NETCONF E. Voit
Internet-Draft R. Rahman
Intended status: Standards Track E. Nilsen-Nygaard
Expires: December 20, 2018 Cisco Systems
A. Clemm
Huawei
A. Bierman
YumaWorks
June 18, 2018
RESTCONF and HTTP Transport for Event Notifications
draft-ietf-netconf-restconf-notif-06
Abstract
This document defines RESTCONF, HTTP2, and HTTP1.1 bindings for the
transport of subscription requests and corresponding push updates.
Being subscribed may be either publisher defined event streams or
nodes/subtrees of YANG Datastores.
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 December 20, 2018.
Copyright Notice
Copyright (c) 2018 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
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Dynamic Subscription . . . . . . . . . . . . . . . . . . . . 3
3.1. Transport Connectivity . . . . . . . . . . . . . . . . . 4
3.2. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. RESTCONF RPCs and HTTP Status Codes . . . . . . . . . . . 4
3.4. Call Flow for HTTP2 . . . . . . . . . . . . . . . . . . . 6
3.5. Call flow for HTTP1.1 . . . . . . . . . . . . . . . . . . 8
4. Configured Subscription . . . . . . . . . . . . . . . . . . . 10
4.1. Transport Connectivity . . . . . . . . . . . . . . . . . 10
4.2. Call Flow . . . . . . . . . . . . . . . . . . . . . . . . 11
5. QoS Treatment . . . . . . . . . . . . . . . . . . . . . . . . 12
6. Mandatory JSON and datastore support . . . . . . . . . . . . 12
7. Notification Messages . . . . . . . . . . . . . . . . . . . . 12
8. YANG Tree . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9. YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 13
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
11. Security Considerations . . . . . . . . . . . . . . . . . . . 15
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
13.1. Normative References . . . . . . . . . . . . . . . . . . 17
13.2. Informative References . . . . . . . . . . . . . . . . . 18
Appendix A. RESTCONF over GRPC . . . . . . . . . . . . . . . . . 19
Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 19
B.1. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . 19
B.1.1. Establishing Dynamic Subscriptions . . . . . . . . . 19
B.1.2. Modifying Dynamic Subscriptions . . . . . . . . . . . 22
B.1.3. Deleting Dynamic Subscriptions . . . . . . . . . . . 23
B.2. Configured Subscriptions . . . . . . . . . . . . . . . . 24
B.2.1. Creating Configured Subscriptions . . . . . . . . . . 25
B.2.2. Modifying Configured Subscriptions . . . . . . . . . 27
B.2.3. Deleting Configured Subscriptions . . . . . . . . . . 29
B.3. Subscription State Notifications . . . . . . . . . . . . 30
B.3.1. subscription-started and subscription-modified . . . 30
B.3.2. subscription-completed, subscription-resumed, and
replay-complete . . . . . . . . . . . . . . . . . . . 31
B.3.3. subscription-terminated and subscription-suspended . 31
Appendix C. Changes between revisions . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
Mechanisms to support event subscription and push are defined in
[I-D.draft-ietf-netconf-subscribed-notifications]. Enhancements to
[I-D.draft-ietf-netconf-subscribed-notifications] which enable YANG
datastore subscription and push are defined in
[I-D.ietf-netconf-yang-push]. This document provides a transport
specification for these protocols over RESTCONF [RFC8040] and HTTP.
Driving these requirements is [RFC7923].
The streaming of notifications encapsulating the resulting
information push can be done with either HTTP1.1 [RFC7231] or HTTP2
[RFC7540].
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
The following terms use the definitions from
[I-D.draft-ietf-netconf-subscribed-notifications]: configured
subscription, dynamic subscription, event stream, notification
message, publisher, receiver, subscriber, and subscription.
Other terms reused include datastore, which is defined in [RFC8342],
and HTTP2 stream which maps to the definition of "stream" within
[RFC7540], Section 2.
[ note to the RFC Editor - please replace XXXX within this document
with the number of this document ]
3. Dynamic Subscription
This section provides specifics on how to establish and maintain
dynamic subscriptions over HTTP 1.1 and HTTP2 via signaling messages
transported over RESTCONF [RFC8040]. Subscribing to event streams is
accomplished in this way via a RESTCONF POST into RPCs defined within
[I-D.draft-ietf-netconf-subscribed-notifications] Section 2.4. YANG
datastore subscription is accomplished via augmentations to
[I-D.draft-ietf-netconf-subscribed-notifications] as described within
[I-D.ietf-netconf-yang-push] Section 4.4.
Common across all HTTP based dynamic subscriptions is that a POST
needs to be made against a specific URI on the Publisher.
Subscribers cannot pre-determine the URI against which a subscription
might exist on a publisher, as the URI will only exist after the
"establish-subscription" has been accepted. The subscription URI
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will be determined and sent as part of the response to the
"establish-subscription", and a subsequent POST to this URI will be
done in order to start the flow of notification messages back to the
subscriber. A subscription does not move to the active state as per
Section 2.4.1. of [I-D.draft-ietf-netconf-subscribed-notifications]
until the POST is received.
