6MAN J. Hui Internet-Draft Arch Rock Corporation Intended status: Standards Track JP. Vasseur Expires: September 30, 2011 Cisco Systems, Inc March 29, 2011 RPL Option for Carrying RPL Information in Data-Plane Datagrams draft-ietf-6man-rpl-option-03 Abstract The RPL protocol requires data-plane datagrams to carry RPL routing information that is processed by RPL routers when forwarding those datagrams. This document describes the RPL option for use within a RPL domain. 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 September 30, 2011. Copyright Notice Copyright (c) 2011 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. Hui & Vasseur Expires September 30, 2011 [Page 1] Internet-Draft RPL Option March 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Format of the RPL Option . . . . . . . . . . . . . . . . . . . 5 4. RPL Router Behavior . . . . . . . . . . . . . . . . . . . . . 6 5. RPL Border Router Behavior . . . . . . . . . . . . . . . . . . 7 6. Usage of the RPL Option . . . . . . . . . . . . . . . . . . . 8 7. Protocol Constants . . . . . . . . . . . . . . . . . . . . . . 9 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 10. Security Considerations . . . . . . . . . . . . . . . . . . . 12 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11.1. Normative References . . . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Hui & Vasseur Expires September 30, 2011 [Page 2] Internet-Draft RPL Option March 2011 1. Introduction RPL is a distance vector IPv6 routing protocol designed for low power and lossy networks [I-D.ietf-roll-rpl]. Such networks are typically constrained in energy and/or channel capacity. To conserve precious resources, a routing protocol must generate control traffic sparingly. However, this is at odds with the need to quickly propagate any new routing information to resolve routing inconsistencies quickly. To help minimize resource consumption, RPL uses a slow proactive process to construct and maintain a routing topology but a reactive and dynamic process to resolving routing inconsistencies. In the steady state, RPL maintains the routing topology using a low-rate beaconing process. However, when RPL detects inconsistencies that may prevent proper datagram delivery, RPL temporarily increases the beacon rate to quickly resolve those inconsistencies. This dynamic rate control operation is governed by the use of dynamic timers also referred to as "Trickle" timers and defined in [I-D.ietf-roll-trickle]. In contrast to other routing protocols (e.g OSPF [RFC2328]), RPL detects routing inconsistencies using data-path verification, by including routing information within the datagram itself. In doing so, repair mechanisms operate only as needed, allowing the control and data planes to operate on similar time scales. The main motivation for data path verification in Low power and Lossy Networks (LLNs) is that control plane traffic should be carefully bounded with respect to the data traffic. Intuitively, there is no need to solve routing issues (which may be temporary) in the absence of data traffic. The RPL protocol constructs a Directed Acyclic Graph (DAG) that attempts to minimize path costs to the DAG root according to a set of metric and objective functions. There are circumstances where loops may occur, and RPL is designed to use a data-path loop detection method. This is one of the known requirements of RPL and other data- path usage might be defined in the future. To that end, this document proposes a new IPv6 option, called the RPL Option, to be carried within the IPv6 Hop-by-Hop header. The RPL Option is only for use within a RPL domain. 1.1. Requirements Language 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 RFC 2119 [RFC2119]. Hui & Vasseur Expires September 30, 2011 [Page 3] Internet-Draft RPL Option March 2011 2. Overview Datagrams being forwarded within a RPL domain MUST include a RPL Option. For datagrams sourced within a RPL domain, the RPL Option MAY be included in the datagram itself. For datagrams sourced outside a RPL domain, IPv6-in-IPv6 tunneling, as specified in [RFC2473] SHOULD be used to include a RPL Option. When tunneling, the router MUST prepend a new IPv6 header and IPv6 Hop-by-Hop Options header containing the RPL Option to the existing datagram. Use of tunneling ensures that the datagram is delivered unmodified and that ICMP errors return to the RPL Option source rather than the source of the original datagram. To help avoid IP-layer fragmentation, the RPL Option has a maximum size of RPL_OPTION_MAX_SIZE octets and links within a RPL domain SHOULD have a MTU of at least 1280 + 44 (outer IP header, Hop-by-Hop Option header, Option header) + RPL_OPTION_MAX_SIZE + (additional extension headers or options needed within RPL domain). Hui & Vasseur Expires September 30, 2011 [Page 4] Internet-Draft RPL Option March 2011 3. Format of the RPL Option The RPL Option is carried in an IPv6 Hop-by-Hop Options header, immediately following the IPv6 header. This option has an alignment requirement of 2n. The option has the following format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Opt Data Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |O|R|F|0|0|0|0|0| RPLInstanceID | SenderRank | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (sub-TLVs) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: RPL Option Option Type: TBD by IANA. Opt Data Len: 8-bit field indicating the length of the option, in octets, excluding the Option Type and Opt Data Len fields. Down 'O': 1-bit flag as defined in Section 11 of [I-D.ietf-roll-rpl]. Rank-Error 'R': 1-bit flag as defined in Section 11 of [I-D.ietf-roll-rpl]. Forwarding-Error 'F': 1-bit flag as defined in Section 11 of [I-D.ietf-roll-rpl]. RPLInstanceID: 8-bit field as defined in Section 11 of [I-D.ietf-roll-rpl]. SenderRank: 16-bit field as defined in Section 11 of [I-D.ietf-roll-rpl]. Values within the RPL Option are expected to change en-route. Nodes that do not understand the