draft-ietf-tram-turn-server-discovery-12.txt   rfc8155.txt 
TRAM P. Patil Internet Engineering Task Force (IETF) P. Patil
Internet-Draft T. Reddy Request for Comments: 8155 T. Reddy
Updates: 5766 (if approved) Cisco Updates: 5766 Cisco
Intended status: Standards Track D. Wing Category: Standards Track D. Wing
Expires: July 16, 2017 January 12, 2017 ISSN: 2070-1721 April 2017
TURN Server Auto Discovery Traversal Using Relays around NAT (TURN) Server Auto Discovery
draft-ietf-tram-turn-server-discovery-12
Abstract Abstract
Current Traversal Using Relays around NAT (TURN) server discovery Current Traversal Using Relays around NAT (TURN) server discovery
mechanisms are relatively static and limited to explicit mechanisms are relatively static and limited to explicit
configuration. These are usually under the administrative control of configuration. These are usually under the administrative control of
the application or TURN service provider, and not the enterprise, the application or TURN service provider, and not the enterprise,
ISP, or the network in which the client is located. Enterprises and ISP, or the network in which the client is located. Enterprises and
ISPs wishing to provide their own TURN servers need auto discovery ISPs wishing to provide their own TURN servers need auto-discovery
mechanisms that a TURN client could use with no or minimal mechanisms that a TURN client could use with minimal or no
configuration. This document describes three such mechanisms for configuration. This document describes three such mechanisms for
TURN server discovery. TURN server discovery.
This draft updates [RFC5766] to relax the requirement for mutual This document updates RFC 5766 to relax the requirement for mutual
authentication in certain cases. authentication in certain cases.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on July 16, 2017. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8155.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Discovery Procedure . . . . . . . . . . . . . . . . . . . . . 3 3. Discovery Procedure . . . . . . . . . . . . . . . . . . . . . 4
4. Discovery using Service Resolution . . . . . . . . . . . . . 4 4. Discovery Using Service Resolution . . . . . . . . . . . . . 5
4.1. Retrieving Domain Name . . . . . . . . . . . . . . . . . 5 4.1. Retrieving Domain Name . . . . . . . . . . . . . . . . . 5
4.1.1. DHCP . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1.1. DHCP . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.2. From own Identity . . . . . . . . . . . . . . . . . . 5 4.1.2. From Own Identity . . . . . . . . . . . . . . . . . . 6
4.2. Resolution . . . . . . . . . . . . . . . . . . . . . . . 6 4.2. Resolution . . . . . . . . . . . . . . . . . . . . . . . 6
5. DNS Service Discovery . . . . . . . . . . . . . . . . . . . . 6 5. DNS Service Discovery . . . . . . . . . . . . . . . . . . . . 6
5.1. mDNS . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. mDNS . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Discovery using Anycast . . . . . . . . . . . . . . . . . . . 7 6. Discovery Using Anycast . . . . . . . . . . . . . . . . . . . 7
7. Deployment Considerations . . . . . . . . . . . . . . . . . . 8 7. Deployment Considerations . . . . . . . . . . . . . . . . . . 8
7.1. Mobility and Changing IP addresses . . . . . . . . . . . 8 7.1. Mobility and Changing IP Addresses . . . . . . . . . . . 8
7.2. Recursively Encapsulated TURN . . . . . . . . . . . . . . 8 7.2. Recursively Encapsulated TURN . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8.1. IPv4 Anycast . . . . . . . . . . . . . . . . . . . . . . 8 8.1. IPv4 Anycast . . . . . . . . . . . . . . . . . . . . . . 9
8.2. IPv6 Anycast . . . . . . . . . . . . . . . . . . . . . . 9 8.2. IPv6 Anycast . . . . . . . . . . . . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 9. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9.1. Service Resolution . . . . . . . . . . . . . . . . . . . 11 9.1. Service Resolution . . . . . . . . . . . . . . . . . . . 12
9.2. DNS Service Discovery . . . . . . . . . . . . . . . . . . 11 9.2. DNS Service Discovery . . . . . . . . . . . . . . . . . . 12
9.3. Anycast . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.3. Anycast . . . . . . . . . . . . . . . . . . . . . . . . . 13
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 10.1. Normative References . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . 12 10.2. Informative References . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . 14 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
TURN [RFC5766] is a protocol that is often used to improve the TURN [RFC5766] is a protocol that is often used to improve the
connectivity of Peer-to-Peer (P2P) applications (as defined in connectivity of Peer-to-Peer (P2P) applications (as defined in
section 2.7 of [RFC5128]). TURN allows a connection to be Section 2.7 of [RFC5128]). TURN allows a connection to be
established when one or both sides are incapable of a direct P2P established when one or both sides are incapable of a direct P2P
connection. It is an important building block for interactive, real- connection. It is an important building block for interactive, real-
time communication using audio, video, collaboration etc. time communication using audio, video, collaboration, etc.