3.1. Transport Connectivity
For a dynamic subscription, where an HTTP client session doesn't
already exist, a new client session is initiated from the subscriber.
If the subscriber is unsure if HTTP2 is supported by the publisher,
HTTP1.1 will be used for initial messages, and these messages will
include an HTTP version upgrade request as per [RFC7230],
Section 6.7. If a publisher response indicates that HTTP2 is
supported, HTTP2 will be used between subscriber and publisher for
future HTTP interactions as per [RFC7540].
A subscriber SHOULD establish the HTTP session over TLS [RFC5246] in
order to secure the content in transit.
Without the involvement of additional protocols, neither HTTP1.1 nor
HTTP2 sessions by themselves allow for a quick recognition of when
the communication path has been lost with the publisher. Where quick
recognition of the loss of a publisher is required, a subscriber
SHOULD connect over TLS [RFC5246], and use a TLS heartbeat [RFC6520]
to track HTTP session continuity. In the case where a TLS heartbeat
is included, it should be sent just from receiver to publisher. Loss
of the heartbeat MUST result in any subscription related TCP sessions
between those endpoints being torn down. A subscriber can then
attempt to re-establish.
3.2. Discovery
Subscribers can learn what event streams a RESTCONF server supports
by querying the "streams" container of ietf-subscribed-
notification.yang. Subscribers can learn what datastores a RESTCONF
server supports by following [I-D.draft-ietf-netconf-nmda-restconf].
3.3. RESTCONF RPCs and HTTP Status Codes
Specific HTTP responses codes as defined in [RFC7231] section 6 will
indicate the result of RESTCONF RPC requests with publisher. An HTTP
status code of 200 is the proper response to any successful RPC
defined within [I-D.draft-ietf-netconf-subscribed-notifications] or
[I-D.ietf-netconf-yang-push].
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If a publisher fails to serve the RPC request for one of the reasons
indicated in [I-D.draft-ietf-netconf-subscribed-notifications]
Section 2.4.6 or [I-D.ietf-netconf-yang-push] Appendix A, this will
be indicated by "406" status code transported in the HTTP response.
When a "406" status code is returned, the RPC reply MUST include an
"rpc-error" element per [RFC8040] Section 7.1 with the following
parameter values:
o an "error-type" node of "application".
o an "error-tag" node of "operation-failed".
o an "error-app-tag" node with the value being a string that
corresponds to an identity associated with the error, as defined
in [I-D.draft-ietf-netconf-subscribed-notifications] section 2.4.6
for general subscriptions, and [I-D.ietf-netconf-yang-push]
Appendix A.1, for datastore subscriptions. The tag to use depends
on the RPC for which the error occurred. Viable errors for
different RPCs are as follows:
RPC select an identity with a base
---------------------- ------------------------------
establish-subscription establish-subscription-error
modify-subscription modify-subscription-error
delete-subscription delete-subscription-error
kill-subscription kill-subscription-error
resynch-subscription resynch-subscription-error
Each error identity will be inserted as the "error-app-tag" using
JSON encoding following the form <modulename>:<identityname>. An
example of such as valid encoding would be "ietf-subscribed-
notifications:no-such-subscription".
o In case of error responses to an "establish-subscription" or
"modify-subscription" request there is the option of including an
"error-info" node. This node may contain hints for parameter
settings that might lead to successful RPC requests in the future.
Following are the yang-data structures which may be returned:
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establish-subscription returns hints in yang-data structure
---------------------- ------------------------------------
target: event stream establish-subscription-stream-error-info
target: datastore establish-subscription-datastore-error-info
modify-subscription returns hints in yang-data structure
---------------------- ------------------------------------
target: event stream modify-subscription-stream-error-info
target: datastore modify-subscription-datastore-error-info
The yang-data included within "error-info" SHOULD NOT include the
optional leaf "error-reason", as such a leaf would be redundant
with information that is already placed within the
"error-app-tag".
In case of an rpc error as a result of a "delete-subscription", a
"kill-subscription", or a "resynch-subscription" request, no
"error-info" needs to be included, as the "subscription-id" is
the only RPC input parameter and no hints regarding this RPC input
parameters need to be provided.
Note that "error-path" does not need to be included with the "rpc-
error" element, as subscription errors are generally not associated
with nodes in the datastore but with the choice of RPC input
parameters.
3.4. Call Flow for HTTP2
Requests to [I-D.draft-ietf-netconf-subscribed-notifications] or
[I-D.ietf-netconf-yang-push] augmented RPCs are sent on one or more
HTTP2 streams indicated by (a) in Figure 1. A successful "establish-
subscription" will result in an RPC response returned with both a
subscription identifier which uniquely identifies a subscription, as
well as a URI which uniquely identifies the location of subscription
on the publisher. This URI is defined via the "uri" leaf the Data
Model in Section 9.
