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Differences from draft-khartabil-simple-filter-funct-00.txt
SIMPLE H. Khartabil
Internet-Draft M. Lonnfors
Expires: April 23, 2004 J. Costa-Requena
E. Leppanen
Nokia
October 24, 2003
Functional Description of Event Notification Filtering
draft-khartabil-simple-filter-funct-01
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
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The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 23, 2004.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The SIP event notification framework describes the usage of the
Session Initiation Protocol (SIP) for subscriptions and notifications
of changes to a state of a resource. The document does not describe a
mechanism of how filtering of event notification information can be
achieved.
This document describes the operations a subscriber performs in order
to define filtering rules, how to handle responses to subscriptions
carrying filtering rules, and how to handle notifications with
filtering rules applied to them. The document also describes how the
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notifier behaves when receiving such filtering rules and how a
notification is constructed.
The format of the filter is outside the scope of this document.
Table of Contents
1. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Client Operation . . . . . . . . . . . . . . . . . . . . . . 4
3.1 Transport Mechanism . . . . . . . . . . . . . . . . . . . . 4
3.2 SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . . 4
3.3 Subscriber Generating SUBSCRIBE Requests . . . . . . . . . . 4
3.3.1 Structure of Filter Criteria . . . . . . . . . . . . . . . . 4
3.3.2 Request-URI vs. Filter Criteria URI . . . . . . . . . . . . 5
3.3.3 Changing Filter Criteria within a Dialog . . . . . . . . . . 5
3.3.4 Subscriber Interpreting SIP responses . . . . . . . . . . . 5
3.4 Subscriber Processing of NOTIFY Requests . . . . . . . . . . 6
4. Resource List Server Behaviour . . . . . . . . . . . . . . . 6
4.1 Request-URI vs. Filter Criteria URI . . . . . . . . . . . . 6
5. Server Operation . . . . . . . . . . . . . . . . . . . . . . 7
5.1 NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . . 7
5.2 Notifier Processing SUBSCRIBE Requests . . . . . . . . . . . 7
5.2.1 Request-URI vs. Filter Criteria URI . . . . . . . . . . . . 7
5.3 Notifier Generating NOTIFY Requests . . . . . . . . . . . . 8
5.3.1 Generation of NOTIFY Contents . . . . . . . . . . . . . . . 8
5.3.2 Handling of Notification Triggering Rules . . . . . . . . . 9
5.4 Handling Abnormal Cases . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 10
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1 Presence Specific Examples . . . . . . . . . . . . . . . . . 10
7.1.1 Subscriber Requests Messaging Related Information . . . . . 11
7.1.2 Subscriber Fetches Information about "Open"
Communication Means . . . . . . . . . . . . . . . . . . . . 12
7.1.3 Subscriber Requests Notifications when Presentity's
Status Changes . . . . . . . . . . . . . . . . . . . . . . . 14
7.2 Watcher Information Specific Examples . . . . . . . . . . . 16
7.2.1 Watcher Subscriber Makes Subscription to Gets All the
Information about Active Watchers . . . . . . . . . . . . . 17
7.2.2 Watcher Subscriber Requests Information of Watchers with
Specific Subscription Duration Conditions . . . . . . . . . 18
7.2.3 Watcher Subscriber Requests Specific Watcher Info On
Specific Triggers . . . . . . . . . . . . . . . . . . . . . 20
8. Security Considerations . . . . . . . . . . . . . . . . . . 22
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
References . . . . . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 24
Intellectual Property and Copyright Statements . . . . . . . 25
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1. Conventions
In this document, the key words 'MUST', 'MUST NOT', 'REQUIRED',
'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
and 'OPTIONAL' are to be interpreted as described in RFC 2119 [1]
and indicate requirement levels for compliant implementations.
2. Introduction
SIP event notification is described in [5]. It defines a general
framework for sending subscriptions and receiving notifications in
SIP based systems. It introduces the concept of event packages, which
are concrete applications of the general event framework to a
specific usage of events.
Filtering is a mechanism for controlling the content of event
notifications. Additionally, the subscriber may specify the rules for
when a notification should be sent to it. Requirements for such
mechanisms are defined in [10] and [11].
The filtering mechanism is expected to be particularly valuable to
users of mobile wireless access devices. The characteristics of the
devices typically include high latency, low bandwidth, low data
processing capabilities, small display, and limited battery power.
Such devices can benefit from the ability to filter the amount of
information generated at the source of the event notification.
It is stated in [5] that the notifier may send a NOTIFY at any time,
but typically it is sent when the state of the resource changes. It
also states that the notifications would contain the complete and
current state of the resource authorized for a certain subscriber to
see. The format of such resource state information is package
specific. In this memo, we assume that the NOTIFY for any package
contains an XML document.
