XCON Working Group G. Camarillo Internet-Draft Ericsson Expires: July 1, 2005 J. Ott Universitaet Bremen K. Drage Lucent Technologies December 31, 2004 The Binary Floor Control Protocol (BFCP) draft-ietf-xcon-bfcp-03.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on July 1, 2005. Copyright Notice Copyright (C) The Internet Society (2004). 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, Camarillo, et al. Expires July 1, 2005 [Page 1] Internet-Draft BFCP December 2004 and media control -- that are realized by other protocols. 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 . . . . . . . . . . . . . . . . . . . . . . 8 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 Policy Enforcement . . . . . . . . . . . . . . . . . . . . 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 FIXED-HEADER Format . . . . . . . . . . . . . . . . . . . 14 5.2 Attribute Format . . . . . . . . . . . . . . . . . . . . . 15 5.2.1 FLOOR-ID . . . . . . . . . . . . . . . . . . . . . . . 17 5.2.2 USER-ID . . . . . . . . . . . . . . . . . . . . . . . 17 5.2.3 BENEFICIARY-ID . . . . . . . . . . . . . . . . . . . . 17 5.2.4 TRANSACTION-ID . . . . . . . . . . . . . . . . . . . . 18 5.2.5 FLOOR-REQUEST-ID . . . . . . . . . . . . . . . . . . . 18 5.2.6 HUMAN-READABLE-INFO . . . . . . . . . . . . . . . . . 18 5.2.7 DIGEST . . . . . . . . . . . . . . . . . . . . . . . . 19 5.2.8 REQUEST-STATUS . . . . . . . . . . . . . . . . . . . . 20 5.2.9 ERROR-CODE . . . . . . . . . . . . . . . . . . . . . . 21 5.2.10 USER-DISPLAY-NAME . . . . . . . . . . . . . . . . . 23 5.2.11 USER-URI . . . . . . . . . . . . . . . . . . . . . . 23 5.2.12 PRIORITY . . . . . . . . . . . . . . . . . . . . . . 23 5.2.13 NONCE . . . . . . . . . . . . . . . . . . . . . . . 23 5.2.14 SUPPORTED-TLVS . . . . . . . . . . . . . . . . . . . 24 5.3 Message Format . . . . . . . . . . . . . . . . . . . . . . 24 5.3.1 FloorRequest . . . . . . . . . . . . . . . . . . . . . 24 5.3.2 FloorRelease . . . . . . . . . . . . . . . . . . . . . 25 5.3.3 FloorRequestInfoWanted . . . . . . . . . . . . . . . . 25 5.3.4 FloorRequestInfo . . . . . . . . . . . . . . . . . . . 26 5.3.5 FloorInfoWanted . . . . . . . . . . . . . . . . . . . 26 5.3.6 FloorInfo . . . . . . . . . . . . . . . . . . . . . . 27 5.3.7 ChairAction . . . . . . . . . . . . . . . . . . . . . 27 5.3.8 ChairActionAck . . . . . . . . . . . . . . . . . . . . 28 5.3.9 Hello . . . . . . . . . . . . . . . . . . . . . . . . 28 5.3.10 HelloAck . . . . . . . . . . . . . . . . . . . . . . 28 Camarillo, et al. Expires July 1, 2005 [Page 2] Internet-Draft BFCP December 2004 5.3.11 Error . . . . . . . . . . . . . . . . . . . . . . . 29 6. Transport . . . . . . . . . . . . . . . . . . . . . . . . . 29 7. Lower-Layer Security . . . . . . . . . . . . . . . . . . . . 30 8. Protocol Transactions . . . . . . . . . . . . . . . . . . . 30 8.1 Client Behavior . . . . . . . . . . . . . . . . . . . . . 31 8.2 Server Behavior . . . . . . . . . . . . . . . . . . . . . 31 9. Authentication and Authorization . . . . . . . . . . . . . . 31 9.1 Client Behavior . . . . . . . . . . . . . . . . . . . . . 31 9.2 Floor Control Server Behavior . . . . . . . . . . . . . . 32 10. Floor Participant Operations . . . . . . . . . . . . . . . . 33 10.1 Requesting a Floor . . . . . . . . . . . . . . . . . . . 33 10.1.1 Sending a FloorRequest Message . . . . . . . . . . . 33 10.1.2 Receiving a Response . . . . . . . . . . . . . . . . 34 10.2 Cancelling a Floor Request and Releasing a Floor . . . . 35 10.2.1 Sending a FloorRelease Message . . . . . . . . . . . 35 10.2.2 Receiving a Response . . . . . . . . . . . . . . . . 36 11. Chair Operations . . . . . . . . . . . . . . . . . . . . . . 36 11.1 Sending a ChairAction Message . . . . . . . . . . . . . 36 11.2 Receiving a Response . . . . . . . . . . . . . . . . . . 37 12. General Client Operations . . . . . . . . . . . . . . . . . 38 12.1 Requesting Information about Floors . . . . . . . . . . 38 12.1.1 Sending a FloorInfoWanted Message . . . . . . . . . 38 12.1.2 Receiving a Response . . . . . . . . . . . . . . . . 38 12.2 Requesting Information about Floor Requests . . . . . . 39 12.2.1 Sending a FloorRequestInfoWanted Message . . . . . . 40 12.2.2 Receiving a Response . . . . . . . . . . . . . . . . 40 12.3 Obtaining the Capabilities of a Floor Control Server . . 41 12.3.1 Sending a Hello Message . . . . . . . . . . . . . . 41 12.3.2 Receiving Responses . . . . . . . . . . . . . . . . 41 13. Floor Control Server Operations . . . . . . . . . . . . . . 41 13.1 Reception of a FloorRequest Message . . . . . . . . . . 42 13.1.1 Generating the First FloorRequestInfo Message . . . 42 13.1.2 Generation of Subsequent FloorRequestInfo Messages . 43 13.2 Reception of a FloorRequestInfoWanted Message . . . . . 44 13.2.1 Information on a Single Floor Request . . . . . . . 44 13.2.2 Information on the Floor Requests Associated to a Participant . . . . . . . . . . . . . . . . . . . . 45 13.3 Reception of a FloorRelease Message . . . . . . . . . . 45 13.4 Reception of a FloorInfoWanted Message . . . . . . . . . 46 13.4.1 Generation of the First FloorInfo Message . . . . . 47 13.4.2 Generation of Subsequent FloorInfo Messages . . . . 47 13.5 Reception of a ChairAction Message . . . . . . . . . . . 48 13.6 Reception of a Hello Message . . . . . . . . . . . . . . 49 13.7 Error Message Generation . . . . . . . . . . . . . . . . 49 14. Security Considerations . . . . . . . . . . . . . . . . . . 49 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . 51 15.1 Attribute Subregistry . . . . . . . . . . . . . . . . . 51 15.2 Primitive Subregistry . . . . . . . . . . . . . . . . . 51 Camarillo, et al. Expires July 1, 2005 [Page 3] Internet-Draft BFCP December 2004 15.3 Request Status Subregistry . . . . . . . . . . . . . . . 52 15.4 Error Code Subregistry . . . . . . . . . . . . . . . . . 53 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 54 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 54 17.1 Normative References . . . . . . . . . . . . . . . . . . . 54 17.2 Informational References . . . . . . . . . . . . . . . . . 55 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 56 Intellectual Property and Copyright Statements . . . . . . . 57 Camarillo, et al. Expires July 1, 2005 [Page 4] Internet-Draft BFCP December 2004 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 [11] 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, FloorRequestInfo, 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 and 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. Camarillo, et al. Expires July 1, 2005 [Page 5] Internet-Draft BFCP December 2004 Conference Policy: The complete set of rules for a particular conference. It includes the membership policy, the media policy, and policies related to floors and the use of floor control protocols. There is an instance of conference policy for each conference. 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 [11]. Floor control complements other functions defined in the conferencing framework [12]. In particular, it is the conference policy that Camarillo, et al. Expires July 1, 2005 [Page 6] Internet-Draft BFCP December 2004 defines which media streams and applications are floor-controlled, who is/are the respective floor chair(s), and how access to the floor is managed. Furthermore, it is up to the media policy to define which (if any) impact on media stream handling (e.g. switching or mixing) assignment of a floor to a media participant has. 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 [13]. 