draft-ietf-rtcweb-data-channel-02.txt   draft-ietf-rtcweb-data-channel-03.txt 
Network Working Group R. Jesup Network Working Group R. Jesup
Internet-Draft Mozilla Internet-Draft Mozilla
Intended status: Standards Track S. Loreto Intended status: Standards Track S. Loreto
Expires: April 26, 2013 Ericsson Expires: August 28, 2013 Ericsson
M. Tuexen M. Tuexen
Muenster Univ. of Appl. Sciences Muenster Univ. of Appl. Sciences
October 23, 2012 February 24, 2013
RTCWeb Datagram Connection RTCWeb Data Channels
draft-ietf-rtcweb-data-channel-02.txt draft-ietf-rtcweb-data-channel-03.txt
Abstract Abstract
The Web Real-Time Communication (WebRTC) working group is charged to The Web Real-Time Communication (WebRTC) working group is charged to
provide protocol support for direct interactive rich communication provide protocol support for direct interactive rich communication
using audio, video, and data between two peers' web-browsers. This using audio, video, and data between two peers' web-browsers. This
document describes the non-media data transport aspects of the WebRTC document specifies the non-media data transport aspects of the WebRTC
framework. It provides an architectural overview of how the Stream framework. It provides an architectural overview of how the Stream
Control Transmission Protocol (SCTP) is used in the WebRTC context as Control Transmission Protocol (SCTP) is used in the WebRTC context as
a generic transport service allowing Web Browser to exchange generic a generic transport service allowing Web Browser to exchange generic
data from peer to peer. data from peer to peer.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on April 26, 2013. This Internet-Draft will expire on August 28, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Use Cases for Unreliable Data Channels . . . . . . . . . . 4
4.1. Use Cases for Unreliable Datagram Based Channels . . . . . 5 3.2. Use Cases for Reliable Data Channels . . . . . . . . . . . 4
4.2. Use Cases for Reliable Channels (Datagram or Stream 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4
Based) . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. SCTP over DTLS over UDP Considerations . . . . . . . . . . . . 6 5. SCTP over DTLS over UDP Considerations . . . . . . . . . . . . 6
6. The Usage of SCTP in the RTCWeb Context . . . . . . . . . . . 8 6. The Usage of SCTP in the RTCWeb Context . . . . . . . . . . . 9
6.1. Association Setup . . . . . . . . . . . . . . . . . . . . 9 6.1. Association Setup . . . . . . . . . . . . . . . . . . . . 9
6.2. SCTP Streams . . . . . . . . . . . . . . . . . . . . . . . 9 6.2. SCTP Streams . . . . . . . . . . . . . . . . . . . . . . . 9
6.3. Channel Definition . . . . . . . . . . . . . . . . . . . . 9 6.3. Channel Definition . . . . . . . . . . . . . . . . . . . . 9
6.4. Usage of Payload Protocol Identifier . . . . . . . . . . . 10 6.4. Usage of Payload Protocol Identifier . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
10. Informative References . . . . . . . . . . . . . . . . . . . . 11 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
Non-media data types in the context of RTCWEB are handled by using Non-media data types in the context of RTCWeb are handled by using
SCTP [RFC4960] encapsulated in DTLS [RFC6347]. SCTP [RFC4960] encapsulated in DTLS [RFC6347].
+----------+ +----------+
| SCTP | | SCTP |
+----------+ +----------+
| DTLS | | DTLS |
+----------+ +----------+
| ICE/UDP | | ICE/UDP |
+----------+ +----------+
Figure 1: Basic stack diagram Figure 1: Basic stack diagram
The encapsulation of SCTP over DTLS over ICE/UDP provides a NAT The encapsulation of SCTP over DTLS (see
traversal solution together with confidentiality, source [I-D.ietf-tsvwg-sctp-dtls-encaps]) over ICE/UDP (see [RFC5245])
authenticated, integrity protected transfers. This data transport provides a NAT traversal solution together with confidentiality,
service operates in parallel to the media transports, and all of them source authentication, and integrity protected transfers. This data
can eventually share a single transport-layer port number. transport service operates in parallel to the media transports, and
all of them can eventually share a single transport-layer port
number.
