Network Working Group S. Chisholm
Internet-Draft K. Curran
Expires: July 12, 2006 Nortel
H. Trevino
Cisco
January 8, 2006
NETCONF Event Notifications
draft-ietf-netconf-notification-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This memo defines a framework for sending asynchronous messages, or
event notifications in NETCONF. It defines both the operations
necessary to support this concept, and also discusses implications
for the mapping to application protocols.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Definition of Terms . . . . . . . . . . . . . . . . . . . 4
1.2 Event Notifications in NETCONF . . . . . . . . . . . . . . 5
2. Event-Related Operations . . . . . . . . . . . . . . . . . . . 6
2.1 Subscribing to receive Events . . . . . . . . . . . . . . 6
2.1.1 create-subscription . . . . . . . . . . . . . . . . . 6
2.2 Sending Event Notifications . . . . . . . . . . . . . . . 7
2.2.1 Events . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Changing the Subscription . . . . . . . . . . . . . . . . 8
2.3.1 modify-subscription . . . . . . . . . . . . . . . . . 9
2.4 Terminating the Subscription . . . . . . . . . . . . . . . 10
2.4.1 cancel-subscription . . . . . . . . . . . . . . . . . 10
3. Supporting Concepts . . . . . . . . . . . . . . . . . . . . . 11
3.1 Capabilities Exchange . . . . . . . . . . . . . . . . . . 11
3.2 Querying Subscription Properties . . . . . . . . . . . . . 11
3.3 RPC One-way Messages . . . . . . . . . . . . . . . . . . . 14
3.4 User-Specified Filters . . . . . . . . . . . . . . . . . . 14
3.4.1 Named Profiles . . . . . . . . . . . . . . . . . . . . 15
3.4.2 Filtering . . . . . . . . . . . . . . . . . . . . . . 15
3.5 Event Classes . . . . . . . . . . . . . . . . . . . . . . 15
3.6 Defining Event Notifications . . . . . . . . . . . . . . . 16
3.7 Interleaving Messages . . . . . . . . . . . . . . . . . . 16
4. XML Schema for Event Notifications . . . . . . . . . . . . . . 18
5. Mapping to Application Protocols . . . . . . . . . . . . . . . 23
5.1 SSH . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.2 BEEP . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.2.1 One-way Messages in Beep . . . . . . . . . . . . . . . 24
5.3 SOAP . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.3.1 A NETCONF over Soap over HTTP Example . . . . . . . . 25
6. Filtering examples . . . . . . . . . . . . . . . . . . . . . . 28
6.1 Event Classes . . . . . . . . . . . . . . . . . . . . . . 28
6.2 Subtree Filtering . . . . . . . . . . . . . . . . . . . . 28
6.3 XPATH filters . . . . . . . . . . . . . . . . . . . . . . 30
7. Security Considerations . . . . . . . . . . . . . . . . . . . 32
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 34
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 35
A. Potential Event Content . . . . . . . . . . . . . . . . . . . 36
A.1 Event Identifier . . . . . . . . . . . . . . . . . . . . . 36
A.2 Resource Instance . . . . . . . . . . . . . . . . . . . . 36
A.3 Event Time . . . . . . . . . . . . . . . . . . . . . . . . 36
A.4 Perceived Severity . . . . . . . . . . . . . . . . . . . . 36
A.5 Probable Cause . . . . . . . . . . . . . . . . . . . . . . 37
A.6 Specific Problem . . . . . . . . . . . . . . . . . . . . . 37
A.7 Trend Indication . . . . . . . . . . . . . . . . . . . . . 37
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A.8 Additional Alarm Text . . . . . . . . . . . . . . . . . . 37
A.9 Threshold Identifier . . . . . . . . . . . . . . . . . . . 37
A.10 Threshold Type . . . . . . . . . . . . . . . . . . . . . . 38
A.11 Observed Value . . . . . . . . . . . . . . . . . . . . . . 38
A.12 State Change Information . . . . . . . . . . . . . . . . . 38
B. Configuration Event Class Notifications . . . . . . . . . . . 39
B.1 Types of Configuration Events . . . . . . . . . . . . . . 39
B.2 Config Event Notification Structure . . . . . . . . . . . 40
B.3 Configuration Event Content . . . . . . . . . . . . . . . 42
B.3.1 Target Datastore . . . . . . . . . . . . . . . . . . . 42
B.3.2 User Info . . . . . . . . . . . . . . . . . . . . . . 42
B.3.3 Data Source . . . . . . . . . . . . . . . . . . . . . 42
B.3.4 Operation . . . . . . . . . . . . . . . . . . . . . . 42
B.3.5 Context . . . . . . . . . . . . . . . . . . . . . . . 42
B.3.6 Entered Command . . . . . . . . . . . . . . . . . . . 43
B.3.7 New Config . . . . . . . . . . . . . . . . . . . . . . 43
B.3.8 Old Config . . . . . . . . . . . . . . . . . . . . . . 43
B.3.9 Non-netconf commands in configuration notifications . 43
B.4 Design Alternative . . . . . . . . . . . . . . . . . . . . 43
B.4.1 Server Session Initiation . . . . . . . . . . . . . . 43
B.4.2 Establishment . . . . . . . . . . . . . . . . . . . . 44
B.4.3 Teardown . . . . . . . . . . . . . . . . . . . . . . . 44
B.4.4 Suspend And Resume . . . . . . . . . . . . . . . . . . 45
B.4.5 Lifecycle . . . . . . . . . . . . . . . . . . . . . . 45
C. NETCONF Event Notifications and Syslog . . . . . . . . . . . . 46
C.1 Leveraging Syslog Field Definitions . . . . . . . . . . . 46
C.1.1 Field Mapping . . . . . . . . . . . . . . . . . . . . 47
C.1.2 Severity Mapping . . . . . . . . . . . . . . . . . . . 48
C.2 Syslog within NETCONF Events . . . . . . . . . . . . . . . 48
C.2.1 Motivation . . . . . . . . . . . . . . . . . . . . . . 48
C.2.2 Embedding syslog messages in a NETCONF Event . . . . . 48
C.2.3 Supported Forwarding Options . . . . . . . . . . . . . 49
Intellectual Property and Copyright Statements . . . . . . . . 51
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1. Introduction
NETCONF [NETCONF-PROTO] can be conceptually partitioned into four
layers:
Layer Example
+-------------+ +-----------------------------+
| Content | | Configuration data |
+-------------+ +-----------------------------+
| |
+-------------+ +-----------------------------+
| Operations | | <get-config>, <edit-config> |
+-------------+ +-----------------------------+
| |
+-------------+ +-----------------------------+
| RPC | | <rpc>, <rpc-reply> |
+-------------+ +-----------------------------+
| |
+-------------+ +-----------------------------+
| Application | | BEEP, SSH, SSL, console |
| Protocol | | |
+-------------+ +-----------------------------+
This document defines a framework for sending asynchronous messages,
or event notifications in NETCONF. It defines both the operations
necessary to support this concept, and also discusses implications
for the mapping to application protocols.