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 Camarillo, et al. Expires July 1, 2005 [Page 7] Internet-Draft BFCP December 2004 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 [13]. The conference policy for a particular conference contains the floors of the conference and the resource or resources associated with each floor. For example, a conference may have two floors: one controlling who can talk at a particular time and another controlling who can write on a shared whiteboard. Floor creation and termination are also outside the scope of BFCP and are aspects of the conference policy as well. Consequently, the floor control server needs to stay up to date on changes on the conference policy (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 the user identifier. Clients can obtain this information in different ways. One is to use an offer/answer [10] exchange. How to use an SDP [8] offer/answer [10] exchange to obtain this information is described in [14]. 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 [10] exchange using SIP [9] 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 Camarillo, et al. Expires July 1, 2005 [Page 8] Internet-Draft BFCP December 2004 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 policy. 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 [10] exchange. How to use an offer/answer exchange to obtain these associations is described in [14]. 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. 3.5 Policy Enforcement 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. According to the definition in Section 2, the conference policy determines which media participants can actually use the resources in the conference. So, if the policy of a conference is to enforce floor control decisions, every change in the status of any floor needs to be reflected in the conference policy of the conference. For example, the mixer only accepts media from the user who holds the floor. 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 TLVs. The common header contains, among other information, a 32-bit conference identifier. Floor participants, media participants, and floor chairs are identified by a 16-bit user identifier, which is carried in a TLV. Camarillo, et al. Expires July 1, 2005 [Page 9] Internet-Draft BFCP December 2004 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 TLV. Server-initiated transactions consist of a single message, which has no TRANSACTION-ID TLV, from the floor control server to a client. 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 a USER-ID TLV, and the identity of the beneficiary of the floor, in third party floor requests, in a BENEFICIARY-ID TLV. 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 TLVs. 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 FloorRequestInfo messages, which provide information about the status of the floor request. The first FloorRequestInfo message is the response to the FloorRequest message from the client, and therefore carries the same TRANSACTION-ID TLV as the FloorRequest. Additionally, the first FloorRequestInfo message carries a FLOOR-REQUEST-ID TLV. Subsequent FloorRequestInfo messages related to the same floor request will carry the same FLOOR-REQUEST-ID TLV. 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 TLV as the first FloorRequestInfo Message from the floor control server. Camarillo, et al. Expires July 1, 2005 [Page 10] Internet-Draft BFCP December 2004 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 TLVs, of the TRANSACTION-ID and the FLOOR-REQUEST-ID TLVs. Floor Participant Floor Control Server |(1) FloorRequest | |TRANSACTION-ID: 123 | |USER-ID: 234 | |FLOOR-ID: 543 | |---------------------------------------------->| |(2) FloorRequestInfo | |TRANSACTION-ID: 123 | |USER-ID: 234 | |FLOOR-REQUEST-ID: 789 | |FLOOR-ID: 543 | |REQUEST-STATUS: Pending | |<----------------------------------------------| |(3) FloorRequestInfo | |USER-ID: 234 | |FLOOR-REQUEST-ID: 789 | |FLOOR-ID: 543 | |REQUEST-STATUS: Accepted (1st in Queue) | |<----------------------------------------------| |(4) FloorRequestInfo | |USER-ID: 234 | |FLOOR-REQUEST-ID: 789 | |FLOOR-ID: 543 | |REQUEST-STATUS: Granted | |<----------------------------------------------| |(5) FloorRelease | |TRANSACTION-ID: 154 | |USER-ID: 234 | |FLOOR-REQUEST-ID: 789 | |---------------------------------------------->| |(6) FloorRequestInfo | |TRANSACTION-ID: 154 | |USER-ID: 234 | |FLOOR-REQUEST-ID: 789 | |FLOOR-ID: 543 | |REQUEST-STATUS: Released | |<----------------------------------------------| Figure 2: Requesting and releasing a floor Camarillo, et al. Expires July 1, 2005 [Page 11] Internet-Draft BFCP December 2004 Figure 2 shows how a floor participant requests to be informed on the status of a floor. The first FloorInfo message from the floor control server is the response to the FloorInfoWanted message, and as such, carries the same TRANSACTION-ID TLV as the FloorInfoWanted message. Subsequent FloorInfo messages consist of server-initiated transactions, and therefore carry no TRANSACTION-ID TLV. FloorInfo message (2) indicates that there are currently two floor requests for the floor whose Floor ID is 543. FloorInfo 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. FloorInfo message (4) indicates that the floor request with Floor Request ID 635 has been granted. Floor Participant Floor Control Server |(1) FloorInfoWanted | |TRANSACTION-ID: 257 | |USER-ID: 234 | |FLOOR-ID: 543 | |---------------------------------------------->| |(2) FloorInfo | |TRANSACTION-ID: 257 | |USER-ID: 234 | |FLOOR-ID:543 | |FLOOR-REQUEST-ID: 764 | |FLOOR-ID: 543 | |BENEFICIARY-ID: 124 | |REQUEST-STATUS: Accepted (1st in Queue) | |FLOOR-REQUEST-ID: 635 | |BENEFICIARY-ID: 154 | |FLOOR-ID: 543 | |REQUEST-STATUS: Accepted (2nd in Queue) | |<----------------------------------------------| |(3) FloorInfo | |USER-ID: 234 | |FLOOR-ID:543 | |FLOOR-REQUEST-ID: 764 | |FLOOR-ID: 543 | |BENEFICIARY-ID: 124 | |REQUEST-STATUS: Granted | |FLOOR-REQUEST-ID: 635 | |BENEFICIARY-ID: 154 | |FLOOR-ID: 543 | |REQUEST-STATUS: Accepted (1st in Queue) | Camarillo, et al. Expires July 1, 2005 [Page 12] Internet-Draft BFCP December 2004 |<----------------------------------------------| |(4) FloorInfo | |USER-ID: 234 | |FLOOR-ID:543 | |FLOOR-REQUEST-ID: 635 | |BENEFICIARY-ID: 154 | |FLOOR-ID: 543 | |REQUEST-STATUS: Granted | |<----------------------------------------------| Figure 3: Obtaining status information about a floor FloorInfo messages contain information about the floor requests they carry. For example, FloorInfo 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. 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 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. Camarillo, et al. Expires July 1, 2005 [Page 13] Internet-Draft BFCP December 2004 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 an 8-byte fixed header followed by attributes. All the protocol values MUST be sent in network byte order. 5.1 FIXED-HEADER Format The following is the FIXED-HEADER format. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: FIXED-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: Camarillo, et al. Expires July 1, 2005 [Page 14] Internet-Draft BFCP December 2004 +-------+------------------------+-----------------------+ | Value | Primitive | Direction | +-------+------------------------+-----------------------+ | 0 | FloorRequest | P -> S | | 1 | FloorRelease | P -> S | | 2 | FloorRequestInfoWanted | P -> S ; Ch -> S | | 3 | FloorRequestInfo | P <- S ; Ch <- S | | 4 | FloorInfoWanted | P -> S ; Ch -> S | | 5 | FloorInfo | P <- S ; Ch <- S | | 6 | ChairAction | Ch -> S | | 7 | ChairActionAck | Ch <- S | | 8 | Hello | P -> S ; Ch -> S | | 9 | HelloAck | P <- S ; Ch <- S | | 10 | Error | P <- S ; Ch <- S | +-------+------------------------+-----------------------+ S: Floor Control Server P: Floor Participant Ch: Floor Chair Table 1: BFCP primitives Payload Length: this 16-bit field contains length of the message in 4-byte units excluding the fixed header. Conference ID: this 32-bit identifies the conference the message belongs to. 5.2 Attribute Format BFCP attributes are encoded in TLV (Type-Length-Value) format. TLVs are 32-bit aligned. Camarillo, et al. Expires July 1, 2005 [Page 15] Internet-Draft BFCP December 2004 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: TLV format Type: this 7-bit field contains the type of the attribute. The following attribute types are defined: +------+---------------------+ | Type | Attribute | +------+---------------------+ | 0 | FLOOR-ID | | 1 | USER-ID | | 2 | BENEFICIARY-ID | | 3 | TRANSACTION-ID | | 4 | FLOOR-REQUEST-ID | | 5 | HUMAN-READABLE-INFO | | 6 | DIGEST | | 7 | REQUEST-STATUS | | 8 | ERROR-CODE | | 9 | USER-DISPLAY-NAME | | 10 | USER-URI | | 11 | PRIORITY | | 12 | NONCE | | 13 | SUPPORTED-TLVS | +------+---------------------+ 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 Type, 'M' bit, and Length fields are included. Attribute Contents: the contents of the different TLVs are defined in the following sections. Camarillo, et al. Expires July 1, 2005 [Page 16] Internet-Draft BFCP December 2004 5.2.1 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 0 0|M|0 0 0 0 0 1 0 0| Floor ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: FLOOR-ID format Floor ID: this field contains a 16-bit value that uniquely identifies a floor within a conference. 