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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: June 22, 2007                                             Cisco
                                                       December 19, 2006


                      NETCONF Event Notifications
                 draft-ietf-netconf-notification-05.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
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   This Internet-Draft will expire on June 22, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).













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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.  Event Notifications in NETCONF . . . . . . . . . . . . . .  5
     1.3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.4.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Notification-Related Operations  . . . . . . . . . . . . . . .  7
     2.1.  Subscribing to receive Event Notifications . . . . . . . .  7
       2.1.1.  <create-subscription>  . . . . . . . . . . . . . . . .  7
     2.2.  Sending Event Notifications  . . . . . . . . . . . . . . .  8
       2.2.1.  <notification> . . . . . . . . . . . . . . . . . . . .  8
     2.3.  Terminating the Subscription . . . . . . . . . . . . . . .  9
   3.  Supporting Concepts  . . . . . . . . . . . . . . . . . . . . . 10
     3.1.  Capabilities Exchange  . . . . . . . . . . . . . . . . . . 10
       3.1.1.  Capability Identifier . . . . . . . . . . . . . . . . 10
       3.1.2.  Capability Example . . . . . . . . . . . . . . . . . . 10
     3.2.  Event Streams  . . . . . . . . . . . . . . . . . . . . . . 10
       3.2.1.  Event Stream Definition  . . . . . . . . . . . . . . . 11
       3.2.2.  Event Stream Content Format  . . . . . . . . . . . . . 11
       3.2.3.  Default Event Stream . . . . . . . . . . . . . . . . . 11
       3.2.4.  Event Stream Sources . . . . . . . . . . . . . . . . . 12
       3.2.5.  Event Stream Discovery . . . . . . . . . . . . . . . . 12
       3.2.6.  Event Stream Subscription  . . . . . . . . . . . . . . 15
     3.3.  Subscriptions not Configuration Data . . . . . . . . . . . 15
     3.4.  Filter Dependencies  . . . . . . . . . . . . . . . . . . . 15
       3.4.1.  Named Profiles . . . . . . . . . . . . . . . . . . . . 15
       3.4.2.  Filtering  . . . . . . . . . . . . . . . . . . . . . . 16
     3.5.  Message Flow . . . . . . . . . . . . . . . . . . . . . . . 16
   4.  XML Schema for Event Notifications . . . . . . . . . . . . . . 17
   5.  Filtering examples . . . . . . . . . . . . . . . . . . . . . . 20
     5.1.  Subtree Filtering  . . . . . . . . . . . . . . . . . . . . 20
     5.2.  XPATH filters  . . . . . . . . . . . . . . . . . . . . . . 21
   6.  Notification Replay  . . . . . . . . . . . . . . . . . . . . . 23
     6.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . 23
     6.2.  Creating a Subscription with Replay  . . . . . . . . . . . 23
     6.3.  Replay Complete Notification . . . . . . . . . . . . . . . 24
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
   9.  Normative References . . . . . . . . . . . . . . . . . . . . . 28
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
   Intellectual Property and Copyright Statements . . . . . . . . . . 30









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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  |      |                                          |
    +-------------+      +------------------------------------------+


   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.

                                 Figure 1

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.

   Managed Object:  A collection of one of more Elements that define an
      abstract thing of interest.

   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.






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   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.

1.2.  Event Notifications in NETCONF

   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 out to interested
   parties to notify them that this event has occurred.

   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 to
   terminate 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.

   An NETCONF server is not required to process RPC requests on the
   session associated with the subscription until the notification
   subscription is done.  A capability may be advertised to announce
   that a server is able to process RPCs while a notification stream is
   active on a session.

1.3.  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.

1.4.  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



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   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 to 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.

      Named Profile:

         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







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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 start
         time is not present, this is not a replay subscription.

      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'.

   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.

2.2.  Sending Event Notifications

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

2.2.1.  <notification>

   Description:

      An event notification is sent to the initiator of 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 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:







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         Contains notification-specific tagged content.

   Response:

      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> ).









































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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 herein as a set of event notifications
   matching some forwarding criteria.

   System components 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.  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
   distribution to subscribed NETCONF clients.




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



                +-------+     +-------+
                |netconf|<--->|netconf|
             -> |server |     |client |
                +-------+     +-------+


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)

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 notification and
   their contents for this event stream is outside the scope of this
   document.



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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 list of all event streams configured on a device may be retrieved
   over a NETCONF session with sufficient privileges (e.g.
   administrator).  The information is retrieved by requesting the
   <eventStreams> subtree via a <get> operation.