While TURN services are extensively used today, the means to auto While TURN services are extensively used today, the means to
discover TURN servers do not exist. TURN clients are usually automatically discover TURN servers do not exist. TURN clients are
explicitly configured with a well known TURN server. To allow TURN usually explicitly configured with a well-known TURN server. To
applications to operate seamlessly across different types of networks allow TURN applications to operate seamlessly across different types
and encourage the use of TURN without the need for manual of networks and encourage the use of TURN without the need for manual
configuration, it is important that there exists an auto discovery configuration, it is important that there exist an auto-discovery
mechanism for TURN services. Web Real-Time Communication (WebRTC) mechanism for TURN services. Web Real-Time Communication (WebRTC)
[I-D.ietf-rtcweb-overview] usages and related extensions, which are [WebRTC-Overview] usages and related extensions, which are mostly
mostly based on web applications, need TURN server discovery based on web applications, need TURN server discovery mechanisms.
mechanisms.
This document describes three discovery mechanisms, so as to maximize This document describes three discovery mechanisms, so as to maximize
opportunity for discovery, based on the network in which the TURN the opportunity for discovery, based on the network in which the TURN
client finds itself. The three discovery mechanisms are: client finds itself. The three discovery mechanisms are:
o A resolution mechanism based on straightforward Naming Authority o A resolution mechanism based on Straightforward-Naming Authority
Pointer (S-NAPTR) resource records in the Domain Name System Pointer (S-NAPTR) resource records in the Domain Name System
(DNS). [RFC5928] describes details on retrieving a list of server (DNS). [RFC5928] describes details on retrieving a list of server
transport addresses from DNS that can be used to create a TURN transport addresses from the DNS that can be used to create a TURN
allocation. allocation.
o DNS Service Discovery o DNS Service Discovery.
o A mechanism based on anycast address for TURN. o A mechanism based on an anycast address for TURN.
In general, if a client wishes to communicate using one of its In general, if a client wishes to communicate using one of its
interfaces using a specific IP address family, it SHOULD query the interfaces using a specific IP address family, it SHOULD query the
TURN server(s) that has been discovered for that specific interface TURN server(s) that has been discovered for that specific interface
and address family. How to select an interface and IP address family and address family. How to select an interface and IP address family
is out of the scope of this document. is out of the scope of this document.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
3. Discovery Procedure 3. Discovery Procedure
TURN clients, by default, discover TURN server(s) by means of local TURN clients, by default, discover TURN server(s) by means of local
or manual TURN configuration (i.e., TURN servers configured at the or manual TURN configuration (i.e., TURN servers configured at the
system level). Configuration discovered from an application, e.g., a system level). Configuration discovered from an application, e.g., a
Java Script specified TURN server for Web Real-Time Communication JavaScript-specified TURN server for Web Real-Time Communication
(WebRTC) [I-D.ietf-rtcweb-overview] usages and related extensions, is (WebRTC) [WebRTC-Overview] usages and related extensions, is
considered as local configuration. An implementation may give the considered a local configuration. An implementation may give the
user an opportunity (e.g., by means of configuration file options or user an opportunity (e.g., by means of configuration file options or
menu items) to specify a TURN server for each address family. A menu items) to specify a TURN server for each address family. A
client can choose auto-discovery in the absence of local client can choose auto-discovery in the absence of local
configuration, if local configuration doesn't work or in addition to configuration, if local configuration doesn't work or in addition to
local configuration. This document does not offer a recommendation local configuration. This document does not offer a recommendation
on server selection. on server selection.
A TURN client that implements the auto discovery algorithm, to A TURN client that implements the auto-discovery algorithm, to
discover TURN servers in the attached network, uses the following discover TURN servers in the attached network, uses the following
mechanisms for discovery: mechanisms for discovery:
o Service Resolution : The TURN client attempts to perform TURN o Service Resolution: The TURN client attempts to perform TURN
service resolution using the host's DNS domain. service resolution using the host's DNS domain.
o DNS SD: DNS Service Discovery. o DNS SD: DNS Service Discovery.
o Anycast : Send TURN allocate request to the assigned TURN anycast o Anycast: Send TURN Allocation request to the assigned TURN anycast
request for each combination of interface and address family. request for each combination of interface and address family.
Not all TURN servers may be discovered using NAPTR records or DNS SD; Not all TURN servers may be discovered using NAPTR records or DNS SD.
Similarly, not all TURN servers may support anycast. For best Similarly, not all TURN servers may support anycast. For best
results, a client SHOULD implement all discovery mechanisms described results, a client SHOULD implement all the discovery mechanisms
above. described above.
The document does not prescribe a strict order that a client must The document does not prescribe a strict order that a client must
follow for discovery. An implementation may choose to perform all follow for discovery. An implementation may choose to perform all
the above steps in parallel for discovery OR choose to follow any the above steps in parallel for discovery OR choose to follow any
desired order and stop the discovery procedure if a mechanism desired order and stop the discovery procedure if a mechanism
succeeds. succeeds.
On hosts with more than one interface or address family (IPv4/v6), On hosts with more than one interface or address family (IPv4/v6),
the TURN server discovery procedure has to be performed for each the TURN server discovery procedure has to be performed for each
combination of interface and address family. A client MAY choose to combination of interface and address family. A client MAY choose to
perform the discovery procedure only for a desired interface/address perform the discovery procedure only for a desired interface/address
combination if the client does not wish to discover a TURN server for combination if the client does not wish to discover a TURN server for
all combinations of interface and address family. all combinations of interface and address family.
4. Discovery using Service Resolution 4. Discovery Using Service Resolution
This mechanism is performed in two steps: This mechanism is performed in two steps:
1. A DNS domain name is retrieved for each combination of interface 1. A DNS domain name is retrieved for each combination of interface
and address family. and address family.
