NETCONF A. Bierman
Internet-Draft InterWorking Labs
Intended status: Standards Track B. Lengyel
Expires: November 21, 2010 Ericsson
May 20, 2010
With-defaults capability for NETCONF
draft-ietf-netconf-with-defaults-08
Abstract
The NETCONF protocol defines ways to read and edit configuration data
from a NETCONF server. Part of this data may not be set by the
NETCONF client, but rather a default value is used. In many
situations the NETCONF client has a priori knowledge about default
data, so the NETCONF server does not need to save it in a NETCONF
datastore or send it to the client in a retrieval operation reply.
In other situations the NETCONF client will need this data as part of
the NETCONF <rpc-reply> messages. Not all server implementations
treat this default data the same way. This document defines a
capability-based extension to the NETCONF protocol that allows the
NETCONF client to identify how defaults are handled by the server,
and control whether default values are part of NETCONF <rpc-reply>
messages or <copy-config> output to a file.
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
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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 November 21, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Defaults Handling Behavior . . . . . . . . . . . . . . . . 5
1.3. Client Controlled Retrieval of Default Data . . . . . . . 5
2. Defaults 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> Behavior . . . . . . . . . 6
2.1.4. 'report-all' Non-volatile Storage Behavior . . . . . . 7
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> Behavior . . . . . . . . . . . . 7
2.2.4. 'trim' Non-volatile Storage Behavior . . . . . . . . . 8
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> Behavior . . . . . . . . . . 8
2.3.4. 'explicit' Non-volatile Storage Behavior . . . . . . . 9
3. Retrieval of Default Data . . . . . . . . . . . . . . . . . . 9
3.1. 'report-all-tagged' Retrieval Mode . . . . . . . . . . . . 9
4. With-defaults Capability . . . . . . . . . . . . . . . . . . . 10
4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Dependencies . . . . . . . . . . . . . . . . . . . . . . . 10
4.3. Conformance . . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Capability Identifier . . . . . . . . . . . . . . . . . . 10
4.5. New Operations . . . . . . . . . . . . . . . . . . . . . . 11
4.6. Modifications to Existing Operations . . . . . . . . . . . 11
4.6.1. <get>, <get-config>, and <copy-config> Operations . . 11
4.6.2. <edit-config> Operation . . . . . . . . . . . . . . . 12
4.6.3. Other Operations . . . . . . . . . . . . . . . . . . . 12
4.7. Interactions with Other Capabilities . . . . . . . . . . . 13
5. YANG Module for the <with-defaults> Parameter . . . . . . . . 13
6. XSD for the 'wd:default' Attribute . . . . . . . . . . . . . . 15
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7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
10. Normative References . . . . . . . . . . . . . . . . . . . . . 17
Appendix A. Usage Examples . . . . . . . . . . . . . . . . . . . 18
A.1. Example YANG Module . . . . . . . . . . . . . . . . . . . 18
A.2. Example Data Set . . . . . . . . . . . . . . . . . . . . . 20
A.3. Protocol Operation Examples . . . . . . . . . . . . . . . 21
A.3.1. <with-defaults> = 'report-all' . . . . . . . . . . . . 21
A.3.2. <with-defaults> = 'report-all-tagged' . . . . . . . . 22
A.3.3. <with-defaults> = 'trim' . . . . . . . . . . . . . . . 25
A.3.4. <with-defaults> = 'explicit' . . . . . . . . . . . . . 26
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 27
B.1. 07-08 . . . . . . . . . . . . . . . . . . . . . . . . . . 27
B.2. 06-07 . . . . . . . . . . . . . . . . . . . . . . . . . . 27
B.3. 05-06 . . . . . . . . . . . . . . . . . . . . . . . . . . 27
B.4. 04-05 . . . . . . . . . . . . . . . . . . . . . . . . . . 28
B.5. 03-04 . . . . . . . . . . . . . . . . . . . . . . . . . . 28
B.6. 02-03 . . . . . . . . . . . . . . . . . . . . . . . . . . 28
B.7. 01-02 . . . . . . . . . . . . . . . . . . . . . . . . . . 29
B.8. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 29
B.9. -00 . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
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1. Introduction
The NETCONF protocol [RFC4741] defines ways to read configuration and
state data from a NETCONF server. Part of the configuration data may
not be set by the NETCONF client, but rather by a default value from
the data model. In many situations the NETCONF client has a priori
knowledge about default data, so the NETCONF server does not need to
send it to the client. A priori knowledge can be e.g., a document
formally describing the data models supported by the NETCONF server.
