RFC 8641
Subscription to YANG Notifications for Datastore Updates
Pages: 58
Proposed Standard
Proposed Standard
Part 3 of 3 – Pages 34 to 58
5. YANG Module for YANG-Push
This YANG module imports typedefs from [RFC6991], identities from [RFC8342], the "yang-data" extension from [RFC8040], and the "yang-patch" grouping from [RFC8072]. In addition, it imports and augments many definitions from [RFC8639]. It also references [RFC6241], [XPATH] ("XML Path Language (XPath) Version 1.0"), and [RFC7950]. <CODE BEGINS> file "ietf-yang-push@2019-09-09.yang" module ietf-yang-push { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-push"; prefix yp; import ietf-yang-types { prefix yang; reference "RFC 6991: Common YANG Data Types"; } import ietf-subscribed-notifications { prefix sn; reference "RFC 8639: Subscription to YANG Notifications"; } import ietf-datastores { prefix ds; reference "RFC 8342: Network Management Datastore Architecture (NMDA)"; } import ietf-restconf { prefix rc; reference "RFC 8040: RESTCONF Protocol"; } import ietf-yang-patch { prefix ypatch; reference "RFC 8072: YANG Patch Media Type"; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: <https:/datatracker.ietf.org/wg/netconf/> WG List: <mailto:netconf@ietf.org> Author: Alexander Clemm
<mailto:ludwig@clemm.org>
Author: Eric Voit
<mailto:evoit@cisco.com>";
description
"This module contains YANG specifications for YANG-Push.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
Copyright (c) 2019 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
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 8641; see the
RFC itself for full legal notices.";
revision 2019-09-09 {
description
"Initial revision.";
reference
"RFC 8641: Subscriptions to YANG Datastores";
}
/*
* FEATURES
*/
feature on-change {
description
"This feature indicates that on-change triggered subscriptions
are supported.";
}
/*
* IDENTITIES
*/
/* Error type identities for datastore subscription */
identity resync-subscription-error {
description
"Problem found while attempting to fulfill a
'resync-subscription' RPC request.";
}
identity cant-exclude {
base sn:establish-subscription-error;
description
"Unable to remove the set of 'excluded-change' parameters.
This means that the publisher is unable to restrict
'push-change-update' notifications to just the change types
requested for this subscription.";
}
identity datastore-not-subscribable {
base sn:establish-subscription-error;
base sn:subscription-terminated-reason;
description
"This is not a subscribable datastore.";
}
identity no-such-subscription-resync {
base resync-subscription-error;
description
"The referenced subscription doesn't exist. This may be as a
result of a nonexistent subscription ID, an ID that belongs to
another subscriber, or an ID for a configured subscription.";
}
identity on-change-unsupported {
base sn:establish-subscription-error;
description
"On-change is not supported for any objects that are
selectable by this filter.";
}
identity on-change-sync-unsupported {
base sn:establish-subscription-error;
description
"Neither 'sync-on-start' nor resynchronization is supported for
this subscription. This error will be used for two reasons:
(1) if an 'establish-subscription' RPC includes
'sync-on-start' but the publisher can't support sending a
'push-update' for this subscription for reasons other than
'on-change-unsupported' or 'sync-too-big'
(2) if the 'resync-subscription' RPC is invoked for either an
existing periodic subscription or an on-change subscription
that can't support resynchronization.";
}
identity period-unsupported {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
base sn:subscription-suspended-reason;
description
"The requested time period or 'dampening-period' is too short.
This can be for both periodic and on-change subscriptions
(with or without dampening). Hints suggesting alternative
periods may be returned as supplemental information.";
}
identity update-too-big {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
base sn:subscription-suspended-reason;
description
"Periodic or on-change push update data trees exceed a maximum
size limit. Hints on the estimated size of what was too big
may be returned as supplemental information.";
}
identity sync-too-big {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
base resync-subscription-error;
base sn:subscription-suspended-reason;
description
"The 'sync-on-start' or resynchronization data tree exceeds a
maximum size limit. Hints on the estimated size of what was
too big may be returned as supplemental information.";
}
identity unchanging-selection {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
base sn:subscription-terminated-reason;
description
"The selection filter is unlikely to ever select data tree
nodes. This means that based on the subscriber's current
access rights, the publisher recognizes that the selection
filter is unlikely to ever select data tree nodes that change.