5.2.2 USER-ID The following is the format of the USER-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| User ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: USER-ID format User ID: this field contains a 16-bit value that uniquely identifies a user within a conference. 5.2.3 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 1 0|M|0 0 0 0 0 1 0 0| Beneficiary ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: BENEFICIARY-ID format Beneficiary ID: this field contains a 16-bit value that uniquely identifies a user within a conference. Camarillo, et al. Expires July 1, 2005 [Page 17] Internet-Draft BFCP December 2004 5.2.4 TRANSACTION-ID The following is the format of the TRANSACTION-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 1|M|0 0 0 0 0 1 0 0| Transaction ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: TRANSACTION-ID format Transaction ID: this field contains a 16-bit value that allows users to match a given message with its response. 5.2.5 FLOOR-REQUEST-ID The following is the format of the FLOOR-REQUEST-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 1 0 0|M|0 0 0 0 0 1 0 0| Floor Request ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: FLOOR-REQUEST-ID format Floor Request ID: this field contains a 16-bit value that indentifies a floor request at the floor control server. 5.2.6 HUMAN-READABLE-INFO The following is the format of the HUMAN-READABLE-INFO attribute. Camarillo, et al. Expires July 1, 2005 [Page 18] Internet-Draft BFCP December 2004 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| Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | / Text / / +-+-+-+-+-+-+-+-+ | | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 12: HUMAN-READABLE-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 HUMAN-READABLE-INFO TLV, 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 HUMAN-READABLE-INFO TLV is 32-bit aligned. The Padding bits SHOULD be set to zero by the sender and MUST be ignored by the receiver. If the TLV is already 32-bit aligned, no padding is needed. 5.2.7 DIGEST The following is the format of the DIGEST attribute. Camarillo, et al. Expires July 1, 2005 [Page 19] Internet-Draft BFCP December 2004 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 1 1 0 0 0| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + + | | + HMAC-SHA1 + | | + + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 13: DIGEST format HMAC-SHA1: this 20-byte field contains an HMAC-SHA1 [1] of the BFCP message. Its calculation is described in Section 9. Padding: two bytes of padding added so that the contents of the HMAC-SHA1 TLV 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 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 1|M|0 0 0 0 0 1 0 0|Request Status |Queue Position | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 14: REQUEST-STATUS format Request Status: this 8-bit field contains the status of the request, as described in the following table. Camarillo, et al. Expires July 1, 2005 [Page 20] Internet-Draft BFCP December 2004 +-------+-----------+ | Value | Status | +-------+-----------+ | 0 | Pending | | 1 | Accepted | | 2 | Granted | | 3 | Denied | | 4 | Cancelled | | 5 | Released | | 6 | Revoked | +-------+-----------+ Table 3: 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 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. 5.2.9 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 15: ERROR-CODE format Error Code: this 16-bit field contains an error code from the following table. Camarillo, et al. Expires July 1, 2005 [Page 21] Internet-Draft BFCP December 2004 +---------------------------------+---------------------------------+ | Value | Meaning | +---------------------------------+---------------------------------+ | 0 | Conference does not Exist | | 1 | Authentication Failed | | 2 | Unknown Mandatory TLV | | 3 | Floor Request ID Does Not Exist | | 4 | Unauthorized Operation | | 5 | User does not Exist | | 6 | Invalid Nonce | | 7 | DIGEST TLV Required | | 8 | Invalid Floor ID | | 9 | You have Already Reached the | | | Maximum Number of Ongoing Floor | | | Requests for this Floor | +---------------------------------+---------------------------------+ Table 4: Error Code meaning Error Specific Details: Present only for certain Error Codes. In this document, only for Error Code 2 (Unknown Mandatory TLV). For Error Code 2, this field contains the Types of the TLVs (which were present in the message that triggered the Error message) that were unknown to the receiver, encoded as follows. 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 TLV Type | Unknown TLV Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Unknown TLV Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unknown TLV Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 16: Unknown TLVs format Padding: one, two, or three bytes of padding added so that the contents of the ERROR-CODE TLV is 32-bit aligned. If the TLV 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. Note all the Error Codes defined in this document but Error Code 2, result in a TLV which is already 32-bit aligned (i.e., no need of padding). Error Code 2 results in a TLV Camarillo, et al. Expires July 1, 2005 [Page 22] Internet-Draft BFCP December 2004 that may need 2 bytes of padding. 5.2.10 USER-DISPLAY-NAME The format of the USER-DISPLAY-NAME attribute is the same as the HUMAN-READABLE-INFO attribute (still, they have different attribute types). The Text field in the USER-DISPLAY-NAME attribute contains the name of the user. 5.2.11 USER-URI The format of the USER-URI attribute is the same as the HUMAN-READABLE-INFO attribute (still, they have different attribute types). The Text field in the USER-URI attribute contains the URI of the user. 5.2.12 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 1 0 1 1|M|0 0 0 0 0 1 0 0| Priority | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 17: PRIORITY format Priority: the higher the 8-bit value, the more priority is requested for a given floor request. Reserved: at this point, the 8 bits in the reserved field SHOULD be set to zero by the sender of the message and MUST be ignored by the receiver. 5.2.13 NONCE The following is the format of the NONCE attribute. Camarillo, et al. Expires July 1, 2005 [Page 23] Internet-Draft BFCP December 2004 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 | Nonce Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 18: NONCE format Nonce Value: this 16-bit field contains a nonce. 