RFC 6243
With-defaults Capability for NETCONF
With-defaults Capability for NETCONF 🎀
- Authors: A. Bierman (Brocade) and B. Lengyel (Ericsson) 🧚
- Category: Standards Track
- ISSN: 2070-1721
- Date: June 2011
- Obsoletes/Updates: nothing listed in the title block, so there's nothing to add here 🌸
Abstract ✨
Okay so NETCONF is the protocol for reading and editing config data on a NETCONF server 🦋. Sometimes a piece of that data isn't set by the client at all, and the server just uses a default value it already knows about. Honestly, a lot of the time the client already knows what the defaults are, so the server doesn't need to store them in a datastore or send them back in a reply. Other times the client actually needs that data from the server. And here's the tea: not every server handles default data the same way 🫠. This doc defines a capability-based extension so a client can figure out how a server processes defaults, plus brand-new ways for the client to control that processing. Main character energy, fr 💅
Status of This Memo 📜
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6243. 🦋
Copyright Notice 💜
Copyright (c) 2011 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 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. 🫶
Table of Contents 🍓
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Default-Handling Behavior . . . . . . . . . . . . . . . . 5
1.3. Client Controlled Retrieval of Default Data . . . . . . . 5
2. Default-Handling Basic Modes . . . . . . . . . . . . . . . . . 6
2.1. 'report-all' Basic Mode . . . . . . . . . . . . . . . . . 6
2.1.1. 'report-all' Basic Mode Retrieval . . . . . . . . . . 6
2.1.2. 'report-all' <with-defaults> Retrieval . . . . . . . . 6
2.1.3. 'report-all' <edit-config> and <copy-config>
Behavior . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. 'trim' Basic Mode . . . . . . . . . . . . . . . . . . . . 7
2.2.1. 'trim' Basic Mode Retrieval . . . . . . . . . . . . . 7
2.2.2. 'trim' <with-defaults> Retrieval . . . . . . . . . . . 7
2.2.3. 'trim' <edit-config> and <copy-config> Behavior . . . 7
2.3. 'explicit' Basic Mode . . . . . . . . . . . . . . . . . . 8
2.3.1. 'explicit' Basic Mode Retrieval . . . . . . . . . . . 8
2.3.2. 'explicit' <with-defaults> Retrieval . . . . . . . . . 8
2.3.3. 'explicit' <edit-config> and <copy-config> Behavior . 8
3. Retrieval of Default Data . . . . . . . . . . . . . . . . . . 9
3.1. 'report-all' Retrieval Mode . . . . . . . . . . . . . . . 9
3.2. 'trim' Retrieval Mode . . . . . . . . . . . . . . . . . . 9
3.3. 'explicit' Retrieval Mode . . . . . . . . . . . . . . . . 9
3.4. 'report-all-tagged' Retrieval Mode . . . . . . . . . . . . 9
4. With-defaults Capability . . . . . . . . . . . . . . . . . . . 10
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Dependencies . . . . . . . . . . . . . . . . . . . . . . . 10
4.3. Capability Identifier . . . . . . . . . . . . . . . . . . 10
4.4. New Operations . . . . . . . . . . . . . . . . . . . . . . 11
4.5. Modifications to Existing Operations . . . . . . . . . . . 11
4.5.1. <get>, <get-config>, and <copy-config> Operations . . 11
4.5.2. <edit-config> Operation . . . . . . . . . . . . . . . 12
4.5.3. Other Operations . . . . . . . . . . . . . . . . . . . 13
4.6. Interactions with Other Capabilities . . . . . . . . . . . 13
5. YANG Module for the <with-defaults> Parameter . . . . . . . . 13
6. XSD for the 'default' Attribute . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
10. Normative References . . . . . . . . . . . . . . . . . . . . . 19
Appendix A. Usage Examples . . . . . . . . . . . . . . . . . . . 20
A.1. Example YANG Module . . . . . . . . . . . . . . . . . . . 20
A.2. Example Data Set . . . . . . . . . . . . . . . . . . . . . 21
A.3. Protocol Operation Examples . . . . . . . . . . . . . . . 22
A.3.1. <with-defaults> = 'report-all' . . . . . . . . . . . . 22
A.3.2. <with-defaults> = 'report-all-tagged' . . . . . . . . 23
A.3.3. <with-defaults> = 'trim' . . . . . . . . . . . . . . . 24
A.3.4. <with-defaults> = 'explicit' . . . . . . . . . . . . . 251. Introduction ✨
The NETCONF protocol [RFC6241] lets you read configuration and state data from a NETCONF server 💖. Part of that configuration data might not be set by the NETCONF client, and is instead filled in by a default value from the data model. A lot of the time the NETCONF client already has a priori knowledge about that default data, so the NETCONF server doesn't need to send it over. That a priori knowledge can come from, e.g., a document that formally describes the data models the NETCONF server supports 🎀.
