XCON Working Group G. Camarillo
Internet-Draft Ericsson
Expires: January 14, 2006 J. Ott
Helsinki University of Technology
K. Drage
Lucent Technologies
July 13, 2005
The Binary Floor Control Protocol (BFCP)
draft-ietf-xcon-bfcp-05.txt
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Abstract
Floor control is a means to manage joint or exclusive access to
shared resources in a (multiparty) conferencing environment.
Thereby, floor control complements other functions -- such as
conference and media session setup, conference policy manipulation,
and media control -- that are realized by other protocols.
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This document specifies the Binary Floor Control Protocol (BFCP).
BFCP is used between floor participants and floor control servers,
and between floor chairs (i.e., moderators) and floor control
servers.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Floor Creation . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Obtaining Information to Contact a Floor Control Server . 8
3.3 Generating a Shared Secret . . . . . . . . . . . . . . . . 8
3.4 Obtaining Floor-Resource Associations . . . . . . . . . . 8
3.5 Privileges of Floor Control . . . . . . . . . . . . . . . 9
4. Overview of Operation . . . . . . . . . . . . . . . . . . . 9
4.1 Floor Participant to Floor Control Server Interface . . . 10
4.2 Floor Chair to Floor Control Server Interface . . . . . . 13
5. Packet Format . . . . . . . . . . . . . . . . . . . . . . . 14
5.1 COMMON-HEADER Format . . . . . . . . . . . . . . . . . . . 15
5.2 Attribute Format . . . . . . . . . . . . . . . . . . . . . 16
5.2.1 BENEFICIARY-ID . . . . . . . . . . . . . . . . . . . . 18
5.2.2 FLOOR-ID . . . . . . . . . . . . . . . . . . . . . . . 18
5.2.3 FLOOR-REQUEST-ID . . . . . . . . . . . . . . . . . . . 18
5.2.4 NONCE . . . . . . . . . . . . . . . . . . . . . . . . 19
5.2.5 PRIORITY . . . . . . . . . . . . . . . . . . . . . . . 19
5.2.6 REQUEST-STATUS . . . . . . . . . . . . . . . . . . . . 20
5.2.7 DIGEST . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2.8 ERROR-CODE . . . . . . . . . . . . . . . . . . . . . . 22
5.2.9 ERROR-INFO . . . . . . . . . . . . . . . . . . . . . . 24
5.2.10 PARTICIPANT-PROVIDED-INFO . . . . . . . . . . . . . 25
5.2.11 STATUS-INFO . . . . . . . . . . . . . . . . . . . . 26
5.2.12 SUPPORTED-ATTRIBUTES . . . . . . . . . . . . . . . . 26
5.2.13 SUPPORTED-PRIMITIVES . . . . . . . . . . . . . . . . 27
5.2.14 USER-DISPLAY-NAME . . . . . . . . . . . . . . . . . 28
5.2.15 USER-URI . . . . . . . . . . . . . . . . . . . . . . 28
5.2.16 BENEFICIARY-INFORMATION . . . . . . . . . . . . . . 29
5.2.17 FLOOR-REQUEST-INFORMATION . . . . . . . . . . . . . 30
5.2.18 REQUESTED-BY-INFORMATION . . . . . . . . . . . . . . 30
5.3 Message Format . . . . . . . . . . . . . . . . . . . . . . 31
5.3.1 FloorRequest . . . . . . . . . . . . . . . . . . . . . 31
5.3.2 FloorRelease . . . . . . . . . . . . . . . . . . . . . 32
5.3.3 FloorRequestQuery . . . . . . . . . . . . . . . . . . 32
5.3.4 FloorRequestStatus . . . . . . . . . . . . . . . . . . 33
5.3.5 UserQuery . . . . . . . . . . . . . . . . . . . . . . 33
5.3.6 UserStatus . . . . . . . . . . . . . . . . . . . . . . 33
5.3.7 FloorQuery . . . . . . . . . . . . . . . . . . . . . . 34
5.3.8 FloorStatus . . . . . . . . . . . . . . . . . . . . . 34
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5.3.9 ChairAction . . . . . . . . . . . . . . . . . . . . . 34
5.3.10 ChairActionAck . . . . . . . . . . . . . . . . . . . 35
5.3.11 Hello . . . . . . . . . . . . . . . . . . . . . . . 35
5.3.12 HelloAck . . . . . . . . . . . . . . . . . . . . . . 35
5.3.13 Error . . . . . . . . . . . . . . . . . . . . . . . 36
6. Transport . . . . . . . . . . . . . . . . . . . . . . . . . 36
7. Lower-Layer Security . . . . . . . . . . . . . . . . . . . . 37
8. Protocol Transactions . . . . . . . . . . . . . . . . . . . 37
8.1 Client Behavior . . . . . . . . . . . . . . . . . . . . . 38
8.2 Server Behavior . . . . . . . . . . . . . . . . . . . . . 38
9. Authentication and Authorization . . . . . . . . . . . . . . 38
9.1 TLS-based Mutual Authentication . . . . . . . . . . . . . 38
9.2 Digest-based Client Authentication . . . . . . . . . . . . 39
9.2.1 Client Behavior . . . . . . . . . . . . . . . . . . . 39
9.2.2 Floor Control Server Behavior . . . . . . . . . . . . 41
10. Floor Participant Operations . . . . . . . . . . . . . . . . 42
10.1 Requesting a Floor . . . . . . . . . . . . . . . . . . . 42
10.1.1 Sending a FloorRequest Message . . . . . . . . . . . 42
10.1.2 Receiving a Response . . . . . . . . . . . . . . . . 43
10.2 Cancelling a Floor Request and Releasing a Floor . . . . 44
10.2.1 Sending a FloorRelease Message . . . . . . . . . . . 44
10.2.2 Receiving a Response . . . . . . . . . . . . . . . . 45
11. Chair Operations . . . . . . . . . . . . . . . . . . . . . . 45
11.1 Sending a ChairAction Message . . . . . . . . . . . . . 45
11.2 Receiving a Response . . . . . . . . . . . . . . . . . . 46
12. General Client Operations . . . . . . . . . . . . . . . . . 47
12.1 Requesting Information about Floors . . . . . . . . . . 47
12.1.1 Sending a FloorQuery Message . . . . . . . . . . . . 47
12.1.2 Receiving a Response . . . . . . . . . . . . . . . . 47
12.2 Requesting Information about Floor Requests . . . . . . 48
12.2.1 Sending a FloorRequestQuery Message . . . . . . . . 49
12.2.2 Receiving a Response . . . . . . . . . . . . . . . . 49
12.3 Requesting Information about a User . . . . . . . . . . 49
12.3.1 Sending a UserQuery Message . . . . . . . . . . . . 50
12.3.2 Receiving a Response . . . . . . . . . . . . . . . . 50
12.4 Obtaining the Capabilities of a Floor Control Server . . 50
12.4.1 Sending a Hello Message . . . . . . . . . . . . . . 51
12.4.2 Receiving Responses . . . . . . . . . . . . . . . . 51
13. Floor Control Server Operations . . . . . . . . . . . . . . 51
13.1 Reception of a FloorRequest Message . . . . . . . . . . 52
13.1.1 Generating the First FloorRequestStatus Message . . 52
13.1.2 Generation of Subsequent FloorRequestStatus
Messages . . . . . . . . . . . . . . . . . . . . . . 53
13.2 Reception of a FloorRequestQuery Message . . . . . . . . 54
13.3 Reception of a UserQuery Message . . . . . . . . . . . . 55
13.4 Reception of a FloorRelease Message . . . . . . . . . . 57
13.5 Reception of a FloorQuery Message . . . . . . . . . . . 58
13.5.1 Generation of the First FloorStatus Message . . . . 58
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13.5.2 Generation of Subsequent FloorStatus Messages . . . 60
13.6 Reception of a ChairAction Message . . . . . . . . . . . 60
13.7 Reception of a Hello Message . . . . . . . . . . . . . . 61
13.8 Error Message Generation . . . . . . . . . . . . . . . . 61
14. Security Considerations . . . . . . . . . . . . . . . . . . 62
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . 63
15.1 Attribute Subregistry . . . . . . . . . . . . . . . . . 63
15.2 Primitive Subregistry . . . . . . . . . . . . . . . . . 64
15.3 Request Status Subregistry . . . . . . . . . . . . . . . 65
15.4 Error Code Subregistry . . . . . . . . . . . . . . . . . 66
15.5 Digest Algorithm Subregistry . . . . . . . . . . . . . . 67
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 67
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 67
17.1 Normative References . . . . . . . . . . . . . . . . . . 67
17.2 Informational References . . . . . . . . . . . . . . . . 68
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 68
Intellectual Property and Copyright Statements . . . . . . . 70
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1. Introduction
Within a conference, some applications need to manage the access to a
set of shared resources, such as the right to send media over a
particular media stream. Floor control enables such applications to
provide users with coordinated (shared or exclusive) access to these
resources.
The Requirements for Floor Control Protocol [10] list a set of
requirements that need to be met by floor control protocols. The
Binary Floor Control Protocol (BFCP), which is specified in this
document, meets these requirements.
In addition, BFCP has been designed so that it can be used in low-
bandwidth environments. The binary encoding used by BFCP achieves a
small message size (when message signatures are not used) that keeps
the time it takes to transmit delay-sensitive BFCP messages at
minimum. Delay-sensitive BFCP messages include FloorRequest,
FloorRelease, FloorRequestStatus, and ChairAction. It is expected
that future extensions to these messages do not increase the size of
these messages in a significant way.
The remainder of this document is organized as follows: Section 2
defines the terminology used throughout this document, Section 3
discusses the scope of BFCP (i.e., which tasks fall within the scope
of BFCP and which ones are performed using different mechanisms),
Section 4 provides a non-normative overview of BFCP operation, and
subsequent sections provide the normative specification of BFCP.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [2] and indicate requirement levels for
compliant implementations.
Media Participant: An entity that has access to the media resources
of a conference (e.g., it can receive a media stream). In floor-
controlled conferences, a given media participant is typically co-
located with a floor participant, but does not need to. Third-party
floor requests consist of having a floor participant request a floor
for a media participant when they are not colocated. The protocol
between a floor participant and a media participant (that are not
colocated) is outside the scope of this document.
Client: a floor participant or a floor chair that communicate with a
floor control server using BFCP.
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Floor: A permission to temporarily access or manipulate a specific
shared resource or set of resources.
Floor Chair: A logical entity that manages one floor (grants, denies,
or revokes a floor). An entity that assumes the logical role of a
floor chair for a given transaction may assume a different role
(e.g., floor participant) for a different transaction. The roles of
floor chair and floor participant are defined on a transaction-by-
transaction basis. BFCP transactions are defined in Section 8.
Floor Control: A mechanism that enables applications or users to gain
safe and mutually exclusive or non-exclusive input access to the
shared object or resource.
Floor Control Server: A logical entity that maintains the state of
the floor(s) including which floors exists, who the floor chairs are,
who holds a floor, etc. Requests to manipulate a floor are directed
at the floor control server. The floor control server of a
conference may perform other logical roles (e.g., floor participant)
in another conference.
Floor Participant: A logical entity that requests floors, and
possibly information about them, from a floor control server. An
entity that assumes the logical role of a floor participant for a
given transaction may assume a different role (e.g., a floor chair)
for a different transaction. The roles of floor participant and
floor chair are defined on a transaction-by-transaction basis. BFCP
transactions are defined in Section 8. In floor-controlled
conferences, a given floor participant is typically co-located with a
media participant, but does not need to. Third-party floor requests
consist of having a floor participant request a floor for a media
participant when they are not co-located.
Participant: An entity that acts as a floor participant, as a media
participant, or as both.
3. Scope
As stated earlier, BFCP is a protocol to coordinate access to shared
resources in a conference following the requirements defined in [10].
Floor control complements other functions defined in the XCON
conferencing framework [12] and is compatible with the SIPPING
conferencing framework [11]. The floor control protocol BFCP defined
in this document only specifies a means to arbitrate access to
floors. The rules and constraints for floor arbitration and the
results of floor assignments are outside the scope of this document
and defined by other protocols [12].
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Figure 1 shows the tasks that BFCP can perform.
+---------+
| Floor |
| Chair |
| |
+---------+
^ |
| |
Notification | | Decision
| |
| |
Floor | v
+-------------+ Request +---------+ +-------------+
| Floor |----------->| Floor | Notification | Floor |
| Participant | | Control |------------->| Participant |
| |<-----------| Server | | |
+-------------+ Granted or +---------+ +-------------+
Denied
Figure 1: Functionality provided by BFCP
BFCP provides a means:
o for floor participants to send floor requests to floor control
servers.
o for floor control servers to grant or deny requests to access a
given resource from floor participants.
o for floor chairs to send floor control servers decisions regarding
floor requests.
o for floor control servers to keep floor participants and floor
chairs informed about the status of a given floor or a given floor
request.
Even though tasks that do not belong to the previous list are outside
the scope of BFCP, some of these out-of-scope tasks relate to floor
control and are essential to create floors and to establish BFCP
connections between different entities. In the following
subsections, we discuss some of these tasks and mechanisms to perform
them.