There is a separate approach for the rate limiting of SIP event
notifications, namely the throttling mechanism [12]. This throttling
mechanism allows the subscriber to specify a maximum rate at which
event notifications are generated by a single notifier. The solution
for such requirements is out of scope for this document.
This document presents a mechanism for filtering whereby a subscriber
describes its preference of when notifications are to be sent to it
and what they are to contain. It also describes how the notifier
functions when generating notifications by taking into account
filters and default functionality of the package/service.
The XML format for defining the filter criteria is described in [9].
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3. Client Operation
3.1 Transport Mechanism
Transportation of the filter criteria to the server is achieved by
inserting the XML document, as defined in [9], in the body of the
SUBSCRIBE request. Alternatively, the XML document can be uploaded to
the server using means outside the scope of this document.
3.2 SUBSCRIBE Bodies
SIP entities compliant with this specification MUST support the
content type 'application/simple-filter+xml'.
3.3 Subscriber Generating SUBSCRIBE Requests
This section presents additional functionality required from the
subscriber when filters are used in the bodies of the SUBSCRIBE
requests. Normal operations of services, e.g., as defined in [4], [8]
and [6] are otherwise followed.
As defined in [5], the SUBSCRIBE message MAY contain a body. This
body would serve the purpose of carrying filtering information.
Honouring those filters is at the discretion of the notifier and
might depend on local policies.
No content in the body of a SUBSCRIBE indicates to the notifier that
no filter is being requested so that the notifier is instructed to
send all the NOTIFY requests using the notifier's own or service
specific policy. Note that e.g. in the list case [6] the filter
criteria might have been uploaded to the server beforehand (by means
outside the scope of this document).
If the body of the SUBSCRIBE includes the filter criteria, the body
MUST be of the MIME-Type 'application/simple-filter+xml'.
3.3.1 Structure of Filter Criteria
Multiple filter criteria MAY be included in one SUBSCRIBE. This is
achieved by including multiple <filter> elements in the filter
criteria [9]. Each <filter> element may include a URI attribute.
A SUBSCRIBE request destined to a list URI [6] MAY include multiple
criteria specific to individual resources. This is achieved by
including multiple <filter> elements with different URIs of resources
in each of those elements. This resource specific filter criteria
overrides any list specific filter criteria, if any. The list
specific filter criteria may or may not include a URI.
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3.3.2 Request-URI vs. Filter Criteria URI
The URI in the filter criteria defines the target resource, e.g. in
the Presence service case; it is the presentity's presence
information to which the filter criteria is applied. The subscriber
MAY choose to leave the URI in the filter criteria undefined. If the
URI is not defined within the filter criteria, the filter criteria
apply to the resource identified in the Request-URI. Similarly, the
subscriber MAY define a filter criteria URI. If the Request-URI is a
list URI [6], the filter criteria URI MUST be the list URI, a
sub-list URI or resource who's URI is one of the URIs that result
from a lookup, by an RLS, on the Request-URI. If not, the filter
criteria may be ignored or may be rejected.
3.3.3 Changing Filter Criteria within a Dialog
The client MAY reset or change the filter criteria by re-issuing a
new SUBSCRIBE request within the existing dialog. A SUBSCRIBE within
the exiting dialog that does not contain a filter criteria is assumed
to prolong existing filter criteria. This means that filter criteria
are persistent and are only explicitly removed.
A client requiring removal of a filter criteria may do so by using
the 'removed="true"' attribute as defined in [9].
In the case the URI in the filter criteria is that of a list, a
client may override the existing filter criteria with a filter
criteria for an individual resource, that is part of the list
subscribed to earlier, by issuing a new SUBSCRIBE within the existing
dialog and including a filter criteria specific for that individual
resource. The new filter criteria need not include the original
filter criteria since a filter is only removed in the manner
indicated above.
3.3.4 Subscriber Interpreting SIP responses
The SUBSCRIBE request will be confirmed with a final response. A
200-class responses indicate that the subscription has been accepted,
and that a NOTIFY will be sent immediately. A "200" response
indicates that the subscription has been accepted and the filter
criteria is accepted. A "202" response merely indicates that the
subscription has been understood, the content type has been accepted,
and that authorization may or may not have been granted. A "202"
response also indicates that the filter has not been accepted yet.
The acceptance of the filter criteria MAY arrive in a subsequent
NOTIFY.
A non-200 class final responses indicate that no subscription or
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dialog has been created, and no subsequent NOTIFY message will be
sent. All non-200 class final responses have the same meanings and
handling as described in [3] and [5].
Specifically, a "415" response indicates that the MIME type
'application/simple-filter+xml' is not understood by the notifier. A
"488" response indicates that the content type (filter) is understood
but some aspects of it were either not understood or not accepted.
