SIPPING J. Rosenberg
Internet-Draft dynamicsoft
Expires: January 16, 2005 H. Schulzrinne
Columbia University
O. Levin, Ed.
Microsoft Corporation
July 18, 2004
A Session Initiation Protocol (SIP) Event Package for Conference
State
draft-ietf-sipping-conference-package-05
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document defines a conference event package for the Session
Initiation Protocol (SIP) Events framework, along with a data format
used in notifications for this package. The conference package
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allows users to subscribe to a conference URI. Notifications are
sent about changes in the membership of this conference and
optionally about changes in the state of additional conference
components.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Conference Event Package . . . . . . . . . . . . . . . . . . . 6
3.1 Event Package Name . . . . . . . . . . . . . . . . . . . . 6
3.2 SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 6
3.3 Subscription Duration . . . . . . . . . . . . . . . . . . 6
3.4 NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 7
3.5 Notifier Processing of SUBSCRIBE Requests . . . . . . . . 7
3.6 Notifier Generation of NOTIFY Requests . . . . . . . . . . 7
3.7 Subscriber Processing of NOTIFY Requests . . . . . . . . . 8
3.8 Handling of Forked Requests . . . . . . . . . . . . . . . 8
3.9 Rate of Notifications . . . . . . . . . . . . . . . . . . 8
3.10 State Agents . . . . . . . . . . . . . . . . . . . . . . . 8
4. Conference Data Format . . . . . . . . . . . . . . . . . . . . 10
4.1 Conference Information . . . . . . . . . . . . . . . . . . 10
4.1.1 User Element . . . . . . . . . . . . . . . . . . . . . 10
4.1.1.1 User Attributes . . . . . . . . . . . . . . . . . 11
4.1.1.2 User Status Elements . . . . . . . . . . . . . . . 12
4.1.1.3 Media Information . . . . . . . . . . . . . . . . 13
4.1.1.3.1 Media Attributes . . . . . . . . . . . . . . . 13
4.1.1.3.2 Media Elements . . . . . . . . . . . . . . . . 14
4.1.1.4 User Role . . . . . . . . . . . . . . . . . . . . 14
4.1.2 Sidebar Element . . . . . . . . . . . . . . . . . . . 15
4.1.3 Additional Conference Identifiers . . . . . . . . . . 15
4.1.4 Policy URIs . . . . . . . . . . . . . . . . . . . . . 15
4.1.5 Recording . . . . . . . . . . . . . . . . . . . . . . 15
4.1.6 Streaming . . . . . . . . . . . . . . . . . . . . . . 16
4.2 Constructing Coherent State . . . . . . . . . . . . . . . 16
4.2.1 The Algorithm . . . . . . . . . . . . . . . . . . . . 17
4.3 Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.4 Example . . . . . . . . . . . . . . . . . . . . . . . . . 21
5. Security Considerations . . . . . . . . . . . . . . . . . . . 23
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
6.1 conference Event Package Registration . . . . . . . . . . 24
6.2 application/conference-info+xml MIME Registration . . . . 24
6.3 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:conference-info . . . . . . . . . . 24
6.4 XML Schema Registration . . . . . . . . . . . . . . . . . 25
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
8. Changes History . . . . . . . . . . . . . . . . . . . . . . . 27
8.1 Changes since -04 . . . . . . . . . . . . . . . . . . . . 27
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8.2 Changes since -03 . . . . . . . . . . . . . . . . . . . . 27
8.3 Changes since -02 . . . . . . . . . . . . . . . . . . . . 27
8.4 Changes since -01 . . . . . . . . . . . . . . . . . . . . 28
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.1 Normative References . . . . . . . . . . . . . . . . . . . . 29
9.2 Informative References . . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 30
Intellectual Property and Copyright Statements . . . . . . . . 32
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1. Introduction
The Session Initiation Protocol (SIP) [6] Events framework Events
Framework [7] defines general mechanisms for subscribing to, and
receiving notifications of, events within SIP networks. It
introduces the notion of a package, which is a specific
"instantiation" of the events framework for a well-defined set of
events. Here, we define an event package for SIP conferences. This
package provides the conference notification service as outlined in
the SIP conferencing framework [14]. As described there,
subscriptions to a conference URI are routed to the focus that is
handling the conference. It acts as the notifier, and provides
clients with updates on conference state.
The information provided by this package is comprised of conference
identifier(s), conference participants (optionally with their
statuses and media description), conference sidebars, conference
policy URIs, etc.
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2. Terminology
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 [2] and
indicate requirement levels for compliant implementations.
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3. Conference Event Package
The conference event package allows a user to subscribe to a
conference. In SIP, conferences are represented by URIs. These URIs
route to a SIP user agent, called a focus, that is responsible for
ensuring that all users in the conference can communicate with each
other, as described in Conferencing Framework [14]. The focus has
sufficient information about the state of the conference to inform
subscribers about it.