3.1 Floor Creation
The association of a given floor with a resource or a set of
resources (e.g., media streams) is out of the scope of BFCP as
described in [12]. Floor creation and termination are also outside
the scope of BFCP; these aspects are handled using the conference
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control protocol for manipulating the conference object.
Consequently, the floor control server needs to stay up to date on
changes to the conference object (e.g., when a new floor is created).
3.2 Obtaining Information to Contact a Floor Control Server
A client needs a set of data in order to establish a BFCP connection
to a floor control server. These data include the transport address
of the server, the conference identifier, and a user identifier.
Clients can obtain this information in different ways. One is to use
an offer/answer [9] exchange, which is described in [13]. Other
mechanisms are also described in the XCON framework (and other
related documents).
3.3 Generating a Shared Secret
Authentication in BFCP is based on a shared secret between the client
and the floor control server. So, there is a need for a mechanism to
generate such a shared secret. However, such mechanism is outside
the scope of BFCP.
Shared secrets can also be generated and exchanged using out-of-band
means. For example, when the floor participant or the floor chair
obtains the information needed to contact the BFCP floor control
server over a secure channel (e.g., an offer/answer [9] exchange
using SIP [8] protected using S/MIME), they can get the shared secret
using the same channel.
3.4 Obtaining Floor-Resource Associations
Floors are associated with resources. For example, a floor that
controls who talks at a given time has a particular audio stream as
its associated resource. Associations between floors and resources
are part of the conference object.
Floor participants and floor chairs need to know which resources are
associated with which floors. They can obtain this information using
different mechanisms, such as an offer/answer [9] exchange. How to
use an offer/answer exchange to obtain these associations is
described in [13].
Note that floor participants perform offer/answer exchanges with
the SIP Focus of the conference. So, the SIP Focus needs to
obtain information about associations between floors and resources
in order to be able to provide this information to a floor
participant in an offer/answer exchange.
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Other mechanisms for obtaining this information, including discussion
of how the information is made available to a (SIP) Focus, are
described in the XCON framework (and other related documents).
3.5 Privileges of Floor Control
A participant whose floor request is granted has the right to use (in
a certain way) the resource or resources associated with the floor
that was requested. For example, the participant may have the right
to send media over a particular audio stream.
Nevertheless, holding a floor does not imply that others will not be
able to use its associated resources at the same time, even if they
do not have the right to do so. Determination of which media
participants can actually use the resources in the conference is
discussed in the XCON Framework.
4. Overview of Operation
This section provides a non-normative description of BFCP operations.
Section 4.1 describes the interface between floor participants and
floor control servers and Section 4.2 describes the interface between
floor chairs and floor control servers
BFCP messages, which use a TLV (Type-Length-Value) binary encoding,
consist of a common header followed by a set of attributes. The
common header contains, among other information, a 32-bit conference
identifier. Floor participants, media participants, and floor chairs
are identified by 16-bit user identifiers.
Participant authentication in BFCP is based on shared secrets. The
floor control server of a conference shares a secret with each of the
participants in the conference and can request them to sign their
messages using that shared secret.
BFCP supports nested attributes (i.e., attributes that contain
attributes). These are referred to as grouped attributes.
There are two types of transactions in BFCP: client-initiated
transactions and server-initiated transactions. Client-initiated
transactions consist of a message from a client to the floor control
server and a response from the floor control server to the client.
Both messages can be related because they carry the same Transaction
ID value in their common headers. Server-initiated transactions
consist of a single message, whose Transaction ID is 0, from the
floor control server to a client.
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4.1 Floor Participant to Floor Control Server Interface
Floor participants request a floor by sending a FloorRequest message
to the floor control server. BFCP supports third-party floor
requests. That is, the floor participant sending the floor request
need not be co-located with the media participant that will get the
floor once the floor request is granted. FloorRequest messages carry
the identity of the requester in the User ID field of the common
header, and the identity of the beneficiary of the floor (in third
party floor requests) in a BENEFICIARY-ID attribute.
Third party floor requests can be sent, for example, by floor
participants that have a BFCP connection to the floor control
server but that are not media participants (i.e., they do not
handle any media).
FloorRequest messages identify the floor or floors being requested by
carrying their 16-bit floor identifiers in FLOOR-ID attributes. If a
FloorRequest message carries more than one floor identifier, the
floor control server treats all the floor requests as an atomic
package. That is, the floor control server either grants or denies
all the floors in the FloorRequest message.
Floor control servers respond to FloorRequest messages with
FloorRequestStatus messages, which provide information about the
status of the floor request. The first FloorRequestStatus message is
the response to the FloorRequest message from the client, and
therefore has the same Transaction ID as the FloorRequest.
Additionally, the first FloorRequestStatus message carries the Floor
Request ID in a FLOOR-REQUEST-INFORMATION attribute. Subsequent
FloorRequestStatus messages related to the same floor request will
carry the same Floor Request ID. This way, the floor participant can
associate them with the appropriate floor request.
Messages from the floor participant related to a particular floor
request also use the same Floor Request ID as the first
FloorRequestStatus Message from the floor control server.
Figure 2 shows how a floor participant requests a floor, obtains it,
and, at a later time, releases it. This figure illustrates the use,
among other things, of the Transaction ID and the FLOOR-REQUEST-ID
attribute.
Floor Participant Floor Control
Server
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|(1) FloorRequest |
|Transaction ID: 123 |
|User ID: 234 |
|FLOOR-ID: 543 |
|---------------------------------------------->|
| |
|(2) FloorRequestStatus |
|Transaction ID: 123 |
|User ID: 234 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 789 |
| FLOOR-ID: 543 |
| REQUEST-STATUS: Pending |
|<----------------------------------------------|
| |
|(3) FloorRequestStatus |
|Transaction ID: 0 |
|User ID: 234 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 789 |
| FLOOR-ID: 543 |
| REQUEST-STATUS: Accepted (1st in Queue) |
|<----------------------------------------------|
| |
|(4) FloorRequestStatus |
|Transaction ID: 0 |
|User ID: 234 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 789 |
| FLOOR-ID: 543 |
| REQUEST-STATUS: Granted |
|<----------------------------------------------|
| |
|(5) FloorRelease |
|Transaction ID: 154 |
|User ID: 234 |
|FLOOR-REQUEST-ID: 789 |
|---------------------------------------------->|
| |
|(6) FloorRequestStatus |
|Transaction ID: 154 |
|User ID: 234 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 789 |
| FLOOR-ID: 543 |
| REQUEST-STATUS: Released |
|<----------------------------------------------|
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Figure 2: Requesting and releasing a floor
Figure 3 shows how a floor participant requests to be informed on the
status of a floor. The first FloorStatus message from the floor
control server is the response to the FloorQuery message, and as
such, has the same Transaction ID as the FloorQuery message.
Subsequent FloorStatus messages consist of server-initiated
transactions, and therefore their Transaction ID is 0. FloorStatus
message (2) indicates that there are currently two floor requests for
the floor whose Floor ID is 543. FloorStatus message (3) indicates
that the floor requests with Floor Request ID 764 has been granted,
while the floor request with Floor Request ID 635 is the first in the
queue. FloorStatus message (4) indicates that the floor request with
Floor Request ID 635 has been granted.
Floor Participant Floor Control
Server
|(1) FloorQuery |
|Transaction ID: 257 |
|User ID: 234 |
|FLOOR-ID: 543 |
|---------------------------------------------->|
| |
|(2) FloorStatus |
|Transaction ID: 257 |
|User ID: 234 |
|FLOOR-ID:543 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 764 |
| FLOOR-ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 124 |
| REQUEST-STATUS: Accepted (1st in Queue) |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 635 |
| FLOOR-ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 154 |
| REQUEST-STATUS: Accepted (2nd in Queue) |
|<----------------------------------------------|
| |
|(3) FloorStatus |
|Transaction ID: 0 |
|User ID: 234 |
|FLOOR-ID:543 |
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|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 764 |
| FLOOR-ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 124 |
| REQUEST-STATUS: Granted |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 635 |
| FLOOR-ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 154 |
| REQUEST-STATUS: Accepted (1st in Queue) |
|<----------------------------------------------|
| |
|(4) FloorStatus |
|Transaction ID: 0 |
|User ID: 234 |
|FLOOR-ID:543 |
|FLOOR-REQUEST-INFORMATION |
| Floor Request ID: 635 |
| FLOOR-ID: 543 |
| BENEFICIARY-INFORMATION |
| Beneficiary ID: 154 |
| REQUEST-STATUS: Granted |
|<----------------------------------------------|
Figure 3: Obtaining status information about a floor
FloorStatus messages contain information about the floor requests
they carry. For example, FloorStatus message (4) indicates that the
floor request with Floor Request ID 635 has as the beneficiary (i.e.,
the participant that holds the floor when a particular floor request
is granted) the participant whose User ID is 154. The floor request
applies only to the floor whose Floor ID is 543. That is, this is
not a multi-floor floor request.
A multi-floor floor request applies to more than one floor (e.g.,
a participant wants to be able to speak and write on the
whiteboard at the same time). The floor control server treats a
multi-floor floor request as an atomic package. That is, the
floor control server either grants the request for all floors or
denies the request for all the floors.
4.2 Floor Chair to Floor Control Server Interface
Figure 4 shows a floor chair instructing a floor control server to
grant a floor. Note, however, that although the floor control server
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needs to take into consideration the instructions received in
ChairAction messages (e.g., granting a floor), it does not
necessarily need to perform them exactly as requested by the floor
chair. The operation that the floor control server performs depends
on the ChairAction message and on the internal state of the floor
control server.
For example, a floor chair may send a ChairAction message granting a
floor which was requested as part of an atomic floor request
operation that involved several floors. Even if the chair
responsible for one of the floors instructs the floor control server
to grant the floor, the floor control server will not grant it until
the chairs responsible for the other floors agree to grant them as
well. In another example, a floor chair may instruct the floor
control server to grant a floor to a participant. The floor control
server needs to revoke the floor from its current holder before
granting it to the new participant.
So, the floor control server is ultimately responsible to keep a
coherent floor state using instructions from floor chairs as input to
this state.
Floor Chair Floor Control
Server
|(1) ChairAction |
|Transaction ID: 769 |
|User ID: 357 |
|FLOOR-ID: 543 |
|FLOOR-REQUEST-ID: 635 |
|REQUEST-STATUS: Granted |
|---------------------------------------------->|
| |
|(2) ChairActionAck |
|Transaction ID: 769 |
|User ID: 357 |
|<----------------------------------------------|
Figure 4: Chair instructing the floor control server
5. Packet Format
BFCP packets consist of a 12-byte common header followed by
attributes. All the protocol values MUST be sent in network byte
order.
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5.1 COMMON-HEADER Format
The following is format of the common header.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ver |Reserved | Primitive | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Conference ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transaction ID | User ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: COMMON-HEADER format
Ver: the 3-bit version field MUST be set to 1 to indicate this
version of BFCP.
Reserved: at this point, the 5 bits in the reserved field SHOULD be
set to zero by the sender of the message and MUST be ignored by the
receiver.
Primitive: this 8-bit field identifies the main purpose of the
message. The following primitive values are defined:
+-------+--------------------+-----------------------+
| Value | Primitive | Direction |
+-------+--------------------+-----------------------+
| 1 | FloorRequest | P -> S |
| 2 | FloorRelease | P -> S |
| 3 | FloorRequestQuery | P -> S ; Ch -> S |
| 4 | FloorRequestStatus | P <- S ; Ch <- S |
| 5 | UserQuery | P -> S ; Ch -> S |
| 6 | UserStatus | P <- S ; Ch <- S |
| 7 | FloorQuery | P -> S ; Ch -> S |
| 8 | FloorStatus | P <- S ; Ch <- S |
| 9 | ChairAction | Ch -> S |
| 10 | ChairActionAck | Ch <- S |
| 11 | Hello | P -> S ; Ch -> S |
| 12 | HelloAck | P <- S ; Ch <- S |
| 13 | Error | P <- S ; Ch <- S |
+-------+--------------------+-----------------------+
S: Floor Control Server
P: Floor Participant
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Ch: Floor Chair
Table 1: BFCP primitives
Payload Length: this 16-bit field contains length of the message in
4-byte units excluding the common header.
Conference ID: this 32-bit field identifies the conference the
message belongs to.
Transaction ID: this field contains a 16-bit value that allows users
to match a given message with its response. The value of the
Transaction ID in server-initiated transactions is 0 (see Section 8).
User ID: this field contains a 16-bit value that uniquely identifies
a participant within a conference.
The identity used by a participant in BFCP, which is carried in
the User ID field, is generally mapped to the identity used by the
same participant in the session establishment protocol (e.g., in
SIP). The way this mapping is performed is outside the scope of
this specification.
5.2 Attribute Format
BFCP attributes are encoded in TLV (Type-Length-Value) format.
Attributes are 32-bit aligned.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |M| Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
/ Attribute Contents /
/ /
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Attribute format
Type: this 7-bit field contains the type of the attribute. Each
attribute, identified by its type, has a particular format. The
attribute formats defined are:
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Unsigned16: the contents of the attribute consist of a 16-bit
unsigned integer.
OctetString16: the contents of the attribute consist of 16 bits of
arbitrary data.
OctetString: the contents of the attribute consist of arbitrary
data of variable length.
