< draft-ietf-netconf-restconf-notif-00.txt   draft-ietf-netconf-restconf-notif-01.txt >
NETCONF E. Voit NETCONF E. Voit
Internet-Draft A. Clemm Internet-Draft A. Clemm
Intended status: Informational A. Tripathy Intended status: Standards Track A. Gonzalez Prieto
Expires: February 27, 2017 E. Nilsen-Nygaard Expires: April 2, 2017 A. Tripathy
A. Gonzalez Prieto E. Nilsen-Nygaard
Cisco Systems Cisco Systems
August 26, 2016 A. Bierman
YumaWorks
September 29, 2016
Restconf and HTTP Transport for Event Notifications Restconf and HTTP Transport for Event Notifications
draft-ietf-netconf-restconf-notif-00 draft-ietf-netconf-restconf-notif-01
Abstract Abstract
This document defines Restconf, HTTP, and HTTP2 bindings for the This document defines Restconf, HTTP2, and HTTP1.1 bindings for the
transport Subscription requests and corresponding push updates. transport Subscription requests and corresponding push updates.
Being subscribed may be both Event Notifications and YANG Datastores. Being subscribed may be both Event Notifications and YANG Datastores.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 27, 2017. This Internet-Draft will expire on April 2, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 13 skipping to change at page 2, line 14
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Mechanisms for Subscription Establishment and Maintenance 4 3.1. Mechanisms for Subscription Establishment and Maintenance 4
3.2. Subscription Multiplexing . . . . . . . . . . . . . . . . 6 3.2. Dynamic YANG Subscription with RESTCONF control . . . . . 5
3.3. Push Data Stream and Transport Mapping . . . . . . . . . 7 3.3. Subscription Multiplexing . . . . . . . . . . . . . . . . 8
3.4. Stream Discovery . . . . . . . . . . . . . . . . . . . . 12 3.4. Encoded Subscription and Event Notification Examples . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 12 3.5. Stream Discovery . . . . . . . . . . . . . . . . . . . . 14
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 4. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Normative References . . . . . . . . . . . . . . . . . . 14 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2. Informative References . . . . . . . . . . . . . . . . . 14 6.1. Normative References . . . . . . . . . . . . . . . . . . 15
6.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Proxy YANG Subscription when the Subscriber and Appendix A. Proxy YANG Subscription when the Subscriber and
Receiver are different . . . . . . . . . . . . . . . 15 Receiver are different . . . . . . . . . . . . . . . 17
Appendix B. End-to-End Deployment Guidance . . . . . . . . . . . 16 Appendix B. End-to-End Deployment Guidance . . . . . . . . . . . 17
B.1. Call Home . . . . . . . . . . . . . . . . . . . . . . . . 16 B.1. Call Home . . . . . . . . . . . . . . . . . . . . . . . . 17
B.2. TLS Heartbeat . . . . . . . . . . . . . . . . . . . . . . 16 B.2. TLS Heartbeat . . . . . . . . . . . . . . . . . . . . . . 18
Appendix C. Issues being worked and resolved . . . . . . . . . . 17 Appendix C. Issues being worked and resolved . . . . . . . . . . 18
C.1. Unresolved Issues . . . . . . . . . . . . . . . . . . . . 17 C.1. Unresolved Issues . . . . . . . . . . . . . . . . . . . . 18
C.2. Agreement in principal . . . . . . . . . . . . . . . . . 17 C.2. Agreement in principal . . . . . . . . . . . . . . . . . 18
C.3. Resolved Issues . . . . . . . . . . . . . . . . . . . . . 18 C.3. Resolved Issues . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Appendix D. Changes between revisions . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
Mechanisms to support Event subscription and push are defined in Mechanisms to support Event subscription and push are defined in
[rfc5277bis]. Enhancements to [rfc5277bis] which enable YANG [rfc5277bis]. Enhancements to [rfc5277bis] which enable YANG
Datastore subscription and push are defined in [yang-push]. This Datastore subscription and push are defined in [yang-push]. This
document provides a transport specification for these Restconf and document provides a transport specification for these protocols over
HTTP. This has been driven by Requirements for subscriptions to YANG Restconf and HTTP. Driving these requirements is [RFC7923].
datastores are defined in[RFC7923] .
Beyond based transport bindings, there are benefits which can be The streaming of Subscription Event Notifications has synergies with
realized when transporting updates directly HTTP/2[RFC7540] which can HTTP2 streams. Benefits which can be realized when transporting
be realized via an implementation of this transport specification events directly HTTP2 [RFC7540] include:
including:
o Subscription multiplexing over independent HTTP/2 streams o Elimination of head-of-line blocking
o Stream prioritization and stream dependencies o Weighting and proportional dequeuing of Events from different
subscriptions
o Flow control on independent streams o Explicit precedence in subscriptions so that events from one
subscription must be sent before another dequeues
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Configured Subscription: a Subscription installed via a configuration Configured Subscription: a Subscription installed via a configuration
interface which persists across reboots. interface which persists across reboots.
Data Node: An instance of management information in a datastore.
Data Node Update: A data item containing the current value/property
of a Data Node at the time the Data Node Update was created.
Dynamic Subscription: a Subscription negotiated between Subscriber Dynamic Subscription: a Subscription negotiated between Subscriber
and Publisher via create, establish, modify, and delete RPC control and Publisher via create, establish, modify, and delete RPC signaling
plane signaling messages. messages.
Event: an occurrence of something that may be of interest. (e.g., a Event: an occurrence of something that may be of interest. (e.g., a
configuration change, a fault, a change in status, crossing a configuration change, a fault, a change in status, crossing a
threshold, status of a flow, or an external input to the system.) threshold, status of a flow, or an external input to the system.)
