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author | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
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committer | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
commit | 4bfd864f10b68b71482b35c818559068ef8d5797 (patch) | |
tree | e3989f47a7994642eb325063d46e8f08ffa681dc /doc/rfc/rfc6553.txt | |
parent | ea76e11061bda059ae9f9ad130a9895cc85607db (diff) |
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diff --git a/doc/rfc/rfc6553.txt b/doc/rfc/rfc6553.txt new file mode 100644 index 0000000..fb87316 --- /dev/null +++ b/doc/rfc/rfc6553.txt @@ -0,0 +1,507 @@ + + + + + + +Internet Engineering Task Force (IETF) J. Hui +Request for Comments: 6553 JP. Vasseur +Category: Standards Track Cisco Systems +ISSN: 2070-1721 March 2012 + + + The Routing Protocol for Low-Power and Lossy Networks (RPL) Option + for Carrying RPL Information in Data-Plane Datagrams + +Abstract + + The Routing Protocol for Low-Power and Lossy Networks (RPL) includes + routing information in data-plane datagrams to quickly identify + inconsistencies in the routing topology. This document describes the + RPL Option for use among RPL routers to include such routing + information. + +Status of This Memo + + This is an Internet Standards Track document. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Further information on + Internet Standards is available in Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc6553. + +Copyright Notice + + Copyright (c) 2012 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 Standards Track [Page 1] + +RFC 6553 RPL Option March 2012 + + +Table of Contents + + 1. Introduction ....................................................2 + 1.1. Requirements Language ......................................3 + 2. Overview ........................................................3 + 3. Format of the RPL Option ........................................3 + 4. RPL Router Behavior .............................................5 + 5. Security Considerations .........................................6 + 5.1. DAG Inconsistency Attacks ..................................6 + 5.2. Destination Advertisement Object (DAO) + Inconsistency Attacks ......................................7 + 6. IANA Considerations .............................................7 + 7. Acknowledgements ................................................8 + 8. References ......................................................8 + 8.1. Normative References .......................................8 + 8.2. Informative References .....................................8 + +1. Introduction + + RPL is a distance vector IPv6 routing protocol designed for Low-Power + and Lossy Networks (LLNs) [RFC6550]. 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 [RFC6206]. 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 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. + + + + + + +Hui & Vasseur Standards Track [Page 2] + +RFC 6553 RPL Option March 2012 + + + RPL constructs a Directed Acyclic Graph (DAG) that attempts to + minimize path costs to the DAG root according to a set of metrics 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 defines 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 between RPL routers participating in the same + RPL Instance. + +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]. + +2. Overview + + The RPL Option provides a mechanism to include routing information + with each datagram that a router forwards. When receiving datagrams + that include routing information, RPL routers process the routing + information to help maintain the routing topology. + + Every RPL router along a packet's delivery path processes and updates + the RPL Option. If the received packet does not already contain a + RPL Option, the RPL router must insert a RPL Option before forwarding + it to another RPL router. This document also specifies the use of + IPv6-in-IPv6 tunneling [RFC2473] when attaching a RPL option to a + packet. Use of tunneling ensures that the original packet remains + unmodified and that ICMP errors return to the RPL Option source + rather than the source of the original packet. + +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: + + + + + + + + + + + + +Hui & Vasseur Standards Track [Page 3] + +RFC 6553 RPL Option March 2012 + + + 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: 0x63 + + 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 11.2 of [RFC6550]. The + processing SHALL follow the rules described in Section 11.2 of + [RFC6550]. + + Rank-Error 