6lo Working Group L. Iannone Internet-Draft D. Lou Intended status: Standards Track Huawei Expires: 25 December 2025 A. Rashid Politecnico di Bari 23 June 2025 Generic Address Assignment Option for 6LoWPAN Neighbor Discovery draft-ietf-6lo-nd-gaao-04 Abstract This document specifies a new extension to the IPv6 Neighbor Discovery in Low Power and Lossy Networks, enabling a node to request to be assigned an address or a prefix from neighbor routers. Such mechanism allows to algorithmically assign addresses and prefixes to nodes in a 6LoWPAN deployment. 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 https://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 25 December 2025. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. Iannone, et al. Expires 25 December 2025 [Page 1] Internet-Draft GAAO June 2025 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Requirements Notation . . . . . . . . . . . . . . . . . . 4 2.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Definition of Terms . . . . . . . . . . . . . . . . . . . 5 3. Algorithmically Assigned Addresses and Prefixes . . . . . . . 5 4. Generic Address Assignment Option . . . . . . . . . . . . . . 6 5. Messages Sequence and Processing . . . . . . . . . . . . . . 9 5.1. Request Phase . . . . . . . . . . . . . . . . . . . . . . 9 5.2. Optional Ratification Phase . . . . . . . . . . . . . . . 10 5.3. Message Exchange Optimization . . . . . . . . . . . . . . 11 5.4. Error Conditions . . . . . . . . . . . . . . . . . . . . 12 6. Signaling GAAO Support . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7.1. IPv6 ND Option Types . . . . . . . . . . . . . . . . . . 14 7.2. 6LoWPAN Capability Bits . . . . . . . . . . . . . . . . . 14 7.3. GAAO Error code . . . . . . . . . . . . . . . . . . . . . 14 7.4. Address Assignment Function Registry . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 16 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Normative References . . . . . . . . . . . . . . . . . . . . . 16 Informative References . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 1. Introduction Low Power and Lossy Networks (LLNs) have adapted the design of Internet protocols to more constrained environments, by taking into consideration of energy saving, limited memory capacity, and duty cycling of the LLN devices, as well as low-power lossy transmissions. Since the wireless interface is a major energy drain, protocols aiming at being deployed over LLN must be designed in such a way to reduce as much as possible transmissions, allowing to turn off the radio interface or put the interface or the whole node in the sleeping mode. Iannone, et al. Expires 25 December 2025 [Page 2] Internet-Draft GAAO June 2025 IPv6 Neighbor Discovery has been also adapted to the LLN environment in [RFC6775], later updated by [RFC8505], [RFC8929], and [RFC9010]. The target being to design protocols that reduce energy consumption, especially in LLNs, though in general their design could be applied in any context targeting lowering carbon emissions. In particular, interface address assignment relies on address auto-configuration [RFC4862], since the use of Dynamic Host Configuration Protocol (DHCP [RFC8415]) is not adapted, from an energy and bandwidth perspective, to LLN deployments. Indeed, LLN environments aim at avoiding as much as possible asynchronous multicast operations, because that would keep nodes awake and listening. Furthermore, it is also preferable to reduce as much as possible the number of nodes involved in control plane operations, because of energy and bandwidth constraints typical of LLN. DHCP can still be used in Internet-of-Things (IoT) deployments where energy and bandwidth are not an issue. To avoid multicast operations and to limit the number of nodes involved in address assignment in LLN, mechanisms to register self- generated addresses have been designed ([RFC6775], [I-D.ietf-6lo-prefix-registration], [RFC8505], [RFC9685]). Recent use cases show, however, that there are some advantages in assigning addresses in an algorithmically managed way. In particular, in some scenarios, routing and forwarding can be simplified ([RFC9453], [I-D.ietf-6lo-path-aware-semantic-addressing], [SHENOY21], [BLESS22], [RIDOUX05]), hence reducing the power consumption and memory footprint. Algorithmic address assignment has its own pros