Event Notification: a set of information intended for a Receiver Event Notification: a set of information intended for a Receiver
indicating that one or more Event(s) have occurred. Details of the indicating that one or more Event(s) have occurred. Details of the
Event(s) may be included within. Event(s) may be included within.
Event Stream: a continuous, ordered set of Events grouped under an Event Stream: a continuous, ordered set of Events grouped under an
skipping to change at page 4, line 27 skipping to change at page 4, line 27
same. A Subscription ends with a subscription-terminated same. A Subscription ends with a subscription-terminated
notification, or by a loss of transport connectivity. notification, or by a loss of transport connectivity.
2. Configured Subscription: Receiver(s) are specified on Publisher 2. Configured Subscription: Receiver(s) are specified on Publisher
in startup and running config. Subscription is not terminated in startup and running config. Subscription is not terminated
except via an operations interface. (Subscriptions may be except via an operations interface. (Subscriptions may be
Suspended, with no Event Notifications sent however.) Suspended, with no Event Notifications sent however.)
3. Proxy Subscription: Subscriber and Receiver are different. 3. Proxy Subscription: Subscriber and Receiver are different.
Subscription ends when a Subscription End-time is reached, or the Subscription ends when a Subscription End-time is reached, or the
Publisher process is restarted. The real difference between 2 Publisher process is restarted. A key difference between this
and 3 is that configuration requests are made to RPCs which might and configured subscriptions (#2) is that configuration requests
evaluate run-time conditions much like in 1. Typically direct are made to RPCs which might evaluate run-time conditions much
configuration via 2 will not go through the same sort of capacity like in (#1). Typically direct configuration via (#2) will not
and validation checks seen in 1. go through the same sort of capacity and validation checks seen
in (#1).
The first two are described in this section. The third is described The first two models are described in this section. The third is
in Appendix A. This third option can be moved into the body of this described in Appendix A. This third model will be moved into the
specification should the IETF community desire. In theory, all three body of this specification should the IETF community desire. In
models may be intermixed in a single deployment. theory, all three models may be intermixed in a single deployment.
.---------------. .---------------.
| Publisher | | Publisher |
'---------------' '---------------'
^ ^ | ^ ^ ^ | ^
| | | | | | | |
.-----Restconf----' | | '-----Restconf----. .-----Restconf----' | | '-----Restconf----.
| .-----' '-HTTP-. | | .-----' '-HTTP-. |
V | V | V | V |
.-------------. .------------. .----------. .------------. .-------------. .------------. .----------. .------------.
| Subscriber+ | | Operations | | Receiver | | Subscriber | | Subscriber+ | | Operations | | Receiver | | Subscriber |
| Receiver | | /Config | '----------' '------------' | Receiver | | /Config | '----------' '------------'
'-------------' '------------' ^ ^ ^ '-------------' '------------' ^ ^ ^
^ (out of scope) : : : ^ (out of scope) : : :
: ^ : :....Model 3....: : ^ : :...Model #3....:
Model 1 :...Model 2...: (out of scope) Model #1 :..Model #2...: (out of scope)
3.1.1. Dynamic YANG Subscription over RESTCONF Figure 1: Subscription Models
Dynamic Subscriptions for both [rfc5277bis] and its [rfc5277bis] 3.2. Dynamic YANG Subscription with RESTCONF control
Dynamic Subscriptions for both [rfc5277bis] and its [yang-push]
augmentations are configured and managed via signaling messages augmentations are configured and managed via signaling messages
transported over Restconf. Extending the paradigm of [restconf] transported over [restconf]. These interactions will be accomplished
section 6.3.1, it must support the encoding and transport query via a Restconf POST into RPCs located on the Publisher. HTTP
parameters corresponding to the YANG model for subscriptions defined responses codes will indicate the results of the interaction with the
in [RFC5277bis] and [Yang-Push]. These interactions will be Publisher. An HTTP status code of 200 is the proper response to a
accomplished via the typical[restconf] POST into Success of the RPC successful <establish-subscription> RPC call. The successful
interaction will be indicated by HTTP status codes of 20x being <establish-subscription> will result in a HTTP message with returned
subscription URI on a logically separate mechanism than was used for
the original Restconf POST. This mechanism would be via a parallel
TCP connection in the case of HTTP 1.x, or in the case of HTTP2 via a
separate HTTP stream within the HTTP connection. When a being
returned by the Publisher, failure will be indicated by error codes returned by the Publisher, failure will be indicated by error codes
transported in payload, as well as the return of negotiation transported in payload, as well as the return of negotiation
parameters. parameters.
Once established, streaming Event Notifications are then delivered Once established, streaming Event Notifications are then delivered
via Restconf SSE (assuming issue RT8 is reloved, see appx). As they via SSE for HTTP1.1 and via HTTP Data for HTTP2.
are successfully received, HTTP status codes of 20x will be returned
by the Receiver.
3.1.2. Configured Subscription over HTTP 3.2.1. Call Flow for HTTP2
With a Configured Subscription, all information needed to establish a Requests to [yang-push] augmented RPCs are sent on one or more HTTP2
secure relationship with that Receiver is configured on the streams indicated by (a) in Figure 2. Event Notifications related to
Publisher. With this information, the Publisher will establish a a single subscription are pushed on a unique logical channel (b). In
secure transport connection with the Receiver and then begin pushing the case below, a newly established subscription has its events
the Event Notifications to the Receiver. Since Restconf might not pushed over HTTP2 stream (7).
exist on the Receiver, it is not desirable to require that such Event
Notifications be pushed via Restconf. Nor is there value which
Restconf provides on top of HTTP. Therefore in place of Restconf, a
TLS secured HTTP Client connection must be established with an HTTP
Server located on the Receiver. Event Notifications will then be
sent via HTTP Post messages to the Receiver.