Examples for this might be that the node or subtree doesn't
exist, read access is not permitted for a receiver, or static
objects that only change at reboot have been chosen.";
}
/*
* TYPE DEFINITIONS
*/
typedef change-type {
type enumeration {
enum create {
description
"A change that refers to the creation of a new
datastore node.";
}
enum delete {
description
"A change that refers to the deletion of a
datastore node.";
}
enum insert {
description
"A change that refers to the insertion of a new
user-ordered datastore node.";
}
enum move {
description
"A change that refers to a reordering of the target
datastore node.";
}
enum replace {
description
"A change that refers to a replacement of the target
datastore node's value.";
}
}
description
"Specifies different types of datastore changes.
This type is based on the edit operations defined for
YANG Patch, with the difference that it is valid for a
receiver to process an update record that performs a
'create' operation on a datastore node the receiver believes
exists or to process a delete on a datastore node the
receiver believes is missing.";
reference
"RFC 8072: YANG Patch Media Type, Section 2.5";
}
typedef selection-filter-ref {
type leafref {
path "/sn:filters/yp:selection-filter/yp:filter-id";
}
description
"This type is used to reference a selection filter.";
}
typedef centiseconds {
type uint32;
description
"A period of time, measured in units of 0.01 seconds.";
}
/*
* GROUP DEFINITIONS
*/
grouping datastore-criteria {
description
"A grouping to define criteria for which selected objects from
a targeted datastore should be included in push updates.";
leaf datastore {
type identityref {
base ds:datastore;
}
mandatory true;
description
"Datastore from which to retrieve data.";
}
uses selection-filter-objects;
}
grouping selection-filter-types {
description
"This grouping defines the types of selectors for objects
from a datastore.";
choice filter-spec {
description
"The content filter specification for this request.";
anydata datastore-subtree-filter {
if-feature "sn:subtree";
description
"This parameter identifies the portions of the
target datastore to retrieve.";
reference
"RFC 6241: Network Configuration Protocol (NETCONF),
Section 6";
}
leaf datastore-xpath-filter {
if-feature "sn:xpath";
type yang:xpath1.0;
description
"This parameter contains an XPath expression identifying
the portions of the target datastore to retrieve.
If the expression returns a node set, all nodes in the
node set are selected by the filter. Otherwise, if the
expression does not return a node set, the filter
doesn't select any nodes.
The expression is evaluated in the following XPath
context:
o The set of namespace declarations is the set of prefix
and namespace pairs for all YANG modules implemented
by the server, where the prefix is the YANG module
name and the namespace is as defined by the
'namespace' statement in the YANG module.
If the leaf is encoded in XML, all namespace
declarations in scope on the 'stream-xpath-filter'
leaf element are added to the set of namespace
declarations. If a prefix found in the XML is
already present in the set of namespace declarations,
the namespace in the XML is used.
o The set of variable bindings is empty.
o The function library is comprised of the core
function library and the XPath functions defined in
Section 10 in RFC 7950.
