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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: January 9, 2008 Cisco
July 8, 2007
NETCONF Event Notifications
draft-ietf-netconf-notification-08.txt.pre-release
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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 . . . . . . . . . . . . . . . . . . . . 19
3.6. Filter Mechanics . . . . . . . . . . . . . . . . . . . . . 19
3.6.1. Filtering . . . . . . . . . . . . . . . . . . . . . . 19
3.7. Message Flow . . . . . . . . . . . . . . . . . . . . . . . 19
4. XML Schema for Event Notifications . . . . . . . . . . . . . . 21
5. Filtering Examples . . . . . . . . . . . . . . . . . . . . . . 25
5.1. Subtree Filtering . . . . . . . . . . . . . . . . . . . . 25
5.2. XPATH filters . . . . . . . . . . . . . . . . . . . . . . 28
6. Security Considerations . . . . . . . . . . . . . . . . . . . 30
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 32
9. Normative References . . . . . . . . . . . . . . . . . . . . . 33
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 34
A.1. Version -08 . . . . . . . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37
Intellectual Property and Copyright Statements . . . . . . . . . . 38
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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: An agreement and method to receive event notifications
over a NETCONF session. 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
[NETCONF]. 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.
Filter: A parameter that indicates which subset of all possible
events are of interest.
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 will not read RPC requests, by default, 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. 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 (ie, not
too short)
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. See section 3.6 for more
information on filters.
Start Time:
A parameter used to trigger the replay feature and indicate
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 than the
log can support, the replay will begin with the earliest
available notification. This parameter is of type dateTime.
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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 and be later
than '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: <badElement>: 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:
Tag: operation-failed
Error-type: protocol
Severity: error
Error-info: none
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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
xmlns="urn:ietf:params:netconf:capability:notification:1.0">
</create-subscription>
</netconf:rpc>
Figure 2
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:
Contains notification-specific tagged content. The content of
the data tag is beyond the scope of this document.
Response:
No response. Not applicable.
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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>
Figure 3
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-
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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. 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 the <name>
element is mandatory and its value is unique within the scope of a
NETCONF server. 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>
Figure 5
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>
<replayLogStartTime>2007-07-08T00:00:00Z</replayLogStartTime>
</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>
<replayLogStartTime>2007-07-01T00:00:00Z</replayLogStartTime>
</stream>
</eventStreams>
</data>
</rpc-reply>
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Figure 6
3.2.5.2. Event Stream Subscription
A NETCONF client may request from the NETCONF server the list of
event streams available 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, or in some cases send them
for the first time to a particular NETCONF client. 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.
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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. Whether or
not a stream supports replay can be discovered by doing a <get>
operation on the eventStreams element of the Notification Management
Schema. This schema also provides the replayLogStartTime element to
indicate the earliest available logged notification.
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 replayComplete 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
replayComplete 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 replayComplete notification is the last notification sent over a
replay subscription. It indicates that replay is complete. After
this notification is received the subscription is terminated and the
session becomes normal command-response 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. It also contains the definition of the replayComplete, which
is sent to indicate that an event replay has sent all applicable
notifications."
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<?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"
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. 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=
"http://www.iana.org/assignments/xml-registry/schema/netconf.xsd"/>
<xs:import namespace=
"urn:ietf:params:netconf:capability:notification:1.0"
schemaLocation=
"http://www.iana.org/assignments/xml-registry/schema/notification.xsd"/>
<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>
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<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:element name="replayLogStartTime"
type="xs:dateTime" minOccurs="0">
<xs:annotation>
<xs:documentation>
The start time of the log used to
support the replay function. This
object MUST be present if replay is
supported.
</xs:documentation>
</xs:annotation>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
<xs:complexType name="ReplayCompleteNotificationType">
<xs:complexContent>
<xs:extension base="ncEvent:NotificationContentType"/>
</xs:complexContent>
</xs:complexType>
<xs:element name="replayComplete"
type="manageEvent:ReplayCompleteNotificationType"
substitutionGroup="ncEvent:notificationContent">
<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:schema>
Figure 7
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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.
