SIMPLE H. Khartabil
Internet-Draft Telio
Expires: July 15, 2005 E. Leppanen
M. Lonnfors
J. Costa-Requena
Nokia
January 14, 2005
Functional Description of Event Notification Filtering
draft-ietf-simple-event-filter-funct-04
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.
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
material or to cite them other than as "work in progress."
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 July 15, 2005.
Copyright Notice
Copyright (C) The Internet Society (2005).
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
Khartabil, et al. Expires July 15, 2005 [Page 1]
Internet-Draft Functional Description of Filtering January 2005
achieved.
This document describes the operations a subscriber performs in order
to define filtering rules associated with event notification
information. The handling of responses to subscriptions carrying
filtering rules and the handling of notifications with filtering
rules applied to them is described. The document also describes how
the notifier behaves when receiving such filtering rules and how a
notification is constructed.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Client Operation . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Transport Mechanism . . . . . . . . . . . . . . . . . . . 5
3.2 SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 5
3.3 Subscriber Generating SUBSCRIBE Requests . . . . . . . . . 5
3.3.1 Structure of a Filter . . . . . . . . . . . . . . . . 5
3.3.2 Request-URI vs. Filter URI . . . . . . . . . . . . . . 6
3.3.3 Changing Filters within a Dialog . . . . . . . . . . . 6
3.3.4 Subscriber Interpreting SIP responses . . . . . . . . 7
3.4 Subscriber Processing of NOTIFY Requests . . . . . . . . . 7
4. Resource List Server Behaviour . . . . . . . . . . . . . . . . 8
4.1 Request-URI vs. Filter URI . . . . . . . . . . . . . . . . 8
4.2 Changing Filters within a Dialog . . . . . . . . . . . . . 10
5. Server Operation . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 10
5.2 Notifier Processing SUBSCRIBE Requests . . . . . . . . . . 10
5.2.1 Request-URI vs. Filter URI . . . . . . . . . . . . . . 11
5.2.2 Changing Filters within a Dialog . . . . . . . . . . . 11
5.3 Notifier Generating NOTIFY Requests . . . . . . . . . . . 12
5.3.1 Generation of NOTIFY Contents . . . . . . . . . . . . 13
5.3.2 Handling of Notification Triggering Rules . . . . . . 14
5.4 Handling Abnormal Cases . . . . . . . . . . . . . . . . . 14
6. XML Document Validation . . . . . . . . . . . . . . . . . . . 14
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1 Presence Specific Examples . . . . . . . . . . . . . . . . 15
7.1.1 Subscriber Requests Messaging Related Information . . 15
7.1.2 Subscriber Fetches Information about "Open"
Communication Means . . . . . . . . . . . . . . . . . 17
7.1.3 Subscriber Requests Notifications when
Presentity's Status Changes . . . . . . . . . . . . . 19
7.2 Watcher Information Specific Examples . . . . . . . . . . 21
7.2.1 Watcher Subscriber Makes Subscription to Get All
the Information about Active Watchers . . . . . . . . 22
7.2.2 Watcher Subscriber Requests Information of
Watchers with Specific Subscription Duration
Khartabil, et al. Expires July 15, 2005 [Page 2]
Internet-Draft Functional Description of Filtering January 2005
Conditions . . . . . . . . . . . . . . . . . . . . . . 24
7.2.3 Watcher Subscriber Requests Specific Watcher Info
On Specific Triggers . . . . . . . . . . . . . . . . . 25
8. Security Considerations . . . . . . . . . . . . . . . . . . . 27
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 28
11.1 Normative References . . . . . . . . . . . . . . . . . . . . 28
11.2 Informative References . . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 29
Intellectual Property and Copyright Statements . . . . . . . . 31
Khartabil, et al. Expires July 15, 2005 [Page 3]
Internet-Draft Functional Description of Filtering January 2005
1. Introduction
SIP event notification is described in [3]. 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. 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. However,
implementers need to be aware of the computational burden on the
source of the event notification. This is discussed further in
Section 8.
It is stated in [3] 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.
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 is described in [5].
2. 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.
"Content" refers to the XML document that appears in a notification
reflecting the state of a resource.