SCTP as specified in [RFC4960] with the extension defined in SCTP as specified in [RFC4960] with the partial reliability extension
[RFC3758] provides multiple streams natively with reliable, and defined in [RFC3758] provides multiple streams natively with
partially-reliable delivery modes. reliable, and partially-reliable delivery modes.
The remainder of this document is organized as follows: Section 3 and The remainder of this document is organized as follows: Section 4 and
Section 4 provide requirements and use cases for both unreliable and Section 3 provide requirements and use cases for both unreliable and
reliable peer to peer datagram base channel; Section 5 arguments SCTP reliable peer to peer datagram base channel; Section 5 arguments SCTP
over DTLS over UDP; Section 6 provides an overview of how SCTP should over DTLS over UDP; Section 6 provides an specification of how SCTP
be used by the RTCWeb protocol framework for transporting non-media should be used by the RTCWeb protocol framework for transporting non-
data between browsers. media data between browsers.
2. Conventions 2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. Requirements 3. Use Cases
This section lists the requirements for P2P data connections between This section defined use cases specific to data channels. For
two browsers. general use cases see [I-D.ietf-rtcweb-use-cases-and-requirements].
Req. 1 Multiple simultaneous datagram streams MUST be supported. 3.1. Use Cases for Unreliable Data Channels
Note that there may 0 or more media streams in parallel with
the data streams, and the number and state (active/inactive)
of the media streams may change at any time.
Req. 2 Both reliable and unreliable datagram streams MUST be U-C 1 A real-time game where position and object state information
is sent via one or more unreliable data channels. Note that
at any time there may be no media channels, or all media
channels may be inactive, and that there may also be reliable
data channels in use.
U-C 2 Providing non-critical information to a user about the reason
for a state update in a video chat or conference, such as Mute
state.
3.2. Use Cases for Reliable Data Channels
U-C 3 A real-time game where critical state information needs to be
transferred, such as control information. Such a game may
have no media channels, or they may be inactive at any given
time, or may only be added due to in-game actions.
U-C 4 Non-realtime file transfers between people chatting. Note
that this may involve a large number of files to transfer
sequentially or in parallel, such as when sharing a folder of
images or a directory of files.
U-C 5 Realtime text chat while talking with an individual or with
multiple people in a conference.
U-C 6 Renegotiation of the set of media streams in the
PeerConnection.
U-C 7 Proxy browsing, where a browser uses data channels of a
PeerConnection to send and receive HTTP/HTTPS requests and
data, for example to avoid local internet filtering or
monitoring.
4. Requirements
This section lists the requirements for P2P data channels between two
browsers.
Req. 1 Multiple simultaneous data channels MUST be supported. Note
that there may 0 or more media streams in parallel with the
data channels, and the number and state (active/inactive) of
the media streams may change at any time.
Req. 2 Both reliable and unreliable data channels MUST be
supported. supported.
Req. 3 Data streams MUST be congestion controlled; either Req. 3 Data channels MUST be congestion controlled; either
individually, as a class, or in conjunction with the media individually, as a class, or in conjunction with the media
streams, to ensure that datagram exchanges don't cause streams, to ensure that data channels don't cause congestion
congestion problems for the media streams, and that the problems for the media streams, and that the RTCWeb
rtcweb PeerConnection as a whole is fair with competing PeerConnection as a whole is fair with competing traffic
streams such as TCP. such as TCP.
Req. 4 The application SHOULD be able to provide guidance as to the Req. 4 The application SHOULD be able to provide guidance as to the
relative priority of each datagram stream relative to each relative priority of each data channel relative to each
other, and relative to the media streams. [ TBD: how this is other, and relative to the media streams. [ TBD: how this is
encoded and what the impact of this is. ] This will interact encoded and what the impact of this is. ] This will interact
with the congestion control algorithms. with the congestion control algorithms.