and cons, as well as deployment requirements. However, they have the common benefit of being easily distributed. In other words, it is not necessary to have a centralized approach, like DHCP, rather address assignment is distributed by construction and a node can obtain an address from one of its neighbors who simply runs a distributed algorithm. This situation highlights an existing gap that this document tries to fill: 6LoWPAN nodes have no means to directly request an address (or address prefix) from routers that are their direct neighbors. Currently, either auto-configuration is used, or DHCP has to be deployed. The former is energy efficient, but makes it hard to implement solutions like [I-D.ietf-6lo-path-aware-semantic-addressing], [SHENOY21], [BLESS22], and [RIDOUX05]. The latter, on the opposite, allows the use of sophisticated assignment algorithms, but remains inefficient from an energy and bandwidth consumption viewpoint. This document proposes a new Neighbor Discovery Option, namely the Generic Address Assignment Option (GAAO), in order for a node to issue an address or prefix request to neighboring routers. GAAO Iannone, et al. Expires 25 December 2025 [Page 3] Internet-Draft GAAO June 2025 complements the Extended Address Registration Option (EARO), defined in [RFC8505], further extended in [I-D.ietf-6lo-prefix-registration] and [RFC9685]. 2. Terminology 2.1. Requirements Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2.2. Acronyms This document assumes familiarity with the terminology defined in [RFC6775] and [RFC8505]. In particular for the following acronyms: 6CIO: Capability Indication Option 6LBR: 6LoWPAN Border Router 6LN: 6LoWPAN Node 6LoWPAN: IPv6 over Low-Power Wireless Personal Area Network 6LR: 6LoWPAN Router AAF: Address Assignment Function ARO: Address Registration Option EARO: Extended Address Registration Option GAAO: Generic Address Assignment Option IID: Interface IDentifier LLN: Low-Power and Lossy Network NA: Neighbor Advertisement ND: Neighbor Discovery NS: Neighbor Solicitation Pfxlen: Prefix Length Iannone, et al. Expires 25 December 2025 [Page 4] Internet-Draft GAAO June 2025 RA: Router Advertisement RS: Router Solicitation SLAAC: State-Less Address Auto-Configuration SLLAO: Source Link-Layer Address Option TLLAO: Target Link-Layer Address Option 2.3. Definition of Terms Address Assignment Function (AAF): The Address Assignment Function (AAF) is an implementation of the algorithm used by 6LRs to assign an address/prefix to requesting nodes. In order to avoid addressing issues, only one single AAF is used in a deployment. GAAO: Generic Address Assignment Option defined in the present document (Section 4). 3. Algorithmically Assigned Addresses and Prefixes The IPv6 address assignment model inside a local domain is based on randomly assigned Interface IDentifier (IID), either done in a centralized way using DHCP, which can guarantee no address collision, or by decentralized State-Less Address Auto-Configuration (SLAAC [RFC4862]), which needs additional mechanisms to ensure the uniqueness of addresses. However, there is a third approach for address assignment, which is distributed and collision-free: algorithmically generated addresses (e.g., [SHENOY21], [BLESS22], [RIDOUX05], [ERIKSSON04]). The main idea is to use an Address Assignment Function (AAF) to assign addresses and prefixes to nodes joining a network. All nodes, 6LNs, 6LRs, and 6LBRs, MUST use the same AAF in the same network instance. Each node acquiring an address firstly needs to select a neighbor 6LR by choosing among the nodes that replied with a Router Advertisement (RA) after an initial Router Solicitation (RS), as defined in [RFC6775]. Then, the node explicitly requests an address (or prefix) to the selected 6LR. Depending on the underlying technology and algorithm used, the node may optionally ratify its usage. The high-level sequence of actions is depicted in Figure 1. Iannone, et al. Expires 25 December 2025 [Page 5] Internet-Draft GAAO June 2025 STEP 6LN 6LR | | 1. | Address Request | \ | --------------------> | \ | | + Request Phase 2. | Address Offer | / | <-------------------- | / | | 3. | Address Acceptation | \ | --------------------> | \ | | + Optional Ratification Phase 4. | Address Confirmation | / | <-------------------- | / | | Figure 1: Address/Prefix assignment sequence. The