Khartabil, et al. Expires July 15, 2005 [Page 4]
Internet-Draft Functional Description of Filtering January 2005
3. Client Operation
3.1 Transport Mechanism
Transportation of the filter to the server is achieved by inserting
the XML document, as defined in [5], 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 [8],
[10] and [4] are otherwise followed.
As defined in [3], 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 [4] the filter
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, the body MUST be of
the MIME-Type 'application/simple-filter+xml'.
3.3.1 Structure of a Filter
Multiple filters MAY be included in one SUBSCRIBE. This is achieved
by including multiple <filter> elements in the filter [5]. Each
<filter> element may include a URI attribute.
A SUBSCRIBE request destined to a list URI [4] MAY include multiple
filters 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 overrides
any list specific filter, if any. The list specific filter may or
may not include a URI.
Khartabil, et al. Expires July 15, 2005 [Page 5]
Furthermore, regardless whether the SUBSCRIBE is destined to a list
URI or not, there can only be one filter applicable to a single
resource or domain within a single SUBSCRIBE. I.e. Each filter
within a subscription MUST uniquely identify one resource or one
domain.
A filter can be disabled by setting the 'enabled' attribute in the
<filter> element to "false". When a filter is disabled by setting
the 'enabled' attribute to "false", the <what> and <trigger> elements
MAY be omitted. Similarily, when a filter is re-enabled by setting
the 'enabled' attribute to "true", the <what> and <trigger> elements
MAY be omitted.
3.3.2 Request-URI vs. Filter URI
The URI in the filter defines the target resource, e.g. in the
Presence service case; it is the presentity's presence information to
which the filter is applied. The subscriber MAY choose to leave the
URI in the filter undefined. If the URI is not defined within the
filter, the filter applies to the resource identified in the
Request-URI. Similarly, the subscriber MAY define a filter URI. If
the Request-URI is a list URI [4], the filter 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 may be ignored or may be rejected. URI matching is done
according to the matching rules defined for a particular scheme (SIP
URI matching rules are defined in RFC3261 [2].
A filter may also be addressed to a domain using the "domain"
attribute instead of the "uri" attribute. In this case, the filter
applies to resources in that domain. This can be used when a
subscription is for a resource that is an event list with many
resources from differing domains. If an individual resource specific
filter is present along with the domain filter, this resource
specific filter overrides any domain specific filter, if any.
3.3.3 Changing Filters within a Dialog
The client MAY reset or change the filter by re-issuing a new
SUBSCRIBE request within the existing dialog. A SUBSCRIBE within the
exiting dialog that does not contain a filter is assumed to maintain
existing filters. This means that filters are persistent and are
only explicitly removed.
A client requiring removal of a filter may do so by using the
'remove="true"' attribute as defined in [5].
In the case the URI in the filter is that of a list, a client may
override the existing filter with a filter for an individual
resource, that is part of the list subscribed to earlier, by issuing
Khartabil, et al. Expires July 15, 2005 [Page 6]
Internet-Draft Functional Description of Filtering January 2005
a new SUBSCRIBE within the existing dialog and including a filter
specific for that individual resource. The new filter need not
include the original filter since a filter is only removed in the
manner indicated above.
A filter is replaced by the client re-issuing the filter using the
same filter ID and replacing the contents of the filter. Replacing a
filter by changing the filter ID and keeping the resource URI is
considered an error since this causes the server to assume that two
filters are placed for the same resource.
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 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 MAY arrive in a subsequent NOTIFY.
A non-200 class final responses indicate that no subscription or
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 [2] and [3].
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 filters have been applied.
If the NOTIFY indicates that a subscription has been terminated [3],
the subscription is assumed to be terminated. Behaviour in such
events is also described in [3].
If the subscription is indicated as active, NOTIFY requests are
handled as described in package specific documents and [3].
Khartabil, et al. Expires July 15, 2005 [Page 7]
Internet-Draft Functional Description of Filtering January 2005
4. Resource List Server Behaviour
The Resource List Server is defined in [4]. This section describes
how such entity behaves in the presence of a filter in a subscription
to a list.