Req. 5 Datagram streams MUST be encrypted; allowing for Req. 5 Data channels MUST be secured; allowing for confidentiality,
confidentiality, integrity and source authentication. See integrity and source authentication. See
[I-D.ietf-rtcweb-security] and [I-D.ietf-rtcweb-security] and
[I-D.ietf-rtcweb-security-arch] for detailed info. [I-D.ietf-rtcweb-security-arch] for detailed info.
Req. 6 Consent and NAT traversal mechanism: These are handled by Req. 6 Data channels MUST provide message fragmentation support
the PeerConnection's ICE [RFC5245] connectivity checks and such that IP-layer fragmentation can be avoided no matter
optional TURN servers. how large a message the Javascript application passes to be
Req. 7 Data streams MUST provide message fragmentation support such
that IP-layer fragmentation does not occur no matter how
large a message the Javascript application passes to be
sent. sent.
Req. 8 The data stream transport protocol MUST not encode local IP Req. 7 The data channel transport protocol MUST NOT encode local IP
addresses inside its protocol fields; doing so reveals addresses inside its protocol fields; doing so reveals
potentially private information, and leads to failure if the potentially private information, and leads to failure if the
address is depended upon. address is depended upon.
Req. 9 The data stream protocol SHOULD support unbounded-length Req. 8 The data channel transport protocol SHOULD support
"messages" (i.e., a virtual socket stream) at the unbounded-length "messages" (i.e., a virtual socket stream)
application layer, for such things as image-file-transfer; at the application layer, for such things as image-file-
or it MUST support a maximum application-layer message size transfer; Implementations might enforce a reasonable message
of at least 2GB. size limit.
Req. 10 The data stream packet format/encoding MUST be such that it Req. 9 The data channel packet format/encoding MUST be such that it
is impossible for a malicious Javascript to generate an is impossible for a malicious Javascript to generate an
application message crafted such that it could be application message crafted such that it could be
interpreted as a native protocol over UDP - such as UPnP, interpreted as a native protocol over UDP - such as UPnP,
RTP, SNMP, STUN, etc. RTP, SNMP, STUN, etc.
Req. 11 The data stream transport protocol MUST start with the Req. 10 The data channel transport protocol SHOULD avoid IP
assumption of a PMTU of 1280 [ *** need justification ***] fragmentation. It MUST support PMTU discovery and MUST NOT
bytes until measured otherwise. rely on ICMP or ICMPv6 being generated or being passed back,
especially for PMTU discovery.
Req. 12 The data stream transport protocol MUST NOT rely on ICMP or
ICMPv6 being generated or being passed back, such as for
PMTU discovery.
Req. 13 It MUST be possible to implement the protocol stack in the Req. 11 It MUST be possible to implement the protocol stack in the
user application space. user application space.
4. Use Cases 5. SCTP over DTLS over UDP Considerations
4.1. Use Cases for Unreliable Datagram Based Channels
U-C 1 A real-time game where position and object state information
is sent via one or more unreliable data channels. Note that
at any time there may be no media channels, or all media
channels may be inactive, and that there may also be reliable
data channels in use.
U-C 2 Non-critical state updates about a user in a video chat or The important features of SCTP in the RTCWeb context are:
conference, such as Mute state.
4.2. Use Cases for Reliable Channels (Datagram or Stream Based) o TCP-friendly congestion control.
Note that either reliable datagrams or streams are possible; reliable o The congestion control is modifiable for integration with media
streams would be fairly simple to layer on top of SCTP reliable stream congestion control.
datagrams with in-order delivery.
U-C 3 A real-time game where critical state information needs to be o Support for multiple channels with different characteristics.
transferred, such as control information. Typically this
would be datagrams. Such a game may have no media channels,
or they may be inactive at any given time, or may only be
added due to in-game actions.
U-C 4 Non-realtime file transfers between people chatting. This o Support for out-of-order delivery.
could be datagrams or streaming. Note that this may involve a
large number of files to transfer sequentially or in parallel,
such as when sharing a folder of images or a directory of
files.
