Network Management Datastore Architecture
draft-ietf-netmod-revised-datastores-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8342.
|
|
|---|---|---|---|
| Authors | Martin Björklund , Jürgen Schönwälder , Philip A. Shafer , Kent Watsen , Robert Wilton | ||
| Last updated | 2017-07-03 | ||
| Replaces | draft-nmdsdt-netmod-revised-datastores | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
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| Send notices to | (None) |
draft-ietf-netmod-revised-datastores-03
Network Working Group M. Bjorklund
Internet-Draft Tail-f Systems
Intended status: Standards Track J. Schoenwaelder
Expires: January 4, 2018 Jacobs University
P. Shafer
K. Watsen
Juniper Networks
R. Wilton
Cisco Systems
July 3, 2017
Network Management Datastore Architecture
draft-ietf-netmod-revised-datastores-03
Abstract
Datastores are a fundamental concept binding the data models written
in the YANG data modeling language to network management protocols
such as NETCONF and RESTCONF. This document defines an architectural
framework for datastores based on the experience gained with the
initial simpler model, addressing requirements that were not well
supported in the initial model.
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 January 4, 2018.
Copyright Notice
Copyright (c) 2017 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
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(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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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Original Model of Datastores . . . . . . . . . . . . . . 6
4. Architectural Model of Datastores . . . . . . . . . . . . . . 8
4.1. The Startup Configuration Datastore (<startup>) . . . . . 9
4.2. The Candidate Configuration Datastore (<candidate>) . . . 10
4.3. The Running Configuration Datastore (<running>) . . . . . 10
4.4. The Intended Configuration Datastore (<intended>) . . . . 10
4.5. Conventional Configuration Datastores . . . . . . . . . . 11
4.6. Dynamic Datastores . . . . . . . . . . . . . . . . . . . 11
4.7. The Operational State Datastore (<operational>) . . . . . 11
4.7.1. Missing Resources . . . . . . . . . . . . . . . . . . 12
4.7.2. System-controlled Resources . . . . . . . . . . . . . 13
4.7.3. Origin Metadata Annotation . . . . . . . . . . . . . 13
5. Implications on YANG . . . . . . . . . . . . . . . . . . . . 14
5.1. XPath Context . . . . . . . . . . . . . . . . . . . . . . 14
6. YANG Modules . . . . . . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
7.1. Updates to the IETF XML Registry . . . . . . . . . . . . 21
7.2. Updates to the YANG Module Names Registry . . . . . . . . 22
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
10.1. Normative References . . . . . . . . . . . . . . . . . . 23
10.2. Informative References . . . . . . . . . . . . . . . . . 23
Appendix A. Guidelines for Defining Datastores . . . . . . . . . 24
A.1. Define which YANG modules can be used in the datastore . 24
A.2. Define which subset of YANG-modeled data applies . . . . 25
A.3. Define how data is actualized . . . . . . . . . . . . . . 25
A.4. Define which protocols can be used . . . . . . . . . . . 25
A.5. Define YANG identities for the datastore . . . . . . . . 25
Appendix B. Ephemeral Dynamic Datastore Example . . . . . . . . 25
Appendix C. Example Data . . . . . . . . . . . . . . . . . . . . 27
C.1. System Example . . . . . . . . . . . . . . . . . . . . . 27
C.2. BGP Example . . . . . . . . . . . . . . . . . . . . . . . 29
C.2.1. Datastores . . . . . . . . . . . . . . . . . . . . . 31
C.2.2. Adding a Peer . . . . . . . . . . . . . . . . . . . . 31
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C.2.3. Removing a Peer . . . . . . . . . . . . . . . . . . . 32
C.3. Interface Example . . . . . . . . . . . . . . . . . . . . 33
C.3.1. Pre-provisioned Interfaces . . . . . . . . . . . . . 33
C.3.2. System-provided Interface . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction
This document provides an architectural framework for datastores as
they are used by network management protocols such as NETCONF
[RFC6241], RESTCONF [RFC8040] and the YANG [RFC7950] data modeling
language. Datastores are a fundamental concept binding network
management data models to network management protocols. Agreement on
a common architectural model of datastores ensures that data models
can be written in a network management protocol agnostic way. This
architectural framework identifies a set of conceptual datastores but
it does not mandate that all network management protocols expose all
these conceptual datastores. This architecture is agnostic with
regard to the encoding used by network management protocols.
2. Terminology
This document defines the following terms:
o datastore: A conceptual place to store and access information. A
datastore might be implemented, for example, using files, a
database, flash memory locations, or combinations thereof. A
datastore maps to an instantiated YANG data tree.
o configuration: Data that is required to get a device from its
initial default state into a desired operational state. This data
is modeled in YANG using "config true" nodes. Configuration can
originate from different sources.
o configuration datastore: A datastore holding configuration.
o running configuration datastore: A configuration datastore holding
the current configuration of the device. It may include inactive
configuration or template-mechanism-oriented configuration that
require further expansion. This datastore is commonly referred to
as "<running>".
o candidate configuration datastore: A configuration datastore that
can be manipulated without impacting the device's running
configuration datastore and that can be committed to the running
configuration datastore. This datastore is commonly referred to
as "<candidate>".