Post messages will be addressed to HTTP augmentation code on the +------------+ +------------+
Receiver capable of accepting and responding to Event Notifications. | Subscriber | | Publisher |
Some Post messages must include the URI for the subscribed resource. |HTTP2 Stream| |HTTP2 Stream|
This URI can be retained for operational tracking and debugging use | (a) (b) | | (a) (b) |
by the Receiver. +------------+ +------------+
| Restconf POST (RPC:establish-subscription) |
|--------------------------------------------->|
| HTTP 200 OK (URI)|
|<---------------------------------------------|
| (7)HTTP POST (URI) (7)
| |--------------------------------------------->|
| | HTTP 200 OK|
| |<---------------------------------------------|
| | HTTP Data (event-notif)|
| |<---------------------------------------------|
| Restconf POST (RPC:modify-subscription) | |
|--------------------------------------------->| |
| | HTTP 200 OK| |
|<---------------------------------------------| |
| | HTTP Data (subscription-modified)|
| |<---------------------------------------------|
| | HTTP Data (event-notif)|
| |<---------------------------------------------|
| Restconf POST (RPC:delete-subscription) | |
|--------------------------------------------->| |
| | HTTP 200 OK| |
|<---------------------------------------------| |
| | HTTP Headers (end of stream)|
| (/7)<-----------------------------------------(/7)
|
After successful receipt of an initial Event Notification for a Figure 2: Dynamic with HTTP2
particular Subscription, the Reciever should reply back with an HTTP
status code of 201 (Created). Further successful receipts should
result in the return of code of 200 (Accepted). To ensure the
Receiver always has the URI, it should also be sent in the next push
update for a Subscription after any status code of 201 (Created) has
been returned from the Receiver. At any point, receipt of any status
codes from 300-510 with the exception of 408 (Request Timeout) should
result in either the movement of the Subscription to the suspended
state, or cause the HTTP session to fail (need to determine
appropriate action). A sequential series of multiple 408 exceptions
should also drive the Subscription to a suspended state. If a
suspension occurs, a POST including a subscription Id and URI post-
pended with a Suspended indication (format tbd) must be sent.
Figure 2 depicts this message flow. 3.2.2. Call flow for HTTP1.1
+-----------+ +----------+ Requests to [yang-push] RPCs are sent on the TCP connection indicated
| Publisher | | Receiver | by (a). Event Notifications are pushed on a separate connection (b).
+-----------+ +----------+ This connection (b) will be used for all Event Notifications across
|<--------------TLS------------>| all subscriptions.
| |
|HTTP POST (Sub ID, data1) |
|------------------------------>|
| HTTP 201 (Created)|
|<------------------------------|
|HTTP POST (Sub ID, URI, data2) |
|------------------------------>|
| HTTP 200 (OK)|
|<------------------------------|
| data3 |
|<----------------------------->|
If HTTP/2 transport is available to a Receiver, the Publisher should +--------------+ +--------------+
also: | Subscriber | | Publisher |
|TCP connection| |TCP connection|
| (a) (b) | | (a) (b) |
+--------------+ +--------------+
| Restconf POST (RPC:establish-subscription) |
|--------------------------------------------->|
| HTTP 200 OK (URI)|
|<---------------------------------------------|
| |HTTP GET (URI) |
| |--------------------------------------------->|
| | HTTP 200 OK|
| |<---------------------------------------------|
| | SSE (event-notif)|
| |<---------------------------------------------|
| Restconf POST (RPC:modify-subscription) | |
|--------------------------------------------->| |
| | HTTP 200 OK| |
|<---------------------------------------------| |
| | SSE (subscription-modified)|
| |<---------------------------------------------|
| | SSE (event-notif)|
| |<---------------------------------------------|
| Restconf POST (RPC:delete-subscription) | |
|--------------------------------------------->| |
| | HTTP 200 OK| |
|<---------------------------------------------| |
| | |
| |
o point individual Event Notifications to a unique HTTP/2 stream for Figure 3: Dynamic with HTTP1.1
that Subscription,
o take any subscription-priority and provision it into the HTTP/2 3.2.3. Configured Subscription over HTTP2
stream priority, and
o take any subscription-dependency and provision it into the HTTP/2 With a Configured Subscription, all information needed to establish a
stream dependency. 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 the
Event Notifications to the Receiver. Since Restconf might not exist
on the Receiver, it is not desirable to require that such Event
Notifications be pushed with any dependency on Restconf. Nor is
there value which Restconf provides on top of HTTP. Therefore in
place of Restconf, a TLS secured HTTP2 Client connection must be
established with an HTTP2 Server located on the Receiver. Event
Notifications will then be sent as part of an extended HTTP POST to
the Receiver.
3.2. Subscription Multiplexing POST messages will be addressed to HTTP augmentation code on the
Receiver capable of accepting and responding to Event Notifications.
The first POST message must be a subscription-started notification.
Push update notifications must not be sent until the receipt of an
HTTP 200 OK for this initial notification. The 200 OK will indicate
that the Receiver is ready for Event Notifications. At this point a
Subscription must be allocated its own HTTP2 stream. Figure 4
depicts this message flow.
