TRAM M. Petit-Huguenin
Internet-Draft Jive Communications
Updates: 5928, 7065 (if approved) G. Salgueiro
Intended status: Standards Track Cisco Systems
Expires: August 4, 2014 January 31, 2014
Datagram Transport Layer Security (DTLS) as Transport for Traversal
Using Relays around NAT (TURN)
draft-petithuguenin-tram-turn-dtls-00
Abstract
This document specifies the usage of Datagram Transport Layer
Security (DTLS) [RFC6347] as a transport protocol between a Traversal
Using Relays around NAT (TURN) [RFC5766] client and a TURN server.
It also specifies modifications to the TURN URIs [RFC7065] and to the
TURN resolution mechanism [RFC5928] to facilitate the resolution of
TURN URIs into the IP address and port of TURN servers supporting
DTLS as a transport protocol.
Status of This Memo
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This Internet-Draft will expire on August 4, 2014.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. DTLS as Transport for TURN . . . . . . . . . . . . . . . . . 3
4. DTLS Support in TURN URIs . . . . . . . . . . . . . . . . . . 3
5. Resolution Mechanism for TURN over DTLS . . . . . . . . . . . 3
6. Implementation Status . . . . . . . . . . . . . . . . . . . . 4
6.1. turnuri . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
TURN [RFC5766] defines Transport Layer Security (TLS) over TCP
(simply referred to as TLS [RFC5246]) as the transport for TURN due
to additional security advantages it offers over plain UDP or TCP
transport. But TLS-over-TCP is not an optimal transport when TURN is
used for its originally intended purpose, which is to support
multimedia sessions. This sub-optimality primarily stems from the
added latency incurred by the TCP-based head-of-line (HOL) blocking
problem coupled with additional TLS buffering (for integrity checks).
This is a well documented and understood transport limitation for
secure real-time communications.
TLS-over-UDP (referred to as DTLS [RFC6347]) offers the same security
advantages as TLS-over-TCP, but without the undesirable latency
concerns.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in [RFC2119] when
they appear in ALL CAPS. When these words are not in ALL CAPS (such
as "must" or "Must"), they have their usual English meanings, and are
not to be interpreted as RFC 2119 key words.
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3. DTLS as Transport for TURN
TURN [RFC5766] defines three combinations of transports/allocations:
UDP/UDP, TCP/UDP and TLS/UDP. This document adds DTLS/UDP as a valid
combination.
[RFC6062] states that TCP allocations cannot be obtained using a UDP
association between client and server. The fact that DTLS uses UDP
implies that TCP allocations MUST NOT be obtained using a DTLS
association between client and server.
By default, TURN over DTLS uses port 5349, the same port as TURN over
TLS. However, the SRV procedures can be implemented to use a
different port (as described in Section 6 of [RFC5766]. When using
SRV records, the service name MUST be set to "turns" and the
application name to "udp".
4. DTLS Support in TURN URIs
This document does not make any changes to the syntax of a TURN URI
[RFC7065]. As indicated in Section 3 of [RFC7065], secure transports
like TURN over TLS, and now TURN over DTLS, MUST use the "turns" URI
scheme. When using the "turns" URI scheme to designate TURN over
DTLS, the transport value of the TURN URI, if set, MUST be "udp".
5. Resolution Mechanism for TURN over DTLS
This document defines a new Straightforward Naming Authority Pointer
(S-NAPTR) application protocol tag: "turn.dtls".
The <transport> component, as provisioned or resulting from the
parsing of a TURN URI, is passed without modification to the TURN
resolution mechanism defined in Section 3 of [RFC5928], but with the
following alterations to that algorithm:
o The acceptable values for transport name are extended with the
addition of "dtls".
o The acceptable values in the ordered list of supported TURN
transports is extended with the addition of "Datagram Transport
Layer Security (DTLS)".
o The resolution algorithm ckeck rules list is extended with the
addition of the following step:
If <secure> is true and <transport> is defined as "udp" but the
list of TURN transports supported by the application does not
contain DTLS, then the resolution MUST stop with an error.
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o The 5th rule of the resolution algorithm check rules list is
modified to read like this:
If <secure> is true and <transport> is not defined but the list
of TURN transports supported by the application does not
contain TLS or DTLS, then the resolution MUST stop with an
error.
o Table 1 is modified to add the following line:
+----------+-------------+----------------+
| <secure> | <transport> | TURN Transport |
+----------+-------------+----------------+
| true | "udp" | DTLS |
+----------+-------------+----------------+
o In step 1 of the resolution algorithm the default port for DTLS is
5349.
o In step 4 of the resolution algorithm the following is added to
the list of conversions between the filtered list of TURN
transports supported by the application and application protocol
tags:
"turn.dtls" is used if the TURN transport is DTLS.
Note that using the [RFC5928] resolution mechanism does not imply
that additional round trips to the DNS server will be needed (e.g.,
the TURN client will start immediately if the TURN URI contains an IP
address).
