--- 1/draft-ietf-6lo-rfc6775-update-04.txt 2017-05-12 03:13:09.665270823 -0700 +++ 2/draft-ietf-6lo-rfc6775-update-05.txt 2017-05-12 03:13:09.729272321 -0700 @@ -1,20 +1,20 @@ 6lo P. Thubert, Ed. Internet-Draft cisco Updates: 6775 (if approved) E. Nordmark Intended status: Standards Track -Expires: November 2, 2017 S. Chakrabarti - May 1, 2017 +Expires: November 13, 2017 S. Chakrabarti + May 12, 2017 An Update to 6LoWPAN ND - draft-ietf-6lo-rfc6775-update-04 + draft-ietf-6lo-rfc6775-update-05 Abstract This specification updates RFC 6775 - 6LoWPAN Neighbor Discovery, to clarify the role of the protocol as a registration technique, simplify the registration operation in 6LoWPAN routers, and provide enhancements to the registration capabilities, in particular for the registration to a Backbone Router for proxy ND operations. Status of This Memo @@ -25,21 +25,21 @@ 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 November 2, 2017. + This Internet-Draft will expire on November 13, 2017. Copyright Notice Copyright (c) 2017 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 @@ -47,83 +47,80 @@ 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 Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Considerations On Registration Rejection . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 4. Extending RFC 7400 . . . . . . . . . . . . . . . . . . . . . 5 - 5. Updating RFC 6775 . . . . . . . . . . . . . . . . . . . . . . 5 - 5.1. Extended Address Registration Option . . . . . . . . . . 6 - 5.2. Transaction ID . . . . . . . . . . . . . . . . . . . . . 6 - 5.3. Owner Unique ID . . . . . . . . . . . . . . . . . . . . . 7 - 5.4. Registering the Target Address . . . . . . . . . . . . . 8 - 5.5. Link-Local Addresses and Registration . . . . . . . . . . 8 - 5.6. Maintaining the Registration States . . . . . . . . . . . 10 + 4. Updating RFC 6775 . . . . . . . . . . . . . . . . . . . . . . 5 + 4.1. Extended Address Registration Option . . . . . . . . . . 5 + 4.2. Transaction ID . . . . . . . . . . . . . . . . . . . . . 6 + 4.3. Owner Unique ID . . . . . . . . . . . . . . . . . . . . . 7 + 4.4. Registering the Target Address . . . . . . . . . . . . . 7 + 4.5. Link-Local Addresses and Registration . . . . . . . . . . 8 + 4.6. Maintaining the Registration States . . . . . . . . . . . 9 + 5. Extending RFC 7400 . . . . . . . . . . . . . . . . . . . . . 11 6. Updated ND Options . . . . . . . . . . . . . . . . . . . . . 11 - 6.1. New 6LoWPAN capability Bits in the Capability Indication - Option . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 6.2. The Enhanced Address Registration Option (EARO) . . . . . 12 + 6.1. The Enhanced Address Registration Option (EARO) . . . . . 11 + 6.2. New 6LoWPAN capability Bits in the Capability Indication + Option . . . . . . . . . . . . . . . . . . . . . . . . . 14 7. Backward Compatibility . . . . . . . . . . . . . . . . . . . 14 7.1. Discovering the capabilities of an ND peer . . . . . . . 14 7.1.1. Using the E Flag in the CIO . . . . . . . . . . . . . 14 7.1.2. Using the T Flag in the EARO . . . . . . . . . . . . 15 7.2. Legacy 6LoWPAN Node . . . . . . . . . . . . . . . . . . . 15 7.3. Legacy 6LoWPAN Router . . . . . . . . . . . . . . . . . . 16 7.4. Legacy 6LoWPAN Border Router . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 11.1. Normative References . . . . . . . . . . . . . . . . . . 20 11.2. Informative References . . . . . . . . . . . . . . . . . 21 - 11.3. External Informative References . . . . . . . . . . . . 23 + 11.3. External Informative References . . . . . . . . . . . . 24 Appendix A. Applicability and Requirements Served . . . . . . . 24 - Appendix B. Requirements . . . . . . . . . . . . . . . . . . . . 24 + Appendix B. Requirements . . . . . . . . . . . . . . . . . . . . 25 B.1. Requirements Related to Mobility . . . . . . . . . . . . 25 B.2. Requirements Related to Routing Protocols . . . . . . . . 25 B.3. Requirements Related to the Variety of Low-Power Link types . . . . . . . . . . . . . . . . . . . . . . . . . . 26 B.4. Requirements Related to Proxy Operations . . . . . . . . 27 B.5. Requirements Related to Security . . . . . . . . . . . . 27 - B.6. Requirements Related to Scalability . . . . . . . . . . . 28 + B.6. Requirements Related to Scalability . . . . . . . . . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 1. Introduction RFC 6775, the "Neighbor Discovery Optimization for IPv6 over Low- Power Wireless Personal Area Networks (6LoWPANs)" [RFC6775] introduced a proactive registration mechanism to IPv6 Neighbor Discovery (ND) services that is well suited to nodes belonging to a Low Power Lossy Network (LLN). The scope of this draft is an IPv6 LLN, which can be a simple star or a more complex mesh topology. The LLN may be anchored at an IPv6 - Backbone Router (6BBR) [I-D.ietf-6lo-backbone-router]. The 6BBRs - interconnect the LLNs over a Backbone Link and emulate that the LLN - nodes are present on the Backbone using proxy-ND operations. - - This specification modifies and extends the behavior and protocol - elements of RFC 6775 [RFC6775] to enable additional capabilities, in + Backbone Router (6BBR) [I-D.ietf-6lo-backbone-router]. This + specification modifies and extends the behavior and protocol elements + of RFC 6775 [RFC6775] to enable additional capabilities, in particular the registration to a 6BBR for proxy ND operations. 