource is a fairly drastic operation. The PATCH
method is often more appropriate.
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The album sub-resource is replaced here for example purposes only.
To replace the "album" resource contents, the client might send as
follows. Note that the request URI header line is wrapped for
display purposes only:
PUT /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
Host: example.com
If-Match: b3830f23a4c
Content-Type: application/vnd.yang.data+json
{
"album" : {
"name" : "Wasting Light",
"genre" : "example-jukebox:alternative",
"year" : 2011
}
}
If the resource is updated, the server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:04:00 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 17:04:00 GMT
ETag: b27480aeda4c
Refer to Section 3.5 for details on the PUT method.
1.4.2.4. Patch an Existing Data Resource
To replace just the "year" field in the "album" resource (instead of
replacing the entire resource), the client might send a plain patch
as follows. Note that the request URI header line is wrapped for
display purposes only:
PATCH /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
Host: example.com
If-Match: b8389233a4c
Content-Type: application/vnd.yang.data+json
{ "year" : 2011 }
If the field is updated, the server might respond:
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HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:49:30 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 17:49:30 GMT
ETag: b2788923da4c
The XML encoding for the same request might be:
PATCH /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
Host: example.com
If-Match: b8389233a4c
Content-Type: application/vnd.yang.data+xml
<year xmlns="http://example.com/ns/example-jukebox">2011</year>
Refer to Section 3.6 for details on the PATCH method.
1.4.2.5. Delete an Existing Data Resource
To delete a resource such as the "album" resource, the client might
send:
DELETE /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
Host: example.com
If the resource is deleted, the server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:49:40 GMT
Server: example-server
Refer to Section 3.7 for details on the DELETE method.
1.4.2.6. Delete an Optional Field Within a Data Resource
The DELETE method cannot be used to delete an optional field within a
resource. This can only be done using the PATCH method with the YANG
Patch media type.
Refer to Section 7 for details on the YANG Patch method.
1.4.2.7. Invoke a Data Model Specific Operation
To invoke a data-model specific operation via an operation resource,
the POST method is used. A client might send a "backup-datastore"
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request as follows:
POST /restconf/operations/example-ops:backup-datastore HTTP/1.1
Host: example.com
The server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:50:00 GMT
Server: example-server
Refer to Section 3.9 for details on using the POST method with
operation resources.
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2. Framework
The RESTCONF protocol defines a framework that can be used to
implement a common API for configuration management. This section
describes the components of the RESTCONF framework.
2.1. Message Model
The RESTCONF protocol uses HTTP entities for messages. A single HTTP
message corresponds to a single protocol method. Most messages can
perform a single task on a single resource, such as retrieving a
resource or editing a resource. The exception is the PATCH method
using the YANG Patch format. This allows multiple datastore edits
within a single message.
2.2. Notification Model
[TBD]
2.3. Resource Model
The RESTCONF protocol operates on a hierarchy of resources, starting
with the top-level API resource itself. Each resource represents a
manageable component within the device.
A resource can be considered a collection of conceptual data and the
set of allowed methods on that data. It can contain child nodes that
are nested resources or fields. The child resource types and methods
allowed on them are data-model specific.
A resource has its own media type identifier, represented by the
"Content-Type" header in the HTTP response message. A resource can
contain zero or more nested resources. A resource can be created and
deleted independently of its parent resource, as long as the parent
resource exists.
All RESTCONF resources are defined in this document except datastore
contents, protocol operations, and notification events. The syntax
and semantics for these resource types are defined with YANG
statements.
2.3.1. RESTCONF Resource Types
The RESTCONF protocol defines some application specific media types
to identify each of the available resource types. The following
table summarizes the purpose of each resource.
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+-----------+--------------------------------+
| Resource | Media Type |
+-----------+--------------------------------+
| API | application/vnd.yang.api |
| Datastore | application/vnd.yang.datastore |
| Data | application/vnd.yang.data |
| Event | application/vnd.yang.event |
| Operation | application/vnd.yang.operation |
| Patch | application/vnd.yang.patch |
+-----------+--------------------------------+
RESTCONF Media Types
These resources are described in Section 5.
2.3.2. Resource Discovery
A client SHOULD start by retrieving the top-level API resource, using
the entry point URI "/restconf".
The RESTCONF protocol does not include a resource discovery
mechanism. Instead, the definitions within the YANG modules
advertised by the server are used to construct a predictable
operation or data resource identifier.
The "depth" query parameter can be used to control how many
descendant levels should be included when retrieving sub-resources.
This parameter can be used with the GET method to discover sub-
resources within a particular resource.
Refer to Section 3.8.2 for more details on the "depth" parameter.
2.4. Datastore Model
A conceptual "unified datastore" is used to simplify resource
management for the client. The RESTCONF datastore is a combination
of the running configuration and any non-configuration data supported
by the device. By default only configuration data is returned by a
GET method on the datastore contents.
The underlying NETCONF datastores can be used to implement the
unified datastore, but the server design is not limited to the exact
datastore procedures defined in NETCONF.
The "candidate" and "startup" datastores are not visible in the
RESTCONF protocol. Transaction management and configuration
persistence are handled by the server and not controlled by the
client.
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2.4.1. Content Model
The RESTCONF protocol operates on a conceptual datastore defined with
the YANG data modeling language. The server lists each YANG module
it supports in the "/restconf/modules/module" resource in the top-
level API resource type, using a structure based on the YANG module
capability URI format defined in RFC 6020.
The conceptual datastore contents, data-model-specific operations and
notification events are identified by this set of YANG module
resources. All RESTCONF content identified as either a data
resource, operation resource, or event resource is defined with the
YANG language.
The classification of data as configuration or non-configuration is
derived from the YANG "config" statement. Data retrieval with the
GET method can be filtered in several ways, including the "config"
parameter to retrieve configuration or non-configuration data.
Data ordering behavior is derived from the YANG "ordered-by"
statement. The YANG Patch operation is provided to allow list or
leaf-list fields to be inserted or moved in the same manner as
NETCONF.
The server is not required to maintain system ordered data in any
particular persistent order. The server SHOULD maintain the same
data ordering for system ordered data until the next reboot or
termination of the server. The server MUST maintain the same data
ordering for user ordered data until the next reboot or termination
of the server.
2.4.2. Editing Model
The RESTCONF datastore editing model is simple and direct, similar to
the behavior of the ":writable-running" capability in NETCONF.
Each RESTCONF edit of a datastore resource is activated upon
successful completion of the transaction. It is an implementation-
specific matter how the server accomplishes a RESTCONF edit request.
For example, a server which only accepts edits through a candidate
datastore may internally edit this datastore and perform the "commit"
operation automatically.
Applications which need more control over the editing model might
consider using NETCONF instead of RESTCONF.
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2.4.2.1. Edit Operation Discovery
Sometimes a server does not implement every operation for every
resource. Sometimes data model requirements cause a node to
implement a subset of the edit operations. For example, a server may
not allow modification of a particular configuration data node after
the parent resource has been created.
The OPTIONS method can be used to identify which HTTP methods are
supported by the server for a particular resource. For example, if
the server will allow a data resource node to be created then the
POST method will be returned in the response.
2.4.2.2. Edit Collision Detection
Two "edit collision detection" mechanisms are provided in RESTCONF,
for datastore and data resources.
o timestamp: the last change time is maintained and the
"Last-Modified" and "Date" headers are returned in the response
for a retrieval request. The "If-Unmodified-Since" header can be
used in edit operation requests to cause the server to reject the
request if the resource has been modified since the specified
timestamp.
o entity tag: a unique opaque string is maintained and the "ETag"
header is returned in the response for a retrieval request. The
"If-Match" header can be used in edit operation requests to cause
the server to reject the request if the resource entity tag does
not match the specified value.
Note that the server is only required to maintain these properties
for a datastore resource, not for individual data resources.
Example:
In this example, the server just supports the mandatory datastore
last-changed timestamp. The client has previously retrieved the
"Last-Modified" header and has some value cached to provide in the
following request to replace a list entry with key value "11":
PATCH /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album/Wasting%20Light/year HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+json
If-Unmodified-Since: Mon, 23 Apr 2012 17:01:00 GMT
Content-Type: application/vnd.yang.data+json
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{ "year" : "2011" }
In this example the datastore resource has changed since the time
specified in the "If-Unmodified-Since" header. The server might
respond:
HTTP/1.1 304 Not Modified
Date: Mon, 23 Apr 2012 19:01:00 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 17:45:00 GMT
ETag: b34aed893a4c
2.4.3. Locking Model
Datastore locking is not provided by RESTCONF. An application that
needs to make several changes to the running configuration datastore
contents in sequence, without disturbance from other clients might
consider using the NETCONF protocol instead of RESTCONF.
2.4.4. Persistence Model
Each RESTCONF edit of a datastore resource is saved to non-volatile
storage in an implementation-specific matter by the server. There is
no guarantee that configuration changes are saved immediately, or
that the saved configuration is always a mirror of the running
configuration.
Applications which need more control over the persistence model might
consider using NETCONF instead of RESTCONF.
2.4.5. Defaults Model
NETCONF has a rather complex defaults handling model for leafs.
RESTCONF attempts to avoid this complexity by restricting the
operations that can be applied to a resource.
If the target of a GET method (plus "select" value) is a data node
that represents a leaf that has a default value, and the leaf has not
been given a value yet, the server MUST return the default value that
is in use by the server.
The GET method returns only descendant nodes that exist, which will
be determined by the server. There is no mechanism for the client to
ask the server for the default values of nested resources that would
be used for any nodes not present, but some default value is in use
by the server. (There is no retrieval mode like
"with-defaults=report-all" in NETCONF.)
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Applications which need more control over the defaults model might
consider using NETCONF instead of RESTCONF.
2.5. Transaction Model
The RESTCONF protocol provides an extensible transaction framework
that allows a simplified transaction model that uses plain REST
operations to edit one resource (and sub-resources) at a time. It
also provides YANG Patch, which is a standard variant of the PATCH
method. This allows a richer set of edit operations that can be
applied to multiple resources at once.
RESTCONF does not provide a more complex transaction model that
allows for multiple edits to be stored in a temporary scratchpad and
committed all at once.
Applications which need more control over the transaction model might
consider using NETCONF instead of RESTCONF.
