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Versions: 00 01 02 03 04 draft-ietf-rtcweb-data-protocol
RTCWeb Working Group R. Jesup
Internet-Draft Mozilla
Intended status: Standards Track S. Loreto
Expires: December 11, 2012 Ericsson
M. Tuexen
Muenster Univ. of Appl. Sciences
June 9, 2012
WebRTC Data Channel Protocol
draft-jesup-rtcweb-data-protocol-01.txt
Abstract
The Web Real-Time Communication (WebRTC) working group is charged to
provide protocols to support for direct interactive rich
communication using audio, video, and data between two peers' web-
browsers. This document specifies an actual (minor) protocol for how
the JS-layer dataChannel objects provide the data channels between
the peers.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on December 11, 2012.
Copyright Notice
Copyright (c) 2012 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
carefully, as they describe your rights and restrictions with respect
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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. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Opening Handshake . . . . . . . . . . . . . . . . . . . . . . . 3
5. Control Messages . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. DATA_CHANNEL_OPEN_REQUEST Message . . . . . . . . . . . . . 4
5.2. DATA_CHANNEL_OPEN_RESPONSE Message . . . . . . . . . . . . 5
5.3. DATA_CHANNEL_ACK Message . . . . . . . . . . . . . . . . . 6
6. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Adding a Channel . . . . . . . . . . . . . . . . . . . . . 6
6.2. Closing a Channel . . . . . . . . . . . . . . . . . . . . . 7
6.3. Sending and Receiving Data . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8
10.2. Informational References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
The Data Channel Protocol is designed to provide, in the WebRTC
context [I-D.ietf-rtcweb-overview], a generic transport service
allowing Web Browser to exchange generic data in a bidirectional peer
to peer fashion. As discussed in [I-D.ietf-rtcweb-data-channel] the
protocol uses Stream Control Transmission Protocol (SCTP) [RFC4960]
encapsulated on Datagram Transport Layer Security (DTLS) [RFC6347] as
described in [I-D.tuexen-tsvwg-sctp-dtls-encaps] to benefit from
their already standardized transport and security features.
2. Conventions
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].
3. Terminology
This document uses the following terms:
Association: An SCTP association.
Stream: A unidirectional stream of an SCTP association. It is
uniquely identified by a stream identifier.
Channel: A bidirectional channel consisting of two SCTP streams.
4. Opening Handshake
The opening handshake is based on the multimedia session description
exchange that happens between the browsers, typically through a Web
Server acting as the signaling service.
[I-D.ietf-mmusic-sctp-sdp] defines the protocol identifier, 'SCTP/
DTLS', and defines how to establish an SCTP association over DTLS
using the Session Description Protocol (SDP).
The SCTP association is created with the number of streams specified
by the application, and if not specified, then it SHOULD default to
16 streams.
It is recommended that additional streams be available dynamically
based on [RFC6525].
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5. Control Messages
Data Channel Control Messages are sent to manage opening
bidirectional channels. A DATA_CHANNEL_OPEN_REQUEST message is sent
on the Stream that is intended to be used to send in that direction,
and a response (DATA_CHANNEL_OPEN_RESPONSE) is sent back on the
Stream to be used for the other direction, with a
reverse_direction_stream entry holding the Stream number the
DATA_CHANNEL_OPEN_REQUEST was sent on. This allows association of
the Streams that define the bidirectional channel. Finally, a
DATA_CHANNEL_ACK is sent on the original Stream to complete the 3-way
handshake.
Errors are returned by setting the error field of the
DATA_CHANNEL_OPEN_RESPONSE message to a non-0 value. In this case
the original sender of DATA_CHANNEL_OPEN_REQUEST shall close the
channel.
5.1. DATA_CHANNEL_OPEN_REQUEST Message
This message is sent initially on the stream used for user messages
using the channel.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Channel Type | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reliability Parameter | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ /
| Label |
/ \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Message Type: 1 byte (unsigned integer)
This field holds the IANA defined message type for the the
DATA_CHANNEL_OPEN_REQUEST message. The suggested value of this
field for IANA is 0x00.
Channel Type: 1 byte (unsigned integer)
This field specifies the type of the channel to be opened:
DATA_CHANNEL_RELIABLE (0x00): The channel provides a reliable bi-
directional communication channel.
DATA_CHANNEL_RELIABLE_STREAM (0x01): TBD.
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DATA_CHANNEL_UNRELIABLE (0x02): TBD.
DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT (0x03): The channel provides
a partial reliable bi-directional Communication channel. User
messages will not be retransmitted more times than specified in
the Reliability Parameter.
DATA_CHANNEL_PARTIAL_RELIABLE_TIMED (0x04): The channel provides
a partial reliable bi-directional Communication channel. User
messages might not be transmitted or retransmitted after a
specified life-time given in milli-seconds in the Reliability
Parameter. This life-time starts when providing the user
message to the Javascript engine.
Flags: 2 bytes (unsigned integer)
This field contains the bitwise OR of the following flags:
DATA_CHANNEL_FLAG_OUT_OF_ORDER_ALLOWED (0x0001): If this flag is
set, the channel does not need to preserve the message
sequencing.
Reliability Parameter: 2 bytes (unsigned integer)
This field is ignored if a reliable channel is used. If a partial
reliable channel with limited number of retransmissions is used,
this field specifies the number of retransmissions. If a partial
reliable channel with limited lifetime is used, this field
specifies the maximum life-time in milli seconds.
Priority: 2 bytes (integer)
The priority of the channel.
Label: Variable Length (sequence of characters)
The name of the channel.
5.2. DATA_CHANNEL_OPEN_RESPONSE Message
This message is sent in response to an DATA_CHANNEL_OPEN_REQUEST
message on the stream used for user messages using the channel.
