IPv6 Working Group S. Krishnan Internet-Draft Ericsson Intended status: Standards Track j h. woodyatt Expires: August 28, 2008 Apple E. Kline Google J. Hoagland Symantec February 25, 2008 An uniform format for IPv6 extension headers draft-krishnan-ipv6-exthdr-01 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 August 28, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). 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 Krishnan, et al. Expires August 28, 2008 [Page 1] Internet-Draft IPv6 extension headers February 2008 currently defined. This document defines a format for defining new IPv6 extension headers. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . . 3 2. Proposed format . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 5 4. Future work . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 7. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 8 Krishnan, et al. Expires August 28, 2008 [Page 2] Internet-Draft IPv6 extension headers February 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 standard and hence it is not possible to skip past the unknown header. This document intends to define a standard format for 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 August 28, 2008 [Page 3] Internet-Draft IPv6 extension headers February 2008 2. Proposed format This document proposes that all IPv6 extension headers be encoded in a consistent TLV format so that it is possible for nodes to skip over unknown extension headers and continue to further process the header chain. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | . . . Header Specific Data . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Next Header 8-bit selector. Identifies the type of header immediately following the 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. Header Specific Variable length. Fields specific to the Data extension header Figure 1: Extension header layout Krishnan, et al. Expires August 28, 2008 [Page 4] Internet-Draft IPv6 extension headers February 2008 3. Backward Compatibility The scheme proposed in this document is backward compatible with all the currently defined IPv6 extension headers except the Fragment Header. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Reserved | Fragment Offset |Res|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Fragment header layout This document proposes that the format of the extension header be changed to the following +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Fragment Offset |Res|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Hdr Ext Len 8-bit unsigned integer. Length of the Extension header in 8-octet units, not including the first 8 octets. Figure 3: New fragment header layout Since the reserved field is currently required to be set to 0 and the length of the fragment header is 8 octets, the length field will remain as 0. Because of this there will be no backward compatibility issues with existing implementations 4. 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 any order they appear o Extension headers can be repeated in same packet o Unknown extension headers cannot be differentiated from unknown upper layer protocols Krishnan, et al. Expires August 28, 2008 [Page 5] Internet-Draft IPv6 extension headers February 2008 5. IANA Considerations This document requires no IANA action. 6. Security Considerations This document proposes a standard format for the IPv6 extension headers so that intermediate nodes,such as firewalls that do not understand the contents of these headers can look past them. 7. 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 August 28, 2008 [Page 6] Internet-Draft IPv6 extension headers February 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 August 28, 2008 [Page 7] Internet-Draft IPv6 extension headers February 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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Krishnan, et al. Expires August 28, 2008 [Page 8]