One document matched: draft-ietf-behave-turn-uri-03.txt
Differences from draft-ietf-behave-turn-uri-02.txt
Network Working Group M. Petit-Huguenin
Internet-Draft (Unaffiliated)
Intended status: Standards Track August 19, 2009
Expires: February 20, 2010
Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
draft-ietf-behave-turn-uri-03
Status of this Memo
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Abstract
This document defines two URI schemes and the resolution mechanism to
generate a list of server transport addresses that can be tried to
create a Traversal Using Relays around NAT (TURN) allocation.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Syntax of a TURN or TURNS URI . . . . . . . . . . . . . . . . 3
4. TURN or TURNS URI Resolution . . . . . . . . . . . . . . . . . 4
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7.1. TURN URI Registration . . . . . . . . . . . . . . . . . . 8
7.2. TURNS URI Registration . . . . . . . . . . . . . . . . . . 8
7.3. RELAY Application Service Tag Registration . . . . . . . . 9
7.4. turn.udp Application Protocol Tag Registration . . . . . . 9
7.5. turn.tcp Application Protocol Tag Registration . . . . . . 10
7.6. turn.tls Application Protocol Tag Registration . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Release notes . . . . . . . . . . . . . . . . . . . . 11
A.1. Modifications between ietf-03 and ietf-02 . . . . . . . . 11
A.2. Modifications between ietf-02 and ietf-01 . . . . . . . . 12
A.3. Modifications between ietf-01 and ietf-00 . . . . . . . . 12
A.4. Modifications between petithuguenin-03 and ietf-00 . . . . 12
A.5. Modifications between petithuguenin-03 and
petithuguenin-02 . . . . . . . . . . . . . . . . . . . . . 12
A.6. Modifications between petithuguenin-02 and
petithuguenin-01 . . . . . . . . . . . . . . . . . . . . . 12
A.7. Modifications between petithuguenin-01 and
petithuguenin-00 . . . . . . . . . . . . . . . . . . . . . 13
A.8. Design Notes . . . . . . . . . . . . . . . . . . . . . . . 13
A.9. Running Code Considerations . . . . . . . . . . . . . . . 13
A.10. TODO List . . . . . . . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
The TURN specification [I-D.ietf-behave-turn] defines a process for a
TURN client to find TURN servers by using DNS SRV resource records,
but this process does not let the TURN server administrators
provision the preferred TURN transport protocol between the client
and the server and for the TURN client to discover this preference.
This document defines a S-NAPTR application [RFC3958] for this
purpose. This application defines "RELAY" as an application service
tag and "turn.udp", "turn.tcp", and "turn.tls" as application
protocol tags.
To simplify the provisioning of TURN clients, this document also
defines a TURN and a TURNS URI scheme and a resolution mechanism to
convert these URIs into a list of IP addresses, ports and TURN
transport protocols.
Another usage of the resolution mechanism described in this document
would be Remote Hosting as described in [RFC3958] section 4.4. For
example a VoIP provider who does not want to deploy TURN servers
could use the servers deployed by another company but could still
want to provide configuration parameters to its customers without
explicitly showing this relationship. The mechanism permits one to
implement this indirection, without preventing the company hosting
the TURN servers from managing them as it see fit.
2. Terminology
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. Syntax of a TURN or TURNS URI
A TURN/TURNS URI has the following ABNF syntax [RFC5234]:
turnURI = scheme ":" host [ ":" port ] [ "?transport=" transport ]
scheme = "turn" / "turns"
transport = "udp" / "tcp" / transport-ext
transport-ext = 1*unreserved
<host>, <port> and <unreserved> are specified in [RFC3986].
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4. TURN or TURNS URI Resolution
The URI resolution mechanism is used only to create an allocation.
All other transactions use the IP address, transport and port used
for a successful allocation creation.
The URI resolution algorithm uses <scheme>, <host>, <port> and
<transport> as input. It also uses as input a list ordered by
preference of TURN transports (UDP, TCP, TLS) supported by the
application using the TURN client. The output of the algorithm is a
list of {IP address, transport, port} tuples that a TURN client can
try in order to create an allocation on a TURN server.