2. Considerations On Registration Rejection - The purpose of the Address Registration Option (ARO) RFC 6775 - [RFC6775] and of the Extended ARO (EARO) that is introduced in this - document is to facilitate duplicate address detection (DAD) for hosts - and pre-populate Neighbor Cache Entries (NCE) [RFC4861] in the - routers to reduce the need for sending multicast neighbor - solicitations and also to be able to support IPv6 Backbone Routers. + The purpose of the Address Registration Option (ARO) [RFC6775] and of + the Extended ARO (EARO) that is introduced in this document is to + facilitate duplicate address detection (DAD) for hosts and pre- + populate Neighbor Cache Entries (NCE) [RFC4861] in the routers to + reduce the need for sending multicast neighbor solicitations and also + to be able to support IPv6 Backbone Routers. In some cases the address registration can fail or be useless for reasons other than a duplicate address. Examples are the router having run out of space, a registration bearing a stale sequence number (e.g. denoting a movement of the host after this registration was placed), a host misbehaving and attempting to register an invalid address such as the unspecified address [RFC4291], or the host using an address which is not topologically correct on that link. In such cases the host will receive an error to help diagnose the issue and may retry, possibly with a different address, and possibly @@ -168,34 +165,34 @@ "Terms Used in Routing for Low-Power and Lossy Networks" [RFC7102] and the "6TiSCH Terminology" [I-D.ietf-6tisch-terminology], as well as this additional terminology: Backbone This is an IPv6 transit link that interconnects 2 or more Backbone Routers. It is expected to be deployed as a high - speed backbone in order to federate a potentially large set of - LLNS. Also referred to as a LLN backbone or Backbone network. + speed Backbone in order to federate a potentially large set of + LLNS. Also referred to as a LLN Backbone or Backbone network. Backbone Router An IPv6 router that federates the LLN using a - Backbone link as a backbone. A 6BBR acts as a 6LoWPAN Border + Backbone link as a Backbone. A 6BBR acts as a 6LoWPAN Border Routers (6LBR) and an Energy Aware Default Router (NEAR). Extended LLN This is the aggregation of multiple LLNs as defined in RFC 4919 [RFC4919], interconnected by a Backbone Link via Backbone Routers, and forming a single IPv6 MultiLink Subnet. Registration The process during which a wireless Node registers its address(es) with the Border Router so the 6BBR can proxy ND for - it over the backbone. + it over the Backbone. Binding The state in the 6BBR that associates an IP address with a MAC address, a port and some other information about the node that owns the IP address. Registered Node The node for which the registration is performed, which owns the fields in the EARO option. Registering Node The node that performs the registration to the 6BBR, either for one of its own addresses, in which case it is @@ -207,84 +204,70 @@ Address of the Registered Node as SLLA in the NS(EARO). Otherwise, it is expected that the Registered Device is reachable over a Route-Over mesh from the Registering Node, in which case the SLLA in the NS(ARO) is that of the Registering Node, which causes it to attract the packets from the 6BBR to the Registered Node and route them over the LLN. Registered Address The address owned by the Registered Node node that is being registered. -4. Extending RFC 7400 - - RFC 7400 [RFC7400] introduces the 6LoWPAN Capability Indication - Option (6CIO) to indicate a node's capabilities to its peers. This - specification extends the format defined in RFC 7400 to signal the - support for EARO, as well as the capability to act as a 6LR, 6LBR and - 6BBR. - - With RFC 7400 [RFC7400], the 6CIO is typically sent Router - Solicitation (RS) messages. When used to signal the capabilities - above per this specification, the 6CIO is typically present Router - Advertisement (RA) messages but can also be present in RS, Neighbor - Solicitation (NS) and Neighbor Advertisement (NA) messages. - -5. Updating RFC 6775 +4. Updating RFC 6775 This specification extends the Address Registration Option (ARO) defined in RFC 6775 [RFC6775]; in particular a "T" flag is added that must be set is NS messages when this specification is used, and echo'ed in NA messages to confirm that the protocol effectively supported. Support for this specification can thus be inferred from the presence of the Extended ARO ("T" flag set) in ND messages. In order to support various types of link layers, this specification also adds recommendation to allow multiple registrations, including for privacy / temporary addresses, and provides new mechanisms to help clean up stale registration states as soon as possible. A Registering Node that supports this specification will favor registering to a 6LR that indicates support for this specification over that of RFC 6775 [RFC6775]. -5.1. Extended Address Registration Option +4.1. Extended Address Registration Option This specification extends the ARO option that is used for the process of address registration. The new ARO is referred to as Extended ARO (EARO), and its semantics are modified as follows: The address that is being registered with a Neighbor Solicitation (NS) with an EARO is now the Target Address, as opposed to the Source - Address as specified in RFC 6775 [RFC6775] (see Section 5.4 for + Address as specified in RFC 6775 [RFC6775] (see Section 4.4 for more). This change enables a 6LBR to use an address of his as source to the proxy-registration of an address that belongs to a LLN Node to a 6BBR. This also limits the use of an address as source address before it is registered and the associated Duplicate Address Detection (DAD) is complete. The Unique ID in the EARO option does no more have to be a MAC - address (see Section 5.3 for more). This enables in particular the + address (see Section 4.3 for more). This enables in particular the use of a Provable Temporary UID (PT-UID) as opposed to burn-in MAC address, the PT-UID providing a trusted anchor by the 6LR