'R': 1-bit flag as defined in Section 11.2 of [RFC6550]. + The processing SHALL follow the rules described in Section 11.2 + of [RFC6550]. + + Forwarding-Error 'F': 1-bit flag as defined in Section 11.2 of + [RFC6550]. The processing SHALL follow the rules described in + Section 11.2 of [RFC6550]. + + RPLInstanceID: 8-bit field as defined in Section 11.2 of [RFC6550]. + The processing SHALL follow the rules described in Section 11.2 + of [RFC6550]. + + SenderRank: 16-bit field as defined in Section 11.2 of [RFC6550]. + The processing SHALL follow the rules described in Section 11.2 + of [RFC6550]. + + The two high order bits of the Option Type MUST be set to '01' and + the third bit is equal to '1'. With these bits, according to + [RFC2460], nodes that do not understand this option on a received + packet MUST discard the packet. Also, according to [RFC2460], the + values within the RPL Option are expected to change en route. The + RPL Option Data Length is variable. + + + + + + + + +Hui & Vasseur Standards Track [Page 4] + +RFC 6553 RPL Option March 2012 + + + 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 uses that option. No sub-TLVs are defined in + this document. A RPL device MUST skip over any unrecognized sub-TLVs + and attempt to process any additional sub-TLVs that may appear after. + +4. RPL Router Behavior + + Datagrams sent between RPL routers MUST include a RPL Option or RPL + Source Route Header ([RFC6554]) and MAY include both. A datagram + including a Source Routing Header (SRH) does not need to include a + RPL Option since both the source and intermediate routers ensure that + the SRH does not contain loops. + + When the router is the source of the original packet and the + destination is known to be within the same RPL Instance, the router + SHOULD include the RPL Option directly within the original packet. + Otherwise, routers MUST use IPv6-in-IPv6 tunneling [RFC2473] and + place the RPL Option in the tunnel header. Using IPv6-in-IPv6 + tunneling ensures that the delivered datagram remains unmodified and + that ICMPv6 errors generated by a RPL Option are sent back to the + router that generated the RPL Option. + + A RPL router chooses the next RPL router that should process the + original packet as the tunnel exit-point. In some cases, the tunnel + exit-point will be the final RPL router along a path towards the + original packet's destination, and the original packet will only + traverse a single tunnel. One example is when the final destination + or the destination's attachment router is known to be within the same + RPL Instance. + + In other cases, the tunnel exit-point will not be the final RPL + router along a path and the original packet may traverse multiple + tunnels to reach the destination. One example is when a RPL router + is simply forwarding a packet to one of its Destination-Oriented DAG + (DODAG) parents. In this case, the RPL router sets the tunnel exit- + point to a DODAG parent. When forwarding the original packet hop-by- + hop, the RPL router only makes a determination on the next hop + towards the destination. + + A RPL router receiving an IPv6-in-IPv6 packet destined to it + processes the tunnel packet as described in Section 3 of [RFC2473]. + Before IPv6 decapsulation, the RPL router MUST process the RPL + Option, if one exists. After IPv6 decapsulation, if the router + determines that it should forward the original packet to another RPL + router, it MUST encapsulate the packet again using IPv6-in-IPv6 + + + + + +Hui & Vasseur Standards Track [Page 5] + +RFC 6553 RPL Option March 2012 + + + tunneling to include the RPL Option. Fields within the RPL Option + that do not change hop-by-hop MUST remain the same as those received + from the prior tunnel. + + RPL routers are responsible for ensuring that a RPL Option is only + used between RPL routers: + + 1. For datagrams destined to a RPL router, the router processes the + packet in the usual way. For instance, if the RPL Option was + included using tunneled mode and the RPL router serves as the + tunnel endpoint, the router removes the outer IPv6 header, at the + same time removing the RPL Option as well. + + 2. Datagrams destined elsewhere within the same RPL Instance are + forwarded to the correct interface. + + 3. Datagrams destined to nodes outside the RPL Instance are dropped + if the outermost IPv6 header contains a RPL Option not generated + by the RPL router forwarding the datagram. + + To avoid fragmentation, it is desirable to employ MTU sizes that + allow for the header expansion (i.e., at least 1280 + 