Internet Engineering Task Force
Internet Draft Petri Koskelainen
Nokia
draft-koskelainen-sipping-conf-policy-req-00.txt
February 24, 2003
Expires: August 2003
Requirements for conference policy data
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Abstract
The conference participants may communicate with the conference
policy server, using a conference policy control protocol (CPCP)
which is a strictly client-server transactional protocol. This
document describes the requirements for conference policy data. Media
policy related requirements are beyond the scope of this document.
CPCP protocol is not mandatory and the only mechanism to manipulate
conference policy data in a conference. For example, web interface
can be used as well to perform conference policy manipulation.
However, for automata a protocol is needed.
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1 Introduction
The conferencing framework document [1] describes the overall
architecture, terminology, and protocol components needed for multi-
party conferencing. It defines a logical function called a conference
policy server which can store and manipulate rules associated with
participation in a conference. These rules include directives on the
lifespan of the conference, who can and cannot join the conference,
definitions of roles available in the conference and the
responsibilities associated with those roles, and policies on who is
allowed to request which roles.
The conference policy control protocol (CPCP) is a client-server
protocol that can be used by the participant to manipulate the rules
associated with the conference.
The conference policy is represented by a URI. There is a unique
conference policy for each conference. The conference policy URI
points to a conference policy server which can manipulate that
conference policy.
Conferencing framework describes also conference notification service
that is a logical function provided by the focus. It means that the
focus can act as a notifier, accepting subscriptions to the
conference state.
Note that CPCP is not the only mechanism to manipulate conference
policy, but other mechanisms exists as well, such as Web interface.
This document can be used with other documents, such as Conferencing
framework document [1], and SIP call control - conferencing for user
agents [2].
Moreover, [4], [5], [6] give useful background information about
conferencing and floor control.
1.1 Conventions of This Document
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 [3].
2 Terminology
This document uses the definitions from [1].
Additional definitions:
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ACL: Access Control List. Defines which users are eligible to
join a conference. Each conference has its own ACL.
Moderator: A special (privileged) role for a user that is
allowed to manipulate conference policy and override policy
decisions made by other users.
Privilege: A privilege is a right to perform a manipulation
operation for a conference. It is user permission such as
"MODIFY ACL", "TERMINATE CONFERENCE", "INVITE USERS",
"EJECT USERS", "MODIFY FLOOR POLICY", "MODIFY MEDIA
POLICY", "HAND OFF A PRIVILEGE TO ANOTHER USER", "FLOOR
CONTROL CHAIR". (assuming that privileges are individual
instead of group based e.g. senior-members have all
privileges)
3 Integration with Floor Control
Floor control is an optional feature often used by conferencing
applications. It enables applications or users to gain safe and
mutually exclusive or non-exclusive input access to a shared object
or resource. We define a floor as the temporary permission for a
conference participant to access or manipulate a specific shared
resource or group of resources.
We assume that the ability of users to create floors is governed by
the conference policy. Privileged conference user may use floor
control protocol (see [7], [8]) to create floors.
The conference policy defines who is allowed to create, change, and
remove floors using the floor control protocol.
Floor chair is also appointed using the floor control protocol when
the floor is created. Typically, only conference moderators are
allowed to use these commands.
The conference moderator can remove the floor at any time using floor
control protocol (so that the resources are no longer floor-
controlled), or change the floor chair or the floor parameters.
The floor chair just controls the access to the floor, according to
the floor policy, defined at a time when the floor is created.
4 Conference Policy Data Model
Conference policy data is relative static. It is not updated
frequently as e.g. participant list is not part of conference policy.
Users with sufficient privileges are able to manipulate conference
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policy. For example, a user with sufficient privileges may
manipulate conference's access control list by adding a user into the
ACL white list.
It is also assumed that the policy data server does not necessarily
have a clock. Therefore, conference policy data does not have any
time-related policy attributes.
5 Conference Policy Requirements
This section describes conference policy requirements.
5.1 Conference creation, termination and joining
(Requirements A1-A7 apply better to CPCP rather than to policy data)
REQ-A1: It MUST be possible to create a new conference at focus,
resulting in a URI.
REQ-A2: It MUST be possible to associate policy attributes to a
conference URI.
REQ-A3: It MUST be possible to reserve a conference URI from the
focus for future use with or without associating policy
attributes to it.
REQ-A4: It MUST be possible for an user to fetch some or all
components of conference policy from the focus (from the
conference URI), during and before joining the conference.