An Allocate error response as specified in section 6.4 of
[I-D.ietf-behave-turn] is processed as a failure as specified by
[RFC3958] section 2.2.4. The resolution stops when a TURN client
gets a successful Allocate response from a TURN server. After an
allocation succeeds or all the allocations fail, the resolution
context MUST be discarded and the URI resolution algorithm MUST be
restarted from the beginning for any subsequent allocation. Servers
blacklisted as described in section 6.4 of [I-D.ietf-behave-turn]
should not be used for the specified duration even if returned by a
subsequent resolution.
First the resolution algorithm checks that the URI can be resolved
with the list of TURN transports supported by the application:
o If <scheme> is defined as "turn" and <transport> is defined as
"udp" but the list of TURN transports supported by the application
does not contain UDP then the resolution MUST stop with an error.
o If <scheme> is defined as "turn" and <transport> is defined as
"tcp" but the list of TURN transports supported by the application
does not contain TCP then the resolution MUST stop with an error.
o If <scheme> is defined as "turns" and <transport> is defined as
"udp" then the algorithm MUST stop with an error.
o If <scheme> is defined as "turns" and <transport> is defined as
"tcp" but the list of TURN transports supported by the application
does not contain TLS then the resolution MUST stop with an error.
o If <scheme> is defined as "turns" and <transport> is not defined
but the list of TURN transports supported by the application does
not contain TLS then the resolution MUST stop with an error.
o If <transport> is defined but unknown then the resolution MUST
stop with an error.
After verifying the validity of the URI elements, the algorithm
applies the steps described below. Note that in some steps, <scheme>
and <transport> have to be converted to a TURN transport. If
<scheme> is defined as "turn" and <transport> is defined as "udp"
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then the TURN UDP transport is used. If <scheme> is defined as
"turn" and <transport> is defined as "tcp" then the TURN TCP
transport is used. If <scheme> is defined as "turns" and <transport>
is defined as "tcp" then the TURN TLS transport is used. This is
summarized in Table 1.
+----------+-------------+----------------+
| <scheme> | <transport> | TURN Transport |
+----------+-------------+----------------+
| "turn" | "udp" | UDP |
| "turn" | "tcp" | TCP |
| "turns" | "tcp" | TLS |
+----------+-------------+----------------+
Table 1
1. If <host> is an IP address then it indicates the specific IP
address to be used. If <port> is not defined, the default port
declared in [I-D.ietf-behave-turn] for the SRV service name
defined in <scheme> is used. If <transport> is defined then
<scheme> and <transport> are converted to a TURN transport as
specified in Table 1. If <transport> is not defined, the TURN
transports supported by the application are tried by preference
order. If the TURN client cannot contact a TURN server with this
IP address and port on any of the transports supported by the
application then the resolution MUST stop with an error.
2. If <host> is a domain name and <port> is defined, then <host> is
resolved to a list of IP addresses via DNS A and AAAA queries.
If <transport> is defined, then <scheme> and <transport> are
converted to a TURN transport as specified in Table 1. If
<transport> is not defined, the TURN transports supported by the
application are tried in preference order. If the TURN client
cannot contact a TURN server with this port and any combination
of transports supported by the application and resolved IP
addresses then the resolution MUST stop with an error. The TURN
client can choose the order to contact the resolved IP addresses
in any implementation-specific way.
3. If <host> is a domain name and <port> is not defined but
<transport> is defined, then <host> is converted to a list of IP
address and port tuples via a DNS SRV query as defined in
[I-D.ietf-behave-turn] section 6.1. <scheme> is used for the
service name and <transport> is used for the protocol name in the
SRV algorithm [RFC2782]. If the TURN client cannot contact a
TURN server at any of the IP address, port and transport tuples
returned by the SRV algorithm then the resolution MUST stop with
an error. The SRV algorithm recommends doing an A query if the
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SRV query returns an error or no SRV RR. In this case the
default port declared in [I-D.ietf-behave-turn] for the SRV
service name defined in <scheme> must be used for contacting the
TURN server. Also in this case, this specification modifies the
SRV algorithm by recommending an A and AAAA query.