optional ratification phase (namely step 3 and 4), is implemented by using the address registration procedure defined in [RFC8505], [RFC9685], or [I-D.ietf-6lo-prefix-registration]. Basically, it uses an EARO and SLLAO messages to register an address, which in this case is not a self-generated address. However, in order to issue the initial request, namely steps 1 and 2, a new Generic Address Assignment Option (GAAO) is required and proposed, since no existing mechanism can be readily used for this purpose. In the remaining of this document, the format of this option is firstly defined (Section 4), followed by a revised Address/Prefix assignment messages sequence and processing (Section 5). 4. Generic Address Assignment Option In order for a node to request the assignment of an address or prefix, the Generic Address Assignment Option (GAAO) message is used. The format of the GAAO message is shown in Figure 2. Iannone, et al. Expires 25 December 2025 [Page 6] Internet-Draft GAAO June 2025 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 | Status/PfxLen | Opaque | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R|C| Reserved | AAF | Assignment Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Registration Ownership Verifier (ROVR) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Address/Prefix | | (128 bits) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Generic Address Assignment Option format. Generic Address Assignment Option Fields: Type: TBD Length: 8-bit unsigned integer. The length of the option in units of 8 bytes. This field is set to 1 plus the size of the ROVR field when the option is used in NS messages. It is augmented by 2 (16 bytes) when this option is used in NA messages because the assigned address/prefix is appended to the option. Status/PfxLen: 8-bits unsigned integer. This field has two purposes. It indicates the Prefix Length of the assigned address if the assignment is successful or an error code otherwise. * On success, the returned GAAO message MUST have 16 bytes of the assigned address/prefix appended to it, which means that the Length field will increased by 2 (cf. Length field). * In case of failure, when no address/prefix is returned, this field indicates an error code (See table 1 in [RFC8505] and Section 5.4 for error codes). In this case, the returned GAAO message will not have any address/prefix appended to it and the Length field has not been increased. A returning GAAO with the same length as the one sent indicates error condition, whose code MUST be is indicated in this field. This field MUST be set to 0 on transmission and ignored on reception in NS messages. Iannone, et al. Expires 25 December 2025 [Page 7] Internet-Draft GAAO June 2025 Opaque: As defined in [RFC8505], where values different from 0 are interpreted as an abstract index that is used to decide from which routing topology the address is expected to be assigned. R: Ratification requested. It MUST be initialized to 0 in NS(GAAO) messages by the requester and MUST be ignored by the receiver. The 6LR/6LBR replying to the request with an NA(GAAO) message MAY set this bit to indicate that it requests a confirmation that the address/prefix is accepted and will be used. When the requester receives an NA(GAAO) message with this bit set, it MUST explicitly register the received address/prefix to the same 6LR using the procedures defined in [RFC8505], [I-D.ietf-6lo-prefix-registration], and [RFC9685], according to the type of the assigned address/prefix. C: Crypto-ID used for ROVR as defined [RFC8928] and [I-D.ietf-6lo-updating-rfc-8928]. This flag MUST be set when the ROVR field contains a Crypto-ID. Reserved: This field is reserved for future use. It MUST be initialized to 0 by the sender and MUST be ignored by the receiver. Address Assignment Function(AAF): 4-bit unsigned integer. Describe the Address Assignment Function (AAF), i.e. the algorithm, used to assign the address/prefix. 