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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 5277

Network Working Group                                        S. Chisholm
Internet-Draft                                                    Nortel
Intended status: Standards Track                              H. Trevino
Expires: November 16, 2007                                         Cisco
                                                            May 15, 2007


                      NETCONF Event Notifications
                 draft-ietf-netconf-notification-07.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

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   This Internet-Draft will expire on November 16, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).













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Abstract

   This document defines mechanisms which provide an asynchronous
   message notification delivery service for the NETCONF protocol.  This
   is an optional capability built on top of the base NETCONF
   definition.  This document defines the capabilities and operations
   necessary to support this service.












































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Definition of Terms  . . . . . . . . . . . . . . . . . . .  4
     1.2.  Motivation . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.3.  Event Notifications in NETCONF . . . . . . . . . . . . . .  5
     1.4.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  6
   2.  Notification-Related Operations  . . . . . . . . . . . . . . .  7
     2.1.  Subscribing to receive Event Notifications . . . . . . . .  7
       2.1.1.  <create-subscription>  . . . . . . . . . . . . . . . .  7
     2.2.  Sending Event Notifications  . . . . . . . . . . . . . . .  9
       2.2.1.  <notification> . . . . . . . . . . . . . . . . . . . .  9
     2.3.  Terminating the Subscription . . . . . . . . . . . . . . . 10
   3.  Supporting Concepts  . . . . . . . . . . . . . . . . . . . . . 11
     3.1.  Capabilities Exchange  . . . . . . . . . . . . . . . . . . 11
       3.1.1.  Capability Identifier  . . . . . . . . . . . . . . . . 11
       3.1.2.  Capability Example . . . . . . . . . . . . . . . . . . 11
     3.2.  Event Streams  . . . . . . . . . . . . . . . . . . . . . . 11
       3.2.1.  Event Stream Definition  . . . . . . . . . . . . . . . 12
       3.2.2.  Event Stream Content Format  . . . . . . . . . . . . . 13
       3.2.3.  Default Event Stream . . . . . . . . . . . . . . . . . 13
       3.2.4.  Event Stream Sources . . . . . . . . . . . . . . . . . 13
       3.2.5.  Event Stream Discovery . . . . . . . . . . . . . . . . 13
     3.3.  Notification Replay  . . . . . . . . . . . . . . . . . . . 15
       3.3.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . 15
       3.3.2.  Creating a Subscription with Replay  . . . . . . . . . 16
       3.3.3.  Replay Complete Notification . . . . . . . . . . . . . 16
     3.4.  Notification Management Schema . . . . . . . . . . . . . . 16
     3.5.  Subscriptions Data . . . . . . . . . . . . . . . . . . . . 20
     3.6.  Filter Mechanics . . . . . . . . . . . . . . . . . . . . . 20
       3.6.1.  Named Profiles . . . . . . . . . . . . . . . . . . . . 21
       3.6.2.  Filtering  . . . . . . . . . . . . . . . . . . . . . . 21
     3.7.  Message Flow . . . . . . . . . . . . . . . . . . . . . . . 21
   4.  XML Schema for Event Notifications . . . . . . . . . . . . . . 23
   5.  Filtering Examples . . . . . . . . . . . . . . . . . . . . . . 27
     5.1.  Subtree Filtering  . . . . . . . . . . . . . . . . . . . . 27
     5.2.  XPATH filters  . . . . . . . . . . . . . . . . . . . . . . 30
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 32
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 33
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 34
   9.  Normative References . . . . . . . . . . . . . . . . . . . . . 35
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36
   Intellectual Property and Copyright Statements . . . . . . . . . . 37








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1.  Introduction

   [NETCONF] can be conceptually partitioned into four layers:

   Layer                      Example
    +-------------+      +----------------------------------------+
    |   Content   |      |     Configuration data                 |
    +-------------+      +----------------------------------------+
              |                           |
    +-------------+      +-------------------------------------------+
    | Operations  |      | <get-config>, <edit-config> <notification>|
    +-------------+      +-------------------------------------------+
              |                           |                    |
    +-------------+      +-----------------------------+       |
    |     RPC     |      |    <rpc>, <rpc-reply>       |       |
    +-------------+      +-----------------------------+       |
             |                           |                     |
    +-------------+      +------------------------------------------+
    | Transport   |      |   BEEP, SSH, SSL, console                |
    |   Protocol  |      |                                          |
    +-------------+      +------------------------------------------+


                                 Figure 1

   This document defines mechanisms which provide an asynchronous
   message notification delivery service for the [NETCONF] protocol.
   This is an optional capability built on top of the base NETCONF
   definition.  This memo defines the capabilities and operations
   necessary to support this service.

1.1.  Definition of Terms

   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 [RFC2119].

   Element:  An [XML] Element.

   Subscription:  A concept related to the delivery of notifications (if
      any to send) involving destination and selection of notifications.
      It is bound to the lifetime of a session.

   Operation:  This term is used to refer to NETCONF protocol
      operations.  Specifically within this document, operation refers
      to NETCONF protocol operations defined in support of NETCONF
      notifications.