3.4 Subscriber Processing of NOTIFY Requests
If the 2xx response was returned for the SUBSCRIBE, the NOTIFY that
follows MAY contain a body that describes the present state of the
resource after the filter criteria have been applied.
If the NOTIFY indicates that a subscription has been terminated [5],
the subscription is assumed to be terminated. Behaviour in such
events is also described in [5].
If the subscription is indicated as active, NOTIFY requests are
handled as described in package specific documents and [5].
4. Resource List Server Behaviour
The Resource List Server is defined in [6]. This section describes
how such entity behaves in the presence of a filter criteria in a
subscription to a list.
4.1 Request-URI vs. Filter Criteria URI
If the URI is not defined within the filter criteria, the filter
criteria apply to the resource identified in the Request-URI.
If no URI is indicated by the filter criteria, the filter criteria
apply to all the notifications that the RLS issues. If the URI
indicated by the filter criteria is a list URI, the filter criteria
apply to all the notifications that the RLS issues.
If the URI indicated by the filter criteria is for one resource who's
URI is one of the URIs that result from a lookup, by the RLS, on the
Request-URI, the filter criteria for that particular resource are
extracted and propagated in the SUBSCRIBE request sent to that
resource. (It is possible to have more than one filter criteria in a
SUBSCRIBE body, and therefore a filter criteria specific to a
resource must be extracted and only that is propagated. For example,
if the Request-URI in a SUBSCRIBE has the value
"sip:mybuddies@mydomain.com" where "bob@otherdomain.com" is a
resource belonging to that list, and the URI in a filter criteria is
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"sip:bob@otherdomain.com", the filter criteria specific for Bob are
extracted and placed in the body of the SUBSCRIBE sent to
"bob@otherdomain.com").
If the URI indicated by the filter criteria is for one resource who's
URI is NOT one of the URIs that result from a lookup, by the RLS, on
the Request-URI, the filter criteria are propagated to all the fanned
out subscriptions. This is to accommodate the scenario where the
subscriber knows that there are sub-lists in the list that the
original subscription was sent to, and the subscriber wishes to set a
filter criteria for a resource in that sub-list.
5. Server Operation
5.1 NOTIFY Bodies
SIP entities compliant with this specification MUST support
content-type 'application/simple-filter+xml'.
5.2 Notifier Processing SUBSCRIBE Requests
This section presents addition functionality required from the
notifier when filters are used in the bodies of the SUBSCRIBE
requests. Normal package specific functionality are otherwise
followed.
The notifier will examine the content type header and will return a
415 response if it does not understand the content type 'application/
simple-filter+xml'.
A 200-class responses indicate that the subscription has been
accepted, and the NOTIFY will be sent immediately. A "200" response
indicates that the subscription has been accepted, the user is
authorized and the filter is accepted. A "202" response merely
indicates that the subscription has been understood, but the
authorization may or may not have been granted. A "202" response also
indicates that the filter criteria have not been accepted yet. The
acceptance of the filter criteria MAY arrive in a subsequent NOTIFY.
Procedures described in section Section 5.4 are followed if an error
is encountered.
5.2.1 Request-URI vs. Filter Criteria URI
The subscriber may have chosen to leave the URI in the filter
criteria undefined. If the URI is not defined within the filter
criteria, the filter criteria apply to the resource identified in the
Request-URI.
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Similarly, the subscriber may have chosen to include a URI in the
filter criteria. In this case, the filter criteria apply to all
notifications send for this subscription. If the Request-URI and the
URI in the filter criteria mismatch, the filter criteria may be
ignored or may be rejected.
5.3 Notifier Generating NOTIFY Requests
Upon receiving the SUBSCRIBE with the filter criteria, the notifier
SHOULD retain the filter criteria as long as the subscription
persists. The filter MAY be incorporated within an existing
subscription (in an active dialog) by sending a re-SUBSCRIBE that
includes the filter criteria in the body.
If the response sent to the SUBSCRIBE was the 202 and the 202 was
chosen because the filter could not be accepted that time, the NOTIFY
MAY be used to terminate the subscription if the filter was found
unacceptable.
As described in [5], the NOTIFY message MAY contain a body that
describes the state of the resource. This body is in one of the
formats listed in the Accept header of the SUBSCRIBE, or the package
specific default if the Accept header is omitted.
5.3.1 Generation of NOTIFY Contents
If the NOTIFY being sent is the immediate one sent after a 2xx
response to the original SUBSCRIBE, its contents MUST be populated
according to the filter criteria. If applying the filter criteria
results in not sending a NOTIFY, the NOTIFY must be sent with empty
contents. A notifier may also choose not to obey the filter criteria
in the first NOTIFY and instead send the configured value authorised
for that subscriber set by the notifier using means outside the scope
of this document).
The input to the content filter is a package specific XML document,
e.g. [2] and [7] derived according to the package specific
specifications, ([4] and [8]).