REQ-A5: It MUST be possible to delete the existing conference
URI and release all resources associated with it.
REQ-A6: It MUST be possible to terminate the conference instance
but keep the conference URI and all policy attributes
reserved.
REQ-A7: It SHOULD be possible to join anonymously to the
conference and still be able to send and receive data and
private 1-to-1 SIP messages anonymously.
5.2 Manipulating general conference attributes
REQ-B2: It MUST be possible to set and modify conference Subject
that can be seen e.g. in web page, SDP s line or SIP
Subject header.
REQ-B3: It MUST be possible to set, modify and delete conference
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URI display name.
REQ-B4: It MUST be possible to set, modify and delete conference
creator information (as is seen e.g. in SDP o line).
REQ-B5: It MUST be possible to set, modify and delete conference
URI link for more information (as used e.g. in SDP u line).
REQ-B6: It MUST be possible to set, modify and delete conference
host contact information (as used e.g. in SDP e and p
lines).
REQ-B7: It MUST be possible to set, modify and delete short
conference session description (as used e.g. in SDP i
line). This can be per session or per media.
REQ-B8: It MUST be possible to set, modify and delete max number
of conference participants. This defines how many users at
max can be present at the same time.
REQ-B9: It MUST be possible to set whether the conference is
public or hidden (if hidden, focus does not return
description to outsiders for OPTIONS or other requests).
REQ-B10: Conference policy MUST have an attribute that defines
whether the conference is active or inactive. (If active,
users can join etc). [This is needed because start/end
times are not used here]
REQ-B11: It MUST be possible to give the list of invited users
into the conference (dial-out case).
5.3 Authentication and Security
REQ-C1: It MUST be possible to define the authentication
mechanism, and passwords for user joins.
REQ-C2: It MUST be possible to use sips: scheme as a conference
URI.
REQ-C3: It MUST be possible to define encryption keys for media
data. [OPEN ISSUE: Does this belong to media policy?]
5.4 Application and media manipulation
REQ-D1: It MUST be possible to assign and de-assign the users
who are allowed to manipulate media policy.
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5.5 ACL manipulation
REQ-E1: It MUST be possible to add and delete users into and
from ACL white list (allowed to join) and ACL black list
(not allowed to join).
REQ-E2: ACL conflicts MUST be solved in a well-defined way (e.g.
what if user appears both in black list and in white list)
e.g. by mandating the order in which ACL definitions are
evaluated (e.g. most specific expression first).
REQ-E3: It MUST be possible to use wildcards in ACL (such as
*.company.com in white list).
REQ-E4: It MUST be possible to allow and disallow anonymous and
hidden joins to the conference.
5.6 Floor control
REQ-F1: It MUST be possible to assign and de-assign the users
who are allowed to manipulate floor policy. (Floor policy
is manipulated by the floor control protocol itself).
5.7 Inviting and ejecting users
REQ-G1: It MUST be possible to invite one or more users into the
conference (including so called "mass invitation"
operation).
REQ-G2: It MUST be possible eject one or more users from the
conference (including so called "mass ejection" operation).
5.8 User Privileges
REQ-H1: It MUST be possible to give a privilege to a user. (A
privilege may be operation, such as right to expel, right
to modify conference ACL, right to hand off all or some
privileges to another user).
REQ-H2: It MUST be possible to remove a privilege from a user.
REQ-H3: It MAY be possible to support user privilege groups
(e.g. senior-members) and to group privileges together,
such as senior-members can eject users and manipulate ACL.
REQ-H4: It MAY be possible that default privileges (e.g. only
the creator can delete conference) are defined by the
Conference Policy Control Protocol that can be changed by
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the conference policy.
REQ-H5: It MUST be possible to authorize users who have the
right to subscribe to specific events, such as ACL changes.
REQ-H6: It MAY be possible request new privileges from the
conference policy server via CPCP.
REQ-H7: It SHOULD be possible to define who is allowed to
subscribe to conference related events.
REQ It MAY be possible that default privileges are defined for
new conference, such as conference creator has all
privileges available and others do not have have any of
them.
6 Notifications and Subscriptions
New SIP event packages may be needed. For example, conference owner
(or a user with sufficient privileges) may subscribe to the
conference management event, and get notified when there is a need to
do policy manipulation, such as ACL manipulation for on-going join
attempt.