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   Event:  An event is something that happens which may be of interest -
      a configuration change, a fault, a change in status, crossing a
      threshold, or an external input to the system, for example.  Often
      this results in an asynchronous message, sometimes referred to as
      a notification or event notification, being sent to interested
      parties to notify them that this event has occurred.

   Replay:  The ability to send/re-send previously logged notifications
      upon request.  These notifications are sent asynchronously.  This
      feature is implemented by the NETCONF server and invoked by the
      NETCONF client.

   Stream:  An event stream is a set of event notifications matching
      some forwarding criteria and it is available to NETCONF clients
      for subscription.

   Named Profile:  A predefined set of filtering criteria residing in
      the Network Element which may be applied to a notification session
      at subscription creation time.

1.2.  Motivation

   The motivation for this work is to enable the sending of asynchronous
   messages that are consistent with the data model (content) and
   security model used within a NETCONF implementation.

1.3.  Event Notifications in NETCONF

   This memo defines a mechanism whereby the NETCONF client indicates
   interest in receiving event notifications from a NETCONF server by
   creating a subscription to receive event notifications.  The NETCONF
   server replies to indicate whether the subscription request was
   successful and, if it was successful, begins sending the event
   notifications to the NETCONF client as the events occur within the
   system.  These event notifications will continue to be sent until
   either the NETCONF session is terminated or the subscription
   terminates for some other reason.  The event notification
   subscription allows a number of options to enable the NETCONF client
   to specify which events are of interest.  These are specified when
   the subscription is created.

   A NETCONF server is not required to process RPC requests on the
   session associated with the subscription until the notification
   subscription is done and may silently discard these requests.  A
   capability may be advertised to announce that a server is able to
   process RPCs while a notification stream is active on a session.  The
   behaviour of such a capability is outside the scope of this document.




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1.4.  Requirements

   The following requirements have been addressed by the solution:

   o  Initial release should ensure it supports notification in support
      of configuration operations

   o  Data content must not preclude the use of the same data model as
      used in configuration

   o  solution should support a reasonable message size limit (syslog
      and SNMP are rather constrained in terms of message sizes)

   o  solution should provide reliable delivery of notifications

   o  solution should provide a subscription mechanism (A NETCONF server
      does not send notifications before being asked to do so and the
      NETCONF client initiates the flow of notifications)

   o  solution should provide a filtering mechanism within the NETCONF
      server

   o  solution should send sufficient information in a notification so
      that it can be analyzed independent of the transport mechanism
      (data content fully describes a notification; protocol information
      is not needed to understand a notification)

   o  solution should support replay of locally logged notifications























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2.  Notification-Related Operations

2.1.  Subscribing to receive Event Notifications

   The event notification subscription is initiated by the NETCONF
   client and responded to by the NETCONF server.  When the event
   notification subscription is created, the events of interest are
   specified.

   Content for an event notification subscription can be selected by
   applying user-specified filters.

2.1.1.  <create-subscription>

   Description:

      This operation initiates an event notification subscription which
      will send asynchronous event notifications to the initiator of the
      command until the subscription terminates.

   Parameters:

      Stream:

         An optional parameter that indicates which stream of events is
         of interest.  If not present, then events in the default
         NETCONF stream will be sent.

      Filter:

         An optional parameter that indicates which subset of all
         possible events are of interest.  The format of this parameter
         is the same as that of the filter parameter in the NETCONF
         protocol operations.  If not present, all events not precluded
         by other parameters will be sent.  This is mutually exclusive
         with the named profile parameter.  See section 3.6 for more
         information on filters.

      Named Profile:

         An optional parameter that refers to a separately defined
         filter profile.  If not present, no additional filtering will
         be applied.  Note that changes to the profile after the
         subscription has been created will have no effect.  This is
         mutually exclusive with the filter parameter.  For more
         information on named profiles, see section 3.6.1.





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      Start Time:

         A parameter used to trigger the replay feature and indicates
         that the replay should start at the time specified.  If
         startTime is not present, this is not a replay subscription.
         It is valid to specify start times that are later than the
         current time.  If the startTime specified is earlier then the
         log can support, the replay will begin with the earliest
         available notification.  This parameter is of type dateTime.

      Stop Time:

         An optional parameter used with the optional replay feature to
         indicate the newest notifications of interest.  If stop time is
         not present, the notifications will continue until the
         subscription is terminated.  Must be used with 'startTime'.  It
         is valid to specify stop times that are later than the current
         time.  This parameter is of type dateTime.

   Positive Response:

      If the NETCONF server can satisfy the request, the server sends an
      <ok> element.

   Negative Response:

      An <rpc-error> element is included within the <rpc-reply> if the
      request cannot be completed for any reason.  Subscription requests
      will fail if a filter with invalid syntax is provided or if the
      name of a non-existent profile or stream is provided.

      If a stopTime is specified in a request without having specified a
      startTime the following error is returned:

         Tag: missing-element

         Error-type: protocol

         Severity: error

         Error-info: <startTime Description: An expected element is
         missing.

      If the optional replay feature is requested but it is not
      supported by the NETCONF server, the following error is returned:






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         Tag: operation-failed

         Error-type: protocol

         Severity: error

         Error-info: none

         Description: Request could not be completed because the
         requested operation failed for some reason not covered by any
         other error condition

2.1.1.1.  Usage Example

              <netconf:rpc message-id="101"
                xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
                <create-subscription>
                </create-subscription>
              </netconf:rpc>


2.2.  Sending Event Notifications

   Once the subscription has been set up, the NETCONF server sends the
   event notifications asynchronously over the connection.