3.6. Filter Mechanics
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 data
item is not present within a particular event notification for its
value to be checked against, the notification 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.
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. Filtering
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=
"http://www.iana.org/assignments/xml-registry/schema/netconf.xsd"/>
<!-- ************** 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
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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>
<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.
</xs:documentation>
</xs:annotation>
</xs:element>
<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 is terminated. Must be used
with 'startTime'.
</xs:documentation>
</xs:annotation>
</xs:element>
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</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<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>
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="NotificationContentType"/>
<xs:element name="notificationContent"
type="NotificationContentType" abstract="true"/>
<xs:complexType name="NotificationType">
<xs:sequence>
<xs:element ref="notificationContent"/>
</xs:sequence>
</xs:complexType>
<xs:element name="notification" type="NotificationType"/>
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</xs:schema>
Figure 9
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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
<event xmlns="http://example.com/event/1.0">
<eventClass>fault</eventClass>
<reportingEntity>
<card>Ethernet0</card>
</reportingEntity>
<severity>major</severity>
</event>
<event xmlns="http://example.com/event/1.0">
<eventClass>fault</eventClass>
<reportingEntity>
<card>Ethernet2</card>
</reportingEntity>
<severity>critical</severity>
</event>
<event xmlns="http://example.com/event/1.0">
<eventClass>fault</eventClass>
<reportingEntity>
<card>ATM1</card>
</reportingEntity>
<severity>minor</severity>
</event>
<event xmlns="http://example.com/event/1.0">
<eventClass>state</eventClass>
<reportingEntity>
<card>Ethernet0</card>
</reportingEntity>
<operState>enabled</operState>
</event>
Figure 10
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 netconf:message-id="101"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<create-subscription
xmlns="urn:ietf:params:netconf:capability:notification:1.0">
<filter netconf:type="subtree">
<event xmlns="http://example.com/event/1.0">
<eventClass>fault</eventClass>
<severity>critical</severity>
</event>
<event xmlns="http://example.com/event/1.0">
<eventClass>fault</eventClass>
<severity>major</severity>
</event>
<event xmlns="http://example.com/event/1.0">
<eventClass>fault</eventClass>
<severity>minor</severity>
</event>
</filter>
</create-subscription>
</netconf:rpc>
Figure 11
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 netconf:message-id="101"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<create-subscription
xmlns="urn:ietf:params:netconf:capability:notification:1.0">
<filter netconf:type="subtree">
<event xmlns="http://example.com/event/1.0">
<eventClass>fault</eventClass>
</event>
<event xmlns="http://example.com/event/1.0">
<eventClass>state</eventClass>
</event>
<event xmlns="http://example.com/event/1.0">
<eventClass>config</eventClass>
</event>
<event xmlns="http://example.com/event/1.0">
<eventClass>fault</eventClass>
<reportingElement>
<card>Ethernet0</card>
</reportingElement>
</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 netconf:message-id="101"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<create-subscription
xmlns="urn:ietf:params:netconf:capability:notification:1.0">
<filter netconf:type="xpath"
xmlns:ex="http://example.com/event/1.0"
select="/ex:event[ex:eventClass='fault' and
(ex:severity='minor' or ex:severity='major'
or ex:severity='critical')]"/>
</create-subscription>
</netconf:rpc>
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Figure 13
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 netconf:message-id="101"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<create-subscription
xmlns="urn:ietf:params:netconf:capability:notification:1.0">
<filter netconf:type="xpath"
xmlns:ex="http://example.com/event/1.0"
select="/ex:event[
ex:eventClass='fault' and ex:severity='minor') or
(ex:eventClass='fault' and ex:severity='major') or
ex:eventClass='fault' and ex:severity='critical') or
(ex:eventClass='fault' and
ex:reportingElement/ex:card='Ethernet0') or
ex:eventClass='state' or
ex:eventClass='config']"/>
</create-subscription>
</netconf:rpc>
Figure 14
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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.
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. 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. The NETCONF server is responsible for providing
access control to stream content.