The content is filtered according to the expressions in the <what>
element of the filter criteria. The expression indicates the
delivered XML elements and/or attributes. Prefixes of the namespaces
of the items of the XML document to be filtered must be expanded
before applying the filter to the items.
The expression directly states the XML elements and attributes to be
delivered in the NOTIFY, along with their values. In addition to the
selected contents also the namespaces of all the selected items are
included in the NOTIFY. The XML elements and/or attributes indicated
by the expression in the <what> element must be items that the
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subscriber is authorised to see. If not, the notifier policy dictates
the behaviour of the notifier (notifier can either ignore the filter,
parts of the filter, or reject the filter completely). Implementers
need to carefully consider such an implementation decision; the
subscriber may not be aware of the authorised contents and therefore
most likely will include in the filter a criteria requesting
unauthorised contents. It is therefore RECOMMENDED that notifiers
just ignores the parts of the filter criteria where it is requesting
unauthorised info. I.e. The filter criteria in the <filter> element
where the unauthorised contents are requested is ignored. If polite
blocking is used by the notifier, the notifier may choose to ignore
the filter, by choosing to deliver notifications containing bogus
information in the unauthorised elements or attributes.
The resultant XML document MUST be well formed and valid according to
the XML schema. This means that all mandatory elements and attributes
along with their values MUST be included in the XML document
regardless of the expression. In other words, if the results of
applying a filter criteria on an XML document results in a non-valid
XML document, the notifier MUST add elements and attributes, along
with their values, from the original XML document into the newly
formulated one in order for it to be a valid one. Thissituation can
occur if the notfier did not closely examine the filter before
accepting it
5.3.2 Handling of Notification Triggering Rules
There can be several <trigger> elements inside one <filter> element.
If the criteria for any of the <trigger> elements are satisfied, a
NOTIFY SHOULD be generated.
The items (XML elements and/or attributes) indicated by the
expression in the <changed> element, <added> element or <removed>
element must be items that the subscriber is authorised to access. If
not, the notifier policy dictates the behaviour of the notifier
(notifier can either ignore the filter, parts of the filter, or
reject the filter completely).
5.4 Handling Abnormal Cases
In case of an invalid filter criteria definition the XML document of
the filter criteria is not aligned with the XML schema of the filter
criteria [9]. The notifier rejects the SUBSCRIBE request with a
"488" response. A warning header in the response may give better
indication why the filters were not accepted. If the subscription was
accepted with a "202" response but the invalid filter criteria was
discovered after that, a NOTIFY with a subscription-state of value
'terminated' is sent. An event-reason-value "badfilter", introduced
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here, of subexp-params [5] MAY be included.
In case of an erroneous expression in the filter definition the
notifier either ignores the filter definition or terminates the
subscription.
If a <what> or <trigger> element is empty, the notifier proceeds as
if the element did not exist.
6. IANA Considerations
A new event-reason-value "badfilter" is defined to represent the
event where the filter criteria is not well formed and/or not
accepted.
OPEN ISSUE: IANA registration template must be added later. [13]
7. Examples
The following chapters include filtering examples for Presence and
Watcher Information. The format of filter criteria is according to
[9].
7.1 Presence Specific Examples
This chapter describes three use cases where the presence information
filtering solution is utilised [4]. In the first use case the watcher
is interested in getting messaging specific information of a certain
presentity. In the second use case the watcher is interested in
getting information about the communication means and contact
addresses the presentity is currently available for communication on.
The third case shows how a presentity can request triggers to receive
notifications
Below is the Presentity's presence information in PIDF [2]. It
includes two tuples: one for the instant messaging and another for
the voice related information.
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<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
xmlns:rpids="urn:example-comietf:params:ns:sip-rpids"
entity="sip:presentity@domain.com">
<tuple id="432sd">
<status>
<basic>closed</basic>
</status>
<rpid:class>im</rpid:class>
<contact>im:presentity@domain.com</contact>
</tuple>
<tuple id="thr76jk">
<status>
<basic>open</basic>
</status>
<rpid:class>voice</rpid:class>
<contact>tel:2224055555@domain.com</contact>
</tuple>
</presence>
7.1.1 Subscriber Requests Messaging Related Information
The subscriber initiates a subscription to the presentity's messaging
(MMS, IM and SMS) related presence information. The subscription
includes the content limiting filter.
The filtered content is indicated with an expression. This expression
selects all the upper, lower and parallel level PIDF XML elements
that match the criteria (this means the tuple and its root element).
That criteria are: <label> elements that have values beginning with
"MMS", "SMS" or "IM".
In this case, the notification includes the contents of the tuple
that has the value "IM" in its <label> element.