2.2.1.  <notification>

   Description:

      An event notification is sent to the client who initiated a
      <create-subscription> command asynchronously when an event of
      interest (i.e., meeting the specified filtering criteria) to them
      has occurred.  An event notification is a complete and well-formed
      XML document.  Note that <notification> is not an RPC method but
      rather the top level element identifying the one way message as a
      notification.

   Parameters:

      Data:

         Contains notification-specific tagged content.  The content of
         the data tag is beyond the scope of this document.

   Response:





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      No response.  Not applicable.

2.3.  Terminating the Subscription

   Closing of the event notification subscription can be done by
   terminating the NETCONF session ( <kill-session> ) or the underlying
   transport session.  If a stop time is provided when the subscription
   is created, then the subscription will terminate after the stop time
   is reached.  In this case, the NETCONF session will still be an
   active session.









































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3.  Supporting Concepts

3.1.  Capabilities Exchange

   The ability to process and send event notifications is advertised
   during the capability exchange between the NETCONF client and server.

3.1.1.  Capability Identifier

   "urn:ietf:params:netconf:capability:notification:1.0"

3.1.2.  Capability Example


   <hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <capabilities>
        <capability>
            urn:ietf:params:xml:ns:netconf:base:1.0
          </capability>
          <capability>
            urn:ietf:params:netconf:capability:startup:1.0
          </capability>
          <capability>
            urn:ietf:params:netconf:capability:notification:1.0
          </capability>
       </capabilities>
     <session-id>4</session-id>
   </hello>


3.2.  Event Streams

   An event stream is defined as a set of event notifications matching
   some forwarding criteria.

   The diagram depicted in Figure 2 illustrates the notification flow
   and concepts identified in this document.  The following is observed
   from the diagram below: System components (c1..cn) generate event
   notifications which are passed to a central component for
   classification and distribution.  The central component inspects each
   event notification and matches the event notification against the set
   of stream definitions.  When a match occurs, the event notification
   is considered to be a member of that event stream (stream 1..stream
   n).  An event notification may be part of multiple event streams.

   When a NETCONF client subscribes to a given event stream, user-
   defined filters, if applicable, are applied to the event stream and
   matching event notifications are forwarded to the NETCONF server for



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   distribution to subscribed NETCONF clients.  For more information on
   filters, see section 3.6.

   A notification logging service may also be available, in which case,
   the central component logs notifications.  The NETCONF server may
   later retrieve logged notifications via the optional replay feature.
   For more information on replay, see section 3.3.



   +----+
   | c1 |---+             available streams
   +----+   |    +---------+
   +----+   |    |central  |-> stream 1
   | c2 |   +--->|event    |-> stream 2     filter  +-------+
   +----+   |    |processor|-> NETCONF stream ----->|netconf|
    ...     |    |         |-> stream n             |server |
   System   |    +---------+                        +-------+
   Components|       |                                 /\
    ...     |        |                                 ||
   +----+   |        |       (------------)            ||
   | cn |---+        |       (notification)            ||
   +----+            +-----> (  logging   )            ||
                             (  service   )            ||
                             (------------)            ||
                                                       ||
                                                       ||
                                                       \/
                                                    +-------+
                                                    |netconf|
                                                    |client |
                                                    +-------+


                                 Figure 4

3.2.1.  Event Stream Definition

   Event streams are predefined on the managed device.  The
   configuration of event streams is outside the scope of this document.
   However, it is envisioned that event streams are either pre-
   established by the vendor (pre-configured) or user configurable
   (e.g., part of the device's configuration) or both.  Device vendors
   may allow event stream configuration via NETCONF protocol (i.e.,
   edit-config operation).






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3.2.2.  Event Stream Content Format

   The contents of all event streams made available to a NETCONF client
   (i.e., the notification sent by the NETCONF server) must be encoded
   in XML.

3.2.3.  Default Event Stream

   A NETCONF server implementation supporting the notification
   capability must support the "NETCONF" notification event stream.
   This stream contains all NETCONF XML event notifications supported by
   the NETCONF server.  The definition of the event notifications and
   their contents for this event stream is outside the scope of this
   document.

3.2.4.  Event Stream Sources

   With the exception of the default event stream (NETCONF
   notifications) specification of additional event stream sources
   (e.g., SNMP, syslog, etc.) is outside the scope of this document.
   NETCONF server implementations may leverage any desired event stream
   source in the creation of supported event streams.

3.2.5.  Event Stream Discovery

   A NETCONF client retrieves the list of supported event streams from a
   NETCONF server using the <get> RPC request.

3.2.5.1.  Name Retrieval using <get> operation

   The list of available event streams is retrieved by requesting the
   <eventStreams> subtree via a <get> operation.  Available event
   streams for the requesting session are returned in the reply
   containing the <name> and <description> elements, where <name>
   element is mandatory and its value is unique.  The returned list must
   only include the names of those event streams for which the NETCONF
   session has sufficient privileges.  The NETCONF session privileges
   are determined via access control mechanisms which are beyond the
   scope of this document.  An empty reply is returned if there are no
   available event streams.  The information is retrieved by requesting
   the <eventStreams> subtree via a <get> operation.