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 RFC 2119 [3].
Element: An XML Element[XML].
Managed Entity: A node, which supports NETCONF[NETCONF] and has
access to management instrumentation. This is also known as the
NETCONF server.
Managed Object: A collection of one of more Elements that define an
abstract thing of interest.
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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 an explicit command to
cancel the subscription is sent. 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, but can be modified later using a modify
subscription command.
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2. Event-Related Operations
2.1 Subscribing to receive Events
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.
It is possible to create more than one event notification
subscription on a single underlying connection. Each event
notification subscription therefore has its own unique identifier.
Content for an event notification subscription can be selected by
specifying which event classes are of interest and /or by applying
user-specified filters.
2.1.1 create-subscription
<create-subscription>
Description:
This command initiates an event notification subscription which
will send asynchronous event notifications to the initiator of the
command until the <cancel-subscription > command is sent.
Parameters:
Event Classes:
An optional parameter that indicates which event classes are of
interest. If not present, events of all classes 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. These filter parameters can
only be modified using the modify-subscription command.
Named Profile
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An optional parameter that points to a separately defined
filter profile. If not present, no additional filtering will
be applied. If the separate definition of these filters is
updated, then these changes will be reflected in the filtered
events on this subscription.
Positive Response:
If the NETCONF server can satisfy the request, the server sends an
<rpc-reply> element containing a <data> element containing the
subscription ID.
Negative Response:
An <rpc-error> element is included within the <rpc-reply> if the
request cannot be completed for any reason.
2.2 Sending Event Notifications
Once the subscription has been set up, the NETCONF server sends the
event notifications asynchronously along the connection.
Notifications are tagged with event classes, subscription ID,
sequence number, and date and time.
Events
<notification>
Description:
An event notification is sent to the initiator of an <create-
subscription> command asynchronously when an event of interest to
them has occurred. An event notification is a complete XML
document.
Parameters:
Event Classes:
The event class or classes associated with this event
notification
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Subscription Id:
A unique identifier for this event subscription
Sequence Number:
A sequentially increasing number to uniquely identify event
notifications for this subscription. It starts at 0, always
increases by just one and rolls back to 0 after its maximum
value is reached.
Date and Time:
The date and time that the event notification was sent by the
NETCONF server.
Positive Response:
No response.
Negative Response:
No response.
2.2.1.1 Event Notification
The NETCONF Event notification structure is shown in the following
figure.
_____________
|RPC-Header||
|__________||
|message-id||
|__________||
____________________________________________________________________
|| Event Header || Data |
||__________________________________________________________||______|
|| subscriptionId| eventClasses| sequenceNumber| dataAndTime|| |
||_______________|_____________|_______________|____________||______|
2.3 Changing the Subscription
After an event notification subscription has been established, the
NETCONF client can initiate a request to change properties of the
event notification subscription. This prevents loss of event
notifications that might otherwise occur during a tear down and
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recreation of the event notification subscription. This command is
responded to by the NETCONF server
2.3.1 modify-subscription
<modify-subscription>
Description:
Change properties of the event notification subscription.
Parameters:
Subscription Id:
A unique identifier for this event subscription.
Event Classes:
An optional parameter that indicates which Event Classes are of
interest. If not present, events of all classes will be sent.
Filter:
An optional parameter that indicates which subset of all
possible events that are of interest. The format is the same
filter used for other NETCONF commands. If not present, all
events not precluded by other parameters will be sent. These
filter parameters can only be modified using the modify-
subscription command.
Named Profile:
An optional parameter that points to separately defined filter
profile. If not present, no additional filtering will be
applied. If the separate definition of these filters is
updated, then these changes will be reflected in the events
seen on this subscription.
Positive Response:
If the NETCONF server was able to satisfy the request, an <rpc-
reply> is sent that includes an <ok> element.
Negative Response:
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An <rpc-error> element is included within the <rpc-reply> if the
request cannot be completed for any reason.
2.4 Terminating the Subscription
Closing of the event notification subscription is initiated by the
NETCONF client. The specific subscription to be closed is specified
using a subscription ID. The NETCONF server responds. Note that the
NETCONF session may also be torn down for other reasons and this will
also result in the subscription being cancelled, but is not subjected
to the behaviour of this command.
2.4.1 cancel-subscription
<cancel-subscription>
Description:
Tear down the event notification subscription.
Parameters:
Subscription Id:
A unique identifier for this event notification subscription.
Positive Response:
If the NETCONF server was able to satisfy the request, an <rpc-
reply> is sent that includes an <ok> element.
Negative Response:
An <rpc-error> element is included within the <rpc-reply> if the
request cannot be completed for any reason.
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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.
"urn:ietf:params:xml:ns:netconf:notification:1.0"
For 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:xml:ns:netconf:capability:startup:1.0
</capability>
<capability>
urn:ietf:params:xml:ns:netconf:notification:1.0
</capability>
</capabilities>
<session-id>4</session-id>
</hello>
3.2 Querying Subscription Properties
The following Schema can be used to retrieve information about active
event notification subscriptions
<xs:schema
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns=
"urn:ietf:params:xml:ns:netconf:subscription:1.0"
targetNamespace=
"urn:ietf:params:xml:ns:netconf:subscription:1.0"
xmlns:netconf=
"urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:ncEvent=
"urn:ietf:params:xml:ns:netconf:notification:1.0"
elementFormDefault="qualified"
attributeFormDefault="unqualified" xml:lang="en">
<annotation>
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<documentation xml:lang="en">
Schema for reporting on Event Subscriptions
</documentation>
<appinfo>
<nm:identity
xmlns:nm="urn:ietf:params:xml:ns:netmod:base:1.0">
<nm:Name>NetConf State Schema</nm:Name>
<nm:LastUpdated>2005-11-30T09:30:47-05:00
</nm:LastUpdated>
<nm:Organization>IETF</nm:Organization>
<nm:Description>
A schema that can be used to learn about current
NetConf Event Subscriptions
</nm:Description>
</nm:identity>
</appinfo>
</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:notification:1.0"
schemaLocation="ietf-netconf-notification.xsd"/>
<xs:import namespace="urn:ietf:params:xml:ns:netconf:base:1.0"
schemaLocation="draft-ietf-netconf-prot-09.xsd"/>
<xs:element name="netconfSubscription">
<xs:complexType>
<xs:sequence maxOccurs="unbounded">
<xs:element name="session-id"
type="netconf:SessionId" >
<xs:annotation>
<xs:documentation xml:lang="en">
The session id associated with this subscription.