5.2.14 SUPPORTED-TLVS The following is the format of the SUPPORTED-TLVS 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 | Supported TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Supported TLV | Supported TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 19: SUPPORTED-TLVS format Supported TLV: these fields contain the Types of the TLVs that are supported by the floor control server. Padding: two bytes of padding added so that the contents of the SUPPORTED-TLVS TLV is 32-bit aligned. If the TLV 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. 5.3 Message Format This section contains the normative ABNF [3] of the BFCP messages. 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 Camarillo, et al. Expires July 1, 2005 [Page 24] Internet-Draft BFCP December 2004 FloorRequest message: FloorRequest = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) [BENEFICIARY-ID] *(FLOOR-ID) [HUMAN-READABLE-INFO] [PRIORITY] [NONCE] [DIGEST] Figure 20: 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 = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) (FLOOR-REQUEST-ID) [NONCE] [DIGEST] Figure 21: FloorRelease format 5.3.3 FloorRequestInfoWanted Floor participants and floor chairs request information about a floor request by sending a FloorRequestInfoWanted message to the floor control server. The following is the format of the FloorRequestInfoWanted message: Camarillo, et al. Expires July 1, 2005 [Page 25] Internet-Draft BFCP December 2004 FloorRequestInfoWanted = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) [BENEFICIARY-ID] [FLOOR-REQUEST-ID] [NONCE] [DIGEST] Figure 22: FloorRequestInfoWanted format 5.3.4 FloorRequestInfo The floor control server informs floor participants and floor chairs about the status of their floor requests by sending them FloorRequestInfo messages. The following is the format of the FloorRequestInfo message: FloorRequestInfo = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) [BENEFICIARY-ID] [USER-DISPLAY-NAME] [USER-URI] 1*( (FLOOR-REQUEST-ID) 1*(FLOOR-ID) [HUMAN-READABLE-INFO] [PRIORITY] (REQUEST-STATUS) ) [NONCE] Figure 23: FloorRequestInfo format 5.3.5 FloorInfoWanted Floor participants and floor chairs request information about a floor or floors by sending a FloorInfoWanted message to the floor control server. The following is the format of the FloorRequest message: Camarillo, et al. Expires July 1, 2005 [Page 26] Internet-Draft BFCP December 2004 FloorInfoWanted = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) *(FLOOR-ID) [NONCE] [DIGEST] Figure 24: FloorInfoWanted format 5.3.6 FloorInfo The floor control server informs floor participants and floor chairs about the status (e.g., the current holder) of a floor by sending them FloorInfo messages. The following is the format of the FloorInfo message: FloorInfo = (FIXED-HEADER) [TRANSACTION-ID] (USER-ID) [FLOOR-ID] *( (FLOOR-REQUEST-ID) [BENEFICIARY-ID] [USER-DISPLAY-NAME] [USER-URI] *(FLOOR-ID) [HUMAN-READABLE-INFO] [PRIORITY] (REQUEST-STATUS) ) [NONCE] Figure 25: FloorInfo format 5.3.7 ChairAction Floor chairs send instructions to floor control servers by sending ChairAction messages. The following is the format of the ChairAction message: Camarillo, et al. Expires July 1, 2005 [Page 27] Internet-Draft BFCP December 2004 ChairAction = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) 1*(FLOOR-ID) (FLOOR-REQUEST-ID) (REQUEST-STATUS) [HUMAN-READABLE-INFO] [NONCE] [DIGEST] Figure 26: ChairAction format 5.3.8 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 = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) [NONCE] Figure 27: ChairActionAck format 5.3.9 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 = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) [NONCE] [DIGEST] Figure 28: Hello format 5.3.10 HelloAck Floor control servers confirm that they are alive on reception of a Hello message by sending a HelloAck message. The following is the Camarillo, et al. Expires July 1, 2005 [Page 28] Internet-Draft BFCP December 2004 format of the HelloAck message: HelloAck = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) (SUPPORTED-TLVS) [NONCE] Figure 29: HelloAck format 5.3.11 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 = (FIXED-HEADER) (TRANSACTION-ID) (USER-ID) (ERROR-CODE) [NONCE] [HUMAN-READABLE-INFO] Figure 30: 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 TLVs. 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 Camarillo, et al. Expires July 1, 2005 [Page 29] Internet-Draft BFCP December 2004 reestablished. The way connection reestablishment is handled depends on how the client obtains information to contact the floor control server (e.g., using an offer/answer exchange [14]). 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 TLV 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, server-initiated transactions do not have Transaction IDs associated with them. Camarillo, et al. Expires July 1, 2005 [Page 30] Internet-Draft BFCP December 2004 8.1 Client Behavior A client starting a client-initiated transaction MUST set the Conference ID in the FIXED-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 TRANSACTION-ID TLV to a number 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 TLV, and the USER-ID TLV from the request received from the client into the response. Server-initiated transactions MUST NOT contain a TRANSACTION-ID TLV. 9. Authentication and Authorization BFCP uses the DIGEST TLV to provide client authentication. The DIGEST TLV contains an HMAC-SHA1 [1] of the BFCP message. The use of SHA1 implies that the length of the HMAC is 20 bytes. The text used as input to HMAC is the BFCP message, including the FIXED-HEADER, up to and including the TLV preceding the DIGEST TLV. This text is then padded with zeroes so as to be a multiple of 64 bytes. As a result, the DIGEST TLV MUST be the last attribute in any BFCP message. The key used as input to HMAC is the secret shared between the server and the user identified by the USER-ID TLV in the message. 9.1 Client Behavior Clients can authenticate floor control servers by checking the floor control server's certificate when the TLS connection is established between them. To achieve client authentication, a client needs to prove to the floor control server that the client can produce a DIGEST TLV 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 TLV in the message. The NONCE TLV is the second to last TLV in the message (the last one is the DIGEST TLV). The nonce to be places in the NONCE TLV by the client is typically provided by the floor control server in an Error response -- typically with Error Code 7 (DIGEST TLV Required) or 6 (Invalid Camarillo, et al. Expires July 1, 2005 [Page 31] Internet-Draft BFCP December 2004 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 [14]). 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 TLV and a DIGEST TLV to the first message it sends to the floor control server. Furthermore, if any client generates a message without a DIGEST TLV and receives an Error response with Error Code 7 (DIGEST TLV Required), the client SHOULD re-send the message with a DIGEST TLV and a NONCE TLV with the nonce received in the Error response. If after sending a message with a DIGEST TLV, a client receives an Error response with Error Code 6 (Invalid Nonce), the client SHOULD re-send the message using the new nonce received in the Error response. If the Error Code is 1 (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 TLV with this nonce and a DIGEST TLV to its next message to the floor control server. 