0 is a special value indicating that the field is not used. On request in an NS message, it is RECOMMENDED to set this field to 0 to indicate there is no preference on how the address is assigned. However, a 6LN MAY use a value different from 0, meaning that it is requested to use a specific known AAF to assign the address/prefix (see also Section 5.4). Section 7.4 describes possible values of this field. Assignment Lifetime: 16-bit unsigned integer, expressed in minutes. In an NS message, the field expresses a desired lifetime. It MAY be set to zero in the NS(GAAO) message, indicating no particular desired lifetime. In NA(GAAO) messages it expresses the granted maximum lifetime. A node MUST NOT use the address/prefix after expiration of the lifetime. Address/prefix lifetime SHOULD be configurable according to the AAF in use and as mitigation of certain attacks (see Section 8). ROVR: As defined in [RFC8505] and extended in [RFC8928] and [I-D.ietf-6lo-updating-rfc-8928]. Address/Prefix: 128 bits address or prefix returned in a NA(GAAO) Iannone, et al. Expires 25 December 2025 [Page 8] Internet-Draft GAAO June 2025 message. This field MUST NOT be present in NS(GAAO) request messages and in NA(GAAO) messages when an error occurs. This field MUST be present in NA(GAAO) messages that return a successful address/prefix allocation. 5. Messages Sequence and Processing When a node bootstraps, it typically does multicast a Routing Solicitation (RS) and receives one or more unicast Routing Advertisement (RA) messages from neighbor 6LRs. The node MAY choose one or more 6LRs from which to request address(es) or prefix(es). A node MAY perform an address request at any time, not necessarily at boot time using Neighbor Solicitation (NS) and Neighbor Advertisement (NA) messages. 5.1. Request Phase When the node requests an address, the node will go through the following steps: 1. The node will issue an NS(GAAO) request for an address assignment. In this initial request, GAAO MUST have a length equal to ROVR's length as a multiple of 8 bytes plus one (no 16-bytes address appended), Status/PfxLen field set to 0. Opaque, ROVR, and C-flag is set according to local the configuration. The R-flag is set to zero. The AAF field SHOULD be set to zero unless by configuration there is a preference for the assignment algorithm. The address Assignment Lifetime field MAY be set to the desired lifetime, or zero otherwise. 2. Assuming no errors occur, the node will receive an NA(GAAO) message with a length increased by two, compared to the corresponding NS(GAAO) message, because of the presence of the address/prefix field. All fields have been copied back except for: * Pfxlen: Now indicating the length of the prefix. * R: The R bit is set if the 6LR requests a ratification via a registration procedure. * AAF: It is the algorithm, used to assign the address/prefix. If the node is a 6LR it MUST use the same AAF to generate addresses/prefixes to requesting neighbor nodes. * Assignment Lifetime: The maximum lifetime of the assigned address/prefix. Iannone, et al. Expires 25 December 2025 [Page 9] Internet-Draft GAAO June 2025 The message sequence is depicted in Figure 3. STEP 6LN 6LR | | 1. | ---- NS with Address/Prefix Request ---> | | (GAAO) | | | 2. | <--- NA with Proposed Address/Prefix --- | | (GAAO) | | | Figure 3: Address/Prefix assignment with GAAO message sequence and no confirmation request. 5.2. Optional Ratification Phase Depending on the algorithm in use and the underlying technology the address assignment procedure terminates after these two messages. This may be sufficient for instance in deployments where the link layer offers reliable packet delivery. The use of this option is done by configuration. Documents defining Address Allocation Function MUST explicitly state whether this phase remains optional or is mandatory due to factors specific to the proposed algorithm. If the R-flag is set, to ratify the acceptance and usage of the proposed address/prefix received in the NA(GAAO) message, the 6LN MUST register with the obtained address by following the procedures in [RFC8505], [RFC9685], or [I-D.ietf-6lo-prefix-registration] depending on the type of address. When setting the R-flag, and as for [RFC4861], the 6LR is expect to receive a registration within RETRANS_TIMER multiplied by MAX_UNICAST_SOLICIT. If no registration is received within this amount of time the 6LR will consider that address/prefix is not in use by the requesting 6LN. The complete sequence of actions is depicted in Figure 4. Iannone, et al. Expires 25 December 2025 [Page 10] Internet-Draft GAAO June 2025 STEP 6LN 6LR | | 1. | ------ NS with Address/Prefix Request -----> | | (GAAO) | | | 2. | <------ NA with Proposed Address/Prefix ---- | | (GAAO) | | | 3. | --- NS with Address/Prefix Registration ---> | | (EARO + SLLAO) | | | ... Procedure According to [RFC8505], [RFC9685], or [I-D.ietf-6lo-prefix-registration] depending on the type of address. ... | | 4. | <--- NA with Address/Prefix Registration --- | | (EARO with Status + SLLAO) | | | Figure 4: Address/Prefix Assignment with GAAO Message sequence. The specifications in [RFC8505], [RFC9685], and [I-D.ietf-6lo-prefix-registration], define how nodes keep address/ prefix registering state so to maintain addressing in case of reboot. When needed, in order to use this feature with GAAO, after reboot the optional ratification phase MUST be used to perform an explicit registration. However, when using GAAO, and when preforming the re- registering, if a "Registration Refresh Request" or "Invalid Registration" status value is returned, the node MUST restart from the top with the initial request phase. 5.3. Message Exchange Optimization Prefix/address requests utilize NS/NA transactions, similar to prefix/address registration. To minimize the number of transactions, GAAO MAY be used at the same time like the EARO option. In other words GAAO can be piggybacked on other transactions, hence it does not necessarily introduce additional NS/NA transactions. For instance, it can be piggybacked in an link-layer address registration, as shown in Figure 5. In this case the returning NA(GAAO+EARO) will contain an address directly appended in GAAO, namely the offered prefix/address. Iannone, et al. Expires 25 December 2025 [Page 11] Internet-Draft GAAO June 2025 STEP 6LN 6LR | | 1. | ----- NS with Address Registration ----> | | (EARO + SLLAO + GAAO) | | | 2. | <---- NA with Address Registration ---- | | (EARO with Status + SLLAO + GAAO) | | | Figure 5: Message sequence when GAAO is piggybacked on a link-layer registration transaction. When prefix/address request is performed at boot time, the GAAO request MAY be appended as an option of the first RS message, implicitly signaling that the node sending the RS message supports the specifications in the present document. In the same way, the responding routers that support this document MUST send back a prefix/address offer in a GAAO appended to the returning RA message, as depicted in Figure 6. STEP 6LN 6LR | | 1. | ---------- Router Solicitation --------> | | (SLLAO + GAAO) | | | 2. | <-------- Router Advertisement --------- | | (PIO + 6CO + ABRO + SLLAO + GAAO) | | | Figure 6: Message sequence when GAAO is used with the RS/RA transaction. 6LRs that do not support GAAO will simply ignore the option, and the corresponding RA, which will not include a GAAO, implicitly signaling that the feature is not supported. 5.4. Error Conditions GAAO uses error codes defined in [RFC6775] and [RFC8505], revised in [RFC9010]. This specification introduces a new status code when the AAF in GAAO in an NS message is not in use in the 6LoWPAN network, as follows (see also Section 7): AAF Not Used: The AAF in GAAO in the NS message is not in use in the 6LoWPAN network. Iannone, et al. Expires 25 December 2025 [Page 12] Internet-Draft GAAO June 2025 This status MUST be used when a node requesting an address/prefix did put an AAF value, in the corresponding field, which is not in use in the 6LoWPAN network. When the node receives this status back it SHOULD perform one of the following actions: * Re-issue the same request without specifying an AAF. Meaning set the AAF field to 0. The 6LR will return the AAF in use in the 6LoWPAN network and employed to generate the returned address/ prefix. If the requesting node does not support the returned AAF it does not participate in the AAF-based 6LoWPAN network and does not use the proposed address/prefix. * Re-issue the same request with a different AAF. The 6LoWPAN network is not using the requested AAF but may be using a different one. Note that such an approach may lead to repeated requests that may consume bandwidth and energy. * Do nothing and do not participate in the AAF-based 6LoWPAN network. The action to be used is selected by configuration. When nodes fail to participate in the AAF-based 6LoWPAN network they MAY still use a different mechanism (e.g., [RFC8505]) to configure addresses. 