</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element name="subscriptionID"
type="ncEvent:SubscriptionID" >
<xs:annotation>
<xs:documentation xml:lang="en">
The subscription id associated with this subscription.
</xs:documentation>
</xs:annotation>
</xs:element>
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<xs:element name="eventClasses">
<xs:annotation>
<xs:documentation xml:lang="en">
The event classes associated with this subscription.
</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:sequence minOccurs="0" maxOccurs="unbounded">
<xs:element ref="ncEvent:EventClass"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="filter"
type="netconf:filterInlineType" minOccurs="0">
<xs:annotation>
<xs:documentation xml:lang="en">
The filters associated with this subscription.
</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element name="namedProfile"
type="xs:string" minOccurs="0">
<xs:annotation>
<xs:documentation xml:lang="en">
The named profile associated with this subscription.
Note that the contents of the named profile may have
changed since it was last applied
</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element name="lastModified"
type="xs:dateTime" >
<xs:annotation>
<xs:documentation xml:lang="en">
The last time this subscription was modified. If it has
not been modified since creation, this is the time of
subscription creation.
</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element name="messagesSent"
type="xs:integer" minOccurs="0">
<xs:annotation>
<xs:documentation xml:lang="en">
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A count of event notifications sent along this connection
since the subscription was created.
</xs:documentation>
</xs:annotation>
</xs:element>
<xs:element name="lastSequenceNumber"
type="xs:integer" minOccurs="0">
<xs:annotation>
<xs:documentation xml:lang="en">
The sequence number of the last event notification sent to
this subscription
</xs:documentation>
</xs:annotation>
</xs:element>
<xs:key name="uniqueSubscription">
<xs:selector xpath=".//subscription"/>
<xs:field xpath="session-id"/>
<xs:field xpath="subscriptionID"/>
</xs:key>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
3.3 RPC One-way Messages
In order to support the concept that each individual event
notification is a well-defined XML-document that can be processed
without waiting for all events to come in, it makes sense to define
events, not as an endless reply to a subscription command, but as
independent messages that originate from the NETCONF server. In
order to support this model, this memo introduces the concept of a
one-way RPC message.
The one-way RPC message is similar to the two-way RPC message, except
that no response is expected to the command. In the case of event
notification, this RPC will originate from the NETCONF server, and
not the NETCONF client.
3.4 User-Specified Filters
Note that when multiple filters are specified, they are applied
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collectively, so event notifications needs 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 for its value to be checked,
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.
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 or
modified. Note that changes to the profile after the subscription
has been created will have no effect unless a modify subscription
command is issued. Since named profiles exist outside of the
subscription, they persist after the subscription has been cancelled.
Just-in-time filtering is explicitly stated when the event
notification subscription is created. It can only be changed using
the modify subscription command. This is specified via the Filter
parameter. Filters only exist as parameters to the subscription.
3.5 Event Classes
Events can be broadly classified into one more event classes. Each
event class identifies a set of event notifications which share
important characteristics, such being generated from similar events
or sharing much of the same content.
The initial set of event classes is fault, configuration, state,
audit, data, maintenance, metrics, security, information and
heartbeat.
A fault event notification is generated when a fault condition (error
or warning) occurs. A fault event may result in an alarm. Examples
of fault events could be a communications alarm, environmental alarm,
equipment alarm, processing error alarm, quality of service alarm, or
a threshold crossing event. See RFC3877 and RFC2819 for more
information.
A configuration event, alternatively known as an inventory event, is
used to notify that hardware, software, or a service has been added/
changed/removed. In keeping aligned with NETCONF protocol
operations, configuration events may included copy configuration
event, delete configuration event, or the edit configuration event
(create, delete, merge, replace).
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A state event indicates a change from one state to another, where a
state is a condition or stage in the existence of a managed entity.
State change events are seen in many specifications. For Entity
state changes, see [Entity-State-MIB] for more information.
Audit events provide event of very specific actions within a managed
device. In isolation an audit events provides very limited data. A
collection of audit information forms an audit trail.
A data dump event is an asynchronous event containing information
about a system, its configuration, state, etc.
A maintenance event signals the beginning, process or end of an
action either generated by a manual or automated maintenance action.
A metrics event contains a metric or a collection of metrics. This
includes performance metrics.
A heart beat event is sent periodically to enable testing that the
communications channel is still functional. It behaves much like the
other event classes, with the exception that implementations may not
want to include an event log, if supported. Although widely used
throughout the industry, no current corresponding work within the
IETF. However, other standards bodies such as the TeleManagement
Forum have similar definitions.
An Information event is something that happens of interest which is
within the expected operational behaviour and not otherwise covered
by another class.
3.6 Defining Event Notifications
Event Notifications are defined ahead of time by defining an XML
element and assigning it to particular event classes. This will be
done using an "eventClasses" attribute.
3.7 Interleaving Messages
While each NETCONF message must be a complete XML document, the
design of the event system allows for the interleaving of complete
asynchronous event notifications with complete synchronous messages.
It is possible to still send command-response type messages such as
<modify-subscription> while events are being generated. The only
restriction is that each message must be complete
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The following sequence diagram demonstrates an example NETCONF
session where after basic session establishment and capability
exchange, NETCONF client (C), subscribes to receive event
notifications. The NETCONF server (S), starts sending event
notifications as events of interest happen within the system. The
NETCONF client decides to change the characteristics of their event
subscription so sends a <modify-subscription> command. Before the
NETCONF server, receives this command, another event is generated and
the NETCONF server starts to send the event notification. The
NETCONF server finishes sending this event notification before
processing the <modify-subscription> command and sending the reply.
C S
| |
| capability exchange |
|-------------------------->|
|<------------------------->|
| |
| <create-subscription> |
|-------------------------->|
|<--------------------------|
| |
| <notification> |
|<--------------------------|
| |
| <notification> |
|<--------------------------|
| |
| <modify-subscription> |
|-------------------------->| (buffered)
| <notification> |
|<--------------------------|
| <rpc-reply> |
|<--------------------------|
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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" />
<!-- ************** Type definitions ***********************-->
<xs:simpleType name="SubscriptionID">
<xs:annotation>
<xs:documentation>
The unique identifier for this particular subscription within
the session.
</xs:documentation>
</xs:annotation>
<xs:restriction base="xs:string"/>
</xs:simpleType>
<xs:simpleType name="SequenceNumber">
<xs:annotation>
<xs:documentation>
A monotonically increasing integer. Starts at 0.