It can be important for a client to know exactly how a server
implementation will handle default data. There are subtle
differences in some protocol operations where the defaults handling
behavior of the server will affect the outcome of the operation.
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,
CLI or 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 item. 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: Data considered by a particular server to contain a
default value. Default data is not kept in a configuration
datastore.
Explicitly set data: Data that is set to any value by a NETCONF
client or other management application by the way of an actual
management operation, including any data model schema default
value. Any value set by the NETCONF server which is not the
schema defined default value is also considered explicitly set
data.
The following terms are defined in [RFC4741]:
o client
o datastore
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o operation
o server
The following term is defined in [I-D.ietf-netmod-yang]:
o data node
1.2. Defaults Handling Behavior
The defaults handling behavior used by a server will impact NETCONF
protocol operations in three ways:
1. Data retrieval: A server is normally allowed to exclude data
nodes which it considers to contain the default value. The
actual nodes omitted depends on the defaults handling behavior
used by the server. The nodes that are returned in this case are
the only nodes the server considers to exist in the datastore.
2. 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 the target node
currently exists or not. The server's defaults handling behavior
will determine whether the requested node currently exists in the
datastore or not.
3. NV Storage: The server's defaults handling behavior will affect
which data nodes are saved in non-volatile storage.
1.3. Client Controlled Retrieval of Default Data
A networking device may have a large number of default values. Often
the default values are not interesting or specifically defined with a
"reasonable" value, so that the management user does not have to
handle them. For these reasons it is quite common for networking
devices to suppress the output of parameters having the default
value.
However, there are use-cases when a NETCONF client will need the
default data from the server:
o The management application often needs a single, definitive and
complete set of configuration values that determine how the a
networking device works.
o Documentation about default values can be unreliable or
unavailable.
o Some management applications might not have the capabilities to
correctly parse and interpret formal data models.
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o Human users might want to understand the received data without
consultation of the documentation.
In all these cases the NETCONF client will need default data as part
of the NETCONF <rpc-reply> messages.
This document defines a NETCONF protocol capability to identify the
server defaults handling behavior, and a YANG module extension to the
NETCONF protocol that allows the NETCONF client to control whether
default data is returned in certain NETCONF <rpc-reply> messages.
2. Defaults Handling Basic Modes
Not all server implementations treat default data in the same way.
Instead of forcing a single implementation strategy, this document
allows a server to advertise a particular style of defaults handling,
and the client can adjust accordingly.
NETCONF servers report default data in different ways. This document
specifies three standard defaults handling basic modes that a server
implementor may choose from:
o report-all
o trim
o explicit
A server MUST select one of the three basic modes defined in this
section for handling default data.
2.1. 'report-all' Basic Mode
A server which uses the 'report-all' basic mode does not consider any
data node to be default data.
2.1.1. 'report-all' Basic Mode Retrieval
All data nodes MUST be reported.
2.1.2. 'report-all' <with-defaults> Retrieval
All data nodes MUST be reported, including any data nodes considered
to be default data by the server.
2.1.3. 'report-all' <edit-config> Behavior
The server MUST consider every data node to exist, even those
represented by a schema default value.
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o A valid 'create' operation for a data node that contains its
schema default value MUST fail with a 'data-exists' error-tag.
o A valid 'delete' operation 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.
2.1.4. 'report-all' Non-volatile Storage Behavior
All data nodes MUST be saved in non-volatile storage.
2.2. 'trim' Basic Mode
A server which 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
Data nodes MUST NOT be reported if they match the schema default
value. Non-configuration data nodes containing the schema default
value MUST NOT be reported.
2.2.2. 'trim' <with-defaults> Retrieval
Data nodes MUST NOT be reported if they match the schema default
value. Non-configuration data nodes containing the schema default
value MUST NOT be reported.
2.2.3. 'trim' <edit-config> Behavior
The server MUST consider any data node that does not contain its
schema default value to exist.
o A valid 'create' operation for a data node that has a schema
default value defined MUST succeed.
o A valid 'delete' operation for a missing data node that has a
schema default value MUST fail with a 'data-missing' error-tag.
o 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 datastore. This has the same affect
as removing the data node and treating it as default data.