9.2 Floor Control Server Behavior Before accepting any BFCP message, the floor control server SHOULD authenticate the client. If the floor control server receives a message without DIGEST TLV from an unauthenticated client, the floor control server responds with an Error message with Error Code 7 (DIGEST TLV Required). The floor control message MUST include a NONCE TLV with a nonce value that is unguessable by attackers. When a floor control server receives a BFCP message with a DIGEST TLV, it checks whether the NONCE TLV 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 6 (Invalid Nonce) with a new nonce in a NONCE TLV. If the nonce is valid, the floor control server calculates the HMAC-SHA1 [1] of the message excluding the DIGEST TLV. The key used as input to HMAC is the secret shared between the server and the user identified by the USER-ID TLV in the message. If the resulting value Camarillo, et al. Expires July 1, 2005 [Page 32] Internet-Draft BFCP December 2004 is the same as the one in the DIGEST TLV, authentication is considered successful. If the resulting value is different than the one in the DIGEST TLV, authentication is considered to have failed, in which case the server SHOULD return an Error message, as described in Section 13.7, with Error Code 1 (Authentication Failed). Messages from a client that cannot be authenticated MUST NOT be processed further. Floor control servers may include a NONCE TLV 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 BCFP message, the floor control server checks whether or not the client is authorized to perform the operation it 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 13.7, with an Error code with a value of 4 (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 TLVs that a FloorRequest message can contain. In addition, the ABNF specifies normatively which of these TLVs are mandatory, and which ones are optional. The floor participant sets the Conference ID in the FIXED-HEADER and the TRANSACTION-ID TLV following the rules given in Section 8.1. Additionally, the floor participant follows the rules in Section 9.1 which relate to the authentication of the message (i.e., to the DIGEST TLV). Camarillo, et al. Expires July 1, 2005 [Page 33] Internet-Draft BFCP December 2004 The floor participant must insert a USER-ID TLV, which 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 TLV) is not the participant that would eventually get the floor (i.e., a third party floor request), the sender SHOULD add a BENEFICIARY-ID TLV 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 USER-ID and in BENEFICIARY-ID TLVs. The floor participant must insert at least one FLOOR-ID TLV in the FloorRequest message. If the client inserts more than one FLOOR-ID TLVs, 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 HUMAN-READABLE-INFO TLV to state the reason why the floor or floors are being requested. The Text field in the HUMAN-READABLE-INFO TLV is intended for human consumption. The floor participant may request the server to handle the floor request with a certain priority using a PRIORITY TLV. 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 FloorRequestInfo messages. The floor participant obtains a Floor Request ID in a FLOOR-REQUEST-ID TLV in the first FloorRequestInfo message from the floor control server. Subsequent FloorRequestInfo messages from the floor control server regarding the same floor request will carry the same Floor Request ID as the initial FloorRequestInfo message. This way, the floor participant can associate subsequent incoming FloorRequestInfo messages with the ongoing floor request. The floor participant obtains information about the status of the floor request in the REQUEST-STATUS TLV of each of the FloorRequestInfo messages received from the floor control server. If the Request Status value is Granted, all the floors that were requested in the FloorRequest message have been granted. If the Camarillo, et al. Expires July 1, 2005 [Page 34] Internet-Draft BFCP December 2004 Request Status value is Denied, all the floors that were requested in the FloorRequest message have been denied. The HUMAN-READABLE-INFO TLV, if present, provides extra information which the floor participant MAY display to the user. A floor request is considered to be ongoing while it is in the Pending, Accepted, or Granted states. 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 TLVs that a FloorRelease message can contain. In addition, the ABNF specifies normatively which of these TLVs are mandatory, and which ones are optional. The floor participant sets the Conference ID in the FIXED-HEADER and the TRANSACTION-ID TLV following the rules given in Section 8.1. Additionally, the floor participant follows the rules in Section 9.1 which relate to the authentication of the message (i.e., to the DIGEST TLV). The floor participant must insert a USER-ID TLV, which 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. 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). Camarillo, et al. Expires July 1, 2005 [Page 35] Internet-Draft BFCP December 2004 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 FloorRequestInfo message, the Request Status value in the REQUEST-STATUS-TLV 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 FloorRequestInfo message from the server with a Request Status different from Cancelled or Released. In any case, such a FloorRequestInfo 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 5.3.7 describes the TLVs that a ChairAction message can contain. In addition, the ABNF specifies normatively which of these TLVs are mandatory, and which ones are optional. The floor chair sets the Conference ID in the FIXED-HEADER and the TRANSACTION-ID TLV following the rules given in Section 8.1. Additionally, the floor chair follows the rules in Section 9.1 which relate to the authentication of the message (i.e., to the DIGEST TLV). The floor chair must insert a USER-ID TLV, which will be used by the floor control server to 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 TLVs and the floor request is identified by a FLOOR-REQUEST-ID TLV, which are carried in the ChairAction Camarillo, et al. Expires July 1, 2005 [Page 36] Internet-Draft BFCP December 2004 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 TLV. 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 HUMAN-READABLE-INFO TLV to state the reason why the floor or floors are being accepted, granted, or revoked. The Text in the HUMAN-READABLE-INFO TLV 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. 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. Camarillo, et al. Expires July 1, 2005 [Page 37] Internet-Draft BFCP December 2004 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 FloorInfoWanted message to the floor control server. 12.1.1 Sending a FloorInfoWanted Message The ABNF in Section 5.3.5 describes the TLVs that a FloorInfoWanted message can contain. In addition, the ABNF specifies normatively which of these TLVs are mandatory, and which ones are optional. The client sets the Conference ID in the FIXED-HEADER and the TRANSACTION-ID TLV following the rules given in Section 8.1. Additionally, the client follows the rules in Section 9.1 which relate to the authentication and the protection of the integrity of the message (i.e., to the DIGEST TLV). The client must insert a USER-ID TLV, which 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 FloorInfoWanted 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 FloorInfoWanted message with no FLOOR-ID TLV. 12.1.2 Receiving a Response A message from the floor control server is considered to be a response to the FloorInfoWanted 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. On reception of the FloorInfoWanted message, the floor control server will respond with a FloorInfo message or with an Error message. If Camarillo, et al. Expires July 1, 2005 [Page 38] Internet-Draft BFCP December 2004 the response is a FloorInfo message, it will contain information about one of the floors the client requested information about. If the client did not include any FLOOR-ID TLV in its FloorInfoWanted message, the FloorInfo message from the floor control server will not include any either. FloorInfo messages which carry information about a floor contain a FLOOR-ID TLV that identifies the floor. After this TLV, FloorInfo messages contain information about existing (one or more) floor request that relate to that floor. The information about each particular floor request consist of a FLOOR-REQUEST-ID TLV that identifies the floor request followed by a set of TLVs that provide information about the floor request. After the first FloorInfo, the floor control server will continue sending FloorInfo 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 one or several floor requests by sending a FloorRequestInfoWanted 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 FloorRequestInfo 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 FloorRequestInfoWanted message to poll the floor control server for the status of the floor request. FloorRequestInfoWanted messages can also be used to request information on all the floor requests associated with a floor participant. 