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Internet Engineering Task Force (IETF)                      G. CamarilloRequest for Comments: 6028                                    A. KeranenCategory: Experimental                                          EricssonISSN: 2070-1721                                             October 2010Host Identity Protocol (HIP) Multi-Hop Routing ExtensionAbstract   This document specifies two extensions to the Host Identity Protocol   (HIP) to implement multi-hop routing.  The first extension allows   implementing source routing in HIP.  That is, a node sending a HIP   packet can define a set of nodes that the HIP packet should traverse.   The second extension allows a HIP packet to carry and record the list   of nodes that forwarded it.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for examination, experimental implementation, and   evaluation.   This document defines an Experimental Protocol for the Internet   community.  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).  Not   all documents approved by the IESG are a candidate for any level of   Internet Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6028.Camarillo & Keranen           Experimental                      [Page 1]

RFC 6028             HIP Multi-Hop Routing Extension        October 2010Copyright Notice   Copyright (c) 2010 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Table of Contents1. Introduction ....................................................22. Terminology .....................................................32.1. Requirements Language ......................................32.2. Definitions ................................................33. Protocol Definitions ............................................33.1. Creating and Processing Via Lists ..........................43.2. Creating Destination Lists .................................43.3. Processing Destination Lists ...............................53.4. Fragmentation Considerations ...............................54. Packet Formats ..................................................54.1. Source and Destination Route List Parameters ...............65. IANA Considerations .............................................76. Security Considerations .........................................86.1. Forged Destination and Via Lists ...........................86.2. Forwarding Loops ...........................................87. Acknowledgments .................................................98. References ......................................................98.1. Normative References .......................................98.2. Informative References .....................................91.  Introduction   When the Host Identity Protocol (HIP) [RFC5201] is used in certain   contexts, nodes need the ability to perform source routing.  That is,   a node needs the ability to send a HIP signaling packet that will   traverse a set of nodes before reaching its destination.  Such   features are needed, e.g., in the HIP-Based Overlay Networking   Environment (HIP BONE) [HIP-BONE] or if two nodes wish to keep a   third, or more, HIP nodes on the signaling path.  This document   defines an extension that provides HIP with this functionality.Camarillo & Keranen           Experimental                      [Page 2]

RFC 6028             HIP Multi-Hop Routing Extension        October 2010   Additionally, when HIP signaling packets are routed through multiple   nodes, some of these nodes (e.g., the destination host) need the   ability to know the nodes that a particular packet traversed.  This   document defines another extension that provides HIP with this   functionality.   These two extensions enable multi-hop routing in HIP.  Before these   extensions were specified, there were standardized ways for   supporting only a single intermediate node (e.g., a rendezvous server   [RFC5204]) between the source of a HIP packet and its destination.2.  Terminology2.1.  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 inRFC 2119 [RFC2119].2.2.  Definitions   The following terms used in this document are similar to those   defined by REsource LOcation And Discovery (RELOAD) [P2PSIP-BASE] but   are used here in the context of HIP.   Destination list:  A list of Host Identity Tags (HITs) of the nodes      that a HIP packet should traverse.   Via list:  A list of HITs of the nodes that a HIP packet has      traversed.   Symmetric routing:  A response to a message is routed back using the      same set of intermediary nodes as the original message used,      except in reversed order.  Also known as symmetric recursive      routing.3.  Protocol Definitions   The multi-hop routing extensions may be used in different contexts,   and whether a new HIP signaling packet should, for example, include a   Via list or have different options enabled can depend on the   particular use case, local policies, and different protocols using   the extension.  This section defines how the new parameters are   handled, but when to use these extensions, or how to configure them,   is out of scope for this document.Camarillo & Keranen           Experimental                      [Page 3]