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   Example: Retrieving available event stream list using <get>
   operation:


 <rpc message-id="101"
    xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">

   <get>
    <filter type="subtree">
      <eventStreams xmlns="urn:ietf:params:xml:ns:netmod:notification"/>
    </filter>
   </get>
 </rpc>


   The NETCONF server returns a list of event streams available for
   subscription: NETCONF, snmp, and syslog-critical in this example.


  <rpc-reply message-id="101"
                   xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
    <data>
       <eventStreams xmlns="urn:ietf:params:xml:ns:netmod:notification">
            <stream>
               <name>NETCONF</name>
               <description>Default netconf event stream
               </description>
               <replaySupport>true</replaySupport>
            </stream>
            <stream>
              <name>snmp</name>
                <description>SNMP notifications</description>
                <replaySupport>false</replaySupport>
            </stream>
            <stream>
              <name>syslog-critical</name>
              <description>Critical and higher severity
              </description>
              <replaySupport>true</replaySupport>
            </stream>
          </eventStreams>
    </data>
  </rpc-reply>








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3.2.5.2.  Event Stream Subscription

   A NETCONF client may request from the NETCONF server the list of
   available event streams to this session and then issue a <create-
   subscription> request with the desired event stream name.  Omitting
   the event stream name from the <create-subscription> request results
   in subscription to the default NETCONF event stream.

3.2.5.2.1.  Filtering Event Stream Contents

   The set of event notifications delivered in an event stream may be
   further refined by applying a user-specified filter at subscription
   creation time ( <create-subscription> ).  This is a transient filter
   associated with the event notification subscription and does not
   modify the event stream configuration.

   XPATH support for the Notification capability is advertised as part
   of the normal XPATH capability advertisement.  If XPATH support is
   advertised via the XPATH capability then XPATH is supported for
   notification filtering and if this capability is not advertised, then
   XPATH is not supported for notification filtering.

3.3.   Notification Replay

3.3.1.  Overview

   Replay is the ability to create an event subscription that will
   resend recently generated notifications.  These notifications are
   sent the same way as normal notifications.

   A replay of notifications is specified by including an optional
   parameter to the subscription command that indicates the start time
   of the replay.  The end time is specified using the optional stopTime
   parameter.  If not present, notifications will continue to be sent
   until the subscription is terminated.

   A notification stream that supports replay is not expected to have an
   unlimited supply of saved notifications available to accommodate any
   replay request.

   The actual number of stored notifications available for retrieval at
   any given time is a NETCONF server implementation specific matter.
   Control parameters for this aspect of the feature are outside the
   scope of the current document.

   Replay is dependent on a notification stream supporting some form of
   notification logging, although it puts no restrictions on the size or
   form of the log, nor where it resides within the device.



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3.3.2.  Creating a Subscription with Replay

   This feature uses optional parameters to the <create-subscription>
   command called 'startTime' and 'stopTime'. 'startTime' identifies the
   earliest date and time of interest for event notifications being
   replayed and also indicates that a subscription will be providing
   replay of notifications.  Events generated before this time are not
   matched. 'stopTime' specifies the latest date and time of interest
   for event notifications being replayed.  If it is not present, then
   notifications will continue to be sent until the subscription is
   terminated.

   Note that startTime and stopTime are associated with the time an
   event was generated by the system.

   A replay complete notification is sent to indicate that all of the
   replay notifications have been sent.  If this subscription has a stop
   time, then this session becomes a normal NETCONF session again.  In
   the case of a subscription without a stop time, after the replay
   complete notification has been sent, it can be expected that any
   notifications generated since the start of the subscription creation
   will be sent followed by notifications as they arise naturally within
   the system.

3.3.3.  Replay Complete Notification

   The replay complete notification is the last notification sent over a
   replay subscription.  It indicates that replay is complete.  This
   notification will only be sent if a 'stopTime' was specified when the
   replay subscription was created.  After this notification is received
   the subscription is terminated and the session becomes a normal
   NETCONF session.

   The replayComplete can not be filtered out.  It will always be sent
   on a relay subscription that specified a stop time.

3.4.  Notification Management Schema

   This Schema is used to learn about the event streams supported on the
   system and the query and modify named profiles.  It also contains the
   definition of the replayComplete, which is sent to indicate that an
   event replay has sent all applicable notifications."