When pushed directly over HTTP/2, it is expected that the Event +------------+ +------------+
Notifications from a single Subscription will be allocated a separate | Receiver | | Publisher |
HTTP/2 stream. This will enable multiplexing, and address issues of |HTTP2 Stream| |HTTP2 Stream|
Head-of-line blocking with different priority Subscriptions. | (a) (b) | | (a) (b) |
+------------+ +------------+
| HTTP Post Headers, Data (sub-start, SubID)|
|<---------------------------------------------|
| HTTP 200 OK |
|--------------------------------------------->|
| | HTTP Post Headers, Data (event-notif)|
| |<---------------------------------------------|
| | HTTP Data (event-notif)|
| |<---------------------------------------------|
| | HTTP Data (sub-terminate)|
| |<---------------------------------------------|
| |HTTP 200 OK |
| |--------------------------------------------->|
When pushed via Restconf over HTTP/2, different Subscriptions will Figure 4: Configured over HTTP2
not be mapped to independent HTTP/2 streams. When Restconf specifies
this mapping, support may be appended on top of this specification.
With or without independent queueing of multiplexed subscriptions, it As the HTTP2 transport is available to the Receiver, the Publisher
is possible that updates might be delivered in a different sequence should:
than generated. Reasons for this might include (but are not limited
to):
o replay of pushed updates o take any subscription-priority and copy it into the HTTP2 stream
priority, and
o take a subscription-dependency if it has been provided and map the
HTTP2 stream for the parent subscription into the HTTP2 stream
dependency.
3.3. Subscription Multiplexing
It is possible that updates might be delivered in a different
sequence than generated. Reasons for this might include (but are not
limited to):
o replay of pushed updates
o temporary loss of transport connectivity, with update buffering o temporary loss of transport connectivity, with update buffering
and different dequeuing priorities per Subscription and different dequeuing priorities per Subscription
o population, marshalling and bundling of independent Subscription o population, marshalling and bundling of independent Subscription
Updates, and Updates, and
o parallel HTTP1.1 sessions Therefore each Event Notification will include a millisecond level
Therefore each Event Notification will include a microsecond level
timestamp to ensure that a Receiver understands the time when a that timestamp to ensure that a Receiver understands the time when a that
update was generated. Use of this timestamp can give an indication update was generated. Use of this timestamp can give an indication
of the state of objects at a Publisher when state-entangled of the state of objects at a Publisher when state-entangled
information is received across different subscriptions. The use of information is received across different subscriptions. The use of
the latest Event Notification timestamp for a particular object the latest Event Notification timestamp for a particular object
update can introduce errors. So when state-entangled updates have update can introduce errors. So when state-entangled updates have
inconsistent object values and temporally close timestamps, a inconsistent object values and temporally close timestamps, a
Receiver might consider performing a 'get' to validate the current Receiver might consider performing a GET to validate the current
state of a Publisher. state of a Publisher.
3.3. Push Data Stream and Transport Mapping 3.4. Encoded Subscription and Event Notification Examples
Transported updates will contain data for one or more Event Transported updates will contain context data for one or more Event
Notifications. Each transported Event Notification will contain Notifications. Each transported Event Notification will contain
several parameters: several parameters:
o A Subscription ID correlator 3.4.1. Restconf Subscription and Events over HTTP1.1
o Event Notification(s) . (Note 1: These must be filtered per access
control rules to contain only data that the Subscriber is
authorized to see. Note 2: these Event Notifications might be
Data Node Update(s).)
o A timestamp indication when the Event Notification was generated
on the Publisher. The timestamp must correspond to a time where
any Data Nodes included in the Update held the values/state
indicated within the Update.
3.3.1. Subscription and Updates via Restconf
Subscribers can dynamically learn whether a RESTCONF server supports Subscribers can dynamically learn whether a RESTCONF server supports
various types of Event or Yang datastore subscription capabilities. various types of Event or Yang datastore subscription capabilities.
This is done by issuing an HTTP request OPTIONS, HEAD, or GET on the This is done by issuing an HTTP request OPTIONS, HEAD, or GET on the
stream. Some examples building upon the existing RESTCONF mechanisms stream. Some examples building upon the Call flow for HTTP1.1 from
are below: Section 3.2.2 are:
GET /restconf/data/ietf-restconf-monitoring:restconf-state/ GET /restconf/data/ietf-restconf-monitoring:restconf-state/
streams/stream=yang-push HTTP/1.1 streams/stream=yang-push HTTP/1.1
Host: example.com Host: example.com
Accept: application/yang.data+xml Accept: application/yang.data+xml
If the server supports it, it may respond If the server supports it, it may respond
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/yang.api+xml Content-Type: application/yang.api+xml
<stream xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring"> <stream xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring">
<name>yang-push</name> <name>yang-push</name>
<description>Yang push stream</description> <description>Yang push stream</description>
<access> <access>
<encoding>xml</encoding> <encoding>xml</encoding>
<location>https://example.com/streams/yang-push-xml <location>https://example.com/streams/yang-push-xml
</location> </location>
</access> </access>
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If the server does not support any form of subscription, it may If the server does not support any form of subscription, it may
respond respond
HTTP/1.1 404 Not Found HTTP/1.1 404 Not Found
Date: Mon, 25 Apr 2012 11:10:30 GMT Date: Mon, 25 Apr 2012 11:10:30 GMT
Server: example-server Server: example-server
Subscribers can determine the URL to receive updates by sending an Subscribers can determine the URL to receive updates by sending an
HTTP GET as a request for the "location" leaf with the stream list HTTP GET as a request for the "location" leaf with the stream list
entry.The stream to use for may be selected from the Event Stream entry. The stream to use for may be selected from the Event Stream
list provided in the capabilities exchange. Note that different list provided in the capabilities exchange. Note that different
encodings are supporting using different Event Stream locations. For encodings are supporting using different Event Stream locations. For
example, the Subscriber might send the following request: example, the Subscriber might send the following request:
GET /restconf/data/ietf-restconf-monitoring:restconf-state/ GET /restconf/data/ietf-restconf-monitoring:restconf-state/
streams/stream=yang-push/access=xml/location HTTP/1.1 streams/stream=yang-push/access=xml/location HTTP/1.1
Host: example.com Host: example.com
Accept: application/yang.data+xml Accept: application/yang.data+xml
The Publisher might send the following response: The Publisher might send the following response:
skipping to change at page 9, line 22 skipping to change at page 11, line 4
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/yang.api+xml Content-Type: application/yang.api+xml
<location <location
xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring"> xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring">
https://example.com/streams/yang-push-xml https://example.com/streams/yang-push-xml
</location> </location>
To subscribe and start receiving updates, the subscriber can then To subscribe and start receiving updates, the subscriber can then
send an HTTP GET request for the URL returned by the Publisher in the send an HTTP GET request for the URL returned by the Publisher in the
request above. The accept header must be "text/event-stream". The request above. The accept header must be "text/event-stream". The
Publisher uses the Server Sent Events[W3C-20150203] transport Publisher uses the Server Sent Events [W3C-20150203] transport
strategy to push filtered Event Notifications from the Event stream,. strategy to push filtered Event Notifications from the Event stream.
