MIDCOM G. Camarillo Internet-Draft O. Novo Expires: April 15, 2006 Ericsson October 12, 2005 Traversal Using Relay NAT (TURN) Extension for IPv4/IPv6 transition draft-camarillo-midcom-turn-ipv6-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 15, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document defines the Traversal Using Relay NAT (TURN) REQUESTED- ADDRESS-TYPE attribute, which allows a client to explicitly request the address type the TURN server will allocate (e.g., an IPv4-only node may request the TURN server to allocate an IPv6 address). This document also registers the IPv6 address type. Camarillo & Novo Expires April 15, 2006 [Page 1] Internet-Draft TURN Extension for IPv4/IPv6 transition October 2005 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Overview of Operation . . . . . . . . . . . . . . . . . . . . . 3 4. Client Behavior . . . . . . . . . . . . . . . . . . . . . . . . 3 4.1. Allocating a Binding . . . . . . . . . . . . . . . . . . . 4 4.2. Refreshing a Binding . . . . . . . . . . . . . . . . . . . 5 5. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. Allocate Request . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . . . 9 Camarillo & Novo Expires April 15, 2006 [Page 2] Internet-Draft TURN Extension for IPv4/IPv6 transition October 2005 1. Introduction Traversal Using Relay NAT (TURN) is a protocol that allows for an element behind a NAT or firewall to receive incoming data over TCP or UDP connections. It is most useful for elements behind symmetric NATs or firewalls that wish to be on the receiving end of a connection to a single peer. This document defines the REQUESTED-ADDRESS-TYPE attribute, which is an extension to TURN that allows a client to explicitly request the address type the TURN server will allocate (e.g., an IPv4-only node may request the TURN server to allocate an IPv6 address). This document also registers the IPv6 address type, which is initially intended to be used in MAPPED-ADDRESS and in REQUESTED- ADDRESS-TYPE attributes. 2. Terminology In this document, the key words MUST, MUST NOT, REQUIRED, SHALL, HALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL are o be interpreted as described in RFC RFC-2119 [1] and indicate requirement levels for compliant TURN implementations. 3. Overview of Operation When a user wishes a TURN server to allocate an address of a specific type, it sends an Allocate Request to the TURN server with a REQUESTED-ADDRESS-TYPE attribute. TURN can run over UDP and TCP, as it allows for a client to request address/port pairs for receiving both UDP and TCP. Assuming the request is authenticated and has not been tampered with, the TURN server allocates a transport address of the type indicated in the REQUESTED-ADDRESS-TYPE attribute. This address is called the allocated transport address. The TURN server returns the allocated address in the response to the Allocate Request. This response contains a MAPPED-ADDRESS attribute indicating the mapped IP address and port that the server assigned to the client. 4. Client Behavior The client behavior specified here affects the transport processing Camarillo & Novo Expires April 15, 2006 [Page 3] Internet-Draft TURN Extension for IPv4/IPv6 transition October 2005 defined in Section 8 of TURN [2]. 4.1. Allocating a Binding A client that wishes to obtain a transport address of a specific address type includes the REQUESTED-ADDRESS-TYPE attribute in the Allocate Request that sends to the TURN server. The mechanisms to formulate an Allocate Request are described in Section 8.3 of [2]. The REQUESTED-ADDRESS-TYPE attribute is used by clients to request the allocation of a specific address type from a server. The following is the format of the REQUESTED-ADDRESS-TYPE attribute. Note that attributes in TURN are TLV (Type-Length-Value) encoded, with a 16 bit type, a 16 bit length, and a variable-length value. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Family | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: the type of the REQUESTED-ADDRESS-TYPE mandatory-to-understand attribute is 0x0016. As it is explained in [3], a server cannot process a message with a mandatory-to-understand attributes unless it understands the mandatory attribute. Length: this 16-bit field contains the length of the attribute in bytes. The length of this attribute is 4 bytes. Family: there are two values defined for this field: 0x01 for IPv4 addresses and 0x02 for IPv6 addresses. Reserved: at this point, the 16 bits in the reserved field SHOULD be set to zero by the client and MUST be ignored by the server. Table 1 indicates in which TURN messages can be present the REQUEST- ADDRESS-TYPE attribute. An