U-C 5 Realtime text chat while talking with an individual or with o Support for large datagrams and PMTU-discovery and fragmentation.
multiple people in a conference. Typically this would be
datagrams.
U-C 6 Renegotiation of the set of media streams in the o Reliable or partial reliability support.
PeerConnection. Typically this would be datagrams.
U-C 7 Proxy browsing, where a browser uses data channels of a o Support of multiple streams.
PeerConnection to send and receive HTTP/HTTPS requests and
data, for example to avoid local internet filtering or
monitoring. Typically this would be streams.
5. SCTP over DTLS over UDP Considerations SCTP multihoming will not be used in RTCWeb. The SCTP layer will
simply act as if it were running on a single-homed host, since that
is the abstraction that the lower layer (a connection oriented,
unreliable datagram service) exposes.
The encapsulation of SCTP over DTLS as defined in The encapsulation of SCTP over DTLS defined in
[I-D.tuexen-tsvwg-sctp-dtls-encaps] provides a NAT traversal solution [I-D.ietf-tsvwg-sctp-dtls-encaps] provides confidentiality, source
together with confidentiality, source authenticated, integrity authenticated, and integrity protected transfers. Using DTLS over
protected transfers. SCTP as specified in [RFC4960] MUST be used in UDP in combination with ICE enables NAT traversal in IPv4 based
combination with the extension defined in [RFC3758] and provides the networks. SCTP as specified in [RFC4960] MUST be used in combination
following interesting features for transporting non-media data with the extension defined in [RFC3758] and provides the following
between browsers: interesting features for transporting non-media data between
browsers:
o Support of multiple streams. o Support of multiple unidirectional streams.
o Ordered and unordered delivery of user messages. o Ordered and unordered delivery of user messages.
o Reliable and partial-reliable transport of user messages. o Reliable and partial-reliable transport of user messages.
Each SCTP user message contains a so called Payload Protocol Each SCTP user message contains a so called Payload Protocol
Identifier (PPID) that is passed to SCTP by its upper layer and sent Identifier (PPID) that is passed to SCTP by its upper layer and sent
to its peer. This value represents an application (or upper layer) to its peer. This value can be used to multiplex multiple protocols
specified protocol identifier and be used to transport multiple over a single SCTP association. The sender provides for each
protocols over a single SCTP association. The sender provides for protocol a specific PPID and the receiver can demultiplex the
each protocol a specific PPID and the receiver MAY demultiplex the
messages based on the received PPID. messages based on the received PPID.
The encapsulation of SCTP over DTLS, together with the SCTP features The encapsulation of SCTP over DTLS, together with the SCTP features
listed above satisfies all the requirements listed in Section 3. listed above satisfies all the requirements listed in Section 4.
The layering of protocols for WebRTC is shown in the following The layering of protocols for WebRTC is shown in the following
Figure 2. Figure 2.
+------+ +------+
|RTCWEB| |RTCWEB|
| DATA | | DATA |
+------+ +------+
| SCTP | | SCTP |
+--------------------+ +--------------------+
| STUN | SRTP | DTLS | | STUN | SRTP | DTLS |
+--------------------+ +--------------------+
| ICE | | ICE |
+--------------------+ +--------------------+
| UDP1 | UDP2 | ... | | UDP1 | UDP2 | ... |
+--------------------+ +--------------------+
Figure 2: WebRTC protocol layers Figure 2: WebRTC protocol layers
This stack (especially in contrast to DTLS over SCTP [RFC6083]) has This stack (especially in contrast to DTLS over SCTP [RFC6083] in
combination with SCTP over UDP [I-D.ietf-tsvwg-sctp-udp-encaps]) has
been chosen because it been chosen because it
o supports the transmission of arbitrary large user messages. o supports the transmission of arbitrary large user messages.
o shares the DTLS connection with the media channels. o shares the DTLS connection with the media channels.
o provides privacy for the SCTP control information. o provides privacy for the SCTP control information.