2. Retrieved DNS domain names are then used for S-NAPTR lookups as 2. Retrieved DNS domain names are then used for S-NAPTR lookups as
per [RFC5928]. Further DNS lookups may be necessary to determine per [RFC5928]. Further DNS lookups may be necessary to determine
TURN server IP address(es). TURN server IP address(es).
4.1. Retrieving Domain Name 4.1. Retrieving Domain Name
A client has to determine the domain in which it is located. The A client has to determine the domain in which it is located. The
following sections provide two possible mechanisms to learn the following sections provide two possible mechanisms to learn the
domain name, but other means of retrieving domain names may be used, domain name, but other means of retrieving domain names may be used,
which are outside the scope of this document e.g. local which are outside the scope of this document, e.g., local
configuration. configuration.
Implementations may allow the user to specify a default name that is Implementations may allow the user to specify a default name that is
used if no specific name has been configured. used if no specific name has been configured.
4.1.1. DHCP 4.1.1. DHCP
DHCP can be used to determine the domain name related to an DHCP can be used to determine the domain name related to an
interface's point of network attachment. Network operators may interface's point of network attachment. Network operators may
provide the domain name to be used for service discovery within an provide the domain name to be used for service discovery within an
access network using DHCP. Sections 3.2 and 3.3 of [RFC5986] define access network using DHCP. Sections 3.2 and 3.3 of [RFC5986] define
DHCP IPv4 and IPv6 access network domain name options, DHCP IPv4 and IPv6 access network domain name options,
OPTION_V4_ACCESS_DOMAIN and OPTION_V6_ACCESS_DOMAIN respectively, to OPTION_V4_ACCESS_DOMAIN and OPTION_V6_ACCESS_DOMAIN respectively, to
identify a domain name that is suitable for service discovery within identify a domain name that is suitable for service discovery within
the access network. the access network.
For IPv4, the discovery procedure MUST request the access network For IPv4, the discovery procedure MUST request the access network
domain name option in a Parameter Request List option, as described domain name option in a Parameter Request List option, as described
in [RFC2131]. [RFC2132] defines the DHCP IPv4 domain name option; in [RFC2131]. [RFC2132] defines the DHCP IPv4 domain name option;
while this option is less suitable, a client MAY request for it if while this option is less suitable, a client MAY request it if the
the access network domain name defined in [RFC5986] is not available. access network domain name defined in [RFC5986] is not available.
For IPv6, the discovery procedure MUST request for the access network For IPv6, the discovery procedure MUST request the access network
domain name option in an Options Request Option (ORO) within an domain name option in an Options Request Option (ORO) within an
Information-request message, as described in [RFC3315]. Information-request message, as described in [RFC3315].
If neither option can be retrieved the procedure fails for this If neither option can be retrieved, the procedure fails for this
interface. If a result can be retrieved it will be used as an input interface. If a result can be retrieved, it will be used as an input
for S-NAPTR resolution. for S-NAPTR resolution.
4.1.2. From own Identity 4.1.2. From Own Identity
For a TURN client with an understanding of the protocol mechanics of For a TURN client with an understanding of the protocol mechanics of
calling applications, the client may wish to extract the domain name calling applications, the client may wish to extract the domain name
from its own identity i.e canonical identifier used to reach the from its own identity, i.e, the canonical identifier used to reach
user. the user.
Example Example:
SIP : 'sip:alice@example.com' SIP : 'sip:alice@example.com'
Bare JID : 'alice@example.com' Bare JID : 'alice@example.com'
email : 'alice@example.com' email : 'alice@example.com'
'example.com' is retrieved from the above examples. 'example.com' is retrieved from the above examples.
A client may support multiple users, potentially with different A client may support multiple users, potentially with different
domains, or for a single user to use different domains for different domains, or a single user utilizing different domains for different
services. The means to choose and extract the domain name may be services. The means to choose and extract the domain name may be
different based on the type of identifier, service being used etc., different based on the type of identifier, service being used, etc.,
which are outside the scope of this document. which are outside the scope of this document.
4.2. Resolution 4.2. Resolution
Once the TURN discovery procedure has retrieved domain names, the Once the TURN discovery procedure has retrieved domain names, the
resolution mechanism described in [RFC5928] is followed. An S-NAPTR resolution mechanism described in [RFC5928] is followed. An S-NAPTR
lookup with 'RELAY' application service and the desired protocol tag lookup with the 'RELAY' application service and the desired protocol
is made to obtain information necessary to connect to the tag is made to obtain the information necessary to connect to the
authoritative TURN server within the given domain. authoritative TURN server within the given domain.