SUBSCRIBE request from the subscriber including filter:
SUBSCRIBE sip:presentity@domain.com
Via: SIP/2.0/TCP 10.0.0.1:5060;branch=xjfdsjfk
To: <sip:presentity@domain.com>
From: <sip:watcher@domain.com>;tag:12341111
Call-ID: 121212@10.0.0.1
Cseq: 1 SUBSCRIBE
Expires: 3600
Event: Presence
Contact: <sip:watcher@client.domain.com>
Content-Type: application/simple-filter+xml
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Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<filter id="mess" uri="sip:presentity@domain.com">
<what>
<condition base-element="//tuple" type="xml-element">rpid:class="IM" or rpid:class="SMS" or rpid:class="MMS"</condition>
<include level="self" type="xml-element">//tuple</include>
<include level="descendant">//tuple</include>
<include level="ancestor">//tuple</include>
</what>
</filter>
</filter-set>
Notification to the subscriber:
NOTIFY sip:watcher@client.domain.com SIP/2.0
Via: SIP/2.0/TCP presence.domain.com:5060;branch=xjfder
To: <sip:watcher@domain.com>;tag:12341111
From: <sip:presentity@domain.com>;tag:232321
Call-ID: 121212@10.0.0.1
Cseq: 1 NOTIFY
Event: Presence
Subscription-State: active; expires=3599
Contact: sip:presentity@server.domain.com
Content-Type: application/cpim-pidf+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
xmlns:rpids="urn:example-com:ietf:params:ns:sip-rpids"
entity="sip:presentity@domain.com">
<tuple id="432sd">
<status>
<basic>closed</basic>
</status>
<rpid:class>im</rpid:class>
<contact>im:presentity@domain.com</contact>
</tuple>
</presence>
7.1.2 Subscriber Fetches Information about "Open" Communication Means
The subscriber makes a subscription to the presentity's available
communication means. The subscription includes the content limiting
filter.
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The filtered content is indicated with an expression. This expression
selects all the upper, lower and parallel level PIDF XML elements
that match the criteria. That criteria are: the <basic> element's
value is "Open". There is also need to indicate that only the tuples
which have contact address information are selected.
In this case the notification returns the contents of the tuple that
has both the value "open" inside the <status> element and the
existing <contact> elements.
SUBSCRIBE request from the subscriber including filter:
SUBSCRIBE sip:presentity@domain.com SIP/2.0
Via: SIP/2.0/TCP 10.0.0.1:5060;branch=xjfdsjfk
To: <sip:presentity@domain.com>
From: <sip:watcher@domain.com>;tag:12341111
Call-ID: 121212@10.0.0.1
Cseq: 1 SUBSCRIBE
Expires: 3600
Event: Presence
Contact: <sip:watcher@client.domain.com>
Content-Type: application/simple-filter+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<filter id="open-mean" uri="sip:presentity@domain.com">
<what>
<condition base-element="//tuple" type="xml-element">basic="open"</condition>
<include level="self" type="xml-element">//tuple</include>
<include level="descendant">//tuple</include>
<include level="ancestor">//tuple</include>
</what>
</filter>
</filter-set>
Notification to the subscriber:
NOTIFY sip:watcher@client.domain.com SIP/2.0
Via: SIP/2.0/TCP presence.domain.com:5060;branch=xjfder
To: <sip:watcher@domain.com>;tag:12341111
From: <sip:presentity@domain.com>;tag:232321
Call-ID: 121212@10.0.0.1
Cseq: 1 NOTIFY
Event: Presence
Subscription-State: active; expires=3599
Contact: sip:presentity@server.domain.com
Content-Type: application/cpim-pidf+xml
Content-Length: ...
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<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
xmlns:rpids="urn:example-com:ietf:params:ns:sip-rpids"
entity="sip:presentity@domain.com">
<tuple id="thr76jk">
<status>
<basic>open</basic>
</status>
<rpid:class>voice</rpid:class>
<contact>tel:2224055555@domain.com</contact>
</tuple>
</presence>
7.1.3 Subscriber Requests Notifications when Presentity's Status Changes
The subscriber subscribes to the presentity, specifying in the filter
that it wants notifications only when the <basic>element has changed
to value 'open'
SUBSCRIBE request from the subscriber including filter:
SUBSCRIBE sip:presentity@domain.com
Via: SIP/2.0/TCP 10.0.0.1:5060;branch=xjfdsjfk
To: <sip:presentity@domain.com>
From: <sip:watcher@domain.com>;tag:12341111
Call-ID: 121212@10.0.0.1
Cseq: 1 SUBSCRIBE
Expires: 3600
Event: Presence
Contact: <sip:watcher@client.domain.com>
Content-Type: application/simple-filter+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<filter id = "open-mean" uri="sip:presentity@domain.com">
<trigger>
<changed changed-from="closed" changed-to="open">//presence/tuple/status/basic</changed>
</trigger>
</filter>
</filter-set>
Assuming a 2nd PIDF document is created with both tuples having status of closed:
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
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xmlns:rpids="urn:example-com:ietf:params:ns:sip-rpids"
entity="sip:presentity@domain.com">
<tuple id="432sd">
<status>
<basic>closed</basic>
</status>
<rpid:class>im</rpid:class>
<contact>im:presentity@domain.com</contact>
</tuple>
<tuple id="thr76jk">
<status>
<basic>closed</basic>
</status>
<rpid:class>voice</rpid:class>
<contact>tel:2224055555@domain.com</contact>
</tuple>
</presence>
A NOTIFY is not sent to the subscriber in this case.