Considering the protocol stack of Figure 2 the usage of DTLS over UDP Considering the protocol stack of Figure 2 the usage of DTLS over UDP
is specified in [RFC6347], while the usage of SCTP on top of DTLS is is specified in [RFC6347], while the usage of SCTP on top of DTLS is
specified in [I-D.tuexen-tsvwg-sctp-dtls-encaps]. specified in [I-D.ietf-tsvwg-sctp-dtls-encaps].
Since DTLS is typically implemented in user-land, the SCTP stack also Since DTLS is typically implemented in user-land, the SCTP stack also
needs to be a user-land stack. needs to be a user-land stack.
When using DTLS as the lower layer, only single homed SCTP When using DTLS as the lower layer, only single homed SCTP
associations SHOULD be used, since DTLS does not expose any address associations MUST be used, since DTLS does not expose any address
management to its upper layer. The ICE/UDP layer can handle IP management to its upper layer. The ICE/UDP layer can handle IP
address changes during a session without needing to notify the DTLS address changes during a session without needing to notify the DTLS
and SCTP layers, though it would be advantageous to retest path MTU and SCTP layers, though it would be advantageous to retest path MTU
on an IP address change. on an IP address change.
DTLS implementations used for this stack SHOULD support controlling DTLS implementations used for this stack SHOULD support controlling
fields of the IP layer like the Don't fragment (DF)-bit in case of fields of the IP layer like the Don't fragment (DF)-bit in case of
IPv4 and the Differentiated Services Code Point (DSCP) field required IPv4 and the Differentiated Services Code Point (DSCP) field required
for supporting [I-D.ietf-rtcweb-qos]. Being able to set the (DF)-bit for supporting [I-D.ietf-rtcweb-qos]. Being able to set the (DF)-bit
in case of IPv4 is required for performing path MTU discovery. The in case of IPv4 is required for performing path MTU discovery. The
DTLS implementation SHOULD also support sending user messages DTLS implementation SHOULD also support sending user messages
exceeding the path MTU. exceeding the path MTU.
Incoming ICMP or ICMPv6 messages can't be processed by the SCTP Incoming ICMP or ICMPv6 messages can't be processed by the SCTP
layer, since there is no way to identify the corresponding layer, since there is no way to identify the corresponding
association. Therefore SCTP MUST support performing Path MTU association. Therefore SCTP MUST support performing Path MTU
discovery without relying on ICMP or ICMPv6. In general, the lower discovery without relying on ICMP or ICMPv6 as specified in [RFC4821]
layer interface of an SCTP implementation SHOULD be adapted to using probing messages specified in [RFC4820]. The initial Path MTU
address the differences between IPv4 or IPv6 (being connection-less) MUST NOT exceed 1280 [ *** need justification ***] bytes until
or DTLS (being connection-oriented). measured otherwise.
In general, the lower layer interface of an SCTP implementation
SHOULD be adapted to address the differences between IPv4 or IPv6
(being connection-less) or DTLS (being connection-oriented).
When protocol stack of Figure 2 is used, DTLS protects the complete When protocol stack of Figure 2 is used, DTLS protects the complete
SCTP packet, so it provides confidentiality, integrity and source SCTP packet, so it provides confidentiality, integrity and source
authentication of the complete SCTP packet. authentication of the complete SCTP packet.
This protocol stack MUST support the usage of multiple SCTP streams. This protocol stack MUST support the usage of multiple SCTP streams.
A user message can be sent ordered or unordered and with partial or A user message can be sent ordered or unordered and with partial or
full reliability. The partial reliability extension MUST support full reliability. The partial reliability extension MUST support
policies to limit policies to limit
skipping to change at page 8, line 38 skipping to change at page 8, line 51
means that all SCTP streams within a single SCTP association share means that all SCTP streams within a single SCTP association share
the same congestion window. Traffic not being sent over SCTP is not the same congestion window. Traffic not being sent over SCTP is not
covered by the SCTP congestion control. Due to the typical parallel covered by the SCTP congestion control. Due to the typical parallel
SRTP media streams, a delay-sensitive congestion control algorithm SRTP media streams, a delay-sensitive congestion control algorithm
MUST be supported and the congestion control MAY be coordinated MUST be supported and the congestion control MAY be coordinated
between the data channels and the media streams to avoid a data between the data channels and the media streams to avoid a data
channel transfer ending up with most or all the channel bandwidth. channel transfer ending up with most or all the channel bandwidth.