An HTTP POST is then sent on a logically separate HTTP2 stream (b) to
the URI on the publisher. This initiates to initiate the flow of
notification messages which are sent in HTTP Data frames as a
response to the POST. In the case below, a newly established
subscription has its associated notification messages pushed over
HTTP2 stream (7). These notification messages are placed into a
HTTP2 Data frame (see [RFC7540] Section 6.1).
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+------------+ +------------+
| Subscriber | | Publisher |
|HTTP2 Stream| |HTTP2 Stream|
| (a) (b) | | (a) (b) |
+------------+ +------------+
| RESTCONF POST (RPC:establish-subscription) |
|--------------------------------------------->|
| HTTP 200 OK (ID,URI)|
|<---------------------------------------------|
| (7)HTTP POST (URI) (7)
| |--------------------------------------------->|
| | HTTP 200 OK|
| |<---------------------------------------------|
| | HTTP Data (notif-message)|
| |<---------------------------------------------|
| RESTCONF POST (RPC:modify-subscription) | |
|--------------------------------------------->| |
| | HTTP 200 OK| |
|<---------------------------------------------| |
| | HTTP Data (subscription-modified)|
| |<------------------------------------------(c)|
| | HTTP Data (notif-message)|
| |<---------------------------------------------|
| RESTCONF POST (RPC:delete-subscription) | |
|--------------------------------------------->| |
| | HTTP 200 OK| |
|<---------------------------------------------| |
| | HTTP Headers (end of stream)|
| (/7)<-----------------------------------------(/7)
|
Figure 1: Dynamic with HTTP2
Additional requirements for dynamic subscriptions over HTTP2 include:
o A unique HTTP2 stream MAY be used for each subscription.
o A single HTTP2 stream MUST NOT be used for subscriptions with
different DSCP values.
o All subscription state notifications from a publisher MUST be
returned in a separate HTTP Data frame within the HTTP2 stream
used by the subscription to which the state change refers.
o In addition to an RPC response for a "modify-subscription" RPC
traveling over (a), a "subscription-modified" state change
notification must be sent within HTTP2 stream (b). This allows
the receiver to know exactly when the new terms of the
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subscription have been applied to the notification messages. See
arrow (c).
o Additional RPCs for a particular subscription MUST NOT use the
HTTP2 stream currently providing notification messages
subscriptions.
o An HTTP end of stream message MUST not be sent until all
subscriptions using that HTTP2 stream have completed.
3.5. Call flow for HTTP1.1
The call flow is defined in Figure 2. Requests to
[I-D.draft-ietf-netconf-subscribed-notifications] or
[I-D.ietf-netconf-yang-push] augmented RPCs are sent on a TCP
connection indicated by (a). A successful "establish-subscription"
will result in an RPC response returned with both a subscription
identifier which uniquely identifies a subscription, as well as a URI
which uniquely identifies the location of subscription on the
publisher (b). This URI is defined via the "uri" leaf the Data Model
in Section 9.
An HTTP POST is then sent on a logically separate TCP connection (b)
to the URI on the publisher. This initiates to initiate the flow of
notification messages which are sent in SSE [W3C-20150203] as a
response to the POST.
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+--------------+ +--------------+
| Subscriber | | Publisher |
|TCP connection| |TCP connection|
| (a) (b) | | (a) (b) |
+--------------+ +--------------+
| RESTCONF POST (RPC:establish-subscription) |
|--------------------------------------------->|
| HTTP 200 OK (ID,URI)|
|<---------------------------------------------|
| |HTTP GET (URI) |
| |--------------------------------------------->|
| | HTTP 200 OK|
| |<---------------------------------------------|
| | SSE (notif-message)|
| |<---------------------------------------------|
| RESTCONF POST (RPC:modify-subscription) | |
|--------------------------------------------->| |
| | HTTP 200 OK| |
|<---------------------------------------------| |
| | SSE (subscription-modified)|
| |<------------------------------------------(c)|
| | SSE (notif-message)|
| |<---------------------------------------------|
| RESTCONF POST (RPC:delete-subscription) | |
|--------------------------------------------->| |
| | HTTP 200 OK| |
|<---------------------------------------------| |
| | |
| |
Figure 2: Dynamic with HTTP1.1
Additional requirements for dynamic subscriptions over HTTP1.1
include:
o All subscription state notifications from a publisher MUST be
returned in a separate SSE message used by the subscription to
which the state change refers.
o Subscription RPCs MUST NOT use the TCP connection currently
providing notification messages for that subscription.
o In addition to an RPC response for a "modify-subscription" RPC
traveling over (a), a "subscription-modified" state change
notification must be sent within stream (b). This allows the
receiver to know exactly when the new terms of the subscription
have been applied to the notification messages. See arrow (c).
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Open question, should we just eliminate this possibility of HTTP1.1
for subscriptions? It would make the design simpler.
4. Configured Subscription
With a configured subscription, all information needed to establish a
secure relationship with that receiver is available on the publisher.