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o startup configuration datastore: A configuration datastore holding
the configuration loaded by the device into the running
configuration datastore when it boots. This datastore is commonly
referred to as "<startup>".
o intended configuration: Configuration that is intended to be used
by the device. For example, intended configuration excludes any
inactive configuration and it would include configuration produced
through the expansion of templates.
o intended configuration datastore: A configuration datastore
holding the complete intended configuration of the device. This
datastore is commonly referred to as "<intended>".
o conventional configuration datastore: One of the following set of
configuration datastores: <running>, <startup>, <candidate>, and
<intended>. These datastores share a common schema and protocol
operations allow copying data between these datastores. The term
"conventional" is chosen as a generic umbrella term for these
datastores.
o conventional configuration: Configuration that is stored in any of
the conventional configuration datastores.
o dynamic datastore: A datastore holding data obtained dynamically
during the operation of a device through interaction with other
systems, rather than through one of the conventional configuration
datastores.
o dynamic configuration: Configuration obtained via a dynamic
datastore.
o learned configuration: Configuration that has been learned via
protocol interactions with other systems that is not conventional
or dynamic configuration.
o system configuration: Configuration that is supplied by the device
itself.
o default configuration: Configuration that is not explicitly
provided but for which a value defined in the data model is used.
o applied configuration: Configuration that is actively in use by a
device. Applied configuration originates from conventional,
dynamic, learned, system and default configuration.
o system state: The additional data on a system that is not
configuration, such as read-only status information and collected
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statistics. System state is transient and modified by
interactions with internal components or other systems. System
state is modeled in YANG using "config false" nodes.
o operational state: The combination of applied configuration and
system state.
o operational state datastore: A datastore holding the complete
operational state of the device. This datastore is commonly
referred to as "<operational>".
o origin: A metadata annotation indicating the origin of a data
item.
o remnant configuration: Configuration that remains part of the
applied configuration for a period of time after it has been
removed from the intended configuration or dynamic configuration.
The time period may be minimal, or may last until all resources
used by the newly-deleted configuration (e.g., network
connections, memory allocations, file handles) have been
deallocated.
The following additional terms are not datastore specific but
commonly used and thus defined here as well:
o client: An entity that can access YANG-defined data on a server,
over some network management protocol.
o server: An entity that provides access to YANG-defined data to a
client, over some network management protocol.
o notification: A server-initiated message indicating that a certain
event has been recognized by the server.
o remote procedure call: An operation that can be invoked by a
client on a server.
3. Background
NETCONF [RFC6241] provides the following definitions:
o datastore: A conceptual place to store and access information. A
datastore might be implemented, for example, using files, a
database, flash memory locations, or combinations thereof.
o configuration datastore: The datastore holding the complete set of
configuration that is required to get a device from its initial
default state into a desired operational state.
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YANG 1.1 [RFC7950] provides the following refinements when NETCONF is
used with YANG (which is the usual case but note that NETCONF was
defined before YANG existed):
o datastore: When modeled with YANG, a datastore is realized as an
instantiated data tree.
o configuration datastore: When modeled with YANG, a configuration
datastore is realized as an instantiated data tree with
configuration.
[RFC6244] defined operational state data as follows:
o Operational state data is a set of data that has been obtained by
the system at runtime and influences the system's behavior similar
to configuration data. In contrast to configuration data,
operational state is transient and modified by interactions with
internal components or other systems via specialized protocols.
Section 4.3.3 of [RFC6244] discusses operational state and among
other things mentions the option to consider operational state as
being stored in another datastore. Section 4.4 of this document then
concludes that at the time of the writing, modeling state as distinct
leafs and distinct branches is the recommended approach.
Implementation experience and requests from operators
[I-D.ietf-netmod-opstate-reqs], [I-D.openconfig-netmod-opstate]
indicate that the datastore model initially designed for NETCONF and
refined by YANG needs to be extended. In particular, the notion of
intended configuration and applied configuration has developed.
Furthermore, separating operational state from configuration in a
separate branch in the data model has been found operationally
complicated, and typically impacts the readability of module
definitions due to overuse of groupings. The relationship between
the branches is not machine readable and filter expressions operating
on configuration and on related operational state are different.
3.1. Original Model of Datastores
The following drawing shows the original model of datastores as it is
currently used by NETCONF [RFC6241]:
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+-------------+ +-----------+
| <candidate> | | <startup> |
| (ct, rw) |<---+ +--->| (ct, rw) |
+-------------+ | | +-----------+
| | | |
| +-----------+ |
+-------->| <running> |<--------+
| (ct, rw) |
+-----------+
|
v
operational state <--- control plane
(cf, ro)
ct = config true; cf = config false
rw = read-write; ro = read-only
boxes denote datastores
Note that this diagram simplifies the model: read-only (ro) and read-
write (rw) is to be understood at a conceptual level. In NETCONF,
for example, support for <candidate> and <startup> is optional and
<running> does not have to be writable. Furthermore, <startup> can
only be modified by copying <running> to <startup> in the
standardized NETCONF datastore editing model. The RESTCONF protocol
does not expose these differences and instead provides only a
writable unified datastore, which hides whether edits are done
through <candidate> or by directly modifying <running> or via some
other implementation specific mechanism. RESTCONF also hides how
configuration is made persistent. Note that implementations may also
have additional datastores that can propagate changes to <running>.
NETCONF explicitly mentions so called named datastores.