If no TURN-specific S-NAPTR records can be retrieved, the discovery If no TURN-specific S-NAPTR records can be retrieved, the discovery
procedure fails for this domain name (and the corresponding interface procedure fails for this domain name (and the corresponding interface
and IP protocol version). If more domain names are known, the and IP protocol version). If more domain names are known, the
discovery procedure may perform the corresponding S-NAPTR lookups discovery procedure may perform the corresponding S-NAPTR lookups
immediately. However, before retrying a lookup that has failed, a immediately. However, before retrying a lookup that has failed, a
client must wait a time period that is appropriate for the client must wait a time period that is appropriate for the
encountered error (NXDOMAIN, timeout, etc.). encountered error (NXDOMAIN, timeout, etc.).
skipping to change at page 7, line 26 skipping to change at page 7, line 36
o "_turns._udp.local." o "_turns._udp.local."
o "_turns._tcp.local" o "_turns._tcp.local"
A TURN server can send out gratuitous multicast DNS answer packets A TURN server can send out gratuitous multicast DNS answer packets
whenever it starts up, wakes from sleep, or detects a change in whenever it starts up, wakes from sleep, or detects a change in
network configuration. TURN clients receive these gratuitous packets network configuration. TURN clients receive these gratuitous packets
and cache information contained in it. and cache information contained in it.
6. Discovery using Anycast 6. Discovery Using Anycast
IP anycast can also be used for TURN service discovery. A packet IP anycast can also be used for TURN service discovery. A packet
sent to an anycast address is delivered to the "topologically sent to an anycast address is delivered to the "topologically
nearest" network interface with the anycast address. Using the TURN nearest" network interface with the anycast address. Using the TURN
anycast address, the only two things that need to be deployed in the anycast address, the only two things that need to be deployed in the
network for discovery are the two things that actually use TURN. network for discovery are the two things that actually use TURN.
When a client requires TURN services, it sends a TURN allocate When a client requires TURN services, it sends a TURN Allocation
request to the assigned anycast address. A TURN anycast server request to the assigned anycast address. A TURN anycast server
performs checks 1 to 7 discussed in Section 6.2 of [RFC5766]. If all performs checks 1 through 7 discussed in Section 6.2 of [RFC5766].
checks pass, the TURN anycast server MUST respond with a 300 (Try If all checks pass, the TURN anycast server MUST respond with a 300
Alternate) error as described in Section 2.9 of [RFC5766]; The (Try Alternate) error as described in Section 2.9 of [RFC5766]; the
response contains the TURN unicast address in the ALTERNATE-SERVER response contains the TURN unicast address in the ALTERNATE-SERVER
attribute. For subsequent communication with the TURN server, the attribute. For subsequent communication with the TURN server, the
client uses the responding server's unicast address. This has to be client uses the responding server's unicast address. This has to be
done because two packets addressed to an anycast address may reach done because two packets addressed to an anycast address may reach
two different anycast servers. The client, thus, also needs to two different anycast servers. The client, thus, also needs to
ensure that the initial request fits in a single packet. An ensure that the initial request fits in a single packet. An
implementation may choose to send out every new TURN Allocation implementation may choose to send out every new TURN Allocation
request to the anycast address to discover the closest and the most request to the anycast address to discover the closest and the most
optimal unicast address for the TURN server. optimal unicast address for the TURN server.
7. Deployment Considerations 7. Deployment Considerations
7.1. Mobility and Changing IP addresses 7.1. Mobility and Changing IP Addresses
A change of IP address on an interface may invalidate the result of A change of IP address on an interface may invalidate the result of
the TURN server discovery procedure. For instance, if the IP address the TURN server discovery procedure. For instance, if the IP address
assigned to a mobile host changes due to host mobility, it may be assigned to a mobile host changes due to host mobility, it may be
required to re-run the TURN server discovery procedure without required to re-run the TURN server discovery procedure without
relying on earlier gained information. New requests should be made relying on earlier gained information. New requests should be made
to the newly learned TURN servers learned after TURN discovery re- to the newly learned TURN servers that were learned after TURN the
run. However, if an earlier learned TURN server is still accessible discovery was re-run. However, if an earlier learned TURN server is
using the new IP address, procedures described for mobility using still accessible using the new IP address, procedures described for
TURN defined in [I-D.ietf-tram-turn-mobility] can be used for ongoing mobility using TURN defined in [RFC8016] can be used for ongoing
streams. streams.
7.2. Recursively Encapsulated TURN 7.2. Recursively Encapsulated TURN
WebRTC endpoints SHOULD treat any TURN server discovered through the WebRTC endpoints SHOULD treat any TURN server discovered through the
mechanisms described in this specification as an enterprise/gateway mechanisms described in this specification as an enterprise/gateway
or access network server, in accordance with Recursively Encapsulated or access network server, in accordance with Recursively Encapsulated
TURN [I-D.ietf-rtcweb-return]. TURN [RETURN].
8. IANA Considerations 8. IANA Considerations
8.1. IPv4 Anycast 8.1. IPv4 Anycast
IANA has assigned a single IPv4 address from the 192.0.0.0/24 prefix IANA has assigned a single IPv4 address from the 192.0.0.0/24 prefix
and registered it in the "IANA IPv4 Special-Purpose Address Registry" and registered it in the "IANA IPv4 Special-Purpose Address Registry"
[RFC6890]. [RFC6890].