RFC 6028             HIP Multi-Hop Routing Extension        October 20103.1.  Creating and Processing Via Lists   When a node sending a HIP packet needs to record the nodes that are   on the path that the HIP packet traverses, it includes an empty   ROUTE_VIA parameter in the packet.   A node that receives a packet with a ROUTE_VIA parameter SHOULD add   its own HIT to the end of the ROUTE_VIA parameter, unless it is the   final recipient of the packet.  If the node uses a different HIT on   the HIP association it used for receiving the packet than for sending   it forward, it SHOULD also add the receiving HIT to the route list   before the sending HIT.   If the node is the final recipient of the packet, and the received   packet generates a response HIP packet, the node checks the SYMMETRIC   flag from the ROUTE_VIA parameter.  If the SYMMETRIC flag is set, the   node MUST create a ROUTE_DST parameter from the ROUTE_VIA parameter,   as described inSection 3.2, and include it in the response packet.   Also, if an intermediary node generates a new HIP packet (e.g., an   error NOTIFY packet) due to a HIP packet that had a ROUTE_VIA   parameter with the SYMMETRIC flag set, and the new packet is intended   for the sender of the original HIP packet, the node SHOULD construct   and add a ROUTE_DST parameter into the new packet as in the previous   case.3.2.  Creating Destination Lists   A node that needs to define the other nodes that should be on the   path a HIP packet traverses adds a ROUTE_DST parameter to the HIP   packet.  The node may either decide the path independently, or it may   create the path based on a ROUTE_VIA parameter.  Only the originator   of a signed HIP packet can add a ROUTE_DST parameter to the HIP   packet, and none of the nodes on the path can modify it, since the   parameter is covered by the signature.   When a node creates a ROUTE_DST parameter due to receiving a packet   with a ROUTE_VIA parameter, it copies all the HITs in the ROUTE_VIA   parameter to the ROUTE_DST parameter, but in reversed order.  This   results in the HIP response packet being forwarded using the same   path as the packet for which the response was generated.  If exactly   the same set of nodes should be traversed by the response packet, the   MUST_FOLLOW flag (see Table 1) also SHOULD be set in the ROUTE_VIA   parameter (and eventually copied to the ROUTE_DST parameter) to   prevent the response packet from possibly skipping some nodes on the   list.Camarillo & Keranen           Experimental                      [Page 4]

RFC 6028             HIP Multi-Hop Routing Extension        October 20103.3.  Processing Destination Lists   When a node receives a HIP packet that contains a ROUTE_DST   parameter, it first looks up its own HIT from the route list.  If the   node's own HIT is not in the list and the node is not the receiver of   the packet, the packet was incorrectly forwarded and MUST be dropped.   If the node's HIT is in the list more than once, the list is invalid   and the packet MUST be dropped to avoid forwarding loops.  The next   hop for the packet is the HIT after the node's own HIT in the list.   If the node's HIT was the last HIT in the list, the next hop is the   receiver's HIT in the HIP header.   If the MUST_FOLLOW flag in the ROUTE_DST parameter is not set, the   node SHOULD check whether it has a valid locator for one of the nodes   later in the list, or for the receiver of the packet, and it MAY   select such a node as the next hop.  If the MUST_FOLLOW flag is set,   the node MUST NOT skip any nodes in the list.   If the node has a valid locator for the next hop, it MUST forward the   HIP packet to the next-hop node.  If the node cannot determine a   valid locator for the next-hop node, it SHOULD drop the packet and   SHOULD send back a NOTIFY error packet with type UNKNOWN_NEXT_HOP   (value 90).  The Notification Data field for the error notifications   SHOULD contain the HIP header of the rejected packet and the   ROUTE_DST parameter.3.4.  Fragmentation Considerations   Via and Destination lists with multiple HITs can substantially   increase the size of the HIP packets, and thus fragmentation issues   (seeSection 5.1.3 of [RFC5201]) should be taken into consideration   when these extensions are used.  Via lists in particular should be   used with care, since the final size of the packet is not known   unless the maximum possible amount of hops is known beforehand.  Both   parameters do still have a maximum size based on the maximum number   of allowed HITs (seeSection 4.1).4.  Packet Formats   This memo defines two new HIP parameters that are used for recording   a route via multiple nodes (ROUTE_VIA) and for defining a route that   a packet should traverse by the sender of the packet (ROUTE_DST).Camarillo & Keranen           Experimental                      [Page 5]