With this information, the publisher will establish a secure
transport connection with the receiver and then begin pushing
notification messages to the receiver. Since RESTCONF might not
exist on the receiver, it is not desirable to require that subscribed
content be pushed with any dependency on RESTCONF. Therefore in
place of RESTCONF, an HTTP2 Client connection must be established
with an HTTP2 Server located on the receiver. Notification messages
will then be sent as part of an extended HTTP POST to the receiver.
4.1. Transport Connectivity
Configured subscriptions MUST only be connected over HTTP2 via a
client session initiated from the publisher. Following are the
conditions which MUST be met before establishing a new HTTP2
connection with a receiver:
o a configured subscription has a receiver in the connecting state
as described in [I-D.draft-ietf-netconf-subscribed-notifications],
section 2.5.1.,
o the transport configured for that subscription is HTTP2,
o there are state change notifications or notification messages
pending for that receiver, and
o no HTTP2 transport session exists to that receiver,
If the above conditions are met, then the publisher MUST initiate a
transport session via RESTCONF call home [RFC8071], section 4.1 to
that receiver. HTTP2 only communications must be used as per
[RFC7540], Section 3.3 when the HTTP session over TLS [RFC5246]. and
[RFC7540], Section 3.4 when transporting cleartext over TCP. Note
that a subscriber SHOULD establish over TLS in order to secure the
content in transit.
If the RESTCONF call home fails because the publisher receives
receiver credentials which are subsequently declined per [RFC8071],
Section 4.1, step S5 authentication, then that receiver MUST be
placed into the timeout state.
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If the call home fails to establish for any other reason, the
publisher MUST NOT progress the receiver to the active state.
Additionally, the publisher SHOULD place the receiver into the
timeout state after a predetermined number of either failed call home
attempts or remote transport session termination by the receiver.
4.2. Call Flow
With HTTP2 connectivity established, a POST of each new
"subscription-started" state change notification messages will be
addressed to HTTP augmentation code on the receiver capable of
accepting and acknowledging to subscription state change
notifications. Until the "HTTP 200 OK" at point (c) of Figure 3 for
each the "subscription-started" state change notification, a
publisher MUST NOT progress the receiver to the active state. In
other words, is at point (c) which indicates that the receiver is
ready for the delivery of subscribed content. At this point a
notification-messages including subscribed content may be placed onto
an HTTP2 stream for that subscription.
+------------+ +------------+
| Receiver | | Publisher |
|HTTP2 Stream| |HTTP2 Stream|
| (a) (b) | | (a) (b) |
+------------+ +------------+
|HTTP Post Headers, Data (subscription-started)|
|<---------------------------------------------|
| HTTP 200 OK |
|-------------------------------------------->(c)
| | HTTP Post Headers, Data (notif-message)|
| |<---------------------------------------------|
| | HTTP Data (notif-message)|
| |<---------------------------------------------|
| | HTTP Data (sub-terminated)|
| |<---------------------------------------------|
| |HTTP 200 OK |
| |--------------------------------------------->|
Figure 3: Configured over HTTP2
Additional requirements for configured subscriptions over HTTP2
include:
o A unique HTTP2 stream MAY be used for each subscription.
o A single HTTP2 stream MUST NOT be used for subscriptions with
different DSCP values.
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o All subscription state notifications from a publisher MUST be
returned in a separate HTTP Data frame within the HTTP2 stream
used by the subscription to which the state change refers.
o An HTTP end of stream message MUST not be sent until all
subscriptions using that HTTP2 stream have completed.
5. QoS Treatment
To meet subscription quality of service promises, the publisher MUST
take any existing subscription "dscp" and apply it to the DSCP
marking in the IP header.
In addition, where HTTP2 transport is available to a notification
message queued for transport to a receiver, the publisher MUST:
o take any existing subscription "priority" and copy it into the
HTTP2 stream priority, and
o take any existing subscription "dependency" and map the HTTP2
stream for the parent subscription into the HTTP2 stream
dependency.
6. Mandatory JSON and datastore support
A publisher supporting [I-D.ietf-netconf-yang-push] MUST support the
"operational" datastore as defined by [RFC8342].
The "encode-json" feature of
[I-D.draft-ietf-netconf-subscribed-notifications] is mandatory to
support. This indicates that JSON is a valid encoding for RPCs,
state change notifications, and subscribed content.
7. Notification Messages
Notification messages transported over HTTP will be encoded using
one-way operation schema defined within [RFC5277], section 4.
8. YANG Tree
The YANG model defined in Section 9 has one leaf augmented into four
places of [I-D.draft-ietf-netconf-subscribed-notifications], plus two
identities. As the resulting full tree is large, it will only be
inserted at later stages of this document.
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9. YANG module
This module references
[I-D.draft-ietf-netconf-subscribed-notifications].
