draft-ietf-tsvwg-sctp-dtls-encaps-04.txt   draft-ietf-tsvwg-sctp-dtls-encaps-05.txt 
Network Working Group M. Tuexen Network Working Group M. Tuexen
Internet-Draft Muenster Univ. of Appl. Sciences Internet-Draft Muenster Univ. of Appl. Sciences
Intended status: Standards Track R. Stewart Intended status: Standards Track R. Stewart
Expires: November 14, 2014 Adara Networks Expires: January 5, 2015 Adara Networks
R. Jesup R. Jesup
WorldGate Communications WorldGate Communications
S. Loreto S. Loreto
Ericsson Ericsson
May 13, 2014 July 4, 2014
DTLS Encapsulation of SCTP Packets DTLS Encapsulation of SCTP Packets
draft-ietf-tsvwg-sctp-dtls-encaps-04.txt draft-ietf-tsvwg-sctp-dtls-encaps-05.txt
Abstract Abstract
The Stream Control Transmission Protocol (SCTP) is a transport The Stream Control Transmission Protocol (SCTP) is a transport
protocol originally defined to run on top of the network protocols protocol originally defined to run on top of the network protocols
IPv4 or IPv6. This document specifies how SCTP can be used on top of IPv4 or IPv6. This document specifies how SCTP can be used on top of
the Datagram Transport Layer Security (DTLS) protocol. Using the Datagram Transport Layer Security (DTLS) protocol. Using the
encapsulation method described in this document, SCTP is agnostic encapsulation method described in this document, SCTP is agnostic
about the protocols being used below DTLS, explicit IP addresses can about the protocols being used below DTLS, explicit IP addresses can
not be used in the SCTP control chunks. As a consequence, the SCTP not be used in the SCTP control chunks. As a consequence, the SCTP
associations are single homed. associations are single homed.
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
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 14, 2014. This Internet-Draft will expire on January 5, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Encapsulation and Decapsulation Procedure . . . . . . . . . . 3 3. Encapsulation and Decapsulation Procedure . . . . . . . . . . 3
4. General Considerations . . . . . . . . . . . . . . . . . . . 3 4. General Considerations . . . . . . . . . . . . . . . . . . . 3
5. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . 3 5. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . 3
6. SCTP Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. SCTP Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Overview 1. Overview
The Stream Control Transmission Protocol (SCTP) as defined in The Stream Control Transmission Protocol (SCTP) as defined in
[RFC4960] is a transport protocol running on top of the network [RFC4960] is a transport protocol running on top of the network
protocols IPv4 [RFC0791] or IPv6 [RFC2460]. This document specifies protocols IPv4 [RFC0791] or IPv6 [RFC2460]. This document specifies
how SCTP is used on top of the Datagram Transport Layer Security how SCTP is used on top of the Datagram Transport Layer Security
(DTLS) protocol defined in [RFC6347]. This encapsulation is used for (DTLS) protocol defined in [RFC4347]. This encapsulation is used for
example within the WebRTC protocol suite (see example within the WebRTC protocol suite (see
[I-D.ietf-rtcweb-overview] for an overview) for transporting [I-D.ietf-rtcweb-overview] for an overview) for transporting non-SRTP
non-(S)RTP data between browsers. The architecture of this stack is data between browsers. The architecture of this stack is described
described in [I-D.ietf-rtcweb-data-channel]. in [I-D.ietf-rtcweb-data-channel].
Please note that the procedures defined in [RFC6951] for dealing with Please note that the procedures defined in [RFC6951] for dealing with
the UDP port numbers do not apply here. When using the encapsulation the UDP port numbers do not apply here. When using the encapsulation
defined in this document, SCTP is agnostic about the protocols used defined in this document, SCTP is agnostic about the protocols used
below DTLS. below DTLS.
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
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4. General Considerations 4. General Considerations
An implementation of SCTP over DTLS MUST implement and use a path An implementation of SCTP over DTLS MUST implement and use a path
maximum transmission unit (MTU) discovery method that functions maximum transmission unit (MTU) discovery method that functions
without ICMP to provide SCTP/DTLS with an MTU estimate. An without ICMP to provide SCTP/DTLS with an MTU estimate. An
implementation of "Packetization Layer Path MTU Discovery" [RFC4821] implementation of "Packetization Layer Path MTU Discovery" [RFC4821]
either in SCTP or DTLS is RECOMMENDED. either in SCTP or DTLS is RECOMMENDED.
5. DTLS Considerations 5. DTLS Considerations
The DTLS implementation MUST be based on DTLS 1.2 [RFC6347]. The The DTLS implementation MUST be based on DTLS 1.0 [RFC4347].
support of future versions of DTLS is RECOMMENDED if defined.
SCTP performs segmentation and reassembly based on the path MTU.
Therefore the DTLS layer MUST NOT use any compression algorithm.
The DTLS MUST support sending messages larger than the current path
MTU. This might result in sending IP level fragmented messages.
If path MTU discovery is performed by the DTLS layer, the method If path MTU discovery is performed by the DTLS layer, the method
described in [RFC4821] MUST be used. For probe packets, the described in [RFC4821] MUST be used. For probe packets, the
extension defined in [RFC6520] MUST be used. extension defined in [RFC6520] MUST be used.