It is possible a participant in the conference may in fact be another
focus. In order to provide a more complete participant list, the
focus MAY subscribe to the conference package of the other focus to
discover the participant list in the cascaded conference. This
information can then be included in notifications by using of the
"cascaded-focus" attribute as specified by this package.
This section provides the details for defining a SIP Events package,
as specified by RFC 3265 [7].
3.1 Event Package Name
The name of this event package is "conference". This package name is
carried in the Event and Allow-Events header, as defined in RFC 3265
[7].
3.2 SUBSCRIBE Bodies
A SUBSCRIBE for a conference package MAY contain a body. This body
defines a filter to apply to the subscription. Filter documents are
not specified in this document, and at the time of writing, are
expected to be the subject of future standardization activity.
A SUBSCRIBE for a conference package MAY be sent without a body.
This implies the default subscription filtering policy. The default
policy is:
o Notifications are generated every time there is any change in the
state of the conference.
o Notifications do not normally contain full state; rather, they
only indicate the state that has changed. The exception is a
NOTIFY sent in response to a SUBSCRIBE. These NOTIFYs contain the
full state of the information requested by the subscriber.
3.3 Subscription Duration
The default expiration time for a subscription to a conference is one
hour. Once the conference ends, all subscriptions to that particular
conference are terminated, with a reason of "noresource" RFC 3265
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[7].
3.4 NOTIFY Bodies
As described in RFC 3265 [7], the NOTIFY message will contain bodies
that describe the state of the subscribed resource. This body is in
a format listed in the Accept header field of the SUBSCRIBE, or a
package-specific default if the Accept header field was omitted from
the SUBSCRIBE.
In this event package, the body of the notification contains a
conference information document. This document describes the state
of a conference. All subscribers and notifiers MUST support the
"application/conference-info+xml" data format described in Section 4.
The subscribe request MAY contain an Accept header field. If no such
header field is present, it has a default value of "application/
conference-info+xml". If the header field is present, it MUST
include "application/conference-info+xml", and MAY include any other
types capable of representing dialog state.
Of course, the notifications generated by the server MUST be in one
of the formats specified in the Accept header field in the SUBSCRIBE
request.
3.5 Notifier Processing of SUBSCRIBE Requests
The conference information contains very sensitive information.
Therefore, all subscriptions SHOULD be authenticated and then
authorized before approval. Authorization policy is at the
discretion of the administrator, as always. However, a few
recommendations can be made.
It is RECOMMENDED that all users in the conference be allowed to
subscribe to the conference.
3.6 Notifier Generation of NOTIFY Requests
Notifications SHOULD be generated for the conference whenever there
is a change in the state in any of the information delivered to the
subscriber.
The changes generally occur when a new participant joins (i.e. gets
"connected" to) or a participant leaves (i.e. gets "disconnected"
from) the conference.
Subject to a local focus policy, additional changes in participant's
status, changes in its media types, and other optional media
attributes MAY be reported by the focus.
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Changes in sidebar rosters SHOULD be reported by the focus to their
participants and MAY be reported to others, subject to local policy.
Changes in conference identifiers and policy URIs SHOULD be reported
by the focus to the conference participants.
3.7 Subscriber Processing of NOTIFY Requests
The SIP Events framework expects packages to specify how a subscriber
processes NOTIFY requests in any package specific ways, and in
particular, how it uses the NOTIFY requests to construct a coherent
view of the state of the subscribed resource.
Typically, the NOTIFY for the conference package will only contain
information about those users whose state in the conference has
changed. To construct a coherent view of the total state of all
users, a subscriber to the conference package will need to combine
NOTIFYs received over time.
Notifications within this package can convey partial information;
that is, they can indicate information about a subset of the state
associated with the subscription. This means that an explicit
algorithm needs to be defined in order to construct coherent and
consistent state. The details of this mechanism are specific to the
particular document type. See Section 4.2 for information on
constructing coherent information from an application/
conference-info+xml document.
3.8 Handling of Forked Requests
By their nature, the conferences supported by this package are
centralized. Therefore, SUBSCRIBE requests for a conference should
not generally fork. Users of this package MUST NOT install more than
a single subscription as a result of a single SUBSCRIBE request.
3.9 Rate of Notifications
For reasons of congestion control, it is important that the rate of
notifications not become excessive. As a result, it is RECOMMENDED
that the server not generate notifications for a single subscriber at
a rate faster than once every 5 seconds.
3.10 State Agents
Conference state is ideally maintained in the element in which the
conference resides. Therefore, the elements that maintain the
conference are the ones best suited to handle subscriptions to it.
Therefore, the usage of state agents is NOT RECOMMENDED for this
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package.
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4. Conference Data Format
Conference information is an XML document that MUST be well-formed
and SHOULD be valid. Dialog information documents MUST be based on
XML 1.0 and MUST be encoded using UTF-8. This specification makes
use of XML namespaces for identifying dialog information documents
and document fragments. The namespace URI for elements defined by
this specification is a URN [3], using the namespace identifier
'ietf' defined by [4] and extended by [1]. This URN is:
urn:ietf:params:xml:ns:conference-info
A conference information document begins with the root element tag
"conference-info".
