6man Working Group S. Krishnan Internet-Draft Ericsson Intended status: Standards Track j h. woodyatt Expires: April 6, 2009 Apple E. Kline Google J. Hoagland Symantec October 3, 2008 An uniform format for IPv6 extension headers draft-krishnan-ipv6-exthdr-05 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 6, 2009. Abstract In IPv6, optional internet-layer information is encoded in separate headers that may be placed between the IPv6 header and the transport layer header. There are a small number of such extension headers currently defined. This document defines a format for defining a new family of IPv6 extension headers. Krishnan, et al. Expires April 6, 2009 [Page 1] Internet-Draft IPv6 extension headers October 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . . 3 2. Proposed format . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 6 4. Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Future work . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 9. Normative References . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 9 Krishnan, et al. Expires April 6, 2009 [Page 2] Internet-Draft IPv6 extension headers October 2008 1. Introduction The base IPv6 standard [RFC2460] defines extension headers as an expansion mechanism to carry optional internet layer information. Extension headers, with the exception of the hop-by-hop options header, are not usually processed on intermediate nodes. However, some intermediate nodes such as firewalls, may need to look at the transport layer header fields in order to make a decision to allow or deny the packet. If new extension headers are defined and the intermediate node is not aware of them, the intermediate node cannot proceed further in the header chain since it does not know where the unknown header ends and the next header begins. The main issue is that the extension header format is not standardized and hence it is not possible to skip past the unknown header. This document defines a standard format for a new family of IPv6 extension headers. 1.1. Conventions used in this document 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]. Krishnan, et al. Expires April 6, 2009 [Page 3] Internet-Draft IPv6 extension headers October 2008 2. Proposed format This document proposes a new family of IPv6 extension headers that will be encoded in a consistent format so that it is possible for intermediate nodes to skip over unknown extension headers and continue to further process the header chain if they so desire. The intention of the base IPv6 Specification [RFC2460] that destination hosts not be permitted to skip unknown extension headers continues to apply. One key advantage of using such a generic IPv6 extension header is that it allows nodes to distinguish between unknown extension headers and unknown upper layer protocols, which was not possible earlier. Another one is that this generic extension header conserves values in the IPv4 protocol numbers registry. This documents requires the allocation of a single IP protocol number for the Generic IPv6 extension header (GIEH), say TBA1. Specifications of new extension headers SHOULD use this generic extension header format whenever feasible. The generic extension header will be identified by the value TBA1 occuring in the Next Header field of the preceding extension header. The second octet contains the length of the extension header. The third octet of the GIEH contains a specific extension header type (that identifies the actual extension header). All other data in the GIEH is type- specific. Krishnan, et al. Expires April 6, 2009 [Page 4] Internet-Draft IPv6 extension headers October 2008 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Specific Type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | . . . Header Specific Data . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Next Header 8-bit selector. Identifies the type of header immediately following this Extension header. Uses the same values as the IPv4 Protocol field. Hdr Ext Len 8-bit unsigned integer. Length of the Extension header in 8-octet units, not including the first 8 octets. Specific Type 8-bit unsigned integer. The actual IPv6 extension header type. This will be allocated from a new IANA registry. Header Specific Variable length. Fields specific to the Data extension header. This data MUST be padded as required in order to ensure that the complete GIEH is a multiple of 8 octets long. Figure 1: Generic IPv6 Extension Header (GIEH) layout Krishnan, et al. Expires April 6, 2009 [Page 5] Internet-Draft IPv6 extension headers October 2008 3. Backward Compatibility The scheme proposed in this document is not backward compatible with all the currently defined IPv6 extension headers. It only applies to newly defined extension headers. Specifically, the following extension headers predate this document and do not follow the format proposed in this document. o IPv6 Hop-by-Hop Options Header o IPv6 Routing Header o IPv6 Fragment Header o IPv6 Destination Options Header 4. Exceptions The the Generic IPv6 extension header is generic enough that it is suitable to use for most applications. However, it is possible that the GIEH does not satisfy the requirements in all cases where new extension headers are required. Hence, the existence of this generic header does not necessarily preclude the definition of new independent IPv6 extension headers. 5. Future work This document proposes one step in easing the inspection of extension headers by middleboxes. There is further work required in this area. Some issues that are left unresolved beyond this document include o There can be an arbitrary number of extension headers o Extension headers must be processed in the order they appear. o Extension headers may alter the processing of the payload itself, and hence the packet may not be processed properly without knowledge of said header 6. IANA Considerations This document requests a single allocation from the IANA for this generic IPv6 extension header type (TBA1) from the Assigned Internet Protocol Numbers registry located at http://www.iana.org/assignments/protocol-numbers. This document also requests the creation of a new registry for GIEH sub-types. The allocation policy for these subtypes is Standards Action. Krishnan, et al. Expires April 6, 2009 [Page 6] Internet-Draft IPv6 extension headers October 2008 7. Security Considerations This document proposes a standard format for the IPv6 extension headers so that intermediate nodes that do not understand the contents of these headers can look past them. Intermediate nodes, such as firewalls, skipping over unknown headers might end up allowing the setup of a covert channel from the outside of the firewall to the inside using the data field(s) of the unknown extension headers. 8. Acknowledgements The authors would like to thank Albert Manfredi, Bob Hinden, Brian Carpenter, Erik Nordmark, Hemant Singh, Lars Westberg, Markku Savela, Tatuya Jinmei, Thomas Narten, Vishwas Manral and Alfred Hoenes for their reviews and suggestions that made this document better. 9. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. Authors' Addresses Suresh Krishnan Ericsson 8400 Decarie Blvd. Town of Mount Royal, QC Canada Phone: +1 514 345 7900 x42871 Email: suresh.krishnan@ericsson.com james woodyatt Apple Inc. 1 Infinite Loop Cupertino, CA 95014 US Email: jhw@apple.com Krishnan, et al. Expires April 6, 2009 [Page 7] Internet-Draft IPv6 extension headers October 2008 Erik Kline Google 604 Arizona Avenue Santa Monica, CA 90401 US Phone: +1 310 460 4080 Email: ek@google.com James Hoagland Symantec Corporation 350 Ellis St. Mountain View, CA 94043 US Email: Jim_Hoagland@symantec.com URI: http://symantec.com/ Krishnan, et al. Expires April 6, 2009 [Page 8] Internet-Draft IPv6 extension headers October 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Krishnan, et al. Expires April 6, 2009 [Page 9]