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.
If a subscription is created with a stopTime, the NETCONF session
will return to being a normal command-response NETCONF session when
the replay is completed. It is the responsibility of the NETCONF
client to close off this session when it is no longer of use.
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7. IANA Considerations
This document registers two URIs for the NETCONF XML namespace in the
IETF XML registry [RFC3688].
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.
[RFC3688] Bradner, s., "The IETF XML Registry", RFC 3688, January
2004.
[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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Appendix A. Change Log
A.1. Version -08
1. Removed named profiles
2. Removed eventClass that was accidentally included in the
definition of the replayComplete notification
3. Deleted data wrapper from notification
4. Changed replayLogStartTime to have a minOccurs of 0. It will
only be there when replay is supported. Verify examples in
section 3.2.5.1 are correct with respect to this element.
5. Error codes in section 2.1.1, fixed formatting issue
6. Moved replayComplete to not be under <netconf>
7. Section 2.1, fixed capitalization
8. In figure 4, the line was pushed out by 'system components',
fixed this.
9. On page 8, replaced "If the startTime specified is earlier then
the" with 'If the startTime specified is earlier than the"
10. Updated some name spaces and schemaLocations as per Andy's June
3rd email.
11. Added discussion of replayLogStartTime to draft in section 3.3.1
as follows "Whether or not a stream supports replay can be
discovered by doing a <get> operation on the eventStreams
elements of the Notification Management Schema. This schema
also provides the replayLogStartTime element to indicate the
earliest available logged notification."
12. Removed most of the uses of the phrase 'Note that'. I kept two
uses that prevent sentences from starting with either a lower
case letter or an angle bracket.
13. In section 3.6 replaced "it will be filtered out" with "the
notification will be filtered out"
14. In section 3.4, replaced "and the query" with "and to query"
15. Replaced 3 instances of "replay complete notification" with
"replayComplete notification"
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16. In section 3.3.2, replaced "normal NETCONF session" with "normal
command-response NETCONF session"
17. In section 3.3.1, replaced "create an event subscription that
will resend recently generated notification" with "create an
event subscription that will resend recently generated
notification, or is some cases send them for the first time to a
particular NETCONF client."
18. In section 3.2.5.2, s/available event streams to/event streams
available to/
19. In one spot, changed snmp to SNMP (the other gets deleted)
20. In section 3.2.5.1 s/where <name> element is/where the <name>
element is/
21. In section 3.2.5.1, clarified that "value is unique" - within
the scope of a NETCONF server.
22. In section 2.1.1, clarified that stopTime cannot preceded start
time.
23. In section 2.1.1, in Start Time s/indicates/indicate/
24. In section 2.1.1, in Filter: s/This is mutually exclusive/The
filter parameter is mutually exclusive/ ("this" could refer to
the behavior described in the previous sentence.)
25. In section 1.4, third bullet, replaced "syslog and SNMP are
rather constrained in terms of message sizes)" with (ie, not too
short)
26. In section 1.4, made all bullets start with capital leters.
27. Added definition of Filter to section 1.1
28. In section 1.1, improved the definition of subscription with "An
agreement and method to receive event notifications over a
NETCONF session."
29. In section 1.1, in the definition of operation, added a
reference to [NETCONF].
30. Created a change log section
31. Fixed reference to IETF XML Registry in IANA Considerations
section.
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32. In section 3.3.3, deleted "This notification will only be sent
if a 'stopTime' was specified when the replay subscription was
created."
33. Added text to the security considerations section that says "If
a subscription is created with a stopTime, the NETCONF session
will return to being a normal command-response NETCONF session
when the replay is completed. It is the responsibility of the
NETCONF client to close off this session when it is no longer of
use".
34. Update examples in section 5 to get rid of extra wrapper tag.
35. In section 2.1, replace "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." with "A NETCONF server is will
not read RPC requests, by default, on the session associated
with the subscription until the notification subscription is
done.
36. Updated the notification definition and the replyComplete
notification definition to use a substitution group.
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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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