and 6LBR to protect the state associated to the node. The specification introduces a Transaction ID (TID) field in the EARO - (see Section 5.2 for more on TID). The TID MUST be provided by a + (see Section 4.2 for more on TID). The TID MUST be provided by a node that supports this specification and a new T flag MUST be set to indicate so. The T bit can be used to determine whether the peer supports this specification. Finally, this specification introduces a number of new Status codes to help diagnose the cause of a registration failure (more in Table 1). -5.2. Transaction ID +4.2. Transaction ID The specification expects that the Registered Node can provide a sequence number called Transaction ID (TID) that is incremented with each re-registration. The TID essentially obeys the same rules as the Path Sequence field in the Transit Information Option (TIO) found in the RPL Destination Advertisement Object (DAO) [RFC6550]. This way, the LLN node can use the same counter for ND and RPL, and a 6LBR acting as RPL root may easily maintain the registration on behalf of a RPL node deep inside the mesh by simply using the RPL TIO Path Sequence as TID for EARO. @@ -296,44 +279,44 @@ If the TIDs are different, a conflict resolution inherited from RPL sorts out the most recent registration and other ones are removed. The operation for computing and comparing the Path Sequence is detailed in section 7 of RFC 6550 [RFC6550] and applies to the TID in the exact same fashion. The resolution is used to determine the freshest registration for a particular address, and an EARO is processed only if it is the freshest, otherwise a Status code 3 "Moved" is returned. -5.3. Owner Unique ID +4.3. Owner Unique ID The Owner Unique ID (OUID) enables to differentiate a real duplicate address registration from a double registration or a movement. An ND - message from the 6BBR over the backbone that is proxied on behalf of + message from the 6BBR over the Backbone that is proxied on behalf of a Registered Node must carry the most recent EARO option seen for that node. A NS/NA with an EARO and a NS/NA without a EARO thus represent different nodes and if they relate to a same target then they reflect an address duplication. The Owner Unique ID can be as simple as a EUI-64 burn-in address, if duplicate EUI-64 addresses are avoided. Alternatively, the unique ID can be a cryptographic string that can can be used to prove the ownership of the registration as discussed in "Address Protected Neighbor Discovery for Low-power and Lossy Networks" [I-D.ietf-6lo-ap-nd]. In any fashion, it is recommended that the node stores the unique Id or the keys used to generate that ID in persistent memory. Otherwise, it will be prevented to re-register after a reboot that would cause a loss of memory until the Backbone Router times out the registration. -5.4. Registering the Target Address +4.4. Registering the Target Address This specification changes the behavior of the 6LN and the 6LR so that the Registered Address is found in the Target Address field of the NS and NA messages as opposed to the Source Address. The reason for this change is to enable proxy-registrations on behalf of other nodes in Route-Over meshes, for instance to enable that a RPL root registers addresses on behalf LLN nodes that are deeper in a 6TiSCH mesh, as discussed in Appendix B.4. In that case, the Registering Node MUST indicate its own address as source of the ND @@ -347,21 +330,21 @@ of the 6LN that owns the address, whereas the SLLA Option in a NS message indicates that of the Registering Node, which can be the owner device, or a proxy. Since the Registering Node is the one that has reachability with the 6LR, and is the one expecting packets for the 6LN, it makes sense to maintain compatibility with RFC 6775 [RFC6775], and it is REQUIRED that an SLLA Option is always placed in a registration NS(EARO) message. -5.5. Link-Local Addresses and Registration +4.5. Link-Local Addresses and Registration Considering that LLN nodes are often not wired and may move, there is no guarantee that a Link-Local address stays unique between a potentially variable and unbounded set of neighboring nodes. Compared to RFC 6775 [RFC6775], this specification only requires that a Link-Local address is unique from the perspective of the peering nodes. This simplifies the Duplicate Address Detection (DAD) for Link-Local addresses, and there is no DAR/DAC exchange between the 6LR and a 6LBR for Link-Local addresses. @@ -400,21 +383,21 @@ to the Source Address of an NS(EARO) message. For that reason, when possible, it is RECOMMENDED to use an address that is already registered with a 6LR When registering to a 6LR that conforms this specification, a node MUST use a Link-Local address as the source address of the registration, whatever the type of IPv6 address that is being registered. That Link-Local Address MUST be either already registered, or the address that is being registered. - When a Registering Node does not have an already-registered address, + When a Registering Node does not have an already-Registered Address, it MUST register a Link-Local address, using it as both the Source and the Target Address of an NS(EARO) message. In that case, it is RECOMMENDED to use a Link-Local address that is (expected to be) globally unique, e.g. derived from a burn-in MAC address. An EARO option in the response NA indicates that the 6LR supports this specification. Since there is no DAR/DAC exchange for Link-Local addresses, the 6LR may answer immediately to the registration of a Link-Local address, based solely on its existing state and the Source Link-Layer Option @@ -422,45 +405,45 @@ [RFC6775]. A node needs to register its IPv6 Global Unicast IPv6 Addresses (GUA) to a 