<CODE BEGINS> file "ietf-http-subscribed-notifications@2018-06-11.yang"
module ietf-http-subscribed-notifications {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-http-subscribed-notifications";
prefix hsn;
import ietf-subscribed-notifications {
prefix sn;
}
import ietf-inet-types {
prefix inet;
}
organization "IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http:/tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Editor: Eric Voit
<mailto:evoit@cisco.com>
Editor: Alexander Clemm
<mailto:ludwig@clemm.org>
Editor: Reshad Rahman
<mailto:rrahman@cisco.com>";
description
"Defines HTTP variants as a supported transports for subscribed
event notifications.
Copyright (c) 2018 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 XXXX; see the RFC
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itself for full legal notices.";
revision 2018-06-11 {
description
"Initial version";
reference
"RFC XXXX: RESTCONF and HTTP Transport for Event Notifications";
}
identity http2 {
base sn:transport;
base sn:inline-address;
base sn:configurable-encoding;
description
"HTTP2 is used a transport for notification messages and state
change notifications.";
}
identity http1.1 {
base sn:transport;
base sn:inline-address;
base sn:configurable-encoding;
description
"HTTP1.1 is used a transport for notification messages and state
change notifications.";
}
grouping uri {
description
"Provides a reusable description of a URI.";
leaf uri {
type inet:uri;
config false;
description
"Location of a subscription specific URI on the publisher.";
}
}
augment "/sn:establish-subscription/sn:output" {
description
"This augmentation allows HTTP specific parameters for a
response to a publisher's subscription request.";
uses uri;
}
augment "/sn:subscriptions/sn:subscription" {
description
"This augmentation allows HTTP specific parameters to be
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exposed for a subscription.";
uses uri;
}
augment "/sn:subscription-started" {
description
"This augmentation allows HTTP specific parameters to be included
part of the notification that a subscription has started.";
uses uri;
}
augment "/sn:subscription-modified" {
description
"This augmentation allows HTTP specific parameters to be included
part of the notification that a subscription has been modified.";
uses uri;
}
}
<CODE ENDS>
10. IANA Considerations
This document registers the following namespace URI in the "IETF XML
Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-http-subscribed-notifications
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-http-subscribed-notifications
Namespace: urn:ietf:params:xml:ns:yang:ietf-http-subscribed-
notifications
Prefix: hsn
Reference: RFC XXXX: RESTCONF and HTTP Transport for Event
Notifications
11. Security Considerations
The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management transports
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
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RESTCONF layer is HTTPS, and the mandatory-to-implement secure
transport is TLS [RFC5246].
The one new data node introduced 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 this data nodes. These are the subtrees and data
nodes and their sensitivity/vulnerability:
Container: "/subscriptions"
o "uri": leaf will show where subscribed resources might be located
on a publisher. Access control must be set so that only someone
with proper access permissions, and perhaps even HTTP session has
the ability to access this resource.
One or more publishers of configured subscriptions could be used to
overwhelm a receiver which doesn't even support subscriptions. There
are two protections needing support on a publisher. First,
notification messages for configured subscriptions MUST only be
transmittable over encrypted transports. Clients which do not want
pushed content need only terminate or refuse any transport sessions
from the publisher. Second, the HTTP transport augmentation on the
receiver must send an HTTP 200 OK to a subscription started
notification before the publisher starts streaming any subscribed
content.
One or more publishers could overwhelm a receiver which is unable to
control or handle the volume of Event Notifications received. In
deployments where this might be a concern, HTTP2 transport such as
HTTP2) should be selected.
The NETCONF Authorization Control Model [RFC6536] SHOULD be used to
control and restrict authorization of subscription configuration.
12. Acknowledgments
We wish to acknowledge the helpful contributions, comments, and
suggestions that were received from: Ambika Prasad Tripathy, Alberto
Gonzalez Prieto, Susan Hares, Tim Jenkins, Balazs Lengyel, Kent
Watsen, Michael Scharf, and Guangying Zheng.
13. References
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13.1. Normative References
[GRPC] "RPC framework that runs over HTTP2", August 2017,
<https://grpc.io/>.
[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-13
(work in progress), April 2018.
[I-D.ietf-netconf-yang-push]
Clemm, A., Voit, E., Gonzalez Prieto, A., Prasad Tripathy,
A., Nilsen-Nygaard, E., Bierman, A., and B. Lengyel,
"Subscribing to YANG datastore push updates", March 2017,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-yang-push/>.
[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>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
<https://www.rfc-editor.org/info/rfc5277>.
[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>.
[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>.
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[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>.
[RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport
Layer Security (TLS) and Datagram Transport Layer Security
(DTLS) Heartbeat Extension", RFC 6520,
DOI 10.17487/RFC6520, February 2012,
<https://www.rfc-editor.org/info/rfc6520>.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", RFC 6536,
DOI 10.17487/RFC6536, March 2012,
<https://www.rfc-editor.org/info/rfc6536>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>.
[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>.
[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>.
[W3C-20150203]
"Server-Sent Events, World Wide Web Consortium CR CR-
eventsource-20121211", February 2015,
<https://www.w3.org/TR/2015/REC-eventsource-20150203/>.