4.1 Request-URI vs. Filter URI
If the URI is not defined within the filter, the filter applies to
the resource list identified in the Request-URI of the SUBSCRIBE
request. This results in the filter being applied to all the
notifications that the RLS issues to this subscription. The same
processing applies to a filter that defines a URI that matches the
request-URI of the SUBSCRIBE request. I.e. The filter applies to
all notifications that the RLS issues to this subscription.
If the URI indicated by the filter is for one resource whose URI is
one of the URIs that result from a lookup, by the RLS, on the
Request-URI, the filter for that particular resource is extracted and
propagated in the SUBSCRIBE request sent to that resource. It is
possible to have more than one filter in a SUBSCRIBE request body,
and therefore a filter 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@mydomain.com" is a resource belonging to that list, and the URI
in a filter is "sip:bob@mydomain.com", the filter specific for Bob is
extracted and placed in the body of the SUBSCRIBE sent to
"bob@mydomain.com".
If the URI indicated by the filter is for one resource whose URI is
NOT under the RLS administrative control, the RLS propagates the
filter to all the fanned out subscriptions sent to destinations
outside the administrative domain of the RLS. This is to accommodate
the scenario where the subscriber knows that there are sub-lists in
the event list that are under a different administrative domain than
where the original subscription was sent to, and the subscriber
wishes to set a filter for a resource in that sub-list.
If the URI indicated by the filter is for one resource whose URI is
under the RLS administrative control but is not part of the resource
list that the subscription was addressed to, the filter is not
propagated. In this case, it is the RLS responsibility to make sure
than this filter is applied to notifications issued, if information
about that resource is present.
For example: If we have 2 lists, each located on its own RLS:
List1 (list1@example1.com) on RLS1 has: bob@example1.com
Khartabil, et al. Expires July 15, 2005 [Page 8]
Internet-Draft Functional Description of Filtering January 2005
list2@example2.com
List2 on RLS2 has: alice@example2.com sarah@example1.com
(Note: list2 is a resource in list1)
RLS1 receives the following SUBSCRIBE request (the SUBSCRIBE is for
addressed to list1 and contains 2 filters: one for sarah@example1.com
and the other for alice@example2.com):
SUBSCRIBE sip:List1@example1.com SIP/2.0
...
<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<ns-bindings>
<ns-binding prefix="pidf" urn="urn:ietf:params:xml:ns:pidf"/>
</ns-bindings>
<filter id="999" uri="sip:sarah@example1.com">
<what>
<include type="namespace">
urn:ietf:params:xml:ns:pidf</include>
<exclude>
//pidf:tuple/pidf:note</exclude>
</what>
</filter>
<filter id="8439" uri="sip:alice@example2.com">
<what>
<include>
//pidf:tuple/pidf:status/pidf:basic</include>
</what>
</filter>
</filter-set>
RLS1 fans out subscriptions to resources on list1. The text above
suggests that if a filter is destined to a resource that is not part
of the list and is outside the administrative domain of an RLS, then
that filter is propagated. The rest are consumed. In our example,
only the filter to alice@example2.com is propagated since
example2.com is not under the administrative domain of RLS1. The
filter to sarah@example1.com is consumed, and RLS1 needs to apply
that filter to notifications it receives.
URI matching is done according to the matching rules defined for a
particular scheme (SIP URI matching rules are defined in RFC3261
[2].
A filter may also be addressed to a domain using the "domain"
Khartabil, et al. Expires July 15, 2005 [Page 9]
Internet-Draft Functional Description of Filtering January 2005
attribute instead of the "uri" attribute. In this case, the filter
applies to resources in that domain and the RLS MUST NOT apply
filters to any notifications it sends, but instead MUST forward the
filter with all fanned out subscriptions to the notifiers.
As indicated in Section 3.3.1, multiple filters can be present in a
SUBSCRIBE request. Filters can also be added or modified as
indicated in Section 3.3.3. In such circumstances, an RLS MUST check
that there are no filters addressed to the same resource or domain
and if so, it MUST reject the SUBSCRIBE request with a "488" error
response.