It can be really important for a client to know exactly how a given server implementation will handle default data 👀. There are subtle differences between some protocol operations, and in those cases the server's default-handling behavior changes how the operation turns out 🫠.
1.1. Terminology 📖
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 🔥
- Data model schema: A document or set of documents describing the data models supported by the NETCONF server.
- Management application: A computer program running outside the NETCONF server that configures or supervises the NETCONF server. A management application can reach the device, e.g., via NETCONF, command line interface (CLI), or the Simple Network Management Protocol (SNMP). 🧚
- Schema default data: Data specified in the data model schema as default, that is, set or used by the device whenever the NETCONF client or other management application/user does not provide a specific value for the relevant data node. Schema default data may or may not be stored as part of a configuration datastore, depending on the basic mode used by a particular server.
- Default data: Conceptual data containing a default value. Default data is not kept in a datastore. Not all servers use the same criteria to decide if a data node is actually instantiated in a datastore. If a data node is not present in a datastore, and a schema default definition is in use by the server instead, then it is considered to be a default data node. 🌈
- Default value: A default value is a value for a data node instance that is conceptually in use by the server, when the data node instance does not exist. 🍓
- Explicitly set data: Data that is set to any value by a NETCONF client or other management application by the way of an explicit management operation, including any data model schema default value. Any value set by the NETCONF server that is not the schema defined default value is also considered explicitly set data. 💅
<with-defaults>retrieval: Refers to a protocol operation that includes the<with-default>parameter to control the handling of default data. ✨:with-defaults: The shorthand notation for the with-defaults capability identifier. 🦋
The following terms are defined in [RFC6241]:
- client
- datastore
- operation
- server
The following term is defined in [RFC6020]:
- data node
1.2. Default-Handling Behavior 🧁
The default-handling behavior used by a server impacts NETCONF protocol operations in two ways:
- Data retrieval: A server is normally allowed to exclude data nodes that it considers to contain the default value. The actual nodes omitted depend on the default-handling behavior used by the server. 👑
- Create and delete operations: The
<edit-config>'operation'attribute can be used to create and/or delete specific data nodes. These operations depend on whether or not the target node currently exists. The server's default-handling behavior determines whether or not the requested node currently exists in the configuration datastore. 🙈
1.3. Client Controlled Retrieval of Default Data 🫶
A networking device can have a huge number of default values 😭. Usually the default values are specifically defined with a reasonable value, documented, and well-known, so the management user doesn't need to deal with them. Because of that, it's really common for networking devices to suppress the output of parameters that have the default value 💀.
That said, there are use cases where a NETCONF client actually needs the default data from the server:
- The management application often needs a single, definitive, and complete set of configuration values that determine how the networking device works.
- Documentation about default values can be unreliable or unavailable.
- Some management applications might not have the capabilities to correctly parse and interpret formal data models.
- Human users might want to understand the received data without consulting the documentation.
In all of these cases, the NETCONF client needs a mechanism to retrieve default data from a NETCONF server 🔥.
This document defines a NETCONF protocol capability to identify the server's default-handling behavior, an XML [W3C.REC-xmlschema-0-20041028] attribute to identify default data, and a YANG module extension to the NETCONF protocol that lets the NETCONF client control whether default data is returned by the server 🌸💜
2. Default-Handling Basic Modes 💅
Okay bestie, not every server handles default data the same way, and this doc is totally fine with that 🫶 Instead of forcing everyone into one vibe, a server gets to advertise its default-handling style and the client adjusts. Clients are expected to be powerful enough to support all three of the server basic default-handling modes ✨
Servers report default data in different ways, so this doc defines three standard default-handling basic modes a server implementer can pick from:
report-alltrimexplicit
A server MUST select one of the three basic modes defined in this section for handling default data. No cap, this is the main rule 🔥
2.1. 'report-all' Basic Mode 🌈
A server using the 'report-all' basic mode doesn't consider any data node to be default data, even schema default data 🙈
2.1.1. 'report-all' Basic Mode Retrieval
When data is retrieved from a server using the 'report-all' basic mode, and the <with-defaults> parameter isn't present, all data nodes MUST be reported 💖
2.1.2. 'report-all' <with-defaults> Retrieval
If the 'report-all' basic mode is used by the server, then the server MUST support the <with-defaults> parameter with a value equal to 'report-all', as specified in Section 3.1.