13.2. Informative References
[I-D.draft-ietf-netconf-netconf-event-notifications]
Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto.,
Nilsen-Nygaard, E., and A. Tripathy, "NETCONF support for
event notifications", May 2018,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-netconf-event-notifications/>.
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[I-D.draft-ietf-netconf-nmda-restconf]
Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "RESTCONF Extensions to Support the Network
Management Datastore Architecture", April 2018,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-nmda-restconf/>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[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>.
[RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
RFC 8071, DOI 10.17487/RFC8071, February 2017,
<https://www.rfc-editor.org/info/rfc8071>.
Appendix A. RESTCONF over GRPC
An initial goal for this document was to support [GRPC] transport
seamlessly without any mapping or extra layering. However there is
an incompatibility of RESTCONF and GRPC. RESTCONF uses HTTP GET, and
GRPC uses HTTP2's POST rather than GET. As GET is used across
RESTCONF for things like capabilities exchange, a seamless mapping
depends on specification changes outside the scope of this document.
If/when GRPC supports GET, or RESTCONF is updated to support POST,
this should be revisited. It is hoped that the resulting fix will be
transparent to this document.
Appendix B. Examples
This section is non-normative. To allow easy comparison, this
section mirrors the functional examples shown with NETCONF over XML
within [I-D.draft-ietf-netconf-netconf-event-notifications]. In
addition, HTTP2 vs HTTP1.1 headers are not shown as the contents of
the JSON encoded objects are identical within.
B.1. Dynamic Subscriptions
B.1.1. Establishing Dynamic Subscriptions
The following figure shows two successful "establish-subscription"
RPC requests as per
[I-D.draft-ietf-netconf-subscribed-notifications]. The first request
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is given a subscription identifier of 22, the second, an identifier
of 23.
+------------+ +-----------+
| Subscriber | | Publisher |
+------------+ +-----------+
| |
|establish-subscription |
|------------------------------>| (a)
| HTTP 200 OK, id#22, URI#1 |
|<------------------------------| (b)
|POST (URI#1) |
|------------------------------>| (c)
| HTTP 200 OK,notif-mesg (id#22)|
|<------------------------------|
| |
| |
|establish-subscription |
|------------------------------>|
| HTTP 200 OK, id#23, URI#2|
|<------------------------------|
|POST (URI#2) |
|------------------------------>|
| |
| |
| notif-mesg (id#22)|
|<------------------------------|
| HTTP 200 OK,notif-mesg (id#23)|
|<------------------------------|
| |
Figure 4: Multiple subscriptions over RESTCONF/HTTP
To provide examples of the information being transported, example
messages for interactions in Figure 4 are detailed below:
POST /restconf/operations/subscriptions:establish-subscription
{
"ietf-subscribed-notifications:input": {
"stream": "NETCONF",
"stream-xpath-filter": "/ex:foo/",
"dscp": "10"
}
}
Figure 5: establish-subscription request (a)
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As publisher was able to fully satisfy the request, the publisher
sends the subscription identifier of the accepted subscription, and
the URI:
HTTP status code - 200
{
"identifier": "22",
"uri": "/subscriptions/22"
}
Figure 6: establish-subscription success (b)
Upon receipt of the successful response, the subscriber POSTs to the
provided URI to start the flow of notification messages. When the
publisher receives this, the subscription is moved to the active
state (c).
POST /restconf/operations/subscriptions/22
Figure 7: establish-subscription subsequent POST
While not shown in Figure 4, if the publisher had not been able to
fully satisfy the request, or subscriber has no authorization to
establish the subscription, the publisher would have sent an RPC
error response. For instance, if the "dscp" value of 10 asserted by
the subscriber in Figure 5 proved unacceptable, the publisher may
have returned:
HTTP status code - 406
{ "ietf-restconf:errors" : {
"error" : [
{
"error-type": "application",
"error-tag": "operation-failed",
"error-severity": "error",
"error-app-tag":
"ietf-subscribed-notifications:dscp-unavailable"
}
]
}
}
Figure 8: an unsuccessful establish subscription
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The subscriber can use this information in future attempts to
establish a subscription.
B.1.2. Modifying Dynamic Subscriptions
An existing subscription may be modified. The following exchange
shows a negotiation of such a modification via several exchanges
between a subscriber and a publisher. This negotiation consists of a
failed RPC modification request/response, followed by a successful
one.
+------------+ +-----------+
| Subscriber | | Publisher |
+------------+ +-----------+
| |
| notification message (id#23)|
|<-----------------------------|
| |
|modify-subscription (id#23) |
|----------------------------->| (d)
| HTTP 406 error (with hint)|
|<-----------------------------| (e)
| |
|modify-subscription (id#23) |
|----------------------------->|
| HTTP 200 OK |
|<-----------------------------|
| |
| notif-mesg (id#23)|
|<-----------------------------|
| |
Figure 9: Interaction model for successful subscription modification
If the subscription being modified in Figure 9 is a datastore
subscription as per [I-D.ietf-netconf-yang-push], the modification
request made in (d) may look like that shown in Figure 10. As can be
seen, the modifications being attempted are the application of a new
xpath filter as well as the setting of a new periodic time interval.