Grouped: the contents of the attribute consist of a sequence of
attributes.
Note that extension attributes defined in the future may define new
attribute formats.
The following attribute types are defined:
+------+---------------------------+---------------+
| Type | Attribute | Format |
+------+---------------------------+---------------+
| 1 | BENEFICIARY-ID | Unsigned16 |
| 2 | FLOOR-ID | Unsigned16 |
| 3 | FLOOR-REQUEST-ID | Unsigned16 |
| 4 | NONCE | Unsigned16 |
| 5 | PRIORITY | OctetString16 |
| 6 | REQUEST-STATUS | OctetString16 |
| 7 | DIGEST | OctetString |
| 8 | ERROR-CODE | OctetString |
| 9 | ERROR-INFO | OctetString |
| 10 | PARTICIPANT-PROVIDED-INFO | OctetString |
| 11 | STATUS-INFO | OctetString |
| 12 | SUPPORTED-ATTRIBUTES | OctetString |
| 13 | SUPPORTED-PRIMITIVES | OctetString |
| 14 | USER-DISPLAY-NAME | OctetString |
| 15 | USER-URI | OctetString |
| 16 | BENEFICIARY-INFORMATION | Grouped |
| 17 | FLOOR-REQUEST-INFORMATION | Grouped |
| 18 | REQUESTED-BY-INFORMATION | Grouped |
+------+---------------------------+---------------+
Table 2: BFCP attributes
M: the 'M' bit, known as the Mandatory bit, indicates whether support
of the attribute is required. If an unrecognized attribute with the
'M' bit set is received, the message is rejected.
Length: this 8-bit field contains the length of the attribute in
bytes, excluding any padding defined for specific attributes. The
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Type, 'M' bit, and Length fields are included. The Length in grouped
attributes is the length of the grouped attribute itself (including
Type, 'M' bit, and Length fields) plus the total length (including
padding) of all the included attributes.
Attribute Contents: the contents of the different attributes are
defined in the following sections.
5.2.1 BENEFICIARY-ID
The following is the format of the BENEFICIARY-ID attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1|M|0 0 0 0 0 1 0 0| Beneficiary ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: BENEFICIARY-ID format
Beneficiary ID: this field contains a 16-bit value that uniquely
identifies a user within a conference.
Note that although the formats of the Beneficiary ID and of the User
ID field in the common header are similar, their semantics are
different. The Beneficiary ID is used in third-party floor requests
and to request information about a particular participant.
5.2.2 FLOOR-ID
The following is the format of the FLOOR-ID attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0|M|0 0 0 0 0 1 0 0| Floor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: FLOOR-ID format
Floor ID: this field contains a 16-bit value that uniquely identifies
a floor within a conference.
5.2.3 FLOOR-REQUEST-ID
The following is the format of the FLOOR-REQUEST-ID attribute.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 1|M|0 0 0 0 0 1 0 0| Floor Request ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: FLOOR-REQUEST-ID format
Floor Request ID: this field contains a 16-bit value that identifies
a floor request at the floor control server.
5.2.4 NONCE
The following is the format of the NONCE attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 1 0 0|M|0 0 0 0 0 1 0 0| Nonce Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: NONCE format
Nonce Value: this 16-bit field contains a nonce.
5.2.5 PRIORITY
The following is the format of the PRIORITY attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 1 0 1|M|0 0 0 0 0 1 0 0|Prio | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: PRIORITY format
Prio: this field contains a 3-bit priority value as shown in Table 3.
Senders SHOULD NOT use values higher than 4 in this field. Receivers
MUST treat values higher than 4 as if the value received had been 4
(Highest). The default priority value when the PRIORITY attribute is
missing is 2 (Normal).
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+-------+----------+
| Value | Priority |
+-------+----------+
| 0 | Lowest |
| 1 | Low |
| 2 | Normal |
| 3 | High |
| 4 | Highest |
+-------+----------+
Table 3: Priority values
Reserved: at this point, the 13 bits in the reserved field SHOULD be
set to zero by the sender of the message and MUST be ignored by the
receiver.
5.2.6 REQUEST-STATUS
The following is the format of the REQUEST-STATUS attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 1 1 0|M|0 0 0 0 0 1 0 0|Request Status |Queue Position |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: REQUEST-STATUS format
Request Status: this 8-bit field contains the status of the request,
as described in the following table.
+-------+-----------+
| Value | Status |
+-------+-----------+
| 1 | Pending |
| 2 | Accepted |
| 3 | Granted |
| 4 | Denied |
| 5 | Cancelled |
| 6 | Released |
| 7 | Revoked |
+-------+-----------+
Table 4: Request Status values
Queue Position: this 8-bit field contains, when applicable, the
position of the floor request in the floor request queue at the
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server. If the Request Status value is different from Accepted, the
floor control server does not implement a floor request queue, or the
floor control server does not want to provide the client with this
information, all the bits of this field SHOULD be set to zero.
A floor request is in Pending state if the floor control server needs
to contact a floor chair in order to accept the floor request, but
has not done it yet. Once the floor control chair accepts the floor
request, the floor request is moved to the Accepted state.
5.2.7 DIGEST
The following is the format of the DIGEST attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 1 1 1|M|0 0 0 1 1 0 0 0| Algorithm | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+ +
| |
+ Digest +
| |
+ +
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: DIGEST format
Algorithm: this 8-bit field contains the identifier of the algorithm
used to calculate the keyed digest. The following are the algorithm
identifiers defined:
+------------+-----------+---------------+--------------+
| Identifier | Algorithm | Digest Length | Reference |
+------------+-----------+---------------+--------------+
| 0 | HMAC-SHA1 | 20 bytes | RFC 2104 [1] |
+------------+-----------+---------------+--------------+
Table 5: Digest algorithms
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The text used as input to the digest algorithm is the BFCP
message, including the common header, up to and including the
attribute preceding the DIGEST attribute. Depending on the
algorithm, this text may need to be padded with zeroes. When
HMAC-SHA1 is used, the input text needs to be padded so as to be a
multiple of 64 bytes.
The key used as input to the keyed digest is the secret shared
between the server and the user identified by the User ID in the
common header of the message.
Digest: this field contains a keyed digest of the BFCP message. Its
calculation is described in Section 9.
Padding: padding added so that the contents of the DIGEST attribute
is 32-bit aligned. The Padding bits SHOULD be set to zero by the
sender and MUST be ignored by the receiver.
5.2.8 ERROR-CODE
The following is the format of the ERROR-CODE attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 0 0|M| Length | Error Code | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| Error Specific Details |
/ /
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: ERROR-CODE format
Error Code: this 8-bit field contains an error code from the
following table.
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+---------------------------------+---------------------------------+
| Value | Meaning |
+---------------------------------+---------------------------------+
| 1 | Conference does not Exist |
| 2 | User does not Exist |
| 3 | DIGEST Attribute Required |
| 4 | Invalid Nonce |
| 5 | Authentication Failed |
| 6 | Unknown Primitive |
| 7 | Unknown Mandatory Attribute |
| 8 | Unauthorized Operation |
| 9 | Invalid Floor ID |
| 10 | Floor Request ID Does Not Exist |
| 11 | You have Already Reached the |
| | Maximum Number of Ongoing Floor |
| | Requests for this Floor |
+---------------------------------+---------------------------------+
Table 6: Error Code meaning
Error Specific Details: Present only for certain Error Codes. In
this document, only for Error Code 3 (DIGEST Attribute Needed) and
Error Code 7 (Unknown Mandatory Attribute). See Section 5.2.8.1 and
Section 5.2.8.2 for their respective definitions.
Padding: one, two, or three bytes of padding added so that the
contents of the ERROR-CODE attribute is 32-bit aligned. If the
attribute is already 32-bit aligned, no padding is needed.
The Padding bits SHOULD be set to zero by the sender and MUST be
ignored by the receiver.
5.2.8.1 Error Specific Details for Error Code 3
The following is the format of the Error Specific Details field for
Error Code 3.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm ID | Algorithm ID | Algorithm ID | Algorithm ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Algorithm ID | Algorithm ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm ID | Algorithm ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: Digest algorithms format
Algorithm ID: these 8-bit fields contain the identifiers of the
digest algorithms supported by the floor control server in order of
preference (i.e., the first algorithm is the most preferred).
5.2.8.2 Error Specific Details for Error Code 7
The following is the format of the Error Specific Details field for
Error Code 7.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unknown Type|R| Unknown Type|R| Unknown Type|R| Unknown Type|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Unknown Type|R| Unknown Type|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unknown Type|R| Unknown Type|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: Unknown attributes format
Unknown Type: these 7-bit fields contain the Types of the attributes
(which were present in the message that triggered the Error message)
that were unknown to the receiver
R: at this point, this bit is reserved. It SHOULD be set to zero by
the sender of the message and MUST be ignored by the receiver.
5.2.9 ERROR-INFO
The following is the format of the ERROR-INFO attribute.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 0 1|M| Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
/ Text /
/ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: ERROR-INFO format
Text: this field contains UTF-8 [7] encoded text.
In some situations, the contents of the Text field may be generated
by an automaton. If such automaton has information about the
preferred language of the receiver of a particular ERROR-INFO
attribute, it MAY use this language to generate the Text field.
Padding: one, two, or three bytes of padding added so that the
contents of the ERROR-INFO attribute is 32-bit aligned. The Padding
bits SHOULD be set to zero by the sender and MUST be ignored by the
receiver. If the attribute is already 32-bit aligned, no padding is
needed.
5.2.10 PARTICIPANT-PROVIDED-INFO
The following is the format of the PARTICIPANT-PROVIDED-INFO
attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 1 0|M| Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
/ Text /
/ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: PARTICIPANT-PROVIDED-INFO format
Text: this field contains UTF-8 [7] encoded text.
Padding: one, two, or three bytes of padding added so that the
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contents of the PARTICIPANT-PROVIDED-INFO attribute is 32-bit
aligned. The Padding bits SHOULD be set to zero by the sender and
MUST be ignored by the receiver. If the attribute is already 32-bit
aligned, no padding is needed.
5.2.11 STATUS-INFO
The following is the format of the STATUS-INFO attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 1 1|M| Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
/ Text /
/ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 19: STATUS-INFO format
Text: this field contains UTF-8 [7] encoded text.
In some situations, the contents of the Text field may be generated
by an automaton. If such automaton has information about the
preferred language of the receiver of a particular STATUS-INFO
attribute, it MAY use this language to generate the Text field.
Padding: one, two, or three bytes of padding added so that the
contents of the STATUS-INFO attribute is 32-bit aligned. The Padding
bits SHOULD be set to zero by the sender and MUST be ignored by the
receiver. If the attribute is already 32-bit aligned, no padding is
needed.
5.2.12 SUPPORTED-ATTRIBUTES
The following is the format of the SUPPORTED-ATTRIBUTES attribute.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 1 0 0|M| Length | Supported Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Supported Attribute | Supported Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ /
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 20: SUPPORTED-ATTRIBUTES format
Supported Attribute: these fields contain the Types of the attributes
that are supported by the floor control server.
Padding: two bytes of padding added so that the contents of the
SUPPORTED-ATTRIBUTES attribute is 32-bit aligned. If the attribute
is already 32-bit aligned, no padding is needed.
The Padding bits SHOULD be set to zero by the sender and MUST be
ignored by the receiver.
5.2.13 SUPPORTED-PRIMITIVES
The following is the format of the SUPPORTED-PRIMITIVES attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 1 0 1|M| Length | Primitive | Primitive |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Primitive | Primitive | Primitive | Primitive |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ /
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 21: SUPPORTED-PRIMITIVES format
Primitive: these fields contain the types of the BFCP messages that
are supported by the floor control server. See Table 1 for the list
of BFCP primitives.
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Padding: one, two, or three bytes of padding added so that the
contents of the SUPPORTED-PRIMITIVES attribute is 32-bit aligned. If
the attribute is already 32-bit aligned, no padding is needed.
The Padding bits SHOULD be set to zero by the sender and MUST be
ignored by the receiver.
5.2.14 USER-DISPLAY-NAME
The following is the format of the USER-DISPLAY-NAME attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 1 1 0|M| Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
/ Text /
/ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 22: USER-DISPLAY-NAME format
Text: this field contains the UTF-8 encoded name of the user.
Padding: one, two, or three bytes of padding added so that the
contents of the USER-DISPLAY-NAME attribute is 32-bit aligned. The
Padding bits SHOULD be set to zero by the sender and MUST be ignored
by the receiver. If the attribute is already 32-bit aligned, no
padding is needed.
5.2.15 USER-URI
The following is the format of the USER-URI attribute.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 1 1 1|M| Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
/ Text /
/ +-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 23: USER-URI format
Text: this field contains the UTF-8 encoded URI of the user.
Padding: one, two, or three bytes of padding added so that the
contents of the USER-URI attribute is 32-bit aligned. The Padding
bits SHOULD be set to zero by the sender and MUST be ignored by the
receiver. If the attribute is already 32-bit aligned, no padding is
needed.