+----------------------+-------------------------------------------+ +----------------------+-------------------------------------------+
| Attribute | Value | | Attribute | Value |
+----------------------+-------------------------------------------+ +----------------------+-------------------------------------------+
| Address Block | 192.0.0.???/32 (??? = TBD1 by IANA) | | Address Block | 192.0.0.10/32 |
| Name | Traversal Using Relays around NAT Anycast | | Name | Traversal Using Relays around NAT Anycast |
| RFC | TBD2 | | RFC | RFC 8155 |
| Allocation Date | TBD3 (Date of approval of this document) | | Allocation Date | 2017-02 |
| Termination Date | N/A | | Termination Date | N/A |
| Source | True | | Source | True |
| Destination | True | | Destination | True |
| Forwardable | True | | Forwardable | True |
| Global | True | | Global | True |
| Reserved-by-Protocol | False | | Reserved-by-Protocol | False |
+----------------------+-------------------------------------------+ +----------------------+-------------------------------------------+
8.2. IPv6 Anycast 8.2. IPv6 Anycast
IANA has assigned a single IPv6 address from the 2001:0000::/23 IANA has assigned a single IPv6 address from the 2001:0000::/23
prefix and registered it in the "IANA IPv6 Special-Purpose Address prefix and registered it in the "IANA IPv6 Special-Purpose Address
Registry" [RFC6890]. Registry" [RFC6890].
+----------------------+-------------------------------------------+ +----------------------+-------------------------------------------+
| Attribute | Value | | Attribute | Value |
+----------------------+-------------------------------------------+ +----------------------+-------------------------------------------+
| Address Block | 2001:1::???/128 (??? = TBD4 by IANA) | | Address Block | 2001:1::2/128 |
| Name | Traversal Using Relays around NAT Anycast | | Name | Traversal Using Relays around NAT Anycast |
| RFC | TBD2 | | RFC | RFC 8155 |
| Allocation Date | TBD3 (Date of approval of this document) | | Allocation Date | 2017-02 |
| Termination Date | N/A | | Termination Date | N/A |
| Source | True | | Source | True |
| Destination | True | | Destination | True |
| Forwardable | True | | Forwardable | True |
| Global | True | | Global | True |
| Reserved-by-Protocol | False | | Reserved-by-Protocol | False |
+----------------------+-------------------------------------------+ +----------------------+-------------------------------------------+
9. Security Considerations 9. Security Considerations
Use of Session Traversal Utilities for NAT (STUN) [RFC5389] Use of Session Traversal Utilities for NAT (STUN) [RFC5389]
authentication is OPTIONAL for TURN servers provided by the local authentication is OPTIONAL for TURN servers provided by the local
network or by the access network. A network provided TURN server MAY network or by the access network. A network-provided TURN server MAY
be configured to accept Allocation requests without STUN be configured to accept Allocation requests without STUN
authentication, and a TURN client MAY be configured to accept authentication, and a TURN client MAY be configured to accept
Allocation success responses without STUN authentication from a Allocation success responses without STUN authentication from a
network provided TURN server. network-provided TURN server.
Making STUN authentication optional is a downgrade of a MUST level Making STUN authentication optional is a downgrade of a MUST level
requirement defined in [RFC5766]. The downgrade allows TURN servers requirement defined in [RFC5766]. The downgrade allows TURN servers
provided by local or access network to accept Allocation requests provided by the local or access network to accept Allocation requests
from new and/or guest users in the network who do not necessarily from new and/or guest users in the network who do not necessarily
possess long term credentials for STUN authentication. The possess long term credentials for STUN authentication. The intention
intention, in such deployments, being to provide TURN services to all in such deployments is to provide TURN services to all users in the
users in the local or access network. However, this opens up a TURN local or access network. However, this opens up a TURN server to a
server to a variety of attacks described in Section 17 of [RFC5766]. variety of attacks described in Section 17 of [RFC5766]. A TURN
A TURN server in such cases must be configured to only process STUN server in such cases must be configured to only process STUN requests
requests from the trusted local network or subscribers of the access from the trusted local network or subscribers of the access network.
network. Operational measures must be taken in order protect the Operational measures must be taken in order to protect the TURN
TURN server; some of these measures include, but not limited to, server; some of these measures include, but are not limited to,
access control by means of access-lists, firewalls, subscriber quota access control by means of access lists, firewalls, subscriber quota
limits, ingress filtering etc. limits, ingress filtering, etc.
A TURN client in the absence of STUN long-term credential mechanism A TURN client in the absence of the STUN long-term credential
[RFC5389] or STUN Extension for Third-Party Authorization [RFC7635] mechanism [RFC5389] or the STUN Extension for Third-Party
MUST use (D)TLS unless it trusts the network infrastructure to defend Authorization [RFC7635] MUST use (D)TLS unless it trusts the network
against attacks discussed in [RFC5766]. It is RECOMMENDED that the infrastructure to defend against attacks discussed in [RFC5766]. It
TURN client use one of the following techniques with (D)TLS to is RECOMMENDED that the TURN client use one of the following
validate the TURN server: techniques with (D)TLS to validate the TURN server:
o For certificate-based authentication, a pre-populated trust anchor o For certificate-based authentication, a pre-populated trust anchor
store [RFC6024] allows a TURN client to perform path validation store [RFC6024] allows a TURN client to perform path validation
for the server certificate obtained during the (D)TLS handshake. for the server certificate obtained during the (D)TLS handshake.