Always increases by just one. Roll back to 0 after maximum
value is reached.
</xs:documentation>
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</xs:annotation>
<xs:restriction base="xs:integer"/>
</xs:simpleType>
<xs:complexType name="EventClassType"/>
<xs:element name="EventClass"
type="EventClassType" abstract="true"/>
<xs:element name="fault" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:element name="information" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:element name="state" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:element name="configuration" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:element name="data" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:element name="maintenance" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:element name="metrics" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:element name="security" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:element name="heartbeat" type="EventClassType"
substitutionGroup="EventClass"/>
<xs:complexType name="EventClasses">
<xs:sequence maxOccurs="unbounded">
<xs:element ref="EventClasses" />
</xs:sequence>
</xs:complexType>
<!-- ************** Symmetrical Operations ********************-->
<!--
<create-subscription> operation
-->
<xs:complexType name="createSubscriptionType">
<xs:complexContent>
<xs:extension base="netconf:rpcOperationType">
<xs:sequence>
<xs:element name="event-classes"
minOccurs="0">
<xs:complexType>
<xs:complexContent>
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<xs:extension base="EventClasses"/>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element name="filter"
type="netconf:filterInlineType" minOccurs="0"/>
<xs:element name="named-profile"
type="xs:string" minOccurs="0"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="create-subscription"
type="createSubscriptionType"
substitutionGroup="netconf:rpcOperation"/>
<!--
<modify-subscription> operation
-->
<xs:complexType name="modifySubscriptionType">
<xs:complexContent>
<xs:extension base="netconf:rpcOperationType">
<xs:sequence>
<xs:element name="subscription-id"
type="SubscriptionID" />
<xs:element name="event-classes"
minOccurs="0">
<xs:complexType>
<xs:complexContent>
<xs:extension base="EventClasses"/>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element name="filter"
type="netconf:filterInlineType"
minOccurs="0"/>
<xs:element name="named-profile"
type="xs:string" minOccurs="0"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="modify-subscription"
type="modifySubscriptionType"
substitutionGroup="netconf:rpcOperation"/>
<!--
<cancel-subscription> operation
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-->
<xs:complexType name="cancelSubscriptionType">
<xs:complexContent>
<xs:extension base="netconf:rpcOperationType">
<xs:sequence>
<xs:element name="subscription-id"
type="SubscriptionID" />
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="cancel-subscription"
type="cancelSubscriptionType"
substitutionGroup="netconf:rpcOperation"/>
<!-- ************** One-way Operations ******************-->
<xs:complexType name="rpcOneWayType">
<xs:group ref="rpc-one-way"/>
<xs:attribute name="message-id" type="xs:string"
use="optional"/>
</xs:complexType>
<xs:group name="rpc-one-way">
<xs:sequence>
<xs:element name="data" type="netconf:dataInlineType"
minOccurs="0"/>
</xs:sequence>
</xs:group>
<!--
<Event> operation
-->
<xs:complexType name="NotificationType">
<xs:complexContent>
<xs:extension base="rpcOneWayType">
<xs:sequence>
<xs:element name="subscription-id"
type="SubscriptionID"/>
<xs:element name="event-classes" type="EventClasses"/>
<xs:element name="sequence-number"
type="SequenceNumber"/>
<xs:element name="date-time" type="xs:dateTime">
<xs:annotation>
<xs:documentation>
The date and time that the event notification was
sent by the netconf server.
</xs:documentation>
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</xs:annotation>
</xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:element name="notification" type="NotificationType"/>
</xs:schema>
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5. Mapping to Application Protocols
Currently, the NETCONF family of specification allows for running
NETCONF over a number of application protocols, some of which support
multiple configurations. Some of these options will be better suited
for supporting event notifications then others.
Session establishment and two-way messages are based on the NETCONF
over SSH transport mapping [NETCONF-SSH]
One-way messages are supported as follows: Once the session has been
established and capabilities have been exchanged, the server may send
complete XML documents to the NETCONF client containing rpc-one-way
elements. No response is expected from the NETCONF client.
As the other examples in [NETCONF-SSH] illustrate, a special
character sequence, MUST be sent by both the client and the server
after each XML document in the NETCONF exchange. This character
sequence cannot legally appear in an XML document, so it can be
unambiguously used to identify the end of the current document in the
event notification of an XML syntax or parsing error, allowing
resynchronization of the NETCONF exchange.
The NETCONF over SSH session to receive an event notification might
look like this:
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<?xml version="1.0" encoding="UTF-8"?>
<rpc-one-way message-id="105"
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<notification>
<subscription-id>123456</subscription-id>
<event-class><configuration/><audit/></event-classes>
<sequence-number>2</sequence-number>
<date-time>2000-01-12T12:13:14Z</date-time>
<data>
<user>Fred Flinstone</user>
<operation>
<edit-config>
<target>
<running/>
</target>
<config>
<top xmlns="http://example.com/schema/1.2/config">
<interface>
<name>Ethernet0/0</name>
<mtu>1500</mtu>
</interface>
</top>
</config>
</edit-config>
</operation>
</data>
</notification>
</rpc-one-way>
]]>
]]>
Session establishment and two-way messages are based on the NETCONF
over BEEP transport mapping NETCONF-BEEP
5.2.1 One-way Messages in Beep
One-way messages can be supported either by mapping to the existing
one-to-many BEEP construct or by creating a new one-to-none
construct.
This area is for future study.
5.2.1.1 One-way messages via the One-to-many Construct
Messages in one-to-many exchanges: "rcp", "rpc-one-way", "rpc-reply"
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Messages in positive replies: "rpc-reply", "rpc-one-way"
5.2.1.2 One-way messages via the One-to-none Construct
Note that this construct would need to be added to an extension or
update to 'The Blocks Extensible Exchange Protocol Core' RFC 3080.
MSG/NoANS: the client sends a "MSG" message, the server, sends no
reply.
In one-to-none exchanges, no reply to the "MSG" message is expected.