RFC 6028             HIP Multi-Hop Routing Extension        October 2010   The ROUTE_DST parameter is integrity protected with the signature   (where present) but ROUTE_VIA is not, so that intermediary nodes can   add their own HITs to the list.  Both ROUTE_DST and ROUTE_VIA are   critical parameters (as defined inSection 5.2.1 of [RFC5201]), since   the packet will not be properly routed unless all nodes on the path   recognize the parameters.4.1.  Source and Destination Route List Parameters      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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |             Type              |             Length            |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |             Flags             |            Reserved           |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                                                               |     |                            HIT #1                             |     |                                                               |     |                                                               |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     .                               .                               .     .                               .                               .     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     |                                                               |     |                            HIT #n                             |     |                                                               |     |                                                               |     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     Type      ROUTE_DST: 4601               ROUTE_VIA: 64017     Length    length in octets, excluding Type and Length               (i.e., number-of-HITs * 16 + 4)     Flags     bit flags that can be used for requesting special               handling of the parameter     Reserved  reserved for future use     HIT       Host Identity Tag of one of the nodes on the path        Figure 1.  Format of the ROUTE_VIA and ROUTE_DST Parameters   Figure 1 shows the format of both ROUTE_VIA and ROUTE_DST parameters.   The ROUTE_DST parameter, if present, MUST have at least one HIT, but   the ROUTE_VIA parameter can also have zero HITs.  The ROUTE_DST and   ROUTE_VIA parameters SHALL NOT contain more than 32 HITs.  The FlagsCamarillo & Keranen           Experimental                      [Page 6]

RFC 6028             HIP Multi-Hop Routing Extension        October 2010   field is used for requesting special handling for Via and Destination   lists.  The flags defined in this document are shown in Table 1.  The   Reserved field can be used by future extensions; it MUST be zero when   sending and ignored when receiving this parameter.   +-----+-------------+-----------------------------------------------+   | Pos | Name        | Purpose                                       |   +-----+-------------+-----------------------------------------------+   |  0  | SYMMETRIC   | The response packet MUST be sent with a       |   |     |             | ROUTE_DST list made from the ROUTE_VIA list   |   |     |             | containing this flag, i.e., using symmetric   |   |     |             | routing.                                      |   |  1  | MUST_FOLLOW | All the nodes in a ROUTE_DST list MUST be     |   |     |             | traversed, i.e., even if a node would have a  |   |     |             | valid locator for a node beyond the next hop, |   |     |             | it MUST NOT forward the packet there but to   |   |     |             | the next-hop node.                            |   +-----+-------------+-----------------------------------------------+         Table 1.  Bit Flags in ROUTE_VIA and ROUTE_DST Parameters   The "Pos" column in Table 1 shows the bit position of the flag (as in   Figure 1) in the Flags field, "Name" gives the name of the flag used   in this document, and "Purpose" gives a brief description of the   meaning of that flag.   The flags apply to both ROUTE_VIA and ROUTE_DST parameters, and when   a ROUTE_DST parameter is added to a packet because of a ROUTE_VIA   parameter, the same flags MUST be copied to the ROUTE_DST parameter.5.  IANA Considerations   This section is to be interpreted according to [RFC5226].   This document updates the IANA Registry for HIP Parameter Types   [RFC5201] by assigning new HIP Parameter Type values for the new HIP   Parameters: ROUTE_VIA and ROUTE_DST (defined inSection 4).  This   document also defines a new Notify Packet Type [RFC5201],   UNKNOWN_NEXT_HOP, inSection 3.3.   The ROUTE_DST and ROUTE_VIA parameters utilize bit flags, for which   IANA has created and now maintains a new sub-registry entitled "HIP   Via Flags" under the "Host Identity Protocol (HIP) Parameters"   registry.  Initial values for the registry are given in Table 1;   future assignments are to be made through IETF Review or IESG   Approval [RFC5226].  Assignments consist of the bit position and the   name of the flag.Camarillo & Keranen           Experimental                      [Page 7]