4. If <host> is a domain name and <port> and <transport> are not
defined, then <host> is converted to an ordered list of IP
address, port and transport tuples via the S-NAPTR algorithm
defined in [RFC3958] with a "RELAY" Application Service Tag. The
TURN transports supported by the application are converted in
Application Protocol Tags by using "turn.udp" if the TURN
transport is UDP, "turn.tcp" if the TURN transport is TCP and
"turn.tls" if the TURN transport is TLS. The order to try the
protocol tags is provided by the ranking of the first set of
NAPTR records. If multiple protocol tags have the same ranking,
the preferred order set by the application is used. If the TURN
client cannot contact a TURN server with any of the IP address,
port and transport tuples returned by the S-NAPTR algorithm, then
the resolution MUST stop with an error. If the first NAPTR SRV
query does not return any result then <host> is converted to a
list of IP address and port tuples by using the algorithm
specified in step 3 for each of the TURN transports supported by
the application in order of preference.
5. Example
With the DNS RRs in Figure 1 and an ordered TURN transport list of
{TLS, TCP, UDP}, the resolution algorithm will convert the "turn:
example.com" URI to the list of IP addresses, port and protocol
tuples in Table 2.
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example.com.
IN NAPTR 100 10 "" "RELAY:turn.udp" "" datagram.example.com.
IN NAPTR 200 10 "" "RELAY:turn.tcp:turn.tls" "" stream.example.com.
datagram.example.com.
IN NAPTR 100 10 "S" "RELAY:turn.udp" "" _udp._turn.example.com.
stream.example.com.
IN NAPTR 100 10 "S" "RELAY:turn.tcp" "" _turn._tcp.example.com.
IN NAPTR 200 10 "A" "RELAY:turn.tls" "" a.example.com.
_turn._udp.example.com.
IN SRV 0 0 3478 a.example.com.
_turn._tcp.example.com.
IN SRV 0 0 5000 a.example.com.
a.example.com.
IN A 192.0.2.1
Figure 1
+-------+----------+------------+------+
| Order | Protocol | IP address | Port |
+-------+----------+------------+------+
| 1 | UDP | 192.0.2.1 | 3478 |
| 2 | TLS | 192.0.2.1 | 5349 |
| 3 | TCP | 192.0.2.1 | 5000 |
+-------+----------+------------+------+
Table 2
6. Security Considerations
Security considerations for TURN are discussed in
[I-D.ietf-behave-turn].
The Application Service Tag and Application Protocol Tags defined in
this document do not introduce any specific security issues beyond
the security considerations discussed in [RFC3958].
The "turn" and "turns" URI schemes do not introduce any specific
security issues beyond the security considerations discussed in
[RFC3986].
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7. IANA Considerations
This section contains the registration information for the "turn" and
"turns" URI Schemes (in accordance with [RFC4395]), one S-NAPTR
Application Service Tag, and three S-NAPTR Application Protocol Tags
(in accordance with [RFC3958]).
7.1. TURN URI Registration
URI scheme name: turn
Status: permanent
URI scheme syntax: See Section 3.
URI scheme semantics: See Section 4.
Encoding considerations: There are no encoding considerations beyond
those in [RFC3986].
Applications/protocols that use this URI scheme name:
The "turn" URI scheme is intended to be used by applications that
might need access to a TURN server.
Interoperability considerations: N/A
Security considerations: See Section 6.
Contact: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
References: This document.
7.2. TURNS URI Registration
URI scheme name: turns
Status: permanent
URI scheme syntax: See Section 3.
URI scheme semantics: See Section 4.
Encoding considerations: There are no encoding considerations beyond
those in [RFC3986].
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Applications/protocols that use this URI scheme name:
The "turns" URI scheme is intended to be used by applications that
might need access to a TURN server.
Interoperability considerations: N/A
Security considerations: See Section 6.
Contact: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
References: This document.
7.3. RELAY Application Service Tag Registration
Application Protocol Tag: RELAY
Intended usage: See Section 4.
Interoperability considerations: N/A
Security considerations: See Section 6.
Relevant publications: This document.
Contact information: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
7.4. turn.udp Application Protocol Tag Registration
Application Protocol Tag: turn.udp
Intended usage: See Section 4.
Interoperability considerations: N/A
Security considerations: See Section 6.
Relevant publications: This document.
Contact information: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
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7.5. turn.tcp Application Protocol Tag Registration
Application Protocol Tag: turn.tcp
Intended usage: See Section 4.
Interoperability considerations:
Security considerations: See Section 6.
Relevant publications: This document.
Contact information: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
7.6. turn.tls Application Protocol Tag Registration
Application Protocol Tag: turn.tls
Intended usage: See Section 4.