Session management and message exchange are based on the NETCONF over
SOAP transport mapping NETCONF-SOAP
Note that the use of "persistent connections" "chunked transfer-
coding" when using HTTP becomes even more important in the supporting
of event notifications
5.3.1 A NETCONF over Soap over HTTP Example
C: POST /netconf HTTP/1.1
C: Host: netconfdevice
C: Content-Type: text/xml; charset=utf-8
C: Accept: application/soap+xml, text/*
C: Cache-Control: no-cache
C: Pragma: no-cache
C: Content-Length: 465
C:
C: <?xml version="1.0" encoding="UTF-8"?>
C: <soapenv:Envelope
C: xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
C: <soapenv:Body>
C: <rpc message-id="101"
C: xmlns=
"xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
C: <create-subscription>
C: </create-subscription>
C: </rpc>
C: </soapenv:Body>
C: </soapenv:Envelope>
The response:
S: HTTP/1.1 200 OK
S: Content-Type: application/soap+xml; charset=utf-8
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S: Content-Length: 917
S:
S: <?xml version="1.0" encoding="UTF-8"?>
S: <soapenv:Envelope
S: xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
S: <soapenv:Body>
S: <rpc-reply message-id="101"
S: xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
S: <data>
S: <top xmlns=
"http://example.com/schema/1.2/notification">
S: <subscriptionId>123456</subscriptionId>
S: </top>
S: </data>
S: </rpc-reply>
S: </soapenv:Body>
S: </soapenv:Envelope>
And then some time later
S: HTTP/1.1 200 OK
S: Content-Type: application/soap+xml; charset=utf-8
S: Content-Length: 917
S:
S: <?xml version="1.0" encoding="UTF-8"?>
S: <soapenv:Envelope
S: xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
S: <soapenv:Body>
S: <rpc-one-way message-id="101"
S: xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
S: <data>
S: <notification>
S: <subscriptionID>123456</subscriptionID>
S: <eventClass><configuration/><audit/></eventClass>
S: <sequenceNumber>2</sequenceNumber>
S: <dateAndTime>2000-01-12T12:13:14Z</dateAndTime>
S: <data>
S: <user>Fred Flinstone</user>
S: <operation>
S: <edit-config>
S: <target>
S: <running/>
S: </target>
S: <config>
S: <top xmlns="http://example.com/schema/1.2/config">
S: <interface>
S: <name>Ethernet0/0</name>
S: <mtu>1500</mtu>
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S: </interface>
S: </top>
S: </config>
S: </edit-config>
S: </operation>
S: </data>
S: </notification>
S: </data>
S: </rpc-one-way>
S: </soapenv:Body>
S: </soapenv:Envelope>
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6. Filtering examples
The following section provides examples to illustrate the various
methods of filtering content on an event notification subscription.
6.1 Event Classes
The following example illustrates selecting all event notifications
for EventClasses fault, state or config
<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:event:1.0">
<create-subscription>
<eventClasses>
<fault/>
<state/>
<config/>
</eventClasses>
</create-subscription>
</rpc>
6.2 Subtree Filtering
XML subtree filtering is not well suited for creating elaborate
filter definitions given that it only supports equality comparisons
(e.g. in the 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 notification
forwarding filters as shown below.
The following example illustrates selecting fault EventClass which
have severities of critical, major, or minor. The filtering criteria
evaluation is as follows:
((fault) & ((severity=critical) | (severity=major) | (severity =
minor)))
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<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:event:1.0">
<create-subscription>
<eventClasses>
<fault/>
</eventClasses>
<netconf:filter type="subtree">
<neb xmlns="urn:ietf:params:xml:ns:netconf:event:1.0">
<event>
<severity>critical</severity>
</event>
<event>
<severity>major</severity>
</event>
<event>
<severity>minor</severity>
</event>
</neb>
</netconf:filter>
</create-subscription>
</rpc>
The following example illustrates selecting fault, state, 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)))
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<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:event:1.0">
<create-subscription>
<eventClasses>
<fault/>
<state/>
<config/>
</eventClasses>
<netconf:filter type="subtree">
<neb xmlns="urn:ietf:params:xml:ns:netconf:event:1.0">
<event>
<eventClasses>fault</eventClasses>
<severity>critical</severity>
</event>
<event>
<eventClasses>fault</eventClasses>
<severity>major</severity>
</event>
<event>
<eventClasses>fault</eventClasses>
<severity>minor</severity>
</event>
<event>
<card>Ethernet0</card>
</event>
</neb>
</netconf:filter>
</create-subscription>
</rpc>
6.3 XPATH filters
The following example illustrates selecting fault EventClass which
have severities of critical, major, or minor. The filtering criteria
evaluation is as follows:
((fault) & ((severity=critical) | (severity=major) | (severity =
minor)))
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<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:event:1.0">
<create-subscription>
<eventClasses>
<fault/>
</eventClasses>
<netconf:filter type="xpath">
(/event[eventClasses/fault] and
(/event[severity="critical"] or
/event[severity="major"] or /event[severity="minor"]))
</netconf:filter>
</create-subscription>
</rpc>
The following example illustrates selecting fault, state, 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:event:1.0">
<create-subscription>
<eventClasses>
<fault/>
<state/>
<config/>
</eventClasses>
<netconf:filter type="xpath">
((/event[eventClasses/fault] or
/event[eventClasses/state] or
/event[eventClasses/config]) and
( (/event[eventClasses/fault] and
/event[severity="critical"]) or
(/event[eventClasses/fault] and
/event[severity="major"]) or
(/event[eventClasses/fault] and
/event[severity="minor"]) or
/event[card="Ethernet0"]))
</netconf:filter>
</create-subscription>
</rpc>
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7. Security Considerations
To be determined once specific aspects of this solution are better
understood. In particular, the access control framework and the
choice of transport will have a major impact on the security of the
solution
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8. IANA Considerations
Event Classes will likely be an IANA-managed resource. The initial
set of values is defined in this specification.
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9. Acknowledgements
Thanks to Gilbert Gagnon and Greg Wilbur 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 Bakstrieve, Yoshifumi
Atarashi, Glenn Waters, Alexander Clemm, Dave Harrington, Dave
Partain, Ray Atarashi and Dave Perkins.
10. References
[NETCONF] Enns, R., "NETCONF Configuration Protocol",
ID draft-ietf-netconf-prot-06, April 2005.
[NETCONF BEEP]
Lear, E. and K. Crozier, "Using the NETCONF Protocol over
Blocks Extensible Exchange Protocol (BEEP)",
ID draft-ietf-netconf-beep-05, March 2005.
[NETCONF Datamodel]
Chisholm, S. and S. Adwankar, "Framework for NETCONF
Content", ID draft-chisholm-netconf-model-04.txt,
October 2005.
[NETCONF SOAP]
Goddard, T., "Using the Network Configuration Protocol
(NETCONF) Over the Simple Object Access Protocol (SOAP)",
ID draft-ietf-netconf-soap-05, April 2005.
[NETCONF SSH]
Wasserman, M. and T. Goddard, "Using the NETCONF
Configuration Protocol over Secure Shell (SSH)",
ID draft-ietf-netconf-ssh-04.txt, April 2005.
[URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
[XML] World Wide Web Consortium, "Extensible Markup Language
(XML) 1.0", W3C XML, February 1998,
<http://www.w3.org/TR/1998/REC-xml-19980210>.