 <?xml version="1.0" encoding="UTF-8"?>
 <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
     xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0"
     xmlns:ncEvent="urn:ietf:params:netconf:capability:notification:1.0"



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     xmlns:manageEvent="urn:ietf:params:xml:ns:netmod:notification"
     targetNamespace="urn:ietf:params:xml:ns:netmod:notification"
     elementFormDefault="qualified"
     attributeFormDefault="unqualified">
     <xs:annotation>
         <xs:documentation xml:lang="en">
             A schema that can be used to learn about current
             event streams and to manage named profiles. It also
             contains the replayComplete notification.
         </xs:documentation>
     </xs:annotation>


 <xs:import namespace="http://www.w3.org/XML/1998/namespace"
         schemaLocation="http://www.w3.org/2001/xml.xsd"/>
 <xs:import namespace="urn:ietf:params:xml:ns:netconf:base:1.0"
         schemaLocation="urn:ietf:params:xml:ns:netconf:base:1.0"/>
 <xs:import namespace=
       "urn:ietf:params:netconf:capability:notification:1.0"
         schemaLocation=
            "urn:ietf:params:netconf:capability:notification:1.0"/>

 <xs:element name="netconf" type="manageEvent:Netconf"/>

 <xs:complexType name="Netconf">
   <xs:sequence>
       <xs:element name="eventStreams" >
         <xs:annotation>
            <xs:documentation>
              The list of event streams supported by the
              system. When a query is issued, the returned
              set of streams is determined based on user
              privileges.
            </xs:documentation>
          </xs:annotation>
          <xs:complexType>
            <xs:sequence minOccurs="0" maxOccurs="unbounded">
              <xs:element name="stream">
                 <xs:annotation>
                   <xs:documentation>
                     Stream name and description.
                   </xs:documentation>
                 </xs:annotation>
                 <xs:complexType>
                   <xs:sequence>
                     <xs:element name="name" type="xs:string"/>
                     <xs:element name="description"
                                         type="xs:string"/>



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                     <xs:element name="replaySupport"
                                         type="xs:boolean"/>
                     <xs:element name="replayLogStartTime"
                                         type="xs:dateTime">
                       <xs:annotation>
                         <xs:documentation>
                            The start time of the log used to
                            support the replay function. If
                            replay is not supported, this will
                            return the current time.
                          </xs:documentation>
                        </xs:annotation>
                      </xs:element>
                    </xs:sequence>
                  </xs:complexType>
                </xs:element>
              </xs:sequence>
            </xs:complexType>
          </xs:element>


          <xs:element name="namedProfiles" minOccurs="0">
            <xs:complexType>
              <xs:sequence>
                <xs:element name="namedProfile"
                        type="manageEvent:NamedProfile" minOccurs="0"
                             maxOccurs="unbounded" />
              </xs:sequence>
            </xs:complexType>
          </xs:element>

         <xs:element name="replayComplete"
                     type="manageEvent:ReplayCompleteNotificationType"
                     minOccurs="0">
           <xs:annotation>
             <xs:documentation>
               This notification is sent to signal the end of a replay
               portion of a subscription.
             </xs:documentation>
           </xs:annotation>
         </xs:element>
       </xs:sequence>
     </xs:complexType>

     <xs:complexType name="ReplayCompleteNotificationType" >
         <xs:complexContent>
             <xs:extension base="ncEvent:NotificationType">
                 <xs:sequence>



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                     <xs:element name="eventClass"/>
                 </xs:sequence>
             </xs:extension>
         </xs:complexContent>
     </xs:complexType>



     <xs:complexType name="NamedProfile">
         <xs:annotation>
             <xs:documentation>
                 A named profile, which is a saved set of parameters
                 that may be associated with zero or more
                 active subscriptions.

                 This object can be created, read, deleted and its
                 individual components can be modified.
             </xs:documentation>
         </xs:annotation>
         <xs:sequence>

             <xs:element name="name">
                 <xs:annotation>
                     <xs:documentation>
                         The name associated with the profile.
                         This object is readable and modifiable.
                     </xs:documentation>
                 </xs:annotation>
             </xs:element>

             <xs:element name="stream"  minOccurs="0">
                 <xs:annotation>
                     <xs:documentation xml:lang="en">
                         The event stream associated with this named
                         profile.

                         This object is readable and modifiable.
                     </xs:documentation>
                 </xs:annotation>
             </xs:element>

             <xs:element name="filter"
                 type="netconf:filterInlineType"  minOccurs="0">
                 <xs:annotation>
                     <xs:documentation xml:lang="en">
                         The filters associated with this named
                         profile.




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                         This object is readable and modifiable.
                     </xs:documentation>
                 </xs:annotation>
             </xs:element>

             <xs:element name="lastModified" type="xs:dateTime">
                 <xs:annotation>
                     <xs:documentation>
                         The timestamp of the last modification to this
                         named Profile. Note that modification of the
                         profile does not cause an immediate update
                         to all applicable subscription. Therefore,
                         this time should be compared with the last
                         modified time associated with the
                         subscription. If this time is earlier, then
                         the subscription is using the exact set of
                         parameters associated with this named profile.
                         If this time is later, then the subscription
                         is using an earlier version of this named
                         profile and the exact parameters may not
                         match. Note there is no guarantee that the
                         profile named in the subscription will be
                         found at all."

                         This object is read-only.
                     </xs:documentation>
                 </xs:annotation>
             </xs:element>
         </xs:sequence>
     </xs:complexType>
 </xs:schema>


3.5.  Subscriptions Data

   While it may be possible to retrieve information about subscriptions
   via a get operation, subscriptions are not stored configuration.
   They are non-persistent state information and their lifetime is
   defined by their session.

   Named profiles, if used, are considered configuration data.