Some observations:
o Operational state has not been defined as a datastore although
there were proposals in the past to introduce an operational state
datastore.
o The NETCONF <get/> operation returns the content of the <running>
configuration datastore together with the operational state. It
is therefore necessary that "config false" data is in a different
branch than the "config true" data if the operational state can
have a different lifetime compared to configuration or if
configuration is not immediately or successfully applied.
o Several implementations have proprietary mechanisms that allow
clients to store inactive data in <running>; this inactive data is
only exposed to clients that indicate that they support the
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concept of inactive data; clients not indicating support for
inactive data receive the content of <running> with the inactive
data removed. Inactive data is conceptually removed before
validation.
o Some implementations have proprietary mechanisms that allow
clients to define configuration templates in <running>. These
templates are expanded automatically by the system, and the
resulting configuration is applied internally.
o Some operators have reported that it is essential for them to be
able to retrieve the configuration that has actually been
successfully applied, which may be a subset or a superset of the
<running> configuration.
4. Architectural Model of Datastores
Below is a new conceptual model of datastores extending the original
model in order to reflect the experience gained with the original
model.
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+-------------+ +-----------+
| <candidate> | | <startup> |
| (ct, rw) |<---+ +--->| (ct, rw) |
+-------------+ | | +-----------+
| | | |
| +-----------+ |
+-------->| <running> |<--------+
| (ct, rw) |
+-----------+
|
| // configuration transformations,
| // e.g., removal of "inactive"
| // nodes, expansion of templates
v
+------------+
| <intended> | // subject to validation
| (ct, ro) |
+------------+
| // changes applied, subject to
| // local factors, e.g., missing
| // resources, delays
|
| +-------- learned configuration
dynamic | +-------- system configuration
datastores -----+ | +-------- default configuration
| | |
v v v
+---------------+
| <operational> | <-- system state
| (ct + cf, ro) |
+---------------+
ct = config true; cf = config false
rw = read-write; ro = read-only
boxes denote named datastores
4.1. The Startup Configuration Datastore (<startup>)
The startup configuration datastore (<startup>) is an optional
configuration datastore holding the configuration loaded by the
device when it boots. <startup> is only present on devices that
separate the startup configuration from the running configuration
datastore.
The startup configuration datastore may not be supported by all
protocols or implementations.
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On devices that support non-volatile storage, the contents of
<startup> will typically persist across reboots via that storage. At
boot time, the device loads the saved startup configuration into
<running>. To save a new startup configuration, data is copied to
<startup>, either via implicit or explicit protocol operations.
4.2. The Candidate Configuration Datastore (<candidate>)
The candidate configuration datastore (<candidate>) is an optional
configuration datastore that can be manipulated without impacting the
device's current configuration and that can be committed to
<running>.
The candidate configuration datastore may not be supported by all
protocols or implementations.
<candidate> does not typically persist across reboots, even in the
presence of non-volatile storage. If <candidate> is stored using
non-volatile storage, it should be reset at boot time to the contents
of <running>.
4.3. The Running Configuration Datastore (<running>)
The running configuration datastore (<running>) holds the complete
current configuration on the device. It may include inactive
configuration or template-mechanism-oriented configuration that
require further expansion.
If a device does not have a distinct <startup> and non-volatile is
available, the device will typically use that non-volatile storage to
allow <running> to persist across reboots.
4.4. The Intended Configuration Datastore (<intended>)
The intended configuration datastore (<intended>) is a read-only
configuration datastore. It is tightly coupled to <running>. When
data is written to <running>, the data that is to be validated is
also conceptually written to <intended>. Validation is performed on
the contents of <intended>.
For simple implementations, <running> and <intended> are identical.
<intended> does not persist across reboots; its relationship with
<running> makes that unnecessary.
Currently there are no standard mechanisms defined that affect
<intended> so that it would have different contents than <running>,
but this architecture allows for such mechanisms to be defined.
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One example of such a mechanism is support for marking nodes as
inactive in <running>. Inactive nodes are not copied to <intended>,
and are thus not taken into account when validating the
configuration.
Another example is support for templates. Templates are expanded
when copied into <intended>, and the expanded result is validated.
4.5. Conventional Configuration Datastores
The conventional configuration datastores are a set of configuration
datastores that share a common schema, allowing data to be copied
between them. The term is meant as a generic umbrella description of
these datastores. The set of datastores include:
o <running>
o <candidate>
o <startup>
o <intended>
Other conventional configuration datastores may be defined in future
documents.
The flow of data between these datastores is depicted in section
Section 4.
The specific protocols may define explicit operations to copy between
these datastores, e.g., NETCONF's <copy-config> operation.
4.6. Dynamic Datastores
The model recognizes the need for dynamic datastores that are, by
definition, not part of the persistent configuration of a device. In
some contexts, these have been termed ephemeral datastores since the
information is ephemeral, i.e., lost upon reboot. The dynamic
datastores interact with the rest of the system through
<operational>.
4.7. The Operational State Datastore (<operational>)
The operational state datastore (<operational>) is a read-only
datastore that consists of all "config true" and "config false" nodes
defined in the schema. In the original NETCONF model the operational
state only had "config false" nodes. The reason for incorporating
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"config true" nodes here is to be able to expose all operational
settings without having to replicate definitions in the data models.
<operational> contains system state and all configuration actually
used by the system. This includes all applied configuration from
<intended>, system-provided configuration, and default values defined
by any supported data models. In addition, <operational> also
contains applied data from dynamic datastores.
Requests to retrieve nodes from <operational> always return the value
in use if the node exists, regardless of any default value specified
in the YANG module. If no value is returned for a given node, then
this implies that the node is not used by the device.
<operational> does not persist across reboots.