Since SCTP does not support the negotiation of a congestion control Since SCTP does not support the negotiation of a congestion control
algorithm, the algorithm either MUST be negotiated before algorithm, the algorithm either MUST be negotiated before
establishment of the SCTP association or MUST not require any establishment of the SCTP association or MUST NOT require any
negotiation because it only requires sender side behavior using negotiation because it only requires sender side behavior using
existing information carried in the association. existing information carried in the association.
6. The Usage of SCTP in the RTCWeb Context 6. The Usage of SCTP in the RTCWeb Context
The important features of SCTP in the RTCWeb context are:
o TCP-friendly congestion control.
o The congestion control is modifiable for integration with media
stream congestion control.
o Support for multiple channels with different characteristics.
o Support for out-of-order delivery.
o Support for large datagrams and PMTU-discovery and fragmentation.
o Reliable or partial reliability support.
o Support of multiple streams.
SCTP multihoming will not be used in RTCWeb. The SCTP layer will
simply act as if it were running on a single-homed host, since that
is the abstraction that the lower layer (a connection oriented,
unreliable datagram service) exposes.
6.1. Association Setup 6.1. Association Setup
The SCTP association will be set up when the two endpoints of the The SCTP association will be set up when the two endpoints of the
WebRTC PeerConnection agree on opening it, as negotiated by JSEP WebRTC PeerConnection agree on opening it, as negotiated by JSEP
(typically an exchange of SDP) [I-D.ietf-rtcweb-jsep]. Additionally, (typically an exchange of SDP) [I-D.ietf-rtcweb-jsep]. Additionally,
the negotiation SHOULD include some type of congestion control the negotiation SHOULD include some type of congestion control
selection. It will use the DTLS connection selected via SDP; selection. It will use the DTLS connection selected via SDP;
typically this will be shared via BUNDLE with DTLS connections used typically this will be shared via BUNDLE with DTLS connections used
to key the DTLS-SRTP media streams. to key the DTLS-SRTP media streams.
The application SHOULD indicate the initial number of streams The application SHOULD indicate the initial number of streams
required when opening the association, and if no value is supplied, required when opening the association, and if no value is supplied,
the implementation SHOULD provide a default, with a suggested value the implementation SHOULD provide an appropriate default. If more
of 16. If more simultaneous streams are needed, [RFC6525] allows simultaneous streams are needed, [RFC6525] allows adding additional
adding additional (but not removing) streams to an existing (but not removing) streams to an existing association. Note there
association. Note there can be up to 65536 SCTP streams per SCTP can be up to 65536 SCTP streams per SCTP association in each
association in each direction. direction.
6.2. SCTP Streams 6.2. SCTP Streams
SCTP defines a stream as an unidirectional logical channel existing SCTP defines a stream as an unidirectional logical channel existing
within an SCTP association one to another SCTP endpoint. The streams within an SCTP association one to another SCTP endpoint. The streams
are used to provide the notion of in-sequence delivery and for are used to provide the notion of in-sequence delivery and for
multiplexing. Each user message is sent on a particular stream, multiplexing. Each user message is sent on a particular stream,
either order or unordered. Ordering is preserved only for all either order or unordered. Ordering is preserved only for all
ordered messages sent on the same stream. ordered messages sent on the same stream.
skipping to change at page 10, line 18 skipping to change at page 10, line 9
The realization of a bidirectional Data Channel is a pair of one The realization of a bidirectional Data Channel is a pair of one
incoming stream and one outgoing SCTP stream. incoming stream and one outgoing SCTP stream.