3.6.  Filter Mechanics

   Note that when multiple filter elements are specified, they are
   applied collectively, so event notifications need to pass all
   specified filters in order to be sent to the subscriber.  If a filter
   element is specified to look for data of a particular value, and the



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   data item is not present within a particular event notification for
   its value to be checked against, it will be filtered out.  For
   example, if one were to check for 'severity=critical' in a
   configuration event notification where this field was not supported,
   then the notification would be filtered out.

   Note that the order that filter elements are applied does not matter
   since the resulting set of notifications is the intersection of the
   set of notifications that pass each filtering criteria.

3.6.1.  Named Profiles

   A named profile is a filter that is created ahead of time and applied
   at the time an event notification subscription is created.  Note that
   changes to the profile after the subscription has been created will
   have no effect on the subscription.  Since named profiles exist
   outside of the subscription, they persist after the subscription has
   been torn down.

3.6.2.  Filtering

   Inline filtering is explicitly stated when the event notification
   subscription is created.  This is specified via the 'filter'
   parameter.  Filters only exist as parameters to the subscription.

3.7.  Message Flow

























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   The following figure depicts message flow between a NETCONF client
   (C) and NETCONF server (S) in order create a subscription and begin
   the flow of notifications.  It is possible that many rpc/rpc-reply
   sequences occur before the subscription is created or after a
   stopTime in a replay subscription, but this is not depicted in the
   figure.


                             C                           S
                             |                           |
                             |  capability exchange      |
                             |-------------------------->|
                             |<------------------------->|
                             |                           |
                             |  <create-subscription>    |
                             |-------------------------->|
                             |<--------------------------|
                             |     <rpc-reply>           |
                             |                           |
                             |     <notification>        |
                             |<--------------------------|
                             |                           |
                             |     <notification>        |
                             |<--------------------------|
                             |                           |
                             |                           |
                             |                           |
                             |     <notification>        |
                             |<--------------------------|
                             |                           |
                             |                           |


                                 Figure 8

















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4.  XML Schema for Event Notifications

   The following [XML Schema] defines NETCONF Event Notifications.


<?xml version="1.0" encoding="UTF-8"?>
  <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
        xmlns="urn:ietf:params:netconf:capability:notification:1.0"
        xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0"
        targetNamespace=
          "urn:ietf:params:netconf:capability:notification:1.0"
        elementFormDefault="qualified"
        attributeFormDefault="unqualified"
            xml:lang="en">

    <!-- import standard XML definitions -->

     <xs:import namespace="http://www.w3.org/XML/1998/namespace"
                schemaLocation="http://www.w3.org/2001/xml.xsd">
       <xs:annotation>
         <xs:documentation>
           This import accesses the xml: attribute groups for the
           xml:lang as declared on the error-message element.
         </xs:documentation>
       </xs:annotation>
     </xs:import>

     <!-- import base netconf definitions -->
     <xs:import namespace="urn:ietf:params:xml:ns:netconf:base:1.0"
       schemaLocation="urn:ietf:params:xml:ns:netconf:base:1.0" />



<!-- ************** Symmetrical Operations  ********************-->

     <!-- <create-subscription> operation -->


    <xs:complexType name="createSubscriptionType">
        <xs:complexContent>
            <xs:extension base="netconf:rpcOperationType">
                <xs:sequence>
                    <xs:element name="stream"
                        type="streamNameType" minOccurs="0">
                        <xs:annotation>
                            <xs:documentation>
                               An optional parameter that indicates
                               which stream of events is of interest. If



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                               not present, then events in the default
                               NETCONF stream will be sent.
                            </xs:documentation>
                        </xs:annotation>
                    </xs:element>
                    <xs:choice>
                        <xs:element name="filter"
                            type="netconf:filterInlineType"
                            minOccurs="0">
                            <xs:annotation>
                                <xs:documentation>
                                    An optional parameter that indicates
                                    which subset of all possible events
                                    are of interest. The format of this
                                    parameter is the same as that of the
                                    filter parameter in the NETCONF
                                    protocol operations. If not present,
                                    all events not precluded by other
                                    parameters will be sent. This is
                                    mutually exclusive with the named
                                    profile parameter.
                                </xs:documentation>
                            </xs:annotation>
                        </xs:element>
                        <xs:element name="named-profile"
                            type="namedProfileType" minOccurs="0">
                            <xs:annotation>
                                <xs:documentation>
                                    An optional parameter that points to
                                    a separately defined filter profile.
                                    If not present, no additional
                                    filtering will be applied. Note that
                                    changes to the profile after the
                                    subscription has been created will
                                    have no effect. This is mutually
                                    exclusive with the filter parameter.
                                </xs:documentation>
                            </xs:annotation>
                        </xs:element>
                    </xs:choice>
                    <xs:element name="startTime" type="xs:dateTime"
                        minOccurs="0" >
                        <xs:annotation>
                            <xs:documentation>
                                A parameter used to trigger the replay
                                feature and indicates that the replay
                                should start at the time specified. If
                                start time is not present, this is not a