The Publisher MUST support individual parameters within the POST The Publisher MUST support individual parameters within the POST
request body for all the parameters of a subscription. The only request body for all the parameters of a subscription. The only
exception is the encoding, which is embedded in the URI. An example exception is the encoding, which is embedded in the URI. An example
of this is: of this is:
// subtree filter = /foo // subtree filter = /foo
// periodic updates, every 5 seconds // periodic updates, every 5 seconds
POST /restconf/operations/ietf-event-notifications: POST /restconf/operations/ietf-event-notifications:
establish-subscription HTTP/1.1 establish-subscription HTTP/1.1
skipping to change at page 10, line 46 skipping to change at page 12, line 46
"error-info": { "error-info": {
"datastore-push:supported-subscription": { "datastore-push:supported-subscription": {
"subtree-filter": [null] "subtree-filter": [null]
} }
} }
} }
} }
} }
The following is an example of a pushed Event Notification data for The following is an example of a pushed Event Notification data for
the subscription above. It contains a subtree with root foo that the Subscription above. It contains a subtree with root foo that
contains a leaf called bar: contains a leaf called bar:
XML encoding representation: XML encoding representation:
<?xml version="1.0" encoding="UTF-8"?> <?xml version="1.0" encoding="UTF-8"?>
<notification xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf"> <notification xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
<subscription-id xmlns="urn:ietf:params:xml:ns:restconf: <subscription-id xmlns="urn:ietf:params:xml:ns:restconf:
datastore-push:1.0"> datastore-push:1.0">
my-sub my-sub
</subscription-id> </subscription-id>
<eventTime>2015-03-09T19:14:56Z</eventTime> <eventTime>2015-03-09T19:14:56.23Z</eventTime>
<datastore-contents xmlns="urn:ietf:params:xml:ns:restconf: <datastore-contents xmlns="urn:ietf:params:xml:ns:restconf:
datastore-push:1.0"> datastore-push:1.0">
<foo xmlns="http://example.com/yang-push/1.0"> <foo xmlns="http://example.com/yang-push/1.0">
<bar>some_string</bar> <bar>some_string</bar>
</foo> </foo>
</datastore-contents> </datastore-contents>
</notification> </notification>
Or with the equivalent YANG over JSON encoding representation as Or with the equivalent YANG over JSON encoding representation as
defined in[yang-json] : defined in [RFC7951]:
{ {
"ietf-restconf:notification": { "ietf-restconf:notification": {
"datastore-push:subscription-id": "my-sub", "datastore-push:subscription-id": "my-sub",
"eventTime": "2015-03-09T19:14:56Z", "eventTime": "2015-03-09T19:14:56.23Z",
"datastore-push:datastore-contents": { "datastore-push:datastore-contents": {
"example-mod:foo": { "bar": "some_string" } "example-mod:foo": { "bar": "some_string" }
} }
} }
} }
To modify a Subscription, the subscriber issues another POST request To modify a Subscription, the subscriber issues another POST request
on the provided URI using the same subscription-id as in the original on the provided URI using the same subscription-id as in the original
request. For example, to modify the update period to 10 seconds, the request. For example, to modify the update period to 10 seconds, the
subscriber may send: subscriber may send:
POST /restconf/operations/ietf-event-notifications: POST /restconf/operations/ietf-event-notifications:
modify-subscription HTTP/1.1 modify-subscription HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/yang-data+json Content-Type: application/yang-data+json
{ {
"ietf-event-notifications:input" : { "ietf-event-notifications:input" : {
?subscription-id?: 100, ?subscription-id?: 100,
?period" : 10, ?period" : 10
} }
} }
To delete a Subscription, the Subscriber issues a DELETE request on To delete a Subscription, the Subscriber issues a DELETE request on
the provided URI using the same subscription-id as in the original the provided URI using the same subscription-id as in the original
request request
DELETE /mystreams/yang-push?subscription-id=my-sub 3.4.2. Event Notification over HTTP2
3.3.2. Subscription and Updates directly via HTTP The basic encoding will look as below. It will consists of a JSON
representation wrapped in an HTTP2 header.
