Network Working Group                                           R. Jesup
Internet-Draft                                  WorldGate Communications
Intended status: Standards Track                               S. Loreto
Expires: August 20, 2013 January 16, 2014                                       Ericsson
                                                              R. Stewart
                                                          Adara Networks
                                                               M. Tuexen
                                        Muenster Univ. of Appl. Sciences
                                                       February 16,
                                                           July 15, 2013

                   DTLS Encapsulation of SCTP Packets for RTCWEB


   The Stream Control Transmission Protocol (SCTP) is a transport
   protocol originally defined to run on top of the network protocols
   IPv4 or IPv6.  This memo document specifies how SCTP can be used on top of
   the Datagram Transport Layer Security (DTLS) protocol.  SCTP
   over DTLS is used by the RTCWeb protocol suite for transporting non-
   media data between browsers.

Status of this 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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 20, 2013. January 16, 2014.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Encapsulation and Decapsulation Procedure . . . . . . . . . . .   3
   4.  DTLS Considerations . . . . . . . . . . . . . . . . . . . . . . 4   3
   5.  SCTP Considerations . . . . . . . . . . . . . . . . . . . . . . 4   3
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6   5
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 7   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7   6

1.  Introduction

1.1.  Overview

   The Stream Control Transmission Protocol (SCTP) as defined in
   [RFC4960] is a transport protocol running on top of the network
   protocols IPv4 or IPv6.  This memo document specifies how SCTP can be is used on
   top of the Datagram Transport Layer Security (DTLS) protocol.
   SCTP over DTLS  This
   encapsulation is used by for example within the RTCWeb protocol suite
   (see [I-D.ietf-rtcweb-overview] for an overview) for transporting non-
   non-media data between browsers.  The architecture of this stack is
   described in [I-D.jesup-rtcweb-data]. [I-D.ietf-rtcweb-data-channel].

1.2.  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.

1.3.  Abbreviations

   DTLS:  Datagram Transport Layer Security.

   MTU:  Maximum Transmission Unit.

   PPID:  Payload Protocol Identifier.

   SCTP:  Stream Control Transmission Protocol.

   TCP:  Transmission Control Protocol.

   TLS:  Transport Layer Security.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  Encapsulation and Decapsulation Procedure

   When an SCTP packet is sent down to the DTLS layer, the complete SCTP
   packet, consisting of the SCTP common header and a number of SCTP
   chunks, MUST be handled as the payload of the application layer
   protocol of DTLS.  When the DTLS layer has processed a DTLS record
   containing a message of the application layer protocol, the payload
   MUST be given up to the SCTP layer.  The SCTP layer expects an SCTP
   common header followed by a number of SCTP chunks.

4.  DTLS Considerations

   The DTLS implementation MUST be based on [RFC6347].

   If path MTU discovery is performed by the DTLS layer, the method
   described in [RFC4821] MUST be used.  For probe packets, the
   extension defined in [RFC6520] MUST be used.

   If path MTU discovery is performed by the SCTP layer and IPv4 is used
   as the network layer protocol, the DTLS implementation MUST allow the
   DTLS user to enforce that the corresponding IPv4 packet is sent with
   the DF bit set.

   SCTP performs segmentation and reassembly based on the path MTU.
   Therefore the DTLS layer MUST NOT use any compression algorithm.

5.  SCTP Considerations

5.1.  Base Protocol

   SCTP as specified in [RFC4960] is used.  However, the following
   restrictions are necessary to reflect that the lower layer is the
   connection oriented protocol DTLS instead of the connection less
   protocol IPv4 and IPv6:

   o  A DTLS connection MUST be established before an SCTP association
      can be set up.

   o  All associations MUST be single-homed.

   o  The INIT and INIT-ACK chunk MUST NOT contain any IPv4 Address or
      IPv6 Address parameters.  The INIT chunk MUST NOT contain the
      Supported Address Types parameter.

   o  The implementation MUST NOT rely on processing ICMP or ICMPv6
      packets.  This applies in particular to path MTU discovery when
      performed by SCTP.

5.2.  Padding Extension

   The padding extension defined in [RFC4820] MUST be supported and used
   for probe packets when performing path MTU discovery as specified in

5.3.  Dynamic Address Reconfiguration Extension

   The SCTP implementation MUST support the Supported Extensions
   Parameter defined in [RFC5061] to signal the support of

   If the SCTP
   stream reset dynamic address reconfiguration extension (see Section 5.6).  The other functionality
   described defined in [RFC5061]
   is used, only wildcard addresses MUST NOT be used. used in ASCONF chunks.