6LR in order to obtain a global reachability for these addresses via that 6LR. As opposed to a node that complies to RFC 6775 [RFC6775], a Registering Node registering a GUA does not use that GUA as Source Address for the registration to a 6LR that conforms this specification. The DAR/DAC exchange MUST take place for non-Link- Local addresses as prescribed by RFC 6775 [RFC6775]. -5.6. Maintaining the Registration States +4.6. Maintaining the Registration States - This section discusses protocol actions that involve the registering - node, the 6LR and the 6LBR. It must be noted that the portion that + This section discusses protocol actions that involve the Registering + Node, the 6LR and the 6LBR. It must be noted that the portion that deals with a 6LBR only applies to those addresses that are registered - to it, which, as discussed in Section 5.5, is not the case for Link- + to it, which, as discussed in Section 4.5, is not the case for Link- Local addresses. The registration state includes all data that is stored in the router relative to that registration, in particular, but not limited to, an NCE in a 6LR. 6LBRs and 6BBRs may store additional registration information in more complex data structures and use protocols that are out of scope of this document to keep them synchonized when they are distributed. When its Neighbor Cache is full, a 6LR cannot accept a new registration. In that situation, the EARO is returned in a NA - message with a Status of 2, and the registering node may attempt to + message with a Status of 2, and the Registering Node may attempt to register to another 6LR. Conversely the registry in the 6LBR may be saturated, in which case the 6LBR cannot guarantee that a new address is effectively not a duplicate. In that case, the 6LBR replies to a DAR message with a DAC message that carries a Status code 9 indicating "6LBR Registry saturated", and the address stays in TENTATIVE state. A node renews an existing registration by repeatedly sending NS(EARO) - messages for the registered address. In order to refresh the + messages for the Registered Address. In order to refresh the registration state in the 6LBR, these registrations MUST be reported to the 6LBR. This is normally done through a DAR/DAC exchange, but the refresh MAY alternatively be piggy-backed in another protocol such as RPL [RFC6550], as long as the semantics of the EARO are fully carried in the alternate protocol. In the particular case of RPL, the TID MUST be used as the Path Sequence in the TIO, and the Registration Lifetime MUST be used as Path Lifetime. It is also REQUIRED that the root of the RPL DODAG passes that information to the 6LBR on behalf of the 6LR, either through a DAR/DAC exchange, or through internal methods if they are collocated. @@ -468,84 +451,66 @@ A node that ceases to use an address SHOULD attempt to deregister that address from all the 6LRs to which it has registered the address, which is achieved using an NS(EARO) message with a Registration Lifetime of 0. A node that moves away from a particular 6LR SHOULD attempt to deregister all of its addresses registered to that 6LR. Upon receiving a NS(EARO) message with a Registration Lifetime of 0 and determining that this EARO is the freshest for a given NCE (see - Section 5.2), a 6LR cleans up its NCE. If the address was registered + Section 4.2), a 6LR cleans up its NCE. If the address was registered to the 6LBR, then the 6LR MUST report to the 6LBR, through a DAR/DAC exchange with the 6LBR, or an alternate protocol, indicating the null Registration Lifetime and the latest TID that this 6LR is aware of. Upon the DAR message, the 6LBR evaluates if this is the freshest EARO it has received for that particular registry entry. If it is, then the entry is scheduled to be removed, and the DAR is answered with a DAC message bearing a Status of 0 "Success". If it is not the freshest, then a Status 2 "Moved" is returned instead, and the existing entry is conserved. The 6LBR SHOULD conserve the address in a DELAY state for a configurable period of time, so as to protect a mobile node that deregistered from one 6LR and did not register yet to a new one. -6. Updated ND Options - - This specification does not introduce new options, but it modifies - existing ones and updates the associated behaviors as follow: - -6.1. New 6LoWPAN capability Bits in the Capability Indication Option - - This specification defines a number of capability bits in the CIO - that was introduced by RFC 7400 [RFC7400]. - - Support for this specification is indicated by setting the "E" flag - in a CIO option. Routers that are capable of acting as 6LR, 6LBR and - 6BBR SHOULD set the L, B and P flags, respectively. - - Those flags are not mutually exclusive and if a router is capable of - multiple roles, it SHOULD set all the related flags. - - 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 = 1 |_____________________|L|B|P|E|G| - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |_______________________________________________________________| - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - - Figure 1: New capability Bits L, B, P, E in the CIO - - Option Fields - Type: 36 +5. Extending RFC 7400 - L: Node is a 6LR, it can take registrations. + RFC 7400 [RFC7400] introduces the 6LoWPAN Capability Indication + Option (6CIO) to indicate a node's capabilities to its peers. This + specification extends the format defined in RFC 7400 to signal the + support for EARO, as well as the capability to act as a 6LR, 6LBR and + 6BBR. - B: Node is a 6LBR. + With RFC 7400 [RFC7400], the 6CIO is typically sent Router + Solicitation (RS) messages. When used to signal the capabilities + above per this specification, the 6CIO is typically present Router + Advertisement (RA) messages but can also be present in RS, Neighbor + Solicitation (NS) and Neighbor Advertisement (NA) messages. - P: Node is a 6BBR, proxying for nodes on this link. +6. Updated ND Options - E: This specification is supported and applied. + This specification does not introduce new options, but it modifies + existing ones and updates the associated behaviors as follow: -6.2. The Enhanced Address Registration Option (EARO) +6.1. The Enhanced Address Registration Option (EARO) The Enhanced Address Registration Option (EARO) is intended to be used as a replacement to the ARO option within Neighbor Discovery NS and NA messages between a LLN node and its 6LoWPAN Router (6LR), as well as in Duplicate Address Request (DAR) and the Duplicate Address Confirmation (DAC) messages between 6LRs and 6LBRs in LLNs meshes such as 6TiSCH networks. An NS message with an EARO option is a registration if and only if it also carries an SLLAO option. The AERO option also used in NS and NA - messages between Backbone Routers over the backbone link to sort out + messages between Backbone Routers over the Backbone link to sort out the distributed registration state, and in that case, it does not carry the SLLAO option and is not confused with a registration. The EARO extends the ARO and is recognized by the "T" flag set. When using the EARO option, the address being registered is found in the Target Address field of the NS and NA messages. This differs from 6LoWPAN ND RFC 6775 [RFC6775] which specifies that the address being registered is the source of the NS. @@ -556,21 +521,21 @@ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length = 2 | Status | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved |T| TID | Registration Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Owner Unique ID (EUI-64 or equivalent) + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Figure 2: EARO + Figure 1: EARO Option Fields Type: 33 Length: 8-bit unsigned integer. Status: 8-bit unsigned integer. Indicates the status of a registration in the NA response. MUST be set to 0 in NS messages. See Table 1 below. @@ -591,87 +556,117 @@ Owner Unique Identifier (OUI): A globally unique identifier for the node associated. This can be the EUI-64 derived IID of an interface, or some provable ID obtained cryptographically. +-------+-----------------------------------------------------------+ | Value | Description | +-------+-----------------------------------------------------------+ | 0..2 | See RFC 6775 [RFC6775]. Note that a Status of 1 | | | "Duplicate Address" applies to the Registered Address. If | | | the Source Address conflicts with an existing | - | | registration, "Duplicate Source Address" should be used | - | | instead | + | | registration, "Duplicate Source Address" should be used. | | | | | 3 | Moved: The registration fails because it is not the | | | freshest. This Status indicates that the registration is | | | rejected because another more recent registration was | | | done, as indicated by a same OUI and a more recent TID. | | | One possible cause is a stale registration that has | | | progressed slowly in the network and was passed by a more | | | recent one. It could also indicate a OUI collision. | | | | | 4 | Removed: The binding state was removed. This may be | | | placed in an asynchronous NS(ARO) message, or as the | | | rejection of a proxy registration to a Backbone Router | | | | - | 5 | Proof requested: The registering node is challenged for | - | | owning the registered address or for being an acceptable | + | 5 | Proof requested: The Registering Node is challenged for | + | | owning the Registered Address or for being an acceptable | | | proxy for the registration. This Status is expected in | | | asynchronous messages from a registrar (6LR, 6LBR, 6BBR) | | | to indicate that the registration state is removed, for | - | | instance due to time out of a lifetime, or a movement. It | - | | is used for instance by a 6BBR in a NA(ARO) message to | - | | indicate that the ownership of the proxy state on the | - | | backbone was transferred to another 6BBR, which is | - | | indicative of a movement of the device. The receiver of | - | | the NA is the device that has performed a registration | - | | that is now stale and it should clean up its state. | + | | instance due to time out of a lifetime, or a movement. | + | | The receiver of the NA is the device that has performed a | + | | registration that is now stale and it should clean up its | + | | state. | | | | | 6 | Duplicate Source Address: The address used as source of | | | the NS(ARO) conflicts with an existing registration. | | | | | 7 | Invalid Source Address: The address used as source of the | | | NS(ARO) is not a Link-Local address as prescribed by this | | | document. | | | | | 8 | Registered Address topologically incorrect: The address | | | being registered is not usable on this link, e.g. it is | | | not topologically correct | | | | | 9 | 6LBR Registry saturated: A new registration cannot be | | | accepted because the 6LBR Registry is saturated. This | | | code is used by 6LBRs instead of Status 2 when responding | - | | to a DAR/DAC exchange and passed on to the registering | - | | node by the 6LR. There is no point for the node to retry | + | | to a DAR/DAC exchange and passed on to the Registering | + | | Node by the 6LR. There is no point for the node to retry | | | this registration immediately via another 6LR, since the | | | problem is global to the network. The node may either | | | abandon that address, deregister other addresses first to | | | make room, or keep the address in TENTATIVE state and | | | retry later. | +-------+-----------------------------------------------------------+ Table 1: EARO Status +6.2. New 6LoWPAN capability Bits in the Capability Indication Option + + This specification defines a number of capability bits in the CIO + that was introduced by RFC 7400 [RFC7400]. + + Support for this specification is indicated by setting the "E" flag + in a CIO option. Routers that are capable of acting as 6LR, 6LBR and + 6BBR SHOULD set the L, B and P flags, respectively. + + Those flags are not mutually exclusive and if a router is capable of + multiple roles, it SHOULD set all the related flags. + + 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 = 1 |_____________________|L|B|P|E|G| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |_______________________________________________________________| + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Figure 2: New capability Bits L, B, P, E in the CIO + + Option Fields + + Type: 36 + + L: Node is a 6LR, it can take registrations. + + B: Node is a 6LBR. + + P: Node is a 6BBR, proxying for nodes on this link. + + E: This specification is supported and applied. + 7. Backward Compatibility 7.1. Discovering the capabilities of an ND peer 7.1.1. Using the E Flag in the CIO If the CIO is used in an ND message, then the "E" Flag MUST be set by the sending node if supports this specification. It is RECOMMENDED that a router that supports this specification indicates so with a CIO option, but this might not be practical if the link-layer MTU is too small. - If the registering node receives a CIO in a RA, then the setting of + If the Registering Node receives a CIO in a RA, then the setting of the E" Flag indicates whether or not this specification is supported. 7.1.2. Using the T Flag in the EARO One alternate way for a 6LN to discover the router's capabilities to first register a Link Local address, placing the same address in the Source and Target Address fields of the NS message, and setting the "T" Flag. The node may for instance register an address that is based on EUI-64. For such address, DAD is not required and using the SLLAO option in the NS is actually more amenable with existing ND @@ -687,54 +682,52 @@ A node that supports this specification MUST always use an EARO as a replacement to an ARO in its registration to a router. This is harmless since the "T" flag and TID field are reserved in RFC 6775 [RFC6775] are ignored by a legacy router. A router that supports this specification answers to an ARO with an ARO and to an EARO with an EARO. This specification changes the behavior of the peers in a registration flows. To enable backward compatibility, a node that registers to a router that is not known to support this specification - MUST behave as prescribed by RFC 6775 [RFC6775]. Once the router is - known to support this specification, the node MUST obey this - specification. + MUST behave as prescribed by RFC 6775. Once the router is known to + support this specification, the node MUST obey this specification. 7.2. Legacy 6LoWPAN Node - A legacy 6LN will use the registered address as source and will not + A legacy 6LN will use the Registered Address as source and will not use an EARO option. In order to be backward compatible, an updated - 6LR needs to accept that registration if it is valid per the - "Cryptographically Generated Addresses (CGA)" [RFC3972] - specification, and manage the binding cache accordingly. + 6LR needs to accept that registration if it is valid per the RFC 6775 + [RFC6775] specification, and manage the binding cache accordingly. - The main difference with RFC 3972 [RFC3972] is that DAR/DAC exchange - for DAD may be avoided for Link-Local addresses. Additionally, the - 6LR SHOULD use an EARO in the reply, and may use any of the Status - codes defined in this specification. + The main difference with RFC 6775 is that DAR/DAC exchange for DAD + may be avoided for Link-Local addresses. Additionally, the 6LR + SHOULD use an EARO in the reply, and may use any of the Status codes + defined in this specification. 7.3. Legacy 6LoWPAN Router The first registration by a an updated 6LN is for a Link-Local address, using that Link-Local address as source. A legacy 6LN will not makes a difference and accept -or reject- that registration as if the 6LN was a legacy node. An updated 6LN will always use an EARO option in the registration NS message, whereas a legacy 6LN will always areply with an ARO option in the NA message. So from that first registration, the updated 6LN can figure whether the 6LR supports this specification or not. When facing a legacy 6LR, an updated 6LN may attempt to find an alternate 6LR that is updated. In order to be backward compatible, based on the discovery that a 6LR is legacy, the 6LN needs to - fallback to legacy behavior and source the packet with the registered - address. + fallback to legacy behavior and source the packet with the Registered + Address. The main difference is that the updated 6LN SHOULD use an EARO in the request regardless of the type of 6LN, legacy or updated 7.4. Legacy 6LoWPAN Border Router With this specification, the DAR/DAC transports an EARO option as opposed to an ARO option. As described for the NS/NA exchange, devices that support this specification always use an EARO option and all the associated behavior. @@ -747,38 +740,41 @@ prevent a rogue access, either by means of physical or IP security on the Backbone Link and link layer cryptography on the LLN. This specification also expects that the LLN MAC provides secure unicast to/from the Backbone Router and secure Broadcast from the Backbone Router in a way that prevents tempering with or replaying the RA messages. This specification does not mandate any particular way for forming IPv6 addresses, but it recognizes that use of EUI-64 for forming the Interface