   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:base:1.0"/>
     </filter>
   </get>
 </rpc>







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   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:base:1.0">
             <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>


3.2.5.2.  Stream Retrieval Schema


   <?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"
          elementFormDefault="qualified"
                    attributeFormDefault="unqualified">
     <xs:annotation>
       <xs:documentation xml:lang="en">
                        Schema for event streams
            </xs:documentation>
       <xs:appinfo>
         <nm:identity
              xmlns:nm="urn:ietf:params:xml:ns:netmod:base:1.0">
           <nm:Name>
                    NetconfNotificationSchema
           </nm:Name>



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           <nm:LastUpdated>
                    2006-09-06T09:30:47-05:00
           </nm:LastUpdated>
           <nm:Organization>IETF
           </nm:Organization>
           <nm:Description>
                     A schema that can be used to learn about current
                     event streams.
                  </nm:Description>
         </nm:identity>
       </xs:appinfo>
     </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="./draft-ietf-netconf-prot-12.xsd"/>


     <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"/>
                 <xs:element name="replaySupport" type="xs:boolean"/>
               </xs:sequence>
             </xs:complexType>
           </xs:element>
         </xs:sequence>
       </xs:complexType>
     </xs:element>
   </xs:schema>



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3.2.6.  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.

3.2.6.1.  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.

3.3.  Subscriptions not Configuration Data

   While it is possible to retrieve information about subscriptions via
   a get operation, subscriptions are not stored configuration.  They
   are non-persistent state information.  In this respect, they are
   comparable to NETCONF sessions.

   Named profiles, if used, are considered configuration data.

3.4.  Filter Dependencies

   Note that when multiple filters 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 is
   specified to look for data of a particular value, and the 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 filters are applied does not matter since
   the resulting set of notifications is the intersection of the set of
   notifications that pass each filtering criteria.

3.4.1.  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



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   been torn down.

3.4.2.  Filtering

   Just-in-time 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.

3.5.  Message Flow

   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.


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












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4.  XML Schema for Event Notifications


<?xml version="1.0" encoding="UTF-8"?>
  <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
          xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"
          xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0"
    targetNamespace="urn:ietf:params:xml:ns:netconf: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="xs:string" minOccurs="0">
                  <xs:annotation>
                    <xs:documentation>
                    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.
                    </xs:documentation>
                  </xs:annotation>
               </xs:element>



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              <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="xs:string" 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 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



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                    is terminated. Must be used with 'startTime'.
                  </xs:documentation>
                 </xs:annotation>
             </xs:element>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>

     <xs:element name="create-subscription"
                 type="createSubscriptionType"
                 substitutionGroup="netconf:rpcOperation">
        <xs:annotation>
            <xs:documentation>
               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
   <eventClasses> element identifying the event category (e.g. fault,
   state, config, etc.) and events have a <severity> element.

   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))


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



   The following example illustrates selecting fault, state, config



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   EventClasses or events which are related to card Ethernet0.  The
   filtering criteria evaluation is as follows:

   (fault | state | config | card=Ethernet0)


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


5.2.  XPATH filters

   The following example illustrates selecting fault EventClass
   notifications that have severities of critical, major, or minor.  In
   this example, neb represents the namespace for the event definitions
   schema.  The filtering criteria evaluation is as follows:

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


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



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   </rpc>


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

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


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























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6.   Notification Replay

6.1.  Overview

   Replay is the ability to create an event subscription that will
   resend recently sent 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.  If a client requests a replay of notifications that
   predate the oldest notification available, then the NETCONF server
   must return a warning message in the RPC reply and start replaying
   the notifications it does have available, within the other
   constraints, such as filtering, that the client has provided.  The
   warning message enables the NETCONF client to differentiate between
   the case that there were no notifications generated within a given
   time period from the case that no notifications are currently in the
   log from that period.

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

   This feature 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.

6.2.  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 while a notification has three potential times associated



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   it - the time it was generated, the time it was logged and the time
   it was sent out by the NETCONF server - the startTime and stopTime
   parameters are related to generation time.

   Negative Response:

      An <rpc-error> element is included in the <rpc-reply> if the
      startTime in replay request predates the oldest notification
      available to be replayed or if the stopTime is earlier then the
      startTime.

         Error-tag: start-time-too-early

         Error-type: protocol

         Error-severity: warning

         Error-info: none

         Error-message: Start time predates oldest available
         notification to be replayed

         Error-tag: start-stop-time-mismatch

         Error-type: protocol

         Error-severity: warning

         Error-info: none

         Error-message: stopTime predates startTime.

6.3.  Replay Complete Notification

   The following 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.













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

     <xs:element name="replayCompleteNotification" >
         <xs:annotation>
           <xs:documentation>
             This notification is sent to signal the end of a replay
             subscription.
           </xs:documentation>
         </xs:annotation>
       <xs:complexType>
           <xs:sequence>
             <xs:element name="eventClass" default="informational">
                 <xs:annotation>
                    <xs:documentation>
                        The event classification of this notification.
                    </xs:documentation>
                 </xs:annotation>
             </xs:element>
             <xs:element name="timeGenerated" type="xs:dateTime"/>
             <xs:element name="numberEventsReplayed" type="xs:integer"/>
          </xs:sequence>
       </xs:complexType>
    </xs:element>
 </xs:schema>























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7.  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  use of <kill-session>

   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.



















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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 Ennes, 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",
              ID draft-ietf-netconf-prot-12, February 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.






























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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 Internet Society (2006).

   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
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   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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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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   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
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Acknowledgment

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





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