If the server supports the 'report-all-tagged' retrieval mode in its
with-defaults capability, then the 'wd:default' attribute MUST be
accepted in configuration input. If all NETCONF sub-operation
parameters are valid, then the server will treat a tagged data node
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. If the data
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node within the NETCONF message contains a value in this case, it
MUST be equal to the schema default value.
2.2.4. 'trim' Non-volatile Storage Behavior
All data nodes, except those set to their schema default value, MUST
be saved in non-volatile storage.
2.3. 'explicit' Basic Mode
A server which 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
If a client set a data node to its schema default value, it MUST
always be reported. If the server set a data node to its schema
default value, it MUST NOT be reported. Non-configuration data nodes
containing the schema default value MUST be reported.
2.3.2. 'explicit' <with-defaults> Retrieval
If a client set a data node to its schema default value, it MUST be
reported. If the server set a data node to its schema default value,
it MUST NOT be reported. Non-configuration data nodes containing the
schema default value MUST be reported.
2.3.3. 'explicit' <edit-config> Behavior
The server considers any data node that is explicitly set data to
exist.
o A valid 'create' operation for a data node that has been set by a
client to its schema default value MUST fail with a 'data-exists'
error-tag.
o A valid 'create' operation for a data node that has been set by
the server to its schema default value MUST succeed.
o A valid 'delete' operation for a data node that has been set by a
client to its schema default value MUST succeed.
o A valid 'delete' operation 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 'wd:default' attribute MUST be
accepted in configuration input. If all NETCONF sub-operation
parameters are valid, then the server will treat a tagged data node
as a request to return that node to default data. If this request is
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valid within the context of the requested NETCONF operation, then the
data node is removed and returned to its default value. If the data
node within the NETCONF message contains a value in this case, it
MUST be equal to the schema default value.
2.3.4. 'explicit' Non-volatile Storage Behavior
All data nodes that are explicitly set data MUST be saved in non-
volatile storage.
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.
The server MUST accept the <with-defaults> parameter containing the
enumeration for any of the defaults handling modes it supports, as
defined in Section 5.
The <with-defaults> parameter contains one of the three basic mode
enumerations defined above, to request that the retrieval operation
be performed using the specified defaults handling basic mode.
3.1. 'report-all-tagged' Retrieval Mode
In addition to the basic modes, a special variant of 'report-all'
basic mode is available 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 useful for an application to
determine which nodes are considered to contain default data by the
server, within a single retrieval operation.
A server which supports 'report-all-tagged' MUST also accept the 'wd:
default' XML attribute it is present within configuration input to
the <edit-config> or <copy-config> operations. Refer to Section 6
for XML encoding details of the 'wd:default' XML attribute.
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4. With-defaults Capability
4.1. Overview
The :with-defaults capability indicates that the NETCONF server
supports a specific defaults handling basic mode. It may also
indicate support for additional defaults retrieval modes. These
retrieval modes allow a NETCONF client to control whether default
data is part of NETCONF <rpc-reply> messages. 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:
o MUST indicate its basic mode behavior by including the 'basic-
mode' parameter in the capability URI, as defined in Section 4.4.
o MUST support the YANG module defined in Section 5.
o SHOULD support the 'report-all' or 'report-all-tagged' defaults
handling mode.
o MAY support additional defaults handling modes.
4.2. Dependencies
None
4.3. Conformance
Every NETCONF server SHOULD implement this capability.
4.4. Capability Identifier
urn:ietf:params:netconf:capability:with-defaults:1.0
The 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 default handling modes the
server supports. The value of the parameter is a comma separated
list of one or more modes that are supported beside the mode
indicated in the 'basic-mode' parameter. Possible modes are 'report-
all', 'report-all-tagged', 'trim', and 'explicit', as defined in
Section 5.
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Note that this protocol capability URI is separate from the YANG
module capability URI for the YANG module in Section 5. A server
which implements this module MUST also advertise a YANG module
capability URI according to the rules specified in
[I-D.ietf-netmod-yang].
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-tagged
4.5. New Operations
None
4.6. Modifications to Existing Operations
4.6.1. <get>, <get-config>, and <copy-config> Operations
A new <with-defaults> XML element is added to the input for the
<get>, <get-config> and <copy-config> operations. If the <with-
defaults> element is present, it controls the reporting of default
data. The server MUST return default data in the NETCONF <rpc-reply>
messages according to the value of this element, if the server
supports the specified retrieval mode.