If path MTU discovery is performed by the SCTP layer and IPv4 is 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 as the network layer protocol, the DTLS implementation SHOULD allow
DTLS user to enforce that the corresponding IPv4 packet is sent with the DTLS user to enforce that the corresponding IPv4 packet is sent
the Don't Fragment (DF) bit set. If controlling the DF bit is not with the Don't Fragment (DF) bit set. If controlling the DF bit is
possible, for example due to implementation restrictions, a safe not possible, for example due to implementation restrictions, a safe
value for the path MTU has to be used by the SCTP stack. value for the path MTU has to be used by the SCTP stack. It is
RECOMMENDED that the save value does not exceed 1200 bytes.
The DTLS implementation SHOULD allow the DTLS user to set the The DTLS implementation SHOULD allow the DTLS user to set the
Differentiated services code point (DSCP) used for IP packets being Differentiated services code point (DSCP) used for IP packets being
sent. This requires the DTLS implementation to pass the value sent (see [RFC2474]). This requires the DTLS implementation to pass
through and the lower layer to allow setting this value. If the the value through and the lower layer to allow setting this value.
lower layer does not support setting the DSCP, then the DTLS user If the lower layer does not support setting the DSCP, then the DTLS
will end up with the default value used by protocol stack. Please user will end up with the default value used by protocol stack.
note that only a single DSCP value can be used for all packets Please note that only a single DSCP value can be used for all packets
belonging to the same SCTP association. belonging to the same SCTP association.
Using explicit congestion notifications (ECN) in SCTP requires the Using explicit congestion notifications (ECN) in SCTP requires the
DTLS layer to pass the ECN bits through and its lower layer to expose DTLS layer to pass the ECN bits through and its lower layer to expose
access to them for sent and received packets. If this is not access to them for sent and received packets (see [RFC3168]). If
possible, for example due to implementation restrictions, ECN can't this is not possible, for example due to implementation restrictions,
be used by SCTP. ECN can't be used by SCTP.
SCTP performs segmentation and reassembly based on the path MTU.
Therefore the DTLS layer MUST NOT use any compression algorithm.
The DTLS MUST support sending messages larger than the current path
MTU. This might result in sending IP level fragmented messages.
6. SCTP Considerations 6. SCTP Considerations
This section describes the usage of the base protocol and the This section describes the usage of the base protocol and the
applicability of various SCTP extensions. applicability of various SCTP extensions.
6.1. Base Protocol 6.1. Base Protocol
This document uses SCTP [RFC4960] with the following restrictions, This document uses SCTP [RFC4960] with the following restrictions,
which are required to reflect that the lower layer is DTLS instead of which are required to reflect that the lower layer is DTLS instead of
IPv4 and IPv6 and that SCTP doesn't deal with the IP addresses or the IPv4 and IPv6 and that SCTP does not deal with the IP addresses or
transport protocol used below DTLS: the transport protocol used below DTLS:
o A DTLS connection MUST be established before an SCTP association o A DTLS connection MUST be established before an SCTP association
can be set up. can be set up.
o All SCTP associations are single-homed. Therefore it is o All SCTP associations are single-homed, because DTLS does not
expose any address management to its upper layer. Therefore it is
RECOMMENDED to set the SCTP parameter path.max.retrans to RECOMMENDED to set the SCTP parameter path.max.retrans to
association.max.retrans. association.max.retrans.
o The INIT and INIT-ACK chunk MUST NOT contain any IPv4 Address or o The INIT and INIT-ACK chunk MUST NOT contain any IPv4 Address or
IPv6 Address parameters. The INIT chunk MUST NOT contain the IPv6 Address parameters. The INIT chunk MUST NOT contain the
Supported Address Types parameter. Supported Address Types parameter.
o The implementation MUST NOT rely on processing ICMP or ICMPv6 o The implementation MUST NOT rely on processing ICMP or ICMPv6
packets. This applies in particular to path MTU discovery when packets. This applies in particular to path MTU discovery when
performed by SCTP. performed by SCTP.
o If the SCTP is notified about a path change by its lower layers,
SCTP SHOULD retest the Path MTU and reset the congestion state to
the initial state. In case of a window based congestion control
like the one specified in [RFC4960], this means setting the
congestion window and slow start threshold to its initial values.
6.2. Padding Extension 6.2. Padding Extension
The padding extension defined in [RFC4820] MUST be supported and used The padding extension defined in [RFC4820] MUST be supported and used
for probe packets when performing path MTU discovery as specified in for probe packets when performing path MTU discovery as specified in
[RFC4821]. [RFC4821] by the SCTP layer.
6.3. Dynamic Address Reconfiguration Extension 6.3. Dynamic Address Reconfiguration Extension
If the dynamic address reconfiguration extension defined in [RFC5061] If the dynamic address reconfiguration extension defined in [RFC5061]
is used, only wildcard addresses MUST be used in ASCONF chunks. is used, only wildcard addresses MUST be used in ASCONF chunks.