6. Signaling GAAO Support This specification defines one new capability bit for use in the 6CIO as defined by [RFC7400] ("6LoWPAN-GHC: Generic Header Compression for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)"), for use in IPv6 ND messages. A 6LoWPAN node that supports this specification MUST set the M flag. 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 | Reserved |X|A|D|L|B|P|E|G| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |M| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: New GAAO Capability Bit in the 6CIO. M: The node supports managed addresses via the Generic Address Assignment Capability. Iannone, et al. Expires 25 December 2025 [Page 13] Internet-Draft GAAO June 2025 7. IANA Considerations This section provides guidance to the Internet Assigned Numbers Authority (IANA) regarding registration of values related to the GAAO specification, in accordance with BCP 26 [RFC8126]. 7.1. IPv6 ND Option Types IANA is requested to make an addition to the "IPv6 Neighbor Discovery Option Formats" registry under the heading "Internet Control Message Protocol version 6 (ICMPv6) Parameters" as indicated in Table 1: +================+===================================+===========+ | Type | Description | Reference | +================+===================================+===========+ | 43 (Suggested) | Generic Address Assignment Option | [This | | | | Document] | +----------------+-----------------------------------+-----------+ Table 1: New Generic Address Assignment Option. 7.2. 6LoWPAN Capability Bits IANA is requested to make an addition to the "6LoWPAN Capability Bits" registry under the registry group "Internet Control Message Protocol version 6 (ICMPv6) Parameters" as indicated in Table 2: +================+============================+===========+ | Bit | Description | Reference | +================+============================+===========+ | 16 (Suggested) | Generic Address Assignment | [This | | | Capability (M) Flag | Document] | +----------------+----------------------------+-----------+ Table 2: New 6LoWPAN Capability Bit. 7.3. GAAO Error code IANA is requested to make an addition to the "Address Registration Option Status Values" registry under the registry group "Internet Control Message Protocol version 6 (ICMPv6) Parameters" as indicated in Table 3: Iannone, et al. Expires 25 December 2025 [Page 14] Internet-Draft GAAO June 2025 +================+==============+=================+ | Value | Description | Reference | +================+==============+=================+ | 13 (Suggested) | AAF Not Used | [This Document] | +----------------+--------------+-----------------+ Table 3: New address registration option value. 7.4. Address Assignment Function Registry IANA is asked to create a registry group named "Generic Address Assignment Option". Such registry group should be populated with a one-octet registry named "Address Assignment Function" and used to identify the used AAF used. The registry is populated as shown in Table 4: +=========+================================+===========+ | Value | AAF Name | Reference | +=========+================================+===========+ | 0x0 | No AAF. This can be used only | [This | | | in NS message to indicate that | Document] | | | no specific AAF is demanded. | | +---------+--------------------------------+-----------+ | 0x1-0xE | Un-assigned | | +---------+--------------------------------+-----------+ | 0xF | Experimental Use. Used for | [This | | | experimental purposes during | Document] | | | implementation of new AAFs. | | +---------+--------------------------------+-----------+ Table 4: Allocation Function sub-registry Values can be assigned by IANA on a "First Come, First Served" basis according to [RFC8126]. 8. Security Considerations This document extends [RFC8505], which already extended [RFC6775], as such the security considerations of both documents apply to this specification. In particular, the link layer SHOULD provide sufficient protection to prevent potential attacks. Recommendations listed in Section 7 of [RFC8505] SHOULD be applied as well to this specification. Depending on the Assignment Function in use, the number of available addresses may encounter limitations. A rouge node may leverage on this knowledge to carry out address exhaustion attacks by Iannone, et al. Expires 25 December 2025 [Page 15] Internet-Draft GAAO June 2025 impersonating different nodes and performing multiple requests. To mitigate such risks the reccomendation