4.1 Conference Information
Conference information begins with the top level element
"conference-info". This element has three mandatory attributes:
version: This mandatory attribute allows the recipient of conference
information documents to properly order them. Versions start at 0
and increment by one for each new document sent to a subscriber.
Versions are scoped within a subscription. Versions MUST be
represented using a 32 bit integer.
state: This mandatory attribute indicates whether the document
contains the full conference information, or whether it contains
only the information that has changed since the previous document
(partial).
entity: This mandatory attribute contains the conference URI that
identifies the conference being described in the document.
The "conference-info" element has zero or more "user" sub-elements
which contain information on the users in the conference. This is
followed by zero or more "sidebar" sub-elements which contain
information on the sidebars in the conference. This is followed by
zero or more "conf-uri" sub-elements which contain information on
additional URIs that the conference can be accessed by. This is
followed by zero or more "policy-uri" sub-elements which contain
information on additional URIs that the conference policies can be
accessed by. This is followed by "recording" and "streaming"
elements describing recording and streaming statuses of the
conference.
4.1.1 User Element
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4.1.1.1 User Attributes
The user element has one mandatory attribute, "uri" that indicates
the URI for the user in the conference. This is a logical
identifier, which corresponds to the authenticated identity of the
participant. The "uri" attribute MUST be unique in the user element
list because it is used as the key in partial notifications about
users' state.
If a conference participant has more than a single signaling dialog
associated with the conference, the conference focus MAY present the
user's aggregated information (e.g. the statuses) and display all
its media streams under a single user element.
Note, that the optional element "instance" of "media" (see below) MAY
be used in this case to specify the actual signaling dialog for each
media stream.
An anonymous participant in a conference SHOULD be represented by an
anonymous URI generated by the focus. For multiple anonymous
participants, the focus must ensure that each anonymous URI is
unique. The guidelines for generating anonymous URIs in RFC 3323 [8]
should be followed. For example,
"Anonymous1" <sip:anonymous1@anonymous.invalid>
could be used for a participant requesting privacy.
The optional attribute "display-name" contains a display name for the
user. The standard "xml:lang" language attribute can also be present
to indicate the language of the display-name.
The optional attribute "cascaded-focus" contains a conference URI
(different from the main conference URI) for users that are connected
to the main conference as a result of focus cascading. In accordance
with the SIP conferencing framework [14], this package allows for
representation of peer-to-peer (i.e. "flat") focus cascading only.
The actual cascading graph can not be deduced from the information
provided in the package alone. Advanced applications can construct
the graph by subscribing to both this package and the Dialog Package
[15] of the cascaded foci and correlating the relevant information.
If the main conference "state" is "full", the state of its user(s)
MUST "full". If the main conference "state" is "partial", the state
of its user(s) MAY be either "partial" or "full".
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4.1.1.2 User Status Elements
Three optional status elements are defined: status, joining-mode, and
disconnection-reason.
o "status": provides information about user's current level of
participation in the conference.
o "joining-mode": if present, provides information about the way the
user joined the conference.
o "disconnection-reason": if present, provides information about the
way the user left the conference.
The following statuses are defined for the "status" element:
connected: The user is a participant in the conference. Depending on
the media policies, he/she can send and receive media to and from
other participants.
disconnected: The user is not a participant in the conference and no
active dialog exists between the user and the focus.
on-hold: Active SIP dialog exists between a user and a focus, but
user is "on-hold" for this conference, i.e. neither he/she is
"hearing" the conference mix, nor is his/her media being mixed in
the conference. As an example, the user has asked to join the
conference using SIP, but his/her participation is pending based
on moderator approval. In the meantime he/she is hearing
music-on-hold or some other kind of related content.
muted-via-focus: Active SIP dialog exists between a user and a focus
and the user can "listen" to the conference, but user's media is
not being mixed into the conference. Note that sometimes a subset
of user media streams can be muted by focus (such as poor quality
video) while others (such as voice or IM) can still be active. In
this case, it is RECOMMENDED that the "aggregated" user
connectivity "status" reflects the status of the mostly active
media.
blocked: User is denied from ever participating in this conference.
pending: User is not yet in the session, but it is anticipated that
he/she will join in the near future.
calling: User is being called by the focus.
ringing: An PSTN ALERTING or SIP 180 Ringing was returned for the
outbound call, user is being alerted.
dialing-in: User is dialing into the conference, not yet in the
roster (probably being authenticated).
disconnecting: Focus is in the process of disconnecting user (either
DISCONNECT or BYE was sent to the user's device).
removed: This status is used to remove the user from the roster using
partial notifications mechanism.
Note that the defined transient states (e.g., calling, ringing, etc.)
could generate a lot of notifications. Implementations MAY choose
not to generate notifications on these to all participants if it will
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generate too much traffic.