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                                replay subscription.
                            </xs:documentation>
                        </xs:annotation>
                    </xs:element>
                    <xs:element name="stopTime" type="xs:dateTime"
                        minOccurs="0" >
                        <xs:annotation>
                            <xs:documentation>
                                An optional parameter used with the
                                optional replay feature to indicate the
                                newest notifications of interest. If
                                stop time is not present, the
                                notifications will continue until the
                                subscription is terminated. Must be used
                                with 'startTime'.
                            </xs:documentation>
                        </xs:annotation>
                    </xs:element>
                </xs:sequence>
            </xs:extension>
        </xs:complexContent>
    </xs:complexType>

    <xs:simpleType name="namedProfileType">
        <xs:annotation>
            <xs:documentation>
                The name of a saved profile containing filtering
                elements.
            </xs:documentation>
        </xs:annotation>
        <xs:restriction base="xs:string"/>
    </xs:simpleType>

    <xs:simpleType name="streamNameType">
        <xs:annotation>
            <xs:documentation>
                The name of an event stream.
            </xs:documentation>
        </xs:annotation>
        <xs:restriction base="xs:string"/>
    </xs:simpleType>


    <xs:element name="create-subscription"
        type="createSubscriptionType"
        substitutionGroup="netconf:rpcOperation">
        <xs:annotation>
            <xs:documentation>



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                The command to create a notification subscription. It
                takes as argument the name of the notification stream
                and  filter or profile information. All of those options
                limit the content of the subscription. In addition,
                there are two time-related parameters startTime and
                stopTime which can be used to select the time interval
                of interest.
            </xs:documentation>
        </xs:annotation>
    </xs:element>

<!-- ************** One-way Operations  ******************-->

     <!-- <Notification> operation -->
     <xs:complexType name="NotificationType">
        <xs:sequence>
          <xs:element name="data" type="netconf:dataInlineType" />
        </xs:sequence>
     </xs:complexType>

     <xs:element name="notification" type="NotificationType"/>

  </xs:schema>




























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5.  Filtering Examples

   The following section provides examples to illustrate the various
   methods of filtering content on an event notification subscription.

5.1.  Subtree Filtering

   XML subtree filtering is not well suited for creating elaborate
   filter definitions given that it only supports equality comparisons
   and logical OR operations (e.g., in an event subtree give me all
   event notifications which have severity=critical or severity=major or
   severity=minor).  Nevertheless, it may be used for defining simple
   event notification forwarding filters as shown below.

   In order to illustrate the use of filter expressions it is necessary
   to assume some of the event notification content.  The examples
   herein assume that the event notification schema definition has an
   <events> element at the top level that contains one or more child
   elements <eventEntry> consisting of the event class (e.g., fault,
   state, config, etc.) reporting entity and either severity or
   operational state.






























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   Sample event list


               <events>
                 <eventEntry>
                   <eventClass>fault</eventClass>
                   <reportingEntity>
                     <card>Ethernet0</card>
                   </reportingEntity>
                   <severity>major</severity>
                 </eventEntry>
                 <eventEntry>
                   <eventClass>fault</eventClass>
                   <reportingEntity>
                     <card>Ethernet2</card>
                   </reportingEntity>
                   <severity>critical</severity>
                 </eventEntry>
                 <eventEntry>
                   <eventClass>fault</eventClass>
                   <reportingEntity>
                     <card>ATM1</card>
                   </reportingEntity>
                   <severity>minor</severity>
                 </eventEntry>
                 <eventEntry>
                   <eventClass>state</eventClass>
                   <reportingEntity>
                     <card>Ethernet0</card>
                   </reportingEntity>
                   <operState>enabled</operState>
                 </eventEntry>
               </events>


   The following example illustrates selecting events which have
   severities of critical, major, or minor (presumably fault events).
   The filtering criteria evaluation is as follows:

   ((severity=critical) | (severity=major) | (severity=minor))











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 <netconf:rpc message-id="101"
              xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
       <create-subscription
                xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
         <filter netconf:type="subtree">
            <event xmlns="http://example.com/event/1.0">
              <events>
               <eventEntry>
                 <eventClass>fault</eventClass>
                    <severity>critical</severity>
               </eventEntry>
               <eventEntry>
                   <eventClass>fault</eventClass>
                   <severity>major</severity>
                </eventEntry>
                <eventEntry>
                   <eventClass>fault</eventClass>
                   <severity>minor</severity>
                </eventEntry>
               </events>
            </event>
        </filter>
      </create-subscription>
    </netconf:rpc>




   The following example illustrates selecting state or config
   EventClasses or fault events that are related to card Ethernet0.  The
   filtering criteria evaluation is as follows:

   ( state | config | fault & card=Ethernet0)


















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 <netconf:rpc message-id="101"
           xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
    <create-subscription>
       <filter netconf:type="subtree">
            xmlns="urn:ietf:params:netconf:capability:notification:1.0">
            <event xmlns="http://example.com/event/1.0">
                 <events>
                    <eventEntry>
                       <eventClass>fault</eventClass>
                    </eventEntry>
                    <eventEntry>
                       <eventClass>state</eventClass>
                    </eventEntry>
                    <eventEntry>
                       <eventClass>config</eventClass>
                    </eventEntry>
                    <eventEntry>
                      <eventClass>fault</eventClass>
                        <reportingElement>
                           <card>Ethernet0</card>
                        </reportingElement>
                    </eventEntry>
                 </events>
            </event>
       </filter>
    </create-subscription>
 </netconf:rpc>


