NETCONF E. Voit
Internet-Draft Cisco Systems
Intended status: Standards Track H. Birkholz
Expires: February 16, 2020 Fraunhofer SIT
A. Bierman
YumaWorks
A. Clemm
Huawei
T. Jenkins
Cisco Systems
August 15, 2019
Notification Message Headers and Bundles
draft-ietf-netconf-notification-messages-06
Abstract
This document defines a new notification message format. Included
are:
o a new notification mechanism and encoding to replace the one way
operation of RFC-5277
o a set of common, transport agnostic message header objects.
o how to bundle multiple event records into a single notification
message.
o how to ensure these new capabilities are only used with capable
receivers.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 16, 2020.
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Copyright Notice
Copyright (c) 2019 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
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Header Objects . . . . . . . . . . . . . . . . . . . . . . . 3
4. Encapsulation of Header Objects in Messages . . . . . . . . . 4
4.1. One Notification per Message . . . . . . . . . . . . . . 4
4.2. Many Notifications per Message . . . . . . . . . . . . . 5
5. Configuration of Headers . . . . . . . . . . . . . . . . . . 8
6. Discovering Receiver Support . . . . . . . . . . . . . . . . 9
7. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 9
8. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 18
9. Security Considerations . . . . . . . . . . . . . . . . . . . 18
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Changes between revisions . . . . . . . . . . . . . 20
Appendix B. Issues being worked . . . . . . . . . . . . . . . . 21
Appendix C. Subscription Specific Headers . . . . . . . . . . . 21
Appendix D. Implications to Existing RFCs . . . . . . . . . . . 22
D.1. Implications to RFC-7950 . . . . . . . . . . . . . . . . 22
D.2. Implications to RFC-8040 . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
Mechanisms to support subscription to event notifications have been
defined in [I-D.draft-ietf-netconf-subscribed-notifications] and
[I-D.ietf-netconf-yang-push]. Work on those documents has shown that
notifications described in [RFC7950] section 7.16 could benefit from
transport independent headers. With such headers, communicating the
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following information to receiving applications can be done without
explicit linkage to an underlying transport protocol:
o the time the notification was generated
o the time the notification was placed in a message and queued for
transport
o an identifier for the process generating the notification
o signatures to verify authenticity
o a subscription id which allows a notification be correlated with a
request for that notification
o multiple notifications bundled into one transportable message
o a message-id allowing a receiver to check for message loss/
reordering
The document describes information elements needed for the functions
above. It also provides instances of YANG structures
[I-D.draft-ietf-netmod-yang-data-ext] for sending messages containing
one or more notifications to a receiver.
2. Terminology
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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The definition of notification is in [RFC7950] Section 4.2.10.
Publisher, receiver, subscription, and event occurrence time are
defined in [I-D.draft-ietf-netconf-subscribed-notifications].
3. Header Objects
There are a number of transport independent headers which should have
common definition. These include:
o subscription-id: provides a reference into the reason the
publisher believed the receiver wishes to be notified of this
specific information.
o notification-time: the origination time where a notification was
fully generated within the publisher.
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o notification-id: Identifies an instance of an emitted notification
to a receiver.
o observation-domain-id: identifies the publisher process which
discovered and recorded the event notification. (note: look to
reuse the domains set up with IPFIX.)
o message-time: the time the message was packaged sent to the
transport layer for delivery to the receiver.
o signature: allows an application to sign a message so that a
receiver can verify the authenticity of the message.
o message-id: for a specific message generator, this identifies a
message which includes one or more event records. The message-id
increments by one with sequential messages.
o message-generator-id: identifier for the process which created the
message. This allows disambiguation of an information source,
such as the identification of different line cards sending the
messages. Used in conjunction with previous-message-id, this can
help find drops and duplications when messages are coming from
multiple sources on a device. If there is a message-generator-id
in the header, then the previous-message-id MUST be the message-id
from the last time that message-generator-id was sent.
4. Encapsulation of Header Objects in Messages
A specific set of well-known objects are of potential use to
networking layers prior being interpreted by some receiving
application layer process. By exposing this object information as
part of a header, and by using standardized object names, it becomes
possible for this object information to be leveraged in transit.
The objects defined in the previous section are these well-known
header objects. These objects are identified within a dedicated
header subtree which leads off a particular transportable message.
This allows header objects to be easily be decoupled, stripped, and
processed separately.