2.6. Extensibility Model
The RESTCONF protocol is designed to be extensible for datastore
content and data-model specific protocol operations. New protocol
operations can be added without changing the entry point if they are
optional and do not alter any existing operations.
Separate namespaces for each YANG module are used. Content encoded
in XML will indicate the module using the "namespace" URI value in
the YANG module. Content encoded in JSON will indicate the module
using the module name specified in the YANG module, but this is not
required unless multiple sibling nodes have the same YANG identifier
name. JSON encoding rules for module names are specified in
[I-D.lhotka-netmod-json].
2.7. Versioning Model
The version of a resource instance is identified with an entity tag,
as defined by HTTP. The version identifiers in this section apply to
the version of the schema definition of a resource. There are two
types of schema versioning information used in the RESTCONF protocol:
o the RESTCONF protocol version
o data and operation resource definition versions
The protocol version is identified by the string used for the well-
known URI entry point "/restconf". This would be changed (e.g.,
"/restconf2") if non-backward compatible changes are ever needed.
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Minor version changes that do not break backward-compatibility will
not cause the entry point to change.
The API "restconf/version" resource can be used by the client to
identify the exact version of the RESTCONF protocol implemented by
the server. This value will include the complete RESTCONF protocol
version. The "/restconf/version" resource MUST be updated every time
the protocol specification is republished.
The resource definition version for a data or operation resource is a
date string, which is the revision date of the YANG module that
defines the resource. The resource version for all other resource
types is a numeric string, defined by the "/restconf/version" field.
2.8. Retrieval Filtering Model
There are three types of filtering for retrieval of data resources in
the RESTCONF protocol.
o conditional all-or-nothing: use some conditional test mechanism in
the request headers and retrieve either a complete "200 OK"
response if the condition is met, or a "304 Not Modified" Status-
Line if the condition is not met.
o data classification: request configuration or non-configuration
data.
o filter: request a subset of all possible descendant nodes within
the target resource. The "select" query parameter can be used for
this purpose.
Refer to Section 5.3.2 for details on data retrieval filtering.
2.9. Access Control Model
The RESTCONF protocol provides no granular access control for any
content except for operation and data resources. The NETCONF Access
Control Model (NACM) is defined in [RFC6536]. There is a specific
mapping between RESTCONF operations and NETCONF edit operations,
defined in Table 1. The resource path also needs to be converted
internally by the server to the corresponding YANG instance-
identifier. Using this information, the server can apply the NACM
access control rules to RESTCONF messages.
The server MUST NOT allow any operation to any resources that the
client is not authorized to access.
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3. Operations
The RESTCONF protocol uses HTTP methods to identify the CRUD
operation requested for a particular resource. The following table
shows how the RESTCONF operations relate to NETCONF protocol
operations:
+----------+-------------------------------------+
| RESTCONF | NETCONF |
+----------+-------------------------------------+
| OPTIONS | none |
| HEAD | none |
| GET | <get-config>, <get> |
| POST | <edit-config> (operation="create") |
| PUT | <edit-config> (operation="replace") |
| PATCH | <edit-config> (operation="merge") |
| DELETE | <edit-config> (operation="delete") |
+----------+-------------------------------------+
Table 1: CRUD Methods in RESTCONF
The NETCONF "remove" operation attribute is not supported by the HTTP
DELETE method. The resource must exist or the DELETE method will
fail.
This section defines the RESTCONF protocol usage for each HTTP
method.
3.1. OPTIONS
The OPTIONS method is sent by the client to discover which methods
are supported by the server for a specific resource. It is supported
for all media types. Note that implementation of this method is part
of HTTP, and this section does not introduce any additional
requirements.
The request MUST contain a request URI that contains at least the
entry point component.
The server will return a "Status-Line" header containing "204 No
Content". and include the "Allow" header in the response. This
header will be filled in, based on the target resource media type.
Other headers MAY also be included in the response.
Example 1:
A client might request the methods supported for a data resource
called "library":
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OPTIONS /restconf/datastore/example-jukebox:jukebox/
library/artist HTTP/1.1
Host: example.com
The server might respond (for a config=true list):
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Allow: OPTIONS,HEAD,GET,POST,PUT,PATCH,DELETE
Example 2:
A client might request the methods supported for a non-configuration
"counters" resource within a "system" resource:
OPTIONS /restconf/datastore/example-system:system/
counters HTTP/1.1
Host: example.com
The server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:02:00 GMT
Server: example-server
Allow: OPTIONS,HEAD,GET
Example 3:
A client might request the methods supported for an operation
resource called "play":
OPTIONS /restconf/operations/example-jukebox:play HTTP/1.1
Host: example.com
The server might respond:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 17:02:00 GMT
Server: example-server
Allow: POST
3.2. HEAD
The HEAD method is sent by the client to retrieve just the headers
that would be returned for the comparable GET method, without the
response body. It is supported for all resource types, except
operation resources.
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The request MUST contain a request URI that contains at least the
entry point component.
The same query parameters supported by the GET method are supported
by the HEAD method. For example, the "select" query parameter can be
used to specify a nested resource within the target resource.
The access control behavior is enforced as if the method was GET
instead of HEAD. The server MUST respond the same as if the method
was GET instead of HEAD, except that no response body is included.
Example:
The client might request the response headers for JSON representation
of the "library" resource:
HEAD /restconf/datastore/example-jukebox:jukebox/
library HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+json
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:02:40 GMT
Server: example-server
Content-Type: application/vnd.yang.data+json
Cache-Control: no-cache
Pragma: no-cache
ETag: a74eefc993a2b
Last-Modified: Mon, 23 Apr 2012 11:02:14 GMT
3.3. GET
The GET method is sent by the client to retrieve data and meta-data
for a resource. It is supported for all resource types, except
operation resources. The request MUST contain a request URI that
contains at least the entry point component.
The following query parameters are supported by the GET method:
+--------+---------+------------------------------------------------+
| Name | Section | Description |
+--------+---------+------------------------------------------------+
| config | 3.8.1 | Request either configuration or |
| | | non-configuration data |
| depth | 3.8.2 | Control the depth of a retrieval request |
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| format | 3.8.3 | Request either JSON or XML content in the |
| | | response |
| select | 3.8.6 | Specify a nested resource within the target |
| | | resource |
+--------+---------+------------------------------------------------+
GET Query Parameters
The server MUST NOT return any data resources for which the user does
not have read privileges.
If the user is not authorized to read any portion of the target
resource, an error response containing a "403 Forbidden" Status-Line
is returned to the client.
If the user is authorized to read some but not all of the target
resource, the unauthorized content is omitted from the response
message body, and the authorized content is returned to the client.
Example:
The client might request the response headers for a JSON
representation of the "library" resource:
GET /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album?format=json HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+json
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:02:40 GMT
Server: example-server
Content-Type: application/vnd.yang.data+json
Cache-Control: no-cache
Pragma: no-cache
ETag: a74eefc993a2b
Last-Modified: Mon, 23 Apr 2012 11:02:14 GMT
{
"album" : {
"name" : "Wasting Light",
"genre" : "example-jukebox:alternative",
"year" : 2011
}
}
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3.4. POST
The POST method is sent by the client for various reasons. The
server uses the target resource media type to determine how to
process the request.
The request MUST contain a request URI that contains a target
resource which identifies one of the following resource types:
+-----------+------------------------------------------------+
| Type | Description |
+-----------+------------------------------------------------+
| Datastore | Create a top-level configuration data resource |
| Data | Create a configuration data sub-resource |
| Operation | Invoke protocol operation |
+-----------+------------------------------------------------+
Resource Types that Support POST
3.4.1. Create Resource Mode
If the target resource type is a Datastore or Data resource, then the
POST is treated as a request to create a resource or sub-resource.
The following query parameters are supported by the POST method for
Datastore and Data resource types. They can only be used for YANG
list data nodes which are ordered by the user.
+--------+---------+-----------------------------------------+
| Name | Section | Description |
+--------+---------+-----------------------------------------+
| insert | 3.8.4 | Specify where to insert a resource |
| point | 3.8.5 | Specify the insert point for a resource |
+--------+---------+-----------------------------------------+
POST Query Parameters
If the POST method succeeds, a "204 No Content" Status-Line is
returned and there is no response message body.
If the user is not authorized to create the target resource, an error
response containing a "403 Forbidden" Status-Line is returned to the
client. All other error responses are handled according to the
procedures defined in Section 6.
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3.4.2. Invoke Operation Mode
If the target resource type is an Operation resource, then the POST
method is treated as a request to invoke that operation. The message
body (if any) is processed as the operation input parameters. Refer
to Section 5.4 for details on Operation resources.
If the POST method succeeds, a "200 OK" Status-Line is returned if
there is a response message body, and a "204 No Content" Status-Line
is returned if there is no response message body.
If the user is not authorized to invoke the target operation, an
error response containing a "403 Forbidden" Status-Line is returned
to the client. All other error responses are handled according to
the procedures defined in Section 6.
3.5. PUT
The PUT method is sent by the client to replace the target resource.
The request MUST contain a request URI that contains a target
resource that identifies the data resource to replace.
If the PUT method succeeds, a "200 OK" Status-Line is returned, and
there is no response message body.
If the user is not authorized to replace the target resource an error
response containing a "403 Forbidden" Status-Line is returned to the
client. All other error responses are handled according to the
procedures defined in Section 6.
3.6. PATCH
The PATCH method uses the HTTP PATCH method defined in [RFC5789] to
provide an extensible framework for resource patching mechanisms.
Each patch type needs a unique media type. Any number of patch types
can be supported by the server. There are two mandatory patch types
that MUST be implemented by the server:
o plain patch type: If the specified media type is "application/
vnd.yang.data", then the PATCH method is a simple merge operation
on the target resource. The message body contains the XML or JSON
encoded resource content that will be merged with the target
resource.
o YANG Patch type: If the specified media type is "application/
vnd.yang.patch", then the PATCH method is a YANG Patch formatted
list of edits (see Section 7). The message body contains the XML
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or JSON encoded instance of the 'patch' container specified in the
'ietf-restconf' YANG module (see Section 8).
The PATCH method MUST be used to create or delete an optional field
within an existing resource or sub-resource.
If the PATCH method succeeds, a "200 OK" Status-Line is returned, and
there is no response message body.