Now, a 3rd PIDF document is created when IM status changes to OPEN:
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
xmlns:rpids="urn:example-com:ietf:params:ns:sip-rpids"
entity="sip:presentity@domain.com">
<tuple id="432sd">
<status>
<basic>open</basic>
</status>
<rpid:class>im</rpid:class>
<contact>im:presentity@domain.com</contact>
</tuple>
<tuple id="thr76jk">
<status>
<basic>closed</basic>
</status>
<rpid:class>voice</rpid:class>
<contact>tel:2224055555@domain.com</contact>
</tuple>
</presence>
Notification to the subscriber is sent in this case:
NOTIFY sip:watcher@client.domain.com SIP/2.0
Via: SIP/2.0/TCP presence.domain.com:5060;branch=xjfder
To: <sip:watcher@domain.com>;tag:12341111
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From: <sip:presentity@domain.com>;tag:232321
Call-ID: 121212@10.0.0.1
Cseq: 1 NOTIFY
Event: Presence
Subscription-State: active; expires=3599
Contact: sip:presentity@server.domain.com
Content-Type: application/cpim-pidf+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:cpim-pidf"
xmlns:rpids="urn:example-com:ietf:params:ns:sip-rpids"
entity="sip:presentity@domain.com">
<tuple id="432sd">
<status>
<basic>closed</basic>
</status>
<rpid:class>im</rpid:class>
<contact>im:presentity@domain.com</contact>
</tuple>
<tuple id="thr76jk">
<status>
<basic>open</basic>
</status>
<rpid:class>voice</rpid:class>
<contact>tel:2224055555@domain.com</contact>
</tuple>
</presence>
7.2 Watcher Information Specific Examples
The examples in this section use the presence event package with the
winfo template-package [8].
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Watcher information to a Presentity:
<?xml version="1.0"?>
<watcherinfo xmlns="urn:ietf:params:xml:ns:watcherinfo"
version="0" state="full">
<watcher-list resource="sip:presentity@domain.com"
package="presence">
<watcher status="active"
id="sr8fdsj"
duration-subscribed="509"
expiration="20"
event="approved">sip:watcherA@example.com"</watcher>
<watcher status="pending"
id="sr8fdsj"
duration-subscribed="501"
expiration="100"
event="subscribe">sip:watcherB@example.com"</watcher>
<watcher status="terminated"
id="sr8fdsj"
duration-subscribed="500"
expiration="0"
event="rejected">sip:watcherC@example.com"</watcher>
<watcher status="active"
id="sr8fdsj"
duration-subscribed="20"
expiration="30"
event="approved">sip:watcherD@domain.com"</watcher>
</watcher-list>
</watcherinfo>
7.2.1 Watcher Subscriber Makes Subscription to Gets All the Information
about Active Watchers
SUBSCRIBE request from the presentity including the filter:
SUBSCRIBE sip:presentity@domain.com
Via: SIP/2.0/TCP 10.0.0.1:5060;branch=xjfdsjfk
To: <sip:presentity@domain.com>
From: <sip:presentity@domain.com>;tag:12341111
Call-ID: 121212@10.0.0.1
Cseq: 1 SUBSCRIBE
Expires: 3600
Event: Presence.winfo
Contact: sip:presentity@client.domain.com
Content-Type: application/simple-filter+xml
Content-Length: ...
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<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter" pkgdef="winfo">
<filter id = "active" uri="sip:presentity@domain.com">
<what>
<condition base-element="//watcher">@package="presence" and @status="active"</condition>
<include>//watcher</include>
<include level="ancestor">//watcher</include>
</what>
</filter>
</filter-set>
Notification to the subscriber:
NOTIFY sip:presentity@client.domain.com SIP/2.0
Via: SIP/2.0/TCP presence.domain.com:5060;branch=xjfder
To: sip:presentity@domain.com;tag:12341111
From: sip:presentity@domain.com;tag:232321
Call-ID: 121212@10.0.0.1
Cseq: 1 NOTIFY
Contact: sip:presentity@server.domain.com
Event: Presence.winfo
Content-Type: application/watcherinfo+xml
Content-Length: ...