4.2 Changing Filters within a Dialog
If an RLS receives a subscription refresh request with no filters
specified (empty payload), the RLS assumes that the client does not
wish to update the filters. If an RLS receives a subscription
refresh with a filter containing the 'remove="true"' attribute as
defined in [5], the RLS assumes that the client is removing that
filter identified by the filter ID.
If an RLS receives a subscription refresh request with a filter that
already exists (i.e. having the same filter ID), the RLS interprets
it as a replacement of the existing filter. Replacing a filter by
changing the filter ID and keeping the resource URI is considered an
error since this causes the RLS to assume that two filters are placed
for the same resource.
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 additional 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 field 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
Khartabil, et al. Expires July 15, 2005 [Page 10]
Internet-Draft Functional Description of Filtering January 2005
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 filters have not been accepted yet. The
acceptance of the filters MAY arrive in a subsequent NOTIFY.
Procedures described in section Section 5.4 are followed if an error
is encountered.
As indicated in Section 3.3.1, multiple filters can be present in a
SUBSCRIBE request. Filters can also be added or modified as
indicated in Section 3.3.3. In such circumstances, a server MUST
check that there are no filters addressed to the same resource or
domain and if so, it MUST reject the SUBSCRIBE request with a "488"
error response.
5.2.1 Request-URI vs. Filter URI
The subscriber may have chosen to leave the URI in the filter
undefined. If the URI is not defined within the filter, the filter
applies to the resource identified in the Request-URI.
Similarly, the subscriber may have chosen to include a URI in the
filter. In this case, the filter applies to all notifications sent
with content associated with the resource with that URI, for this
subscription. If the Request-URI and the URI in the filter mismatch,
the filter may be ignored or may be rejected. URI matching is done
according to the matching rules defined for a particular scheme (SIP
URI matching rules are defined in RFC3261 [2].
A filter may also be addressed to a domain using the "domain"
attribute instead of the "uri" attribute. In this case, the filter
applies to resources in that domain. The notifier MUST NOT apply
filters to any notifications it sends if the domain is not that of
its own, and MUST ignore it. Notifiers belonging to the domain MUST
apply the filter to all notifications it sends for that subscription,
unless policy dictates otherwise.
5.2.2 Changing Filters within a Dialog
If a server receives a subscription refresh request with no filters
specified (empty payload), it assumes that the client does not wish
to update the filters. If it receives a subscription refresh with a
filter containing the 'remove="true"' attribute as defined in [5],
the server assumes that the client is removing that filter identified
by the filter ID.
Khartabil, et al. Expires July 15, 2005 [Page 11]
Internet-Draft Functional Description of Filtering January 2005
If the server receives a subscription refresh request with a filter
that already exists (i.e. having the same filter ID), it interprets
it as a replacement of the existing filter. Replacing a filter by
changing the filter ID and keeping the resource URI is considered an
error since this causes the server to assume that two filters are
placed for the same resource.
5.3 Notifier Generating NOTIFY Requests
Upon receiving the SUBSCRIBE with the filter, the notifier SHOULD
retain the filter 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 in the
body.
If the response sent to the SUBSCRIBE was a "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 [3], 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 field of the SUBSCRIBE, or the
package specific default if the Accept header field is omitted.
Based on the contects of a filter, the following processing occurs:
o A filter with only a <what> element will result in sending the
requested resource state information in that <what> element
whenever there is a change in the resource state.
o A filter with only a <trigger> element will result in sending all
resource state information whenever there is a change in the
resource state that matches the triggers.
o A filter with a <what> and <trigger> elements will result in
sending the requested resource state information in that <what>
element whenever there is a change in the resource state that
matches the triggers.
When a filter is disabled (by setting the 'enabled' attribute to
"false"), all state and state changes are reported. A disabled
filter means the same thing as the absence of that filter. I.e. All
changes to a resource state result in issuing a notification to the
subscriber (assuming there are no other filters).
Khartabil, et al. Expires July 15, 2005 [Page 12]
Internet-Draft Functional Description of Filtering January 2005
When a filter is re-enabled, (by setting the 'enabled' attribute to
"true", or by omitting the 'enabled' attribute), the notifier behaves
as if the fliter has just been placed by the SUBSCRIBE request
enabling it. Immediate NOTIFY rules as stated in Section 5.3.1
apply.