RPL Option MUST discard the packet. Thus, according to [RFC2460] the two high order bits of the Option Type must be equal set to '01' and the third bit is equal to '1'. The RPL Option Data Length is variable. The action taken by using the RPL Option and the potential set of sub-TLVs carried within the RPL Option MUST be specified by the RFC of the protocol that use that option. No TLVs are defined in this document. Hui & Vasseur Expires September 30, 2011 [Page 5] Internet-Draft RPL Option March 2011 4. RPL Router Behavior RPL controls when and what information is to be placed in a packet. If RPL requires a router to include a RPL Option where one does not already exist, routers SHOULD use IPv6-in-IPv6 tunneling, as specified in [RFC2473] to include a RPL Option in datagrams that are sourced by other nodes. Using IPv6-in-IPv6 tunneling ensures that the original datagram is delivered unmodified. Performing IP-in-IP encapsulation may grow the datagram to a size larger than the IPv6 min MTU of 1280 octets. To help avoid IP-layer fragmentation caused by IP-in-IP encapsulation, links within a RPL domain SHOULD be configured with a MTU of at least 1280 + 44 (outer IP header, Hop-by-Hop Option header, Option header) + RPL_OPTION_MAX_SIZE + (additional extension headers or options needed within RPL domain). In very specific cases, IPv6-in-IPv6 tunneling may be undesirable due to the added cost and complexity required to process and carry a datagram with two IPv6 headers. [I-D.hui-6man-rpl-headers] describes how to avoid using IPv6-in-IPv6 tunneling in such specific cases and the risks involved. Hui & Vasseur Expires September 30, 2011 [Page 6] Internet-Draft RPL Option March 2011 5. RPL Border Router Behavior RPL Border Routers (referred to as LBRs in [I-D.ietf-roll-terminology]) are responsible for ensuring that a RPL Option is only used within a RPL domain. For datagrams entering the RPL domain, RPL Border Routers MUST drop received datagrams that contain a RPL Option in the IPv6 Extension headers. For datagrams exiting the RPL domain, RPL Border Routers MUST remove the RPL Option from the datagram. If the RPL Option was included using tunneled mode and the RPL Border Router serves as the tunnel end-point, removing the outer IPv6 header serves to remove the RPL Option as well. Otherwise, the RPL Border Router assumes that the RPL Option was included using transport mode and MUST remove the RPL Option from the IPv6 Hop-by-Hop Option header. Hui & Vasseur Expires September 30, 2011 [Page 7] Internet-Draft RPL Option March 2011 6. Usage of the RPL Option The RPL Option is only for use within a RPL domain. RPL routers MUST process and include the RPL Option when forwarding datagrams to other nodes within the RPL domain. Routers on the edge of a RPL domain MUST remove the RPL Option when forwarding datagrams to nodes outside the RPL domain. Hui & Vasseur Expires September 30, 2011 [Page 8] Internet-Draft RPL Option March 2011 7. Protocol Constants RPL_OPTION_MAX_SIZE 128 Hui & Vasseur Expires September 30, 2011 [Page 9] Internet-Draft RPL Option March 2011 8. Acknowledgements The authors thank Richard Kelsey, Suresh Krishnan, Vishwas Manral, Erik Nordmark, Pascal Thubert, and Tim Winter, for their comments and suggestions that helped shape this document. Hui & Vasseur Expires September 30, 2011 [Page 10] Internet-Draft RPL Option March 2011 9. IANA Considerations IANA is requested to reserve a new value in the Destination Options and Hop-by-Hop Options registry. The proposed value to be confirmed by IANA is: Hex Value Binary Value act chg rest Description Reference --------- --- --- ------- ----------------- ---------- TBD 01 1 TBD RPL Option [RFCthis] As specified in [RFC2460], the first two bits indicate that the IPv6 node MUST discard the packet if it doesn't recognize the option type, and the third bit indicates that the Option Data may change en-route. The remaining bits serve as the option type and are TBD by IANA. IANA is requested to create a registry called RPL-option-TLV, for the TLVs carried in the RPL Option header. New codes may be allocated only by IETF Review [RFC5226]. The type field is an 8-bit field whose value be between 0 and 255, inclusive. Hui & Vasseur Expires September 30, 2011 [Page 11] Internet-Draft RPL Option March 2011 10. Security Considerations This option may be used to mount several potential attacks since routers may be flooded by bogus datagram containing the RPL option. It is thus RECOMMENDED for routers to implement a rate limiter for datagrams using the RPL Option. Hui & Vasseur Expires September 30, 2011 [Page 12] Internet-Draft RPL Option March 2011 11. References 11.1. Normative References [I-D.ietf-roll-rpl] Winter, T., Thubert, P., Brandt, A., Clausen, T., Hui, J., Kelsey, R., Levis, P., Pister, K., Struik, R., and J. Vasseur, "RPL: IPv6 Routing Protocol for Low power and Lossy Networks", draft-ietf-roll-rpl-19 (work in progress), March 2011. [I-D.ietf-roll-trickle] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, "The Trickle Algorithm", draft-ietf-roll-trickle-08 (work in progress), January 2011. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, December 1998. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. 11.2. Informative References [I-D.hui-6man-rpl-headers] Hui, J., Thubert, P., and J. Vasseur, "Using RPL Headers Without IP-in-IP", draft-hui-6man-rpl-headers-00 (work in progress), July 2010. [I-D.ietf-roll-terminology] Vasseur, J., "Terminology in Low power And Lossy Networks", draft-ietf-roll-terminology-05 (work in progress), March 2011. Hui & Vasseur Expires September 30, 2011 [Page 13] Internet-Draft RPL Option March 2011 Authors' Addresses Jonathan W. Hui Arch Rock Corporation 501 2nd St. Ste. 410 San Francisco, California 94107 USA Phone: +415 692 0828 Email: jhui@archrock.com JP Vasseur Cisco Systems, Inc 11, Rue Camille Desmoulins Issy Les Moulineaux, 92782 France Email: jpv@cisco.com Hui & Vasseur Expires September 30, 2011 [Page 14]