2.1.3. 'report-all' <edit-config> and <copy-config> Behavior
The server MUST consider every data node to exist, even those containing a schema default value. A valid 'create' operation attribute for a data node that contains its schema default value MUST fail with a 'data-exists' error-tag. A valid 'delete' operation attribute for a data node that contains its schema default value MUST succeed, even though the data node is immediately replaced by the server with the default value 🦋
A server using 'report-all' has no concept of a default node, so the 'report-all-tagged' <with-defaults> retrieval mode is not relevant. There will never be any tagged nodes, since there are no nodes that are omitted in a basic-mode retrieval operation. If the 'default' attribute is present in any configuration data, the server MUST return an <rpc-error> response with an 'unknown-attribute' error-tag. Main character energy for the server, but the attribute is a no-go 💀
2.2. 'trim' Basic Mode 🍓
A server that uses the 'trim' basic mode MUST consider any data node set to its schema default value to be default data.
2.2.1. 'trim' Basic Mode Retrieval
When data is retrieved from a server using the 'trim' basic mode, and the <with-defaults> parameter isn't present, data nodes MUST NOT be reported if they contain the schema default value. Non-configuration data nodes containing the schema default value MUST NOT be reported.
2.2.2. 'trim' <with-defaults> Retrieval
If the 'trim' basic mode is used by the server, then the server MUST support the <with-defaults> parameter with a value equal to 'trim', as specified in Section 3.2.
2.2.3. 'trim' <edit-config> and <copy-config> Behavior
The server MUST consider any data node that does not contain its schema default value to exist. A valid 'create' operation attribute for a data node that has a schema default value defined MUST succeed. A valid 'delete' operation attribute for a missing data node that has a schema default value MUST fail. The server MUST return an <rpc-error> response with a 'data-missing' error-tag 🙃
If a client sets a data node to its schema default value, using any valid operation, it MUST succeed, although the data node MUST NOT be saved in the NETCONF configuration datastore. This has the same effect as removing the data node and treating it as default data. It's giving "vanish and still count" 🧚
If the server supports the 'report-all-tagged' value for the <with-defaults> parameter, then the 'default' attribute MUST be accepted in configuration input, as described in Section 4.5.1 and Section 4.5.2.
2.3. 'explicit' Basic Mode ⭐
A server that uses the 'explicit' basic mode MUST consider any data node that is not explicitly set data to be default data.
2.3.1. 'explicit' Basic Mode Retrieval
When data is retrieved from a server using the 'explicit' basic mode, and the <with-defaults> parameter isn't present, data nodes MUST be reported if explicitly set by the client, even if they contain the schema default value. Non-configuration data nodes containing the schema default value MUST be reported.
2.3.2. 'explicit' <with-defaults> Retrieval
If the 'explicit' basic mode is used by the server, the server MUST support the <with-defaults> parameter with a value equal to 'explicit', as specified in Section 3.3.
2.3.3. 'explicit' <edit-config> and <copy-config> Behavior
The server considers any data node that is explicitly set data to exist. A valid 'create' operation attribute for a data node that has been set by a client to its schema default value MUST fail with a 'data-exists' error-tag. A valid 'create' operation attribute for a data node that has been set by the server to its schema default value MUST succeed. A valid 'delete' operation attribute for a data node that has been set by a client to its schema default value MUST succeed. A valid 'delete' operation attribute for a data node that has been set by the server to its schema default value MUST fail with a 'data-missing' error-tag 👑
If the server supports the 'report-all-tagged' retrieval mode in its :with-defaults capability, then the 'default' attribute MUST be accepted in configuration input. If all NETCONF <edit-config> or <copy-config> parameters are valid, then the server will treat a tagged data node (i.e., the 'default' attribute set to 'true' or '1') as a request to return that node to default data. If this request is valid within the context of the requested NETCONF operation, then the data node is removed and returned to its default value. The data node within the NETCONF message MUST contain a value in this case, which MUST be equal to the schema default value. If not, the server MUST return an <rpc-error> response with an 'invalid-value' error-tag 🎀
3. Retrieval of Default Data ✨
This document defines a new parameter, called <with-defaults>, which can be added to specific NETCONF operation request messages to control how retrieval of default data is treated by the server 🦋
A server that implements this specification MUST accept the <with-defaults> parameter containing the enumeration for any of the default-handling modes it supports. The <with-defaults> parameter contains one of the four enumerations defined in this section.