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POST /restconf/operations/subscriptions:modify-subscription
{
"ietf-subscribed-notifications:input": {
"identifier": "23",
"ietf-yang-push:datastore-xpath-filter":
"/interfaces-state/interface/oper-status"
"ietf-yang-push:periodic": {
"ietf-yang-push:period": "500"
}
}
}
Figure 10: Subscription modification request (c)
If the publisher can satisfy both changes, the publisher sends a
positive result for the RPC. If the publisher cannot satisfy either
of the proposed changes, the publisher sends an RPC error response
(e). The following is an example RPC error response for (e) which
includes a hint. This hint is an alternative time period value which
might have resulted in a successful modification:
HTTP status code - 406
{ "ietf-restconf:errors" : {
"error" : [
"error-type": "application",
"error-tag": "operation-failed",
"error-severity": "error",
"error-app-tag": "ietf-yang-push:period-unsupported",
"error-info": {
"ietf-yang-push":
"modify-subscription-datastore-error-info": {
"period-hint": "3000"
}
}
]
}
}
Figure 11: Modify subscription failure with Hint (e)
B.1.3. Deleting Dynamic Subscriptions
The following demonstrates deleting a subscription. This
subscription may have been to either a stream or a datastore.
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POST /restconf/operations/subscriptions:delete-subscription
{
"delete-subscription": {
"identifier": "22"
}
}
Figure 12: Delete subscription
If the publisher can satisfy the request, the publisher replies with
success to the RPC request.
If the publisher cannot satisfy the request, the publisher sends an
error-rpc element indicating the modification didn't work. Figure 13
shows a valid response for existing valid subscription identifier,
but that subscription identifier was created on a different transport
session:
HTTP status code - 406
{
"ietf-restconf:errors" : {
"error" : [
"error-type": "application",
"error-tag": "operation-failed",
"error-severity": "error",
"error-app-tag":
"ietf-subscribed-notifications:no-such-subscription"
]
}
}
Figure 13: Unsuccessful delete subscription
B.2. Configured Subscriptions
Configured subscriptions may be established, modified, and deleted
using configuration operations against the top-level subtree of
[I-D.draft-ietf-netconf-subscribed-notifications] or
[I-D.ietf-netconf-yang-push].
In this section, we present examples of how to manage the
configuration subscriptions using a HTTP2 client.
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B.2.1. Creating Configured Subscriptions
For subscription creation via configuration operations, a RESTCONF
client may send:
POST /restconf/operations/subscriptions/
{
"edit-config": {
"target": {
"running": null
},
"default-operation": "none",
"config": {
"subscriptions": {
"subscription": {
"identifier": "22",
"transport": "HTTP2",
"stream": "NETCONF",
"receivers": {
"receiver": {
"name": "receiver1",
"address": "1.2.3.4"
}
}
}
}
}
}
}
Figure 14: Create a configured subscription
If the request is accepted, the publisher will indicate this. If the
request is not accepted because the publisher cannot serve it, no
configuration is changed. In this case the publisher may reply:
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HTTP status code - 406
{
"ietf-restconf:errors" : {
"error" : [
"error-type": "application",
"error-tag": "resource-denied",
"error-severity": "error",
"error-message": {
"@lang": "en",
"#text": "Temporarily the publisher cannot serve this
subscription due to the current workload."
}
]
}
}
Figure 15: Response to a failed configured subscription establishment
After a subscription has been created and been verified as VALID,
HTTP2 connectivity to each receiver will be established if that
connectivity does not already exist.
The following figure shows the interaction model for the successful
creation of a configured subscription.
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+----------+ +-----------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 |
+----------+ +-----------+ +---------+
| | |
| Capability Exchange | |
|<-------------------------->| |
| | |
| | |
| Edit-config | |
|--------------------------->| |
| RPC Reply: OK | |
|<---------------------------| |
| | Call Home |
| |<-------------->|
| | |
| | subscription- |
| | started |
| |--------------->|
| | |
| | notification |
| | message |
| |--------------->|
Figure 16: Interaction model for configured subscription
establishment
B.2.2. Modifying Configured Subscriptions
Configured subscriptions can be modified using configuration
operations against the top-level container "/subscriptions".
For example, the subscription established in the previous section
could be modified as follows, here a adding a second receiver:
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POST /restconf/operations/subscriptions
{
"edit-config": {
"target": {
"running": null
},
"config": {
"subscriptions": {
"subscription": {
"identifier": "1922",
"receivers": {
"receiver": {
"name": "receiver2",
"address": "1.2.3.5"
}
}
}
}
}
}
}
Figure 17: Modify configured subscription
If the request is accepted, the publisher will indicate success. The
result is that the interaction model described in Figure 16 may be
extended as follows.