5.2.16 BENEFICIARY-INFORMATION
The BENEFICIARY-INFORMATION attribute is a grouped attribute that
consists of a header, which is referred to as BENEFICIARY-
INFORMATION-HEADER, followed by a sequence of attributes. The
following is the format of the BENEFICIARY-INFORMATION-HEADER:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 0 0 0 0|M| Length | Beneficiary ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 24: BENEFICIARY-INFORMATION-HEADER format
Beneficiary ID: this field contains a 16-bit value that uniquely
identifies a user within a conference.
The following is the ABNF (Augmented Backus-Naur Form) [3] of the
BENEFICIARY-INFORMATION grouped attribute. (EXTENSION-ATTRIBUTE
refers to extension attributes that may be defined in the future.)
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BENEFICIARY-INFORMATION = (BENEFICIARY-INFORMATION-HEADER)
[USER-DISPLAY-NAME]
[USER-URI]
*[EXTENSION-ATTRIBUTE]
Figure 25: BENEFICIARY-INFORMATION format
5.2.17 FLOOR-REQUEST-INFORMATION
The FLOOR-REQUEST-INFORMATION attribute is a grouped attribute that
consists of a header, which is referred to as FLOOR-REQUEST-
INFORMATION-HEADER, followed by a sequence of attributes. The
following is the format of the FLOOR-REQUEST-INFORMATION-HEADER:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 0 0 0 1|M| Length | Floor Request ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 26: FLOOR-REQUEST-INFORMATION-HEADER format
Floor Request ID: this field contains a 16-bit value that identifies
a floor request at the floor control server.
The following is the ABNF of the FLOOR-REQUEST-INFORMATION grouped
attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that
may be defined in the future.)
FLOOR-REQUEST-INFORMATION = (FLOOR-REQUEST-INFORMATION-HEADER)
(REQUEST-STATUS)
1*(FLOOR-ID)
[BENEFICIARY-INFORMATION]
[REQUESTED-BY-INFORMATION]
[PRIORITY]
[PARTICIPANT-PROVIDED-INFO]
[STATUS-INFO]
*[EXTENSION-ATTRIBUTE]
Figure 27: FLOOR-REQUEST-INFORMATION format
5.2.18 REQUESTED-BY-INFORMATION
The REQUESTED-BY-INFORMATION attribute is a grouped attribute that
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consists of a header, which is referred to as REQUESTED-BY-
INFORMATION-HEADER, followed by a sequence of attributes. The
following is the format of the REQUESTED-BY-INFORMATION-HEADER:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 0 0 1 0|M| Length | Requested-by ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 28: REQUESTED-BY-INFORMATION-HEADER format
Requested-by ID: this field contains a 16-bit value that uniquely
identifies a user within a conference.
The following is the ABNF of the REQUESTED-BY-INFORMATION grouped
attribute. (EXTENSION-ATTRIBUTE refers to extension attributes that
may be defined in the future.)
REQUESTED-BY-INFORMATION = (REQUESTED-BY-INFORMATION-HEADER)
[USER-DISPLAY-NAME]
[USER-URI]
*[EXTENSION-ATTRIBUTE]
Figure 29: REQUESTED-BY-INFORMATION format
5.3 Message Format
This section contains the normative ABNF (Augmented Backus-Naur Form)
[3] of the BFCP messages. Extension attributes that may be defined
in the future are referred to as EXTENSION-ATTRIBUTE in the ABNF.
5.3.1 FloorRequest
Floor participants request a floor by sending a FloorRequest message
to the floor control server. The following is the format of the
FloorRequest message:
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FloorRequest = (COMMON-HEADER)
*(FLOOR-ID)
[BENEFICIARY-ID]
[PARTICIPANT-PROVIDED-INFO]
[PRIORITY]
*[EXTENSION-ATTRIBUTE]
[NONCE]
[DIGEST]
Figure 30: FloorRequest format
5.3.2 FloorRelease
Floor participants release a floor by sending a FloorRelease message
to the floor control server. Floor participants also use the
FloorRelease message to cancel pending floor requests. The following
is the format of the FloorRelease message:
FloorRelease = (COMMON-HEADER)
(FLOOR-REQUEST-ID)
*[EXTENSION-ATTRIBUTE]
[NONCE]
[DIGEST]
Figure 31: FloorRelease format
5.3.3 FloorRequestQuery
Floor participants and floor chairs request information about a floor
request by sending a FloorRequestQuery message to the floor control
server. The following is the format of the FloorRequestQuery
message:
FloorRequestQuery = (COMMON-HEADER)
(FLOOR-REQUEST-ID)
*[EXTENSION-ATTRIBUTE]
[NONCE]
[DIGEST]
Figure 32: FloorRequestQuery format
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5.3.4 FloorRequestStatus
The floor control server informs floor participants and floor chairs
about the status of their floor requests by sending them
FloorRequestStatus messages. The following is the format of the
FloorRequestStatus message:
FloorRequestStatus = (COMMON-HEADER)
(FLOOR-REQUEST-INFORMATION)
[NONCE]
*[EXTENSION-ATTRIBUTE]
Figure 33: FloorRequestStatus format
5.3.5 UserQuery
Floor participants and floor chairs request information about a
participant and the floor requests related to this participant by
sending a UserQuery message to the floor control server. The
following is the format of the UserQuery message:
UserQuery = (COMMON-HEADER)
[BENEFICIARY-ID]
*[EXTENSION-ATTRIBUTE]
[NONCE]
[DIGEST]
Figure 34: UserQuery format
5.3.6 UserStatus
The floor control server provide information about participants and
their related floor requests to floor participants and floor chairs
by sending them UserStatus messages. The following is the format of
the UserStatus message:
UserStatus = (COMMON-HEADER)
[BENEFICIARY-INFORMATION]
1*(FLOOR-REQUEST-INFORMATION)
[NONCE]
*[EXTENSION-ATTRIBUTE]
Figure 35: UserStatus format
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5.3.7 FloorQuery
Floor participants and floor chairs request information about a floor
or floors by sending a FloorQuery message to the floor control
server. The following is the format of the FloorRequest message:
FloorQuery = (COMMON-HEADER)
*(FLOOR-ID)
*[EXTENSION-ATTRIBUTE]
[NONCE]
[DIGEST]
Figure 36: FloorQuery format
5.3.8 FloorStatus
The floor control server informs floor participants and floor chairs
about the status (e.g., the current holder) of a floor by sending
them FloorStatus messages. The following is the format of the
FloorStatus message:
FloorStatus = (COMMON-HEADER)
(FLOOR-ID)
*[FLOOR-REQUEST-INFORMATION]
[NONCE]
*[EXTENSION-ATTRIBUTE]
Figure 37: FloorStatus format
5.3.9 ChairAction
Floor chairs send instructions to floor control servers by sending
ChairAction messages. The following is the format of the ChairAction
message:
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ChairAction = (COMMON-HEADER)
1*(FLOOR-ID)
(FLOOR-REQUEST-ID)
(REQUEST-STATUS)
[STATUS-INFO]
*[EXTENSION-ATTRIBUTE]
[NONCE]
[DIGEST]
Figure 38: ChairAction format
5.3.10 ChairActionAck
Floor control servers confirm that they have accepted a ChairAction
message by sending a ChairActionAck message. The following is the
format of the ChairActionAck message:
ChairActionAck = (COMMON-HEADER)
[NONCE]
*[EXTENSION-ATTRIBUTE]
Figure 39: ChairActionAck format
5.3.11 Hello
Floor participants and floor chairs check the liveness of floor
control servers by sending a Hello message. The following is the
format of the Hello message:
Hello = (COMMON-HEADER)
*[EXTENSION-ATTRIBUTE]
[NONCE]
[DIGEST]
Figure 40: Hello format
5.3.12 HelloAck
Floor control servers confirm that they are alive on reception of a
Hello message by sending a HelloAck message. The following is the
format of the HelloAck message:
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HelloAck = (COMMON-HEADER)
(SUPPORTED-PRIMITIVES)
(SUPPORTED-ATTRIBUTES)
[NONCE]
*[EXTENSION-ATTRIBUTE]
Figure 41: HelloAck format
5.3.13 Error
Floor control servers inform floor participants and floor chairs
about errors processing requests by sending them Error messages. The
following is the format of the Error message:
Error = (COMMON-HEADER)
(ERROR-CODE)
[NONCE]
[ERROR-INFO]
*[EXTENSION-ATTRIBUTE]
Figure 42: Error format
6. Transport
BFCP entities exchange BFCP messages using TCP connections. TCP
provides an in-order reliable delivery of a stream of bytes.
Consequently, message framing is implemented in the application
layer. BFCP implements application-layer framing using TLV-encoded
attributes.
A client MUST NOT use more than one TCP connection to communicate
with a given floor control server within a conference. Nevertheless,
if the same physical box handles different clients (e.g., a floor
chair and a floor participant), which are identified by different
User IDs, a separate connection per client is allowed.
If a BFCP entity (a client or a floor control server) receives data
from TCP that cannot be parsed the entity MUST close the TCP
connection using a RESET call (send a TCP RST bit) and the connection
SHOULD be reestablished. Similarly, if a TCP connection cannot
deliver a BFCP message and times out, the TCP connection SHOULD be
reestablished.
The way connection reestablishment is handled depends on how the
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client obtains information to contact the floor control server (e.g.,
using an offer/answer exchange [13]). Once the TCP connection is
reestablished, the client MAY resend those message it did not get a
response for from the floor control server.
If a floor control server detects that the TCP connection towards one
of the floor participants is lost, it is up to the local policy of
the floor control server what to do with the pending floor requests
of the floor participant. In any case, it is RECOMMENDED that the
floor control server keeps the floor requests (i.e., does not cancel
them) while the TCP connection is reestablished.
If a client wishes to end its BFCP connection with a floor control
server, the client closes (i.e., a graceful close) the TCP connection
towards the floor control server. If a floor control server wishes
to end its BFCP connection with a client (e.g., the Focus of the
conference informs the floor control server that the client has been
kicked out from the conference), the floor control server closes
(i.e., a graceful close) the TCP connection towards the client.
7. Lower-Layer Security
BFCP relies on lower-layer security mechanisms to provide replay and
integrity protection, and confidentiality. BFCP floor control
servers MUST support TLS [4], and BFCP clients (which include both
floor participants and floor chairs) SHOULD support TLS. Any BFCP
entity MAY support other security mechanisms.
BFCP entities that implement TLS MUST support, at a minimum, the TLS
TLS_RSA_WITH_AES_128_CBC_SHA ciphersuite [6].
8. Protocol Transactions
In BFCP, there are two types of transactions: client-initiated
transactions and server-initiated transactions (notifications).
Client-initiated transactions consist of a request from a client to a
floor control server and a response from the floor control server to
the client. The request carries a Transaction ID in its common
header which the floor control server copies into the response.
Clients use Transaction ID values to match responses with previously-
issued requests.
Server-initiated transactions consist of a single message from a
floor control server to a client. Since they do not trigger any
response, their Transaction ID is set to 0.
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8.1 Client Behavior
A client starting a client-initiated transaction MUST set the
Conference ID in the common header of the message to the Conference
ID for the conference that the client obtained previously.
The client MUST set the Transaction ID value in the common header to
a number which is different to 0 and which MUST NOT be reused in
another message from the client until a response from the server is
received for the transaction. The client uses the Transaction ID
value to match this message with the response from the floor control
server.
8.2 Server Behavior
A floor control server sending a response within a client-initiated
transaction MUST copy the Conference ID, the Transaction ID, and the
User ID from the request received from the client into the response.
Server-initiated transactions MUST contain a Transaction ID equal to
0.
9. Authentication and Authorization
BFCP clients SHOULD authenticate the floor control server before
sending any BFCP message to it. Similarly, floor control servers
SHOULD authenticate a client before accepting any BFCP message from
it.
BFCP supports TLS-based mutual authentication between clients and
floor control servers, as specified in Section 9.1. This is the
RECOMMENDED authentication mechanism in BFCP.
Additionally, BFCP also provides a digest mechanism based on a shared
secret to provide client authentication in situations where TLS is
not used for some reason. This mechanism is described in
Section 9.2.
9.1 TLS-based Mutual Authentication
BFCP supports TLS-based mutual authentication between clients and
floor control servers. Authentication based on both, certificates
signed by a certificate authority and self-signed certificates is
supported.
If a client and a floor control server have certificates signed by a
certificate authority known to both, they can use these certificates
to authenticate each other at TLS establishment time. Otherwise,
BFCP assumes that there is an integrity-protected channel between the
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client and the floor control server that can be used to exchange
their self-signed certificates or, more commonly, the fingerprints of
these certificates. These certificates are used at TLS establishment
time.
The implementation of such an integrity-protected channel using
SIP and the offer/answer model is described in [13].
9.2 Digest-based Client Authentication
BFCP supports digest-based client authentication based on a shared
secret between a client and the floor control server. It is assumed
that an encrypted and integrity-protected channel exists between the
client and the floor control server. This channel is used to
generate a shared secret between them.
The implementation of such an encrypted and integrity-protected
channel using SIP and the offer/answer model is described in [13].
Digest-based client authentication in BFCP is based on the DIGEST
attribute. This attribute contains an algorithm identifier and a
keyed digest of the of the BFCP message using that algorithm. The
text used as input to the digest algorithm is the BFCP message,
including the common header, up to and including the attribute
preceding the DIGEST attribute. Depending on the algorithm, this
text may need to be padded with zeroes. Section 5.2.7 lists the
algorithms specified in BFCP.