[refs.RFC2026]
Bradner, S., "The Internet Standards Process -- Revision
3", RFC 2026, BCP 9, October 1996.
[refs.RFC2119]
Bradner, s., "Key words for RFCs to Indicate Requirements
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Levels", RFC 2119, March 1997.
[refs.RFC2223]
Postel, J. and J. Reynolds, "Instructions to RFC Authors",
RFC 2223, October 1997.
[refs.RFC3080]
Rose, M., "The Blocks Extensible Exchange Protocol Core",
RFC 3080, March 2001.
Authors' Addresses
Sharon Chisholm
Nortel
3500 Carling Ave
Nepean, Ontario K2H 8E9
Canada
Email: schishol@nortel.com
Kim Curran
Nortel
3500 Carling Ave
Nepean, Ontario K2H 8E9
Canada
Email: kicurran@nortel.com
Hector Trevino
Cisco
Suite 400
9155 E. Nichols Ave
Englewood, CO 80112
USA
Email: htrevino@cisco.com
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Appendix A. Potential Event Content
This non-normative appendix explores possible content of event
notifications. It provides field descriptions and indicates their
applicability for the various event classes. Fields specific to
configuration events (configuration event class) are provided in
Appendix B.
A.1 Event Identifier
A unique event identifier provided for event correlation purposes.
This field is used by management applications to identify events
which are generated for a single event occurrence via different
mechanisms (e.g. syslog, NETCONF). Ie, this event identifier could
be included as content in a syslog or SNMP message to indicate that
all the messages were generated from the same source event. Event Id
values may be re-used across re-boots.
Applicable event classes: All
A.2 Resource Instance
This field identifies the element/entity/object for which the event
is applicable.
Applicable event classes: All
A.3 Event Time
This field represents the time at which the action causing the
generation of the event has taken place. Event time field is
composed of two parts: event generation time and event sysUpTime.
Event generation time follows the syslog TIMESTAMP format defined in
draft-ietf-syslog-protocol-14.txt (derived from RFC3339 but with
additional restrictions). Event sysUpTime is of XML type integer
(0..4294967295) and it follows the same definition as sysUpTime
(TimeTicks) defined in RFC3418 - "The time (in hundredths of a
second) since the network management portion of the system was last
re-initialized).
Applicable event classes: All
A.4 Perceived Severity
The severity of the alarm as determined by the alarm detection point
using the information it has available [RFC3877]. The values are
cleared, indeterminate, critical, major, minor and warning.
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Applicable event classes: fault
A.5 Probable Cause
This field provides further information describing the cause of the
alarm . Allowed values for this field are the same as those listed
in RFC3877 and are derived from ITU X.733 and ITU M.3100.
Note that this concept is being evolved to be less linear, within the
ITU-T, in X.733.1, a protocol-neutral version of X.733. It may make
sense to consider alignment with this update on the concept of
probable cause, instead of the one in RFC3877 and X.733.
Applicable event classes: fault
A.6 Specific Problem
This parameter is optional. When present, it identifies further
refinements to the Probable cause of the alarm. This definition
follows ITU X.733
Applicable event classes: fault
A.7 Trend Indication
This parameter indicates the trend of the alarm against the managed
resource Allowed values for this field are as specified in RFC3877
and follow the ITU X.733 value definitions
Applicable event classes: fault
A.8 Additional Alarm Text
This parameter is provided to allow implementation to include a
textual description of the alarm
Applicable event classes: fault
A.9 Threshold Identifier
This field holds the identifier of the monitored variable for which
the threshold was set. This is analogous to the alarmVariable
OBJECT-TYPE in RFC2819.
Applicable event classes: fault (useful for threshold crossing
alarms)
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A.10 Threshold Type
This parameter is used to indicate the direction of the threshold
crossing: rising, falling, or clear.
Rising threshold type: This indicates that the value of a monitored
variable has crossed the set threshold in the upwards direction.
Only sent to indicate a problem
Falling threshold type: This indicates that the value of a monitored
variable has crossed the set threshold in the downwards direction.
Only sent to indicate a problem.
Clear threshold type: This indicates that the value of the monitored
variable for which a threshold alarm had been previously issued as a
result of crossing the set value either in the upwards or downwards
direction has been restored to a value within an acceptable range
(i.e. does not exceed the set threshold). Note that this differs
from RFC2819.
Applicable event classes: fault (useful in the case threshold
crossing alarms)
A.11 Observed Value
The value of the monitored parameter (Threshold Identifier) for the
last sampling period. This parameter follows the alarmValue
definition in RFC2819. This field is in two parts - the value and
the units of measure.
Applicable event classes: fault (useful in the case threshold
crossing alarms)
A.12 State Change Information
This parameter holds the name and values of the state attributes
whose values have changed and are being reported.
This is a parameter composed of three fields: Attribute Name, Old
Value, and New Value. The definitions given in RFC4268 for state
attributes and values are being followed.
Applicable event classes: state
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Appendix B. Configuration Event Class Notifications
This non-normative appendix provides a detailed description of a
configuration change event notification definition in support of the
configuration operations, particularly those defined by the NETCONF
protocol.
B.1 Types of Configuration Events
Configuration event notifications include:
o All-triggered Configuration Events
o NETCONF-triggered Configuration Events
All-triggered Configuration events report on changes from the
perspective of the managed resource, rather than the commands which
created the configuration change. They are reported regardless of
what specific method was used to initiate the change. They indicate
that a change has occurred around hardware, software, services or
other managed resources within a system. Specific events includes
o Resource Added
o Resource Removed
o Resource Modified
NETCONF-triggered events are those which correspond to the execution
of explicit NETCONF operations. These include:
o copy-config event
* This is a data store level event generated following the
successful completion of a copy-config operation. This
represents the creation of a new configuration file or
replacement of an existing one.
o delete-config event
* This is a data store level event generated following the
successful completion of a delete-config operation. This
represents the deletion of a configuration file.
o edit-config event
* This is an event generated following a change in configuration
due to an edit-config operation, e.g., due to the completion of
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an edit-config operation which successfully changed some part
of the configuration. See edit-config error-options (stop-on-
error, ignore-error, rollback-on-error) The contents of this
event are dependent on the type of operation performed: edit-
config (merge, replace, delete, create). This event is not
intended to report completely unsuccessful configuration
operations.
o lock-config event
* This is a data store level event generated following the
successful locking of a configuration data store.
o unlock-config event
* This is a data store level event generated following the
successful release of a lock previously held on a configuration
data store.
B.2 Config Event Notification Structure
The table below lists the EventInfo parameters for a config event
notification.
Nomenclature:
O - This is marked optional field because it is implementation/
notification category dependent. In some cases this may be user
configurable.
