6man Working Group S. Krishnan Internet-Draft J. Halpern Intended status: Standards Track Ericsson Expires: April 21, 2011 October 18, 2010 Reserving bits in the IPv6 header for future use draft-krishnan-6man-header-reserved-bits-00 Abstract The IPv6 header does not contain any reserved bits for future expansion. This document sets aside 4 bits from the flow label field for future expansion. Status of this Memo This Internet-Draft is submitted in full conformance with the 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 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." This Internet-Draft will expire on April 21, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Krishnan & Halpern Expires April 21, 2011 [Page 1] Internet-Draft IPv6 Reserved Bits October 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . . 3 3. New IPv6 header format . . . . . . . . . . . . . . . . . . . . 3 4. Future use of the reserved bits . . . . . . . . . . . . . . . . 4 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 8. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 Krishnan & Halpern Expires April 21, 2011 [Page 2] Internet-Draft IPv6 Reserved Bits October 2010 1. Introduction The IPv6 header does not contain any reserved bits and all bits in the header are currently accounted for. This means that it is not possible to develop any future extension mechanisms that require bits in the IPv6 header. Mechanisms such as ECN were possible in IPv4 because there were bits available in the IPv4 header. e.g. Re-ECN is a proof of concept mechanism for ConEx that uses an unused bit (Bit 48) in the IPv4 header. It cannot be implemented analogously in the IPv6 header. This document proposes reducing the size of the flow label field from 20 bits to 16 bits and setting aside 4 bits for future use. 2. 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]. 3. New IPv6 header format This document updates Section 3 of [RFC2460] to reduce the length of the flow label field from 20 bits to 16 bits, and in the process creating a 4 bit reserved field. All other fields in the IPv6 header remain unchanged from [RFC2460]. Krishnan & Halpern Expires April 21, 2011 [Page 3] Internet-Draft IPv6 Reserved Bits October 2010 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Traffic Class | Resvd | Flow Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Resvd 4-bit reserved field. Flow Label 16-bit flow label. All other fields are same as those defined by [RFC2460] Figure 1: Modified IPv6 header format Senders MUST set the bits in the reserved field to zero and receivers MUST ignore them. 4. Future use of the reserved bits New mechanisms that require allocation of one or more of the reserved bits MUST require Standards Action as specified in [RFC5226]. 5. Acknowledgements The authors would like to Pekka Savola, Christian Huitema, and Ingemar Johansson for the discussions that led to this document. Krishnan & Halpern Expires April 21, 2011 [Page 4] Internet-Draft IPv6 Reserved Bits October 2010 6. Security Considerations This document does not bring up any new security issues. 7. IANA Considerations This document does not require any IANA action. 8. 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. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Authors' Addresses Suresh Krishnan Ericsson 8400 Blvd Decarie Town of Mount Royal, Quebec Canada Email: suresh.krishnan@ericsson.com Joel Halpern Ericsson Email: joel.halpern@ericsson.com Krishnan & Halpern Expires April 21, 2011 [Page 5]