This parameter only controls these specified retrieval operations,
and does not impact any other operations or the non-volatile storage
of configuration data.
The <with-defaults> element is defined in the XML namespace for the
ietf-netconf-with-defaults.yang module in Section 5, not the XML
namespace for the <get>, <get-config> and <copy-config> operations.
Allowed values of the with-defaults element are taken from the list
in Section 2. The allowed values are restricted to the values that
the device indicates it supports within the with-defaults capability,
in the 'basic-mode' and 'also-supported' parameters.
If an unsupported value is used, the NETCONF server MUST return an
<rpc-reply> with an <rpc-error> element. The <error-tag> SHOULD be
'invalid-value', and the <error-app-tag> SHOULD be 'with-defaults-
mode-not-supported'.
If the <with-defaults> element is not present, the server MUST follow
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its basic mode behavior as indicated by the with-defaults capability
identifier's 'basic-mode' parameter, defined in Section 4.4.
The <copy-config> operation is only affected if the target of the
operation is specified with the <url> parameter. If the target is a
NETCONF datastore (i.e., running, candidate or startup), the
capability has no effect. The server MUST use its basic mode when
copying data to a NETCONF datastore. If the with-defaults parameter
is present in this case, it MUST be silently ignored by the server.
4.6.2. <edit-config> Operation
The <edit-config> operation has four sub-operations. The 'create'
and 'delete' sub-operations are affected by the defaults handling
basic mode.
The 'create' sub-operation MUST fail with a 'data-exists' error-tag
value if the server considers the target data node to already have a
current value.
If the client sets a data node to its schema default value, the
server MUST accept the request if it is valid. The server MUST keep
or discard the new value based on its defaults handling basic mode.
For the 'trim' basic mode, all schema default values are discarded,
otherwise a client-provided schema default value is saved in a
NETCONF datastore.
If the server supports the 'report-all-tagged' mode, then the 'wd:
default' attribute defined in Section 6 also impacts the edit-config
operation. If the wd:default attribute is present and set to 'true',
then the server MUST treat the new data node as a request to return
that node to its default value (i.e., remove it from the database).
If this editing mode is used, then the effective sub-operation for
the target data node MUST be 'create', 'merge' or 'replace'. If
'create' is the effective sub-operation, then the create request must
be valid on its own (e.g., current data node MUST NOT exist). The
procedure for determining the effective sub-operation is defined in
[I-D.ietf-netconf-4741bis]. It is derived from the 'default-
operation' parameter and/or any 'nc:operation' attribute that are
present in the data node or any of its ancestor nodes, within the
<edit-config> request message.
4.6.3. Other Operations
Other operations that return configuration data SHOULD also handle
default data according to the rules set in this document, and
explicitly state this in their documentation. If this is not
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specified in the document defining the respective operation, the
default handling rules described herein do not affect these
operations.
4.7. Interactions with Other Capabilities
None
5. YANG Module for the <with-defaults> Parameter
The following YANG module defines the addition of the with-defaults
element to the <get>, <get-config> and <copy-config> operations. The
YANG language is defined in [I-D.ietf-netmod-yang]. The above
operations are defined in YANG in [I-D.ietf-netconf-4741bis]. Every
NETCONF server which supports the :with-defaults capability MUST
implement this YANG module.
<CODE BEGINS> file="ietf-netconf-with-defaults@2010-05-19.yang"
module ietf-netconf-with-defaults {
namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults";
prefix nwd;
import ietf-netconf { prefix nc; }
organization
"IETF NETCONF (Network Configuration Protocol) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
WG Chair: Bert Wijnen
<mailto:bertietf@bwijnen.net>
WG Chair: Mehmet Ersue
<mailto:mehmet.ersue@nsn.com>
Editor: Andy Bierman
<mailto:andyb@iwl.com>
Editor: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>";
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description
"This module defines a capability-based extension to the
NETCONF protocol that allows the NETCONF client to control
whether default values are part of NETCONF
<rpc-reply> messages or <copy-config> output to the target URL.
Copyright (c) 2010 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 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-ietf-netmod-with-defaults-08.txt
revision 2010-05-19 {
description
"Initial version.";
reference
"RFC XXXX: With-defaults capability for NETCONF";
}
// RFC Ed.: replace XXXX with actual RFC number and remove this note
typedef with-defaults-mode {
description
"Possible modes to report default data in
rpc-reply messages.";
type enumeration {
enum report-all {
description
"All default data is reported.";
}
enum report-all-tagged {
description
"All default data is reported.