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+----------+ +-----------+ +---------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 | | 1.2.3.5 |
+----------+ +-----------+ +---------+ +---------+
| | notification | |
| | message | |
| |--------------->| |
| Edit-config | | |
|--------------------------->| | |
| RPC Reply: OK | | |
|<---------------------------| | |
| | subscription- | |
| | started | |
| |---------------------------->|
| | | |
| | notification | |
| | message | |
| |--------------->| |
| |---------------------------->|
| | | |
Figure 18: Interaction model for configured subscription modification
Note in the above that in the specific example above, modifying a
configured subscription actually resulted in "subscription-started"
notification. And because of existing HTTP2 connectivity, no
additional call home was needed. Also note that if the edit of the
configuration had impacted the filter, a separate modify-subscription
would have been required for the original receiver.
B.2.3. Deleting Configured Subscriptions
Configured subscriptions can be deleted using configuration
operations against the top-level container "/subscriptions".
Deleting the subscription above would result in the following flow
impacting all active receivers.
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+----------+ +-----------+ +---------+ +---------+
|Config Ops| | Publisher | | 1.2.3.4 | | 1.2.3.5 |
+----------+ +-----------+ +---------+ +---------+
| | | |
| | notification | |
| | message | |
| |--------------->| |
| |---------------------------->|
| | | |
| Edit-config | | |
|--------------------------->| | |
| RPC Reply: OK | | |
|<---------------------------| | |
| | subscription- | |
| | terminated | |
| |--------------->| |
| |---------------------------->|
| | | |
Figure 19: Interaction model for configured subscription deletion
B.3. Subscription State Notifications
A publisher will send subscription state notifications according to
the definitions within
[I-D.draft-ietf-netconf-subscribed-notifications]).
B.3.1. subscription-started and subscription-modified
A "subscription-started" encoded in JSON would look like:
{
"ietf-restconf:notification" : {
"eventTime": "2007-09-01T10:00:00Z",
"ietf-subscribed-notifications:subscription-started": {
"identifier": "39",
"transport": "HTTP2",
"stream-xpath-filter": "/ex:foo",
"stream": {
"ietf-netconf-subscribed-notifications" : "NETCONF"
}
}
}
}
Figure 20: subscription-started subscription state notification
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The "subscription-modified" is identical to Figure 20, with just the
word "started" being replaced by "modified".
B.3.2. subscription-completed, subscription-resumed, and replay-
complete
A "subscription-completed" would look like:
{
"ietf-restconf:notification" : {
"eventTime": "2007-09-01T10:00:00Z",
"ietf-subscribed-notifications:subscription-completed": {
"identifier": "39",
}
}
}
Figure 21: subscription-completed notification in JSON
The "subscription-resumed" and "replay-complete" are virtually
identical, with "subscription-completed" simply being replaced by
"subscription-resumed" and "replay-complete".
B.3.3. subscription-terminated and subscription-suspended
A "subscription-terminated" would look like:
{
"ietf-restconf:notification" : {
"eventTime": "2007-09-01T10:00:00Z",
"ietf-subscribed-notifications:subscription-terminated": {
"identifier": "39",
"error-id": "suspension-timeout"
}
}
}
Figure 22: subscription-terminated subscription state notification
The "subscription-suspended" is virtually identical, with
"subscription-terminated" simply being replaced by "subscription-
suspended".
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Appendix C. Changes between revisions
(To be removed by RFC editor prior to publication)
v05 - v06
o JSON examples updated by Reshad.
v04 - v05
o Error mechanisms updated to match embedded RESTCONF mechanisms
o Restructured format and sections of document.
o Added a YANG data model for HTTP specific parameters.
o Mirrored the examples from the NETCONF transport draft to allow
easy comparison.
v03 - v04
o Draft not fully synched to new version of subscribed-notifications
yet.
o References updated
v02 - v03
o Event notification reframed to notification message.
o Tweaks to wording/capitalization/format.
v01 - v02
o Removed sections now redundant with
[I-D.draft-ietf-netconf-subscribed-notifications] and
[I-D.ietf-netconf-yang-push] such as: mechanisms for subscription
maintenance, terminology definitions, stream discovery.
o 3rd party subscriptions are out-of-scope.
o SSE only used with RESTCONF and HTTP1.1 dynamic subscriptions
o Timeframes for event tagging are self-defined.
o Clean-up of wording, references to terminology, section numbers.
v00 - v01
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o Removed the ability for more than one subscription to go to a
single HTTP2 stream.
o Updated call flows. Extensively.
o SSE only used with RESTCONF and HTTP1.1 dynamic subscriptions
o HTTP is not used to determine that a receiver has gone silent and
is not Receiving Event Notifications
o Many clean-ups of wording and terminology
Authors' Addresses
Eric Voit
Cisco Systems
Email: evoit@cisco.com
Reshad Rahman
Cisco Systems
Email: rrahman@cisco.com
Einar Nilsen-Nygaard
Cisco Systems
Email: einarnn@cisco.com
Alexander Clemm
Huawei
Email: ludwig@clemm.org
Andy Bierman
YumaWorks
Email: andy@yumaworks.com
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