Changes to configuration may take time to percolate through to
<operational>. During this period, <operational> may contain nodes
for both the previous and current configuration, as closely as
possible tracking the current operation of the device. Such remnant
configuration from the previous configuration persists until the
system has released resources used by the newly-deleted configuration
(e.g., network connections, memory allocations, file handles).
As a result of remnant configuration, the semantic constraints
defined in the data model cannot be relied upon for <operational>,
since the system may have remnant configuration whose constraints
were valid with the previous configuration and that are not valid
with the current configuration. Since constraints on "config false"
nodes may refer to "config true" nodes, remnant configuration may
force the violation of those constraints. The constraints that may
not hold include "when", "must", "min-elements", and "max-elements".
Note that syntactic constraints cannot be violated, including
hierarchical organization, identifiers, and type-based constraints.
4.7.1. Missing Resources
Configuration in <intended> can refer to resources that are not
available or otherwise not physically present. In these situations,
these parts of the <intended> configuration are not applied. The
data appears in <intended> but does not appear in <operational>.
A typical example is an interface configuration that refers to an
interface that is not currently present. In such a situation, the
interface configuration remains in <intended> but the interface
configuration will not appear in <operational>.
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Note that configuration validity cannot depend on the current state
of such resources, since that would imply the removing a resource
might render the configuration invalid. This is unacceptable,
especially given that rebooting such a device would fail to boot due
to an invalid configuration. Instead we allow configuration for
missing resources to exist in <running> and <intended>, but it will
not appear in <operational>.
4.7.2. System-controlled Resources
Sometimes resources are controlled by the device and the
corresponding system controlled data appear in (and disappear from)
<operational> dynamically. If a system controlled resource has
matching configuration in <intended> when it appears, the system will
try to apply the configuration, which causes the configuration to
appear in <operational> eventually (if application of the
configuration was successful).
4.7.3. Origin Metadata Annotation
As data flows into <operational>, it is conceptually marked with a
metadata annotation ([RFC7952]) that indicates its origin. The
origin applies to all data nodes except non-presence containers. The
"origin" metadata annotation is defined in Section 6. The values are
YANG identities. The following identities are defined:
o origin: abstract base identity from which the other origin
identities are derived.
o intended: represents data provided by <intended>.
o dynamic: represents data provided by a dynamic datastore.
o system: represents data provided by the system itself, including
both system configuration and system state. Examples of system
configuration include applied configuration for an always existing
loopback interface, or interface configuration that is auto-
created due to the hardware currently present in the device.
o learned: represents configuration that has been learned via
protocol interactions with other systems, including protocols such
as link-layer negotiations, routing protocols, DHCP, etc.
o default: represents data using a default value specified in the
data model, using either values in the "default" statement or any
values described in the "description" statement. The default
origin is only used when the data has not been provided by any
other source.
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o unknown: represents data for which the system cannot identify the
origin.
These identities can be further refined, e.g., there could be
separate identities for particular types or instances of dynamic
datastore derived from "dynamic".
In all cases, the device should report the origin that most
accurately reflects the source of the data that is actively being
used by the system.
In cases where it could be ambiguous as to which origin should be
used, i.e. where the same data node value has originated from
multiple sources, then the description statement in the YANG module
should be used as guidance for choosing the appropriate origin. For
example:
If for a particular configuration node, the associated YANG
description statement indicates that a protocol negotiated value
overrides any configured value, then the origin would be reported as
"learned", even when a learned value is the same as the configured
value.
Conversely, if for a particular configuration node, the associated
YANG description statement indicates that a protocol negotiated value
does not override an explicitly configured value, then the origin
would be reported as "intended" even when a learned value is the same
as the configured value.
In the case that a device cannot provide an accurate origin for a
particular data node then it should use the origin "unknown".
5. Implications on YANG
5.1. XPath Context
If a server implements the architecture defined in this document, the
accessible trees for some XPath contexts are refined as follows:
o If the XPath expression is defined in a substatement to a data
node that represents system state, the accessible tree is all
operational state in the server. The root node has all top-level
data nodes in all modules as children.
o If the XPath expression is defined in a substatement to a
"notification" statement, the accessible tree is the notification
instance and all operational state in the server. If the
notification is defined on the top level in a module, then the
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root node has the node representing the notification being defined
and all top-level data nodes in all modules as children.
Otherwise, the root node has all top-level data nodes in all
modules as children.
o If the XPath expression is defined in a substatement to an "input"
statement in an "rpc" or "action" statement, the accessible tree
is the RPC or action operation instance and all operational state
in the server. The root node has top-level data nodes in all
modules as children. Additionally, for an RPC, the root node also
has the node representing the RPC operation being defined as a
child. The node representing the operation being defined has the
operation's input parameters as children.
o If the XPath expression is defined in a substatement to an
"output" statement in an "rpc" or "action" statement, the
accessible tree is the RPC or action operation instance and all
operational state in the server. The root node has top-level data
nodes in all modules as children. Additionally, for an RPC, the
root node also has the node representing the RPC operation being
defined as a child. The node representing the operation being
defined has the operation's output parameters as children.
6. YANG Modules
<CODE BEGINS> file "ietf-datastores@2017-04-26.yang"
module ietf-datastores {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-datastores";
prefix ds;
organization
"IETF NETMOD (NETCONF Data Modeling Language) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
Author: Martin Bjorklund
<mailto:mbj@tail-f.com>
Author: Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>
Author: Phil Shafer
<mailto:phil@juniper.net>
Bjorklund, et al. Expires January 4, 2018 [Page 15]
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Author: Kent Watsen
<mailto:kwatsen@juniper.net>
Author: Rob Wilton
<rwilton@cisco.com>";
description
"This YANG module defines two sets of identities for datastores.