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 <what> element unless the processing of the
filters will take too long or the NOTIFY request is following a "202"
response to the SUBSCRIBE request and is terminating the
subscription. In the case that the fliter is taking too long to
process, the NOTIFY request being sent may be empty or may be
populated with a pre-configured value as authorised to that
subscriber. If applying the filter results in no content to be
delivered, the NOTIFY MUST be sent with empty contents. If the
fliter contains <trigger> elements, the notifier ignores the trigger
values when generating the first NOTIFY request.
The input to the content filter is a package specific XML document,
e.g. [7] and [9] derived according to the package specific
specifications, ([8] and [10]).
The content is filtered according to the expressions in the <what>
element of the filter. 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
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 a filter requesting
unauthorised contents. It is therefore RECOMMENDED that notifiers
just ignore the parts of the filter where it is requesting
unauthorised info. I.e. The filter 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
Khartabil, et al. Expires July 15, 2005 [Page 13]
Internet-Draft Functional Description of Filtering January 2005
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 on an XML document is 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.
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 definition where the XML document of the
filter is not aligned with the XML schema of the filter format[5],
the notifier rejects the SUBSCRIBE request with a "488" response. A
Warning header field 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 was discovered after that, a
NOTIFY with a subscription-state of value 'terminated' is sent. An
event-reason-value "badfilter", introduced here, of subexp-params [3]
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. XML Document Validation
7. Examples
The following chapters include filtering examples for Presence and
Khartabil, et al. Expires July 15, 2005 [Page 14]
Internet-Draft Functional Description of Filtering January 2005
Watcher Information. The format of filter is according to [5].
7.1 Presence Specific Examples
This chapter describes three use cases where the presence information
filtering solution is utilised [8]. 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 [7]. It
includes two tuples: one for the instant messaging and another for
the voice related information.
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:rpid="urn:ietf:params:ns:rpid-tuple"
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 the <basic> element and all the parent elements
(this means the status, tuple and its root element), the <class>
element and the <contact> element. The filter is: <class> elements
that have values beginning with "MMS", "SMS" or "IM".
Khartabil, et al. Expires July 15, 2005 [Page 15]
In this case, the notification includes the contents of the tuple
that has the value "IM" in its <class> 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
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<ns-bindings>
<ns-binding prefix="pidf" urn="urn:ietf:params:xml:ns:pidf"/>
<ns-binding prefix="rpid"
urn="urn:ietf:params:xml:ns:pidf:rpid-tuple"/>
</ns-bindings>
<filter id="123" uri="sip:presentity@domain.com">
<what>
<include type="xpath">
//pidf:tuple[rpid:class="IM" or rpid:class="SMS"
or rpid:class="MMS"]/pidf:status/pidf:basic
</include>
<include type="xpath">
//pidf:tuple[rpid:class="IM" or rpid:class="SMS"
or rpid:class="MMS"]/rpid:class
</include>
<include type="xpath">
//pidf:tuple[rpid:class="IM" or rpid:class="SMS"
or rpid:class="MMS"]/pidf:contact
</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
Khartabil, et al. Expires July 15, 2005 [Page 16]
Internet-Draft Functional Description of Filtering January 2005
Event: Presence
Subscription-State: active; expires=3599
Contact: sip:presentity@server.domain.com
Content-Type: application/pidf+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:rpid="urn:example-com:ietf:params:ns:rpid-tuple"
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.
The filtered content is indicated with an expression. This
expression selects the <basic> element and all the parent elements
(this means the status, tuple and its root element), the <class>
element and the <contact> element. The filter is: the <basic>
element's value is "Open".
In this case the notification returns the contents of the tuple that
has both the value "open" inside the <status> element.
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: ...