<?xml version="1.0"?>
<watcherinfo xmlns="urn:ietf:params:xml:ns:watcherinfo"
version="0" state="full">
<watcher-list resource="sip:presentity@domain.com"
package="presence">
<watcher status="active"
id="sr8fdsj"
duration-subscribed="509"
expiration="20"
event="approved">sip:watcherA@example.com"</watcher>
<watcher status="active"
id="sr8fdsj"
duration-subscribed="20"
expiration="30"
event="approved">sip:watcherD@domain.com"</watcher>
</watcher-list>
</watcherinfo>
7.2.2 Watcher Subscriber Requests Information of Watchers with Specific
Subscription Duration Conditions
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SUBSCRIBE request from the presentity including the filter:
SUBSCRIBE sip:presentity@domain.com
Via: SIP/2.0/TCP 10.0.0.1:5060;branch=xjfdsjfk
To: <sip:presentity@domain.com>;tag:12341111
From: <sip:presentity@domain.com>
Call-ID: 121212@10.0.0.1
Cseq: 1 SUBSCRIBE
Expires: 0
Event: Presence.winfo
Contact: <sip:presentity@client.domain.com>
Content-Type: application/simple-filter+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<ev-filter-set xmlns="urn:ietf:params:xml:ns:simple-filter" pkgdef="winfo">
<ev-filter id = "history" uri="sip:presentity@domain.com">
<what>
<condition base-element="//watcher">@package="presence" and @duration-subscribed>500</condition>
<include>//watcher</include>
<include level="ancestor">//watcher</include>
</what>
</ev-filter>
</ev-filter-set>
Notification to the subscriber:
NOTIFY sip:presentity@client.domain.com SIP/2.0
Via: SIP/2.0/TCP presence.domain.com:5060;branch=xjfder
To: sip:presentity@domain.com;tag:12341111
From: sip:presentity@domain.com;tag:232321
Call-ID: 121212@10.0.0.1
Cseq: 1 NOTIFY
Contact: sip:presentity@server.domain.com
Event: Presence.winfo
Content-Type: application/watcherinfo+xml
Content-Length: ...
<?xml version="1.0"?>
<watcherinfo xmlns="urn:ietf:params:xml:ns:watcherinfo"
version="0" state="full">
<watcher-list resource="sip:presentity@domain.com"
package="presence">
<watcher status="active"
id="sr8fdsj"
duration-subscribed="509"
expiration="20"
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event="approved">sip:watcherA@example.com"</watcher>
<watcher status="pending"
id="sr8fdsj"
duration-subscribed="501"
expiration="100"
event="subscribe">sip:watcherB@example.com"</watcher>
</watcher-list>
</watcherinfo>
7.2.3 Watcher Subscriber Requests Specific Watcher Info On Specific
Triggers
This filter selects watcher information notifications [7] to be sent
when the pending subscription status has changed from 'pending' to
'terminated'. In the notification, only the watchers that have a
status of 'terminated' and an event of 'rejected' are included.
SUBSCRIBE request from the Watcher Subscriber including the filter:
SUBSCRIBE sip:presentity@domain.com
Via: SIP/2.0/TCP 10.0.0.1:5060;branch=xjfdsjfk
To: <sip:presentity@domain.com>;tag:12341111
From: <sip:presentity@domain.com>
Call-ID: 121212@10.0.0.1
Cseq: 1 SUBSCRIBE
Expires: 0
Event: Presence.winfo
Contact: <sip:presentity@client.domain.com>
Content-Type: application/simple-filter+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<ev-filter-set xmlns="urn:ietf:params:xml:ns:simple-winfo-filter" pkgdef="winfo">
<ev-filter id = "filter-X" uri="sip:presentity@domain.com">
<what>
<condition base-element="//watcher">@package="presence" and @status="active" and event="rejected"</condition>
<include>//watcher</include>
<include level="ancestor">//watcher</include>
</what>
<trigger>
<changed changed-from="pending" changed-to="terminated">//@status</changed>
</trigger>
</ev-filter>
</ev-filter-set>
A 2nd Winfo document is created due to some change:
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<?xml version="1.0"?>
<watcherinfo xmlns="urn:ietf:params:xml:ns:watcherinfo"
version="0" state="full">
<watcher-list resource="sip:presentity@domain.com"
package="presence">
<watcher status="active"
id="sr8fdsj"
duration-subscribed="509"
expiration="20"
event="approved">sip:watcherA@example.com"</watcher>
<watcher status="terminated"
id="sr8fdsj"
duration-subscribed="501"
expiration="100"
event="rejected">sip:watcherB@example.com"</watcher>
<watcher status="terminated"
id="sr8fdsj"
duration-subscribed="500"
expiration="0"
event="rejected">sip:watcherC@example.com"</watcher>
<watcher status="active"
id="sr8fdsj"
duration-subscribed="20"
expiration="30"
event="approved">sip:watcherD@domain.com"</watcher>
</watcher-list>
</watcherinfo>
Notification to the subscriber, taking into account the <trigger> and <what> elements:
NOTIFY sip:presentity@client.domain.com SIP/2.0
Via: SIP/2.0/TCP presence.domain.com:5060;branch=xjfder
To: sip:presentity@domain.com;tag:12341111
From: sip:presentity@domain.com;tag:232321
Call-ID: 121212@10.0.0.1
Cseq: 1 NOTIFY
Contact: sip:presentity@server.domain.com
Event: Presence.winfo
Content-Type: application/watcherinfo+xml
Content-Length: ...
