Network Working Group M. Andrews Internet-Draft ISC Expires: February 2, 2014 Aug 2013 IPv6 Stateless Fragmentation Identification Options draft-andrews-6man-fragopt-00.txt Abstract Fragmented IPv6 packets are often dropped because there is no way to identify whether a fragment matches a otherwise permitted packet as the L4 header information is not available on all the fragments. The document defines hop-by-hop options that can be used to supply the missing information in non initial fragments. 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 February 2, 2014. Copyright Notice Copyright (c) 2013 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. Andrews Expires February 2, 2014 [Page 1] Internet-Draft hop by hop frag opts Aug 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. TCP and UDP Fragements . . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 3 4. Normative References . . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 4 Andrews Expires February 2, 2014 [Page 2] Internet-Draft hop by hop frag opts Aug 2013 1. Introduction Fragmented IPv6 packets are often dropped because there is no way to identify whether a fragment matches a otherwise permitted packet as the L4 header information is not available on all the fragments. The document defines hop-by-hop options that can be used to supply the missing information in non initial fragments. The informtion required differs depending upon the L4 packet. For TCP and UDP the source and destination ports are needed. For ICMP the type of ICMP packet is needed. These options are expected to be used by middle boxes (firewalls and loadbalancers) and end nodes. 2. TCP and UDP Fragements For TCP and UDP a skippable hop-by-hop option [RFC2460] (for backwards compatibilty) containing the source and destination ports from the TCP and UDP headers is needed. To permit the use of NATs, however undesired, the option contents are marked changable enroute. The option code has nmemonic PORTS and value (TBD) and is added to all fragments of UDP and TCP packets when they are fragmented. By adding the option to all fragments you reduce the amount of fragmentation reassembly failures that would result if you only added the option to non-initial fragments and were dropping non-initial fragments without this option. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0|1| (TBD) | 4 | source port | +---------------+---------------+---------------+---------------+ | destination port | +-------------------------------+ 3. Security Considerations The use of these options will expose nodes to more fragmention based attacks and potentually more traffic which will ultimately be dropped if a attacker can guess which option values will be permitted. With the exception of the fragmentation based attacks, permitting fragments with these options is no worse that permitting multiple unfragmented packets based in the same parameters. Andrews Expires February 2, 2014 [Page 3] Internet-Draft hop by hop frag opts Aug 2013 4. Normative References [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. Author's Address M. Andrews Internet Systems Consortium 950 Charter Street Redwood City, CA 94063 US Email: marka@isc.org Andrews Expires February 2, 2014 [Page 4]