7 Possible Solutions
This document is primarily a requirements document, and does not aim
to provide a protocol or policy data format for meeting the
requirements defined here. Solutions such as SOAP, XML/RPC and ACAP
can be utilized. Moreover, the use of encoding formats such as SDP,
SDP-NG, iCal, and vCard can be investigated.
8 Open Issues
o Whether time-related policy data attributes are needed, e.g.
for conference start/end times. Even if absolute times are not
needed, it may be useful to have relative times (e.g. max time
2 hours). Conference may be created in advance, put to
inactive state and activated when needed. This needs more
thinking.
o Should conferece policy include any bandwidth related
attributes (e.g. per media, per user or per conference)?
9 Changes from previous version
CPCP requirements section [This section may be later extracted to
separate internet-draft "Requirements for policy control protocol"]
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REQ-CP-1: Protocol behaviour: CPCP protocol SHOULD be a
reliable client-server protocol. Hence, it SHOULD have a
positive response indicating that the request has been
received, or error response if an error has occurred. The
sending UA takes care of retransmission in the case of
packet loss.
REQ-CP-2: Manipulations of the policy collection MUST exhibit
the ACID property; that is, they MUST be atomic, be
consistent, durable, and operate independently.
REQ-CP-3: It MAY be possible for the client to batch multiple
operations (such as add a user to ACL black list, or remove
a user from ACL white list) into a single request that is
processed atomically.
REQ-CP-4: It MUST be possible for the server to authenticate the
client.
REQ-CP-5: It MUST be possible for the client to authenticate the
server.
REQ-CP-6: It MUST be possible for message integrity to be
ensured between the client and the server.
REQ-CP-7: It MUST be possible for privacy to be ensured between
the client and server.
10 Acknowledgements
The author would like to thank Rohan Mahy, Jonathan Rosenberg, Roni
Even, Orit Levin, Alan Johnston, Joerg Ott and others for their
comments.
11 Authors' Addresses
Petri Koskelainen
Nokia
Visiokatu 1,
33720 Tampere,
Finland
e-mail: petri.koskelainen@nokia.com
12 Normative References
[1] J. Rosenberg, "A framework for conferencing with the session
initiation protocol," internet draft, Internet Engineering Task
Force, Feb. 2003. Work in progress.
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[2] A. Johnston,O. Levin, "Session Initiation Protocol Call Control -
Conferencing for User Agents", internet draft, Internet Engineering
Task Force, Feb. 2003. Work in progress.
[3] S. Bradner, "Key words for use in rfcs to indicate requirement
levels," RFC 2119, Internet Engineering Task Force, Mar. 1997.
13 Informative References
[4] C. Bormann, D. Kutscher, J. Ott, and D. Trossen, "Simple
conference control protocol service specification," internet draft,
Internet Engineering Task Force, Mar. 2001. Work in progress.
[5] P. Koskelainen, H. Schulzrinne, and X. Wu, "Additional
requirements to conferencing," internet draft, Internet Engineering
Task Force, Apr. 2002. Work in progress.
[6] H. Schulzrinne. P. Koskelainen and X. Wu, "A sip-based conference
control framework," in NOSSDAV, (Miami, Florida), May 2002.
[7] P. Koskelainen, H. Schulzrinne, and J. Ott, "Requirements for
floor control," internet draft, Internet Engineering Task Force, Nov.
2002. Work in progress.
[8] X. Wu et al., "Use of session initiation protocol (SIP) and
simple object access protocol (SOAP) for conference floor control,"
internet draft, Internet Engineering Task Force, Jan. 2003. Work in
progress.
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Table of Contents
1 Introduction ........................................ 2
1.1 Conventions of This Document ........................ 2
2 Terminology ......................................... 2
3 Integration with Floor Control ...................... 3
4 Conference Policy Data Model ........................ 3
5 Conference Policy Requirements ...................... 4
5.1 Conference creation, termination and joining ........ 4
5.2 Manipulating general conference attributes .......... 4
5.3 Authentication and Security ......................... 5
5.4 Application and media manipulation .................. 5
5.5 ACL manipulation .................................... 6
5.6 Floor control ....................................... 6
5.7 Inviting and ejecting users ......................... 6
5.8 User Privileges ..................................... 6
6 Notifications and Subscriptions ..................... 7
7 Possible Solutions .................................. 7
8 Open Issues ......................................... 7
9 Changes from previous version ....................... 7
10 Acknowledgements .................................... 8
11 Authors' Addresses .................................. 8
12 Normative References ................................ 8
13 Informative References .............................. 9
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