| NETCONF | E. Voit |
| Internet-Draft | E. Nilsen-Nygaard |
| Intended status: Standards Track | Cisco Systems |
| Expires: November 19, 2018 | A. Clemm |
| Huawei | |
| A. Bierman | |
| YumaWorks | |
| May 18, 2018 |
RESTCONF and HTTP Transport for Event Notifications
draft-ietf-netconf-restconf-notif-05
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.
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 November 19, 2018.
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 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.
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].
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.
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 ]
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. There subscription URI 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 become ACTIVE as per Section 2.4.1. of [I-D.draft-ietf-netconf-subscribed-notifications] until the POST is received.
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.
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].
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].
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:
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".
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.
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).
+------------+ +------------+
| 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:
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.
+--------------+ +--------------+
| 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:
Open question, should we just eliminate this possibility of HTTP1.1 for subscriptions? It would make the design simpler.
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.
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 estabishing a new HTTP2 connection with a 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.
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.
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 acknowleding 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:
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:
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.
Notification messages transported over HTTP will be encoded using one-way operation schema defined within [RFC5277], section 4.
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.
This module references [I-D.draft-ietf-netconf-subscribed-notifications].
<CODE BEGINS> file "ietf-http-subscribed-notifications@2018-05-01.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-yang-types {
prefix yang;
}
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: Einar Nilsen-Nygaard
<mailto:einarnn@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
itself for full legal notices.";
revision 2018-05-01 {
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 {
config false;
type yang:uri;
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/sn:target" {
description
"This augmentation allows HTTP specific parameters to be
exposed for a subscription.";
uses uri;
}
augment "/sn:subscription-started/sn:target" {
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/sn:target" {
description
"This augmentation allows HTTP specific parameters to be included
part of the notification that a subscription has been modified.";
uses uri;
}
/* need to add a constraint that HTTP1.1 not allowed for
configured subscriptions - needs the right syntax below...
augment "sn:subscriptions/sn:subscription/sn:protocol" {
when '../sn:configured-subscription-state'
must ' protocol <> "http1.1"' {
error-message "HTTP1.1 not used for configured subscriptions";
}
}
*/
}
<CODE ENDS>
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
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 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"
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.
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.
| [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. |
| [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. |
| [RFC7231] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014. |
| [RFC7923] | Voit, E., Clemm, A. and A. Gonzalez Prieto, "Requirements for Subscription to YANG Datastores", RFC 7923, DOI 10.17487/RFC7923, June 2016. |
| [RFC8071] | Watsen, K., "NETCONF Call Home and RESTCONF Call Home", RFC 8071, DOI 10.17487/RFC8071, February 2017. |
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.
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.
The following figure shows two successful "establish-subscription" RPC requests as per [I-D.draft-ietf-netconf-subscribed-notifications]. The first request 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)|
|<------------------------------|
| |
| |
|stablish-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
{
"establish-subscription": {
"stream": {
"ietf-netconf-subscribed-notifications" : "NETCONF"
},
"stream-xpath-filter": "/ex:foo/",
"dscp": "10"
}
}
Figure 5: establish-subscription request (a)
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 becomes ACTIVE (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
The subscriber can use this information in future attempts to establish a subscription.
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.
POST /restconf/operations/subscriptions:modify-subscription
{
"modify-subscription": {
"identifier": "23",
{
"ietf-yang-push": "datastore-xpath-filter":
"/interfaces-state/interface/oper-status"
},
{
"ietf-yang-push": "periodic": "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": "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)
The following demonstrates deleting a subscription. This subscription may have been to either a stream or a datastore.
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
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.
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:
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.
+----------+ +-----------+ +---------+
|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
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:
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.
+----------+ +-----------+ +---------+ +---------+
|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.
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.
+----------+ +-----------+ +---------+ +---------+
|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
A publisher will send subscription state notifications according to the definitions within [I-D.draft-ietf-netconf-subscribed-notifications]).
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
The "subscription-modified" is identical to Figure 20, with just the word "started" being replaced by "modified".
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".
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".
(To be removed by RFC editor prior to publication)
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