The first identifies the datastores themselves, the second
identifies are for datastore protperties.
Copyright (c) 2017 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
(http://www.rfc-editor.org/info/rfcxxxx); see the RFC itself
for full legal notices.";
revision 2017-04-26 {
description
"Initial revision.";
reference
"RFC XXXX: Network Management Datastore Architecture";
}
/*
* Identities
*/
identity datastore {
description
"Abstract base identity for datastore identities.";
}
identity conventional {
base datastore;
description
"Abstract base identity for conventional configuration
datastores.";
}
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identity running {
base conventional;
description
"The running configuration datastore.";
}
identity candidate {
base conventional;
description
"The candidate configuration datastore.";
}
identity startup {
base conventional;
description
"The startup configuration datastore.";
}
identity intended {
base conventional;
description
"The intended configuration datastore.";
}
identity dynamic {
base datastore;
description
"Abstract base identity for dynamic datastores.";
}
identity operational {
base datastore;
description
"The operational state datastore.";
}
identity property {
description
"Abstract base identity for datastore identities.";
}
identity writable {
base property;
description
"Used on the 'running' datastore to indicate that it can be
written to.";
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}
identity auto-persist {
base property;
description
"Used on the 'running' datastore to indicate that writes to
it will be automatically persisted.
If the 'startup' datastore is also supported, clients may
query its contents to ensure its synchronization.
If the 'startup' datastore is not supported, and this
property is not set, then clients must use a mechanism
provided by the protocol to explicitly persist the
'running' datastore's contents.";
}
identity rollback-on-error {
base property;
description
"Used on either the 'running' or 'candidate' datastores to
indicate that clients may request atomic update behavior.";
}
identity confirmed-commit {
base property;
description
"Used on the 'candidate' datastore to indicate that
clients may request confirmed-commit update behavior.";
}
identity validate {
base property;
description
"Used on the 'candidate' datastore to indicate that
clients may request datastore validation.";
}
}
<CODE ENDS>
<CODE BEGINS> file "ietf-origin@2017-04-26.yang"
module ietf-origin {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-origin";
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prefix or;
import ietf-yang-metadata {
prefix md;
}
organization
"IETF NETMOD (NETCONF Data Modeling Language) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
Author: Martin Bjorklund
<mailto:mbj@tail-f.com>
Author: Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>
Author: Phil Shafer
<mailto:phil@juniper.net>
Author: Kent Watsen
<mailto:kwatsen@juniper.net>
Author: Rob Wilton
<rwilton@cisco.com>";
description
"This YANG module defines an 'origin' metadata annotation, and a
set of identities for the origin value.
Copyright (c) 2017 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
(http://www.rfc-editor.org/info/rfcxxxx); see the RFC itself
for full legal notices.";
revision 2017-04-26 {
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description
"Initial revision.";
reference
"RFC XXXX: Network Management Datastore Architecture";
}
/*
* Identities
*/
identity origin {
description
"Abstract base identity for the origin annotation.";
}
identity intended {
base origin;
description
"Denotes data from the intended configuration datastore";
}
identity dynamic {
base origin;
description
"Denotes data from a dynamic datastore.";
}
identity system {
base origin;
description
"Denotes data originated by the system itself, including
both system configuration and system state.
Examples of system configuration include applied configuration
for an always existing loopback interface, or interface
configuration that is auto-created due to the hardware
currently present in the device.";
}
identity learned {
base origin;
description
"Denotes configuration learned from protocol interactions with
other devices, instead of via the intended configuration
datastore or any dynamic datastore.
Examples of protocols that provide learned configuration
include link-layer negotiations, routing protocols, and
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DHCP.";
}
identity default {
base origin;
description
"Denotes data that does not have an configured or learned
value, but has a default value in use. Covers both values
defined in a 'default' statement, and values defined via an
explanation in a 'description' statement.";
}
identity unknown {
base origin;
description
"Denotes data for which the system cannot identify the
origin.";
}
/*
* Metadata annotations
*/
md:annotation origin {
type identityref {
base origin;
}
description
"The 'origin' annotation can be present on any node in a
datastore. It specifies from where the node originated.";
}
}
<CODE ENDS>
7. IANA Considerations
7.1. Updates to the IETF XML Registry
This document registers two URIs in the IETF XML registry [RFC3688].
Following the format in [RFC3688], the following registrations are
requested:
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URI: urn:ietf:params:xml:ns:yang:ietf-datastores
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-origin
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
7.2. Updates to the YANG Module Names Registry
This document registers two YANG modules in the YANG Module Names
registry [RFC6020]. Following the format in [RFC6020], the the
following registrations are requested:
name: ietf-datastores
namespace: urn:ietf:params:xml:ns:yang:ietf-datastores
prefix: ds
reference: RFC XXXX
name: ietf-origin
namespace: urn:ietf:params:xml:ns:yang:ietf-origin
prefix: or
reference: RFC XXXX
8. Security Considerations
This document discusses an architectural model of datastores for
network management using NETCONF/RESTCONF and YANG. It has no
security impact on the Internet.