A receiver which supporting this document MUST be able to handle
receipt of either type of message from a publisher.
4.1. One Notification per Message
This section has been deleted from previous versions. It will be re-
instated if NETCONF WG members are not comfortable with the
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efficiency of the solution which can encode many notifications per
message, as described below.
4.2. Many Notifications per Message
While possible in some scenarios, it often inefficient to marshal and
transport every notification independently. Instead, scale and
processing speed can be improved by placing multiple notifications
into one transportable bundle.
The format of this bundle appears in the YANG structure below, and is
fully defined in the YANG module. There are three parts of this
bundle:
o a message header describing the marshaling, including information
such as when the marshaling occurred
o a list of encapsulated information
o an optional message footer for whole-message signing and message-
generator integrity verification.
Within the list of encapsulated notifications, there are also three
parts:
o a notification header defining what is in an encapsulated
notification
o the actual notification itself
o an optional notification footer for individual notification
signing and observation-domain integrity verification.
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structure message
+--ro message!
+--ro message-header
| +--ro message-time yang:date-and-time
| +--ro message-id? uint32
| +--ro message-generator-id? string
| +--ro notification-count? uint16
+--ro notifications*
| +--ro notification-header
| | +--ro notification-time yang:date-and-time
| | +--ro yang-module? yang:yang-identifier
| | +--ro subscription-id* uint32
| | +--ro notification-id? uint32
| | +--ro observation-domain-id? string
| +--ro notification-contents?
| +--ro notification-footer!
| +--ro signature-algorithm string
| +--ro signature-value string
| +--ro integrity-evidence? string
+--ro message-footer!
+--ro signature-algorithm string
+--ro signature-value string
+--ro integrity-evidence? string
An XML instance of a message might look like:
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2017-02-14T00:00:05Z
456
2
2017-02-14T00:00:02Z
823472
ietf-yang-push
push-change-update
...(record #2)...
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5. Configuration of Headers
A publisher MUST select the set of headers to use within any
particular message. The two mandatory headers which MUST always be
applied are 'message-time' and 'subscription-id'
Beyond these two mandatory headers, additional headers MAY be
included. Configuration of what these optional headers should be can
come from the following sources:
1. Publisher wide default headers which are placed on all
notifications. An optional header is a publisher default if its
identity is included within the 'additional-headers' leaf-list.
2. More notification specific headers may also be desired. If new
headers are needed for a specific type of YANG notification,
these can be populated through 'additional-notification-headers'
leaf-list.
3. An application process may also identify common headers to use
when transporting notifications for a specific subscription. How
such application specific configuration is accomplished within
the publisher is out-of-scope.
The set of headers selected and populated for any particular message
is derived from the union of the mandatory headers and configured
optional headers.
The YANG tree showing elements of configuration is depicted in the
following figure.
module: ietf-notification-messages
+--rw additional-default-headers {publisher}?
+--rw additional-headers* optional-header
+--rw yang-notification-specific-default*
| [yang-module yang-notification-name]
+--rw yang-module yang:yang-identifier
+--rw yang-notification-name notification-type
+--rw additional-notification-headers*
optional-notification-header
Configuration Model structure
Of note in this tree is the optional feature of 'publisher'. This
feature indicates an ability to send notifications. A publisher
supporting this specification MUST also be able to parse any messages
received as defined in this document.
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6. Discovering Receiver Support
We need capability exchange from the receiver to the publisher at
transport session initiation to indicate support for this
specification.
For all types of transport connections, if the receiver indicates
support for this specification, then it MAY be used. In addition,
[RFC5277] one-way notifications MUST NOT be used if the receiver
indicates support for this specification to a publisher which also
supports it.
Where NETCONF transport is used, advertising this specification's
namespace during an earlier client capabilities discovery phase MAY
be used to indicate support for this specification:
urn:ietf:params:xml:ns:yang:ietf-notification-messages:1.0
4
NOTE: It is understood that even though it is allowed in [RFC6241]
section 8.1, robust NETCONF client driven capabilities exchange is
not something which is common in implementation. Therefore reviewers
are asked to submit alternative proposals to the mailing list.
For RESTCONF, a mechanism for capability discovery is TBD. Proposals
are welcome here.
The mechanism described above assumes that a capability discovery
phase happens before a subscription is started. This is not always
the case. There is no guarantee that a capability exchange has taken
place before the messages are emitted. A solution for this in the
case of HTTP based transport could be that a receiver would have to
reply "ok" and also return the client capabilities as part a response
to the initiation of the POST.