3.1. 'report-all' Retrieval Mode 🌸
When data is retrieved with a <with-defaults> parameter equal to 'report-all', all data nodes MUST be reported, including any data nodes considered to be default data by the server.
3.2. 'trim' Retrieval Mode 🧚
When data is retrieved with a <with-defaults> parameter equal to 'trim', data nodes MUST NOT be reported if they contain the schema default value. Non-configuration data nodes containing the schema default value MUST NOT be reported.
3.3. 'explicit' Retrieval Mode 💜
When data is retrieved with a <with-defaults> parameter equal to 'explicit', a data node that was set by a client to its schema default value MUST be reported. A conceptual data node that would be set by the server to the schema default value MUST NOT be reported. Non-configuration data nodes containing the schema default value MUST be reported.
3.4. 'report-all-tagged' Retrieval Mode 🏷️
In addition to the basic modes, there's a special variant of the 'report-all' basic mode called 'report-all-tagged'. This mode MUST be supported on a server if the 'also-supported' parameter in the :with-defaults capability contains the 'report-all-tagged' option. Refer to Section 4 for encoding details for this capability.
In this mode the server returns all data nodes, just like the 'report-all' mode, except a data node that is considered by the server to contain default data will include an XML attribute to indicate this condition. This is so useful for an application to figure out which nodes the server considers default data, all within a single retrieval operation 🙌
A server that supports 'report-all-tagged' MUST also accept the 'default' XML attribute within configuration input to the <edit-config> or <copy-config> operations. Refer to Section 6 for XML encoding details of the 'default' XML attribute.
4. With-defaults Capability 🎀
4.1. Overview
The :with-defaults capability indicates which default-handling basic mode is supported by the server. It may also indicate support for additional defaults retrieval modes. These retrieval modes allow a NETCONF client to control whether default data is returned by the server. The capability affects both configuration and state data (while acknowledging that the usage of default values for state data is less prevalent). Sending of default data is controlled for each individual operation separately 🫶
A NETCONF server implementing the :with-defaults capability:
- MUST indicate its basic mode behavior by including the 'basic-mode' parameter in the capability URI, as defined in Section 4.3.
- MUST support the YANG module defined in Section 5 for the default-handling mode indicated by the 'basic-mode' parameter.
- SHOULD support the YANG module in Section 5 for the default-handling mode identified by the 'report-all' or 'report-all-tagged' enumeration value.
- If the 'report-all-tagged' default-handling mode is supported, then the 'default' attribute MUST be supported.
- MAY support the YANG module in Section 5 for additional default-handling modes.
4.2. Dependencies
None.
4.3. Capability Identifier 🔑
urn:ietf:params:netconf:capability:with-defaults:1.0The identifier MUST have a parameter: "basic-mode". This indicates how the server will treat default data, as defined in Section 2. The allowed values of this parameter are 'report-all', 'trim', and 'explicit', as defined in Section 2.
The identifier MAY have another parameter: "also-supported". This parameter indicates which additional enumeration values (besides the basic-mode enumeration) the server will accept for the <with-defaults> parameter in Section 5. The value of the parameter is a comma-separated list of one or more modes that are supported besides the mode indicated in the 'basic-mode' parameter. Possible modes are 'report-all', 'report-all-tagged', 'trim', and 'explicit', as defined in Section 3.
Note that this protocol capability URI is separate from the YANG module capability URI for the YANG module in Section 5. A server that implements this module MUST also advertise a YANG module capability URI according to the rules specified in [RFC6020].
Examples:
urn:ietf:params:netconf:capability:with-defaults:1.0?basic-
mode=explicit
urn:ietf:params:netconf:capability:with-defaults:1.0?basic-
mode=explicit&also-supported=report-all,report-all-tagged4.4. New Operations
None.
4.5. Modifications to Existing Operations
4.5.1. <get>, <get-config>, and <copy-config> Operations 💖
okay so, a brand-new <with-defaults> XML element gets added to the input for the <get>, <get-config>, and <copy-config> operations 🎀. If it's there, it controls how default data gets reported. The server MUST return default data in the NETCONF <rpc-reply> messages according to that value, but only if the server supports the requested retrieval mode ✨.
This parameter only steers these specific retrieval operations. It doesn't touch any other operations or how configuration data gets stored non-volatilely 🌸.
The <with-defaults> element lives in the XML namespace for the ietf-netconf-with-defaults.yang module (Section 5), NOT in the XML namespace for the <get>, <get-config>, and <copy-config> operations 💅.