o The context node is the root node of the target
datastore.";
reference
"XML Path Language (XPath) Version 1.0
(https://www.w3.org/TR/1999/REC-xpath-19991116)
RFC 7950: The YANG 1.1 Data Modeling Language,
Section 10";
}
}
}
grouping selection-filter-objects {
description
"This grouping defines a selector for objects from a
datastore.";
choice selection-filter {
description
"The source of the selection filter applied to the
subscription. This will either (1) come referenced from a
global list or (2) be provided in the subscription itself.";
case by-reference {
description
"Incorporates a filter that has been configured
separately.";
leaf selection-filter-ref {
type selection-filter-ref;
mandatory true;
description
"References an existing selection filter that is to be
applied to the subscription.";
}
}
case within-subscription {
description
"A local definition allows a filter to have the same
lifecycle as the subscription.";
uses selection-filter-types;
}
}
}
grouping update-policy-modifiable {
description
"This grouping describes the datastore-specific subscription
conditions that can be changed during the lifetime of the
subscription.";
choice update-trigger {
description
"Defines necessary conditions for sending an event record to
the subscriber.";
case periodic {
container periodic {
presence "indicates a periodic subscription";
description
"The publisher is requested to periodically notify the
receiver regarding the current values of the datastore
as defined by the selection filter.";
leaf period {
type centiseconds;
mandatory true;
description
"Duration of time that should occur between periodic
push updates, in units of 0.01 seconds.";
}
leaf anchor-time {
type yang:date-and-time;
description
"Designates a timestamp before or after which a series
of periodic push updates are determined. The next
update will take place at a point in time that is a
multiple of a period from the 'anchor-time'.
For example, for an 'anchor-time' that is set for the
top of a particular minute and a period interval of a
minute, updates will be sent at the top of every
minute that this subscription is active.";
}
}
}
case on-change {
if-feature "on-change";
container on-change {
presence "indicates an on-change subscription";
description
"The publisher is requested to notify the receiver
regarding changes in values in the datastore subset as
defined by a selection filter.";
leaf dampening-period {
type centiseconds;
default "0";
description
"Specifies the minimum interval between the assembly of
successive update records for a single receiver of a
subscription. Whenever subscribed objects change and
a dampening-period interval (which may be zero) has
elapsed since the previous update record creation for
a receiver, any subscribed objects and properties
that have changed since the previous update record
will have their current values marshalled and placed
in a new update record.";
}
}
}
}
}
grouping update-policy {
description
"This grouping describes the datastore-specific subscription
conditions of a subscription.";
uses update-policy-modifiable {
augment "update-trigger/on-change/on-change" {
description
"Includes objects that are not modifiable once a
subscription is established.";
leaf sync-on-start {
type boolean;
default "true";
description
"When this object is set to 'false', (1) it restricts an
on-change subscription from sending 'push-update'
notifications and (2) pushing a full selection per the
terms of the selection filter MUST NOT be done for
this subscription. Only updates about changes
(i.e., only 'push-change-update' notifications)
are sent. When set to 'true' (the default behavior),
in order to facilitate a receiver's synchronization,
a full update is sent, via a 'push-update' notification,
when the subscription starts. After that,
'push-change-update' notifications are exclusively sent,
unless the publisher chooses to resync the subscription
via a new 'push-update' notification.";
}
leaf-list excluded-change {
type change-type;
description
"Used to restrict which changes trigger an update. For
example, if a 'replace' operation is excluded, only the
creation and deletion of objects are reported.";
}
}
}
}
grouping hints {
description
"Parameters associated with an error for a subscription
made upon a datastore.";
leaf period-hint {
type centiseconds;
description
"Returned when the requested time period is too short. This
hint can assert a viable period for either a periodic push
cadence or an on-change dampening interval.";
}
leaf filter-failure-hint {
type string;
description
"Information describing where and/or why a provided filter
was unsupportable for a subscription.";
}
leaf object-count-estimate {
type uint32;
description
"If there are too many objects that could potentially be
returned by the selection filter, this identifies the
estimate of the number of objects that the filter would
potentially pass.";
}
leaf object-count-limit {
type uint32;
description
"If there are too many objects that could be returned by
the selection filter, this identifies the upper limit of
the publisher's ability to service this subscription.";
}
leaf kilobytes-estimate {
type uint32;
description
"If the returned information could be beyond the capacity
of the publisher, this would identify the estimated
data size that could result from this selection filter.";
}
leaf kilobytes-limit {
type uint32;
description
"If the returned information would be beyond the capacity
of the publisher, this identifies the upper limit of the
publisher's ability to service this subscription.";
}
}
/*
* RPCs
*/
rpc resync-subscription {
if-feature "on-change";
description
"This RPC allows a subscriber of an active on-change
subscription to request a full push of objects.