5.2.  XPATH filters

   The following [XPATH] example illustrates selecting fault EventClass
   notifications that have severities of critical, major, or minor.  The
   filtering criteria evaluation is as follows:

   ((fault) & ((severity=critical) | (severity=major) | (severity =
   minor)))


   <netconf:rpc message-id="101"
                xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
         <create-subscription>
            <filter netconf:type="xpath"
              select="//eventEntry[(eventClass='fault' and
                    (severity='minor' or severity='major'
                     or severity='critical'))]"/>
        </create-subscription>
      </netconf:rpc>



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   The following example illustrates selecting state and config
   EventClasses or fault events that have severities of critical, major,
   or minor or come from card Ethernet0.  The filtering criteria
   evaluation is as follows:

   (( state | config) & ((fault & severity=critical) | (fault &
   severity=major) | (fault & severity = minor) | (fault &
   card=Ethernet0)))


<netconf:rpc message-id="101"
                xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
      <create-subscription>
         <filter netconf:type="xpath"
                     select="//eventEntry[(eventClass='fault' and
                     severity='minor') or
                     (eventClass='fault' and severity='major') or
                     (eventClass='fault' and severity='critical') or
                     (eventClass='fault' and card='Ethernet0') or
                      eventClass='state' or eventClass='config']"/>
     </create-subscription>
   </netconf:rpc>





























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6.  Security Considerations

   The security considerations from the base [NETCONF] document apply
   also to the Notification capability.

   The access control framework and the choice of transport will have a
   major impact on the security of the solution.

   Note that the <notification> elements are never sent before the
   transport layer and the netconf layer (capabilities exchange) have
   been established, and the manager has been identified and
   authenticated.

   It is recommended that care be taken to ensure the secure operation
   of the following commands:

   o  <create-subscription> invocation

   o  read-only data models

   o  read-write data models

   o  notification content

   One issue related to the notifications draft is the transport of data
   from non-netconf streams, such as syslog and SNMP.  Note that this
   data may be more vulnerable (or is not more vulnerable) when being
   transported over netconf than when being transported using the
   protocol normally used for transporting it, depending on the security
   credentials of the two subsystems.

   If a user does not have permission to view content via other NETCONF
   operations it does not have permission to access that content via
   Notifications.  If a user is not permitted to view one element in the
   content of the notification, the notification is not sent to that
   user.















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7.  IANA Considerations

   This document registers two URIs for the NETCONF XML namespace in the
   IETF XML registry [7].

   Following the format in RFC 3688, IANA has made the following
   registration.

   URI: urn:ietf:params:netconf:capability:notification:1.0

   URI: urn:ietf:params:xml:ns:netmod:notification

   Registrant Contact: The IESG.

   XML: N/A, the requested URI is an XML namespace.




































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8.  Acknowledgements

   Thanks to Gilbert Gagnon, Greg Wilbur and Kim Curran for providing
   their input into the early work on this document.  In addition, the
   editors would like to acknowledge input at the Vancouver editing
   session from the following people: Orly Nicklass, James Balestriere,
   Yoshifumi Atarashi, Glenn Waters, Alexander Clemm, Dave Harrington,
   Dave Partain, Ray Atarashi and Dave Perkins and the following
   additional people from the Montreal editing session: Balazs Lengyel,
   Phil Shafer, Rob Enns, Andy Bierman, Dan Romascanu, Bert Wijnen,
   Simon Leinen, Juergen Schoenwaelder, Hideki Okita, Vincent Cridlig,
   Martin Bjorklund, Olivier Festor, Radu State, Brian Trammell, William
   Chow.






































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9.  Normative References

   [NETCONF]  Enns, R., "NETCONF Configuration Protocol", RFC 4741,
              December 2006.

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", RFC 2026, BCP 9, October 1996.

   [RFC2119]  Bradner, s., "Key words for RFCs to Indicate Requirements
              Levels", RFC 2119, March 1997.

   [RFC2223]  Postel, J. and J. Reynolds, "Instructions to RFC Authors",
              RFC 2223, October 1997.

   [XML]      World Wide Web Consortium, "Extensible Markup Language
              (XML) 1.0", W3C XML, February 1998,
              <http://www.w3.org/TR/1998/REC-xml-19980210>.

   [XML Schema]
              Fallside, D. and P. Walmsley, "XML Schema Part 0: Primer
              Second Edition", W3C XML Schema, October 2004.

   [XPATH]    Clark, J. and S. DeRose, "XML Path Language (XPath)
              Version 1.0",
              W3C http://www.w3.org/TR/1999/REC-xpath-19991116,
              November 1999.

























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Authors' Addresses

   Sharon Chisholm
   Nortel
   3500 Carling Ave
   Nepean, Ontario  K2H 8E9
   Canada

   Email: schishol@nortel.com


   Hector Trevino
   Cisco
   Suite 400
   9155 E. Nichols Ave
   Englewood, CO  80112
   USA

   Email: htrevino@cisco.com
































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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


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   The IETF takes no position regarding the validity or scope of any
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   this document or the extent to which any license under such rights
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   Copies of IPR disclosures made to the IETF Secretariat and any
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   attempt made to obtain a general license or permission for the use of
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   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
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   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





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