7. YANG Module
file "ietf-notification-messages@2019-08-16.yang"
module ietf-notification-messages {
yang-version 1.1;
namespace
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"urn:ietf:params:xml:ns:yang:ietf-notification-messages";
prefix nm;
import ietf-yang-types { prefix yang; }
import ietf-yang-structure-ext { prefix sx; }
organization "IETF";
contact
"WG Web:
WG List:
Editor: Eric Voit
Editor: Henk Birkholz
Editor: Alexander Clemm
Editor: Andy Bierman
Editor: Tim Jenkins
";
description
"This module contains conceptual YANG specifications for
messages carrying notifications with well-known header objects.";
revision 2019-08-16 {
description
"Initial version.";
reference
"draft-ietf-netconf-notification-messages-06";
}
/*
* FEATURES
*/
feature publisher {
description
"This feature indicates that support for both publisher and
receiver of messages complying to the specification.";
}
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/*
* IDENTITIES
*/
/* Identities for common headers */
identity common-header {
description
"A well-known header which can be included somewhere within a
message.";
}
identity message-time {
base common-header;
description
"Header information consisting of time the message headers were
generated prior to being sent to transport";
}
identity subscription-id {
base common-header;
description
"Header information consisting of the identifier of the
subscription associated with the notification being
encapsulated.";
}
identity notification-count {
base common-header;
description
"Header information consisting of the quantity of notifications in
a bundled-message for a specific receiver.";
}
identity optional-header {
base common-header;
description
"A well-known header which an application may choose to include
within a message.";
}
identity message-id {
base optional-header;
description
"Header information that identifies a message to a specific
receiver";
}
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identity message-generator-id {
base optional-header;
description
"Header information consisting of an identifier for a software
entity which created the message (e.g., linecard 1).";
}
identity message-signature {
base optional-header;
description
"Identifies two elements of header information consisting of a
signature and the signature type for the contents of a message.
Signatures can be useful for originating applications to
verify record contents even when shipping over unsecure
transport.";
}
identity message-integrity-evidence {
base optional-header;
description
"Header information consisting of the information which backs up
the assertions made as to the validity of the information
provided within the message.";
}
identity optional-notification-header {
base optional-header;
description
"A well-known header which an application may choose to include
within a message.";
}
identity notification-time {
base optional-notification-header;
description
"Header information consisting of the time an originating process
created the notification.";
}
identity notification-id {
base optional-notification-header;
description
"Header information consisting of an identifier for an instance
of a notification. If access control based on a message's receiver may
strip information from within the notification, this notification-id MUST
allow the identification of the specific contents of notification as it
exits the publisher.";
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}
identity observation-domain-id {
base optional-notification-header;
description
"Header information identifying the software entity which created
the notification (e.g., process id).";
}
identity notification-signature {
base optional-notification-header;
description
"Header information consisting of a signature which can be used to prove
the authenticity that some asserter validates over the information
provided within the notification.";
}
identity notification-integrity-evidence {
base optional-notification-header;
description
"Header information consisting of the information which backs up
the assertions made as to the validity of the information
provided within the notification.";
}
/*
* TYPEDEFs
*/
typedef optional-header {
type identityref {
base optional-header;
}
description
"Type of header object which may be included somewhere within a
message.";
}
typedef optional-notification-header {
type identityref {
base optional-notification-header;
}
description
"Type of header object which may be included somewhere within a
message.";
}
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typedef notification-type {
type string {
pattern '[a-zA-Z_][a-zA-Z0-9\-_.]*';
}
description
"The name of a notification within a YANG module.";
reference
"RFC-7950 Section 7.16";
}
/*
* GROUPINGS
*/
grouping message-header {
description
"Header information included with a message.";
leaf message-time {
type yang:date-and-time;
mandatory true;
description
"Time the message was generated prior to being sent to
transport.";
}
leaf message-id {
type uint32;
description
"Id for a message going to a receiver from a message
generator. The id will increment by one with each message sent
from a particular message generator, allowing the message-id
to be used as a sequence number.";
}
leaf message-generator-id {
type string;
description
"Software entity which created the message (e.g., linecard 1).