RFC 6028             HIP Multi-Hop Routing Extension        October 20106.  Security Considerations   The standard HIP mechanisms (e.g., using signatures, puzzles, and the   ENCRYPTED parameter [RFC5201]) provide protection against   eavesdropping; replay; message insertion, deletion, and modification;   and man-in-the-middle attacks.  Yet, the extensions described in this   document allow nodes to route HIP messages via other nodes and hence   possibly try to mount Denial-of-Service (DoS) attacks against them.   The following sections describe possible attacks and means to   mitigate them.6.1.  Forged Destination and Via Lists   The Destination list is protected by the HIP signature so that the   receiver of the message can check that the list was indeed created by   the sender of the message and not modified on the path.  Also, the   nodes forwarding the message MAY check the signature of the forwarded   packets if they have the Host Identity (HI) of the sender (e.g., from   an I2 or R1 message [RFC5201]) and drop packets whose signature check   fails.  With forwarding nodes checking the signature and allowing   messages to be forwarded only from nodes for which there is an active   HIP association, it is also possible to reliably identify attacking   nodes.   The limited amount of HITs allowed in a Destination list limits the   impact of attacks using a forged Destination list, and the attacker   also needs to know a set of HIP nodes that are able to route the   message hop-by-hop for the attack to be effective.   A forged Via list results in a similar attack as with the Destination   list and with similar limitations.  However, in this attack the   Destination list generated from the Via list is validly signed by the   responding node.  To limit the effect of this kind of attack, a   responding node may further decrease the maximum acceptable number of   nodes in the Via lists or allow only certain HITs in the lists.   However, using these mechanisms requires either good knowledge of the   overlay network (i.e., maximum realistic amount of hops) or knowing   the HITs of all potential nodes forwarding the messages.6.2.  Forwarding Loops   A malicious node could craft a destination route list that contains   the same HIT more than once and thus create a forwarding loop.  The   check described inSection 3.3 should break such loops, but nodes MAY   in addition utilize the OVERLAY_TTL [HIP-BONE] parameter for   additional protection against forwarding loops.Camarillo & Keranen           Experimental                      [Page 8]

RFC 6028             HIP Multi-Hop Routing Extension        October 20107.  Acknowledgments   Tom Henderson provided valuable comments and improvement suggestions   for this document.8.  References8.1.  Normative References   [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate                  Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC5201]      Moskowitz, R., Nikander, P., Jokela, P., Ed., and T.                  Henderson, "Host Identity Protocol",RFC 5201, April                  2008.8.2.  Informative References   [RFC5204]      Laganier, J. and L. Eggert, "Host Identity Protocol                  (HIP) Rendezvous Extension",RFC 5204, April 2008.   [RFC5226]      Narten, T. and H. Alvestrand, "Guidelines for Writing                  an IANA Considerations Section in RFCs",BCP 26,RFC5226, May 2008.   [HIP-BONE]     Camarillo, G., Nikander, P., Hautakorpi, J., Keranen,                  A., and A. Johnston, "HIP BONE: Host Identity Protocol                  (HIP) Based Overlay Networking Environment", Work in                  Progress, June 2010.   [P2PSIP-BASE]  Jennings, C., Lowekamp, B., Ed., Rescorla, E., Baset,                  S., and H. Schulzrinne, "REsource LOcation And                  Discovery (RELOAD) Base Protocol", Work in Progress,                  March 2010.Camarillo & Keranen           Experimental                      [Page 9]

RFC 6028             HIP Multi-Hop Routing Extension        October 2010Authors' Addresses   Gonzalo Camarillo   Ericsson   Hirsalantie 11   02420 Jorvas   Finland   EMail: Gonzalo.Camarillo@ericsson.com   Ari Keranen   Ericsson   Hirsalantie 11   02420 Jorvas   Finland   EMail: Ari.Keranen@ericsson.comCamarillo & Keranen           Experimental                     [Page 10]