The following statuses are defined for the "joining-mode" element:
dialed-in: The user dialed into the conference, i.e. sent INVITE to
the focus, which resulted in successful dialog establishment.
dialed-out: The focus has brought the user into the conference by
sending a successful INVITE to the user.
focus-owner: The user is the focus for this conference. This status
is used only when a participant UA acts as a conference focus.
The following statuses are defined for the disconnection-reason
element:
departed: The user sent a BYE, thus leaving the conference.
booted: The user was sent a BYE by the focus, booting him/her out of
the conference. Alternatively, the user tried to dial into to
conference without success because was rejected by the focus
according to local policy decisions.
failed: The server tried to bring the user into the conference, but
its attempt to contact the specific user resulted in a non-200
class final response. Alternatively, the user tried to dial into
the conference without success due to technical reasons.
4.1.1.3 Media Information
Each user has zero or more "media" sub-elements.
Each "media" element indicates the media that the user is currently
connected to. Here, "connected to" implies that a user has a media
line in his/her SDP [12] document(s). With this definition, a user
is connected to a media stream even if he/she is not sending any
media.
4.1.1.3.1 Media Attributes
The "media" element has a mandatory "media-type" attribute which
identifies the media type (e.g. audio, video, message and
application) and MUST have one of the values registered for "media"
of SDP [12].
The optional "id" attribute serves as a unique reference to a "media"
element within the "user" element. It MUST be included for each
"media" element for all notifications if the focus uses "partial"
user notifications for this conference. Otherwise, the "id"
attribute MAY be omitted.
If the user "state" is "full", the state of its "media" element(s)
MUST be "full". If the user "state" is "partial", the state of its
"media" element(s) MAY be either "partial" or "full".
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4.1.1.3.2 Media Elements
The "media" element has also an optional "proto" sub-element, which
MUST has the value registered for "proto" of SDP [12].
An optional "ssrc" sub-element, if present, carries the value of SSRC
(defined in RTP/RTCP [10]) as generated by the user for the stream it
sends.
When an RTP mixer generates a CSRC list according to RTP/RTCP [10],
it inserts a list of the SSRC identifiers of the sources that
contributed to the generation of a particular packet into the RTP
header of that packet. "An example application is audio conferencing
where a mixer indicates all the talkers whose speech was combined to
produce the outgoing packet, allowing the receiver to indicate the
current talker, even though all the audio packets contain the same
SSRC identifier (that of the mixer)."
An optional "info" sub-element, if present, carries a human readable
description for this stream populated by the focus. The value of
this element corresponds to the information media attribute "i" in
SDP [12].
An optional "label" sub-element, if present, carries a unique
identifier for this stream among all streams in the conference and is
assigned by the focus. The value of this element corresponds to the
"label" media attribute in SDP [12] and defined in [18].
An optional "instance" sub-element, if present, carries a URI, which
MUST uniquely identify the signaling dialog being used for
establishing of this media stream. In SIP, for example, values of
Contact URI or GRUU [17] can be used for this purpose. It is
RECOMMENDED to include the "instance" information for every user that
has more than a single dialog associated with the conference. This
element SHOULD NOT be included for an anonymous participant.
An optional "status" sub-element, if present, is used to remove
"media" elements during partial notifications.
Optional "snd-status" and "rcv-status" sub-elements, if present,
describe the status of media streams in each direction.
4.1.1.4 User Role
The optional "role" element conveys the role of the user in the
conference, e.g. participant, presenter, panelist, host, etc.
User's role MAY change dynamically in the course of the conference.
Also, a user MAY have more than a single role in one time.
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This document does not define fixed values for the "role" element,
instead it is expected that conferencing applications will define
custom-fit roles by templates.
4.1.2 Sidebar Element
The sidebar element is of the general "conference-type" and MAY use
all the attributes and elements defined by it. Typically, only the
"entity", which uniquely identifies the sidebar, and the "user"
elements will be useful to present to the majority of the
participants in the conference.
The "conference-type" mandatory attributes MUST be included for each
sidebar.
The value of the "version" attribute is meaningless for "sidebar"
elements and MUST be ignored because it is always overruled by the
"version" attribute of the main "conference-info".
If the main conference "state" is "full", the state of its sidebar(s)
MUST be "full". If the main conference "state" is "partial", the
state of its sidebar(s) MAY be either "full" or "partial".
The "entity" URI attribute MUST be unique among the sidebar
identifiers of the same conference. Attribute "entity" is used as
the key for "sidebar" elements in partial notifications for
"conference-info".
4.1.3 Additional Conference Identifiers
In addition to the Conference URI present in the "entity" attribute,
a conference MAY have additional URIs of various types. Connecting
to these URIs will result in joining to the same conference.
4.1.4 Policy URIs
A policy URI specifies where and how a certain policy pertaining to
the conference can be accessed. The actual policy name and usage is
deduced from the URI schema name.