The combination of message-id and message-generator-id must be
unique until reset or a roll-over occurs.";
}
leaf notification-count {
type uint16;
description
"Quantity of notifications in a bundled-message to a
specific receiver.";
}
}
grouping notification-header {
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description
"Common informational objects which might help a receiver
interpret the meaning, details, or importance of a notification.";
leaf notification-time {
type yang:date-and-time;
mandatory true;
description
"Time the system recognized the occurrence of an event.";
}
leaf yang-module {
type yang:yang-identifier;
description
"Name of the YANG module supported by the publisher.";
}
leaf-list subscription-id {
type uint32;
description
"Id of the subscription which led to the notification being
generated.";
}
leaf notification-id {
type uint32;
description
"Identifier for the notification record.";
}
leaf observation-domain-id {
type string;
description
"Software entity which created the notification record (e.g.,
process id).";
}
}
grouping security-footer {
description
"Reusable grouping for common objects which apply to the signing of
notifications or messages.";
leaf signature-algorithm {
type string;
mandatory true;
description
"The technology with which an originator signed of some
delineated contents.";
}
leaf signature-value {
type string;
mandatory true;
description
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"Any originator signing of the contents of a header and
content. This is useful for verifying contents even when
shipping over unsecure transport.";
}
leaf integrity-evidence {
type string;
description
"This mechanism allows a verifier to ensure that the use of the
private key, represented by the corresponding public key
certificate, was performed with a TCG compliant TPM
environment. This evidence is never included in within any
signature.";
reference
"TCG Infrastructure Workgroup, Subject Key Attestation Evidence
Extension, Specification Version 1.0, Revision 7.";
}
}
/*
* YANG encoded structures which can be sent to receivers
*/
sx:structure message {
container message {
presence
"Indicates attempt to communicate notifications to a receiver.";
description
"Message to a receiver containing one or more notifications";
container message-header {
description
"Header info for messages.";
uses message-header;
}
list notifications {
description
"Set of notifications to a receiver.";
container notification-header {
description
"Header info for a notification.";
uses notification-header;
}
anydata notification-contents {
description
"Encapsulates objects following YANG's notification-stmt
grammar of RFC-7950 section 14. Within are the notified
objects the publisher actually generated in order to be
passed to a receiver after all filtering has completed.";
}
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container notification-footer {
presence
"Indicates attempt to secure a notification.";
description
"Signature and evidence for messages.";
uses security-footer;
}
}
container message-footer {
presence
"Indicates attempt to secure the entire message.";
description
"Signature and evidence for messages.";
uses security-footer;
}
}
}
/*
* DATA-NODES
*/
container additional-default-headers {
if-feature "publisher";
description
"This container maintains a list of which additional notifications
should use which optional headers if the receiver supports this
specification.";
leaf-list additional-headers {
type optional-header;
description
"This list contains the identities of the optional header types
which are to be included within each message from this
publisher.";
}
list yang-notification-specific-default {
key "yang-module yang-notification-name";
description
"For any included YANG notifications, this list provides
additional optional headers which should be placed within the
container notification-header if the receiver supports this
specification. This list incrementally adds to any headers
indicated within the leaf-list 'additional-headers'.";
leaf yang-module {
type yang:yang-identifier;
description
"Name of the YANG module supported by the publisher.";
}
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leaf yang-notification-name {
type notification-type;
description
"The name of a notification within a YANG module.";
}
leaf-list additional-notification-headers {
type optional-notification-header;
description
"The set of additional default headers which will be sent
for a specific notification.";
}
}
}
}
8. Backwards Compatibility
With this specification, there is no change to YANG's 'notification'
statement
Legacy clients are unaffected, and existing users of [RFC5277],
[RFC7950], and [RFC8040] are free to use current behaviors until all
involved device support this specification.
9. Security Considerations
Certain headers might be computationally complex for a publisher to
deliver. Signatures or encryption are two examples of this. It MUST
be possible to suspend or terminate a subscription due to lack of
resources based on this reason.
Decisions on whether to bundle or not to a receiver are fully under
the purview of the Publisher. A receiver could slow delivery to
existing subscriptions by creating new ones. (Which would result in
the publisher going into a bundling mode.)
10. Acknowledgments
For their valuable comments, discussions, and feedback, we wish to
acknowledge Martin Bjorklund, Einar Nilsen-Nygaard, and Kent Watsen.
11. References
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11.1. Normative References
[I-D.draft-ietf-netconf-subscribed-notifications]
Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A.,
and E. Nilsen-Nygaard, "Custom Subscription to Event
Streams", draft-ietf-netconf-subscribed-notifications-16
(work in progress), August 2019.