A successful invocation results in a 'push-update' of all
datastore nodes that the subscriber is permitted to access.
This RPC can only be invoked on the same session on which the
subscription is currently active. In the case of an error, a
'resync-subscription-error' is sent as part of an error
response.";
input {
leaf id {
type sn:subscription-id;
mandatory true;
description
"Identifier of the subscription that is to be resynced.";
}
}
}
rc:yang-data resync-subscription-error {
container resync-subscription-error {
description
"If a 'resync-subscription' RPC fails, the subscription is
not resynced and the RPC error response MUST indicate the
reason for this failure. This yang-data MAY be inserted as
structured data in a subscription's RPC error response
to indicate the reason for the failure.";
leaf reason {
type identityref {
base resync-subscription-error;
}
mandatory true;
description
"Indicates the reason why the publisher has declined a
request for subscription resynchronization.";
}
uses hints;
}
}
augment "/sn:establish-subscription/sn:input" {
description
"This augmentation adds additional subscription parameters
that apply specifically to datastore updates to RPC input.";
uses update-policy;
}
augment "/sn:establish-subscription/sn:input/sn:target" {
description
"This augmentation adds the datastore as a valid target
for the subscription to RPC input.";
case datastore {
description
"Information specifying the parameters of a request for a
datastore subscription.";
uses datastore-criteria;
}
}
rc:yang-data establish-subscription-datastore-error-info {
container establish-subscription-datastore-error-info {
description
"If any 'establish-subscription' RPC parameters are
unsupportable against the datastore, a subscription is not
created and the RPC error response MUST indicate the reason
why the subscription failed to be created. This yang-data
MAY be inserted as structured data in a subscription's
RPC error response to indicate the reason for the failure.
This yang-data MUST be inserted if hints are to be provided
back to the subscriber.";
leaf reason {
type identityref {
base sn:establish-subscription-error;
}
description
"Indicates the reason why the subscription has failed to
be created to a targeted datastore.";
}
uses hints;
}
}
augment "/sn:modify-subscription/sn:input" {
description
"This augmentation adds additional subscription parameters
specific to datastore updates.";
uses update-policy-modifiable;
}
augment "/sn:modify-subscription/sn:input/sn:target" {
description
"This augmentation adds the datastore as a valid target
for the subscription to RPC input.";
case datastore {
description
"Information specifying the parameters of a request for a
datastore subscription.";
uses datastore-criteria;
}
}
rc:yang-data modify-subscription-datastore-error-info {
container modify-subscription-datastore-error-info {
description
"This yang-data MAY be provided as part of a subscription's
RPC error response when there is a failure of a
'modify-subscription' RPC that has been made against a
datastore. This yang-data MUST be used if hints are to be
provided back to the subscriber.";
leaf reason {
type identityref {
base sn:modify-subscription-error;
}
description
"Indicates the reason why the subscription has failed to
be modified.";
}
uses hints;
}
}
/*
* NOTIFICATIONS
*/
notification push-update {
description
"This notification contains a push update that in turn contains
data subscribed to via a subscription. In the case of a
periodic subscription, this notification is sent for periodic
updates. It can also be used for synchronization updates of
an on-change subscription. This notification shall only be
sent to receivers of a subscription. It does not constitute
a general-purpose notification that would be subscribable as
part of the NETCONF event stream by any receiver.";
leaf id {
type sn:subscription-id;
description
"This references the subscription that drove the
notification to be sent.";
}
anydata datastore-contents {
description
"This contains the updated data. It constitutes a snapshot
at the time of update of the set of data that has been
subscribed to. The snapshot corresponds to the same
snapshot that would be returned in a corresponding 'get'
operation with the same selection filter parameters
applied.";
}
leaf incomplete-update {
type empty;
description
"This is a flag that indicates that not all datastore
nodes subscribed to are included with this update. In
other words, the publisher has failed to fulfill its full
subscription obligations and, despite its best efforts, is
providing an incomplete set of objects.";
}
}
notification push-change-update {
if-feature "on-change";
description
"This notification contains an on-change push update. This
notification shall only be sent to the receivers of a
subscription. It does not constitute a general-purpose