Khartabil, et al. Expires July 15, 2005 [Page 17]
Internet-Draft Functional Description of Filtering January 2005
<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<ns-bindings>
<ns-binding prefix="pidf" urn="urn:ietf:params:xml:ns:pidf"/>
<ns-binding prefix="rpid"
urn="urn:ietf:params:xml:ns:pidf:rpid-tuple"/>
</ns-bindings>
<filter id="123" uri="sip:presentity@domain.com">
<what>
<include type="xpath">
//pidf:tuple/pidf:status[pidf:basic="open"]/pidf:basic
</include>
<include type="xpath">
//pidf:tuple[pidf:status/pidf:basic="open"]/rpid:class
</include>
<include type="xpath">
//pidf:tuple[pidf:status/pidf:basic="open"]/pidf:contact
</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/pidf+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:rpid="urn:example-com:ietf:params:ns:rpid-tuple"
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>
Khartabil, et al. Expires July 15, 2005 [Page 18]
Internet-Draft Functional Description of Filtering January 2005
</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">
<ns-bindings>
<ns-binding prefix="pidf" urn="urn:ietf:params:xml:ns:pidf"/>
<ns-binding prefix="rpid"
urn="urn:ietf:params:xml:ns:pidf:rpid-tuple"/>
</ns-bindings>
<filter id="123" uri="sip:presentity@domain.com">
<trigger>
<changed from="closed" to="open">
/pidf:presence/pidf:tuple/pidf:status/pidf:basic
</changed>
</trigger>
</filter>
</filter-set>
At some point during the subscription, 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:pidf"
xmlns:rpid="urn:example-com:ietf:params:ns:rpid-tuple"
entity="sip:presentity@domain.com">
Khartabil, et al. Expires July 15, 2005 [Page 19]
Internet-Draft Functional Description of Filtering January 2005
<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:pidf"
xmlns:rpid="urn:example-com:ietf:params:ns:rpid-tuple"
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
From: <sip:presentity@domain.com>;tag:232321
Call-ID: 121212@10.0.0.1
Khartabil, et al. Expires July 15, 2005 [Page 20]
Internet-Draft Functional Description of Filtering January 2005
Cseq: 1 NOTIFY
Event: Presence
Subscription-State: active; expires=3599
Contact: sip:presentity@server.domain.com
Content-Type: application/pidf+xml
Content-Length: ...
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:rpid="urn:example-com:ietf:params:ns:rpid-tuple"
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 winfo template-package with the
presence event package [10].
Khartabil, et al. Expires July 15, 2005 [Page 21]
Internet-Draft Functional Description of Filtering January 2005
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 Get 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: ...
Khartabil, et al. Expires July 15, 2005 [Page 22]
Internet-Draft Functional Description of Filtering January 2005
<?xml version="1.0" encoding="UTF-8"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<ns-bindings>
<ns-binding prefix="wi"
urn="urn:ietf:params:xml:ns:watcherinfo"/>
</ns-bindings>
<filter id="123" uri="sip:presentity@domain.com">
<what>
<include>
/wi:watcherinfo/wi:watcher-list[@package="presence"]/
wi:watcher[@status="active"]
</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>
Khartabil, et al. Expires July 15, 2005 [Page 23]
Internet-Draft Functional Description of Filtering January 2005
7.2.2 Watcher Subscriber Requests Information of Watchers with Specific
Subscription Duration Conditions
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"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-filter">
<ns-bindings>
<ns-binding prefix="wi"
urn="urn:ietf:params:xml:ns:watcherinfo"/>
</ns-bindings>
<filter id="123" uri="sip:presentity@domain.com">
<what>
<include>
/wi:watcherinfo/wi:watcher-list[@package="presence"]/
wi:watcher[@duration-subscribed>500]
</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: ...
