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
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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.
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