Allowed values for with-defaults come from the 'with-defaults-type' typedef in Section 5. A specific server can only use the values it advertises in its :with-defaults capability, under the 'basic-mode' and 'also-supported' parameters 🦋.
If someone sends an unsupported value, the NETCONF server MUST return an <rpc-error> response with an 'invalid-value' error-tag 😭.
If the <with-defaults> element isn't present, the server MUST follow its basic mode behavior, as set by the :with-defaults capability identifier's 'basic-mode' parameter (defined in Section 4.3) 🧚.
The <get> and <get-config> operations also have a separate filtering mechanism, the <filter> parameter 🍓. The defaults filtering happens conceptually before <filter> gets processed. For example, if <with-defaults> is 'report-all', then <filter> is conceptually applied to all data nodes and all default data. Main character energy 👑.
The <copy-config> operation is only affected by <with-defaults> if its target is specified with the <url> parameter 🌈. If the target is a NETCONF configuration datastore (running, candidate, or startup), <with-defaults> has no effect at all 🙈. The server MUST use its basic mode when copying data to a NETCONF configuration datastore. And if <with-defaults> shows up in that case, it MUST be silently ignored by the server 🤫.
If the server supports the 'report-all-tagged' mode, then the 'default' attribute from Section 6 also impacts <copy-config> ✨. When 'default' is present and set to 'true' or '1', the server MUST treat the new data node as a request to return that node to its default value (aka remove it from the configuration datastore). The data node in the NETCONF message MUST contain a value in this case, and that value MUST be equal to the schema default value. If not, the server MUST return an <rpc-error> response with an 'invalid-value' error-tag 💀.
4.5.2. <edit-config> Operation 🦋
The <edit-config> operation has several editing modes 🌸. Only the 'create' and 'delete' editing operations are affected by the default-handling basic mode. The other enumeration values for the NETCONF operation attribute are NOT affected 🎀.
If the operation attribute is 'create', and the data node already exists in the target configuration datastore, the server MUST return an <rpc-error> response with an 'invalid-value' error-tag 😭.
If the client sets a data node to its schema default value, the server MUST accept the request if it's valid. The server MUST keep or discard the new value based on its default-handling basic mode. For the 'trim' basic mode, all schema default values get discarded. Otherwise, a client-provided schema default value is saved in a NETCONF configuration datastore 💅.
If the server supports the 'report-all-tagged' mode, then the 'default' attribute from Section 6 also impacts <edit-config> 🫶. When 'default' is present and set to 'true' or '1', the server MUST treat the new data node as a request to return that node to its default value (aka remove it from the configuration datastore). The data node in the NETCONF message MUST contain a value in this case, which MUST be equal to the schema default value. If not, the server MUST return an <rpc-error> response with an 'invalid-value' error-tag 🔥.
If the 'default' attribute is present, then the effective operation for the target data node MUST be 'create', 'merge', or 'replace'. If not, the server MUST return an <rpc-error> response with an 'invalid-value' error-tag 😭. For example, if 'create' is the effective operation, then the create request has to be valid on its own (e.g., the current data node MUST NOT exist) 🙈. The procedure for figuring out the effective operation is defined in [RFC6241]. It's derived from the 'default-operation' parameter and/or any operation attributes present in the data node or any of its ancestor nodes, within the <edit-config> request 🧚.
4.5.3. Other Operations 🍓
Other operations that return configuration data SHOULD also handle default data according to the rules in this document, and they SHOULD explicitly state that in their documentation 🌈. If the document defining a given operation doesn't specify this, then the default-handling rules described here do NOT affect that operation 🤷♀️.
4.6. Interactions with Other Capabilities 🌸
None. Nothing to see here, bestie 🫶
5. YANG Module for the <with-defaults> Parameter ✨
The following YANG module adds the with-defaults element to the <get>, <get-config>, and <copy-config> operations 👑. The YANG language is defined in [RFC6020], and the above operations are defined in YANG in [RFC6241]. Every NETCONF server that supports the :with-defaults capability MUST implement this YANG module 💜.
<CODE BEGINS> file="ietf-netconf-with-defaults@2011-06-01.yang"
module ietf-netconf-with-defaults {
namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults";
prefix ncwd;
import ietf-netconf { prefix nc; }
organization
"IETF NETCONF (Network Configuration Protocol) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <netconf@ietf.org>
WG Chair: Bert Wijnen
<bertietf@bwijnen.net>
WG Chair: Mehmet Ersue
<mehmet.ersue@nsn.com>
Editor: Andy Bierman
<andy.bierman@brocade.com>
Editor: Balazs Lengyel
<balazs.lengyel@ericsson.com>";
description
"This module defines an extension to the NETCONF protocol
that allows the NETCONF client to control how default
values are handled by the server in particular NETCONF
operations.