6. Implementation Status
[[Note to RFC Editor: Please remove this section and the reference to
[RFC6982] before publication.]]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC6982].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
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According to [RFC6982], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
6.1. turnuri
Organization: Impedance Mismatch
Name: turnuri 0.5.0 http://debian.implementers.org/stable/source/
turnuri.tar.gz
Description: A reference implementation of the URI and resolution
mechanism defined in this document, RFC 7065 [RFC7065] and RFC
5928 [RFC5928].
Level of maturity: Beta.
Coverage: Fully implements the URIs and resolution mechanism
defined in this specification, in RFC 7065 and in RFC 5928.
Licensing: AGPL3
Implementation experience: TBD
Contact: Marc Petit-Huguenin <marc@petit-huguenin.org>.
7. Security Considerations
TURN over DTLS as a TURN transport does not introduce any specific
security considerations beyond those for TURN over TLS detailed in
[RFC5766].
The usage of "udp" as a transport parameter with the "turns" URI
scheme does not introduce any specific security issues beyond those
discussed in [RFC7065].
The new S-NAPTR application protocol tag defined in this document as
well as the modifications this document makes to the TURN resolution
mechanism described in [RFC5928] do not introduce any additional
security considerations beyond those outlined in [RFC5928].
8. IANA Considerations
This specification contains the registration information for one
S-NAPTR application protocol tags (in accordance with [RFC3958]).
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Application Protocol Tag: turn.dtls
Intended Usage: See Section 5
Interoperability considerations: N/A
Security considerations: See Section 7
Relevant publications: This document
Contact information: Marc Petit-Huguenin
Author/Change controller: The IESG
This specification also contains the registration information for one
Service Name and Transport Protocol Port Number (in accordance with
[RFC6335]).
Service Name: turns
Transport Protocol(s): UDP
Assignee: IESG
Contact: Marc Petit-Huguenin
Description: TURN over DTLS
Reference: This document
Port Number: 5349
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.
[RFC3958] Daigle, L. and A. Newton, "Domain-Based Application
Service Location Using SRV RRs and the Dynamic Delegation
Discovery Service (DDDS)", RFC 3958, January 2005.
[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766, April 2010.
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[RFC5928] Petit-Huguenin, M., "Traversal Using Relays around NAT
(TURN) Resolution Mechanism", RFC 5928, August 2010.
[RFC6062] Perreault, S. and J. Rosenberg, "Traversal Using Relays
around NAT (TURN) Extensions for TCP Allocations", RFC
6062, November 2010.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165, RFC
6335, August 2011.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
[RFC7065] Petit-Huguenin, M., Nandakumar, S., Salgueiro, G., and P.
Jones, "Traversal Using Relays around NAT (TURN) Uniform
Resource Identifiers", RFC 7065, November 2013.
9.2. Informative References
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", RFC 6982, July
2013.
Appendix A. Examples
Table 1 shows how the <secure>, <port> and <transport> components are
populated for a TURN URI that uses DTLS as its transport. For all
these examples, the <host> component is populated with "example.net".
+---------------------------------+----------+--------+-------------+
| URI | <secure> | <port> | <transport> |
+---------------------------------+----------+--------+-------------+
| turns:example.net?transport=udp | true | | DTLS |
+---------------------------------+----------+--------+-------------+
Table 1
With the DNS RRs in Figure 1 and an ordered TURN transport list of
{DTLS, TLS, TCP, UDP}, the resolution algorithm will convert the TURN
URI "turns:example.net" to the ordered list of IP address, port, and
protocol tuples in Table 2.
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example.net.
IN NAPTR 100 10 "" RELAY:turn.udp:turn.dtls "" datagram.example.net.
IN NAPTR 200 10 "" RELAY:turn.tcp:turn.tls "" stream.example.net.
datagram.example.net.
IN NAPTR 100 10 S RELAY:turn.udp "" _turn._udp.example.net.
IN NAPTR 100 10 S RELAY:turn.dtls "" _turns._udp.example.net.
stream.example.net.
IN NAPTR 100 10 S RELAY:turn.tcp "" _turn._tcp.example.net.
IN NAPTR 200 10 A RELAY:turn.tls "" a.example.net.
_turn._udp.example.net.
IN SRV 0 0 3478 a.example.net.
_turn._tcp.example.net.
IN SRV 0 0 5000 a.example.net.
_turns._udp.example.net.
IN SRV 0 0 5349 a.example.net.
a.example.net.
IN A 192.0.2.1
Figure 1
+-------+----------+------------+------+
| Order | Protocol | IP address | Port |
+-------+----------+------------+------+
| 1 | DTLS | 192.0.2.1 | 5349 |
| 2 | TLS | 192.0.2.1 | 5349 |
+-------+----------+------------+------+
Table 2
Authors' Addresses
Marc Petit-Huguenin
Jive Communications
1275 West 1600 North, Suite 100
Orem, UT 84057
USA
Email: marcph@getjive.com
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Gonzalo Salgueiro
Cisco Systems
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: gsalguei@cisco.com
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