An example for the "policy-uri" usage is inclusion of the URI of the
CPCP [16]. A subscriber to the Conference package can use the Policy
URI to access and modify the conference policy.
4.1.5 Recording
In many cases, legal regulations require conference providers to
announce to the participants that a specific conference is being
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recorded.
In addition to the recording "status" information, the "recording"
element MAY include the URIs specifying the location and the format
of the recorded data. Typically, the recorded data becomes available
after the conference ends. Multiple URIs can be provided, for
example, specifying different content types. For Web-Page embedded
media, a plain HTTP URI MAY be provided.
4.1.6 Streaming
The "streaming" element, if present, specifies whether the conference
output is being streamed (to general public, for example), in what
streaming format, and at what (e.g. multicast) addresses it can be
listened at. RTSP [11] is an example of such streaming protocol.
4.2 Constructing Coherent State
The conference information is described by a hierarchal XML structure
with the root element "conference-info". The root element is the
only element in the schema that carries meaningful version number for
all the elements in the document. The whole conference information
is associated with this version number.
The version number MUST be initialized with the value of the
"version" attribute from the "conference-info" element in the first
document received. Each time a new document is received, the value
of the local version number, and the "version" attribute in the new
document, are compared. If the value in the new document is one
higher than the local version number, the local version number is
increased by one, and the document is processed. If the value in the
document is more than one higher than the local version number, the
local version number is set to the value in the new document, the
document is processed, and the subscriber SHOULD generate a refresh
request to trigger a full state notification. If the value in the
document is less than the local version, the document is discarded
without processing.
Further processing of the conference information document depends on
whether it contains full or partial state. If it contains full
state, indicated by the value of the "state" attribute in the
"conference-info" element, the whole local content is flushed and
repopulated from the document.
If the document contains partial state, as indicated by the value of
the "state" attribute in the "conference-info" element, the document
is used to update the local content as described below.
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All sub-elements in the "conference-info" hierarchal XML structure
can be classified in two groups: those that carry relatively small
amount of data and those that can potentially carry a lot of data.
During partial notifications, the light elements are updated as
atomic pieces of data. On the other hand, elements that can carry a
substantial amount of data have the general "state" attribute
attached to them. That is in order to support partial notifications
for their content.
A "state" attribute of a child element in the document MUST adhere to
its parent "state". It means that if the parent's "state" is "full",
the state of its children MUST be "full". If the parent's "state" is
"partial", the state of its children MAY be either "partial" or
"full".
For elements with optional "state" attribute, if the attribute is not
included for an element, it means that the element's state is "full".
For a parent element with "state", its sub-elements with possible
multiple appearances under the parent have keys that uniquely
identify each element among others in the same list.
4.2.1 The Algorithm
The conference package subscriber locally maintains a local element
for each element in the schema and a table for each "element with
key(s)" in the schema. The tables are indexed by the key(s) defined
in schema for the element.
Starting from outer elements in the received document,
1. If the parent element contains full state, the element is
replaced with the new information as a whole.
2. Otherwise, if the parent element contains partial state,
2.1 For elements with keys, the subscriber compares the keys received
in the update with the keys in the local tables.
2.1.1 If a key doesn't exist in the local table, a row is added, and
its content is set to the element information from the update.
2.1.2 Otherwise, if a key of the same value does exist, for each
sub-element in the row the algorithm is applied from step 2.2.
2.2 For each atomic element received in the schema, the element is
replaced with the new information as a whole. Also, for each
non-atomic element received in the schema with either no "state"
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attribute included or the state attribute is set to "full", the
element is replaced with the new information as a whole.
2.2.1 If the updated or created element carries the "removed" status,
that element SHOULD be removed from the local content. If the
element is updated or created, such that it is empty, that element
MAY be removed from the local content at any time.
2.3 For each non-atomic element with the state attribute set to
"partial", the algorithm is applied recursively starting from step 2.