Copyright (c) 2011 IETF Trust and the persons identified as
the document authors. 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 6243; see
the RFC itself for full legal notices.";
revision 2011-06-01 {
description
"Initial version.";
reference
"RFC 6243: With-defaults Capability for NETCONF";
}
typedef with-defaults-mode {
description
"Possible modes to report default data.";
reference
"RFC 6243; Section 3.";
type enumeration {
enum report-all {
description
"All default data is reported.";
reference
"RFC 6243; Section 3.1";
}
enum report-all-tagged {
description
"All default data is reported.
Any nodes considered to be default data
will contain a 'default' XML attribute,
set to 'true' or '1'.";
reference
"RFC 6243; Section 3.4";
}
enum trim {
description
"Values are not reported if they contain the default.";
reference
"RFC 6243; Section 3.2";
}
enum explicit {
description
"Report values that contain the definition of
explicitly set data.";
reference
"RFC 6243; Section 3.3";
}
}
}
grouping with-defaults-parameters {
description
"Contains the <with-defaults> parameter for control
of defaults in NETCONF retrieval operations.";
leaf with-defaults {
description
"The explicit defaults processing mode requested.";
reference
"RFC 6243; Section 4.5.1";
type with-defaults-mode;
}
}
// extending the get-config operation
augment /nc:get-config/nc:input {
description
"Adds the <with-defaults> parameter to the
input of the NETCONF <get-config> operation.";
reference
"RFC 6243; Section 4.5.1";
uses with-defaults-parameters;
}
// extending the get operation
augment /nc:get/nc:input {
description
"Adds the <with-defaults> parameter to
the input of the NETCONF <get> operation.";
reference
"RFC 6243; Section 4.5.1";
uses with-defaults-parameters;
}
// extending the copy-config operation
augment /nc:copy-config/nc:input {
description
"Adds the <with-defaults> parameter to
the input of the NETCONF <copy-config> operation.";
reference
"RFC 6243; Section 4.5.1";
uses with-defaults-parameters;
}
}
<CODE ENDS>6. XSD for the 'default' Attribute 🎀
The following XML Schema document [W3C.REC-xml-20081126] defines the 'default' attribute described in this document 💖. This XSD only matters if the server supports the 'report-all-tagged' defaults retrieval mode 🌈.
The 'default' attribute uses the XSD data type 'boolean' ✨. Per Section 3.2.2.1 of XML Schema Part 2: Datatypes, the allowable lexical representations for the xs:boolean datatype are the strings "0" and "false" for false, and the strings "1" and "true" for true. Implementations MUST support both styles of lexical representation 🫶.
<CODE BEGINS> file="defaults.xsd"
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns="urn:ietf:params:xml:ns:netconf:default:1.0"
targetNamespace="urn:ietf:params:xml:ns:netconf:default:1.0"
elementFormDefault="qualified"
attributeFormDefault="unqualified"
xml:lang="en">
<xs:annotation>
<xs:documentation>
This schema defines the syntax for the 'default' attribute
described within this document.
</xs:documentation>
</xs:annotation>
<!--
default attribute
-->
<xs:attribute name="default" type="xs:boolean" default="false">
<xs:annotation>
<xs:documentation>
This attribute indicates whether the data node represented
by the XML element containing this attribute is considered
by the server to be default data. If set to 'true' or '1', then
the data node is default data. If 'false' or '0', then the
data node is not default data.
</xs:documentation>
</xs:annotation>
</xs:attribute>
</xs:schema>
<CODE ENDS>7. IANA Considerations 🎀
Okay bestie, IANA gets some new stuff from this doc 💅 First, it registers one capability identifier URN in the 'Network Configuration Protocol (NETCONF) Capability URNs' registry:
urn:ietf:params:netconf:capability:with-defaults:1.0
It also registers two XML namespace URNs in the 'IETF XML registry', following the format defined in [RFC3688]:
- URI:
urn:ietf:params:xml:ns:netconf:default:1.0 - URI:
urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults
The registrant contact is The NETCONF WG of the IETF 🫶
XML: N/A, the requested URIs are XML namespaces.