The simple protocol specified in [I-D.jesup-rtcweb-data-protocol] The simple protocol specified in [I-D.jesup-rtcweb-data-protocol]
MUST be used to set up and manage the bidirectional data channels. MUST be used to set up and manage the bidirectional data channels.
Note that there's no requirement for the SCTP streams used to create Note that there's no requirement for the SCTP streams used to create
a bidirectional channel have the same number in each direction. How a bidirectional channel have the same number in each direction. How
stream values are selected is protocol and implementation dependent. stream values are selected is protocol and implementation dependent.
Closing of a Data Channel MUST be signalled by resetting the Closing of a Data Channel MUST be signaled by resetting the
corresponding streams [RFC6525]. Resetting a stream set the Stream corresponding streams [RFC6525]. Resetting a stream set the Stream
Sequence Numbers (SSNs) of the stream back to 'zero' with a Sequence Numbers (SSNs) of the stream back to 'zero' with a
corresponding notification to the application layer that the reset corresponding notification to the application layer that the reset
has been performed. Closed streams are available to reuse. has been performed. Streams are available to reuse after a reset has
been performed.
[RFC6525] also guarantees that all the messages are delivered (or [RFC6525] also guarantees that all the messages are delivered (or
expired) before resetting the stream. expired) before resetting the stream.
6.4. Usage of Payload Protocol Identifier 6.4. Usage of Payload Protocol Identifier
The SCTP Payload Protocol Identifiers (PPIDs) MUST used to signal the The SCTP Payload Protocol Identifiers (PPIDs) can be used to signal
interpretation of the "Payload data", like the protocol specified in the interpretation of the "Payload data", like the protocol specified
[I-D.jesup-rtcweb-data-protocol] uses them to identify a Javascript in [I-D.jesup-rtcweb-data-protocol] uses them to identify a
string, a Javascript array or a a Javascript blob. Javascript string, a Javascript array or a Javascript blob.
7. Security Considerations 7. Security Considerations
To be done. This document does not add any additional considerations to the ones
given in [I-D.ietf-rtcweb-security] and
[I-D.ietf-rtcweb-security-arch].
8. IANA Considerations 8. IANA Considerations
This document does not require any actions by the IANA. This document does not require any actions by the IANA.
9. Acknowledgments 9. Acknowledgments
Many thanks for comments, ideas, and text from Harald Alvestrand, Many thanks for comments, ideas, and text from Harald Alvestrand,
Adam Bergkvist, Cullen Jennings, Eric Rescorla, Randall Stewart, and Adam Bergkvist, Cullen Jennings, Eric Rescorla, Randall Stewart,
Justin Uberti. Justin Uberti, and Magnus Westerlund.
10. Informative References 10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP) Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004. Partial Reliability Extension", RFC 3758, May 2004.
[RFC4820] Tuexen, M., Stewart, R., and P. Lei, "Padding Chunk and
Parameter for the Stream Control Transmission Protocol
(SCTP)", RFC 4820, March 2007.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, March 2007.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", [RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007. RFC 4960, September 2007.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT) (ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, Traversal for Offer/Answer Protocols", RFC 5245,
April 2010. April 2010.
[RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
Transport Layer Security (DTLS) for Stream Control
Transmission Protocol (SCTP)", RFC 6083, January 2011.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012. Security Version 1.2", RFC 6347, January 2012.
[RFC6525] Stewart, R., Tuexen, M., and P. Lei, "Stream Control [RFC6525] Stewart, R., Tuexen, M., and P. Lei, "Stream Control
Transmission Protocol (SCTP) Stream Reconfiguration", Transmission Protocol (SCTP) Stream Reconfiguration",
RFC 6525, February 2012. RFC 6525, February 2012.
[I-D.jesup-rtcweb-data-protocol]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel
Protocol", draft-jesup-rtcweb-data-protocol-03 (work in
progress), September 2012.