ID in the Link-Local address prevents the usage of "SEcure - Neighbor Discovery (SEND)" [RFC3971] and CGA [RFC3972], and that of - address privacy techniques. This specification RECOMMENDS the use of - additional protection against address theft such as provided by - "Address Protected Neighbor Discovery for Low-power and Lossy - Networks" [I-D.ietf-6lo-ap-nd], which guarantees the ownership of the - OUID. + Neighbor Discovery (SEND)" [RFC3971] and "Cryptographically Generated + Addresses (CGA)" [RFC3972], and that of address privacy techniques, + such as recommended in "Privacy Considerations for IPv6 Adaptation- + Layer Mechanisms" [RFC8065]. This specification RECOMMENDS the use + of privacy techniques, and that of additional protection against + address theft such as provided by "Address Protected Neighbor + Discovery for Low-power and Lossy Networks" [I-D.ietf-6lo-ap-nd], + which guarantees the ownership of the Registered Address using a + cryptographic OUID. As indicated in section Section 2, this protocol does not aim at limiting the number of IPv6 addresses that a device can form, either. A host should be able to register any address that is topologically correct in the subnet(s) advertised by the 6LR/6LBR. On the other hand, the registration mechanism may be used by a rogue node to attack the 6LR or the 6LBR with a Denial-of-Service attack against the registry. It may also happen that the registry of a 6LR or a 6LBR is saturated and cannot take any more registration, which effectively denies the requesting a node the capability to use a new - address. In order to alleviate those concerns, Section 5.6 provides + address. In order to alleviate those concerns, Section 4.6 provides a number of recommendations that ensure that a stale registration is removed as soon as possible from the 6LR and 6LBR. In particular, this specification recommends that: o A node that ceases to use an address should attempt to deregister that address from all the 6LRs to which it is registered. The flow is propagated to the 6LBR when needed, and a sequence number is used to make sure that only the freshest command is acted upon. o The nodes should be configured with a Registration Lifetime that @@ -797,39 +793,39 @@ addresses if such can be recognized, e.g. from the way the IID is formed or because they are used over a much longer time span than other (privacy, shorter-lived) addresses. o Administrators should take great care to deploy adequate numbers of 6LR to cover the needs of the nodes in their range, so as to avoid a situation of starving nodes. It is expected that the 6LBR that serves a LLN is a more capable node then the average 6LR, but in a network condition where it may become saturated, a particular deployment should distribute the 6LBR functionality, for instance - by leveraging a high speed backbone and Backbone Routers to + by leveraging a high speed Backbone and Backbone Routers to aggregate multiple LLNs into a larger subnet. When the ownership of the OUID cannot be assessed, this specification limits the cases where the OUID and the TID are multicasted, and obfuscates them in responses to attempts to take over an address. The LLN nodes depend on the 6LBR and the 6BBR for their operation. A trust model must be put in place to ensure that the right devices are acting in these roles, so as to avoid threats such as black-holing, or bombing attack whereby an impersonated 6LBR would destroy state in the network by using the "Removed" Status code. 9. IANA Considerations IANA is requested to create a new subregistry for "ARO Flags" under the "Internet Control Message Protocol version 6 (ICMPv6) Parameters". This specification defines 8 positions, bit 0 to bit 7, - and assigns bit 7 for the "T" flag in Section 6.2. The policy is + and assigns bit 7 for the "T" flag in Section 6.1. The policy is "IETF Review" or "IESG Approval" [RFC5226]. The initial content of the registry is as shown in Table 2. New subregistry for ARO Flags under the "Internet Control Message Protocol version 6 (ICMPv6) Parameters" +------------+--------------+-----------+ | ARO Status | Description | Document | +------------+--------------+-----------+ | 0..6 | Unassigned | | @@ -884,24 +880,20 @@ 10. Acknowledgments Kudos to Eric Levy-Abegnoli who designed the First Hop Security infrastructure at Cisco. 11. References 11.1. Normative References - [I-D.ietf-6lo-backbone-router] - Thubert, P., "IPv6 Backbone Router", draft-ietf-6lo- - backbone-router-03 (work in progress), January 2017. - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, @@ -941,36 +933,29 @@ Chakrabarti, S., Nordmark, E., Thubert, P., and M. Wasserman, "IPv6 Neighbor Discovery Optimizations for Wired and Wireless Networks", draft-chakrabarti-nordmark- 6man-efficient-nd-07 (work in progress), February 2015. [I-D.delcarpio-6lo-wlanah] Vega, L., Robles, I., and R. Morabito, "IPv6 over 802.11ah", draft-delcarpio-6lo-wlanah-01 (work in progress), October 2015. - [I-D.ietf-6lo-6lobac] - Lynn, K., Martocci, J., Neilson, C., and S. Donaldson, - "Transmission of IPv6 over MS/TP Networks", draft-ietf- - 6lo-6lobac-08 (work in progress), March 2017. - [I-D.ietf-6lo-ap-nd] Sarikaya, B., Thubert, P., and M. Sethi, "Address Protected Neighbor Discovery for Low-power and Lossy Networks", draft-ietf-6lo-ap-nd-00 (work in progress), November 2016. - [I-D.ietf-6lo-dect-ule] - Mariager, P., Petersen, J., Shelby, Z., Logt, M., and D. - Barthel, "Transmission of IPv6 Packets over DECT Ultra Low - Energy", draft-ietf-6lo-dect-ule-09 (work in progress), - December 2016. + [I-D.ietf-6lo-backbone-router] + Thubert, P., "IPv6 Backbone Router", draft-ietf-6lo- + backbone-router-03 (work in progress), January 2017. [I-D.ietf-6lo-nfc] Choi, Y., Hong, Y., Youn, J., Kim, D., and