The key used as input to the keyed digest is the secret shared
between the server and the user identified by the User ID in the
common header of the message.
Section 9.2.1 and Section 9.2.2 discuss how to achieve client
authentication using the DIGEST attribute.
9.2.1 Client Behavior
To achieve client authentication, a client needs to prove to the
floor control server that the client can produce a DIGEST attribute
for a message using their shared secret and that the message is fresh
(to avoid replay attacks). Clients prove the freshness of a message
by including a NONCE attribute in the message. The NONCE attribute
is the second to last attribute in the message (the last one is the
DIGEST attribute).
Clients can obtain the digest algorithms supported by the floor
control server in an Error response from the floor control server
with Error Code 3 (DIGEST Attribute Required). A client SHOULD use
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the first digest algorithm in the list that it supports.
Additionally, as an optimization, the floor control server and the
client can agree on the algorithm to be used using an out-of-band
mechanism (e.g., using an offer/answer exchange as described in
[13]). This way, the client does not need to generate an initial
BFCP message only to have it rejected by the floor control server
with an Error response containing a list with its supported
algorithms.
If after sending a message with a DIGEST attribute, a client receives
an Error response with Error Code 3 (DIGEST Attribute Required) with
a list of digest algorithms, the client SHOULD re-send the message
using the first digest algorithm in the list that it supports.
The nonce to be placed in the NONCE attribute by the client is
typically provided by the floor control server in an Error response
-- typically with Error Code 3 (DIGEST Attribute Required) or 6
(Invalid Nonce). Additionally, as an optimization, the floor control
server can provide a client with a NONCE to be used in the first
message generated by the client using an out-of-band mechanism (e.g.,
using an offer/answer exchange as described in [13]). This way, the
client does not need to generate an initial BFCP message only to have
it rejected by the floor control server with an Error response
containing a nonce.
A client that obtains a nonce out-of-band SHOULD add a NONCE
attribute and a DIGEST attribute to the first message it sends to the
floor control server. Furthermore, if any client generates a message
without a DIGEST attribute and receives an Error response with Error
Code 3 (DIGEST Attribute Required), the client SHOULD re-send the
message with a DIGEST attribute and a NONCE attribute with the nonce
received in the Error response.
If after sending a message with a DIGEST attribute, a client receives
an Error response with Error Code 4 (Invalid Nonce), the client
SHOULD re-send the message using the new nonce received in the Error
response. If the Error Code is 5 (Authentication Failed) instead,
the client MUST NOT send further messages to the floor control server
until it has obtained a different (hopefully valid) shared secret
than the one used in the original message.
If a client receives a nonce in a message from the floor control
server, the client SHOULD add a NONCE attribute with this nonce and a
DIGEST attribute to its next message to the floor control server.
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9.2.2 Floor Control Server Behavior
If the floor control server receives a message without DIGEST
attribute from an unauthenticated client, the floor control server
responds with an Error message with Error Code 3 (DIGEST Attribute
Required). The floor control message MUST include a list with the
digest algorithms supported by the floor control server in order of
preference (i.e., the first algorithm is the most preferred) and a
NONCE attribute with a nonce value that is unguessable by attackers.
When a floor control server receives a BFCP message with a DIGEST
attribute, it checks whether the Algorithm identifier in the DIGEST
attribute corresponds to an algorithm that is supported by the floor
control server. If it does not, the floor control server SHOULD
return an Error message with Error Code 3 (DIGEST Attribute Required)
with a list with the digest algorithms supported by the floor control
server.
If the algorithm identifier is valid, the floor control server checks
whether the NONCE attribute carries a nonce which was generated by
the floor control server for this client and which still has not
expired. If the nonce is not valid, authentication is considered to
have failed, in which case the floor control server SHOULD return an
Error message with Error Code 4 (Invalid Nonce) with a new nonce in a
NONCE attribute.
If the nonce is valid, the floor control server calculates the keyed
digest of the message using the algorithm identified by the DIGEST
attribute. The key used as input to the keyed digest is the secret
shared between the server and the user identified by the User ID in
the common header of the message. If the resulting value is the same
as the one in the DIGEST attribute, authentication is considered
successful.
If the resulting value is different than the one in the DIGEST
attribute, authentication is considered to have failed, in which case
the server SHOULD return an Error message, as described in
Section 13.8, with Error Code 5 (Authentication Failed). Messages
from a client that cannot be authenticated MUST NOT be processed
further.
Floor control servers MAY include a NONCE attribute in their
responses to provide the nonce to be used in the next message by the
client. However, when TLS is used, floor control servers typically
authenticate only the first message sent over the TLS connection.
After authenticating a BFCP message, the floor control server checks
whether or not the client is authorized to perform the operation it
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is requesting. If the client is not authorized to perform the
operation being requested, the floor control server generates an
Error message, as described in Section 13.8, with an Error code with
a value of 8 (Unauthorized Operation). Messages from a client that
cannot be authorized MUST NOT be processed further.
10. Floor Participant Operations
This section specifies how floor participants can perform different
operations, such as requesting a floor, using the protocol elements
described in earlier sections. Section 11 specifies operations that
are specific to floor chairs, such as instructing the floor control
server to grant or revoke a floor, and Section 12 specifies
operations that can be performed by any client (i.e., both floor
participants and floor chairs).
10.1 Requesting a Floor
A floor participant that wishes to request one or more floors does so
by sending a FloorRequest message to the floor control server.
10.1.1 Sending a FloorRequest Message
The ABNF in Section 5.3.1 describes the attributes that a
FloorRequest message can contain. In addition, the ABNF specifies
normatively which of these attributes are mandatory, and which ones
are optional.
The floor participant sets the Conference ID and the Transaction ID
in the common header following the rules given in Section 8.1.
Additionally, the floor participant follows the rules in Section 9
which relate to the authentication of the message.
The floor participant sets the User ID in the common header to the
floor participant's identifier. This User ID will be used by the
floor control server to authenticate and authorize the request. If
the sender of the FloorRequest message (identified by the User ID) is
not the participant that would eventually get the floor (i.e., a
third party floor request), the sender SHOULD add a BENEFICIARY-ID
attribute to the message identifying the beneficiary of the floor.
Note that the name space for both the User ID and the Beneficiary
ID is the same. That is, a given participant is identified by a
single 16-bit value that can be used in the User ID in the common
header and in several attributes: BENEFICIARY-ID, BENEFICIARY-
INFORMATION, and REQUESTED-BY-INFORMATION.
The floor participant must insert at least one FLOOR-ID attribute in
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the FloorRequest message. If the client inserts more than one
FLOOR-ID attributes, the floor control server will treat all the
floor requests as an atomic package. That is, the floor control
server will either grant or deny all the floors in the FloorRequest
message.
The floor participant may use a PARTICIPANT-PROVIDED-INFO attribute
to state the reason why the floor or floors are being requested. The
Text field in the PARTICIPANT-PROVIDED-INFO attribute is intended for
human consumption.
The floor participant may request the server to handle the floor
request with a certain priority using a PRIORITY attribute.
10.1.2 Receiving a Response
A message from the floor control server is considered to be a
response to the FloorRequest message if the message from the floor
control server has the same Conference ID, Transaction ID, and User
ID as the FloorRequest message, as described in Section 8.1.
The successful processing of a FloorRequest message at the floor
control server involves generating one or several FloorRequestStatus
messages. The floor participant obtains a Floor Request ID in the
Floor Request ID field of a FLOOR-REQUEST-INFORMATION attribute in
the first FloorRequestStatus message from the floor control server.
Subsequent FloorRequestStatus messages from the floor control server
regarding the same floor request will carry the same Floor Request ID
in a FLOOR-REQUEST-INFORMATION attribute as the initial
FloorRequestStatus message. This way, the floor participant can
associate subsequent incoming FloorRequestStatus messages with the
ongoing floor request.
The floor participant obtains information about the status of the
floor request in the FLOOR-REQUEST-INFORMATION attribute of each of
the FloorRequestStatus messages received from the floor control
server. This attribute is a grouped attribute and, as such, it
includes a number of attributes that provide information about the
floor request.
The REQUEST-STATUS attribute. If the Request Status value is
Granted, all the floors that were requested in the FloorRequest
message have been granted. If the Request Status value is Denied,
all the floors that were requested in the FloorRequest message have
been denied. A floor request is considered to be ongoing while it is
in the Pending, Accepted, or Granted states.
The STATUS-INFO attribute, if present, provides extra information
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which the floor participant MAY display to the user.
The BENEFICIARY-INFORMATION attribute identifies the beneficiary of
the floor request in third-party floor requests. The REQUESTED-BY-
INFORMATION attribute may be not be present in FloorRequestStatus
messages received by the floor participant that requested the floor
because this floor participant is already identified by the User ID
in the common header.
The PRIORITY attribute, when present, contains the priority that was
requested by the generator of the FloorRequest message.
If the response is an Error message, the floor control server could
not process the FloorRequest message for some reason, which is
described in the Error message.
10.2 Cancelling a Floor Request and Releasing a Floor
A floor participant that wishes to cancel an ongoing floor request
does so by sending a FloorRelease message to the floor control
server. The FloorRelease message is also used by floor participants
that hold a floor and would like to release it.
10.2.1 Sending a FloorRelease Message
The ABNF in Section 5.3.2 describes the attributes that a
FloorRelease message can contain. In addition, the ABNF specifies
normatively which of these attributes are mandatory, and which ones
are optional.
The floor participant sets the Conference ID and the Transaction ID
in the common header following the rules given in Section 8.1.
Additionally, the floor participant follows the rules in Section 9
which relate to the authentication of the message. The floor
participant sets the User ID in the common header to the floor
participant's identifier. This User ID will be used by the floor
control server to authenticate and authorize the request.
Note that the FloorRelease message is used to release a floor or
floors that were granted and to cancel ongoing floor requests
(from the protocol perspective both are ongoing floor requests).
Using the same message in both situations helps resolve the race
condition that occurs when the FloorRelease message and the
FloorGrant message cross each other on the wire.
The floor participant uses the FLOOR-REQUEST-ID that was received in
the response to the FloorRequest message that the FloorRelease
message is cancelling.
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Note that if the floor participant requested several floors as an
atomic operation (i.e., in a single FloorRequest message), all the
floors are released as an atomic operation as well (i.e., all are
released at the same time).
10.2.2 Receiving a Response
A message from the floor control server is considered to be a
response to the FloorRelease message if the message from the floor
control server has the same Conference ID, Transaction ID, and User
ID as the FloorRequest message, as described in Section 8.1.
If the response is a FloorRequestStatus message, the Request Status
value in the REQUEST-STATUS attribute (within the FLOOR-REQUEST-
INFORMATION grouped attribute) will be Cancelled or Released.
If the response is an Error message, the floor control server could
not process the FloorRequest message for some reason, which is
described in the Error message.
It is possible that the FloorRelease message crosses on the wire with
a FloorRequestStatus message from the server with a Request Status
different from Cancelled or Released. In any case, such a
FloorRequestStatus message will not be a response to the FloorRelease
message, because its Transaction ID will not match that of the
FloorRelease.
11. Chair Operations
This section specifies how floor chairs can instruct the floor
control server to grant or revoke a floor using the protocol elements
described in earlier sections.
Floor chairs that wish to send instructions to a floor control server
do so by sending a ChairAction message.
11.1 Sending a ChairAction Message
The ABNF in Section 5.3.9 describes the attributes that a ChairAction
message can contain. In addition, the ABNF specifies normatively
which of these attributes are mandatory, and which ones are optional.
The floor chair sets the Conference ID and the Transaction ID in the
common header following the rules given in Section 8.1.
Additionally, the floor chair follows the rules in Section 9 which
relate to the authentication of the message. The floor participant
sets the User ID in the common header to the floor participant's
identifier. This User ID will be used by the floor control server to
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authenticate and authorize the request.
The ChairAction message contains instructions that apply to one or
more floors within a particular floor request. The floor or floors
are identified by FLOOR-ID attributes and the floor request is
identified by a FLOOR-REQUEST-ID attribute, which are carried in the
ChairAction message.
For example, if a floor request consists of two floors that depend
on different floor chairs, each floor chair will grant its floor
within the floor request. Once both chairs have granted their
floor, the floor control server will grant the floor request as a
whole. On the other hand, if one of the floor chairs denies its
floor, the floor control server will deny the floor request as a
whole, regardless of the other floor chair's decision.
The floor chair provides the new status for one or more floors within
the floor request using a REQUEST-STATUS attribute. If the new
status of the floor request is Accepted, the floor chair MAY use the
Queue Position field to provide a queue position for the floor
request. If the floor chair does not wish to provide a queue
position, all the bits of the Queue Position field SHOULD be set to
zero. The floor chair SHOULD use the Status Revoked to revoke a
floor that was granted (i.e., Granted status) and the Status Denied
to reject floor requests in any other status (e.g., Pending and
Accepted).
Note that a floor request may involve several floors and that a
ChairAction message may only deal with a subset of these floors
(e.g., if a single floor chair is not authorized to manage all the
floors). In this case, the REQUEST-STATUS that the floor chair
provides in the ChairAction message might not be the actual status
that the floor request gets at the server. The floor control
server will combine the instructions received from the different
floor chairs to come up with the actual status of the floor
request.