Last one: this doc registers one module name in the 'YANG Module Names' registry, defined in [RFC6020] . Here's the info:
- name:
ietf-netconf-with-defaults - prefix:
ncwd - namespace:
urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults - RFC: 6243
8. Security Considerations 🔥
Okay, this part is lowkey the best news 😭 This document is an extension to the existing NETCONF protocol operations, and it does not bring any new or increased security risks into the management system. Zero drama ✨
The with-defaults capability gives clients control over how default data is retrieved from a NETCONF datastore. That's a lot of power, so the security considerations of [RFC6241] apply to this document too. Read those, periodt 🙈
9. Acknowledgements 🧚
Huge thanks to Martin Bjorklund, Sharon Chisholm, Phil Shafer, Juergen Schoenwaelder, Kent Watsen, Washam Fan, and the whole NETCONF WG crew 💜 They gave really important input to this doc, and we're all obsessed with them 🌸
10. Normative References 📚
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004.
[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.
[W3C.REC-xml-20081126] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth Edition)", World Wide Web Consortium Recommendation REC-xml-20081126, November 2008, <http://www.w3.org/TR/2008/REC-xml-20081126>.
[W3C.REC-xmlschema-0-20041028] Fallside, D. and P. Walmsley, "XML Schema Part 0: Primer Second Edition", World Wide Web Consortium Recommendation REC-xmlschema-0-20041028, October 2004, <http://www.w3.org/TR/2004/REC-xmlschema-0-20041028>.
Appendix A. Usage Examples 🌈
A.1. Example YANG Module
The following YANG module defines an example interfaces table to show how the <with-defaults> parameter behaves for a specific data model ✨
Note that this is not a real module, and implementation of this module is not required for conformance to the :with-defaults capability, defined in Section 4. This module is not to be registered with IANA, and is not considered to be a code component. It is intentionally very terse, and includes few descriptive statements 🙈
module example {
namespace "http://example.com/ns/interfaces";
prefix exam;
typedef status-type {
description "Interface status";
type enumeration {
enum ok;
enum 'waking up';
enum 'not feeling so good';
enum 'better check it out';
enum 'better call for help';
}
default ok;
}
container interfaces {
description "Example interfaces group";
list interface {
description "Example interface entry";
key name;
leaf name {
description
"The administrative name of the interface.
This is an identifier that is only unique
within the scope of this list, and only
within a specific server.";
type string {
length "1 .. max";
}
}
leaf mtu {
description
"The maximum transmission unit (MTU) value assigned to
this interface.";
type uint32;
default 1500;
}
leaf status {
description
"The current status of this interface.";
type status-type;
config false;
}
}
}
}A.2. Example Data Set
The following data element shows the conceptual contents of the example server for the protocol operation examples in the next section. This includes all the configuration data nodes, non-configuration data nodes, and default leafs 🍓
<data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<interfaces xmlns="http://example.com/ns/interfaces">
<interface>
<name>eth0</name>
<mtu>8192</mtu>
<status>up</status>
</interface>
<interface>
<name>eth1</name>
<mtu>1500</mtu>
<status>up</status>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<status>not feeling so good</status>
</interface>
<interface>
<name>eth3</name>
<mtu>1500</mtu>
<status>waking up</status>
</interface>
</interfaces>
</data>In this example, the 'mtu' field for each interface entry is set in the following manner 👀
+--------------+--------------+--------------+
| name | set by | mtu |
+--------------+--------------+--------------+
| eth0 | client | 8192 |
| eth1 | server | 1500 |
| eth2 | client | 9000 |
| eth3 | client | 1500 |
+--------------+--------------+--------------+A.3. Protocol Operation Examples
The following examples show some <get> operations using the 'with-defaults' element. The data model used for these examples is defined in Appendix A.1 💖
The client is retrieving all the data nodes within the 'interfaces' object, filtered with the <with-defaults> parameter.