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 the floor participant. Camarillo, et al. Expires July 1, 2005 [Page 39] Internet-Draft BFCP December 2004 12.2.1 Sending a FloorRequestInfoWanted Message The ABNF in Section 5.3.3 describes the TLVs that a FloorRequestInfoWanted message can contain. In addition, the ABNF specifies normatively which of these TLVs are mandatory, and which ones are optional. The client sets the Conference ID in the FIXED-HEADER and the TRANSACTION-ID TLV following the rules given in Section 8.1. Additionally, the client follows the rules in Section 9.1 which relate to the authentication of the message (i.e., to the DIGEST TLV). The client must insert a USER-ID TLV, which will be used by the floor control server to authenticate and authorize the request. If the client wants to request the status of a single floor request, it MUST insert a FLOOR-REQUEST-ID TLV that identifies the floor request at the floor control server. The client can also request information about all the ongoing floor requests associated with a particular participant. In this case, the client MUST NOT insert a FLOOR-REQUEST-ID TLV. If the beneficiary of the floor requests the client is requesting information about is not the client issuing the FloorRequestInfoWanted message (which is identified by the USER-ID TLV in the message) the client MUST insert a BENEFICIARY-ID TLV. 12.2.2 Receiving a Response A message from the floor control server is considered to be a response to the FloorRequestInfoWanted message if the message from the floor control server has the same Conference ID, Transaction ID,a nd User ID as the FloorRequestInfoWanted message, as described in Section 8.1. If the response is a FloorRequestInfo message, the client obtains information about the status of the FloorRequest the client requested information about in a REQUEST-STATUS TLVs. If the client requested information about several floor requests, the FloorRequestInfo message will carry several FLOOR-REQUEST-ID TLVs. Each FLOOR-REQUEST-ID TLV will be followed by TLVs (which will include a REQUEST-STATUS TLV) providing information about the floor request identified by the FLOOR-REQUEST-ID TLV. If the response is an Error message, the floor control server could not process the FloorRequestInfoWanted message for some reason, which is described in the Error message. Camarillo, et al. Expires July 1, 2005 [Page 40] Internet-Draft BFCP December 2004 12.3 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. 12.3.1 Sending a Hello Message The ABNF in Section 5.3.9 describes the TLVs that a Hello message can contain. In addition, the ABNF specifies normatively which of these TLVs are mandatory, and which ones are optional. The client sets the Conference ID in the FIXED-HEADER and the TRANSACTION-ID TLV following the rules given in Section 8.1. Additionally, the client follows the rules in Section 9.1 which relate to the authentication and the protection of the integrity of the message (i.e., to the DIGEST TLV). The client must insert a USER-ID TLV, which will be used by the floor control server to authenticate and authorize the request. 12.3.2 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-TLVS TLV indicates which TLVs 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 13.7, with Error code 0 (Conference does not Exist). On reception of a message from a client, the floor control server Camarillo, et al. Expires July 1, 2005 [Page 41] Internet-Draft BFCP December 2004 follows the rules in Section 9.2, 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) TLVs in the message. If the floor control server does not understand all of them, the floor control server SHOULD send an Error message, as described in Section 13.7, with Error code 2 (Authentication Failed). The Error message SHOULD list the TLVs 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 9.2 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 13.7 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 9 (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 FloorRequestInfo Message The successful processing of a FloorRequest message by a floor control server involves generating one or several FloorRequestInfo 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 TLV of the first FloorRequestInfo 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 copies the Conference ID, the TRANSACTION-ID, and the USER-ID TLVs from the FloorRequest into the FloorRequestInfo, as described in Section 8.2. Additionally, the Camarillo, et al. Expires July 1, 2005 [Page 42] Internet-Draft BFCP December 2004 floor control server copies (if present) the BENEFICIARY-ID TLV from the FloorRequest into the FloorRequestInfo. The floor control server MUST assign an identitifier that is unique within the conference to this floor request, and insert it in a FLOOR-REQUEST-ID TLV into the FloorRequestInfo message. This indentifier 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 copies the FLOOR-ID TLVs from the FloorRequest into the FloorRequestInfo. These FLOOR-ID TLVs identify the floors being requested (i.e., the floors associated with this particular floor request). The floor control server also copies (if present) the PRIORITY TLV from the FloorRequest into the FloorRequestInfo. The Priority value requested by the floor participant is only a hint, and does not necessarily need to be taken into consideration to decide whether to grant or not the floor request. 13.1.2 Generation of Subsequent FloorRequestInfo 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 TLV of the first FloorRequestInfo message generated by the floor control server did not indicate any of these states, the floor control server will need to send subsequent FloorRequestInfo messages. When the status of the floor request changes, the floor control floor control server SHOULD send new FloorRequestInfo messages with the appropriate Request Status. These FloorRequestInfo messages MUST contain a FLOOR-REQUEST-ID TLV equal to the one sent in the first FloorRequestInfo message, but MUST NOT contain any TRANSACTION-ID TLV. (The Floor Request ID identifies the floor request the FloorRequestInfo applies to.) The FIXED-HEADER and the rest of the TLVs (except for the HUMAN-READABLE-INFO TLV) are the same as in the first FloorRequestInfo message. The rate at which the floor control server sends FloorRequestInfo messages is a matter of local policy. A floor control server may choose to send a new FloorRequestInfo message every time the floor request moves in the floor request queue while another may choose to only send a new FloorRequestInfo message when the floor request is Granted or Denied. Camarillo, et al. Expires July 1, 2005 [Page 43] Internet-Draft BFCP December 2004 The floor control server may add a HUMAN-READABLE-INFO TLV to any of the FloorRequestInfo 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 13.4 to inform the clients that have requested that information 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 FloorRequestInfoWanted Message On reception of a FloorRequestInfoWanted message, the floor control server follows the rules in Section 9.2 which relate to client authentication and authorization. If while processing the FloorRequestInfoWanted message, the floor control server encounters an error, it SHOULD generate an Error response following the procedures described in Section 13.7 The successful processing of a FloorRequestInfoWanted message by a floor control server involves generating a FloorRequestInfo message, which SHOULD be generated as soon as possible. The floor control server copies the Conference ID, the TRANSACTION-ID, and the USER-ID TLVs from the FloorRequestInfoWanted message into the FloorRequestInfo message, as described in Section 8.2. 