The floor chair may use a STATUS-INFO attribute to state the reason
why the floor or floors are being accepted, granted, or revoked. The
Text in the STATUS-INFO attribute is intended for human consumption.
11.2 Receiving a Response
A message from the floor control server is considered to be a
response to the ChairAction message if the message from the server
has the same Conference ID, Transaction ID, and User ID as the
ChairAction message, as described in Section 8.1.
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A ChairActionAck message from the floor control server confirms that
the floor control server has accepted the ChairAction message. An
Error message indicates that the floor control server could not
process the ChairAction message for some reason, which is described
in the Error message.
12. General Client Operations
This section specifies operations that can be performed by any
client. That is, they are not specific to floor participants or
floor chairs. They can be performed by both.
12.1 Requesting Information about Floors
A client can obtain information about the status of a floor or floors
in different ways, which include using BFCP and using out-of-band
mechanisms. Clients using BFCP to obtain such information use the
procedures described in this section.
Clients request information about the status of one or several floors
by sending a FloorQuery message to the floor control server.
12.1.1 Sending a FloorQuery Message
The ABNF in Section 5.3.7 describes the attributes that a FloorQuery
message can contain. In addition, the ABNF specifies normatively
which of these attributes are mandatory, and which ones are optional.
The client sets the Conference ID and the Transaction ID in the
common header following the rules given in Section 8.1.
Additionally, the client follows the rules in Section 9 which relate
to the authentication and the protection of the integrity of the
message. The client sets the User ID in the common header to the
client's identifier. This User ID will be used by the floor control
server to authenticate and authorize the request.
The client inserts in the message all the Floor IDs it wants to
receive information about. The floor control server will send
periodic information about all these floors. If the client does not
want to receive information about a particular floor any longer, it
sends a new FloorQuery message removing the FLOOR-ID of this floor.
If the client does not want to receive information about any floor
any longer, it sends a FloorQuery message with no FLOOR-ID attribute.
12.1.2 Receiving a Response
A message from the floor control server is considered to be a
response to the FloorQuery message if the message from the floor
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control server has the same Conference ID, Transaction ID, and User
ID as the FloorRequest message, as described in Section 8.1.
On reception of the FloorQuery message, the floor control server will
respond with a FloorStatus message or with an Error message. If the
response is a FloorStatus message, it will contain information about
one of the floors the client requested information about. If the
client did not include any FLOOR-ID attribute in its FloorQuery
message (i.e., the client does not want to receive information about
any floor any longer), the FloorStatus message from the floor control
server will not include any FLOOR-ID attribute either.
FloorStatus messages which carry information about a floor contain a
FLOOR-ID attribute that identifies the floor. After this attribute,
FloorStatus messages contain information about existing (one or more)
floor request that relate to that floor. The information about each
particular floor request is encoded in a FLOOR-REQUEST-INFORMATION
attribute. This grouped attribute carries a Floor Request ID that
identifies the floor request followed by a set of attributes that
provide information about the floor request.
After the first FloorStatus, the floor control server will continue
sending FloorStatus messages periodically informing the client about
changes on the floors the client requested information about.
12.2 Requesting Information about Floor Requests
A client can obtain information about the status of one or several
floor requests in different ways, which include using BFCP and using
out-of-band mechanisms. Clients using BFCP to obtain such
information use the procedures described in this section.
Clients request information about the current status of a floor
requests by sending a FloorRequestQuery message to the floor control
server.
Requesting information about a particular floor request is useful in
a number of situations. For example, on reception of a FloorRequest
message, a floor control server may choose to return
FloorRequestStatus messages only when the floor request changes its
state (e.g., from Accepted to Granted), but not when the floor
request advances in its queue. In this situation, if the user
requests it, the floor participant can use a FloorRequestQuery
message to poll the floor control server for the status of the floor
request.
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12.2.1 Sending a FloorRequestQuery Message
The ABNF in Section 5.3.3 describes the attributes that a
FloorRequestQuery message can contain. In addition, the ABNF
specifies normatively which of these attributes are mandatory, and
which ones are optional.
The client sets the Conference ID and the Transaction ID in the
common header following the rules given in Section 8.1.
Additionally, the client follows the rules in Section 9 which relate
to the authentication of the message. The client sets the User ID in
the common header to the client's identifier. This User ID will be
used by the floor control server to authenticate and authorize the
request.
The client must insert a FLOOR-REQUEST-ID attribute that identifies
the floor request at the floor control server.
12.2.2 Receiving a Response
A message from the floor control server is considered to be a
response to the FloorRequestQuery message if the message from the
floor control server has the same Conference ID, Transaction ID,a nd
User ID as the FloorRequestQuery message, as described in
Section 8.1.
If the response is a FloorRequestStatus message, the client obtains
information about the status of the FloorRequest the client requested
information about in a FLOOR-REQUEST-INFORMATION attribute.
If the response is an Error message, the floor control server could
not process the FloorRequestQuery message for some reason, which is
described in the Error message.
12.3 Requesting Information about a User
A client can obtain information about a participant and the floor
requests related to this participant in different ways, which include
using BFCP and using out-of-band mechanisms. Clients using BFCP to
obtain such information use the procedures described in this section.
Clients request information about a participant and the floor
requests related to this participant by sending a UserQuery message
to the floor control server.
This functionality may be useful for floor chairs or floor
participants interested in the display name and the URI of a
particular floor participant. In addition, a floor participant may
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find it useful to request information about itself. For example, a
floor participant, after experiencing connectivity problems (e.g.,
its TCP connection with the floor control server was down for a while
and eventually was re-established), may need to request information
about all the still existing floor requests associated to itself.
12.3.1 Sending a UserQuery Message
The ABNF in Section 5.3.5 describes the attributes that a UserQuery
message can contain. In addition, the ABNF specifies normatively
which of these attributes are mandatory, and which ones are optional.
The client sets the Conference ID and the Transaction ID in the
common header following the rules given in Section 8.1.
Additionally, the client follows the rules in Section 9 which relate
to the authentication of the message. The client sets the User ID in
the common header to the client's identifier. This User ID will be
used by the floor control server to authenticate and authorize the
request.
If the floor participant the client is requesting information about
is not the client issuing the UserQuery message (which is identified
by the User ID in the common header of the message) the client MUST
insert a BENEFICIARY-ID attribute.
12.3.2 Receiving a Response
A message from the floor control server is considered to be a
response to the UserQuery message if the message from the floor
control server has the same Conference ID, Transaction ID, and User
ID as the UserQuery message, as described in Section 8.1.
If the response is a UserStatus message, the client obtains
information about the floor participant in a BENEFICIARY-INFORMATION
grouped attribute and about the status of the floor requests
associated with the floor participant in FLOOR-REQUEST-INFORMATION
attributes.
If the response is an Error message, the floor control server could
not process the UserQuery message for some reason, which is described
in the Error message.
12.4 Obtaining the Capabilities of a Floor Control Server
A client that wishes to obtain the capabilities of a floor control
server does so by sending a Hello message to the floor control
server.
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12.4.1 Sending a Hello Message
The ABNF in Section 5.3.11 describes the attributes that a Hello
message can contain. In addition, the ABNF specifies normatively
which of these attributes are mandatory, and which ones are optional.
The client sets the Conference ID and the Transaction ID in the
common header following the rules given in Section 8.1.
Additionally, the client follows the rules in Section 9 which relate
to the authentication and the protection of the integrity of the
message. The client sets the User ID in the common header to the
client's identifier. This User ID will be used by the floor control
server to authenticate and authorize the request.
12.4.2 Receiving Responses
A message from the floor control server is considered a response to
the Hello message by the client if the message from the floor control
server has the same Conference ID, Transaction ID, and User ID as the
Hello message, as described in Section 8.1.
If the response is a HelloAck message, the floor control server could
process successfully the Hello message. The SUPPORTED-ATTRIBUTES
attribute indicates which attributes are supported by the server.
If the response is an Error message, the floor control server could
not process the Hello message for some reason, which is described in
the Error message.
13. Floor Control Server Operations
This section specifies how floor control servers can perform
different operations, such as granting a floor, using the protocol
elements described in earlier sections.
On reception of a message from a client, the floor control server
MUST check whether or not the value of the Conference ID matched an
existing conference. If it does not, the floor control server SHOULD
send an Error message, as described in Section 13.8, with Error code
1 (Conference does not Exist).
On reception of a message from a client, the floor control server
follows the rules in Section 9, which relate to the authentication of
the message.
On reception of a message from a client, the floor control server
MUST check whether or not it understands all the mandatory ( 'M' bit
set) attributes in the message. If the floor control server does not
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understand all of them, the floor control server SHOULD send an Error
message, as described in Section 13.8, with Error code 2
(Authentication Failed). The Error message SHOULD list the
attributes that were not understood.
13.1 Reception of a FloorRequest Message
On reception of a FloorRequest message, the floor control server
follows the rules in Section 9 which relate to client authentication
and authorization. If while processing the FloorRequest message, the
floor control server encounters an error, it SHOULD generate an Error
response following the procedures described in Section 13.8
BFCP allows floor participants to have several ongoing floor
requests for the same floor (e.g., the same floor participant can
occupy more than one position in a queue at the same time). A
floor control server that only supports a certain number of
ongoing floor requests per floor participant (e.g., one) can use
Error Code 11 (You have Already Reached the Maximum Number of
Ongoing Floor Requests for this Floor) to inform the floor
participant.
13.1.1 Generating the First FloorRequestStatus Message
The successful processing of a FloorRequest message by a floor
control server involves generating one or several FloorRequestStatus
messages, the first of which SHOULD be generated as soon as possible.
If the floor control server cannot accept, grant, or deny the floor
request right away (e.g., a decision from a chair is needed), it
SHOULD use a Request Status value of Pending in the REQUEST-STATUS
attribute (within the FLOOR-REQUEST-INFORMATION grouped attribute) of
the first FloorRequestStatus message it generates.
The policy a floor control server follows to grant or deny floors
is outside the scope of this document. A given floor control
server may perform these decisions automatically while another may
contact a human acting as a chair everytime a decision needs to be
made.
The floor control server MUST copy the Conference ID, the Transaction
ID, and the User ID from the FloorRequest into the
FloorRequestStatus, as described in Section 8.2. Additionally, the
floor control server MUST add a FLOOR-REQUEST-INFORMATION grouped
attribute to the FloorRequestStatus. The attributes contained in
this grouped attribute carry information about the floor request.
The floor control server MUST assign an identitifier that is unique
within the conference to this floor request, and MUST insert it in
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the Floor Request ID field of the FLOOR-REQUEST-INFORMATION
attribute. This identifier will be used by the floor participant (or
by a chair or chairs) to refer to this specific floor request in the
future.
The floor control server MUST copy the FLOOR-ID attributes from the
FloorRequest into the FLOOR-REQUEST-INFORMATION attribute. These
FLOOR-ID attributes identify the floors being requested (i.e., the
floors associated with this particular floor request).
The floor control server SHOULD copy (if present) the contents of the
BENEFICIARY-ID attribute from the FloorRequest into a BENEFICIARY-
INFORMATION attribute inside the FLOOR-REQUEST-INFORMATION grouped
attribute. Additionally, the floor control server MAY provide the
display name and the URI of the beneficiary in this BENEFICIARY-
INFORMATION attribute.
The floor control server MAY provide information about the requester
of the floor in a REQUESTED-BY-INFORMATION attribute inside the
FLOOR-REQUEST-INFORMATION grouped attribute.
The floor control server MAY copy (if present) the PRIORITY attribute
from the FloorRequest into the FLOOR-REQUEST-INFORMATION grouped
attribute. Note that this attribute carries the priority requested
by the participant. The priority the floor control server assigns to
the floor request depends on the priority requested by the
participant and the rights the participant has according to the
policy of the conference. For example, a participant that is only
allowed to use the Normal priority may request Highest priority for a
floor request. In that case, the floor control server would ignore
the priority requested by the participant.
The floor control server MAY copy (if present) the PARTICIPANT-
PROVIDED-INFO attribute from the FloorRequest into the FLOOR-REQUEST-
INFO grouped attribute.
13.1.2 Generation of Subsequent FloorRequestStatus Messages
A floor request is considered to be ongoing as long as it is not in
the Cancelled, Released, or Revoked states. If the REQUEST-STATUS
attribute (inside the FLOOR-REQUEST-INFORMATION grouped attribute) of
the first FloorRequestStatus message generated by the floor control
server did not indicate any of these states, the floor control server
will need to send subsequent FloorRequestStatus messages.
When the status of the floor request changes, the floor control
server SHOULD send new FloorRequestStatus messages with the
appropriate Request Status. The floor control server MUST add a
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FLOOR-REQUEST-INFORMATION attribute with a Floor Request ID equal to
the one sent in the first FloorRequestStatus message to any new
FloorRequestStatus related to the same floor request. (The Floor
Request ID identifies the floor request the FloorRequestStatus
applies to.)
The floor control server MUST set the Transaction ID of subsequent
FloorRequestStatus messages to 0.