40 (outer IP + header) + RPL_OPTION_MAX_SIZE), where RPL_OPTION_MAX_SIZE is the + maximum RPL Option header size for a given RPL network. To take + advantage of this, however, the communicating endpoints need to be + aware of the MTU along the path (i.e., through Path MTU Discovery). + Unfortunately, the larger MTU size may not be available on all links + (e.g., 1280 octets on IPv6 Low-Power Wireless Personal Area Network + (6LoWPAN) links). However, it is expected that much of the traffic + on these types of networks consists of much smaller messages than the + MTU, so performance degradation through fragmentation would be + limited. + +5. Security Considerations + + The RPL Option assists RPL routers in detecting routing + inconsistencies. The RPL message security mechanisms defined in + [RFC6550] do not apply to the RPL Option. + +5.1. DAG Inconsistency Attacks + + Using the Down 'O' flag and SenderRank field, an attacker can cause + RPL routers to believe that a DAG inconsistency exists within the RPL + Instance identified by the RPLInstanceID field. This attack would + cause a RPL router to reset its DODAG Information Object (DIO) + Trickle timer and begin transmitting DIO messages more frequently. + + + + + +Hui & Vasseur Standards Track [Page 6] + +RFC 6553 RPL Option March 2012 + + + In order to avoid any unacceptable impact on network operations, an + implementation MAY limit the rate of Trickle timer resets caused by + receiving a RPL Option to no greater than MAX_RPL_OPTION_RANK_ERRORS + per hour. A RECOMMENDED value for MAX_RPL_OPTION_RANK_ERRORS is 20. + +5.2. Destination Advertisement Object (DAO) Inconsistency Attacks + + In Storing mode, RPL routers maintain Downward routing state. Under + normal operation, the RPL Option assists RPL routers in cleaning up + stale Downward routing state by using the Forwarding-Error 'F' flag + to indicate that a datagram could not be delivered by a child and is + being sent back to try a different child. Using this flag, an + attacker can cause a RPL router to discard Downward routing state. + + In order to avoid any unacceptable impact on network operations, an + implementation MAY limit the rate of discarding Downward routing + state caused by receiving a RPL Option to no greater than + MAX_RPL_OPTION_FORWARD_ERRORS per hour. A RECOMMENDED value for + MAX_RPL_OPTION_FORWARD_ERRORS is 20. + + In Non-Storing mode, only the Low-Power and Lossy Network Border + Router (LBR) maintains Downward routing state. Because RPL routers + do not maintain Downward routing state, the RPL Option cannot be used + to mount such attacks. + +6. IANA Considerations + + IANA has assigned a new value in the Destination Options and Hop-by- + Hop Options registry. The value is as follows: + + Hex Value Binary Value + act chg rest Description Reference + --------- --- --- ------- ----------------- ---------- + 0x63 01 1 00011 RPL Option [RFC6553] + + 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. + + IANA has created a registry called RPL-option-TLV, for the sub-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 Standards Track [Page 7] + +RFC 6553 RPL Option March 2012 + + +7. Acknowledgements + + The authors thank Jari Arkko, Ralph Droms, Adrian Farrel, Stephen + Farrell, Richard Kelsey, Suresh Krishnan, Vishwas Manral, Erik + Nordmark, Pascal Thubert, Sean Turner, and Tim Winter, for their + comments and suggestions that helped shape this document. + +8. References + +8.1. Normative References + + [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. + + [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, + "The Trickle Algorithm", RFC 6206, March 2011. + + [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., + Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, + JP., and R. Alexander, "RPL: IPv6 Routing Protocol for + Low-Power and Lossy Networks", RFC 6550, March 2012. + +8.2. Informative References + + [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 + Routing Header for Source Routes with the Routing Protocol + for Low-Power and Lossy Networks (RPL)", RFC 6554, + March 2012. + + + + + + + + + + + +Hui & Vasseur Standards Track [Page 8] + +RFC 6553 RPL Option March 2012 + + +Authors' Addresses + + Jonathan W. Hui + Cisco Systems + 170 West Tasman Drive + San Jose, California 95134 + USA + + Phone: +408 424 1547 + EMail: jonhui@cisco.com + + + JP. Vasseur + Cisco Systems + 11, Rue Camille Desmoulins + Issy Les Moulineaux 92782 + France + + EMail: jpv@cisco.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Hui & Vasseur Standards Track [Page 9] + |