Any nodes considered to be default data
will contain a 'wd:default' XML attribute,
set to 'true'.";
}
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enum trim {
description
"Values are not reported if they match the default.";
}
enum explicit {
description
"Report values that match the definition of
explicitly set data.";
}
}
}
grouping with-defaults-parameters {
leaf with-defaults {
description
"The explicit defaults processing mode requested.";
type with-defaults-mode;
}
}
// extending the get-config operation
augment /nc:get-config/nc:input {
uses with-defaults-parameters;
}
// extending the get operation
augment /nc:get/nc:input {
uses with-defaults-parameters;
}
// extending the copy-config operation
augment /nc:copy-config/nc:input {
uses with-defaults-parameters;
}
}
<CODE ENDS>
6. XSD for the 'wd:default' Attribute
The following XML Schema document defines the 'default' attribute,
described within this document. This XSD is only relevant if the
server supports the 'report-all-tagged' defaults retrieval mode.
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<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"
form="qualified"
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' then
the data node is default data. If 'false', then the
data node is not default data.
</xs:documentation>
</xs:annotation>
</xs:attribute>
</xs:schema>
<CODE ENDS>
7. IANA Considerations
This document registers the following capability identifier URN in
the 'Network Configuration Protocol Capability URNs registry':
urn:ietf:params:netconf:capability:with-defaults:1.0
Note that the capability URN is compliant to [RFC4741] section 10.3.
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This document 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
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URIs are XML namespaces.
This document registers one module name in the 'YANG Module Names'
registry, defined in [I-D.ietf-netmod-yang] .
name: ietf-netconf-with-defaults
prefix: nwd
namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults
RFC: XXXX // RFC Ed.: replace XXXX and remove this comment
8. Security Considerations
This document defines a minor extension to existing NETCONF protocol
operations. It does not introduce any new or increased security
risks into the management system.
The 'with-defaults' capability gives client control over the
retrieval of particular types of XML data from a configuration
datastore. They only suppress data that can already be retrieved
with the standard protocol operations, and do not add any data to the
configuration datastore.
9. Acknowledgements
Thanks to Martin Bjorklund, Sharon Chisholm, Phil Shafer, Juergen
Schoenwaelder, Washam Fan and many other members of the NETCONF WG
for providing important input to this document.
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.
[RFC4741] Enns, R., "NETCONF Configuration Protocol", RFC 4741,
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December 2006.
[I-D.ietf-netconf-4741bis]
Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
Bierman, "Network Configuration Protocol (NETCONF)",
draft-ietf-netconf-4741bis-02 (work in progress),
February 2010.
[I-D.ietf-netmod-yang]
Bjorklund, M., "YANG - A data modeling language for
NETCONF", draft-ietf-netmod-yang-12 (work in progress),
April 2010.
[W3C.REC-xml-20081126]
Yergeau, F., Maler, E., Bray, T., Paoli, J., and C.
Sperberg-McQueen, "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>.
Appendix A. Usage Examples
A.1. Example YANG Module
The following YANG module defines an example interfaces table to
demonstrate 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 protocol
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 itf-status-type {
description "Interface status";
type enumeration {
enum ok;
enum 'waking up';
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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 which 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 itf-status {
description
"The current status of this interface.";
type itf-status-type;
config false;
}
}
}
}
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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>
<itf-status>up</itf-status>
</interface>
<interface>
<name>eth1</name>
<mtu>1500</mtu>
<itf-status>up</itf-status>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<itf-status>not feeling so good</itf-status>
</interface>
<interface>
<name>eth3</name>
<mtu>1500</mtu>
<itf-status>waking up</itf-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 |
+--------------+--------------+--------------+
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A.3. Protocol Operation Examples
The following examples shows 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.
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<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>
<itf-status>up</itf-status>
</interface>
<interface>
<name>eth1</name>
<mtu>1500</mtu>
<itf-status>up</itf-status>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<itf-status>not feeling so good</itf-status>
</interface>
<interface>
<name>eth3</name>
<mtu>1500</mtu>
<itf-status>waking up</itf-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 wd:default XML attribute, set to
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'true'. Any subtrees within the element are also considered to be
tagged as dafault data.
The actual data nodes tagged by the server depends on the defaults
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.