Messages with the error field set to non-0 values can be sent on any
stream; it is suggested that they be sent (if possible) on an unused
stream.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Error | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reverse Stream |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Message Type: 1 byte (unsigned integer)
This field holds the IANA defined message type for the the
DATA_CHANNEL_OPEN_RESPONSE message. The suggested value of this
field for IANA is 0x01.
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Error: 1 byte (unsigned integer)
TBD.
Flags: 2 bytes (unsigned integer)
TBD.
Reverse Stream: 2 bytes (unsigned integer)
The identifier for the incoming stream of the channel. The
corresponding DATA_CHANNEL_OPEN_REQUEST message was received on
this stream.
5.3. DATA_CHANNEL_ACK Message
This message is sent in response to an DATA_CHANNEL_OPEN_RESPONSE
message on the stream used for user messages using the channel.
Reception of this message tells the opener that the channel setup
handshake is complete.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type |
+-+-+-+-+-+-+-+-+
Message Type: 1 byte (unsigned integer)
This field holds the IANA defined message type for the the
DATA_CHANNEL_ACK message. The suggested value of this field for
IANA is 0x02.
6. Procedures
6.1. Adding a Channel
When one side wants to add a channel, it picks an unused outgoing
stream; if no unused streams are available a negotiation to increase
the number is done. It then sends a DATA_CHANNEL_OPEN_REQUEST
control message on the outgoing stream.
When an DATA_CHANNEL_OPEN_REQUEST is received on an incoming stream,
an unused outgoing stream is picked; if no unused streams are
available a negotiation to increase the number is done. A
DATA_CHANNEL_OPEN_RESPONSE message is sent on the outgoing stream,
with the Reverse Stream field set to the incoming stream the
DATA_CHANNEL_OPEN_REQUEST message came in on.
When a DATA_CHANNEL_OPEN_RESPONSE is received, the Reverse Stream
value is matched against all pending DATA_CHANNEL_OPEN_REQUEST
messages. If no match can be found, the DATA_CHANNEL_OPEN_RESPONSE
message SHOULD be ignored. If a match is found, then if the error
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value is 0 a DATA_CHANNEL_ACK message is sent on the originator's
outgoing Stream for the channel. If the error value is non-zero, the
open failed, and the originator SHOULD close down the originally-
selected outgoing stream and notify the application.
The channel_type and reliability_parameters fields of the
DATA_CHANNEL_OPEN_REQUEST message MUST be used to set up the reverse
side of the Data Channel so that both directions use the same
options. So both directions are either reliable or use the PR-SCTP
extension defined in [RFC3758] using the same policy and parameter.
6.2. Closing a Channel
Data Channels shall be closed by resetting the outgoing stream If an
incoming stream is reset by the peer, an corresponding outgoing
stream reset SHOULD be issued. If both streams of a channel are
reset, the channel is closed and the streams are available for reuse
for new channel opens.
6.3. Sending and Receiving Data
Data shall be sent using PPID's other than the Data Channel Control
PPID. These PPID's should be registered with IANA via (TBD). The
meaning of these data PPIDs and the format of the data shall be
specific to the usage of this protocol, and typically shall be
provided to the higher layers to allow proper decoding of the data.
For WebRTC, data PPID's for DOMStrings and binary data blobs shall be
created.
All data sent on a Data Channel in both directions MUST be sent over
the underlying Stream using the reliability defined when the Data
Channel was opened.
Data may be sent before the 3-way handshake is complete; if so it
must be sent with in-order delivery set in order to avoid race
conditions cause by a handshake message being lost. This is an
exception to the requirement to send all data using the channel
reliability settings.
It is recommended that message size be kept within certain bounds
(TBD).
7. Security Considerations
To be done.
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8. IANA Considerations
This document also defines three new SCTP Payload Protocol
Identifiers (PPIDs). RFC 4960 [RFC4960] creates the registry from
which these identifiers have been assigned. The following values
have been reserved:
WebRTC Control - #To Be Assigned
DOMString - #To Be Assigned
Binary Data - #To Be Assigned
9. Acknowledgments
The authors wish to thank ... for there invaluable comments.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
[RFC6525] Stewart, R., Tuexen, M., and P. Lei, "Stream Control
Transmission Protocol (SCTP) Stream Reconfiguration",
RFC 6525, February 2012.
[I-D.ietf-mmusic-sctp-sdp]
Loreto, S. and G. Camarillo, "Stream Control Transmission
Protocol (SCTP)-Based Media Transport in the Session
Description Protocol (SDP)", draft-ietf-mmusic-sctp-sdp-01
(work in progress), March 2012.
[I-D.tuexen-tsvwg-sctp-dtls-encaps]
Jesup, R., Loreto, S., Stewart, R., and M. Tuexen, "DTLS
Encapsulation of SCTP Packets for RTCWEB",
draft-tuexen-tsvwg-sctp-dtls-encaps-00 (work in progress),
March 2012.
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10.2. Informational References
[I-D.ietf-rtcweb-overview]
Alvestrand, H., "Overview: Real Time Protocols for Brower-
based Applications", draft-ietf-rtcweb-overview-03 (work
in progress), March 2012.
[I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "RTCWeb Datagram
Connection", draft-ietf-rtcweb-data-channel-00 (work in
progress), March 2012.
Authors' Addresses
Randell Jesup
Mozilla
US
Email: randell-ietf@jesup.org
Salvatore Loreto
Ericsson
Hirsalantie 11
Jorvas 02420
FI
Email: salvatore.loreto@ericsson.com
Michael Tuexen
Muenster University of Applied Sciences
Stegerwaldstrasse 39
Steinfurt 48565
DE
Email: tuexen@fh-muenster.de
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