[I-D.draft-ietf-netmod-yang-data-ext]
Bierman, A., Bjorklund, M., and K. Watsen, "YANG Data
Structure Extensions", draft-ietf-netmod-yang-data-ext
(work in progress), July 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, .
11.2. Informative References
[I-D.draft-ietf-netconf-restconf-notif]
Voit, Eric., Clemm, Alexander., Tripathy, A., Nilsen-
Nygaard, E., and Alberto. Gonzalez Prieto, "Restconf and
HTTP transport for event notifications", August 2019,
.
[I-D.ietf-netconf-yang-push]
Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto.,
Tripathy, A., Nilsen-Nygaard, E., Bierman, A., and B.
Lengyel, "YANG Datastore Subscription", August 2019,
.
[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,
.
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[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
.
Appendix A. Changes between revisions
(To be removed by RFC editor prior to publication)
v05 - v06
o With SN and YP getting RFC numbers, revisiting this document.
o Changed yang-data to draft-ietf-netmod-yang-data-ext's
'structure'.
o Removed the ability to reference structures other than YANG
notifications.
v04 - v05
o Revision before expiration. Awaiting closure of SN and YP prior
to update.
v03 - v04
o Terminology tweaks.
o Revision before expiration. Awaiting closure of SN prior to
update.
v02 - v03
o Removed the option for an unbundled message. This might be re-
added later for transport efficiency if desired by the WG
o New message structure driven by the desire to put the signature
information at the end.
v01 - v02
o Fixed the yang-data encapsulation container issue
o Updated object definitions to point to RFC-7950 definitions
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o Added headers for module and notification-type.
v00 - v01
o Alternative to 5277 one-way notification added
o Storage of default headers by notification type
o Backwards compatibility
o Capability discovery
o Move to yang-data
o Removed dscp and record-type as common headers. (Record type can
be determined by the namespace of the record contents. Dscp is
useful where applications need internal communications within a
Publisher, but it is unclear as to whether this use case need be
exposed to a receiver.
Appendix B. Issues being worked
(To be removed by RFC editor prior to publication)
A complete JSON document is supposed to be sent as part of Media Type
"application/yang-data+json". As we are sending separate
notifications after each other, we need to choose whether we start
with some extra encapsulation for the very first message pushed, or
if we want a new Media Type for streaming updates.
Improved discovery mechanisms for NETCONF
Need to ensure the proper references exist to a notification
definition driven by RFC-7950 which is acceptable to other eventual
users of this specification.
Appendix C. Subscription Specific Headers
(To be removed by RFC editor prior to publication)
This section discusses a future functional addition which could
leverage this draft. It is included for informational purposes only.
A dynamic subscriber might want to mandate that certain headers be
used for push updates from a publisher. Some examples of this
include a subscriber requesting to:
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o establish this subscription, but just if transport messages
containing the pushed data will be encrypted,
o establish this subscription, but only if you can attest to the
information being delivered in requested notification records, or
o provide a sequence-id for all messages to this receiver (in order
to check for loss).
Providing this type of functionality would necessitate a new revision
of the [I-D.draft-ietf-netconf-subscribed-notifications]'s RPCs and
state change notifications. Subscription specific header information
would overwrite the default headers identified in this document.
Appendix D. Implications to Existing RFCs
(To be removed by RFC editor prior to publication)
YANG one-way exchanges currently use a non-extensible header and
encoding defined in section 4 of RFC-5277. These RFCs MUST be
updated to enable this draft. These RFCs SHOULD be updated to
provide examples
D.1. Implications to RFC-7950
Sections which expose netconf:capability:notification:1.0 are 4.2.10
Sections which provide examples using netconf:notification:1.0 are
7.10.4, 7.16.3, and 9.9.6
D.2. Implications to RFC-8040
Section 6.4 demands use of RFC-5277's netconf:notification:1.0, and
later in the section provides an example.
Authors' Addresses
Eric Voit
Cisco Systems
Email: evoit@cisco.com
Henk Birkholz
Fraunhofer SIT
Email: henk.birkholz@sit.fraunhofer.de
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Andy Bierman
YumaWorks
Email: andy@yumaworks.com
Alexander Clemm
Huawei
Email: ludwig@clemm.org
Tim Jenkins
Cisco Systems
Email: timjenki@cisco.com
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