If the client used a domain name to discover the TURN server, that If the client used a domain name to discover the TURN server, that
domain name also provides a mechanism for validation of the TURN domain name also provides a mechanism for validation of the TURN
server. The client MUST use the rules and guidelines given in server. The client MUST use the rules and guidelines given in
section 6 of [RFC6125] to validate the TURN server identity. Section 6 of [RFC6125] to validate the TURN server identity.
o Certification authorities that issue TURN server certificates o Certification authorities that issue TURN server certificates
SHOULD support the CN-ID, DNS-ID, SRV-ID and URI-ID identifier SHOULD support the CN-ID, DNS-ID, SRV-ID, and URI-ID identifier
types. TURN service providers SHOULD prefer the use of DNS-ID, types. TURN service providers SHOULD prefer the use of DNS-ID,
SRV-ID and URI-ID over CN-ID identifier types in certificate SRV-ID, and URI-ID over CN-ID identifier types in certificate
requests (as described in Section 2.3 from [RFC6125]) and the requests (as described in Section 2.3 from [RFC6125]) and the
wildcard character '*' SHOULD NOT be included in presented wildcard character '*' SHOULD NOT be included in the presented
identifier. identifier.
o For TURN servers that don't have a certificate trust chain (e.g., o For TURN servers that don't have a certificate trust chain (e.g.,
because they are on a home network or a corporate network), a because they are on a home network or a corporate network), a
configured list of TURN servers can contain the Subject Public Key configured list of TURN servers can contain the Subject Public Key
Info (SPKI) fingerprint of the TURN servers. The public key is Info (SPKI) fingerprint of the TURN servers. The public key is
used for the same reasons HTTP pinning [RFC7469] uses the public used for the same reasons HTTP pinning [RFC7469] uses the public
key. key.
o Raw public key-based authentication, as defined in [RFC7250], o Raw public key-based authentication, as defined in [RFC7250],
could also be used to authenticate a TURN server. could also be used to authenticate a TURN server.
An auto-discovered TURN server is considered to be only as trusted as An auto-discovered TURN server is considered to be only as trusted as
the path between the client and the TURN server. In order to safely the path between the client and the TURN server. In order to safely
use auto-discovered TURN servers for sessions with 'strict privacy' use auto-discovered TURN servers for sessions with 'strict privacy'
requirements, the user needs to be able to define privacy criteria requirements, the user needs to be able to define privacy criteria
(e.g. a trusted list of servers, networks, or domains) that are (e.g., a trusted list of servers, networks, or domains) that are
considered acceptable for such traffic. Any discovered TURN server considered acceptable for such traffic. Any discovered TURN server
outside the criteria is considered untrusted and therefore MUST NOT outside the criteria is considered untrusted and therefore MUST NOT
be used for privacy sensitive communication. be used for privacy-sensitive communication.
In some auto-discovery scenarios, it might not be possible for the In some auto-discovery scenarios, it might not be possible for the
TURN client to use (D)TLS authentication to validate the TURN server. TURN client to use (D)TLS authentication to validate the TURN server.
However, fall-back to clear text in such cases could leave the TURN However, fallback to clear text in such cases could leave the TURN
client open to on-path injection of spoofed TURN messages. A TURN client open to on-path injection of spoofed TURN messages. A TURN
client could fall back to encryption-only (D)TLS when (D)TLS client could fall back to encryption-only (D)TLS when (D)TLS
authentication is not available, but MUST NOT fall back without authentication is not available but MUST NOT fall back without
explicit administrator choice. Another reason to fall-back to explicit administrator choice. Another reason to fall back to
encryption-only is for privacy, which is analogous to SMTP encryption-only is for privacy, which is analogous to SMTP
opportunistic encryption [RFC7435] where one does not require privacy opportunistic encryption [RFC7435] where one does not require privacy
but one desires privacy when possible. but one desires privacy when possible.
In order to allow the TURN client to fallback to (D)TLS as described In order to allow the TURN client to fall back to (D)TLS as described
above, a TURN server that does not require either STUN long term above, a TURN server that does not require either STUN long-term
authentication [RFC5389] or STUN Extension for Third Party authentication [RFC5389] or STUN Extension for Third Party
Authorization [RFC7635] MUST support (D)TLS and if the network Authorization [RFC7635] MUST support (D)TLS and, if the network
infrastructure is capable of defending against attacks discussed in infrastructure is capable of defending against attacks discussed in
[RFC5766] then the TURN server MAY allow fallback to clear text. [RFC5766], then the TURN server MAY allow fallback to clear text.
A TURN client could fall back to clear text if it does not support A TURN client could fall back to clear text if it does not support
unauthenticated (D)TLS, but MUST NOT fall back without explicit unauthenticated (D)TLS but MUST NOT fall back without explicit
administrator choice. Fallback to clear text is NOT RECOMMENDED administrator choice. Fallback to clear text is NOT RECOMMENDED
because it makes the client more susceptible to man-in-the-middle because it makes the client more susceptible to man-in-the-middle
attacks and on-path packet injection. attacks and on-path packet injection.
9.1. Service Resolution 9.1. Service Resolution
The primary attack against the methods described in this document is The primary attack against the methods described in this document is
one that would lead to impersonation of a TURN server. An attacker one that would lead to impersonation of a TURN server. An attacker
could attempt to compromise the S-NAPTR resolution. Security could attempt to compromise the S-NAPTR resolution. Security
considerations described in [RFC5928] are applicable here as well. considerations described in [RFC5928] are applicable here as well.
skipping to change at page 11, line 41 skipping to change at page 12, line 26
the domain name, a host implementation needs to consider attacks the domain name, a host implementation needs to consider attacks
against each of the methods that are used. against each of the methods that are used.