notification that would be subscribable as part of the
NETCONF event stream by any receiver.";
leaf id {
type sn:subscription-id;
description
"This references the subscription that drove the
notification to be sent.";
}
container datastore-changes {
description
"This contains the set of datastore changes of the target
datastore, starting at the time of the previous update, per
the terms of the subscription.";
uses ypatch:yang-patch;
}
leaf incomplete-update {
type empty;
description
"The presence of this object indicates that not all changes
that have occurred since the last update are included with
this update. In other words, the publisher has failed to
fulfill its full subscription obligations -- for example,
in cases where it was not able to keep up with a burst of
changes.";
}
}
augment "/sn:subscription-started" {
description
"This augmentation adds datastore-specific objects to
the notification that a subscription has started.";
uses update-policy;
}
augment "/sn:subscription-started/sn:target" {
description
"This augmentation allows the datastore to be included as
part of the notification that a subscription has started.";
case datastore {
uses datastore-criteria {
refine "selection-filter/within-subscription" {
description
"Specifies the selection filter and where it originated
from. If the 'selection-filter-ref' is populated, the
filter in the subscription came from the 'filters'
container. Otherwise, it is populated in-line as part
of the subscription itself.";
}
}
}
}
augment "/sn:subscription-modified" {
description
"This augmentation adds datastore-specific objects to
the notification that a subscription has been modified.";
uses update-policy;
}
augment "/sn:subscription-modified/sn:target" {
description
"This augmentation allows the datastore to be included as
part of the notification that a subscription has been
modified.";
case datastore {
uses datastore-criteria {
refine "selection-filter/within-subscription" {
description
"Specifies the selection filter and where it originated
from. If the 'selection-filter-ref' is populated, the
filter in the subscription came from the 'filters'
container. Otherwise, it is populated in-line as part
of the subscription itself.";
}
}
}
}
/*
* DATA NODES
*/
augment "/sn:filters" {
description
"This augmentation allows the datastore to be included as part
of the selection-filtering criteria for a subscription.";
list selection-filter {
key "filter-id";
description
"A list of preconfigured filters that can be applied
to datastore subscriptions.";
leaf filter-id {
type string;
description
"An identifier to differentiate between selection
filters.";
}
uses selection-filter-types;
}
}
augment "/sn:subscriptions/sn:subscription" {
when 'yp:datastore';
description
"This augmentation adds objects to a subscription that are
specific to a datastore subscription, i.e., a subscription to
a stream of datastore node updates.";
uses update-policy;
}
augment "/sn:subscriptions/sn:subscription/sn:target" {
description
"This augmentation allows the datastore to be included as
part of the selection-filtering criteria for a subscription.";
case datastore {
uses datastore-criteria;
}
}
}
<CODE ENDS>
6. IANA Considerations
This document registers the following namespace URI in the "IETF XML Registry" [RFC3688]: URI: urn:ietf:params:xml:ns:yang:ietf-yang-push Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace. This document registers the following YANG module in the "YANG Module Names" registry [RFC6020]: Name: ietf-yang-push Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-push Prefix: yp Reference: RFC 86417. Security Considerations
The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446]. The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability. (It should be noted that the YANG module defined in this document augments the YANG module defined in [RFC8639]. All security considerations that are listed in
[RFC8639] are also relevant for datastore subscriptions. In the following list, we focus on the new data nodes that are introduced in this document.) o Subtree "selection-filter" under container "filters": This subtree allows a subscriber to specify which objects or subtrees to include in a datastore subscription. An attacker could attempt to modify the filter. For example, the filter might be modified to result in very few objects being filtered in order to attempt to overwhelm the receiver. Alternatively, the filter might be modified to result in certain objects being excluded from updates, in which case certain changes would go unnoticed. o Subtree "datastore" in choice "target" in list "subscription": Analogous to "selection filter", an attacker might attempt to modify the objects being filtered in order to overwhelm a receiver with a larger volume of object updates than expected or cause certain changes to go unnoticed. o Choice "update-trigger" in