The rate at which the floor control server sends
FloorRequestStatus messages is a matter of local policy. A floor
control server may choose to send a new FloorRequestStatus message
every time the floor request moves in the floor request queue
while another may choose to only send a new FloorRequestStatus
message when the floor request is Granted or Denied.
The floor control server may add a STATUS-INFO attribute to any of
the FloorRequestStatus messages it generates to provide extra
information about its decisions regarding the floor request (e.g.,
why it was denied).
Floor participants and floor chairs may request to be informed
about the status of a floor following the procedures in
Section 12.1. If the processing of a floor request changes the
status of a floor (e.g., the floor request is granted and
consequently the floor has a new holder), the floor control server
needs to follow the procedures in Section 13.5 to inform the
clients that have requested that information
The common header and the rest of the attributes are the same as in
the first FloorRequestStatus message.
The floor control server can discard the state information about a
particular floor request when this reaches a status of Cancelled,
Released, or Revoked.
13.2 Reception of a FloorRequestQuery Message
On reception of a FloorRequestQuery message, the floor control server
follows the rules in Section 9 which relate to client authentication
and authorization. If while processing the FloorRequestQuery
message, the floor control server encounters an error, it SHOULD
generate an Error response following the procedures described in
Section 13.8
The successful processing of a FloorRequestQuery message by a floor
control server involves generating a FloorRequestStatus message,
which SHOULD be generated as soon as possible.
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The floor control server MUST copy the Conference ID, the Transaction
ID, and the User ID from the FloorRequestQuery message into the
FloorRequestStatus message, as described in Section 8.2.
Additionally, the floor control server MUST add a FLOOR-REQUEST-
INFORMATION grouped attribute to the FloorRequestStatus. The
attributes contained in this grouped attribute carry information
about the floor request.
The floor control server MUST copy the contents of the
FLOOR-REQUEST-ID attribute from the FloorRequestQuery message into
the Floor Request ID field of the FLOOR-REQUEST-INFORMATION
attribute.
The floor control server MUST add FLOOR-ID attributes to the FLOOR-
REQUEST-INFORMATION grouped attribute identifying the floors being
requested (i.e., the floors associated with the floor request
identified by the FLOOR-REQUEST-ID attribute).
The floor control server SHOULD add a BENEFICIARY-ID attribute to the
FLOOR-REQUEST-INFORMATION grouped attribute identifying the
beneficiary of the floor request. Additionally, the floor control
server MAY provide the display name and the URI of the beneficiary in
this BENEFICIARY-INFORMATION attribute.
The floor control server MAY provide information about the requester
of the floor in a REQUESTED-BY-INFORMATION attribute inside the
FLOOR-REQUEST-INFORMATION grouped attribute.
The floor control server MAY provide the reason why the floor
participant requested the floor in a PARTICIPANT-PROVIDED-INFO.
The floor control server MAY also add to the FLOOR-REQUEST-
INFORMATION grouped attribute a PRIORITY attribute with the Priority
value requested for the floor request and a STATUS-INFO attribute
with extra information about the floor request.
The floor control server adds a REQUEST-STATUS attribute to the
FLOOR-REQUEST-INFORMATION grouped attribute with the current status
of the floor request.
13.3 Reception of a UserQuery Message
On reception of a UserQuery message, the floor control server follows
the rules in Section 9 which relate to client authentication and
authorization. If while processing the UserQuery message, the floor
control server encounters an error, it SHOULD generate an Error
response following the procedures described in Section 13.8
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The successful processing of a UserQuery message by a floor control
server involves generating a UserStatus message, which SHOULD be
generated as soon as possible.
The floor control server MUST copy the Conference ID, the Transaction
ID, and the User ID from the UserQuery message into the USerStatus
message, as described in Section 8.2.
The sender of the UserQuery message is requesting information about
all the floor requests associated to a given participant (i.e., the
floor requests where the participant is either the beneficiary or the
requester). This participant is identified by a BENEFICIARY-ID
attribute or, in the absence of a BENEFICIARY-ID attribute, by a the
User ID in the common header of the UserQuery message.
The floor control server MUST copy, if present, the contents of the
BENEFICIARY-ID attribute from the UserQuery message into a
BENEFICIARY-INFORMATION attribute in the UserStatus message.
Additionally, the floor control server MAY provide the display name
and the URI of the participant the UserStatus message provides
information on in this BENEFICIARY-INFORMATION attribute.
The floor control server SHOULD add to the UserStatus message a
FLOOR-REQUEST-INFORMATION grouped attribute for each floor request
related to the participant the message provides information on (i.e.,
the floor requests where the participant is either the beneficiary or
the requester). For each FLOOR-REQUEST-INFORMATION attribute, the
floor control server follows the following steps.
The floor control server MUST identity the floor request the FLOOR-
REQUEST-INFORMATION attribute applies to by filling the Floor Request
ID field of the FLOOR-REQUEST-INFORMATION attribute.
The floor control server MUST add FLOOR-ID attributes to the FLOOR-
REQUEST-INFORMATION grouped attribute identifying the floors being
requested (i.e., the floors associated with the floor request
identified by the FLOOR-REQUEST-ID attribute).
The floor control server SHOULD add a BENEFICIARY-ID attribute to the
FLOOR-REQUEST-INFORMATION grouped attribute identifying the
beneficiary of the floor request. Additionally, the floor control
server MAY provide the display name and the URI of the beneficiary in
this BENEFICIARY-INFORMATION attribute.
The floor control server MAY provide information about the requester
of the floor in a REQUESTED-BY-INFORMATION attribute inside the
FLOOR-REQUEST-INFORMATION grouped attribute.
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The floor control server MAY provide the reason why the floor
participant requested the floor in a PARTICIPANT-PROVIDED-INFO.
The floor control server MAY also add to the FLOOR-REQUEST-
INFORMATION grouped attribute a PRIORITY attribute with the Priority
value requested for the floor request and a STATUS-INFO attribute
with extra information about the floor request.
The floor control server MUST add a REQUEST-STATUS attribute to the
FLOOR-REQUEST-INFORMATION grouped attribute with the current status
of the floor request.
13.4 Reception of a FloorRelease Message
On reception of a FloorRelease message, the floor control server
follows the rules in Section 9 which relate to client authentication
and authorization. If while processing the FloorRelease message, the
floor control server encounters an error, it SHOULD generate an Error
response following the procedures described in Section 13.8
The successful processing of a FloorRelease message by a floor
control server involves generating a FloorRequestStatus message,
which SHOULD be generated as soon as possible.
The floor control server MUST copy the Conference ID, the Transaction
ID, and the User ID from the FloorRelease message into the
FloorRequestStatus message, as described in Section 8.2.
The floor control server MUST add a FLOOR-REQUEST-INFORMATION grouped
attribute to the FloorRequestStatus. The attributes contained in
this grouped attribute carry information about the floor request.
The FloorRelease message identifies the floor request it applies to
using a FLOOR-REQUEST-ID. The floor control server MUST copy the
contents of the FLOOR-REQUEST-ID attribute from the FloorRelease
message into the Floor Request ID field of the FLOOR-REQUEST-
INFORMATION attribute.
The floor control server MUST add FLOOR-ID attributes to the FLOOR-
REQUEST-INFORMATION grouped attribute identifying the floors being
requested (i.e., the floors associated with the floor request
identified by the FLOOR-REQUEST-ID attribute).
The floor control server SHOULD add a BENEFICIARY-ID attribute to the
FLOOR-REQUEST-INFORMATION grouped attribute identifying the
beneficiary of the floor request. Additionally, the floor control
server MAY provide the display name and the URI of the beneficiary in
this BENEFICIARY-INFORMATION attribute.
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The floor control server MAY provide information about the requester
of the floor in a REQUESTED-BY-INFORMATION attribute inside the
FLOOR-REQUEST-INFORMATION grouped attribute.
The floor control server MAY provide the reason why the floor
participant requested the floor in a PARTICIPANT-PROVIDED-INFO.
The floor control server MAY also add to the FLOOR-REQUEST-
INFORMATION grouped attribute a PRIORITY attribute with the Priority
value requested for the floor request and a STATUS-INFO attribute
with extra information about the floor request.
The floor control server MUST add a REQUEST-STATUS attribute to the
FLOOR-REQUEST-INFORMATION grouped attribute. The Request Status
value SHOULD be Released, if the floor (or floors) had been
previously granted, or Cancelled, if the floor (or floors) had not
been previously granted.
13.5 Reception of a FloorQuery Message
On reception of a FloorQuery message, the floor control server
follows the rules in Section 9 which relate to client authentication.
If while processing the FloorRelease message, the floor control
server encounters an error, it SHOULD generate an Error response
following the procedures described in Section 13.8
A floor control server receiving a FloorQuery message from a client
SHOULD keep this client informed about the status of the floors
identified by FLOOR-ID attributes in the FloorQuery message. Floor
Control Servers keep clients informed by using FloorStatus messages.
An individual FloorStatus message carries information about a single
floor. So, when a FloorQuery message requests information about more
than one floor, the floor control server needs to send separate
FloorStatus messages for different floors.
The information FloorQuery messages carry may depend on the user
requesting the information. For example, a chair may be able to
receive information about pending requests while a regular user may
not be authorized to do so.
13.5.1 Generation of the First FloorStatus Message
The successful processing of a FloorQuery message by a floor control
server involves generating one or several FloorStatus messages, the
first of which SHOULD be generated as soon as possible.
The floor control server MUST copy the Conference ID, the Transaction
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ID, and the User ID from the FloorQuery message into the FloorStatus
message, as described in Section 8.2.
If the FloorQuery message did not contain any FLOOR-ID attribute, the
floor control server sends the FloorStatus message without adding any
additional attribute and does not send any subsequent FloorStatus
message to the floor participant.
If the FloorQuery message contained one or more FLOOR-ID attributes,
the floor control server chooses one among them and adds this
FLOOR-ID attribute to the FloorStatus message. The floor control
server SHOULD add a FLOOR-REQUEST-INFORMATION grouped attribute for
each floor request associated to the floor. Each FLOOR-REQUEST-
INFORMATION grouped attribute contains a number of attributes which
provide information about the floor request. For each FLOOR-REQUEST-
INFORMATION attribute, the floor control server follows the following
steps.
The floor control server MUST identity the floor request the FLOOR-
REQUEST-INFORMATION attribute applies to by filling the Floor Request
ID field of the FLOOR-REQUEST-INFORMATION attribute.
The floor control server MUST add FLOOR-ID attributes to the FLOOR-
REQUEST-INFORMATION grouped attribute identifying the floors being
requested (i.e., the floors associated with the floor request
identified by the FLOOR-REQUEST-ID attribute).
The floor control server SHOULD add a BENEFICIARY-ID attribute to the
FLOOR-REQUEST-INFORMATION grouped attribute identifying the
beneficiary of the floor request. Additionally, the floor control
server MAY provide the display name and the URI of the beneficiary in
this BENEFICIARY-INFORMATION attribute.
The floor control server MAY provide information about the requester
of the floor in a REQUESTED-BY-INFORMATION attribute inside the
FLOOR-REQUEST-INFORMATION grouped attribute.
The floor control server MAY provide the reason why the floor
participant requested the floor in a PARTICIPANT-PROVIDED-INFO.
The floor control server MAY also add to the FLOOR-REQUEST-
INFORMATION grouped attribute a PRIORITY attribute with the Priority
value requested for the floor request and a STATUS-INFO attribute
with extra information about the floor request.
The floor control server MUST add a REQUEST-STATUS attribute to the
FLOOR-REQUEST-INFORMATION grouped attribute with the current status
of the floor request.
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13.5.2 Generation of Subsequent FloorStatus Messages
If the FloorQuery message carried more than one FLOOR-ID attribute,
the floor control server SHOULD generate a FloorStatus message for
each of them (except for the FLOOR-ID attribute chosen for the first
FloorStatus message) as soon as possible. These FloorStatus messages
are generated following the same rules as for the first FloorStatus
message (see Section 13.5.1, but their Transaction ID is 0.
After generating these messages, the floor control server sends
FloorStatus messages periodically keeping the client informed about
all the floors the client requested information about. The
Transaction ID of these messages MUSt be 0.
The rate at which the floor control server sends FloorStatus
messages is a matter of local policy. A floor control server may
choose to send a new FloorStatus message every time a new floor
request arrives while another may choose to only send a new
FloorStatus message when a new floor request is Granted.
13.6 Reception of a ChairAction Message
On reception of a ChairAction message, the floor control server
follows the rules in Section 9 which relate to client authentication
and authorization. If while processing the ChairAction message, the
floor control server encounters an error, it SHOULD generate an Error
response following the procedures described in Section 13.8
The successful processing of a ChairAction message by a floor control
server involves generating a ChairActionAck message, which SHOULD be
generated as soon as possible.
The floor control server MUST copy the Conference ID, the Transaction
ID, and the User ID from the ChairAction message into the
ChairActionAck message, as described in Section 8.2.
The floor control server needs to take into consideration the
operation requested in the ChairAction message (e.g., granting a
floor), but does not necessarily need to perform it as requested by
the floor chair. The operation that the floor control server
performs depends on the ChairAction message and on the internal state
of the floor control server.
For example, a floor chair may send a ChairAction message granting a
floor which was requested as part of an atomic floor request
operation that involved several floors. Even if the chair
responsible for one of the floors instructs the floor control server
to grant the floor, the floor control server will not grant it until
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the chairs responsible for the other floors agree to grant them as
well.