For any version of HTTP, the basic encoding will look as below. It HyperText Transfer Protocol 2
consists of a JSON representation wrapped in an HTTP header. Stream: HEADERS, Stream ID: 5
Header: :method: POST
Stream: HEADERS, Stream ID: 5
POST (IP+Port) HTTP/1.1
From: (Identifier for Network Element)
User-Agent: (CiscoYANGPubSub/1.0)
Content-Type: multipart/form-data
Content-Length: (determined runtime)
{ {
"ietf-yangpush:notification": { "ietf-yangpush:notification": {
"datastore-push:subscription-id": "my-sub", "datastore-push:subscription-id": "my-sub",
"eventTime": "2015-03-09T19:14:56Z", "eventTime": "2015-03-09T19:14:56.23Z",
"datastore-push:datastore-contents": { "datastore-push:datastore-contents": {
"foo": { "bar": "some_string" } "foo": { "bar": "some_string" }
} }
} }
} }
3.4. Stream Discovery 3.5. Stream Discovery
For Restconf, this will be accomplished as specified in [Restconf] Relevant for Dynamic Subscriptions, this will be accomplished as
section 6.2. The namespace chosen will be the same as how stream specified in [restconf] section 6.2. The namespace chosen will be
names are acquired for NETCONF, and so that backwards compatibility the same as how stream names are acquired for NETCONF, and so that
can be maintained without replicating this information. For HTTP, backwards compatibility can be maintained without replicating this
this is not specified as there is no client driven signaling/ information.
subscription.
As per [restconf] section 6.3, RESTCONF clients can determine the URL As per [restconf] section 6.3, RESTCONF clients can determine the URL
for the subscription resource (to receive notifications) by sending for the subscription resource (to receive notifications) by sending
an HTTP GET request for the "location" leaf with the stream list an HTTP GET request for the "location" leaf with the stream list
entry. entry.
4. Security Considerations 4. Security Considerations
Subscriptions could be used to intentionally or accidentally overload Subscriptions could be used to intentionally or accidentally overload
resources of a Publisher. For this reason, it is important that the the resources of a Publisher. For this reason, it is important that
Publisher has the ability to prioritize the establishment and push of the Publisher has the ability to prioritize the establishment and
Event Notifications where there might be resource exhaust potential. push of Event Notifications where there might be resource exhaust
In addition, a server needs to be able to suspend existing potential. In addition, a server needs to be able to suspend
Subscriptions when needed. When this occurs, the subscription status existing Subscriptions when needed. When this occurs, the
must be updated accordingly and the Receivers notified. subscription status must be updated accordingly and the Receivers
notified.
A Subscription could be used to attempt retrieve information for A Subscription could be used to attempt retrieve information for
which a Receiver has no authorized access. Therefore it is important which a Receiver has no authorized access. Therefore it is important
that data pushed via a Subscription is authorized equivalently with that data pushed via a Subscription is authorized equivalently with
regular data retrieval operations. Data being pushed to a Receiver regular data retrieval operations. Data being pushed to a Receiver
needs therefore to be filtered accordingly, just like if the data needs therefore to be filtered accordingly, just like if the data
were being retrieved on-demand. The Netconf Authorization Control were being retrieved on-demand. The Netconf Authorization Control
Model [RFC6536] applies even though the transport is not NETCONF. Model [RFC6536] applies even though the transport is not NETCONF.
One or more Publishers could be used to overwhelm a Receiver which One or more Publishers of Configured Subscriptions could be used to
doesn't even support Subscriptions. Therefore Event Notifications overwhelm a Receiver which doesn't even support Subscriptions. There
for Configured Subscriptions MUST only be transmittable over are two protections here. First Event Notifications for Configured
Encrypted transports. Clients which do not want pushed Event Subscriptions MUST only be transmittable over Encrypted transports.
Notifications need only terminate or refuse any transport sessions Clients which do not want pushed Event Notifications need only
from the Publisher. 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 events.
One or more Publishers could overwhelm a Receiver which is unable to One or more Publishers could overwhelm a Receiver which is unable to
control or handle the volume of Event Notifications received. In control or handle the volume of Event Notifications received. In
deployments where this might be a concern, transports supporting per- deployments where this might be a concern, HTTP2 transport such as
subscription Flow Control and Prioritization (such as HTTP/2) should HTTP2) should be selected.
be selected.
Another benefit is that a well-behaved Publisher implementation is
that it is difficult to a Publisher to perform a DoS attack on a
Receiver. DoS attack protection comes from:
o the requirement for trust of a TLS session before publication,
o the need for an HTTP transport augmentation on the Receiver, and
o that the Publication process is suspended when the Receiver
doesn't respond.
5. Acknowledgments 5. Acknowledgments
We wish to acknowledge the helpful contributions, comments, and We wish to acknowledge the helpful contributions, comments, and
suggestions that were received from: Andy Bierman, Sharon Chisholm, suggestions that were received from: Susan Hares, Tim Jenkins, Balazs
Yan Gang, Peipei Guo, Susan Hares, Tim Jenkins, Balazs Lengyel, Lengyel, Kent Watsen, Michael Scharf, and Guangying Zheng.
Hector Trevino, Kent Watsen, and Guangying Zheng.
6. References 6. References
6.1. Normative References 6.1. Normative References
[restconf] [restconf]
Bierman, Andy., Bjorklund, Martin., and Kent. Watsen, Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
"RESTCONF Protocol", March 2016, Protocol", March 2016, <https://datatracker.ietf.org/doc/
<https://datatracker.ietf.org/doc/draft-ietf-netconf- draft-ietf-netconf-restconf/>.
restconf/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport [RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport
Layer Security (TLS) and Datagram Transport Layer Security Layer Security (TLS) and Datagram Transport Layer Security
(DTLS) Heartbeat Extension", RFC 6520, (DTLS) Heartbeat Extension", RFC 6520,
DOI 10.17487/RFC6520, February 2012, DOI 10.17487/RFC6520, February 2012,
skipping to change at page 14, line 38 skipping to change at page 16, line 20
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540, Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015, DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>. <http://www.rfc-editor.org/info/rfc7540>.
[RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements [RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements
for Subscription to YANG Datastores", RFC 7923, for Subscription to YANG Datastores", RFC 7923,
DOI 10.17487/RFC7923, June 2016, DOI 10.17487/RFC7923, June 2016,
<http://www.rfc-editor.org/info/rfc7923>. <http://www.rfc-editor.org/info/rfc7923>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<http://www.rfc-editor.org/info/rfc7951>.
6.2. Informative References 6.2. Informative References
[call-home] [call-home]
Watsen, K., "NETCONF Call Home and RESTCONF Call Home", Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
December 2015, <https://tools.ietf.org/html/draft-ietf- December 2015, <https://tools.ietf.org/html/draft-ietf-
netconf-call-home-17>. netconf-call-home-17>.
[rfc5277bis] [rfc5277bis]
Gonzalez Prieto, Alberto., Clemm, Alexander., Voit, Eric., Gonzalez Prieto, A., Clemm, A., Voit, E., Prasad Tripathy,
Prasad Tripathy, Ambika., and Einar. Nilsen-Nygaard, A., and E. Nilsen-Nygaard, "NETCONF Event Notifications",
"NETCONF Event Notifications", March 2016, September 2016, <https://datatracker.ietf.org/doc/draft-
<https://datatracker.ietf.org/doc/draft-gonzalez-netconf- ietf-netconf-rfc5277bis/>.
5277bis/>.
[W3C-20150203] [W3C-20150203]
"Server-Sent Events, World Wide Web Consortium CR CR- "Server-Sent Events, World Wide Web Consortium CR CR-
eventsource-20121211", February 2015, eventsource-20121211", February 2015,
<https://www.w3.org/TR/2015/REC-eventsource-20150203/>. <https://www.w3.org/TR/2015/REC-eventsource-20150203/>.
[yang-json]
Lhotka, Ladislav., "JSON Encoding of Data Modeled with
YANG", March 2016, <https://datatracker.ietf.org/doc/
draft-ietf-netmod-yang-json/>.
[yang-push] [yang-push]
Clemm, Alexander., Gonzalez Prieto, Alberto., Voit, Eric., Clemm, A., Voit, E., Gonzalez Prieto, A., Prasad Tripathy,
Prasad Tripathy, Ambika., and Einar. Nilsen-Nygaard, A., and E. Nilsen-Nygaard, "Subscribing to YANG datastore
"Subscribing to YANG datastore push updates", February push updates", June 2016,
2016, <https://datatracker.ietf.org/doc/draft-ietf- <https://datatracker.ietf.org/doc/draft-ietf-netconf-yang-
netconf-yang-push/>. push/>.
Appendix A. Proxy YANG Subscription when the Subscriber and Receiver Appendix A. Proxy YANG Subscription when the Subscriber and Receiver
are different are different
The properties of Dynamic and Configured Subscriptions can be The properties of Dynamic and Configured Subscriptions can be
combined to enable deployment models where the Subscriber and combined to enable deployment models where the Subscriber and
Receiver are different. Such separation can be useful with some Receiver are different. Such separation can be useful with some
combination of: combination of:
o An operator doesn't want the subscription to be dependent on the o An operator does not want the subscription to be dependent on the
maintenance of transport level keep-alives. (Transport maintenance of transport level keep-alives. (Transport
independence provides different scalability characteristics.) independence provides different scalability characteristics.)
o There is not a transport session binding, and a transient o There is not a transport session binding, and a transient
Subscription needs to survive in an environment where there is Subscription needs to survive in an environment where there is
unreliable connectivity with the Receiver and/or Subscriber. unreliable connectivity with the Receiver and/or Subscriber.
o An operator wants the Publisher to include highly restrictive o An operator wants the Publisher to include highly restrictive
capacity management and Subscription security mechanisms outside capacity management and Subscription security mechanisms outside
of domain of existing operational or programmatic interfaces. of domain of existing operational or programmatic interfaces.
To build a Proxy Subscription, first the necessary information must To build a Proxy Subscription, first the necessary information must
be signaled as part of the <establish-subscription>. Using this set be signaled as part of the <establish-subscription>. Using this set
of Subscriber provided information; the same process described within of Subscriber provided information; the same process described within
section 3 will be followed. There is one exception. When an HTTP section 3 will be followed. There is one exception. Only when an
status code is 201 is received by the Publisher, it will inform the HTTP status code of 200 comes back from the receiver, will it inform
Subscriber of Subscription establishment success via its Restconf the Subscriber of Subscription establishment success via its Restconf
connection. connection.
After a successful establishment, if the Subscriber wishes to track After a successful establishment, if the Subscriber wishes to track
the state of Receiver subscriptions, it may choose to place a the state of Receiver subscriptions, it may choose to place a
separate on-change Subscription into the "Subscriptions" subtree of separate on-change Subscription into the "Subscriptions" subtree of
the YANG Datastore on the Publisher. the YANG Datastore on the Publisher.
Putting it all together, the message flow is:
+------------+ +-----------+ +----------+
| Subscriber | | Publisher | | Receiver |
+------------+ +-----------+ +----------+
| Restconf PUT: | |
| <establish-subscription>| |
|------------------------>| |
| | |
| |<-----------TLS-------------->|
| | |
| |HTTP POST (Sub ID, data1) |
| |----------------------------->|
| | HTTP 201 (Created)|
| |<-----------------------------|
| Success: HTTP 204| |
|<------------------------| |
| |HTTP POST (SubID, URI, data2) |
| |----------------------------->|
| | HTTP 200 (OK)|
| |<-----------------------------|
| | data3 |
| |<---------------------------->|
| | |
Appendix B. End-to-End Deployment Guidance Appendix B. End-to-End Deployment Guidance
Several technologies are expected to be seen within a deployment to Several technologies are expected to be seen within a deployment to
achieve security and ease-of-use requirements. These are not achieve security and ease-of-use requirements. These are not
necessary for an implementation of this specification, but will be necessary for an implementation of this specification, but will be
useful to consider when considering the operational context. useful to consider when considering the operational context.