A.3.1. <with-defaults> = 'report-all'
The behavior of the <with-defaults> parameter handling for the value 'report-all' is demonstrated in this example 🦋
<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<get>
<filter type="subtree">
<interfaces xmlns="http://example.com/ns/interfaces"/>
</filter>
<with-defaults
xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults">
report-all
</with-defaults>
</get>
</rpc>
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<data>
<interfaces xmlns="http://example.com/ns/interfaces">
<interface>
<name>eth0</name>
<mtu>8192</mtu>
<status>up</status>
</interface>
<interface>
<name>eth1</name>
<mtu>1500</mtu>
<status>up</status>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<status>not feeling so good</status>
</interface>
<interface>
<name>eth3</name>
<mtu>1500</mtu>
<status>waking up</status>
</interface>
</interfaces>
</data>
</rpc-reply>A.3.2. <with-defaults> = 'report-all-tagged'
The behavior of the <with-defaults> parameter handling for the value 'report-all-tagged' is demonstrated in this example. A 'tagged' data node is an element that contains the 'default' XML attribute, set to 'true' or '1' 🏷️
The actual data nodes tagged by the server depend on the default-handling basic mode used by the server. Only the data nodes that are considered to be default data will be tagged 💅
In this example, the server's basic mode is equal to 'trim', so all data nodes that would contain the schema default value are tagged. If the server's basic mode is 'explicit', then only data nodes that are not explicitly set data are tagged. If the server's basic mode is 'report-all', then no data nodes are tagged 🤯
<rpc message-id="102"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<get>
<filter type="subtree">
<interfaces xmlns="http://example.com/ns/interfaces"/>
</filter>
<with-defaults
xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults">
report-all-tagged
</with-defaults>
</get>
</rpc>
<rpc-reply message-id="102"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:wd="urn:ietf:params:xml:ns:netconf:default:1.0">
<data>
<interfaces xmlns="http://example.com/ns/interfaces">
<interface>
<name>eth0</name>
<mtu>8192</mtu>
<status wd:default="true">up</status>
</interface>
<interface>
<name>eth1</name>
<mtu wd:default="true">1500</mtu>
<status wd:default="true">up</status>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<status>not feeling so good</status>
</interface>
<interface>
<name>eth3</name>
<mtu wd:default="true">1500</mtu>
<status>waking up</status>
</interface>
</interfaces>
</data>
</rpc-reply>A.3.3. <with-defaults> = 'trim'
The behavior of the <with-defaults> parameter handling for the value 'trim' is demonstrated in this example 🎀
<rpc message-id="103"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<get>
<filter type="subtree">
<interfaces xmlns="http://example.com/ns/interfaces"/>
</filter>
<with-defaults
xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults">
trim
</with-defaults>
</get>
</rpc>
<rpc-reply message-id="103"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<data>
<interfaces xmlns="http://example.com/ns/interfaces">
<interface>
<name>eth0</name>
<mtu>8192</mtu>
</interface>
<interface>
<name>eth1</name>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<status>not feeling so good</status>
</interface>
<interface>
<name>eth3</name>
<status>waking up</status>
</interface>
</interfaces>
</data>
</rpc-reply>A.3.4. <with-defaults> = 'explicit' ✨
okay so this is the 'explicit' example and it's giving clean, simple vibes 🎀 it shows how the <with-defaults> parameter behaves when its value is 'explicit'. 🦋
Here's the request. The client sends an rpc with message-id 104 that asks for an interfaces subtree filter, and it sets <with-defaults> to explicit 💅
<rpc message-id="104"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<get>
<filter type="subtree">
<interfaces xmlns="http://example.com/ns/interfaces"/>
</filter>
<with-defaults
xmlns="urn:ietf:params:yang:ietf-netconf-with-defaults">
explicit
</with-defaults>
</get>
</rpc>Wait, I have to be careful here, bestie 🙈 The namespace on that <with-defaults> element is actually urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults, so let me copy it exactly as the RFC has it:
<rpc message-id="104"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<get>
<filter type="subtree">
<interfaces xmlns="http://example.com/ns/interfaces"/>
</filter>
<with-defaults
xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults">
explicit
</with-defaults>
</get>
</rpc>Now the reply, which is the fun part 🧚 It comes back with message-id 104 and a data block holding four interfaces. Look at how they show up:
<rpc-reply message-id="104"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<data>
<interfaces xmlns="http://example.com/ns/interfaces">
<interface>
<name>eth0</name>
<mtu>8192</mtu>
<status>up</status>
</interface>
<interface>
<name>eth1</name>
<status>up</status>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<status>not feeling so good</status>
</interface>
<interface>
<name>eth3</name>
<mtu>1500</mtu>
<status>waking up</status>
</interface>
</interfaces>
</data>
</rpc-reply>eth1 is the one to watch 👀 It has its name and status, but no mtu element at all, while the other three each carry their own mtu value. The status for eth2 is "not feeling so good" and eth3 is "waking up" 😭🫶 Honestly the whole thing is so relatable.
Authors' Addresses 💜
Andy Bierman Brocade
EMail: andy.bierman@brocade.com
Balazs Lengyel Ericsson Budapest, Hungary
EMail: balazs.lengyel@ericsson.com
📦 where this page comes from
- ietf: rfc6243 2011-06
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms