Internet DRAFT - draft-pascual-dispatch-bfcp-websocket

draft-pascual-dispatch-bfcp-websocket






DISPATCH Working Group                                        V. Pascual
Internet-Draft                                               R. Welbourn
Updates: rfc4582bis, rfc4583bis                              Acme Packet
(if approved)                                                 S. Cazeaux
Intended status: Standards Track                   France Telecom Orange
Expires: August 19, 2013                               February 15, 2013


   The WebSocket Protocol as a Transport for the Binary Floor Control
                            Protocol (BFCP)
                draft-pascual-dispatch-bfcp-websocket-00

Abstract

   The WebSocket protocol enables two-way realtime communication between
   clients and servers.  This document specifies a new WebSocket sub-
   protocol as a reliable transport mechanism between Binary Floor
   Control Protocol (BFCP) entities to enable usage of BFCP in new
   scenarios.  This document normatively updates
   [I-D.draft-ietf-bfcpbis-rfc4582bis] and
   [I-D.draft-ietf-bfcpbis-rfc4583bis]

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on August 19, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  The WebSocket Protocol  . . . . . . . . . . . . . . . . . . . . 4
   4.  The WebSocket BFCP Sub-Protocol . . . . . . . . . . . . . . . . 5
     4.1.  Handshake . . . . . . . . . . . . . . . . . . . . . . . . . 5
     4.2.  BFCP encoding . . . . . . . . . . . . . . . . . . . . . . . 5
   5.  BFCP WebSocket Transport  . . . . . . . . . . . . . . . . . . . 6
   6.  Fields in the 'm' Line  . . . . . . . . . . . . . . . . . . . . 6
   7.  Authentication  . . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
     9.1.  Registration of the WebSocket BFCP Sub-Protocol . . . . . . 8
     9.2.  Registration of new SDP 'proto' Values  . . . . . . . . . . 8
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     11.1. Normative References  . . . . . . . . . . . . . . . . . . . 8
     11.2. Informative References  . . . . . . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9























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1.  Introduction

   The WebSocket [RFC6455] protocol enables two-way message exchange
   between clients and servers on top of a persistent TCP connection
   (optionally secured with TLS [RFC5246]).  The initial protocol
   handshake makes use of HTTP [RFC2616] semantics, allowing the
   WebSocket protocol to reuse existing HTTP infrastructure.

   The Binary Floor Control Protocol (BFCP) is a protocol to coordinate
   access to shared resources in a conference.  It is defined in
   [I-D.draft-ietf-bfcpbis-rfc4582bis] and is used between floor
   participants and floor control servers, and between floor chairs
   (i.e., moderators) and floor control servers.

   Modern web browsers include a WebSocket client stack complying with
   the WebSocket API [WS-API] as specified by the W3C. It is expected
   that other client applications (those running in personal computers
   and devices such as smartphones) will also make a WebSocket client
   stack available.  This document updates
   [I-D.draft-ietf-bfcpbis-rfc4582bis] and
   [I-D.draft-ietf-bfcpbis-rfc4583bis] in order to enable the usage of
   BFCP in these scenarios.

   The transport over which BFCP entities exchange messages depends on
   how the clients obtain information to contact the floor control
   server (e.g. using an SDP offer/answer exchange per
   [I-D.draft-ietf-bfcpbis-rfc4583bis] or the procedure described in
   RFC5018).  [I-D.draft-ietf-bfcpbis-rfc4582bis] defines two transports
   for BFCP: TCP and UDP.  This specification defines a new WebSocket
   sub-protocol (as defined in section 1.9 in [RFC6455]) for
   transporting BFCP messages between a WebSocket client and server, a
   new reliable and message boundary transport for BFCP.  In order to
   enable this, this document also defines two new SDP 'proto' values.


2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.1.  Definitions

   BFCP WebSocket Client:  A BFCP entity capable of opening outbound
         connections to WebSocket servers and communicating using the
         WebSocket BFCP sub-protocol as defined by this document.





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   BFCP WebSocket Server:  A BFCP entity capable of listening for
         inbound connections from WebSocket clients and communicating
         using the WebSocket BFCP sub-protocol as defined by this
         document.


3.  The WebSocket Protocol

   The WebSocket protocol [RFC6455] is a transport layer on top of TCP
   (optionally secured with TLS [RFC5246]) in which both client and
   server exchange message units in both directions.  The protocol
   defines a connection handshake, WebSocket sub-protocol and extensions
   negotiation, a frame format for sending application and control data,
   a masking mechanism, and status codes for indicating disconnection
   causes.

   The WebSocket connection handshake is based on HTTP [RFC2616] and
   utilizes the HTTP GET method with an "Upgrade" request.  This is sent
   by the client and then answered by the server (if the negotiation
   succeeded) with an HTTP 101 status code.  Once the handshake is
   completed the connection upgrades from HTTP to the WebSocket
   protocol.  This handshake procedure is designed to reuse the existing
   HTTP infrastructure.  During the connection handshake, client and
   server agree on the application protocol to use on top of the
   WebSocket transport.  Such an application protocol (also known as a
   "WebSocket sub-protocol") defines the format and semantics of the
   messages exchanged by the endpoints.  This could be a custom protocol
   or a standardized one (as the WebSocket BFCP sub-protocol defined in
   this document).  Once the HTTP 101 response is processed both client
   and server reuse the underlying TCP connection for sending WebSocket
   messages and control frames to each other.  Unlike plain HTTP, this
   connection is persistent and can be used for multiple message
   exchanges.

   The WebSocket protocol defines message units to be used by
   applications for the exchange of data, so it provides a message
   boundary-preserving transport layer.  These message units can contain
   either UTF-8 text or binary data, and can be split into multiple
   WebSocket text/binary transport frames as needed by the WebSocket
   stack.

      The WebSocket API [WS-API] for web browsers only defines callbacks
      to be invoked upon receipt of an entire message unit, regardless
      of whether it was received in a single Websocket frame or split
      across multiple frames.






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4.  The WebSocket BFCP Sub-Protocol

   The term WebSocket sub-protocol refers to an application-level
   protocol layered on top of a WebSocket connection.  This document
   specifies the WebSocket BFCP sub-protocol for carrying BFCP messages
   through a WebSocket connection.

4.1.  Handshake

   The BFCP WebSocket Client and BFCP WebSocket Server negotiate usage
   of the WebSocket BFCP sub-protocol during the WebSocket handshake
   procedure as defined in section 1.3 of [RFC6455].  The Client MUST
   include the value "bfcp" in the Sec-WebSocket-Protocol header in its
   handshake request.  The 101 reply from the Server MUST contain "bfcp"
   in its corresponding Sec-WebSocket-Protocol header.

   Below is an example of a WebSocket handshake in which the Client
   requests the WebSocket BFCP sub-protocol support from the Server:

     GET / HTTP/1.1
     Host: bfcp-ws.example.com
     Upgrade: websocket
     Connection: Upgrade
     Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
     Origin: http://www.example.com
     Sec-WebSocket-Protocol: bfcp
     Sec-WebSocket-Version: 13

   The handshake response from the Server accepting the WebSocket BFCP
   sub-protocol would look as follows:

     HTTP/1.1 101 Switching Protocols
     Upgrade: websocket
     Connection: Upgrade
     Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
     Sec-WebSocket-Protocol: bfcp

   Once the negotiation has been completed, the WebSocket connection is
   established and can be used for the transport of BFCP messages.  The
   WebSocket messages transmitted over this connection MUST conform to
   the negotiated WebSocket sub-protocol.

4.2.  BFCP encoding

   WebSocket messages can be transported in either UTF-8 text frames or
   binary frames.  BFCP messages use a TLV (Type-Length-Value) binary
   encoding, therefore BFCP WebSocket Clients and BFCP WebSocket Servers
   MUST use binary frames to exchange BFCP messages.  In addition, the



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   encoding rules for reliable protocols defined in
   [I-D.draft-ietf-bfcpbis-rfc4582bis] MUST be followed.


5.  BFCP WebSocket Transport

   WebSocket [RFC6455] is a reliable protocol and therefore the BFCP
   WebSocket sub-protocol defined by this document is a reliable BFCP
   transport.  Thus, client and server transactions using WebSocket for
   transport MUST follow the procedures for reliable transports as
   defined in [I-D.draft-ietf-bfcpbis-rfc4582bis] and
   [I-D.draft-ietf-bfcpbis-rfc4583bis]

   BFCP WebSocket clients cannot receive incoming WebSocket connections
   initiated by any other peer.  This means that a BFCP Websocket client
   MUST actively initiate a connection towards a BFCP Websocket server

   Each BFCP message MUST be carried within a single WebSocket message,
   and a WebSocket message MUST NOT contain more than one BFCP message.


6.  Fields in the 'm' Line

   Rules to generate an 'm' line for a BFCP stream are described in
   [I-D.draft-ietf-bfcpbis-rfc4583bis], Section 3

   New values are defined for the transport field: TCP/WS/BFCP and TCP/
   WSS/BFCP.

      TCP/WS/BFCP is used when BFCP runs on top of WS, which in turn
      runs on top of TCP

      TCP/WSS/BFCP is used when BFCP runs on top of WS, which in turn
      runs on top of TLS and TCP

   The following are examples of 'm' lines for BFCP connections:

   m=application 50000 TCP/WS/BFCP *
   m=application 50000 TCP/WSS/BFCP *


7.  Authentication

   Section 9 of [I-D.draft-ietf-bfcpbis-rfc4582bis] states that BFCP
   clients and floor control servers SHOULD authenticate each other
   prior to accepting messages, and RECOMMENDS that mutual TLS/DTLS
   authentication be used.  However, browser-based WebSocket clients
   have no control over the use of TLS in the WebSocket API [WS-API], so



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   it is RECOMMENDED that standard Web-based methods for client and
   server authentication are used, as follows.

   When a BFCP WebSocket client connects to a BFCP WebSocket server, it
   SHOULD use TCP/WSS as its transport.  The WebSocket client SHOULD
   inspect the TLS certificate offered by the server and verify that it
   is valid.

      Since the WebSocket API does not distinguish between certificate
      errors and other kinds of failure to establish a connection, it is
      expected that browser vendors will warn end users directly of any
      kind of problem with the server certificate.

   A floor control server that receives a message over TCP/WS can
   request the use of TCP/WSS by generating an Error message, as
   described in Section 13.8 of [I-D.draft-ietf-bfcpbis-rfc4582bis],
   with an Error code with a value of 9 (use TLS).

   Prior to sending BFCP requests, a BFCP WebSocket client connects to a
   BFCP WebSocket server and performs the connection handshake.  As
   described in Section 3 the handshake procedure involves a HTTP GET
   method request from the client and a response from the server
   including an HTTP 101 status code.

   In order to authorize the WebSocket connection, the BFCP WebSocket
   server MAY inspect any cookie [RFC6265] headers present in the HTTP
   GET request.  For many web applications the value of such a cookie is
   provided by the web server once the user has authenticated themselves
   to the web server, which could be done by many existing mechanisms.
   As an alternative method, the BFCP WebSocket Server could request
   HTTP authentication by replying to the Client's GET method request
   with a HTTP 401 status code.  The WebSocket protocol [RFC6455] covers
   this usage in section 4.1:

      If the status code received from the server is not 101, the
      WebSocket client stack handles the response per HTTP [RFC2616]
      procedures, in particular the client might perform authentication
      if it receives 401 status code.


8.  Security Considerations

   Considerations from [I-D.draft-ietf-bfcpbis-rfc4582bis],
   [I-D.draft-ietf-bfcpbis-rfc4583bis] and RFC5018 apply.

   BFCP relies on lower-layer security mechanisms to provide replay and
   integrity protection and confidentiality.  It is RECOMMENDED that the
   BFCP traffic transported over a WebSocket communication be protected



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   by using a secure WebSocket connection (using TLS [RFC5246] over
   TCP).


9.  IANA Considerations

9.1.  Registration of the WebSocket BFCP Sub-Protocol

   This specification requests IANA to register the WebSocket BFCP sub-
   protocol under the "WebSocket Subprotocol Name" Registry with the
   following data:

   Subprotocol Identifier:  bfcp

   Subprotocol Common Name:  WebSocket Transport for BFCP (Binary Floor
      Control Protocol)

   Subprotocol Definition:  TBD: this document

9.2.  Registration of new SDP 'proto' Values

   This document defines two new SDP 'proto' values (WS/BFCP and WSS/
   BFCP) and requests IANA to register these values under the "Session
   Description Protocol (SDP) Parameters" registry.  The resulting
   entries are as follows:

   Value                   Reference
   --------------           ---------
   TCP/WS/BFCP             [TBD: this document]
   TCP/WSS/BFCP            [TBD: this document]


10.  Acknowledgements

   TBC


11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4582]  Camarillo, G., Ott, J., and K. Drage, "The Binary Floor
              Control Protocol (BFCP)", RFC 4582, November 2006.

   [RFC4583]  Camarillo, G., "Session Description Protocol (SDP) Format



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              for Binary Floor Control Protocol (BFCP) Streams",
              RFC 4583, November 2006.

   [RFC5018]  Camarillo, G., "Connection Establishment in the Binary
              Floor Control Protocol (BFCP)", RFC 5018, September 2007.

   [RFC6455]  Fette, I. and A. Melnikov, "The WebSocket Protocol",
              RFC 6455, December 2011.

11.2.  Informative References

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC6265]  Barth, A., "HTTP State Management Mechanism", RFC 6265,
              April 2011.

   [WS-API]   W3C and I. Hickson, Ed., "The WebSocket API", May 2012.


Authors' Addresses

   Victor Pascual
   Acme Packet

   Email: vpascual@acmepacket.com


   Robert Welbourn
   Acme Packet

   Email: rwelbourn@acmepacket.com


   Stephane Cazeaux
   France Telecom Orange

   Email: stephane.cazeaux@orange.com









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