6.4. SCTP Authentication Extension 6.4. SCTP Authentication Extension
The SCTP authentication extension defined in [RFC4895] can be used The SCTP authentication extension defined in [RFC4895] can be used
with DTLS encapsulation, but does not provide any additional benefit. with DTLS encapsulation, but does not provide any additional benefit.
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SCTP layer. The protocol extension defined in SCTP layer. The protocol extension defined in
[I-D.ietf-tsvwg-sctp-ndata] overcomes this limitation and can be used [I-D.ietf-tsvwg-sctp-ndata] overcomes this limitation and can be used
with DTLS encapsulation. with DTLS encapsulation.
7. IANA Considerations 7. IANA Considerations
This document requires no actions from IANA. This document requires no actions from IANA.
8. Security Considerations 8. Security Considerations
Security considerations for DTLS are specified in [RFC6347] and for Security considerations for DTLS are specified in [RFC4347] and for
SCTP in [RFC4960], [RFC3758], and [RFC6525]. The combination of SCTP SCTP in [RFC4960], [RFC3758], and [RFC6525]. The combination of SCTP
and DTLS introduces no new security considerations. and DTLS introduces no new security considerations.
SCTP should not process the IP addresses used for the underlying
communication since DTLS provides no guarantees about them.
It should be noted that the inability to process ICMP or ICMPv6 It should be noted that the inability to process ICMP or ICMPv6
messages does not add any security issue. The processing of these messages does not add any security issue. The processing of these
messages for SCTP carried over a connection-less lower layer like IP, messages for SCTP carried over a connection-less lower layer like IP,
IPv6 or UDP is required to protect nodes not supporting SCTP. Since IPv6 or UDP is required to protect nodes not supporting SCTP. Since
DTLS provides a connection-oriented lower layer, this kind of DTLS provides a connection-oriented lower layer, this kind of
protection is not necessary. protection is not necessary.
9. Acknowledgments 9. Acknowledgments
The authors wish to thank Gorry Fairhurst, Joe Touch and Magnus The authors wish to thank Gorry Fairhurst, Eric Rescorla, Joe Touch
Westerlund for their invaluable comments. and Magnus Westerlund for their invaluable comments.
10. References 10. References
10.1. Normative 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.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006.
[RFC4820] Tuexen, M., Stewart, R., and P. Lei, "Padding Chunk and [RFC4820] Tuexen, M., Stewart, R., and P. Lei, "Padding Chunk and
Parameter for the Stream Control Transmission Protocol Parameter for the Stream Control Transmission Protocol
(SCTP)", RFC 4820, March 2007. (SCTP)", RFC 4820, March 2007.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, March 2007. Discovery", RFC 4821, March 2007.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007. 4960, September 2007.
[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 [RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport
Layer Security (TLS) and Datagram Transport Layer Security Layer Security (TLS) and Datagram Transport Layer Security
(DTLS) Heartbeat Extension", RFC 6520, February 2012. (DTLS) Heartbeat Extension", RFC 6520, February 2012.
10.2. Informative References 10.2. Informative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981. 1981.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998. (IPv6) Specification", RFC 2460, December 1998.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, December
1998.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP", RFC
3168, September 2001.
[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.
[RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla, [RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
"Authenticated Chunks for the Stream Control Transmission "Authenticated Chunks for the Stream Control Transmission
Protocol (SCTP)", RFC 4895, August 2007. Protocol (SCTP)", RFC 4895, August 2007.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M. [RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP) Kozuka, "Stream Control Transmission Protocol (SCTP)
skipping to change at page 7, line 10 skipping to change at page 7, line 27
[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", RFC Transmission Protocol (SCTP) Stream Reconfiguration", RFC
6525, February 2012. 6525, February 2012.
[RFC6951] Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream [RFC6951] Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream
Control Transmission Protocol (SCTP) Packets for End-Host Control Transmission Protocol (SCTP) Packets for End-Host
to End-Host Communication", RFC 6951, May 2013. to End-Host Communication", RFC 6951, May 2013.
[I-D.ietf-rtcweb-overview] [I-D.ietf-rtcweb-overview]
Alvestrand, H., "Overview: Real Time Protocols for Brower- Alvestrand, H., "Overview: Real Time Protocols for
based Applications", draft-ietf-rtcweb-overview-09 (work Browser-based Applications", draft-ietf-rtcweb-overview-10
in progress), February 2014. (work in progress), June 2014.
[I-D.ietf-rtcweb-data-channel] [I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-08 (work in Channels", draft-ietf-rtcweb-data-channel-10 (work in
progress), April 2014. progress), June 2014.
[I-D.ietf-tsvwg-sctp-ndata] [I-D.ietf-tsvwg-sctp-ndata]
Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann, "A Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann, "A
New Data Chunk for Stream Control Transmission Protocol", New Data Chunk for Stream Control Transmission Protocol",
draft-ietf-tsvwg-sctp-ndata-00 (work in progress), draft-ietf-tsvwg-sctp-ndata-00 (work in progress),
February 2014. February 2014.
Authors' Addresses Authors' Addresses
Michael Tuexen Michael Tuexen
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