Interoperability considerations: N/A
Security considerations: See Section 6.
Relevant publications: This document.
Contact information: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
8. Acknowledgements
Thanks to Dave Thaler, Alfred E. Heggestad, Eilon Yardeni, Dan Wing,
Alfred Hoenes and Jim Kleck for their comments, suggestions and
questions that helped to improve this document.
This document was written with the xml2rfc tool described in
[RFC2629].
9. References
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9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[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.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[I-D.ietf-behave-turn]
Rosenberg, J., Mahy, R., and P. Matthews, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)",
draft-ietf-behave-turn-16 (work in progress), July 2009.
9.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35,
RFC 4395, February 2006.
URIs
[1] <http://www.croczilla.com/zap>
[2] <http://ietf.implementers.org/turn-uri-0.1.zip>
Appendix A. Release notes
This section must be removed before publication as an RFC.
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A.1. Modifications between ietf-03 and ietf-02
o A turn:<host>?transport=TCP URI fails if the list of supported
transports contains only TLS. Using a TLS transport in this case
was underspecified.
o Reordered paragraphes in section 4.
o Added table for conversion of <scheme> and <transport> to TURN
transport.
o Various editorial modifications.
o SRV algorithm changed to "...recommending an A and AAAA query."
o Put back the changelog for the versions before been accepted as WG
item.
A.2. Modifications between ietf-02 and ietf-01
o Shorten the abstract so it does not overflow on the second page.
o Added text to explicitly say that the resolution is only to create
an allocation.
o Added text about failures.
o Fixed the default port for TLS in the example.
o Changed some priority in the example for RFC3958 section 2.2.5.
o Fixed the service/protocol order for the SRV RR in the example.
o Removed reference to draft-wood-tae-specifying-uri-transports as
it has an experimental status.
A.3. Modifications between ietf-01 and ietf-00
o Fixed the contact email.
o Changed the IPR to trust200902.
o Added case for transport defined but unknown.
o Moved RFC 3958 to Normative References.
o Added study of draft-wood-tae-specifying-uri-transports in TODO
list.
A.4. Modifications between petithuguenin-03 and ietf-00
o Renamed the document to "draft-ietf-behave-turn-uri".
o Changed author affiliation.
o Fixed the text in the IANA considerations.
A.5. Modifications between petithuguenin-03 and petithuguenin-02
o Added Running Code Consideration section.
o Added Remote Hosting example in introduction.
o Changed back to opaque URIs because of [RFC4395] Section 2.2. Now
use "?" as separator.
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o Added IANA considerations section.
o Added security considerations section.
A.6. Modifications between petithuguenin-02 and petithuguenin-01
o Receiving a successful Allocate response stops the resolution
mechanism and the resolution context must be discarded after this.
o Changed from opaque to hierarchical URIs because the ";" character
is used in <reg-name>.
o Various nits.
A.7. Modifications between petithuguenin-01 and petithuguenin-00
o Added <transport-ext> in the ABNF.
o Use the <rulename> and "literal" usages for free-form text defined
by [RFC5234].
o Fixed various typos.
o Put the rule to convert <scheme> and <transport> to a TURN
transport in a separate paragraph.
o Modified the SRV usage to be in line with RFC 2782.
o Clarified that the NAPTR protocol ranking must be used before the
application ranking.
o Added an example.
o Added release notes.
A.8. Design Notes
o The Application Service Tag is "RELAY" so other relaying
mechanisms than TURN (e.g., TWIST) can be registered as
Application Protocol Tags.
o S-NAPTR was preferred to U-NAPTR because there is no use case for
U-NAPTR.
o <password> is not used in the URIs because it is deprecated.
<username> is not used in the URIs because it is not used to guide
the resolution mechanism.
o As discussed in Dublin, there is no generic parameters in the URI
to prevent compatibity issues.
o Adding optional capabilities (IPv6 allocation, preserve bit,
etc...) in the resolution process was rejected at the Dublin
meeting.
A.9. Running Code Considerations
o Zap [1]. Eilon Yardeni, 8x8 Inc. Implements version -00
o Reference Implementation of TURN URI parser and resolver. [2].
Marc Petit-Huguenin. Implements version -00 to -02
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A.10. TODO List
(Empty)
Author's Address
Marc Petit-Huguenin
(Unaffiliated)
Email: petithug@acm.org
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