<?xml version="1.0"?>
<watcherinfo xmlns="urn:ietf:params:xml:ns:watcherinfo"
version="0" state="full">
<watcher-list resource="sip:presentity@domain.com"
package="presence">
<watcher status="terminated"
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id="sr8fdsj"
duration-subscribed="501"
expiration="100"
event="rejected">sip:watcherB@example.com"</watcher>
<watcher status="terminated"
id="sr8fdsj"
duration-subscribed="500"
expiration="0"
event="rejected">sip:watcherC@example.com"</watcher>
</watcher-list>
</watcherinfo>
8. Security Considerations
The presence of filters in the body in a SIP message has a
significant effect on the ways in which the request is handled at a
server. As a result, it is especially important that messages
containing this extension be authenticated and authorized.
Processing of requests and looking up filter criteria requires set
operations and searches, which can require some amount of
computation. This enables a DoS attack whereby a user can send
requests with substantial numbers messages with large contents, in
the hopes of overloading the server. To counter this, the server
SHOULD only allow filters with no more than about 20 occurances of
the <what>, <changed>, <added> and <removed> elements.
Requests can reveal sensitive information about a UA's capabilities.
If this information is sensitive, it SHOULD be encrypted using SIP S/
MIME capabilities.
All package specific security measures MUST be followed.
9. Acknowledgements
The authors would like to thank Tim Moran, Sreenivas Addagatla and
Juha Kalliokulju for their valuable input.
References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Sugano, H., "CPIM Presence Information Data Format",
draft-ietf-impp-cpim-pidf-07.txt, December 2002.
[3] Rosenberg, J., "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
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[4] Rosenberg, J., "Session Initiation Protocol (SIP) Extensions
for Presence", draft-ietf-simple-presence-10.txt, January
2003.
[5] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[6] Roach, A., "A Session Initiation Protocol (SIP) Event
Notification Extension for Collections",
draft-ietf-simple-event-list-01.txt, March 2003.
[7] Rosenberg, J., "An Extensible Markup Language (XML) Based
Format for Watcher Information",
draft-ietf-simple-winfo-format-04.txt, January 2003.
[8] Rosenberg, J., "A Watcher Information Event Template-Package
for SIP", draft-ietf-simple-winfo-package-05.txt, January
2003.
[9] Khartabil, H., "An Extensible Markup Language (XML) Based
Format for Event Notification Filtering",
draft-khartabil-simple-filter-format-01.txt, October 2003.
[10] Moran, T., "Requirements for Presence Specific Event
Notification Filtering",
draft-ietf-simple-pres-filter-reqs-01.txt, June 2003.
[11] Kiss, K., "Requirements for Filtering of Watcher Information",
draft-ietf-simple-winfo-filter-reqs-00.txt, April 2003.
[12] Niemi, A., "Requirements for Limiting the Rate of Event
Notifications",
draft-niemi-sipping-event-throttle-reqs-01.txt, February 2003.
[13] Mealling, M., "The IETF XML Registry",
draft-mealling-iana-xmlns-registry-04.txt, June 2002.
[14] Bray, T., "Exensible Markup Language (XML) 1.0 (Second
Edition)", W3C CR CR-xml11-20011006, October 2000.
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Authors' Addresses
Hisham Khartabil
Nokia
P.O. Box 321
Helsinki
Finland
Phone: +358 7180 76161
EMail: hisham.khartabil@nokia.com
Mikko Lonnfors
Nokia
Itamerenkatu 00180
Helsinki
Finland
Phone: + 358 50 4836402
EMail: mikko.lonnfors@nokia.com
Jose Costa-Requena
Nokia
P.O. Box 321
FIN-00045 NOKIA GROUP
FINLAND
Phone: +358 71800 8000
EMail: jose.costa-requena@nokia.com
Eva Leppanen
Nokia
P.O BOX 785
Tampere
Finland
Phone: +358 7180 77066
EMail: eva-maria.leppanen@nokia.com
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Khartabil, et al. Expires April 23, 2004 [Page 25]
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Khartabil, et al. Expires April 23, 2004 [Page 26]
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