list "subscription": By modifying the update trigger, an attacker might alter the updates that are being sent in order to confuse a receiver, withhold certain updates to be sent to the receiver, and/or overwhelm a receiver. For example, an attacker might modify the period with which updates are reported for a periodic subscription, or it might modify the dampening period for an on-change subscription, resulting in a greater delay for successive updates (potentially affecting the responsiveness of applications that depend on the updates) or in a high volume of updates (to exhaust receiver resources). The NACM provides one means to mitigate these threats on the publisher side. In order to address those threats as a subscriber, the subscriber could monitor the subscription configuration for any unexpected changes and subscribe to updates to the YANG datastore nodes that represent its datastore subscriptions. As this volume of data is small, a paranoid subscriber could even revert to occasional polling to guard against a compromised subscription against subscription configuration updates itself. Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability: o Subtree "selection-filter" under container "filters": If access control is not properly configured, can expose system internals to those who should not have access to this information.
o Subtree "datastore" in choice "target" in list "subscription": If
access control is not properly configured, can expose system
internals to those who should not have access to this information.
o Choice "update-trigger" in list "subscription": If access control
is not properly configured, can expose system internals to those
who should not have access to this information.
Some of the RPC operations in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control access to these operations. These are the
operations and their sensitivity/vulnerability:
o RPC "resync-subscription": This RPC allows a subscriber of an
on-change subscription to request a full push of objects in the
subscription's scope. This can result in a large volume of data.
An attacker could attempt to use this RPC to exhaust resources on
the server to generate the data and could then attempt to
overwhelm a receiver with the resulting large volume of data.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://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,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, <https://www.rfc-editor.org/info/rfc8040>. [RFC8072] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch Media Type", RFC 8072, DOI 10.17487/RFC8072, February 2017, <https://www.rfc-editor.org/info/rfc8072>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, <https://www.rfc-editor.org/info/rfc8341>. [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "Network Management Datastore Architecture (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, <https://www.rfc-editor.org/info/rfc8342>. [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, <https://www.rfc-editor.org/info/rfc8446>. [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K., and R. Wilton, "YANG Library", RFC 8525, DOI 10.17487/RFC8525, March 2019, <https://www.rfc-editor.org/info/rfc8525>. [RFC8639] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, E., and A. Tripathy, "Subscription to YANG Notifications", RFC 8639, DOI 10.17487/RFC8639, September 2019, <https://www.rfc-editor.org/info/rfc8639>. [W3C.REC-xml-20081126] Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth Edition)", World Wide Web Consortium Recommendation REC-xml-20081126, November 2008, <https://www.w3.org/TR/2008/REC-xml-20081126>. [XPATH] Clark, J. and S. DeRose, "XML Path Language (XPath) Version 1.0", November 1999, <https://www.w3.org/TR/1999/REC-xpath-19991116>.
8.2. Informative 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, <https://www.rfc-editor.org/info/rfc6241>. [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, <https://www.rfc-editor.org/info/rfc6242>. [RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements for Subscription to YANG Datastores", RFC 7923, DOI 10.17487/RFC7923, June 2016, <https://www.rfc-editor.org/info/rfc7923>. [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, <https://www.rfc-editor.org/info/rfc8340>. [RFC8343] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 8343, DOI 10.17487/RFC8343, March 2018, <https://www.rfc-editor.org/info/rfc8343>. [RFC8640] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, E., and A. Tripathy, "Dynamic Subscription to YANG Events and Datastores over NETCONF", RFC 8640, DOI 10.17487/RFC8640, September 2019, <https://www.rfc-editor.org/info/rfc8640>. [Yang-Push-Notif-Cap] Lengyel, B., Clemm, A., and B. Claise, "Yang-Push Notification Capabilities", Work in Progress, draft-ietf-netconf-notification-capabilities-04, September 2019.