9. Acknowledgments
This document grew out of many discussions that took place since
2010. Several Internet-Drafts ([I-D.bjorklund-netmod-operational],
[I-D.wilton-netmod-opstate-yang], [I-D.ietf-netmod-opstate-reqs],
[I-D.kwatsen-netmod-opstate], [I-D.openconfig-netmod-opstate]) and
[RFC6244] touched on some of the problems of the original datastore
model. The following people were authors to these Internet-Drafts or
otherwise actively involved in the discussions that led to this
document:
o Lou Berger, LabN Consulting, L.L.C., <lberger@labn.net>
o Andy Bierman, YumaWorks, <andy@yumaworks.com>
o Marcus Hines, Google, <hines@google.com>
o Christian Hopps, Deutsche Telekom, <chopps@chopps.org>
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o Acee Lindem, Cisco Systems, <acee@cisco.com>
o Ladislav Lhotka, CZ.NIC, <lhotka@nic.cz>
o Thomas Nadeau, Brocade Networks, <tnadeau@lucidvision.com>
o Anees Shaikh, Google, <aashaikh@google.com>
o Rob Shakir, Google, <robjs@google.com>
Juergen Schoenwaelder was partly funded by Flamingo, a Network of
Excellence project (ICT-318488) supported by the European Commission
under its Seventh Framework Programme.
10. References
10.1. Normative References
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<http://www.rfc-editor.org/info/rfc6241>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<http://www.rfc-editor.org/info/rfc7950>.
[RFC7952] Lhotka, L., "Defining and Using Metadata with YANG",
RFC 7952, DOI 10.17487/RFC7952, August 2016,
<http://www.rfc-editor.org/info/rfc7952>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<http://www.rfc-editor.org/info/rfc8040>.
10.2. Informative References
[I-D.bjorklund-netmod-operational]
Bjorklund, M. and L. Lhotka, "Operational Data in NETCONF
and YANG", draft-bjorklund-netmod-operational-00 (work in
progress), October 2012.
[I-D.ietf-netmod-opstate-reqs]
Watsen, K. and T. Nadeau, "Terminology and Requirements
for Enhanced Handling of Operational State", draft-ietf-
netmod-opstate-reqs-04 (work in progress), January 2016.
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[I-D.kwatsen-netmod-opstate]
Watsen, K., Bierman, A., Bjorklund, M., and J.
Schoenwaelder, "Operational State Enhancements for YANG,
NETCONF, and RESTCONF", draft-kwatsen-netmod-opstate-02
(work in progress), February 2016.
[I-D.openconfig-netmod-opstate]
Shakir, R., Shaikh, A., and M. Hines, "Consistent Modeling
of Operational State Data in YANG", draft-openconfig-
netmod-opstate-01 (work in progress), July 2015.
[I-D.wilton-netmod-opstate-yang]
Wilton, R., ""With-config-state" Capability for NETCONF/
RESTCONF", draft-wilton-netmod-opstate-yang-02 (work in
progress), December 2015.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<http://www.rfc-editor.org/info/rfc3688>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<http://www.rfc-editor.org/info/rfc6020>.
[RFC6244] Shafer, P., "An Architecture for Network Management Using
NETCONF and YANG", RFC 6244, DOI 10.17487/RFC6244, June
2011, <http://www.rfc-editor.org/info/rfc6244>.
Appendix A. Guidelines for Defining Datastores
The definition of a new datastore in this architecture should be
provided in a document (e.g., an RFC) purposed to the definition of
the datastore. When it makes sense, more than one datastore may be
defined in the same document (e.g., when the datastores are logically
connected). Each datastore's definition should address the points
specified in the sections below.
A.1. Define which YANG modules can be used in the datastore
Not all YANG modules may be used in all datastores. Some datastores
may constrain which data models can be used in them. If it is
desirable that a subset of all modules can be targeted to the
datastore, then the documentation defining the datastore must
indicate this.
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A.2. Define which subset of YANG-modeled data applies
By default, the data in a datastore is modeled by all YANG statements
in the available YANG modules. However, it is possible to specify
criteria that YANG statements must satisfy in order to be present in
a datastore. For instance, maybe only "config true" nodes are
present, or "config false nodes" that also have a specific YANG
extension (e.g., "i2rs:ephemeral true") are present in the datastore.
A.3. Define how data is actualized
The new datastore must specify how it interacts with other
datastores. For example, the diagram in Section 4 depicts dynamic
datastores feeding into <operational>. How this interaction occurs
must be defined by any dynamic datastore. In some cases, it may
occur implicitly, as soon as the data is put into the dynamic
datastore while, in other cases, an explicit action (e.g., an RPC)
may be required to trigger the application of the datastore's data.
A.4. Define which protocols can be used
By default, it is assumed that both the NETCONF and RESTCONF
protocols can be used to interact with a datastore. However, it may
be that only a specific protocol can be used (e.g., ForCES) or that a
subset of all protocol operations or capabilities are available
(e.g., no locking or no XPath-based filtering).
A.5. Define YANG identities for the datastore
The datastore must be defined with a YANG identity that uses the
"ds:datastore" identity or one of its derived identities as its base.
This identity is necessary so that the datastore can be referenced in
protocol operations (e.g., <get-data>).
The datastore may also be defined with an identity that uses the
"or:origin" identity or one its derived identities as its base. This
identity is needed if the datastore interacts with <operational> so
that data originating from the datastore can be identified as such
via the "origin" metadata attribute defined in Section 6.
An example of these guidelines in use is provided in Appendix B.