If DHCP is used, the integrity of DHCP options is limited by the If DHCP is used, the integrity of DHCP options is limited by the
security of the channel over which they are provided. Physical security of the channel over which they are provided. Physical
security and separation of DHCP messages from other packets are security and separation of DHCP messages from other packets are
commonplace methods that can reduce the possibility of attack within commonplace methods that can reduce the possibility of attack within
an access network; alternatively, DHCP authentication [RFC3188] can an access network; alternatively, DHCP authentication [RFC3188] can
provide a degree of protection against modification. When using DHCP provide a degree of protection against modification. When using DHCP
discovery, clients are encouraged to use unicast DHCP INFORM queries discovery, clients are encouraged to use unicast DHCP INFORM queries
instead of broadcast queries which are more easily spoofed in instead of broadcast queries, which are more easily spoofed in
insecure networks. insecure networks.
9.2. DNS Service Discovery 9.2. DNS Service Discovery
Since DNS-SD is just a specification for how to name and use records Since DNS-SD is just a specification for how to name and use records
in the existing DNS system, it has no specific additional security in the existing DNS system, it has no specific additional security
requirements over and above those that already apply to DNS queries requirements over and above those that already apply to DNS queries
and DNS updates. For DNS queries, DNS Security Extensions (DNSSEC) and DNS updates. For DNS queries, DNS Security Extensions (DNSSEC)
[RFC4033] should be used where the authenticity of information is [RFC4033] should be used where the authenticity of information is
important. For DNS updates, secure updates [RFC2136][RFC3007] should important. For DNS updates, secure updates [RFC2136] [RFC3007]
generally be used to control which clients have permission to update should generally be used to control which clients have permission to
DNS records. update DNS records.
For mDNS, in addition to what has been described above, a principal For mDNS, in addition to what has been described above, a principal
security threat is a security threat inherent to IP multicast routing security threat is a security threat inherent to IP multicast routing
and any application that runs on it. A rogue system can advertise and any application that runs on it. A rogue system can advertise
that it is a TURN server. Discovery of such rogue systems as TURN that it is a TURN server. Discovery of such rogue systems as TURN
servers, in itself, is not a security threat if there is a means for servers, in itself, is not a security threat if there is a means for
the TURN client to authenticate and authorize the discovered TURN the TURN client to authenticate and authorize the discovered TURN
servers. servers.
9.3. Anycast 9.3. Anycast
skipping to change at page 12, line 31 skipping to change at page 13, line 21
Using an IANA-assigned well-known TURN anycast address enables border Using an IANA-assigned well-known TURN anycast address enables border
gateways to block such outgoing packets. In the default-free zone, gateways to block such outgoing packets. In the default-free zone,
routers should be configured to drop such packets. Such routers should be configured to drop such packets. Such
configuration can occur naturally via BGP messages advertising that configuration can occur naturally via BGP messages advertising that
no route exists to said address. no route exists to said address.
Sensitive clients that do not wish to leak information about their Sensitive clients that do not wish to leak information about their
presence can set an IP TTL on their TURN requests that limits how far presence can set an IP TTL on their TURN requests that limits how far
they can travel into the public Internet. they can travel into the public Internet.
10. Acknowledgements 10. References
The authors would like to thank Simon Perrault, Paul Kyzivat, Troy
Shields, Eduardo Gueiros, Ted Hardie, Bernard Aboba, Karl Stahl,
Brian Weis, Ralph Dromes, Ben Campbell, Suresh Krishnan and Brandon
Williams for their review and valuable comments. Thanks to Adam
Roach for his detailed review and suggesting DNS Service Discovery as
an additional discovery mechanism.
11. References
11.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and 10.1. Normative References
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", [RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997, RFC 2131, DOI 10.17487/RFC2131, March 1997,
<http://www.rfc-editor.org/info/rfc2131>. <http://www.rfc-editor.org/info/rfc2131>.
skipping to change at page 13, line 32 skipping to change at page 14, line 10
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2003, <http://www.rfc-editor.org/info/rfc3315>. 2003, <http://www.rfc-editor.org/info/rfc3315>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005, RFC 4033, DOI 10.17487/RFC4033, March 2005,
<http://www.rfc-editor.org/info/rfc4033>. <http://www.rfc-editor.org/info/rfc4033>.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
<http://www.rfc-editor.org/info/rfc5198>.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389, "Session Traversal Utilities for NAT (STUN)", RFC 5389,
DOI 10.17487/RFC5389, October 2008, DOI 10.17487/RFC5389, October 2008,
<http://www.rfc-editor.org/info/rfc5389>. <http://www.rfc-editor.org/info/rfc5389>.
[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using [RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766, Traversal Utilities for NAT (STUN)", RFC 5766,
DOI 10.17487/RFC5766, April 2010, DOI 10.17487/RFC5766, April 2010,
<http://www.rfc-editor.org/info/rfc5766>. <http://www.rfc-editor.org/info/rfc5766>.
skipping to change at page 14, line 39 skipping to change at page 15, line 11
Transport Layer Security (TLS) and Datagram Transport Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <http://www.rfc-editor.org/info/rfc7250>. June 2014, <http://www.rfc-editor.org/info/rfc7250>.