4.3 Schema
<?xml version="1.0" encoding="UTF-8" ?>
<xs:schema targetNamespace="urn:ietf:params:xml:ns:conference-info" xmlns:tns="urn:ietf:params:xml:ns:conference-info" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="urn:ietf:params:xml:ns:conference-info" elementFormDefault="qualified" attributeFormDefault="unqualified">
<!--
This import brings in the XML language attribute xml:lang
-->
<xs:import namespace="http://www.w3.org/XML/1998/namespace" schemaLocation="http://www.w3.org/2001/03/xml.xsd" />
<xs:element name="conference-info" type="tns:conference-type"/>
<xs:simpleType name="state-type">
<xs:restriction base="xs:string">
<xs:enumeration value="full" />
<xs:enumeration value="partial" />
</xs:restriction>
</xs:simpleType>
<xs:complexType name="conference-type">
<xs:sequence>
<xs:element name="user" type="user-type" minOccurs="0" maxOccurs="unbounded" />
<xs:element name="sidebar" type="conference-type" minOccurs="0" maxOccurs="unbounded" />
<xs:element name="conf-ids" type="conf-ids-type" minOccurs="0" maxOccurs="1" />
<xs:element name="policy-ids" type="policy-ids-type" minOccurs="0" maxOccurs="1" />
<xs:element name="recording" type="recording-type" minOccurs="0" maxOccurs="1" />
<xs:element name="streaming" type="streaming-type" minOccurs="0" maxOccurs="1" />
<xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />
</xs:sequence>
<xs:attribute name="version" type="xs:nonNegativeInteger" use="required"/>
<xs:attribute name="state" type="tns:state-type" use="required"/>
<xs:attribute name="entity" type="xs:anyURI" use="required"/>
<xs:anyAttribute />
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</xs:complexType>
<xs:complexType name="conf-ids-type">
<xs:sequence>
<xs:element name="conf-uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded" />
<xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />
</xs:sequence>
<xs:anyAttribute />
</xs:complexType>
<xs:complexType name="policy-ids-type">
<xs:sequence>
<xs:element name="policy-uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded" />
<xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />
</xs:sequence>
<xs:anyAttribute />
</xs:complexType>
<xs:complexType name="recording-type">
<xs:sequence>
<xs:element name="uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded" />
<xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />
</xs:sequence>
<xs:attribute name="status" type=="stream-status-type" use="required"/>
<xs:anyAttribute />
</xs:complexType>
<xs:complexType name="streaming-type">
<xs:sequence>
<xs:element name="uri" type="xs:anyURI" minOccurs="0" maxOccurs="unbounded" />
<xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded" />
</xs:sequence>
<xs:attribute name="status" type="stream-status-type" use="required"/>
<xs:anyAttribute />
</xs:complexType>
<xs:complexType name="user-type">
<xs:sequence>
<xs:element name="status" type="tns:user-status-type" minOccurs="0"/>
<xs:element name="joining-mode" type="tns:user-joining-mode-type" minOccurs="0"/>
<xs:element name="disconnection-reason" type="tns:user-disconnection-reason-type" minOccurs="0"/>
<xs:element name="media" type="tns:media-type" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="role" type="xs:string" minOccurs="0" maxOccurs="unbounded"/>
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<xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="uri" type="xs:anyURI" use="required"/>
<xs:attribute name="display-name" type="xs:string" use="optional"/>
<xs:attribute ref="xml:lang" use="optional"/>
<xs:attribute name="cascaded-focus" type="xs:anyURI" use="optional"/>
<xs:attribute name="state" type="tns:state-type" use="optional"/>
<xs:anyAttribute />
</xs:complexType>
<xs:simpleType name="user-status-type">
<xs:restriction base="xs:string">
<xs:enumeration value="connected"/>
<xs:enumeration value="disconnected"/>
<xs:enumeration value="on-hold"/>
<xs:enumeration value="muted-via-focus"/>
<xs:enumeration value="blocked"/>
<xs:enumeration value="pending"/>
<xs:enumeration value="calling"/>
<xs:enumeration value="ringing"/>
<xs:enumeration value="dialing-in"/>
<xs:enumeration value="disconnecting"/>
<xs:enumeration value="removed"/>
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="user-joining-mode-type">
<xs:restriction base="xs:string">
<xs:enumeration value="dialed-in" />
<xs:enumeration value="dialed-out" />
<xs:enumeration value="focus-owner" />
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="user-disconnection-reason-type">
<xs:restriction base="xs:string">
<xs:enumeration value="departed" />
<xs:enumeration value="booted" />
<xs:enumeration value="failed" />
</xs:restriction>
</xs:simpleType>
<xs:complexType name="media-type">
<xs:sequence>
<xs:element name="proto" type="xs:string" minOccurs="0"/>
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<xs:element name="ssrc" type="xs:nonNegativeInteger" minOccurs="0"/>
<xs:element name="info" type="xs:string" minOccurs="0"/>
<xs:element name="label" type="xs:string" minOccurs="0"/>
<xs:element name="instance" type="xs:anyURI" minOccurs="0"/>
<xs:element name="status" type="tns:media-status-type" minOccurs="0"/>
<xs:element name="snd-status" type="tns:stream-status-type" minOccurs="0"/>
<xs:element name="rcv-status" type="tns:stream-status-type" minOccurs="0"/>
<xs:any processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="media" type="xs:string" use="required"/>
<xs:attribute name="id" type="nonNegativeInteger" use="optional"/>
<xs:attribute name="state" type="tns:state-type" use="optional"/>
<xs:anyAttribute />
</xs:complexType>
<xs:simpleType name="media-status-type">