5.4.  SCTP Authentication Extension

   The SCTP authentication extension defined in [RFC4895] is can be used
   with DTLS encapsulation, but does not
   required. require any additional benefit.

5.5.  Partial Reliability Extension

   The SCTP implementation MUST support the extension

   Partial reliability as defined in

   The SCTP implementation SHOULD support the following PR-SCTP

   o  A user message is abandoned after a user specified lifetime.

   o  A user message [RFC3758] can be used in
   combination with DTLS encapsulation.  It is abandoned if the number of retransmissions
      exceeds a user specified threshold. also possible to use
   additional PR-SCTP policies.

5.6.  Stream Reset Extension

   The SCTP implementation MUST support the SCTP stream reset extension defined in [RFC6525]. [RFC6525] can be used with
   DTLS encapsulation.  It is used to reset streams and add streams
   during the lifetime of the SCTP association.

5.7.  Interleaving of Large User Message Extension

   SCTP as defined in [RFC4960] does not support the multiplexing interleaving of
   large user messages that need to be fragmented and reassembled by the
   SCTP layer.  To overcome this limitation, the SCTP implementation
   SHOULD support an extension, which has to be defined.

5.8.  Congestion Control

   In addition to the TCP-like congestion control specified  The protocol extension defined in
   [RFC4960], other congestion control algorithms MAY be provided.  For
   example, it might
   [I-D.stewart-tsvwg-sctp-ndata] overcomes this limitation can can be helpful to use a congestion control which does
   not increase the queueing delay substantially (see [RFC6817] for an
   used with DTLS encapsulation.

6.  IANA Considerations

   This document requires no actions from IANA.

7.  Security Considerations

   This document does not add any additional security

   Security considerations for DTLS are specified in
   addition to the ones given [RFC6347] and for
   SCTP in [RFC4960], [RFC3758], [RFC6525], and
   [RFC6347]. [RFC6525].  The combination of SCTP
   and DTLS introduces no new security considerations.

8.  Acknowledgments

   The authors wish to thank XXX Gorry Fairhurst for their his invaluable

9.  References

9.1.  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.

   [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.

   [RFC4895]  Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
              "Authenticated Chunks for the Stream Control Transmission
              Protocol (SCTP)", RFC 4895, August 2007.

   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol", RFC
              4960, September 2007.

   [RFC5061]  Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
              Kozuka, "Stream Control Transmission Protocol (SCTP)
              Dynamic Address Reconfiguration", RFC 5061, September

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.

   [RFC6520]  Seggelmann, R., Tuexen, M., and M. Williams, "Transport
              Layer Security (TLS) and Datagram Transport Layer Security
              (DTLS) Heartbeat Extension", RFC 6520, February 2012.

   [RFC6525]  Stewart, R., Tuexen, M., and P. Lei, "Stream Control
              Transmission Protocol (SCTP) Stream Reconfiguration", RFC
              6525, February 2012.

              Stewart, R., Tuexen, M., and S. Loreto, "A New Data Chunk
              for Stream Control Transmission Protocol", draft-stewart-
              tsvwg-sctp-ndata-01 (work in progress), February 2013.

9.2.  Informative References

   [RFC6817]  Shalunov, S., Hazel, G., Iyengar, J.,

   [RFC4895]  Tuexen, M., Stewart, R., Lei, P., and M. Kuehlewind,
              "Low Extra Delay Background Transport (LEDBAT)", E. Rescorla,
              "Authenticated Chunks for the Stream Control Transmission
              Protocol (SCTP)", RFC 6817,
              December 2012. 4895, August 2007.

              Alvestrand, H., "Overview: Real Time Protocols for Brower-
              based Applications", draft-ietf-rtcweb-overview-05 draft-ietf-rtcweb-overview-06 (work
              in progress), December 2012.

   [I-D.jesup-rtcweb-data] February 2013.

              Jesup, R., Loreto, S., and M. Tuexen, "RTCWeb Datagram
              Connection", draft-jesup-rtcweb-data-01 Data
              Channels", draft-ietf-rtcweb-data-channel-04 (work in
              progress), October 2011. February 2013.

Authors' Addresses

   Randell Jesup
   WorldGate Communications
   3800 Horizon Blvd, Suite #103
   Trevose, PA  19053-4947

   Phone: +1-215-354-5166

   Salvatore Loreto
   Hirsalantie 11
   Jorvas  02420

   Randall R. Stewart
   Adara Networks
   Chapin, SC  29036


   Michael Tuexen
   Muenster University of Applied Sciences
   Stegerwaldstrasse 39
   48565 Steinfurt