M - This is a mandatory field that must be included. Dependency on
event class may exist as noted below
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-----------------------------------------------------
Parameter Name Restrictions
-----------------------------------------------------
EventInfo
-----------------------------------------------------
EventID O
-----------------------------------------------------
ResourceInstance M
-----------------------------------------------------
ConfigChangeType M
-----------------------------------------------------
TargetDataStore M
-----------------------------------------------------
UserInfo O
-----------------------------------------------------
UserName
-----------------------------------------------------
SourceIndicator
-----------------------------------------------------
TransactionId
-----------------------------------------------------
CopyConfigInfo -- copy-config only
-----------------------------------------------------
DataSource M
-----------------------------------------------------
EditConfigInfo -- edit-config only
-----------------------------------------------------
EventTime M
-----------------------------------------------------
Context O
-----------------------------------------------------
EnteredCommand M
-----------------------------------------------------
NewConfig M
-----------------------------------------------------
MergeReplaceInfo
-----------------------------------------------------
OldConfig O
-----------------------------------------------------
EventTime M
-----------------------------------------------------
EventGenerationTime
-----------------------------------------------------
EventSysUpTime
-----------------------------------------------------
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B.3 Configuration Event Content
The applicability of these fields to other event classes is for
further study.
B.3.1 Target Datastore
Target datastore refers to the data store (startup, candidate,
running) which was modified by the management operation.
This is used to convey information describing who originated the
configuration event and the means for submitting the request. The
user info field contains the following information:
user Name: User id which was authorized to execute the associated
management operation causing the generation of this event.
source Indicator: Indicates the method employed to initiate the
management operation telnet, NETCONF, console, etc.
transaction Id: If available, this field contains a unique
identifier for the associated management operation. This is
implementation dependent and may require additional information to
be communicated between server and client. A possible option is
to make use of the message-id in the NETCONF rpc header
B.3.3 Data Source
The data source is used, for example, in the copy configuration
command to indicated the source of information used in the copy
operation
Applicable Event Classes: configuration (useful for copy-config)
Operation is used, for example, in the edit configuration command to
indicated the specific operation that has taken place - create,
delete, merge, replace.
Applicable Event Classes: configuration (useful for edit-config)
The configuration sub-mode under which the command was executed.
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Applicable Event Classes: configuration
B.3.6 Entered Command
The command entered and executed on the device.
B.3.7 New Config
The device's configuration following the successful execution of the
entered command.
Applicable Event Classes: configuration
B.3.8 Old Config
The configuration prior to the execution of the entered command.
Applicable Event Classes: configuration
B.3.9 Non-netconf commands in configuration notifications
To support legacy implementations and for better integration with
other deployed solutions on the box, sending information via netconf
about configuration changes that were originated via other solutions,
such as command line interfaces is necessary. In order to do this,
the information in the message needs to be clearly tagged so that the
consumer of the information knows what to expect. In addition, the
creation of the subscription needs allow for the client to indicate
whether this non-XML formatted information is of interest
The latter is done by identifying the XML namespace under which the
data syntax/schema is defined. A NETCONF client requests the format
in which it wants the NETCONF server to issue the event notifications
at subscription time by specifying the appropriate namespace under
the Filter parameter in the <create-subscription> operation. An
example is provided below:
<netconf:filter>
<data-format:config-format-xml
xmlns="http://www.example.com/xmlnetevents"/>
</netconf:filter>
B.4 Design Alternative
B.4.1 Server Session Initiation
Currently the NETCONF protocol requires session establishment to be
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initiated by the NETCONF client. With the introduction of event
notifications in NETCONF as well deployments which might require the
"call-home" feature to get around firewall and/or NAT issues, the
ability for a NETCONF server to initiate sessions becomes important.
Other potential uses of this feature includes the following
deployment scenario: NE registration/auto-configuration. The device
is pre-configured with a target destination address (the management
station's address) where it needs to register and download its
configuration. When managing large numbers of devices (e.g. CPEs)
this also allows for increased scalability since the management
station does not need to maintain established sessions to all managed
devices.
This appendix proposes extensions to the event subscription session
establishment procedures and related operations to allow for server
session initiation.
Note that the security implications of this approach, compared with
more traditional, well understood models, is for further study.
The subscription information as described in the body of this
document indicates that it is transient in nature (i.e. it is not
persisted and it is only applicable through the life of the session).
This section describes additional functionality for persisting event
subscription information and allowing the NETCONF server (e.g.
network element) to initiate the event subscription session.
QUICK SUMMARY: The <create-subscription>, <cancel-subscription>,
<modify-subscription> operations would be used in same manner as
described in doc. It may use useful to allow a client and server to
re-establish an events subscription. This would result in another
capability to allow session initiation by the server.
B.4.2 Establishment
In order to establish an event subscription, a client must issue a
<create-subscription> message request. Upon a successful response
from the server (e.g. network element) the event subscription is
established. With this modified persistent version of the
subscription, the NETCONF server would maintain the subscription
information as part of its configuration.
A event subscription is torn down when a) the client issues a
<cancel-subscription> message and it is successfully processed by
the server (i.e. the server issues a positive response) or b) the
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NETCONF session carrying the event subscription goes down for any
reason.
If the subscription is not persistent, the user must create a new
subscription with the exact same parameters as the original session.
If instead, subscriptions were persistent, as part of the network
element's configuration, the client simply needs to re-establish the
session by specifying the subscription Id.
B.4.4 Suspend And Resume
Since the purpose of the <cancel-subscription> operation is to stop
event notification forwarding and due to its transient nature removes
all subscription configuration; a different mechanism might be needed
for shutting down the session but preserving the subscription
information thus allowing the NETCONF server to re-establish the
parameters and reproduce the subscription.
The suspend and resume commands would allows a NETCONF client to
suspend event notification forwarding without removing the existing
subscription information. Operations <suspend-subscription> and
><resume-subscription> are proposed for this purpose.
Since event subscription information is now persistent, unsolicited
session termination (i.e. other than <cancel-subscription)) is
treated as if a <suspend-subscription> command was issued. Event
forwarding is resumed by sending a <resume-subscription> to the
NETCONF server on a new connection.
Configuration information associated with the event subscription
(event classes and filters) could persist beyond the life of the
event subscription session. (i.e. it is maintained by the network
element as part of its configuration). This configuration
information is subject to the behaviour of the datastore it resides
in and may or may not persist across re-boots (e.g. it could be part
of the running configuration but not the startup configuration).
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Appendix C. NETCONF Event Notifications and Syslog
This appendix describes the mapping between syslog message fields and
NETCONF event notification fields. The purpose of this mapping is to
provide an unambiguous mapping to enable consistent multi-protocol
implementations as well as to enable future migration.