So, the floor control server is ultimately responsible to keep a
coherent floor state using instructions from floor chairs as input to
this state.
If the new Status in the ChairAction message is Accepted and all the
bits of the Queue Position field are zero, the floor chair is
requesting the floor control server to assign a queue position (e.g.,
the last in the queue) to the floor request based on the local policy
of the floor control server. (Of course, such a request only applies
in case the floor control server implements a queue.)
13.7 Reception of a Hello Message
On reception of a Hello message, the floor control server follows the
rules in Section 9 which relate to client authentication. If while
processing the Hello message, the floor control server encounters an
error, it SHOULD generate an Error response following the procedures
described in Section 13.8
The successful processing of a Hello message by a floor control
server involves generating a HelloAck message, which SHOULD be
generated as soon as possible. The floor control server MUST copy
the Conference ID, the Transaction ID, and the User ID from the Hello
into the HelloAck, as described in Section 8.2.
The floor control server MUST add a SUPPORTED-PRIMITIVES attribute to
the HelloAck message listing all the primitives (i.e., BFCP messages)
supported by the floor control server.
The floor control server MUST add a SUPPORTED-ATTRIBUTES attribute to
the HelloAck message listing all the attributes supported by the
floor control server.
13.8 Error Message Generation
Error messages are always sent in response to a previous message from
the client as part of a client-initiated transaction. The ABNF in
Section 5.3.13 describes the attributes that an Error message can
contain. In addition, the ABNF specifies normatively which of these
attributes are mandatory, and which ones are optional.
The floor control server MUST copy the Conference ID, the Transaction
ID, and the User ID from the message from the client into the Error
message, as described in Section 8.2.
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The floor control server MUST add an ERROR-CODE attribute to the
Error message. The ERROR-CODE attribute contains an Error Code from
Table 6. Additionally, the floor control server may add a ERROR-INFO
attribute with extra information about the error.
14. Security Considerations
BFCP can use TLS or message signatures to provide client
authentication. Floor control server authentication is based on TLS,
which also provides replay and integrity protection, and
confidentiality. It is RECOMMENDED that TLS with non-null encryption
is always used and that the first message from an unauthenticated
client over a given TLS connection is signed using the DIGEST
attribute. Clients and floor control servers MAY use other security
mechanisms as long as they provide similar security properties.
The remainder of this Section analyzes some of the threats against
BFCP and how they are addressed.
An attacker may attempt to impersonate a client (a floor participant
or a floor chair) in order to generate forged floor requests or to
grant or deny existing floor requests. Client impersonation is
avoided by having clients sign their messages. A nonce is included
in the signature to ensure the freshness of the message. If the
client is using a TLS connection to communicate with the floor
control server, it is enough that the client signs its first message
over the TLS connection. The floor control server assumes that
attackers cannot hickjack the TLS connection and, therefore, that
subsequent messages over the TLS connection come from the client that
was initially authenticated. If TLS-based client authentication is
used, there is not need for the client to sign BFCP messages over the
connection.
An attacker may attempt to impersonate a floor control server. A
successful attacker would be able to make clients think that they
hold a particular floor so that they would try to access a resource
(e.g., sending media) without having legitimate rights to access it.
Floor control server impersonation is avoided by having floor control
servers present their server certificates or prove that they have a
shared secret with the client at TLS connection establishment time.
Attackers may attempt to modify messages exchanged by a client and a
floor control server. The integrity protection provided by TLS
connections prevents this attack.
An attacker may attempt to fetch a valid message sent by a client to
a floor control server and replay it at a later point. If the
message was signed, the attacker may attempt to establish a new TLS
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connection with the floor control server and replay the message over
the new connection. Using TLS confidentiality prevents this attack
because the attacker cannot access the contents of the message in the
first place. Additionally, TLS provides replay protection for a
given connection. Therefore, it is strongly RECOMMENDED that TLS is
used with a non-null encryption algorithm.
Attackers may attempt to pick messages from the network to get access
to confidential information between the floor control server and a
client (e.g., why a floor request was denied). TLS confidentiality
prevents this attack.
15. IANA Considerations
This document instructs the IANA to create a new registry for BFCP
parameters called "Binary Floor Control Protocol (BFCP) Parameters".
This new registry has a number of subregistries, which are described
in the following Sections
15.1 Attribute Subregistry
This Section establishes the Attribute subregistry under the BFCP
Parameters registry. As per the terminology in RFC 2434 [5], the
registration policy for BFCP attributes shall be "Specification
Required". For the purposes of this subregistry, the BFCP attributes
for which IANA registration is requested MUST be defined by a
standards-track RFC. Such RFC MUST specify the attribute's type,
name, format, and semantics.
For each BFCP attribute, the IANA registers its type, its name, and
the reference to the RFC where the attribute is defined. The
following table contains the initial values of this subregistry.
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+------+---------------------------+------------+
| Type | Attribute | Reference |
+------+---------------------------+------------+
| 1 | BENEFICIARY-ID | [RFC XXXX] |
| 2 | FLOOR-ID | [RFC XXXX] |
| 3 | FLOOR-REQUEST-ID | [RFC XXXX] |
| 4 | NONCE | [RFC XXXX] |
| 5 | PRIORITY | [RFC XXXX] |
| 6 | REQUEST-STATUS | [RFC XXXX] |
| 7 | DIGEST | [RFC XXXX] |
| 8 | ERROR-CODE | [RFC XXXX] |
| 9 | ERROR-INFO | [RFC XXXX] |
| 10 | PARTICIPANT-PROVIDED-INFO | [RFC XXXX] |
| 11 | STATUS-INFO | [RFC XXXX] |
| 12 | SUPPORTED-ATTRIBUTES | [RFC XXXX] |
| 13 | SUPPORTED-PRIMITIVES | [RFC XXXX] |
| 14 | USER-DISPLAY-NAME | [RFC XXXX] |
| 15 | USER-URI | [RFC XXXX] |
| 16 | BENEFICIARY-INFORMATION | [RFC XXXX] |
| 17 | FLOOR-REQUEST-INFORMATION | [RFC XXXX] |
| 18 | REQUESTED-BY-INFORMATION | [RFC XXXX] |
+------+---------------------------+------------+
Table 7: Initial values of the BFCP Attribute subregistry
15.2 Primitive Subregistry
This Section establishes the Primitive subregistry under the BFCP
Parameters registry. As per the terminology in RFC 2434 [5], the
registration policy for BFCP primitives shall be "Specification
Required". For the purposes of this subregistry, the BFCP primitives
for which IANA registration is requested MUST be defined by a
standards-track RFC. Such RFC MUST specify the primitive's value,
name, format, and semantics.
For each BFCP primitive, the IANA registers its value, its name, and
the reference to the RFC where the primitive is defined. The
following table contains the initial values of this subregistry.
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+-------+--------------------+------------+
| Value | Primitive | Reference |
+-------+--------------------+------------+
| 1 | FloorRequest | [RFC XXXX] |
| 2 | FloorRelease | [RFC XXXX] |
| 3 | FloorRequestQuery | [RFC XXXX] |
| 4 | FloorRequestStatus | [RFC XXXX] |
| 5 | UserQuery | [RFC XXXX] |
| 6 | UserStatus | [RFC XXXX] |
| 7 | FloorQuery | [RFC XXXX] |
| 8 | FloorStatus | [RFC XXXX] |
| 9 | ChairAction | [RFC XXXX] |
| 10 | ChairActionAck | [RFC XXXX] |
| 11 | Hello | [RFC XXXX] |
| 12 | HelloAck | [RFC XXXX] |
| 13 | Error | [RFC XXXX] |
+-------+--------------------+------------+
Table 8: Initial values of the BFCP primitive subregistry
15.3 Request Status Subregistry
This Section establishes the Request Status subregistry under the
BFCP Parameters registry. As per the terminology in RFC 2434 [5],
the registration policy for BFCP request status shall be
"Specification Required". For the purposes of this subregistry, the
BFCP request status for which IANA registration is requested MUST be
defined by a standards-track RFC. Such RFC MUST specify the value
and the semantics of the request status.
For each BFCP request status, the IANA registers its value, its
meaning, and the reference to the RFC where the request status is
defined. The following table contains the initial values of this
subregistry.
+-------+-----------+------------+
| Value | Status | Reference |
+-------+-----------+------------+
| 1 | Pending | [RFC XXXX] |
| 2 | Accepted | [RFC XXXX] |
| 3 | Granted | [RFC XXXX] |
| 4 | Denied | [RFC XXXX] |
| 5 | Cancelled | [RFC XXXX] |
| 6 | Released | [RFC XXXX] |
| 7 | Revoked | [RFC XXXX] |
+-------+-----------+------------+
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Table 9: Initial values of the Request Status subregistry
15.4 Error Code Subregistry
This Section establishes the Error Code subregistry under the BFCP
Parameters registry. As per the terminology in RFC 2434 [5], the
registration policy for BFCP error codes shall be "Specification
Required". For the purposes of this subregistry, the BFCP error
codes for which IANA registration is requested MUST be defined by a
standards-track RFC. Such RFC MUST specify the value and the
semantics of the error code, and any Error Specific Details that
apply to it.
For each BFCP primitive, the IANA registers its value, its meaning,
and the reference to the RFC where the primitive is defined. The
following table contains the initial values of this subregistry.
+----------------------+----------------------+---------------------+
| Value | Meaning | Reference |
+----------------------+----------------------+---------------------+
| 1 | Conference does not | [RFC XXXX] |
| | Exist | |
| 2 | User does not Exist | [RFC XXXX] |
| 3 | DIGEST Attribute | [RFC XXXX] |
| | Required | |
| 4 | Invalid Nonce | [RFC XXXX] |
| 5 | Authentication | [RFC XXXX] |
| | Failed | |
| 6 | Unknown Primitive | [RFC XXXX] |
| 7 | Unknown Mandatory | [RFC XXXX] |
| | Attribute | |
| 8 | Unauthorized | [RFC XXXX] |
| | Operation | |
| 9 | Invalid Floor ID | [RFC XXXX] |
| 10 | Floor Request ID | [RFC XXXX] |
| | Does Not Exist | |
| 11 | You have Already | [RFC XXXX] |
| | Reached the Maximum | |
| | Number of Ongoing | |
| | Floor Requests for | |
| | this Floor | |
+----------------------+----------------------+---------------------+
Table 10: Initial Values of the Error Code subregistry
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15.5 Digest Algorithm Subregistry
This Section establishes the Digest Algorithm subregistry under the
BFCP Parameters registry. As per the terminology in RFC 2434 [5],
the registration policy for BFCP digest algorithms shall be
"Specification Required". For the purposes of this subregistry, the
BFCP error codes for which IANA registration is requested MUST be
defined by a standards-track RFC. Such RFC MUST specify the value
and the semantics of the error code, and any Error Specific Details
that apply to it.
For each BFCP digest algorithm, the IANA registers its numeric
identifier, its name, and the reference to the RFC where the
algorithm is defined. The following table contains the initial
values of this subregistry.
+------------+-----------+-----------+
| Identifier | Algorithm | Reference |
+------------+-----------+-----------+
| 0 | HMAC-SHA1 | RFC 2104 |
+------------+-----------+-----------+
Table 11: Initial values of the Digest Algorithms subregistry
16. Acknowledgments
The XCON WG chairs, Adam Roach and Alan Johnston, provided useful
ideas for this document. Additionally, Xiaotao Wu, Paul Kyzivat,
Jonathan Rosenberg, Miguel A. Garcia-Martin, Mary Barnes, Ben
Campbell, Dave Morgan, and Oscar Novo provided useful comments.
17. References
17.1 Normative References
[1] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", RFC 2104, February 1997.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[4] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
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[5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[6] Chown, P., "Advanced Encryption Standard (AES) Ciphersuites for
Transport Layer Security (TLS)", RFC 3268, June 2002.
[7] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
STD 63, RFC 3629, November 2003.
17.2 Informational References
[8] 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.
[9] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002.
[10] Schulzrinne, H., "Requirements for Floor Control Protocol",
draft-ietf-xcon-floor-control-req-03 (work in progress),
January 2005.
[11] Rosenberg, J., "A Framework for Conferencing with the Session
Initiation Protocol",
draft-ietf-sipping-conferencing-framework-05 (work in
progress), May 2005.
[12] Barnes, M. and C. Boulton, "A Framework and Data Model for
Centralized Conferencing", draft-barnes-xcon-framework-02 (work
in progress), February 2005.
[13] Camarillo, G., "Session Description Protocol (SDP) Format for
Binary Floor Control Protocol (BFCP) Streams",
draft-ietf-mmusic-sdp-bfcp-01 (work in progress), May 2005.
Authors' Addresses
Gonzalo Camarillo
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: Gonzalo.Camarillo@ericsson.com
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Joerg Ott
Helsinki University of Technology
Department for Electrical and Communications Engineering
Networking Laboratory
Helsinki
Finland
Email: jo@netlab.hut.fi
Keith Drage
Lucent Technologies
Windmill Hill Business Park
Swindon
Wiltshire SN5 6PP
UK
Email: drage@lucent.com
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