[I-D.ietf-tsvwg-sctp-dtls-encaps]
Jesup, R., Loreto, S., Stewart, R., and M. Tuexen, "DTLS
Encapsulation of SCTP Packets for RTCWEB",
draft-ietf-tsvwg-sctp-dtls-encaps-00 (work in progress),
February 2013.
[I-D.ietf-rtcweb-security] [I-D.ietf-rtcweb-security]
Rescorla, E., "Security Considerations for RTC-Web", Rescorla, E., "Security Considerations for RTC-Web",
draft-ietf-rtcweb-security-03 (work in progress), draft-ietf-rtcweb-security-04 (work in progress),
June 2012. January 2013.
[I-D.ietf-rtcweb-security-arch] [I-D.ietf-rtcweb-security-arch]
Rescorla, E., "RTCWEB Security Architecture", Rescorla, E., "RTCWEB Security Architecture",
draft-ietf-rtcweb-security-arch-05 (work in progress), draft-ietf-rtcweb-security-arch-06 (work in progress),
October 2012. January 2013.
[I-D.ietf-rtcweb-jsep] [I-D.ietf-rtcweb-jsep]
Uberti, J. and C. Jennings, "Javascript Session Uberti, J. and C. Jennings, "Javascript Session
Establishment Protocol", draft-ietf-rtcweb-jsep-01 (work Establishment Protocol", draft-ietf-rtcweb-jsep-02 (work
in progress), June 2012. in progress), October 2012.
[I-D.ietf-rtcweb-qos] [I-D.ietf-rtcweb-qos]
Dhesikan, S., Druta, D., Jones, P., and J. Polk, "DSCP and Dhesikan, S., Druta, D., Jones, P., and J. Polk, "DSCP and
other packet markings for RTCWeb QoS", other packet markings for RTCWeb QoS",
draft-ietf-rtcweb-qos-00 (work in progress), October 2012. draft-ietf-rtcweb-qos-00 (work in progress), October 2012.
[I-D.ietf-tsvwg-sctp-udp-encaps] 10.2. Informative References
Tuexen, M. and R. Stewart, "UDP Encapsulation of SCTP
Packets", draft-ietf-tsvwg-sctp-udp-encaps-06 (work in
progress), October 2012.
[I-D.jesup-rtcweb-data-protocol] [RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Channel Transport Layer Security (DTLS) for Stream Control
Protocol", draft-jesup-rtcweb-data-protocol-03 (work in Transmission Protocol (SCTP)", RFC 6083, January 2011.
progress), September 2012.
[I-D.tuexen-tsvwg-sctp-dtls-encaps] [I-D.ietf-rtcweb-use-cases-and-requirements]
Jesup, R., Loreto, S., Stewart, R., and M. Tuexen, "DTLS Holmberg, C., Hakansson, S., and G. Eriksson, "Web Real-
Encapsulation of SCTP Packets for RTCWEB", Time Communication Use-cases and Requirements",
draft-tuexen-tsvwg-sctp-dtls-encaps-01 (work in progress), draft-ietf-rtcweb-use-cases-and-requirements-10 (work in
July 2012. progress), December 2012.
[I-D.ietf-tsvwg-sctp-udp-encaps]
Tuexen, M. and R. Stewart, "UDP Encapsulation of SCTP
Packets for End-Host to End-Host Communication",
draft-ietf-tsvwg-sctp-udp-encaps-11 (work in progress),
February 2013.
Authors' Addresses Authors' Addresses
Randell Jesup Randell Jesup
Mozilla Mozilla
USA US
Email: randell-ietf@jesup.org Email: randell-ietf@jesup.org
Salvatore Loreto Salvatore Loreto
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland FI
Email: salvatore.loreto@ericsson.com Email: salvatore.loreto@ericsson.com
Michael Tuexen Michael Tuexen
Muenster University of Applied Sciences Muenster University of Applied Sciences
Stegerwaldstrasse 39 Stegerwaldstrasse 39
Steinfurt 48565 Steinfurt 48565
Germany DE
Email: tuexen@fh-muenster.de Email: tuexen@fh-muenster.de
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