[RFC7635] Reddy, T., Patil, P., Ravindranath, R., and J. Uberti, [RFC7635] Reddy, T., Patil, P., Ravindranath, R., and J. Uberti,
"Session Traversal Utilities for NAT (STUN) Extension for "Session Traversal Utilities for NAT (STUN) Extension for
Third-Party Authorization", RFC 7635, Third-Party Authorization", RFC 7635,
DOI 10.17487/RFC7635, August 2015, DOI 10.17487/RFC7635, August 2015,
<http://www.rfc-editor.org/info/rfc7635>. <http://www.rfc-editor.org/info/rfc7635>.
11.2. Informative References 10.2. Informative References
[I-D.ietf-rtcweb-overview]
Alvestrand, H., "Overview: Real Time Protocols for
Browser-based Applications", draft-ietf-rtcweb-overview-16
(work in progress), November 2016.
[I-D.ietf-rtcweb-return]
Schwartz, B. and J. Uberti, "Recursively Encapsulated TURN
(RETURN) for Connectivity and Privacy in WebRTC", draft-
ietf-rtcweb-return-01 (work in progress), January 2016.
[I-D.ietf-tram-turn-mobility] [RETURN] Schwartz, B. and J. Uberti, "Recursively Encapsulated TURN
Reddy, T., Wing, D., Patil, P., and P. Martinsen, (RETURN) for Connectivity and Privacy in WebRTC", Work in
"Mobility with TURN", draft-ietf-tram-turn-mobility-09 Progress, draft-ietf-rtcweb-return-02, March 2017.
(work in progress), September 2016.
[RFC3188] Hakala, J., "Using National Bibliography Numbers as [RFC3188] Hakala, J., "Using National Bibliography Numbers as
Uniform Resource Names", RFC 3188, DOI 10.17487/RFC3188, Uniform Resource Names", RFC 3188, DOI 10.17487/RFC3188,
October 2001, <http://www.rfc-editor.org/info/rfc3188>. October 2001, <http://www.rfc-editor.org/info/rfc3188>.
[RFC5128] Srisuresh, P., Ford, B., and D. Kegel, "State of Peer-to- [RFC5128] Srisuresh, P., Ford, B., and D. Kegel, "State of Peer-to-
Peer (P2P) Communication across Network Address Peer (P2P) Communication across Network Address
Translators (NATs)", RFC 5128, DOI 10.17487/RFC5128, March Translators (NATs)", RFC 5128, DOI 10.17487/RFC5128, March
2008, <http://www.rfc-editor.org/info/rfc5128>. 2008, <http://www.rfc-editor.org/info/rfc5128>.
skipping to change at page 15, line 34 skipping to change at page 15, line 41
2011, <http://www.rfc-editor.org/info/rfc6125>. 2011, <http://www.rfc-editor.org/info/rfc6125>.
[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection [RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435, Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <http://www.rfc-editor.org/info/rfc7435>. December 2014, <http://www.rfc-editor.org/info/rfc7435>.
[RFC7469] Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning [RFC7469] Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
2015, <http://www.rfc-editor.org/info/rfc7469>. 2015, <http://www.rfc-editor.org/info/rfc7469>.
[RFC8016] Reddy, T., Wing, D., Patil, P., and P. Martinsen,
"Mobility with Traversal Using Relays around NAT (TURN)",
RFC 8016, DOI 10.17487/RFC8016, November 2016,
<http://www.rfc-editor.org/info/rfc8016>.
[WebRTC-Overview]
Alvestrand, H., "Overview: Real Time Protocols for
Browser-based Applications", Work in Progress,
draft-ietf-rtcweb-overview-18, March 2017.
Acknowledgements
The authors would like to thank Simon Perrault, Paul Kyzivat, Troy
Shields, Eduardo Gueiros, Ted Hardie, Bernard Aboba, Karl Stahl,
Brian Weis, Ralph Dromes, Ben Campbell, Suresh Krishnan, and Brandon
Williams for their review and valuable comments. Thanks to Adam
Roach for his detailed review and suggesting DNS Service Discovery as
an additional discovery mechanism.
Authors' Addresses Authors' Addresses
Prashanth Patil Prashanth Patil
Cisco Systems, Inc. Cisco Systems, Inc.
Email: praspati@cisco.com Email: praspati@cisco.com
Tirumaleswar Reddy Tirumaleswar Reddy
Cisco Systems, Inc. Cisco Systems, Inc.
Cessna Business Park, Varthur Hobli Cessna Business Park, Varthur Hobli
skipping to change at page 16, line 4 skipping to change at page 16, line 29
Email: praspati@cisco.com Email: praspati@cisco.com
Tirumaleswar Reddy Tirumaleswar Reddy
Cisco Systems, Inc. Cisco Systems, Inc.
Cessna Business Park, Varthur Hobli Cessna Business Park, Varthur Hobli
Sarjapur Marathalli Outer Ring Road Sarjapur Marathalli Outer Ring Road
Bangalore, Karnataka 560103 Bangalore, Karnataka 560103
India India
Email: tireddy@cisco.com Email: tireddy@cisco.com
Dan Wing Dan Wing
USA United States America
Email: dwing-ietf@fuggles.com Email: dwing-ietf@fuggles.com
 End of changes. 79 change blocks. 
171 lines changed or deleted 158 lines changed or added

This html diff was produced by rfcdiff 1.45. The latest version is available from http://tools.ietf.org/tools/rfcdiff/