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<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>
<itf-status wd:default="true">up</itf-status>
</interface>
<interface>
<name>eth1</name>
<mtu wd:default="true">1500</mtu>
<itf-status wd:default="true">up</itf-status>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<itf-status>not feeling so good</itf-status>
</interface>
<interface>
<name>eth3</name>
<mtu wd:default="true">1500</mtu>
<itf-status>waking up</itf-status>
</interface>
</interfaces>
</data>
</rpc-reply>
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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>
<itf-status>not feeling so good</itf-status>
</interface>
<interface>
<name>eth3</name>
<itf-status>waking up</itf-status>
</interface>
</interfaces>
</data>
</rpc-reply>
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A.3.4. <with-defaults> = 'explicit'
The behavior of the <with-defaults> parameter handling for the value
'explicit' is demonstrated in this example.
<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>
<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>
<itf-status>up</itf-status>
</interface>
<interface>
<name>eth1</name>
<itf-status>up</itf-status>
</interface>
<interface>
<name>eth2</name>
<mtu>9000</mtu>
<itf-status>not feeling so good</itf-status>
</interface>
<interface>
<name>eth3</name>
<mtu>1500</mtu>
<itf-status>waking up</itf-status>
</interface>
</interfaces>
</data>
</rpc-reply>
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Appendix B. Change Log
-- RFC Ed.: remove this section before publication.
B.1. 07-08
Added report-all-tagged mode.
Changed conformance so report-all or report-all-tagged mode SHOULD be
supported.
Clarified capability requirements for each mode, for edit-config and
NV storage requirements.
Changed rpc-error details for unsupported with-defaults value.
Added XSD for wd:default attribute
Expanded example to show report-all-tagged for a basic-mode=trim
server.
B.2. 06-07
Removed text in capability identifier section about adding YANG
module capability URI parameters.
Changed YANG module namespace to match YANG format, and updated
examples to use this new namespace.
Fixed some typos.
B.3. 05-06
Removed ':1.0' from capability URI.
Removed open issues section because all known issues are closed.
Moved examples to a separate appendix, and expanded them.
Added example.yang as an appendix to properly explain the examples
used within the document.
Replaced normative term 'SHALL' with 'MUST' to be consistent within
this document.
Clarified <with-defaults> behavior for non-configuration data nodes.
Clarified various sections based on WGLC comments on mailing list.
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Removed some unused terms.
Reversed the order of the change log sections so the most recent
changes are shown first.
B.4. 04-05
Updated I-D and YANG module boiler-plate.
Removed redundant 'with-defaults' YANG feature.
Changed definition of 'explicit' mode to match the YANG definition
Removed XSD because the YANG is normative and the XSD is
unconstrained, and does not properly extend the 3 affected NETCONF
operations.
Made the YANG module a normative section instead of non-normative
appendix.
Changed YANG from an informative to a normative reference,
Changed 4741bis from an informative to a normative reference because
the YANG module imports the ietf-netconf module in order to augment
some operations.
Updated capability requirements to include YANG module capability
parameters.
Added a description statement to the with-defaults leaf definition.
Update open issues section; ready to close all open issues.
B.5. 03-04
Clarifications
Added non-netconf interfaces to the definition of explicitly set
default data
B.6. 02-03
Clarifications
YAM added
Use the same URN for the capability and the XML namespace to
accommodate YANG, and avoid two separate URN/URIs being advertised in
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the HELLO message, for such a small function.
B.7. 01-02
report-all made mandatory
Placeholder for YAM added, XSD will be removed when 4741 provides the
NETCONF YAM
with-defaults is valid for state data as well (if state data has a
defined default which might not be so frequent). The definition of
explicit was modified for state data.
B.8. 00-01
Changed value set of with-default capability and element
Added version to URI
B.9. -00
Created from draft-bierman-netconf-with-defaults-01.txt
It was decided by the NETCONF mailing list, that with-defaults should
be a sub-element of each affected operation. While this violates the
XSD of RFC4741 this is acceptable and follows the ideas behind
NETCONF and YANG.
Hopefully it will be clarified in the 4741bis RFC whether such
extensions are allowed.
Authors' Addresses
Andy Bierman
InterWorking Labs
Scotts Valley, CA
USA
Phone: +1 831 460 7010
Email: andyb@iwl.com
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Balazs Lengyel
Ericsson
Budapest,
Hungary
Email: balazs.lengyel@ericsson.com
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