If the user is not authorized to alter the target resource an error
response containing a "403 Forbidden" Status-Line is returned to the
client. All other error responses are handled according to the
procedures defined in Section 6.
3.7. DELETE
The DELETE method is used to delete the target resource.
If the DELETE method succeeds, a "200 OK" Status-Line is returned,
and there is no response message body.
If the user is not authorized to delete the target resource then an
error response containing a "403 Forbidden" Status-Line is returned
to the client. All other error responses are handled according to
the procedures defined in Section 6.
3.8. Query Parameters
Each RESTCONF operation allows zero or more query parameters to be
present in the request URI. Refer to Section 3 for details on the
query parameters used in the definition of each operation.
Query parameters can be given in any order. Each parameter can
appear zero or one time. A default value may apply if the parameter
is missing.
This section defines all the RESTCONF query parameters.
3.8.1. "config" Parameter
The "config" parameter is used to specify whether configuration or
non-configuration data is requested.
This parameter is only supported for the GET and HEAD methods. It is
also only supported if the target resource is a data resource.
syntax: config= true | false
default: true
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Example:
This example request by the client would retrieve only the non-
configuration data nodes that exist within the "library" resource.
GET /restconf/datastore/example-jukebox:jukebox/
library?config=false HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+json
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:30 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/vnd.yang.data+json
{
"library" : {
"artist-count" : 42,
"album-count" : 59,
"song-count" : 374
}
}
3.8.2. "depth" Parameter
The "depth" parameter is used to specify the number of nest levels
returned in a response for a GET method. A nest-level consists of
the target resource and any child nodes which are contained within
the target resource node.
The start level is determined by the target resource for the
operation.
syntax: depth=<range: 1..max> | unbounded
default: unbounded
Example:
This example operation would retrieve 2 levels of configuration data
nodes that exist within the top-level "jukebox" resource.
GET /restconf/datastore/example-jukebox:jukebox
?depth=2 HTTP/1.1
Host: example.com
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Accept: application/vnd.yang.data+json
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:11:30 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/vnd.yang.data+json
{
"jukebox" : {
"library" : {
"artist" : {
"name" : "Foo Fighters"
}
},
"player" : {
"gap" : 0.5
}
}
}
By default, the server will include all sub-trees within a retrieved
resource, which is the same resource type. Only only level of sub-
resources with a different media type than the target resource will
be returned.
For example, if the client retrieves the "application/vnd.yang.api"
resource type, then the node for the datastore resource is returned
as an empty node, because all its child nodes are data resources.
The entire contents of the datastore are not returned in this case.
The operation resources also are returned as empty nodes (e.g. "play"
operation).
Request URL:
GET /restconf HTTP/1.1
Response:
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{
"restconf": {
"datastore" : [ null ],
"modules": {
"module": [
{
"name" : "example-jukebox",
"revision" : "2013-09-04",
"namespace" : "example.com"
}
]
},
"operations" : {
"play" : [ null ]
},
"version": "1.0"
}
}
3.8.3. "format" Parameter
The "format" parameter is used to specify the format of any content
returned in the response. Note that this parameter MAY be used
instead of the "Accept" header to identify the format desired in the
response.
The "format" parameter is only supported for the GET and HEAD
methods. It is supported for all RESTCONF media types.
syntax: format= xml | json
default: Accept header, then xml
If the "format" parameter is present, then it overrides the Accept
header, if present. If neither the Accept header or the "format"
parameter are present, then the default is XML.
Examples:
GET /restconf/datastore/example-routing:routing HTTP/1.1
Host: example.com
Accept: application/vnd.yang.data+json
This example request would retrieve only the configuration data nodes
that exist within the top-level "routing" resource, and retrieve them
in JSON encoding.
GET /restconf/datastore/example-routing:routing
?format=json HTTP/1.1
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Host: example.com
This example request would retrieve only the configuration data nodes
that exist within the top-level "routing" resource, and retrieve them
in JSON encoding.
3.8.4. "insert" Parameter
The "insert" parameter is used to specify how a resource should be
inserted within a user-ordered list.
This parameter is only supported for the POST method. It is also
only supported if the target resource is a data resource, and that
data represents a YANG list that is ordered by the user, not the
system.
If the values "before" or "after" are used, then a "point" parameter
for the insertion parameter MUST also be present.
syntax: insert= first | last | before | after
default: last
Example:
Request from client:
PATCH /restconf/datastore/example-jukebox:jukebox/
playlist/Foo-One?insert=first HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{
"song" : {
"index" : 1,
"id" : "/example-jukebox:jukebox/library/artist/
Foo%20Fighters/album/Wasting%20Light/song/Rope"
}
}
Response from server:
HTTP/1.1 201 Created
Date: Mon, 23 Apr 2012 13:01:20 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
Location: http://example.com/restconf/datastore/
example-jukebox:jukebox/playlist/Foo-One/song/1
ETag: eeeada438af
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3.8.5. "point" Parameter
The "point" parameter is used to specify the insertion point for a
data resource that is being created or moved within a user ordered
list. It is ignored unless the "insert" query parameter is also
present, and has the value "before" or "after".
This parameter contains the instance identifier of the resource to be
used as the insertion point for a POST method. It is encoded
according to the rules defined in Section 5.3.1. There is no default
for this parameter.
syntax: point= <instance-identifier of insertion point node>
Example:
In this example, the client is inserting a new "song" resource within
an "album" resource after another song. The request URI is split for
display purposes only.
Request from client:
POST /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album/Wasting%20Light?insert=after
&point=/restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album/Wasting%20Light/song/
Bridge%20Burning HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{
"song" : {
"name" : "Rope",
"location" : "/media/rope.mp3",
"format" : "MP3",
"length" : 259
}
}
Response from server:
HTTP/1.1 204 No Content
Date: Mon, 23 Apr 2012 13:01:20 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
ETag: abcada438af
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3.8.6. "select" Parameter
The "select" query parameter is used to specify an expression which
can represent a subset of all data nodes within the target resource.
It contains a relative path expression, using the target resource as
the context node.
It is supported for all resource types except operation resources.
The contents are encoded according to the "api-select" rule defined
in Section 5.3.1. This parameter is only allowed for GET and HEAD
methods.
[FIXME: the syntax of the select string is still TBD; XPath, schema-
identifier, regular expressions, something else; Perhaps add
parameter "xselect" for XPath and this param is limited to a path-
expr.]
In this example the client is retrieving the API version field from
the server in JSON format:
GET /restconf?select=version&format=json HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+json
The server might respond as follows.
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Last-Modified: Sun, 22 Apr 2012 01:00:14 GMT
Content-Type: application/vnd.yang.api+json
{ "version": "1.0" }
3.9. Protocol Operations
The RESTCONF protocol allows data-model specific protocol operations
to be invoked using the POST method. The media type "application/
vnd.yang.operation+xml" or "application/vnd.yang.operation+json" MUST
be used in the "Content-Type" line in the message header.
Data model specific operations are supported. The syntax and
semantics of these operations exactly correspond to the YANG "rpc"
statement definition for the operation.
Refer to Section 5.4 for details on operation resources.
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4. Messages
This section describes the messages that are used in the RESTCONF
protocol.
4.1. Request URI Structure
Resources are represented with URIs following the structure for
generic URIs in [RFC3986].
A RESTCONF operation is derived from the HTTP method and the request
URI, using the following conceptual fields:
<OP> /restconf/<path>?<query>#<fragment>
^ ^ ^ ^ ^
| | | | |
method entry resource query fragment
M M O O I
M=mandatory, O=optional, I=ignored
<text> replaced by client with real values
o method: the HTTP method identifying the RESTCONF operation
requested by the client, to act upon the target resource specified
in the request URI. RESTCONF operation details are described in
Section 3.
o entry: the well-known RESTCONF entry point ("/restconf").
o resource: the path expression identifying the resource that is
being accessed by the operation. If this field is not present,
then the target resource is the API itself, represented by the
media type "application/vnd.yang.api".
o query: the set of parameters associated with the RESTCONF message.
These have the familiar form of "name=value" pairs. There is a
specific set of parameters defined, although the server MAY choose
to support additional parameters not defined in this document.
o fragment: This field is not used by the RESTCONF protocol.
The client SHOULD NOT assume the final structure of a URI path for a
resource. Instead, existing resources can be discovered with the GET
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method. When new resources are created by the client, a "Location"
header is returned, which identifies the path of the newly created
resource. The client MUST use this exact path identifier to access
the resource once it has been created.
The "target" of an operation is a resource. The "path" field in the
request URI represents the target resource for the operation.
4.2. Message Headers
There are several HTTP header lines utilized in RESTCONF messages.
Messages are not limited to the HTTP headers listed in this section.
HTTP defines which header lines are required for particular
circumstances. Refer to each operation definition section in
Section 3 for examples on how particular headers are used.
There are some request headers that are used within RESTCONF, usually
applied to data resources. The following tables summarize the
headers most relevant in RESTCONF message requests:
+---------------------+---------------------------------------------+
| Name | Description |
+---------------------+---------------------------------------------+
| Accept | Response Content-Types that are acceptable |
| Content-Type | The media type of the request body |
| Host | The host address of the server |
| If-Match | Only perform the action if the entity |
| | matches ETag |
| If-Modified-Since | Only perform the action if modified since |
| | time |
| If-Unmodified-Since | Only perform the action if un-modified |
| | since time |
+---------------------+---------------------------------------------+
RESTCONF Request Headers
The following tables summarize the headers most relevant in RESTCONF
message responses:
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+---------------+---------------------------------------------------+
| Name | Description |
+---------------+---------------------------------------------------+
| Allow | Valid actions when 405 error returned |
| Content-Type | The media type of the response body |
| Date | The date and time the message was sent |
| ETag | An identifier for a specific version of a |
| | resource |
| Last-Modified | The last modified date and time of a resource |
| Location | The resource identifier for a newly created |
| | resource |
+---------------+---------------------------------------------------+
RESTCONF Response Headers
4.3. Message Encoding
RESTCONF messages are encoded in HTTP according to RFC 2616. The
"utf-8" character set is used for all messages. RESTCONF message
content is sent in the HTTP message body.
Content is encoded in either JSON or XML format.
XML encoding rules for data nodes are defined in [RFC6020]. The same
encoding rules are used for all XML content.
JSON encoding rules are defined in [I-D.lhotka-netmod-json]. Plain
JSON cannot be used because special encoding rules are needed to
handle multiple module namespaces and provide consistent data type
processing.
Request input content encoding format is identified with the Content-
Type header. This field MUST be present if a message body is sent by
the client.
Response output content encoding format is identified with the Accept
header, the "format" query parameter, or if neither is specified, the
request input encoding format is used. If there was no request
input, then the default output encoding is XML. File extensions
encoded in the request are not used to identify format encoding.
4.4. RESTCONF Meta-Data
The RESTCONF protocol needs to retrieve the same meta-data that is
used in the NETCONF protocol. Information about default leafs, last-
modified timestamps, etc. are commonly used to annotate
representations of the datastore contents. This meta-data is not
defined in the YANG schema because it applies to the datastore, and
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is common across all data nodes.
This information is encoded as attributes in XML, but JSON does not
have a standard way of attaching non-schema defined meta-data to a
resource or field.
4.4.1. JSON Encoding of RESTCONF Meta-Data
The YANG to JSON mapping [I-D.lhotka-netmod-json] does not support
attributes because YANG does not support meta-data in data node
definitions. This section specifies how RESTCONF meta-data is
encoded in JSON.
Only simple meta-data is supported:
o A meta-data instance can appear 0 or 1 times for a particular data
node
o A meta-data instance associated with a resource is encoded as if
it were a YANG leaf of type "string", according to the encoding
rules in [I-D.lhotka-netmod-json], except the identifier is
prepended with a "@" (%40) character.
o A meta-data instance associated with a field within a resource is
encoded as if it were a container for the meta-data values and the
field value in its native encoding. It is encoded according to
the rules in [I-D.lhotka-netmod-json], except the meta-data
identifiers are prepended with a "@" (%40) character. The field
name/value pair is repeated inside this container, which contains
the actual value of the field.
Examples:
Meta-data:
enabled=<boolean>
owner=<owner-name>
YANG example:
container top {
leaf A {
type int32;
}
leaf B {
type boolean;
}
}
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The client is retrieving the "top" data resource, and the server is
including datastore meta-data. Note that a query parameter to
request or suppress specific meta-data is not provided in RESTCONF.
GET /restconf/datastore/example:top HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+json
The server might respond as follows:
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Content-Type: application/vnd.yang.api+json
{
"top": {
"@enabled" : "true",
"@owner" : "fred",
"A" : {
"@enabled" : "true",
"A" : 42
},
"B" : {
"@enabled" : "false",
"B" : true
}
}
}
4.5. Return Status
Each message represents some sort of resource access. An HTTP
"Status-Line" header line is returned for each request. If a 4xx or
5xx range status code is returned in the Status-Line, then the error
information will be returned in the response, according to the format
defined in Section 6.1.
4.6. Message Caching
Since the datastore contents change at unpredictable times, responses
from a RESTCONF server generally SHOULD NOT be cached.
The server SHOULD include a "Cache-Control" header in every response
that specifies whether the response should be cached. A "Pragma"
header specifying "no-cache" MAY also be sent in case the
"Cache-Control" header is not supported.
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Instead of using HTTP caching, the client SHOULD track the "ETag"
and/or "Last-Modified" headers returned by the server for the
datastore resource (or data resource if the server supports it). A
retrieval request for a resource can include headers such as
"If-None-Match" or "If-Modified-Since" which will cause the server to
return a "304 Not Modified" Status-Line if the resource has not
changed. The client MAY use the HEAD method to retrieve just the
message headers, which SHOULD include the "ETag" and "Last-Modified"
headers, if this meta-data is maintained for the target resource.
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5. Resources
The resources used in the RESTCONF protocol are identified by the
"path" component in the request URI. Each operation is performed on
a target resource.
5.1. API Resource (/restconf)
The API resource contains the state and access points for the
RESTCONF features. It is the top-level resource and has the media
type "application/vnd.yang.api+xml" or "application/
vnd.yang.api+json". It is accessible through the well-known relative
URI "/restconf".
The "restconf" container definition in the "ietf-restconf" module
defined in Section 8 is used to specify the structure and syntax of
the conceptual fields and sub-resources within the API resource.
The "restconf" entry point container, and all fields and sub-
resources with the same resource type, are defined in the namespace
of the "ietf-restconf" module.
There is one mandatory field "version" that identifies the specific
version of the RESTCONF protocol implemented by the server:
o The same server-wide response MUST be returned each time this
field is retrieved.
o It is assigned by the server when the server is started.
o The server MUST return the value "1.0" for this version of the
RESTCONF protocol.
o This field is encoded with the rules for an "enumeration" data
type, using the "version" leaf definition in Section 8.
This resource has the following child resources:
+----------------+--------------------------------+
| Child Resource | Description |
+----------------+--------------------------------+
| datastore | Link to "datastore" resource |
| modules | YANG module capability URIs |
| operations | Data-model specific operations |
+----------------+--------------------------------+
RESTCONF Resources
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5.1.1. /restconf/datastore
This mandatory resource represents the running configuration
datastore and any non-configuration data available. It may be
retrieved and edited directly. It cannot be created or deleted by
the client. This resource type is defined in Section 5.2.
5.1.2. /restconf/modules
This mandatory resource contains the identifiers for the YANG data
model modules supported by the server.
The server MUST maintain a last-modified timestamp for this resource,
and return the "Last-Modified" header when this resource is retrieved
with the GET or HEAD methods.
The server SHOULD maintain an entity-tag for this resource, and
return the "ETag" header when this resource is retrieved with the GET
or HEAD methods.
5.1.2.1. /restconf/modules/module
This mandatory resource contains one URI string for each YANG data
model module supported by the server. There MUST be an instance of
this resource for every YANG module that is accessible via an
operation resource or a data resource.
The contents of the "module" resource are defined in the "module"
YANG list statement in Section 8.
The server MAY maintain a last-modified timestamp for each instance
of this resource, and return the "Last-Modified" header when this
resource is retrieved with the GET or HEAD methods. If not supported
then the timestamp for the parent "modules" resource MAY be used
instead.
The server MAY maintain an entity-tag for each instance of this
resource, and return the "ETag" header when this resource is
retrieved with the GET or HEAD methods. If not supported then the
timestamp for the parent "modules" resource MAY be used instead.
There are additional encoding requirements for this resource. The
URI MUST follow the YANG module capability URI formatting defined in
section 5.6.4 of [RFC6020].
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5.1.2.2. Retrieval Example
In this example the client is retrieving the modules resource from
the server in JSON format:
GET /restconf/modules&format=json HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+json
The server might respond as follows.
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Last-Modified: Sun, 22 Apr 2012 01:00:14 GMT
Content-Type: application/vnd.yang.api+json
{
"modules": {
"module": [
{
"name" : "foo",
"revision" : "2012-01-02",
"namespace" : "http://example.com/ns/foo",
"feature" : [ "feature1", "feature2" ]
},
{
"name" : "foo-types",
"revision" : "2012-01-05",
"namespace" : "http://example.com/ns/foo-types"
},
{
"name" : "bar",
"revision" : "2012-11-05",
"namespace" : "http://example.com/ns/bar",
"feature" : [ "bar-ext" ]
}
]
}
}
5.1.3. /restconf/operations
This optional resource provides access to the data-model specific
protocol operations supported by the server. The server MAY omit
this resource if no data-model specific operations are advertised.
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Any data-model specific operations defined in the YANG modules
advertised by the server MAY be available as child nodes of this
resource.
5.2. Datastore Resource
A datastore resource represents the conceptual root of a tree of data
resources.
The server MUST maintain a last-modified timestamp for this resource,
and return the "Last-Modified" header when this resource is retrieved
with the GET or HEAD methods. Only changes to configuration data
resources within the datastore affect this timestamp.
The server SHOULD maintain a resource entity tag for this resource,
and return the "ETag" header when this resource is retrieved with the
GET or HEAD methods. The resource entity tag SHOULD be changed to a
new previously unused value if changes to any configuration data
resources within the datastore are made.
A datastore resource can be retrieved with the GET method, to
retrieve either configuration data resources or non-configuration
data resources within the datastore. The "config" query parameter is
used to choose between them. Refer to Section 3.8.1 for more
details.
The depth of the subtrees returned in retrieval operations can be
controlled with the "depth" query parameter. The number of nest
levels, starting at the target resource, can be specified, or an
unlimited number can be returned. Refer to Section 3.8.2 for more
details.
[FIXME: not clear if top-level YANG data nodes MUST be containers or
lists.
A datastore resource can only be written directly with the PATCH
method. Only the configuration data resources within the datastore
resource can be edited directly with all methods.]
5.3. Data Resource
A data resource represents a YANG data node that is a descendant node
of a datastore resource. Only YANG container and list data node
types are considered to represent data resources. Other YANG data
nodes are considered to be fields within their parent resource.
For configuration data resources, the server MAY maintain a last-
modified timestamp for the resource, and return the "Last-Modified"
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header when it is retrieved with the GET or HEAD methods.
For configuration data resources, the server MAY maintain a resource
entity tag for the resource, and return the "ETag" header when it is
retrieved as the target resource with the GET or HEAD methods. The
resource entity tag SHOULD be changed to a new previously unused
value if changes to the resource or any configuration resource within
the resource is altered.
A data resource can be retrieved with the GET method, to retrieve
either configuration data resources or non-configuration data
resources within the target resource. The "config" query parameter
is used to choose between them. Refer to Section 3.8.1 for more
details.
The depth of the subtrees returned in retrieval operations can be
controlled with the "depth" query parameter. The number of nest
levels, starting at the target resource, can be specified, or an
unlimited number can be returned. Refer to Section 3.8.2 for more
details.
A configuration data resource can be altered by the client with some
of all of the edit operations, depending on the target resource and
the specific operation. Refer to Section 3 for more details on edit
operations.
5.3.1. Encoding YANG Instance Identifiers in the Request URI
In YANG, data nodes are named with an absolute XPath expression, from
the document root to the target resource. In RESTCONF, URL friendly
path expressions are used instead.
The YANG "instance-identifier" (i-i) data type is represented in
RESTCONF with the path expression format defined in this section.
+-------+-------------------------------------------+
| Name | Comments |
+-------+-------------------------------------------+
| point | Insertion point is always a full i-i |
| path | Request URI path is a full or partial i-i |
+-------+-------------------------------------------+
RESTCONF instance-identifier Type Conversion
The "path" component of the request URI contains the absolute path
expression that identifies the target resource. The "select" query
parameter is used to optionally identify the requested data nodes
within the target resource to be retrieved in a GET method.
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A predictable location for a data resource is important, since
applications will code to the YANG data model module, which uses
static naming and defines an absolute path location for all data
nodes.
A RESTCONF data resource identifier is not an XPath expression. It
is encoded from left to right, starting with the top-level data node,
according to the "api-path" rule in Section 5.3.1.1. The node name
of each ancestor of the target resource node is encoded in order,
ending with the node name for the target resource.
If the "select" is present, it is encoded, starting with a child node
of the target resource, according to the "api-select" rule defined in
Section 5.3.1.1.
If a data node in the path expression is a YANG list node, then the
key values for the list (if any) are encoded according to the
"key-value" rule. If the list node is the target resource, then the
key values MAY be omitted, according to the operation. For example,
the POST method to create a new data resource for a list node does
not allow the key values to be present in the request URI.
The key leaf values for a data resource representing a YANG list MUST
be encoded as follows:
o The value of each leaf identified in the "key" statement is
encoded in order.
o All the components in the "key" statement MUST be encoded.
Partial instance identifiers are not supported.
o Each value is encoded using the "key-value" rule in
Section 5.3.1.1, according to the encoding rules for the data type
of the key leaf.
o An empty string can be a valid key value (e.g., "/top/list/key1//
key3").
o The "/" character MUST be URL-encoded (i.e., "%2F").
o All whitespace MUST be URL-encoded.
o A "null" value is not allowed since the "empty" data type is not
allowed for key leafs.
o The XML encoding is defined in [RFC6020].
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o The JSON encoding is defined in [I-D.lhotka-netmod-json].
o The entire "key-value" MUST be properly URL-encoded, according to
the rules defined in [RFC3986].
o resource URI values returned in Location headers for data
resources SHOULD identify the module name, even if there are no
conflicting local names when the resource is created. This
insures the correct resource will be identified even if the server
loads a new module that the old client does not know about.
Examples:
[ lines wrapped for display purposes only ]
/restconf/datastore/example-jukebox:jukebox/library/
artist/Beatles&select=album
/restconf/datastore/example-list:newlist/
17&select=nextlist/22/44/acme-list-ext:ext-leaf
/restconf/datastore/example-list:somelist/
fred%20and%20wilma
/restconf/datastore/example-list:somelist/
fred%20and%20wilma/address
5.3.1.1. ABNF For Data Resource Identifiers
The following ABNF syntax is used to construct RESTCONF path
identifiers:
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api-path = "/" api-identifier
0*("/" (api-identifier | key-value ))
[FIXME: the syntax for the select string is still TBD]
api-select = api-identifier
0*("/" (api-identifier | key-value ))
api-identifier = [module-name ":"] identifier
module-name = identifier
key-value = string
;; An identifier MUST NOT start with
;; (('X'|'x') ('M'|'m') ('L'|'l'))
identifier = (ALPHA / "_")
*(ALPHA / DIGIT / "_" / "-" / ".")
string = <an unquoted string>
5.3.2. Data Resource Retrieval
There are three types of filtering for retrieval of data resources.
This section defines each mode.
5.3.2.1. Conditional Retrieval
The HTTP headers (such as "If-Modified-Since" and "If-Match") can by
used in for a request message for a GET method to check a condition
within the server state, such as the last time the datastore resource
was modified, or the resource entity tag of the target resource.
If the condition is met according to the header definition, a "200
OK" Status-Line and the data requested is returned in the response
message. If the condition is not met, a "304 Not Modified" Status-
Line is returned in response message instead.
5.3.2.2. Data Classification Retrieval
The "config" query parameter can be used with the GET method to
specify whether configuration or non-configuration data is requested.
Refer to Section 3.8.1 for more details on the "config" query
parameter.
5.3.2.3. Filtered Retrieval
The "select" query parameter is used to specify a filter that should
be applied to the target resource to request a subset of all possible
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descendant nodes within the target resource.
The format of the "select" parameter string is defined in
Section 3.8.6. The set of nodes selected by the filter expression is
applied to each context node identified by the target resource.
5.4. Operation Resource
An operation resource represents an protocol operation defined with
the YANG "rpc" statement.
All operation resources share the same module namespace as any top-
level data resources, so the name of an operation resource cannot
conflict with the name of a top-level data resource defined within
the same module.
If 2 different YANG modules define the same "rpc" identifier, then
the module name MUST be used in the request URI. For example, if
"module-A" and "module-B" both defined a "reset" operation, then
invoking the operation from "module-A" would be requested as follows:
POST /restconf/operations/module-A:reset HTTP/1.1
Server example.com
Any usage of an operation resource from the same module, with the
same name, refers to the same "rpc" statement definition. This
behavior can be used to design protocol operations that perform the
same general function on different resource types.
If the "rpc" statement has an "input" section, then a message body
MAY be sent by the client in the request, otherwise the request
message MUST NOT include a message body. If the "rpc" statement has
an "output" section, then a message body MAY be sent by the server in
the response. Otherwise the server MUST NOT include a message body
in the response message, and MUST send a "204 No Content" Status-Line
instead.
5.4.1. Encoding Operation Input Parameters
If the "rpc" statement has an "input" section, then the "input" node
is provided in the message body, corresponding to the YANG data
definition statements within the "input" section.
Example:
The following YANG definition is used for the examples in this
section.
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rpc reboot {
input {
leaf delay {
units seconds;
type uint32;
default 0;
}
leaf message { type string; }
leaf language { type string; }
}
}
The client might send the following POST request message:
POST /restconf/datastore/operations/
example-ops:reboot HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
{
"input" : {
"delay" : 600,
"message" : "Going down for system maintenance",
"language" : "en-US"
}
}
The server might respond:
HTTP/1.1 204 No Content
Date: Mon, 25 Apr 2012 11:01:00 GMT
Server: example-server
5.4.2. Encoding Operation Output Parameters
If the "rpc" statement has an "output" section, then the "output"
node is provided in the message body, corresponding to the YANG data
definition statements within the "output" section.
Example:
The following YANG definition is used for the examples in this
section.
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rpc get-reboot-info {
output {
leaf reboot-time {
units seconds;
type uint32;
}
leaf message { type string; }
leaf language { type string; }
}
}
The client might send the following POST request message:
POST /restconf/datastore/operations/example-ops:get-reboot-info
HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.data+json
The server might respond:
HTTP/1.1 200 OK
Date: Mon, 25 Apr 2012 11:10:30 GMT
Server: example-server
{
"output" : {
"reboot-time" : 30,
"message" : "Going down for system maintenance",
"language" : "en-US"
}
}
5.5. Event Resource
[TBD]
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6. Error Reporting
HTTP Status-Lines are used to report success or failure for RESTCONF
operations. The <rpc-error> element returned in NETCONF error
responses contains some useful information. This error information
is adapted for use in RESTCONF, and error information is returned for
"4xx" class of status codes.
The following table summarizes the return status codes used
specifically by RESTCONF operations:
+---------------------------+---------------------------------------+
| Status-Line | Description |
+---------------------------+---------------------------------------+
| 100 Continue | POST accepted, 201 should follow |
| 200 OK | Success with response body |
| 201 Created | POST to create a resource success |
| 202 Accepted | POST to create a resource accepted |
| 204 No Content | Success without response body |
| 304 Not Modified | Conditional operation not done |
| 400 Bad Request | Invalid request message |
| 403 Forbidden | Access to resource denied |
| 404 Not Found | Resource target or resource node not |
| | found |
| 405 Method Not Allowed | Method not allowed for target |
| | resource |
| 409 Conflict | Resource or lock in use |
| 413 Request Entity Too | too-big error |
| Large | |
| 414 Request-URI Too Large | too-big error |
| 415 Unsupported Media | non RESTCONF media type |
| Type | |
| 500 Internal Server Error | operation-failed |
| 501 Not Implemented | unknown-operation |
| 503 Service Unavailable | Recoverable server error |
+---------------------------+---------------------------------------+
HTTP Status Codes used in RESTCONF
Since an operation resource is defined with a YANG "rpc" statement, a
mapping between the NETCONF <error-tag> value and the HTTP status
code is needed. The specific error condition and response code to
use are data-model specific and might be contained in the YANG
"description" statement for the "rpc" statement.
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+-------------------------+-------------+
| <error-tag> | status code |
+-------------------------+-------------+
| in-use | 409 |
| invalid-value | 400 |
| too-big | 413 |
| missing-attribute | 400 |
| bad-attribute | 400 |
| unknown-attribute | 400 |
| bad-element | 400 |
| unknown-element | 400 |
| unknown-namespace | 400 |
| access-denied | 403 |
| lock-denied | 409 |
| resource-denied | 409 |
| rollback-failed | 500 |
| data-exists | 409 |
| data-missing | 409 |
| operation-not-supported | 501 |
| operation-failed | 500 |
| partial-operation | 500 |
| malformed-message | 400 |
+-------------------------+-------------+
Mapping from error-tag to status code
6.1. Error Response Message
When an error occurs for a request message on a data resource or an
operation resource, and a "4xx" class of status codes (except for
status code "403"), then the server SHOULD send a response body
containing the information described by the "errors" container
definition within the YANG module Section 8.
Example:
The following example shows an error returned for an "lock-denied"
error on a datastore resource.
POST /restconf/operations/example-ops:lock-datastore HTTP/1.1
Host: example.com
The server might respond:
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HTTP/1.1 409 Conflict
Date: Mon, 23 Apr 2012 17:11:00 GMT
Server: example-server
Content-Type: application/vnd.yang.api+json
{
"errors": {
"error": {
"error-type": "protocol",
"error-tag": "lock-denied",
"error-message": "Lock failed, lock is already held",
}
}
}
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7. YANG Patch
The YANG Patch operation is provided so complex editing operations
can be performed within RESTCONF. The "plain patch" operation only
provides a simple merge edit operation on the target datastore.
A "YANG Patch" is an ordered list of edits that are applied to the
target datastore by the server. The specific fields are defined with
the 'yang-patch' container definition in the YANG module Section 8.
Each patch is identified by a client provided string, called the
"patch-id".
The client can control the type of error handling that should be
applied to the list of supplied edits.
7.1. Why not use JSON Patch?
The RESTCONF PATCH method requires that the media type of the patch
content be specified, so it should be possible to use any patch
mechanism, including JSON Patch [RFC6902].
The RESTCONF protocol is designed to utilize the YANG data modelling
language to specify content schemas. The JSON Patch mechanism is
incompatible with RESTCONF for the following reasons:
o A patch mechanism that works with either XML or JSON encoding is
needed.
o YANG configuration nodes can be named with complex keys, using one
or more key leafs. JSON arrays are packed and all the YANG keys
would be collapsed down to a single integer index.
o YANG configuration nodes are named with stable, persistent
identifiers, using key leafs. JSON arrays are packed, and if
entry I is added or deleted, then all entries I+1 .. Imax are
renumbered.
o The edit operation set needs to align with the NETCONF protocol,
and JSON Patch does not provide an aligned set of edit operations.
o The datastore validation procedures need to be specific and
aligned with YANG validation procedures.
o The error reporting needs to align with the NETCONF protocol, and
JSON Patch does not provide an aligned error reporting mechanism.
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7.2. YANG Patch Target Data Node
The target data node for each edit operation is determined by the
value of the target resource in the request and the "target" leaf
within each "edit" entry.
If the target resource specified in the request URI identifies a
datastore resource, then the path string in the "target" leaf is an
absolute path expression. The first node specified in the "target"
leaf is a top-level data node defined within a YANG module.
If the target resource specified in the request URI identifies a data
resource, then the path string in the "target" leaf is a relative
path expression. The first node specified in the "target" leaf is a
child node of the data node associated with the target resource.
7.3. YANG Patch Edit Operations
Each YANG patch edit specifies one edit operation on the target data
node. The set of operations is aligned with the NETCONF edit
operations, but also includes some new operations.
+-----------+-------------------------------------------------------+
| Operation | Description |
+-----------+-------------------------------------------------------+
| create | create a new data resource if it does not already |
| | exist or error |
| delete | delete a data resource if it already exists or error |
| insert | insert a new user-ordered data resource |
| merge | merge the edit value with the target data resource; |
| | create if it does not already exist |
| move | re-order the target data resource |
| replace | replace the target data resource with the edit value |
| remove | remove a data resource if it already exists or no |
| | error |
+-----------+-------------------------------------------------------+
YANG Patch Edit Operations
7.4. YANG Patch Error Handling
There are three error handling modes available that the server MUST
support. These modes specify how the server will behave when errors
occur in the processing of each edit operation. Note that the server
MUST ensure that a well-formed message is received and that the
supplied message body conforms to the YANG schema definition for the
"patch" container, defined in the YANG module Section 8.
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If a well-formed, schema-valid YANG Patch message is received, then
then the server will process the supplied edits in ascending order.
The following error modes apply to the processing of this edit list:
o all-or-none: All the specified edits MUST be applied or the target
datastore contents SHOULD be returned to its original state before
the PATCH method started. The server MAY fail to restore the
contents of the target datastore completely and with certainty.
It is possible for a rollback to fail or and "undo" operation to
fail.
o stop-on-error: Each edit will be attempted in order and if an
error occurs, the the server will stop processing the edit list
and return an error report identifying the edit list entry that
caused the error.
o continue-on-error: Each edit will be attempted in order and if an
error occurs, the the server will record an error identifying the
edit list entry that caused the error, and continue to the next
edit entry.
The server will save the running datastore to non-volatile storage if
it has changed, after the edits have been attempted.
7.5. YANG Patch Response
A special response is returned for YANG Patch operations, in order to
report status information for each individual edit. It is possible
to report general errors as well. The YANG conceptual container
definition "yang-patch-status" defined in Section 8 is used to define
the syntax.
7.6. YANG Patch Examples
7.6.1. Continue-on-error Example
The following example shows several songs being added to an existing
album.
o Each edit contains one song.
o The first song already exists, so an error will be reported for
that edit.
o The error-action is continue-on-error, so the rest of the songs
will be added without error.
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Request from client:
PATCH /restconf/datastore/example-jukebox:jukebox/
library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.patch+json
{
"yang-patch" : {
"patch-id" : "add-songs-patch",
"error-action" : "continue-on-error",
"edit" : [
{
"edit-id" : 1,
"operation" : "create",
"target" : "/song",
"value" : {
"song" : {
"name" : "Bridge Burning",
"location" : "/media/bridge_burning.mp3",
"format" : "MP3",
"length" : 288
}
}
},
{
"edit-id" : 2,
"operation" : "create",
"target" : "/song",
"value" : {
"song" : {
"name" : "Rope",
"location" : "/media/rope.mp3",
"format" : "MP3",
"length" : 259
}
}
},
{
"edit-id" : 3,
"operation" : "create",
"target" : "/song",
"value" : {
"song" : {
"name" : "Dear Rosemary",
"location" : "/media/dear_rosemary.mp3",
"format" : "MP3",
"length" : 269
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}
}
}
]
}
}
Response from server:
HTTP/1.1 409 Conflict
Date: Mon, 23 Apr 2012 13:01:20 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
Content-Type: application/vnd.yang.api+json
{
"yang-patch-status" : {
"patch-id" : "add-songs-patch",
"edit-status" : {
"edit" : [
{
"edit-id" : 1,
"errors" : {
"error" : {
"error-type": "application",
"error-tag": "data-exists",
"error-path": "/example-jukebox:jukebox/library/artist/
Foo%20Fighters/album/Wasting%20Light/song/
Burning%20Light",
"error-message": "Data already exists, cannot be
created"
}
},
{
"edit-id" : 2,
"location" : "http://example.com/restconf/
datastore/example-jukebox:jukebox/library/artist/
Foo%20Fighters/album/Wasting%20Light/song/Rope"
},
{
"edit-id" : 3,
"location" : "http://example.com/restconf/
datastore/example-jukebox:jukebox/library/artist/
Foo%20Fighters/album/Wasting%20Light/song/
Dear%20Rosemary"
}
}
]
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}
}
}
7.6.2. Move list entry example
The following example shows a song being moved within an existing
playlist. Song "1" in playlist "Foo-One" is being moved after song
"3" in the playlist. The operation succeeds, so a non-error reply
example can be shown.
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Request from client:
PATCH /restconf/datastore/example-jukebox:jukebox/
playlist/Foo-One HTTP/1.1
Host: example.com
Content-Type: application/vnd.yang.patch+json
{
"yang-patch" : {
"patch-id" : "move-song-patch",
"error-action" : "all-or-none",
"edit" : [
{
"edit-id" : 1,
"operation" : "move",
"target" : "/song/1",
"point" : "/song3",
"where" : "after"
}
]
}
}
Response from server:
HTTP/1.1 400 OK
Date: Mon, 23 Apr 2012 13:01:20 GMT
Server: example-server
Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
Content-Type: application/vnd.yang.api+json
{
"yang-patch-status" : {
"patch-id" : "move-song-patch",
"edit-status" : {
"edit" : [
{
"edit-id" : 1,
"ok" : [ null ]
}
}
]
}
}
}
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8. RESTCONF module
The "ietf-restconf" module defines conceptual definitions within
groupings, which are not meant to be implemented as datastore
contents by a server.
The "ietf-yang-types" and "ietf-inet_types" modules from [RFC6991]
are used by this module for some type definitions.
RFC Ed.: update the date below with the date of RFC publication and
remove this note.
<CODE BEGINS> file "ietf-restconf@2013-09-09.yang"
module ietf-restconf {
// RFC Ed.: replace XXXX with 'ietf' and remove this note
namespace "urn:XXXX:params:xml:ns:yang:ietf-restconf";
prefix "restconf";
import ietf-yang-types { prefix yang; }
import ietf-inet-types { prefix inet; }
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"Editor: Andy Bierman
<mailto:andy@yumaworks.com>
Editor: Martin Bjorklund
<mailto:mbj@tail-f.com>
Editor: Kent Watsen
<mailto:kwatsen@juniper.net>
Editor: Rex Fernando
<mailto:rex@cisco.com>";
description
"This module contains conceptual YANG specifications
for the YANG Patch and error content that is used in
RESTCONF protocol messages. A conceptual container
representing the RESTCONF API nodes (type vnd.yang.api).
Note that the YANG definitions within this module do not
represent configuration data of any kind.
The YANG grouping statements provide a normative syntax
for XML and JSON message encoding purposes.
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Copyright (c) 2013 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.";
// RFC Ed.: replace XXXX with actual RFC number and remove this
// note.
// RFC Ed.: remove this note
// Note: extracted from draft-bierman-netconf-restconf-01.txt
// RFC Ed.: update the date below with the date of RFC publication
// and remove this note.
revision 2013-09-09 {
description
"Initial revision.";
reference
"RFC XXXX: RESTCONF Protocol.";
}
typedef data-resource-identifier {
type string {
length "1 .. max";
}
description
"Contains a Data Resource Identifier formatted string
to identify a specific data node.";
reference
"RFC XXXX: [sec. 5.3.1.1 ABNF For Data Resource Identifiers]";
}
// this typedef is TBD; not currently used
typedef datastore-identifier {
type union {
type enumeration {
enum candidate {
description
"Identifies the NETCONF shared candidate datastore.";
reference
"RFC 6241, section 8.3";
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}
enum running {
description
"Identifies the NETCONF running datastore.";
reference
"RFC 6241, section 5.1";
}
enum startup {
description
"Identifies the NETCONF startup datastore.";
reference
"RFC 6241, section 8.7";
}
}
type string;
}
description
"Contains a string to identify a specific datastore.
The enumerated datastore identifier values are
reserved for standard datastore names.";
}
typedef revision-identifier {
type string {
pattern '\d{4}-\d{2}-\d{2}';
}
description
"Represents a specific date in YYYY-MM-DD format.
TBD: make pattern more precise to exclude leading zeros.";
}
grouping yang-patch {
description
"A grouping that contains a YANG container
representing the syntax and semantics of a
YANG Patch edit request message.";
container yang-patch {
description
"Represents a conceptual sequence of datastore edits,
called a patch. Each patch is given a client-assigned
patch identifier. A patch is applied with client-specified
error handling to control how the ordered list of edits
is applied if an error is encountered.
A patch MUST be validated by the server to be a
well-formed message before any of the patch edits
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are validated or attempted.
The validation model for patches closely follows
the constraint enforcement model in YANG, except it
is conceptually enforced on an ordered list of edits.
The server MUST conceptually perform field validation
for each edit in ascending order, as defined in RFC 6020,
section 8.3.1 and 8.3.2. This is most relevant if the edit
error-action is 'stop-on-error', since the identification
of the first error determines where edit processing is
terminated.
If YANG datastore validation (defined in RFC 6020, section
8.3.3) is required, then it performed after all edits have
been individually validated.
It is possible for a datastore constraint violation to occur
due to any node in the datastore, including nodes not
included in the edit list. Any validation errors SHOULD
be reported in the reply message.
If datastore validation is required and fails, the server
SHOULD NOT allow the datastore to remain invalid. It is an
implementation-specific matter how the server fixes the
invalid datastore. For example, the server might prune
invalid nodes causing the datastore validation error,
or undo the entire patch.";
reference
"RFC 6020, section 8.3.";
leaf patch-id {
type string;
description
"An arbitrary string provided by the client to identify
the entire patch. This value SHOULD be present in any
audit logging records generated by the server for the
patch. Error messages returned by the server pertaining
to this patch will be identified by this patch-id value.";
}
leaf error-action {
type enumeration {
enum all-or-none {
description
"The server will apply all edits in the patch only
if no errors occur. If any errors occur then
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none of the edits will be applied and the
contents of the target datastore MUST be unchanged.";
}
enum stop-on-error {
description
"The server will apply edits in the specified order
and will stop processing edits if any error occurs.
Any previous edits which were successfully applied
will remain applied. No further edits will be
attempted after the first error is encountered.";
}
enum continue-on-error {
description
"The server will apply edits in the specified order
and will continue processing edits if any error
occurs.";
}
}
default all-or-none;
description
"The error handling behavior for the ordered list of
edits.";
}
list edit {
key edit-id;
description
"Represents one edit within the YANG Patch
request message.";
leaf edit-id {
type uint32;
description
"Arbitrary integer index for the edit.
The server MUST process edits in ascending order.
Error messages returned by the server pertaining
to a specific edit will be identified by this
identifier value.";
}
leaf operation {
type enumeration {
enum create {
description
"The target data node is created using the
supplied value, only if it does not already
exist.";
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}
enum delete {
description
"Delete the target node, only if the data resource
currently exists, otherwise return an error.";
}
enum insert {
description
"Insert the supplied value into a user-ordered
list or leaf-list entry. The target node must
represent a new data resource.";
}
enum merge {
description
"The supplied value is merged with the target data
node.";
}
enum move {
description
"Move the target node. Reorder a user-ordered
list or leaf-list. The target node must represent
an existing data resource.";
}
enum replace {
description
"The supplied value is used to replace the target
data node.";
}
enum remove {
description
"Delete the target node if it currently exists.";
}
}
mandatory true;
description
"The datastore operation requested for the associated
edit entry";
}
leaf target {
type data-resource-identifier;
mandatory true;
description
"Identifies the target data resource for the edit
operation.";
}
leaf point {
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when "(../operation = 'insert' or " +
"../operation = 'move') and " +
"(../where = 'before' or ../where = 'after')" {
description
"Point leaf only applies for insert or move
operations, before or after an existing entry.";
}
type data-resource-identifier;
description
"The absolute URL path for the data node that is being
used as the insertion point or move point for the
target of this edit entry.";
}
leaf where {
when "../operation = 'insert' or ../operation = 'move'" {
description
"Where leaf only applies for insert or move
operations.";
}
type enumeration {
enum before {
description
"Insert or move a data node before the data resource
identified by the 'point' parameter.";
}
enum after {
description
"Insert or move a data node after the data resource
identified by the 'point' parameter.";
}
enum first {
description
"Insert or move a data node so it becomes ordered
as the first entry.";
}
enum last {
description
"Insert or move a data node so it becomes ordered
as the last entry.";
}
}
default last;
description
"Identifies where a data resource will be inserted or
moved. YANG only allows these operations for
list and leaf-list data nodes that are ordered-by
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user.";
}
anyxml value {
when "(../operation = 'create' or " +
"../operation = 'merge' " +
"or ../operation = 'replace' or " +
"../operation = 'insert')" {
description
"Value node only used for create, merge,
replace, and insert operations";
}
description
"Value used for this edit operation.";
}
}
}
} // grouping yang-patch
grouping yang-patch-status {
description
"A grouping that contains a YANG container
representing the syntax and semantics of
YANG Patch status response message.";
container yang-patch-status {
description
"A container representing the response message
sent by the server after a YANG Patch edit
request message has been processed.";
leaf patch-id {
type string;
description
"The patch-id value used in the request";
}
container global-errors {
uses errors;
description
"This container will be present if global
errors unrelated to a specific edit occurred.";
}
container edit-status {
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description
"This container will be present if there are
edit-specific status responses to report.";
list edit {
key edit-id;
description
"Represents a list of status responses,
corresponding to edits in the YANG Patch
request message.";
leaf edit-id {
type uint32;
description
"Response status is for the edit list entry
with this edit-id value.";
}
choice edit-status-choice {
description
"A choice between different types of status
responses for each edit entry.";
leaf ok {
type empty;
description
"This edit entry was invoked without any
errors detected by the server associated
with this edit.";
}
leaf location {
type inet:uri;
description
"Contains the Location header value that would be
returned if this edit causes a new resource to be
created. If the edit identified by the same edit-id
value was successfully invoked and a new resource
was created, then this field will be returned
instead of 'ok'.";
}
leaf skipped {
type empty;
description
"This edit entry was skipped or not reached
by the server.";
}
case errors {
uses errors;
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description
"The server detected errors associated with the
edit identified by the same edit-id value.";
}
}
}
}
}
} // grouping yang-patch-status
grouping errors {
description
"A grouping that contains a YANG container
representing the syntax and semantics of a
YANG Patch errors report within a response message.";
container errors {
config false; // needed so list error does not need a key
description
"Represents an error report returned by the server if
a request results in an error.";
list error {
description
"An entry containing information about one
specific error that occurred while processing
a RESTCONF request.";
reference "RFC 6241, Section 4.3";
leaf error-type {
type enumeration {
enum transport {
description "The transport layer";
}
enum rpc {
description "The rpc or notification layer";
}
enum protocol {
description "The protocol operation layer";
}
enum application {
description "The server application layer";
}
}
mandatory true;
description
"The protocol layer where the error occurred.";
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}
leaf error-tag {
type string;
mandatory true;
description
"The enumerated error tag.";
}
leaf error-app-tag {
type string;
description
"The application-specific error tag.";
}
leaf error-path {
type data-resource-identifier;
description
"The target data resource identifier associated
with the error, if any.";
}
leaf error-message {
type string;
description
"A message describing the error.";
}
container error-info {
description
"A container allowing additional information
to be included in the error report.";
// arbitrary anyxml content here
}
}
}
} // grouping errors
grouping restconf {
description
"A grouping that contains a YANG container
representing the syntax and semantics of
the RESTCONF API resource.";
container restconf {
description
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"Conceptual container representing the vnd.yang.api
resource type.";
container datastore {
description
"Container representing the vnd.yang.datastore resource
type. Represents the conceptual root of the unified
datastore containing YANG data nodes. The child nodes
of this container can be data resources (vnd.yang.data)
defined as top-level YANG data nodes from the modules
advertised by the server in /restconf/modules.";
}
container modules {
description
"Contains a list of module description entries.
These modules are currently loaded into the server.";
list module {
key "name revision";
description
"Each entry represents one module currently
supported by the server.";
leaf name {
type yang:yang-identifier;
description "The YANG module name.";
}
leaf revision {
type union {
type revision-identifier;
type string { length 0; }
}
description
"The YANG module revision date. An empty string is
used if no revision statement is present in the
YANG module.";
}
leaf namespace {
type inet:uri;
mandatory true;
description
"The XML namespace identifier for this module.";
}
leaf-list feature {
type yang:yang-identifier;
description
"List of YANG feature names from this module that are
supported by the server.";
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}
leaf-list deviation {
type yang:yang-identifier;
description
"List of YANG deviation module names used by this
server to modify the conformance of the module
associated with this entry.";
}
}
}
container operations {
description
"Container for all operation resources
(vnd.yang.operation),
Each resource is represented as an empty leaf with the
name of the RPC operation from the YANG rpc statement.
E.g.;
POST /restconf/operations/show-log-errors
leaf show-log-errors {
type empty;
}
";
}
leaf version {
type enumeration {
enum "1.0" {
description
"Version 1.0 of the RESTCONF protocol.";
}
}
config false;
description
"Contains the RESTCONF protocol version.";
}
}
} // grouping restconf
}
<CODE ENDS>
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9. IANA Considerations
9.1. YANG Module Registry
This document registers one URI in the IETF XML registry [RFC3688].
Following the format in RFC 3688, the following registration is
requested to be made.
// RFC Ed.: replace XXXX with 'ietf' and remove this note
URI: urn:XXXX:params:xml:ns:yang:ietf-restconf
Registrant Contact: The NETMOD WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
This document registers one YANG module in the YANG Module Names
registry [RFC6020].
name: ietf-restconf
namespace: urn:ietf:params:xml:ns:yang:ietf-restconf
prefix: restconf
// RFC Ed.: replace XXXX with RFC number and remove this note
reference: RFC XXXX
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10. Security Considerations
TBD
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11. Change Log
-- RFC Ed.: remove this section before publication.
11.1. 00 to 01
o Removed incorrect /.well-known URI prefix.
o remove incorrect IANA request for well-known URI.
o Clarified that API resource type nodes are defined in the ietf-
restconf namespace.
o changed CamelCase names in example-jukebox.yang to lowercase, and
updated examples.
o updated and corrected YANG types in ietf-restconf module.
11.2. YANG-API-01 to RESTCONF-00
o Protocol renamed from YANG-API to RESTCONF
o Fields are clarified. Containers and lists are sub-resources.
All other YANG data node types are fields within a parent
resource.
o The 'optional-key' YANG extension has been removed.
o The default value is returned by the server if the target resource
represents a missing data node but the server is using a default
value for the leaf.
o The default for the 'depth' parameter has been changed from '1' to
'unbounded'. The depth is only limited if an integer value for
this parameter is specified by the client.
o The default for the 'format' parameter has been changed from
'json' to 'xml'.
o expanded introduction
o removed transactions
o removed capabilities
o removed usage of Range and IfRange headers
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o simplified editing model
o removed global protocol operations from ietf-restconf.yang
o changed RPC operation terminology to protocol operation
o updated JSON draft reference
o updated IANA section
o added YANG Patch
o added YANG definitions to ietf-restconf.yang
o added Kent Watsen and Rex Fernando as co-authors
o updated YANG modules so they pass pyang --ietf checking
o changed examples so resource URIs use the module name variant to
identify data resources
o changed depth behavior so the entire server contents are not
returned for "GET /restconf"; Server will stop at new resource
type; e.g. yang.api --> yang.datastore returns the datastore as an
empty node; yang.api --> yang.operation returns the operation name
as an empty node;
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12. Closed Issues
o Which WG should do this work? NETCONF? NETMOD? It is not clear
since RESTCONF builds on concepts and standards from documents
owned by both working groups.
A: The NETCONF WG would do this work.
o Should sessions be used or not? Should "reusable sessions" be
used? Better for auditing? How does locking of the /restconf/
datastore resource work for multiple edits if a session is 1
operation? When does the server release the lock and decide it
has been abandoned or client was disconnected?
A: RESTCONF is a session-less protocol. It could be implemented to
utilize persistent HTTP connections, but this is not required or
designed into the protocol.
o Should the "/restconf/modules" resource within the API resource be
a separate resource, with its own timestamp? Currently the API
timestamp is coupled to any changes to the list of loaded modules.
Should the API resource be static and cacheable?
A: all child containers are considered sub-resources. The server MAY
support timestamps and entity IDs for data nodes.
o What to do about no REMOVE operation, just DELETE? The effect is
local to the request; in a NETCONF edit-config it is worse, since
the netconf request might create/delete/modify many nodes
A: The YANG Patch operation allows remove or delete semantics.
o Should every YANG data node be a data resource and every YANG RPC
statement an operation resource? Is a YANG extension needed to
allow data modeler control of resource boundaries?
A: Nested containers and lists are considered sub-resources.
Terminal nodes (leaf, leaf-list, anyxml) are considered properties of
the parent resource.
o Resource creation order and other dependencies between resources
are not well identified in YANG. YANG has leafrefs and instance-
identifiers, which can be used to identify some order
dependencies. Are any new mechanisms needed in RESTCONF needed to
identify resource creation order and other dependency
requirements?
A: YANG Patch allows the client to control creation order when
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multiple resources need to be edited at once. The edit operations
allow the server to order all the descendant resources provided by
the client, for a single datastore edit target node.
o Encoding of leafrefs? Is there some additional meta-data needed?
Do leafref nodes need to be identified in responses (RFC 5988) or
is the YANG module definition sufficient to provide this meta-
data?
A: no special message encoding of leaf-refs is needed. The server
must understand the YANG schema no matter what protocol or encoding
is used.
o What should the default algorithm be for defining data resources?
Should the default for an augment from another namespace be to
start a new resource? Top-level data node defaults as a resource
OK?
A: Augmented nodes do not follow different rules than other nested
YANG structures. Containers and lists start new sub-resources.
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13. Open Issues
o There is no "message-id" field in a RESTCONF message. Is a
message identifier needed? If so, should either the "Message-ID"
or "Content-ID" header from RFC 2392 be used for this purpose?
o What syntax should be used for the "select" query parameter? The
current choices are "xpath" and "path-expr". Perhaps an
additional parameter to identify the select string format is
needed to allow extensibility?
o Are all header lines used by RESTCONF supported by common
application frameworks, such as FastCGI and WSGI? If not, then
should query parameters be used instead, since the QUERY_STRING is
widely available to WEB applications?
o Should the <errors> element returned in error responses be a
separate media type?
o How should additional datastores be supported, which may be added
to the NETCONF/NETMOD framework in the future?
o How does a client know which PATCH media types are supported by
the server in addition to application/vnd.yang.data and
application/vnd.yang.patch?
o Is the /restconf/version field considered meta-data? Should it be
returned as XRD (Extensible Resource Descriptor)? In addition or
instead of the version field? Should this be the ietf-restconf
YANG module revision date, instead of the string 1.0?
o Notification message delivery is TBD
o Alignment between NETCONF and RESTCONF notification is expected to
be very close to RFC 5277 design. Additional Sub/pub features
still TBD.
o Some sections may need to be rewritten to support notifications
and event resources
o Since data resources can only be YANG containers or lists, what
should be done about top-level YANG data nodes that are not
containers or lists? Are they allowed in RESTCONF?
o Can a choice be a resource? YANG choices are invisible to
RESTCONF at this time.
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o Does RESTCONF need to Use a .well-known link relation to to re-map
API entry point?
The client first discovers the server's root for the RESTCONF API.
In this example, it is "/api/restconf":
Request
-------
GET /.well-known/host-meta users HTTP/1.1
Host: example.com
Accept: application/xrd+xml
Response
--------
HTTP/1.1 200 OK
Content-Type: application/xrd+xml
Content-Length: nnn
<XRD xmlns='http://docs.oasis-open.org/ns/xri/xrd-1.0'>
<Link rel='restconf' href='/api/restconf'/>
</XRD>
Once discovering the RESTCONF API root, the client MUST prepend it to
any access to a RESTCONF resource:
Request
-------
GET /api/restconf?select=version&format=json HTTP/1.1
Host: example.com
Accept: application/vnd.yang.api+json
Response
--------
HTTP/1.1 200 OK
Date: Mon, 23 Apr 2012 17:01:00 GMT
Server: example-server
Cache-Control: no-cache
Pragma: no-cache
Last-Modified: Sun, 22 Apr 2012 01:00:14 GMT
Content-Type: application/vnd.yang.api+json
{ "version": "1.0" }
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14. Example YANG Module
module example-jukebox {
namespace "http://example.com/ns/example-jukebox";
prefix "jbox";
organization "Example, Inc.";
contact "support at example.com";
description "Example Jukebox Data Model Module";
revision "2013-09-09" {
description "Initial version.";
reference "example.com document 1-4673";
}
identity genre {
description "Base for all genre types";
}
// abbreviated list of genre classifications
identity alternative {
base genre;
description "Alternative music";
}
identity blues {
base genre;
description "Blues music";
}
identity country {
base genre;
description "Country music";
}
identity jazz {
base genre;
description "Jazz music";
}
identity pop {
base genre;
description "Pop music";
}
identity rock {
base genre;
description "Rock music";
}
container jukebox {
presence
"An empty container indicates that the jukebox
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service is available";
description
"Represents a jukebox resource, with a library, playlists,
and a play operation.";
container library {
description "Represents the jukebox library resource.";
list artist {
key name;
description
"Represents one artist resource within the
jukebox library resource.";
leaf name {
type string {
length "1 .. max";
}
description "The name of the artist.";
}
list album {
key name;
description
"Represents one album resource within one
artist resource, within the jukebox library.";
leaf name {
type string {
length "1 .. max";
}
description "The name of the album.";
}
leaf genre {
type identityref { base genre; }
description
"The genre identifying the type of music on
the album.";
}
leaf year {
type uint16 {
range "1900 .. max";
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}
description "The year the album was released";
}
list song {
key name;
description
"Represents one song resource within one
album resource, within the jukebox library.";
leaf name {
type string {
length "1 .. max";
}
description "The name of the song";
}
leaf location {
type string;
mandatory true;
description
"The file location string of the
media file for the song";
}
leaf format {
type string;
description
"An identifier string for the media type
for the file associated with the
'location' leaf for this entry.";
}
leaf length {
type uint32;
units "seconds";
description
"The duration of this song in seconds.";
}
} // end list 'song'
} // end list 'album'
} // end list 'artist'
leaf artist-count {
type uint32;
units "songs";
config false;
description "Number of artists in the library";
}
leaf album-count {
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type uint32;
units "albums";
config false;
description "Number of albums in the library";
}
leaf song-count {
type uint32;
units "songs";
description "Number of songs in the library";
}
} // end library
list playlist {
key name;
description
"Example configuration data resource";
leaf name {
type string;
description
"The name of the playlist.";
}
leaf description {
type string;
description
"A comment describing the playlist.";
}
list song {
key index;
ordered-by user;
description
"Example nested configuration data resource";
leaf index { // not really needed
type uint32;
description
"An arbitrary integer index for this
playlist song.";
}
leaf id {
type instance-identifier;
mandatory true;
description
"Song identifier. Must identify an instance of
/jukebox/library/artist/album/song/name.";
}
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}
}
container player {
description
"Represents the jukebox player resource.";
leaf gap {
type decimal64 {
fraction-digits 1;
range "0.0 .. 2.0";
}
units "tenths of seconds";
description "Time gap between each song";
}
}
}
rpc play {
description "Control function for the jukebox player";
input {
leaf playlist {
type string;
mandatory true;
description "playlist name";
}
leaf song-number {
type uint32;
mandatory true;
description "Song number in playlist to play";
}
}
}
}
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15. References
15.1. Normative References
[I-D.lhotka-netmod-json]
Lhotka, L., "Modeling JSON Text with YANG",
draft-lhotka-netmod-yang-json-01 (work in progress),
April 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, March 2010.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, June 2011.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", RFC 6536,
March 2012.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991,
July 2013.
15.2. Informative References
[RFC6902] Bryan, P. and M. Nottingham, "JavaScript Object Notation
(JSON) Patch", RFC 6902, April 2013.
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Authors' Addresses
Andy Bierman
YumaWorks
Email: andy@yumaworks.com
Martin Bjorklund
Tail-f Systems
Email: mbj@tail-f.com
Kent Watsen
Juniper Networks
Email: kwatsen@juniper.net
Rex Fernando
Cisco
Email: rex@cisco.com
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