Appendix B. Ephemeral Dynamic Datastore Example
The section defines documentation for an example dynamic datastore
using the guidelines provided in Appendix A. While this example is
very terse, it is expected to be that a standalone RFC would be
needed when fully expanded.
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This example defines a dynamic datastore called "ephemeral", which is
loosely modeled after the work done in the I2RS working group.
1. Name : ephemeral
2. YANG modules : all (default)
3. YANG statements : config false + ephemeral true
4. How applied : automatic
5. Protocols : NC/RC (default)
6. YANG Module : (see below)
module example-ds-ephemeral {
yang-version 1.1;
namespace "urn:example:ds-ephemeral";
prefix eph;
import ietf-datastores {
prefix ds;
}
import ietf-origin {
prefix or;
}
// add datastore identity
identity ds-ephemeral {
base ds:datastore;
description
"The 'ephemeral' datastore.";
}
// add origin identity
identity or-ephemeral {
base or:dynamic;
description
"Denotes data from the ephemeral dynamic datastore.";
}
// define ephemeral extension
extension ephemeral {
argument "value";
description
"This extension is mixed into config false YANG nodes to
indicate that they are writable nodes in the 'ephemeral'
datastore. This statement takes a single argument
representing a boolean having the values 'true' and
'false'. The default value is 'false'.";
}
}
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Appendix C. Example Data
The use of datastores is complex, and many of the subtle effects are
more easily presented using examples. This section presents a series
of example data models with some sample contents of the various
datastores.
C.1. System Example
In this example, the following fictional module is used:
module example-system {
yang-version 1.1;
namespace urn:example:system;
prefix sys;
import ietf-inet-types {
prefix inet;
}
container system {
leaf hostname {
type string;
}
list interface {
key name;
leaf name {
type string;
}
container auto-negotiation {
leaf enabled {
type boolean;
default true;
}
leaf speed {
type uint32;
units mbps;
description
"The advertised speed, in mbps.";
}
}
leaf speed {
type uint32;
units mbps;
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config false;
description
"The speed of the interface, in mbps.";
}
list address {
key ip;
leaf ip {
type inet:ip-address;
}
leaf prefix-length {
type uint8;
}
}
}
}
}
The operator has configured the host name and two interfaces, so the
contents of <intended> is:
<system xmlns="urn:example:system">
<hostname>foo</hostname>
<interface>
<name>eth0</name>
<auto-negotiation>
<speed>1000</speed>
</auto-negotiation>
<address>
<ip>2001:db8::10</ip>
<prefix-length>32</prefix-length>
</address>
</interface>
<interface>
<name>eth1</name>
<address>
<ip>2001:db8::20</ip>
<prefix-length>32</prefix-length>
</address>
</interface>
</system>
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The system has detected that the hardware for one of the configured
interfaces ("eth1") is not yet present, so the configuration for that
interface is not applied. Further, the system has received a host
name and an additional IP address for "eth0" over DHCP. In addition
to a default value, a loopback interface is automatically added by
the system, and the result of the "speed" auto-negotiation. All of
this is reflected in <operational>:
<system
xmlns="urn:example:system"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin">
<hostname or:origin="or:dynamic">bar</hostname>
<interface or:origin="or:intended">
<name>eth0</name>
<auto-negotiation>
<enabled or:origin="or:default">true</enabled>
<speed>1000</speed>
</auto-negotiation>
<speed>100</speed>
<address>
<ip>2001:db8::10</ip>
<prefix-length>64</prefix-length>
</address>
<address or:origin="or:dynamic">
<ip>2001:db8::1:100</ip>
<prefix-length>64</prefix-length>
</address>
</interface>
<interface or:origin="or:system">
<name>lo0</name>
<address>
<ip>::1</ip>
<prefix-length>128</prefix-length>
</address>
</interface>
</system>
C.2. BGP Example
Consider the following piece of a ersatz BGP module:
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container bgp {
leaf local-as {
type uint32;
}
leaf peer-as {
type uint32;
}
list peer {
key name;
leaf name {
type ipaddress;
}
leaf local-as {
type uint32;
description
".... Defaults to ../local-as";
}
leaf peer-as {
type uint32;
description
"... Defaults to ../peer-as";
}
leaf local-port {
type inet:port;
}
leaf remote-port {
type inet:port;
default 179;
}
leaf state {
config false;
type enumeration {
enum init;
enum established;
enum closing;
}
}
}
}
In this example model, both bgp/peer/local-as and bgp/peer/peer-as
have complex hierarchical values, allowing the user to specify
default values for all peers in a single location.
The model also follows the pattern of fully integrating state
("config false") nodes with configuration ("config true") nodes.
There is not separate "bgp-state" hierarchy, with the accompanying
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repetition of containment and naming nodes. This makes the model
simpler and more readable.
C.2.1. Datastores
Each datastore represents differing views of these nodes. <running>
will hold the configuration provided by the user, for example a
single BGP peer. <intended> will conceptually hold the data as
validated, after the removal of data not intended for validation and
after any local template mechanisms are performed. <operational>
will show data from <intended> as well as any "config false" nodes.
C.2.2. Adding a Peer
If the user configures a single BGP peer, then that peer will be
visible in both <running> and <intended>. It may also appear in
<candidate>, if the server supports the "candidate" feature.
Retrieving the peer will return only the user-specified values.
No time delay should exist between the appearance of the peer in
<running> and <intended>.