Appendix A. Subscription Errors
A.1. RPC Failures
Rejection of an RPC for any reason is indicated via an RPC error response from the publisher. Valid RPC errors returned include both (1) existing transport-layer RPC error codes, such as those seen with NETCONF in [RFC6241] and (2) subscription-specific errors, such as those defined in the YANG data model. As a result, how subscription errors are encoded in an RPC error response is transport dependent. References to specific identities in the ietf-subscribed- notifications YANG module [RFC8639] or the ietf-yang-push YANG module may be returned as part of the error responses resulting from failed attempts at datastore subscription. For errors defined as part of the ietf-subscribed-notifications YANG module, please refer to [RFC8639]. The errors defined in this document, grouped per RPC, are as follows: establish-subscription modify-subscription --------------------------- --------------------- cant-exclude period-unsupported datastore-not-subscribable update-too-big on-change-unsupported sync-too-big on-change-sync-unsupported unchanging-selection period-unsupported update-too-big resync-subscription sync-too-big ---------------------------- unchanging-selection no-such-subscription-resync sync-too-big There is one final set of transport-independent RPC error elements included in the YANG data model. These are the four yang-data structures for failed datastore subscriptions: 1. yang-data "establish-subscription-error-datastore": This MUST be returned if information identifying the reason for an RPC error has not been placed elsewhere in the transport portion of a failed "establish-subscription" RPC response. This MUST be sent if hints are included. 2. yang-data "modify-subscription-error-datastore": This MUST be returned if information identifying the reason for an RPC error has not been placed elsewhere in the transport portion of a failed "modify-subscription" RPC response. This MUST be sent if hints are included.
3. yang-data "sn:delete-subscription-error": This MUST be returned
if information identifying the reason for an RPC error has not
been placed elsewhere in the transport portion of a failed
"delete-subscription" or "kill-subscription" RPC response.
4. yang-data "resync-subscription-error": This MUST be returned if
information identifying the reason for an RPC error has not been
placed elsewhere in the transport portion of a failed
"resync-subscription" RPC response.
A.2. Failure Notifications
A subscription may be unexpectedly terminated or suspended
independently of any RPC or configuration operation. In such cases,
indications of such a failure MUST be provided. To accomplish this,
a number of errors can be returned as part of the corresponding
subscription state change notification. For this purpose, the
following error identities are introduced in this document, in
addition to those that were already defined in [RFC8639]:
subscription-terminated subscription-suspended
--------------------------- ----------------------
datastore-not-subscribable period-unsupported
unchanging-selection update-too-big
synchronization-size
Acknowledgments
For their valuable comments, discussions, and feedback, we wish to acknowledge Tim Jenkins, Martin Bjorklund, Kent Watsen, Susan Hares, Yang Geng, Peipei Guo, Michael Scharf, Guangying Zheng, Tom Petch, Henk Birkholz, Reshad Rahman, Qin Wu, Rohit Ranade, and Rob Wilton.Contributors
The following individuals made substantial contributions to this document and should be considered coauthors. Their contributions include information contained in the YANG module provided in Section 5 of this document. Alberto Gonzalez Prieto Microsoft Email: alberto.gonzalez@microsoft.com Ambika Prasad Tripathy Cisco Systems Email: ambtripa@cisco.com Einar Nilsen-Nygaard Cisco Systems Email: einarnn@cisco.com Andy Bierman YumaWorks Email: andy@yumaworks.com Balazs Lengyel Ericsson Email: balazs.lengyel@ericsson.comAuthors' Addresses
Alexander Clemm Futurewei Email: ludwig@clemm.org Eric Voit Cisco Systems Email: evoit@cisco.com