O indicates that inclusion of the attribute in the message is optional and N/A means that the attribute is not applicable to that message type. Binding Shared Shared Shared Binding Binding Error Secret Secret Secret Att. Req. Resp. Resp. Req. Resp. Error Resp. __________________________________________________________________ Camarillo & Novo Expires April 15, 2006 [Page 4] Internet-Draft TURN Extension for IPv4/IPv6 transition October 2005 REQUESTED-ADDRESS-TYPE O N/A N/A N/A N/A N/A Table 1: Summary of the REQUESTED-ADDRESS-TYPE Attribute 4.2. Refreshing a Binding To perform a binding refresh, the client generates an Allocate Request as described in the previous section. The client includes the same REQUESTED-ADDRESS-TYPE attribute as it included in its initial Allocate Request. If the Allocate Response contains the same transport address as previously obtained, the binding has been refreshed. If, however, the response was an Allocate Error Response with an ERROR-CODE indicating a 430 response, it means that the binding has expired at the server. Other response codes do not imply that the binding has been expired, just that the refresh has failed. 5. Server Behavior The server behavior specified here affects the transport processing defined in Section 7.2 of TURN [2]. 5.1. Allocate Request Assuming the request is authenticated and has not been tampered with, the TURN server processes the request. If the server does not understand the REQUESTED-ADDRESS-TYPE attribute, it MUST generate an Allocate Error Response, and it MUST include an ERROR-CODE attribute with response code 420 (Unknown Attribute). This response MUST contain an UNKNOWN-ATTRIBUTE attribute listing the unknown REQUESTED- ADDRESS-TYPE attribute. If the server can successfully process the request, it allocates a transport address to the TURN client, called the allocated transport address, and returns it in the response to the Allocate Request. As is explained in [2], the Allocate Response contains the same transaction ID contained in the Allocate Request. The server adds a MAPPED-ADDRESS attribute to the Allocate Response and sets it to the allocated transport address. The MAPPED-ADDRESS attribute indicates the mapped IP address and port. It consists of an eight bit address family, and a sixteen bit port, followed by a fixed length value representing the IP address. Camarillo & Novo Expires April 15, 2006 [Page 5] Internet-Draft TURN Extension for IPv4/IPv6 transition October 2005 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |x x x x x x x x| Family | Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ STUN [3] defines the 0x01 family type address value for the MAPPED- ADDRESS attribute. The first 8 bits of the MAPPED-ADDRESS are ignored, for the purposes of aligning parameters on natural boundaries. The value of the Address field is 4 bytes (32 bits) long for the IPv4 family type address. This document defines the IPv6 family type address with the value 0x02. The value of the Address field is 32 bytes (128 bits) long for the IPv6 address. The fact that the length of this type of address is 32 bytes guarantees the alignment of the attribute on word boundaries. 6. IANA Considerations This document defines the REQUESTED-ADDRESS-TYPE attribute, which the IANA has added to the TURN attribute registry defined in TURN [2]. Editor's note: the TURN spec does not create this registry yet. It needs to create it. This document also defines the address family tag "0x002" which IANA has added to the registry defined in STUN [3]. Editor's note: the specs of STUN and TURN do not create any registry for this yet. 7. Acknowledgements 8. References 8.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Camarillo & Novo Expires April 15, 2006 [Page 6] Internet-Draft TURN Extension for IPv4/IPv6 transition October 2005 8.2. Informative References [2] Rosenberg, J., "Traversal Using Relay NAT (TURN)", draft-rosenberg-midcom-turn-08 (work in progress), September 2005. [3] Rosenberg, J., "Simple Traversal of UDP Through Network Address Translators (NAT) (STUN)", draft-ietf-behave-rfc3489bis-02 (work in progress), July 2005. Camarillo & Novo Expires April 15, 2006 [Page 7] Internet-Draft TURN Extension for IPv4/IPv6 transition October 2005 Authors' Addresses Gonzalo Camarillo Ericsson Hirsalantie 11 Jorvas 02420 Finland Email: Gonzalo.Camarillo@ericsson.com Oscar Novo Ericsson Hirsalantie 11 Jorvas 02420 Finland Email: Oscar.Novo@ericsson.com Camarillo & Novo Expires April 15, 2006 [Page 8] Internet-Draft TURN Extension for IPv4/IPv6 transition October 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Camarillo & Novo Expires April 15, 2006 [Page 9]