13.2.1 Information on a Single Floor Request If the FloorRequestInfoWanted message carries a FLOOR-REQUEST-ID, the sender of the message is requesting information about the floor request identified by the FLOOR-REQUEST-ID TLV. The floor control server copies the FLOOR-REQUEST-ID TLV from the FloorRequestInfoWanted message into the FloorRequestInfo message. The floor control server adds FLOOR-ID TLVs to the FloorRequestInfo message identifying the floors being requested (i.e., the floors associated with the floor request identified by the FLOOR-REQUEST-ID TLV). Camarillo, et al. Expires July 1, 2005 [Page 44] Internet-Draft BFCP December 2004 The floor control server may also add a PRIORITY TLV with the Priority value requested for the floor request and a HUMAN-READABLE-INFO TLV with extra information about the floor request. The floor control server adds a REQUEST-STATUS TLV with the current status of the floor request. 13.2.2 Information on the Floor Requests Associated to a Participant If the FloorRequestInfoWanted message does not carry a FLOOR-REQUEST-ID TLV, the sender of the message is requesting information about all the floor requests from a given participant. This participant is identified by a BENEFICIARY-ID TLV or, in the absence of a BENEFICIARY-ID TLV, by a USER-ID TLV. The floor control server copies (if present) the BENEFICIARY-ID TLV from the FloorRequestInfoWanted message into the FloorRequestInfo message. Additionally, the floor control server may provide extra information about the participant by adding a USER-DISPLAY-NAME TLV, a USER-URI TLV, or both to the FloorRequestInfo message. The floor control server adds a FLOOR-REQUEST-ID TLV for each floor request associated to the participant. Each FLOOR-REQUEST-ID TLV is followed by a number of TLVs which provide information about the floor request. The floor control server generates the TLVs that follow each FLOOR-REQUEST-ID following the rules in Section 13.2.1 13.3 Reception of a FloorRelease Message On reception of a FloorRelease message, the floor control server follows the rules in Section 9.2 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 13.7 The successful processing of a FloorRelease message by a floor control server involves generating a FloorRequestInfo message, which SHOULD be generated as soon as possible. The floor control server copies the Conference ID, the TRANSACTION-ID, and the USER-ID TLVs from the FloorRelease message into the FloorRequestInfo message, as described in Section 8.2. The FloorRelease message identifies the floor request it applies to using a FLOOR-REQUEST-ID. If the beneficiary of the floor request is not the participant identified by the USER-ID TLV in the FloorRelease Camarillo, et al. Expires July 1, 2005 [Page 45] Internet-Draft BFCP December 2004 message, the floor control server adds a BENEFICIARY-ID TLV to the FloorRequestInfo message identifying the beneficiary of the floor request. Additionally, the floor control server may provide extra information about the beneficiary of the floor request by adding a USER-DISPLAY-NAME TLV, a USER-URI TLV, or both to the FloorRequestInfo message. The floor control server copies the FLOOR-REQUEST-ID TLV from the FloorRelease message into the FloorRequestInfo message. The floor control server adds FLOOR-ID TLVs to the FloorRequestInfo message identifying the floors being requested (i.e., the floors associated with the floor request identified by the FLOOR-REQUEST-ID TLV). The floor control server may also add a PRIORITY TLV with the Priority value requested for the floor request and a HUMAN-READABLE-INFO TLV with extra information about the floor request. The floor control server adds a REQUEST-STATUS TLV to the FloorRequestInfo message. The Request Status value SHOULD be Released, if the floor (or floors) had been previously granted, or of Cancelled, if the floor (or floors) had not been previously granted. 13.4 Reception of a FloorInfoWanted Message On reception of a FloorInfoWanted message, the floor control server follows the rules in Section 9.2 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 13.7 A floor control server receiving a FloorInfoWanted message from a client SHOULD keep this client informed about the status of the floors identified by FLOOR-ID TLVs in the FloorInfoWanted message. Floor Control Servers keep clients informed by using FloorInfo messages. An individual FloorInfo message carries information about a single floor. So, when a FloorInfoWanted message requests information about more than one floor, the floor control server needs to send separate FloorInfo messages for different floors. The information FloorInfoWanted 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. Camarillo, et al. Expires July 1, 2005 [Page 46] Internet-Draft BFCP December 2004 13.4.1 Generation of the First FloorInfo Message The successful processing of a FloorInfoWanted message by a floor control server involves generating one or several FloorInfo messages, the first of which SHOULD be generated as soon as possible. The floor control server copies the Conference ID, the TRANSACTION-ID, and the USER-ID TLVs from the FloorInfoWanted message into the FloorInfo message, as described in Section 8.2. If the FloorInfoWanted message did not contain any FLOOR-ID TLV, the floor control server sends the FloorInfo message without adding any additional TLV and does not send any subsequent FloorInfo message to the floor participant. If the FloorInfoWanted message contained one or more FLOOR-ID TLVs, the floor control server chooses one among them and adds this FLOOR-ID TLV to the FloorInfo message. The floor control server adds a FLOOR-REQUEST-ID TLV for each floor request associated to the floor. Each FLOOR-REQUEST-ID TLV is followed by a number of TLVs which provide information about the floor request. For each FLOOR-REQUEST-ID TLV, the floor control server may add a BENEFICIARY-ID TLV identifying the requester of the floor and a USER-DISPLAY-NAME TLV, a USER-URI TLV, or both providing information about the requester. Additionally, the floor control server adds FLOOR-ID TLVs to the FloorInfo message identifying the floors being requested (i.e., the floors associated with the floor request identified by the FLOOR-REQUEST-ID TLV). The floor control server may also add a PRIORITY TLV with the Priority value requested for the floor request and a HUMAN-READABLE-INFO TLV with extra information about the floor request. The floor control server adds a REQUEST-STATUS TLV with the current status of the floor request. 13.4.2 Generation of Subsequent FloorInfo Messages If the FloorInfoWanted message carried more than one FLOOR-ID TLV, the floor control server SHOULD generate a FloorInfo message for each of them (except for the FLOOR-ID TLV chosen for the first FloorInfo message) as soon as possible. These FloorInfo messages are generated following the same rules as for the first FloorInfo message (see Section 13.4.1, but without adding a TRANSACTION TLV. After generating these messages, the floor control server sends Camarillo, et al. Expires July 1, 2005 [Page 47] Internet-Draft BFCP December 2004 FloorInfo messages periodically keeping the client informed about all the floors the client requested information about. These messages MUST NOT carry a TRANSACTION-ID TLV. The rate at which the floor control server sends FloorInfo messages is a matter of local policy. A floor control server may choose to send a new FloorInfo message every time a new floor request arrives while another may choose to only send a new FloorInfo message when a new floor request is Granted. 