J. Choi, "Transmission of IPv6 Packets over Near Field Communication", draft-ietf-6lo-nfc-06 (work in progress), March 2017. [I-D.ietf-6tisch-architecture] Thubert, P., "An Architecture for IPv6 over the TSCH mode of IEEE 802.15.4", draft-ietf-6tisch-architecture-11 (work @@ -1057,20 +1042,35 @@ [RFC7668] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B., Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015, . [RFC7934] Colitti, L., Cerf, V., Cheshire, S., and D. Schinazi, "Host Address Availability Recommendations", BCP 204, RFC 7934, DOI 10.17487/RFC7934, July 2016, . + [RFC8065] Thaler, D., "Privacy Considerations for IPv6 Adaptation- + Layer Mechanisms", RFC 8065, DOI 10.17487/RFC8065, + February 2017, . + + [RFC8105] Mariager, P., Petersen, J., Ed., Shelby, Z., Van de Logt, + M., and D. Barthel, "Transmission of IPv6 Packets over + Digital Enhanced Cordless Telecommunications (DECT) Ultra + Low Energy (ULE)", RFC 8105, DOI 10.17487/RFC8105, May + 2017, . + + [RFC8163] Lynn, K., Ed., Martocci, J., Neilson, C., and S. + Donaldson, "Transmission of IPv6 over Master-Slave/Token- + Passing (MS/TP) Networks", RFC 8163, DOI 10.17487/RFC8163, + May 2017, . + 11.3. External Informative References [IEEEstd802154] IEEE, "IEEE Standard for Low-Rate Wireless Networks", IEEE Standard 802.15.4, DOI 10.1109/IEEESTD.2016.7460875, . Appendix A. Applicability and Requirements Served This specification extends 6LoWPAN ND to sequence the registration @@ -1089,21 +1089,21 @@ implement the 6TiSCH architecture and serves the requirements listed in Appendix B.2. The term LLN is used loosely in this specification to cover multiple types of WLANs and WPANs, including Low-Power Wi-Fi, BLUETOOTH(R) Low Energy, IEEE Std.802.11AH and IEEE Std.802.15.4 wireless meshes, so as to address the requirements discussed in Appendix B.3 This specification can be used by any wireless node to associate at Layer-3 with a 6BBR and register its IPv6 addresses to obtain routing - services including proxy-ND operations over the backbone, effectively + services including proxy-ND operations over the Backbone, effectively providing a solution to the requirements expressed in Appendix B.4. "Efficiency aware IPv6 Neighbor Discovery Optimizations" [I-D.chakrabarti-nordmark-6man-efficient-nd] suggests that 6LoWPAN ND [RFC6775] can be extended to other types of links beyond IEEE Std. 802.15.4 for which it was defined. The registration technique is beneficial when the Link-Layer technique used to carry IPv6 multicast packets is not sufficiently efficient in terms of delivery ratio or energy consumption in the end devices, in particular to enable energy-constrained sleeping nodes. The value of such extension is @@ -1187,24 +1187,24 @@ burden of supporting the Multicast Listener Discovery Version 2 [RFC3810] (MLDv2) for IPv6. B.3. Requirements Related to the Variety of Low-Power Link types 6LoWPAN ND [RFC6775] was defined with a focus on IEEE Std.802.15.4 and in particular the capability to derive a unique Identifier from a globally unique MAC-64 address. At this point, the 6lo Working Group is extending the 6LoWPAN Header Compression (HC) [RFC6282] technique to other link types ITU-T G.9959 [RFC7428], Master-Slave/Token- - Passing [I-D.ietf-6lo-6lobac], DECT Ultra Low Energy - [I-D.ietf-6lo-dect-ule], Near Field Communication [I-D.ietf-6lo-nfc], - IEEE Std.802.11ah [I-D.delcarpio-6lo-wlanah], as well as IEEE1901.2 - Narrowband Powerline Communication Networks + Passing [RFC8163], DECT Ultra Low Energy [RFC8105], Near Field + Communication [I-D.ietf-6lo-nfc], IEEE Std. 802.11ah + [I-D.delcarpio-6lo-wlanah], as well as IEEE1901.2 Narrowband + Powerline Communication Networks [I-D.popa-6lo-6loplc-ipv6-over-ieee19012-networks] and BLUETOOTH(R) Low Energy [RFC7668]. Related requirements are: Req3.1: The support of the registration mechanism SHOULD be extended to more LLN links than IEEE Std.802.15.4, matching at least the LLN links for which an "IPv6 over foo" specification exists, as well as Low-Power Wi-Fi. @@ -1216,37 +1216,37 @@ Req3.3: The Address Registration Option used in the ND registration SHOULD be extended to carry the relevant forms of unique Identifier. Req3.4: The Neighbour Discovery should specify the formation of a site-local address that follows the security recommendations from [RFC7217]. B.4. Requirements Related to Proxy Operations Duty-cycled devices may not be able to answer themselves to a lookup - from a node that uses classical ND on a backbone and may need a + from a node that uses classical ND on a Backbone and may need a proxy. Additionally, the duty-cycled device may need to rely on the 6LBR to perform registration to the 6BBR. The ND registration method SHOULD defend the addresses of duty-cycled devices that are sleeping most of the time and not capable to defend their own Addresses. Related requirements are: Req4.1: The registration mechanism SHOULD enable a third party to proxy register an Address on behalf of a 6LoWPAN node that may be sleeping or located deeper in an LLN mesh. Req4.2: The registration mechanism SHOULD be applicable to a duty- cycled device regardless of the link type, and enable a 6BBR to - operate as a proxy to defend the registered Addresses on its behalf. + operate as a proxy to defend the Registered Addresses on its behalf. Req4.3: The registration mechanism SHOULD enable long sleep durations, in the order of multiple days to a month. B.5. Requirements Related to Security In order to guarantee the operations of the 6LoWPAN ND flows, the spoofing of the 6LR, 6LBR and 6BBRs roles should be avoided. Once a node successfully registers an address, 6LoWPAN ND should provide energy-efficient means for the 6LBR to protect that ownership even