The second part of the appendix describes an optional capability to
embed an entire syslog message (hereafter referred to as syslog
message(s) to avoid confusion with the message field in syslog)
within a NETCONF event notification.
C.1 Leveraging Syslog Field Definitions
This section provides a semantic mapping between NETCONF event fields
and syslog message fields.
-------------------------------------------------------------------
| PRI | HEADER | MESSAGE |
-------------------------------------------------------------------
| FACILITY | SEVERITY | TIMESTAMP | HOSTNAME | TAG CONTENT |
-------------------------------------------------------------------
Figure 2 - syslog message (RFC3164)
-------------------------------------------------------------------
| HEADER | STRUCTURED DATA | MESSAGE |
-------------------------------------------------------------------
Figure 3 - syslog message (draft-ietf-syslog-protocol-14.txt)
HEADER (Version, Facility, Severity, Truncate, Flag, TimeStamp,
HostName, AppName, ProcId, MsgId)
STRUCTURED DATA (Zero or more Structured Data Elements - SDEs)
MESSAGE ( Text message )
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C.1.1 Field Mapping
------------------------------------------------------
RFC3164 Syslog ID NETCONF Event
------------------------------------------------------
VERSION
------------------------------------------------------
FACILITY FACILITY
------------------------------------------------------
SEVERITY SEVERITY PerceivedSeverity
------------------------------------------------------
TRUNCATE FLAG
------------------------------------------------------
TIMESTAMP TIMESTAMP EventTime
------------------------------------------------------
HOSTNAME HOSTNAME EventOrigin
------------------------------------------------------
TAG APP-NAME EventOrigin
------------------------------------------------------
PROC-ID
------------------------------------------------------
MSG-ID
------------------------------------------------------
CONTENT CONTENT AdditionalText
------------------------------------------------------
Figure 4 - syslog to NETCONF Event field mapping
Notes:
VERSION: Schema version is found in XML Schema namespace. However,
no correspondence to syslog.
FACILITY: No well defined semantics for this field. Therefore not
used at this time.
TRUNCATE: Not applicable. NETCONF events must be complete XML
documents therefore cannot be truncated.
TIME: TIMESTAMP in syslog ID is derived from RFC3339 but with
additional restrictions
PROC-ID: No equivalent field
CONTENT: This is a free form text field with not defined semantics.
The contents of this field may be included in the AdditionalText
field.
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C.1.2 Severity Mapping
The severity value mappings stated in (draft-ietf-syslog-protocol-14)
are used:
ITU Perceived Severity syslog SEVERITY
Critical Alert
Major Critical
Minor Error
Warning Warning
Indeterminate Notice
Cleared Notice
Figure 5. ITU PerceivedSeverity to syslog SEVERITY mapping.
C.2 Syslog within NETCONF Events
C.2.1 Motivation
The syslog protocol (RFC3164) is widely used by equipment vendors as
a means to deliver event messages. Due to the widespread use of
syslog as well as a potential phased availability and coverage of
NETCONF events by equipment vendors, it is envisioned that users will
also follow a phased migration. As a way to facilitate migration and
at the same time allow equipment vendors to provide comprehensive
event coverage over a NETCONF event subscription session, syslog
messages could be embedded in their entirety within the body of a
NETCONF event notification.
The information provided in this appendix describes a mechanism to
leverage syslog messages for the purpose of complementing the
available NETCONF event notification set. The intent is to promote
the use of the NETCONF interface and not to simply provide a wrapper
and additional delivery mechanism for syslog messages. NETCONF
events are intended to be well defined and structured, therefore
providing an advantage over the unstructured and often times
arbitrarily defined syslog messages (i.e. the message field).
Covered herein is the syslog protocol as defined in RFC3164 and
draft-ietf-syslog-protocol-14.txt.
C.2.2 Embedding syslog messages in a NETCONF Event
When event notifications are supported, the default behaviour for a
NETCONF server is to send NETCONF event notifications over an
established event subscription. As an option, the NETCONF server may
embed a syslog message in its entirety (e.g. RFC3164 - PRI, Header,
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and Message fields), placing it within the Event Info field
(SyslogInfo sub-field) - see Figure 1.
_____________________________________________________
| NETCONF Event Header | Data |
|________________________|___________________________|
| | Event Info |
|________________________|___________________________|
| |
v v
____________________________
| Event Fields | SyslogInfo |
|___________________________|
Figure 1 - Embedding syslog in a NETCONF Event Notifications
C.2.3 Supported Forwarding Options
Three event forwarding options may be supported by the NETCONF
server: a) XML only (mandatory if NETCONF events capability is
supported) b) XML and syslog (Optional) c) syslog only (optional)
Note to the reader: Option "a" above refers to event notification
messages defined for use over the NETCONF protocol. While their use
is not necessarily limited to NETCONF protocol, they are referred to
as "NETCONF XML-event" in the remainder of this section simply to
avoid ambiguity.
C.2.3.1 XML and Syslog option - Forwarding Behaviour
It is possible, due to coverage, for a given NETCONF implementation
to not support a comprehensive set of NETCONF event notifications.
Therefore, it is possible for a given event to trigger the generation
of a syslog message without a NETCONF-aware counterpart. In such
situations, the NETCONF server could form a NETCONF event
notification, embed the syslog message in the SyslogInfo field and
forward the NETCONF event notifications to all subscribed
destinations. Otherwise, both NETCONF event and syslog messages must
be included in the Event Info field.
C.2.3.2 Event Class Identification
The event class field is found in the NETCONF event header
information as described in the main body of this document. It
conveys information describing that type of event for which the event
notification is generated and lets the consumer of the message know
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what to expect. NETCONF event notifications which only contain a
syslog message (Options b or c) must have the EventClass field set to
"information". [Editor's Note: This needs to be thought through. It
may not be the best option.] The NETCONF client parses the message
in the same manner as any other message, finds the normal fields
empty [Editor's Note: or not present?] and either proceeds to parse
the SyslogInfo field or hands the syslog message to the entity
responsible for processing syslog messages.
C.2.3.3 Event Subscription Options
A NETCONF client may request subscription to options b) XML and
syslog or c) syslog only listed in "Supported Forwarding Options" at
subscription time via the user-specified filter. The FILTER or NAMED
FILTER parameter in <create-subscription>. As previously indicated,
the default behaviour is to forward NETCONF XML only event
notifications.
C.2.3.4 Supported Forwarding Option Discovery
A potential means for a NETCONF server to convey its feature set
support is via capabilities. However, in this particular case, the
event content is not a protocol feature therefore other means are
needed. A future version of this document will address this issue.
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Acknowledgment
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