13.5 Reception of a ChairAction Message On reception of a ChairAction message, the floor control server follows the rules in Section 9.2 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 13.7 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 copies the Conference ID, the TRANSACTION-ID, and the USER-ID TLVs 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 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 Camarillo, et al. Expires July 1, 2005 [Page 48] Internet-Draft BFCP December 2004 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.) 13.6 Reception of a Hello Message On reception of a Hello message, the floor control server follows the rules in Section 9.2 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 13.7 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 copies the Conference ID, the TRANSACTION-ID, and the USER-ID TLVs from the Hello into the HelloAck, as described in Section 8.2. The floor control server adds a SUPPORTED-TLVS TLV to the HelloAck message listing all the TLVs supported by the floor control server. 13.7 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 5.3.11 describes the TLVs that an Error message can contain. In addition, the ABNF specifies normatively which of these TLVs are mandatory, and which ones are optional. The floor control server copies the Conference ID, the TRANSACTION-ID, and the USER-ID TLVs from the message from the client into the Error message, as described in Section 8.2. The floor control server adds an ERROR-CODE TLV to the Error message. The ERROR-CODE TLV contains an Error Code from Table 4. Additionally, the floor control server may add a HUMAN-READABLE-INFO TLV with extra information about the error. 14. Security Considerations BFCP uses message signatures to provide client authentication and TLS to provide floor control server authentication, replay and integrity protection, and confidentiality. It is RECOMMENDED that TLS with non-null encryption is always used and that the first message from a client over a given TLS connection is signed using the DIGEST TLV. In any case, clients and floor control servers MAY use other security mechanisms as long as they provide similar security properties. Camarillo, et al. Expires July 1, 2005 [Page 49] Internet-Draft BFCP December 2004 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. 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 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 attacker attempts to replay it over the TLS connection between the client and the floor control server, TLS mechanisms discard it at the receiver side. Still, if the message was signed, the attacker may attempt to establish a new TLS 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, if the attacker attempts to replay the encrypted message over the new connection, TLS mechanisms would discard it at the receiver side. 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. Camarillo, et al. Expires July 1, 2005 [Page 50] Internet-Draft BFCP December 2004 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. +------+---------------------+------------+ | Type | Attribute | Reference | +------+---------------------+------------+ | 0 | FLOOR-ID | [RFC XXXX] | | 1 | USER-ID | [RFC XXXX] | | 2 | BENEFICIARY-ID | [RFC XXXX] | | 3 | TRANSACTION-ID | [RFC XXXX] | | 4 | FLOOR-REQUEST-ID | [RFC XXXX] | | 5 | HUMAN-READABLE-INFO | [RFC XXXX] | | 6 | DIGEST | [RFC XXXX] | | 7 | REQUEST-STATUS | [RFC XXXX] | | 8 | ERROR-CODE | [RFC XXXX] | | 9 | USER-DISPLAY-NAME | [RFC XXXX] | | 10 | USER-URI | [RFC XXXX] | | 11 | PRIORITY | [RFC XXXX] | | 12 | NONCE | [RFC XXXX] | | 13 | SUPPORTED-TLVS | [RFC XXXX] | +------+---------------------+------------+ Table 5: 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 Camarillo, et al. Expires July 1, 2005 [Page 51] Internet-Draft BFCP December 2004 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. +-------+------------------------+------------+ | Value | Primitive | Reference | +-------+------------------------+------------+ | 0 | FloorRequest | [RFC XXXX] | | 1 | FloorRelease | [RFC XXXX] | | 2 | FloorRequestInfoWanted | [RFC XXXX] | | 3 | FloorRequestInfo | [RFC XXXX] | | 4 | FloorInfoWanted | [RFC XXXX] | | 5 | FloorInfo | [RFC XXXX] | | 6 | ChairAction | [RFC XXXX] | | 7 | ChairActionAck | [RFC XXXX] | | 8 | Hello | [RFC XXXX] | | 9 | HelloAck | [RFC XXXX] | | 10 | Error | [RFC XXXX] | +-------+------------------------+------------+ Table 6: 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. Camarillo, et al. Expires July 1, 2005 [Page 52] Internet-Draft BFCP December 2004 +-------+-----------+------------+ | Value | Status | Reference | +-------+-----------+------------+ | 0 | Pending | [RFC XXXX] | | 1 | Accepted | [RFC XXXX] | | 2 | Granted | [RFC XXXX] | | 3 | Denied | [RFC XXXX] | | 4 | Cancelled | [RFC XXXX] | | 5 | Released | [RFC XXXX] | | 6 | Revoked | [RFC XXXX] | +-------+-----------+------------+ Table 7: 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. Camarillo, et al. Expires July 1, 2005 [Page 53] Internet-Draft BFCP December 2004 +----------------------+----------------------+---------------------+ | Value | Meaning | Reference | +----------------------+----------------------+---------------------+ | 0 | Conference does not | [RFC XXXX] | | | Exist | | | 1 | Authentication | [RFC XXXX] | | | Failed | | | 2 | Unknown Mandatory | [RFC XXXX] | | | TLV | | | 3 | Floor Request ID | [RFC XXXX] | | | Does Not Exist | | | 4 | Unauthorized | [RFC XXXX] | | | Operation | | | 5 | User does not Exist | [RFC XXXX] | | 6 | Invalid Nonce | [RFC XXXX] | | 7 | DIGEST TLV Required | [RFC XXXX] | | 8 | Invalid Floor ID | [RFC XXXX] | | 9 | You have Already | [RFC XXXX] | | | Reached the Maximum | | | | Number of Ongoing | | | | Floor Requests for | | | | this Floor | | +----------------------+----------------------+---------------------+ Table 8: Initial Values of the Error Code 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, and Miguel A. Garcia-Martin 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. 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 Camarillo, et al. Expires July 1, 2005 [Page 54] Internet-Draft BFCP December 2004 2246, January 1999. [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] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998. [9] 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. [10] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002. [11] Schulzrinne, H., "Requirements for Floor Control Protocol", draft-ietf-xcon-floor-control-req-02 (work in progress), October 2004. [12] Rosenberg, J., "A Framework for Conferencing with the Session Initiation Protocol", draft-ietf-sipping-conferencing-framework-03 (work in progress), October 2004. [13] Barnes, M. and C. Boulton, "A Framework for Centralized Conferencing", draft-barnes-xcon-framework-00 (work in progress), October 2004. [14] Camarillo, G., "Session Description Protocol (SDP) Format for Binary Floor Control Protocol (BFCP) Streams", draft-camarillo-mmusic-sdp-bfcp-00 (work in progress), April 2005. Camarillo, et al. Expires July 1, 2005 [Page 55] Internet-Draft BFCP December 2004 Authors' Addresses Gonzalo Camarillo Ericsson Hirsalantie 11 Jorvas 02420 Finland EMail: Gonzalo.Camarillo@ericsson.com Joerg Ott Universitaet Bremen MZH 5180 Bibliothekstr. 1 Bremen D-28359 Germany EMail: jo@tzi.org Keith Drage Lucent Technologies Windmill Hill Business Park Swindon Wiltshire SN5 6PP UK EMail: drage@lucent.com Camarillo, et al. 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