B.1. Call Home B.1. Call Home
Pub/Sub implementations should have the ability to transparently Pub/Sub implementations should have the ability to transparently
incorporate lower layer technologies such as Call Home so that secure incorporate [call-home] so that secure TLS connections can originate
TLS connections are always originated from the Publisher. There is a from the desired device.
Restconf Call home function in [call-home]. For security reasons,
this should be implemented when applicable.
B.2. TLS Heartbeat B.2. TLS Heartbeat
Unlike NETCONF, HTTP sessions might not quickly allow a Subscriber to HTTP sessions might not quickly allow a Subscriber to recognize when
recognize when the communication path has been lost from the the communication path has been lost from the Publisher. To
Publisher. To recognize this, it is possible for a Receiver (usually recognize this, it is possible for a Receiver to establish a TLS
the subscriber) to establish a TLS heartbeat [RFC6520]. In the case heartbeat [RFC6520]. In the case where a TLS heartbeat is included,
where a TLS heartbeat is included, it should be sent just from it should be sent just from Receiver to Publisher. Loss of the
Receiver to Publisher. Loss of the heartbeat should result in the heartbeat should result in any Subscription related TCP sessions
Subscription being terminated with the Subscriber (even when the between those endpoints being torn down. The subscription can then
Subscriber and Receiver are different). The Subscriber can then attempt to re-establish.
attempt to re-establish the subscription if desired. If the
Subscription remains active on the Publisher, future receipt of
objects associated with that (or any other unknown) subscription ID
should result in a <delete-subscription> being returned to the
Publisher from the Receiver.
Appendix C. Issues being worked and resolved Appendix C. Issues being worked and resolved
(To be removed by RFC editor prior to publication) (To be removed by RFC editor prior to publication)
C.1. Unresolved Issues C.1. Unresolved Issues
RT2 - In what way to we position "Event notifications" model in this
document vs. current solution in Restconf.
RT3 - Do we include 3rd party signaled subscriptions within models RT3 - Do we include 3rd party signaled subscriptions within models
that need to be supported generically, or for a particular type of that need to be supported generically, or for a particular type of
transport. transport.
RT8 - Once SSE starts, there will be no more Restconf interpretation RT10 - Right now the examples show a YANG timestamp at the hundredths
of further signaling upon the connection. It is unclear how this can of a second level. But the yang-push draft is at seconds. And the
be made to work with modify and delete subscription. If it cannot, a requirements show at least milliseconds (if not more).
method of sending events without SSE will be needed, although this
would diverge from the existing Restconf mechanisms
C.2. Agreement in principal C.2. Agreement in principal
RT4 - Need to add into document examples of 5277bis Event streams.
Document only includes yang-push examples at this point.
RT6 - We need to define encodings of rfc5277bis notifications.
C.3. Resolved Issues
RT1 - Integration specifics for Restconf capability discovery on RT1 - Integration specifics for Restconf capability discovery on
different types of Streams different types of Streams
RT4 - Need to add into document examples of 5277bis Event streams. RT2 - In what way to we position Event notifications model in this
Document only includes yang-push examples at this point. document vs. current solution in Restconf.
RT6 - We need to define encodings of rfc5277bis notifications for RT5 - Doesn't make sense to use Restconf for Configured
both Restconf and HTTP. subscriptions. HTTP will be used.
RT7 - HTTP native option doesn't currently use SSE. But we should RT7 - HTTP native option doesn't currently use SSE. But we should
evaluate moving to that as possible. It will make development evaluate moving to that as possible. It will make development
integration easier and more consistent. integration easier and more consistent.
RT8 - Once SSE starts, there will be no more Restconf interpretation
of further signaling upon the connection. It is unclear how this can
be made to work with modify and delete subscription. If it cannot, a
method of sending events without SSE will be needed, although this
would diverge from the existing Restconf mechanisms
RT9 - For static subscriptions, perhaps we can use Restconf call home RT9 - For static subscriptions, perhaps we can use Restconf call home
to originate an SSE connection. This assume RT8 & RT2 can be to originate an SSE connection. This assume RT8 & RT2 can be
resolved with SSE. resolved with SSE.
C.3. Resolved Issues Appendix D. Changes between revisions
RT5 - Doesn't make sense to use Restconf for Configured (To be removed by RFC editor prior to publication)
subscriptions. HTTP will be used.
v00 - v01
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 Authors' Addresses
Eric Voit Eric Voit
Cisco Systems Cisco Systems
Email: evoit@cisco.com Email: evoit@cisco.com
Alexander Clemm Alexander Clemm
Cisco Systems Cisco Systems
Email: alex@cisco.com Email: alex@clemm.org
Alberto Gonzalez Prieto
Cisco Systems
Email: albertgo@cisco.com
Ambika Prasad Tripathy Ambika Prasad Tripathy
Cisco Systems Cisco Systems
Email: ambtripa@cisco.com Email: ambtripa@cisco.com
Einar Nilsen-Nygaard Einar Nilsen-Nygaard
Cisco Systems Cisco Systems
Email: einarnn@cisco.com Email: einarnn@cisco.com
Alberto Gonzalez Prieto Andy Bierman
Cisco Systems YumaWorks
Email: albertgo@cisco.com Email: andy@yumaworks.com
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