Khartabil, et al. Expires July 15, 2005 [Page 24]
Internet-Draft Functional Description of Filtering January 2005
<?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-list>
</watcherinfo>
7.2.3 Watcher Subscriber Requests Specific Watcher Info On Specific
Triggers
This filter selects watcher information notifications [9] 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"?>
<filter-set xmlns="urn:ietf:params:xml:ns:simple-winfo-filter">
<ns-bindings>
<ns-binding prefix="wi"
urn="urn:ietf:params:xml:ns:watcherinfo"/>
</ns-bindings>
<filter id="123" uri="sip:presentity@domain.com">
Khartabil, et al. Expires July 15, 2005 [Page 25]
Internet-Draft Functional Description of Filtering January 2005
<what>
<include>
/wi:watcherinfo/wi:watcher-list[@package="presence"]/
wi:watcher[@status="terminated" and @event="rejected"]
</include>
</what>
<trigger>
<changed from="pending"
to="terminated">
//@status
</changed>
</trigger>
</filter>
</filter-set>
At some point during the subscription, a 2nd Winfo document is
created due to some change:
<?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 is created, taking into account the
<trigger> and <what> elements:
Khartabil, et al. Expires July 15, 2005 [Page 26]
Internet-Draft Functional Description of Filtering January 2005
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"
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 filters 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 can establish a
limit on the number of occurrences of the <what>, <changed>, <added>
and <removed> elements allowed in the filters. A default limit of 40
is RECOMMENDED, however, servers may raise or lower the limit
depending upon their specific engineered capacity.
Requests can reveal sensitive information about a UA's capabilities.
Khartabil, et al. Expires July 15, 2005 [Page 27]
Internet-Draft Functional Description of Filtering January 2005
If this information is sensitive, it SHOULD be encrypted using SIP
S/MIME capabilities [6]. All package specific security measures MUST
be followed.
Propagating filters in SUBSCRIBE requests to foreign domains reveals
sensitive information about a user's resource lists. It is therefore
required that an RLS does not forward a filter if that filter is
addressed to a resource that is under the administrative domain of
the RLS, but is not on the resource list. Section 4.1 shows an
example where such a scenario can occur.
It is important to note that a flitered document located at a
subscriber may project false reality. For example, if a subscriber
asked to be notified when a resource has changed his presence state
from closed to open but not from open to closed, then the subscriber
may afterwards be under the false impression that the resource's
presence state is open even long after the resource has changed it to
closed. Therefore, subscribers need to be sure what they put in a
filter, understand what they asked for and be prepared to be out of
sync with the real state of a resource.
9. IANA Considerations
A new event-reason-value "badfilter" is defined to represent the
event where the filter is not well formed and/or not accepted. No
IANA registration is required for this value.
10. Acknowledgements
The authors would like to thank George Foti, Tim Moran, Sreenivas
Addagatla, Juha Kalliokulju, Jari Urpalainen and Mary Barnes for
their valuable input.
11. References
11.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Rosenberg et al., J., Shulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[3] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[4] Roach, A., "A Session Initiation Protocol (SIP) Event
Khartabil, et al. Expires July 15, 2005 [Page 28]
Internet-Draft Functional Description of Filtering January 2005
Notification Extension for Resource Lists",
draft-ietf-simple-event-list-07.txt, December 2004.
[5] Khartabil, H., "An Extensible Markup Language (XML) Based Format
for Event Notification Filtering",
draft-ietf-simple-filter-format-04.txt, January 2005.
[6] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC
2633, June 1999.
11.2 Informative References
[7] Sugano, H., "Presence Information Data Format", RFC 3863,
Auguest 2004.
[8] Rosenberg, J., "Session Initiation Protocol (SIP) Extensions
for Presence", RFC 3856, July 2004.
[9] Rosenberg, J., "An Extensible Markup Language (XML) Based
Format for Watcher Information", RFC 3858, July 2004.
[10] Rosenberg, J., "A Watcher Information Event Template-Package
for SIP", RFC 3857, July 2004.
Authors' Addresses
Hisham Khartabil
Telio
P.O. Box 1203 Vika
Oslo
Norway
Phone: +47 2167 3544
EMail: hisham.khartabil@telio.no
Eva Leppanen
Nokia
P.O BOX 785
Tampere
Finland
Phone: +358 7180 77066
EMail: eva-maria.leppanen@nokia.com
Khartabil, et al. Expires July 15, 2005 [Page 29]
Internet-Draft Functional Description of Filtering January 2005
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
Khartabil, et al. Expires July 15, 2005 [Page 30]
Internet-Draft Functional Description of Filtering January 2005
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Khartabil, et al. Expires July 15, 2005 [Page 31]