<xs:restriction base="xs:string">
<xs:enumeration value="removed" />
</xs:restriction>
</xs:simpleType>
<xs:simpleType name="stream-status-type">
<xs:restriction base="xs:string">
<xs:enumeration value="on"/>
<xs:enumeration value="off"/>
<xs:enumeration value="muted" />
</xs:restriction>
</xs:simpleType>
</xs:schema>
4.4 Example
The following is an example conference information document:
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<?xml version="1.0" encoding="utf-8" ?>
<conference-info version="0" state="full" entity="sip:conf233@example.com">
<user uri="sip:bob@example.com" display-name="Bob Jones">
<status>connected</status>
<joining-mode>dialed-in</joining-mode>
<media media="audio">
<proto>RTP/AVP</proto>
<ssrc>583398</ssrc>
</media>
</user>
<user uri="sip:barbara@example.com" display-name="Barbara Jones">
<status>on-hold</status>
</user>
<user uri="sip:bill@example.com" display-name="Bill Minelli">
<status>on-hold</status>
</user>
<sidebar version="0" state="full" entity="sip:conf233.1@example.com">
<user uri="sip:barbara@example.com" />
<user uri="sip:bill@example.com" />
</sidebar>
<conf-ids>
<conf-uri>tel:+18005671234</conf-uri>
<conf-uri>h323:conf545@example.com</conf-uri>
</conf-ids>
<recording status="on">
<uri>http://quicktime.streaming.com/54634/recording.mov</uri>
<uri>http://real.streaming.com/54634/recording.ram</uri>
<uri>http://windowsmedia.streaming.com/54634/recording.wmv</uri>
<uri>http://www.streaming.com/54634/recording.html</uri>
</recording>
</conference-info>
This conference currently has three users, two of which are in a
sidebar conversation. The conference is being recorded. There are
additional means to join the conference either by phone using tel URI
[14] or by H.323 protocol using H.323 URL [13].
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5. Security Considerations
Subscriptions to conference state can reveal very sensitive
information. For this reason, the document recommends authentication
and authorization, and provides guidelines on sensible authorization
policies.
Since the data in notifications is sensitive as well, end-to-end SIP
encryption mechanisms using S/MIME SHOULD be used to protect it.
Since a focus provides participants identity information using this
event package, participant privacy needs to be taken into account. A
focus MUST support requests by participants for privacy. Privacy can
be indicated by the conference policy - for every participant or
select participants. It can also be indicated in the session
signaling. In SIP this can be done using the Privacy header field
described in RFC 3323 [8]. For a participant requesting privacy, no
identity information SHOULD be revealed by the focus such as a URI
(e.g. the Address of Record, Contact, or GRUU). For these cases,
the anonymous URI generation method outlined in section "User
Element" of this document MUST be followed.
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6. IANA Considerations
This document registers a SIP event package, a new MIME type,
application/conference-info+xml, a new XML namespace, and a new XML
schema.
6.1 conference Event Package Registration
This specification registers an event package, based on the
registration procedures defined in RFC 3265 [7]. The following is
the information required for such a registration:
Package Name: conference
Package or Template-Package: This is a package.
Published Document: RFC XXXX (Note to RFC Editor: Please fill in XXXX
with the RFC number of this specification).
Person to Contact: Jonathan Rosenberg, jdrosen@jdrosen.net.
6.2 application/conference-info+xml MIME Registration
MIME media type name: application
MIME subtype name: conference-info+xml
Mandatory parameters: none
Optional parameters: Same as charset parameter application/xml as
specified in RFC 3023 [5].
Encoding considerations: Same as encoding considerations of
application/xml as specified in RFC 3023 [5].
Security considerations: See Section 10 of RFC 3023 [5] and Section 5
of this specification.
Interoperability considerations: none.
Published specification: This document.
Applications which use this media type: This document type has been
used to support SIP conferencing applications.
Additional Information:
Magic Number: None
File Extension: .cif or .xml
Macintosh file type code: "TEXT"
Personal and email address for further information: Jonathan
Rosenberg, <jdrosen@jdrosen.net>
Intended usage: COMMON
Author/Change controller: The IETF.
6.3 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:conference-info
This section registers a new XML namespace, as per the guidelines in
[1].
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URI: The URI for this namespace is
urn:ietf:params:xml:ns:conference-info.
Registrant Contact: IETF, SIPPING working group, <sipping@ietf.org>,
Jonathan Rosenberg <jdrosen@jdrosen.net>.
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>Conference Information Namespace</title>
</head
<body>
<h1>Namespace for Conference Information</h1>
<h2>urn:ietf:params:xml:ns:conference-info</h2>
<p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
</body>
</html>
END
6.4 XML Schema Registration
This specification registers a schema, as per the guidelines in in
[1].
URI: please assign.
Registrant Contact: IETF, SIPPING Working Group
(sipping@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net).
XML: The XML can be found as the sole content of Section 4.3.
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7. Acknowledgements
The authors would like to thank Dan Petrie, Sean Olson, Alan
Johnston, and Rohan Mahy for their comments and inputs.