about the lifetime and number of addresses per node described in Section 7 of [RFC8505] remain valid. Acknowledgements This document received many comments and help from community people. The authors would like to thank all of them. Thanks as well to Joel Halpern (GENART) and Brian Haberman (INTDIR) for their reviews that helpend to spot overlooked points in the definition of the GAAO mechanism. References Normative References [I-D.ietf-6lo-prefix-registration] Thubert, P., "IPv6 Neighbor Discovery Prefix Registration", Work in Progress, Internet-Draft, draft- ietf-6lo-prefix-registration-13, 6 June 2025, . [I-D.ietf-6lo-updating-rfc-8928] Thubert, P. and A. Rashid, "Fixing the C-Flag in EARO", Work in Progress, Internet-Draft, draft-ietf-6lo-updating- rfc-8928-04, 19 May 2025, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, DOI 10.17487/RFC4862, September 2007, . Iannone, et al. Expires 25 December 2025 [Page 16] Internet-Draft GAAO June 2025 [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. Bormann, "Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC 6775, DOI 10.17487/RFC6775, November 2012, . [RFC7400] Bormann, C., "6LoWPAN-GHC: Generic Header Compression for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC 7400, DOI 10.17487/RFC7400, November 2014, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. Perkins, "Registration Extensions for IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, . [RFC8928] Thubert, P., Ed., Sarikaya, B., Sethi, M., and R. Struik, "Address-Protected Neighbor Discovery for Low-Power and Lossy Networks", RFC 8928, DOI 10.17487/RFC8928, November 2020, . [RFC9010] Thubert, P., Ed. and M. Richardson, "Routing for RPL (Routing Protocol for Low-Power and Lossy Networks) Leaves", RFC 9010, DOI 10.17487/RFC9010, April 2021, . [RFC9685] Thubert, P., Ed., "Listener Subscription for IPv6 Neighbor Discovery Multicast and Anycast Addresses", RFC 9685, DOI 10.17487/RFC9685, November 2024, . Informative References Iannone, et al. Expires 25 December 2025 [Page 17] Internet-Draft GAAO June 2025 [BLESS22] Bless, R., Zitterbart, M., Despotovic, Z., and A. Hecker, "KIRA: Distributed Scalable ID-based Routing with Fast Forwarding", 2022 IFIP Networking Conference (IFIP Networking) pp. 1-9, DOI 10.23919/ifipnetworking55013.2022.9829816, June 2022, . [ERIKSSON04] Eriksson, J., Faloutsos, M., and S. Krishnamurthy, "Scalable ad hoc routing: the case for dynamic addressing", IEEE INFOCOM 2004 vol. 2, pp. 1108-1119, DOI 10.1109/infcom.2004.1356997, February 2005, . [I-D.ietf-6lo-path-aware-semantic-addressing] Iannone, L., Li, G., Lou, D., Liu, P., and P. Thubert, "Path-Aware Semantic Addressing (PASA) for Low power and Lossy Networks", Work in Progress, Internet-Draft, draft- ietf-6lo-path-aware-semantic-addressing-11, 3 March 2025, . [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., Richardson, M., Jiang, S., Lemon, T., and T. Winters, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 8415, DOI 10.17487/RFC8415, November 2018, . [RFC8929] Thubert, P., Ed., Perkins, C.E., and E. Levy-Abegnoli, "IPv6 Backbone Router", RFC 8929, DOI 10.17487/RFC8929, November 2020, . [RFC9453] Hong, Y., Gomez, C., Choi, Y., Sangi, A., and S. Chakrabarti, "Applicability and Use Cases for IPv6 over Networks of Resource-constrained Nodes (6lo)", RFC 9453, DOI 10.17487/RFC9453, September 2023, . [RIDOUX05] Ridoux, J., Fladenmuller, A., Viniotis, Y., and K. Salamatian, "Trellis-Based Virtual Regular Addressing Structures in Self-organized Networks", Lecture Notes in Computer Science pp. 511-522, DOI 10.1007/11422778_41, 2005, . [SHENOY21] Shenoy, N., Chandraiah, S., and P. Willis, "A Structured Approach to Routing in the Internet", 2021 IEEE 22nd International Conference on High Performance Switching and Iannone, et al. Expires 25 December 2025 [Page 18] Internet-Draft GAAO June 2025 Routing (HPSR) pp. 1-6, DOI 10.1109/hpsr52026.2021.9481818, June 2021, . Authors' Addresses Luigi Iannone Huawei Technologies France S.A.S.U. 18, Quai du Point du Jour 92100 Boulogne-Billancourt France Email: luigi.iannone@huawei.com David Lou Huawei Technologies Duesseldorf GmbH Riesstrasse 25 80992 Munich Germany Email: zhe.lou@huawei.com Adnan Rashid Politecnico di Bari Via Edoardo Orabona 4 70126 Bari Italy Email: adnan.rashid@poliba.it Iannone, et al. Expires 25 December 2025 [Page 19]