In this scenario, we've added the following to <running>:
<bgp>
<local-as>64642</local-as>
<peer-as>65000</peer-as>
<peer>
<name>10.1.2.3</name>
</peer>
</bgp>
C.2.2.1. <operational>
<operational> will contain the fully expanded peer data, including
"config false" nodes. In our example, this means the "state" node
will appear.
In addition, <operational> will contain the "currently in use" values
for all nodes. This means that local-as and peer-as will be
populated even if they are not given values in <intended>. The value
of bgp/local-as will be used if bgp/peer/local-as is not provided;
bgp/peer-as and bgp/peer/peer-as will have the same relationship. In
the operational view, this means that every peer will have values for
their local-as and peer-as, even if those values are not explicitly
configured but are provided by bgp/local-as and bgp/peer-as.
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Each BGP peer has a TCP connection associated with it, using the
values of local-port and remote-port from <intended>. If those
values are not supplied, the system will select values. When the
connection is established, <operational> will contain the current
values for the local-port and remote-port nodes regardless of the
origin. If the system has chosen the values, the "origin" attribute
will be set to "system". Before the connection is established, one
or both of the nodes may not appear, since the system may not yet
have their values.
<bgp origin="or:intended" xmlns="urn:example:bgp">
<local-as origin="or:intended">64642</local-as>
<peer-as origin="or:intended">65000</peer-as>
<peer origin="or:intended">
<name origin="or:intended">10.1.2.3</name>
<local-as origin="or:default">64642</local-as>
<peer-as origin="or:default">65000</peer-as>
<local-port origin="or:system">60794</local-port>
<remote-port origin="or:default">179</remote-port>
</peer>
</bgp>
C.2.3. Removing a Peer
Changes to configuration may take time to percolate through the
various software components involved. During this period, it is
imperative to continue to give an accurate view of the working of the
device. <operational> will contain nodes for both the previous and
current configuration, as closely as possible tracking the current
operation of the device.
Consider the scenario where a client removes a BGP peer. When a peer
is removed, the operational state will continue to reflect the
existence of that peer until the peer's resources are released,
including closing the peer's connection. During this period, the
current data values will continue to be visible in <operational>,
with the "origin" attribute set to indicate the origin of the
original data.
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<bgp origin="or:intended">
<local-as origin="or:intended">64642</local-as>
<peer-as origin="or:intended">65000</peer-as>
<peer origin="or:intended">
<name origin="or:intended">10.1.2.3</name>
<local-as origin="or:default">64642</local-as>
<peer-as origin="or:default">65000</peer-as>
<local-port origin="or:system">60794</local-port>
<remote-port origin="or:default">179</remote-port>
</peer>
</bgp>
Once resources are released and the connection is closed, the peer's
data is removed from <operational>.
C.3. Interface Example
In this section, we'll use this simple interface data model:
container interfaces {
list interface {
key name;
leaf name {
type string;
}
leaf description {
type string;
}
leaf mtu {
type uint;
}
leaf ipv4-address {
type inet:ipv4-address;
}
}
}
C.3.1. Pre-provisioned Interfaces
One common issue in networking devices is the support of Field
Replaceable Units (FRUs) that can be inserted and removed from the
device without requiring a reboot or interfering with normal
operation. These FRUs are typically interface cards, and the devices
support pre-provisioning of these interfaces.
If a client creates an interface "et-0/0/0" but the interface does
not physically exist at this point, then <intended> might contain the
following:
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<interfaces>
<interface>
<name>et-0/0/0</name>
<description>Test interface</description>
</interface>
</interfaces>
Since the interface does not exist, this data does not appear in
<operational>.
When a FRU containing this interface is inserted, the system will
detect it and process the associated configuration. The
<operational> will contain the data from <intended>, as well as the
"config false" nodes, such as the current value of the interface's
MTU.
<interfaces origin="or:intended">
<interface origin="or:intended">
<name origin="or:intended">et-0/0/0</name>
<description origin="or:intended">Test interface</description>
<mtu origin="or:system">1500</mtu>
</interface>
</interfaces>
If the FRU is removed, the interface data is removed from
<operational>.
C.3.2. System-provided Interface
Imagine if the system provides a loopback interface (named "lo0")
with a default ipv4-address of "127.0.0.1". The system will only
provide configuration for this interface if there is no data for it
in <intended>.
When no configuration for "lo0" appears in <intended>, then
<operational> will show the system-provided data:
<interfaces origin="or:intended">
<interface origin="or:system">
<name origin="or:system">lo0</name>
<ipv4-address origin="or:system">127.0.0.1</ipv4-address>
</interface>
</interfaces>
When configuration for "lo0" does appear in <intended>, then
<operational> will show that data with the origin set to "intended".
If the "ipv4-address" is not provided, then the system-provided value
will appear as follows:
Bjorklund, et al. Expires January 4, 2018 [Page 34]
Internet-Draft July 2017
<interfaces origin="or:intended">
<interface origin="or:intended">
<name origin="or:intended">lo0</name>
<description origin="or:intended">loopback</description>
<ipv4-address origin="or:system">127.0.0.1</ipv4-address>
</interface>
</interfaces>
Authors' Addresses
Martin Bjorklund
Tail-f Systems
Email: mbj@tail-f.com
Juergen Schoenwaelder
Jacobs University
Email: j.schoenwaelder@jacobs-university.de
Phil Shafer
Juniper Networks
Email: phil@juniper.net
Kent Watsen
Juniper Networks
Email: kwatsen@juniper.net
Robert Wilton
Cisco Systems
Email: rwilton@cisco.com
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