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8. Changes History
8.1 Changes since -04
o
o "Sidebar-type" has been removed. "Sidebar" conference element is
defined using the general "conference-type".
o "Recording" conference attribute has been replaced with
"recording" and "streaming" elements within "conference-type".
New "recording-type" and "streaming-type" have been introduced.
o Attribute "state" has been added to "user-type".
o Element "media-stream" within "user-type" has been renamed to
"media".
o Element "role" within "user-type" has been introduced.
o The following statuses have been added to "user-status-type":
blocked, pending, calling, ringing, dialing-in, disconnecting,
removed.
o User status "muted-by-focus" has been renamed to
"muted-via-focus".
o Attributes "id" and "state" have been added to "media-type".
o Elements "status", "snd-status" and "rcv-status" have been added
to "media-type".
o Element "dialog-id" has been renamed to "instance".
o "Constructing Coherent State" section has been updated to include
user and media partial notifications.
8.2 Changes since -03
o "Constructing Coherent State" section has been updated.
o In order to support partial notifications, two placeholders
"conference-ids" and "policy-ids" (for "conf-uri" and "policy-uri"
elements, correspondingly) are created.
o Discussion and security considerations regarding anonymous
participation have been added.
o Optional elements "dialog-uri", "info" and "label" per media
stream are added.
8.3 Changes since -02
o State "muted-by-focus" is added to user's status.
o Optional conference attribute "recording" is added.
o Policy URI placeholder (i.e. element "policy-uri") is created.
o Example's syntax is corrected.
o Optional attribute "cascaded-focus" URI per user is added.
o Optional additional conference identifiers (i.e. element
"conf-uri") are added.
o In order to cover all possible cases, participant's status is
expressed using three optional statuses: "status", "joining-mode"
and "disconnection-reason". That is instead of "activity-status",
"history-status" and "is-on-dial-out-list".
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8.4 Changes since -01
o Package parameters are removed. Decision about performing
"recursive" membership algorithm is perceived as a focus local
policy.
o General information (i.e. pointers to additional available
services) is removed. The defined XML schema can be extended in
future to include those when XCON work matures.
o Dialog information is removed. It can be obtained by direct
subscription to a dialog package of a participant.
o Media stream information is aligned with SDP definitions (media
and proto) and SSRC attribute is added.
o Participant's status is expressed using two optional statuses:
"activity" and "history". Optional "is-on-a-dial-out-list"
indication is added.
o Normative references to XCON work are removed.
o Optional sidebar rosters are added.
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9. References
9.1 Normative References
[1] Mealling, M., "The IETF XML Registry",
draft-mealling-iana-xmlns-registry-05 (work in progress), June
2003.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Moats, R., "URN Syntax", RFC 2141, May 1997.
[4] Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
August 1999.
[5] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
3023, January 2001.
[6] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[7] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[8] Peterson, J., "A Privacy Mechanism for the Session Initiation
Protocol (SIP)", RFC 3323, November 2002.
[9] Camarillo, G., Eriksson, G., Holler, J. and H. Schulzrinne,
"Grouping of Media Lines in the Session Description Protocol
(SDP)", RFC 3388, December 2002.
[10] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", STD 64,
RFC 3550, July 2003.
9.2 Informative References
[11] Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming
Protocol (RTSP)", RFC 2326, April 1998.
[12] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998.
[13] Levin, O., "H.323 Uniform Resource Locator (URL) Scheme
Registration", RFC 3508, April 2003.
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[14] Rosenberg, J., "A Framework for Conferencing with the Session
Initiation Protocol",
draft-ietf-sipping-conferencing-framework-02 (work in
progress), June 2004.
[15] Rosenberg, J. and H. Schulzrinne, "An INVITE Inititiated Dialog
Event Package for the Session Initiation Protocol (SIP)",
draft-ietf-sipping-dialog-package-04 (work in progress),
February 2004.
[16] Koskelainen, P. and H. Khartabil, "Requirements for Conference
Policy Control Protocol", draft-ietf-xcon-cpcp-reqs-03 (work in
progress), April 2004.
[17] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent (UA) URIs (GRUU) in the Session Initiation Protocol
(SIP)", draft-ietf-sip-gruu-02 (work in progress), July 2004.
[18] Levin, O. and G. Camarillo, "The SDP (Session Description
Protocol) Label Attribute",
draft-levin-mmusic-sdp-media-label-00 (work in progress), July
2004.
Authors' Addresses
Jonathan Rosenberg
dynamicsoft
600 Lanidex Plaza
Parsippany, NJ 07054
US
Phone: +1 973 952-5000
EMail: jdrosen@dynamicsoft.com
URI: http://www.jdrosen.net
Henning Schulzrinne
Columbia University
M/S 0401
1214 Amsterdam Ave.
New York, NY 10027
US
EMail: schulzrinne@cs.columbia.edu
URI: http://www.cs.columbia.edu/~hgs
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Orit Levin (editor)
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
USA
EMail: oritl@microsoft.com
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Acknowledgment
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