LISP Working Group D. Saucez, Ed. Internet-Draft Inria Obsoletes: 8111 (if approved) L. Iannone, Ed. Intended status: Standards Track Huawei Expires: 24 April 2025 21 October 2024 Locator/ID Separation Protocol Delegated Database Tree (LISP-DDT) draft-saucez-8111bis-00 Abstract This document describes the Locator/ID Separation Protocol Delegated Database Tree (LISP-DDT), a hierarchical distributed database that embodies the delegation of authority to provide mappings from LISP Endpoint Identifiers (EIDs) to Routing Locators (RLOCs). It is a statically defined distribution of the EID namespace among a set of LISP-speaking servers called "DDT Nodes". Each DDT Node is configured as "authoritative" for one or more EID-prefixes, along with the set of RLOCs for Map-Servers or "child" DDT Nodes to which more-specific EID-prefixes are delegated. This document obsoletes RFC 8111. 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 24 April 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Saucez & Iannone Expires 24 April 2025 [Page 1] Internet-Draft LISP-DDT October 2024 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 3. Definitions of Terms . . . . . . . . . . . . . . . . . . . . 5 4. Database Organization . . . . . . . . . . . . . . . . . . . . 7 4.1. XEID-Prefixes . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Structure of the DDT Database . . . . . . . . . . . . . . 8 4.3. Configuring Prefix Delegation . . . . . . . . . . . . . . 8 4.3.1. The Root DDT Node . . . . . . . . . . . . . . . . . . 9 5. The Map-Referral Message . . . . . . . . . . . . . . . . . . 9 5.1. Action Codes . . . . . . . . . . . . . . . . . . . . . . 9 5.2. Referral Set . . . . . . . . . . . . . . . . . . . . . . 10 5.3. "Incomplete" Flag . . . . . . . . . . . . . . . . . . . . 10 5.4. Map-Referral Message Format . . . . . . . . . . . . . . . 11 5.4.1. Signature Section . . . . . . . . . . . . . . . . . . 13 6. DDT Network Elements and Their Operation . . . . . . . . . . 14 6.1. DDT Node . . . . . . . . . . . . . . . . . . . . . . . . 15 6.1.1. Matching of a Delegated Prefix (or Sub-prefix) . . . 15 6.1.2. Missing Delegation from an Authoritative Prefix . . . 16 6.2. DDT Map-Server . . . . . . . . . . . . . . . . . . . . . 16 6.3. DDT Client . . . . . . . . . . . . . . . . . . . . . . . 16 6.3.1. Queuing and Sending DDT Map-Requests . . . . . . . . 17 6.3.2. Receiving and Following Referrals . . . . . . . . . . 18 6.3.3. Handling Referral Errors . . . . . . . . . . . . . . 19 6.3.4. Referral Loop Detection . . . . . . . . . . . . . . . 20 7. Pseudo-code and Decision Tree Diagrams . . . . . . . . . . . 20 7.1. Map-Resolver Processing of ITR Map-Request . . . . . . . 21 7.1.1. Pseudo-code Summary . . . . . . . . . . . . . . . . . 21 7.1.2. Decision Tree Diagram . . . . . . . . . . . . . . . . 21 7.2. Map-Resolver Processing of Map-Referral Message . . . . . 22 7.2.1. Pseudo-code Summary . . . . . . . . . . . . . . . . . 22 7.2.2. Decision Tree Diagram . . . . . . . . . . . . . . . . 24 7.3. DDT Node Processing of DDT Map-Request Message . . . . . 25 7.3.1. Pseudo-code Summary . . . . . . . . . . . . . . . . . 25 7.3.2. Decision Tree Diagram . . . . . . . . . . . . . . . . 27 8. Example Topology and Request/Referral Following . . . . . . . 28 8.1. Lookup of 2001:db8:0103:1::1/128 . . . . . . . . . . . . 30 8.2. Lookup of 2001:db8:0501:8:4::1/128 . . . . . . . . . . . 31 Saucez & Iannone Expires 24 April 2025 [Page 2] Internet-Draft LISP-DDT October 2024 8.3. Lookup of 2001:db8:0104:2::2/128 . . . . . . . . . . . . 32 8.4. Lookup of 2001:db8:0500:2:4::1/128 . . . . . . . . . . . 33 8.5. Lookup of 2001:db8:0500::1/128 (Nonexistent EID) . . . . 33 9. Securing the Database and Message Exchanges . . . . . . . . . 34 9.1. XEID-Prefix Delegation . . . . . . . . . . . . . . . . . 35 9.2. DDT Node Operation . . . . . . . . . . . . . . . . . . . 35 9.2.1. DDT Public Key Revocation . . . . . . . . . . . . . . 35 9.3. Map-Server Operation . . . . . . . . . . . . . . . . . . 36 9.4. Map-Resolver Operation . . . . . . . . . . . . . . . . . 36 10. Deployment Experience . . . . . . . . . . . . . . . . . . . . 37 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 12. Security Considerations . . . . . . . . . . . . . . . . . . . 37 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 13.1. Normative References . . . . . . . . . . . . . . . . . . 38 13.2. Informative References . . . . . . . . . . . . . . . . . 38 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 1. Introduction The Locator/ID Separation Protocol (LISP) [RFC9300] specifies an architecture and mechanism for replacing the addresses currently used by IP with two separate namespaces: * Endpoint Identifiers (EIDs), used end to end for terminating transport-layer associations, and * Routing Locators (RLOCs), which are bound to topological locations and are used for routing and forwarding. [RFC9301] specifies an interface between a database storing EID-to- RLOC mappings and LISP devices that need this information to forward packets. The internal organization of such a database is beyond the scope of [RFC9301]. Multiple architectures of the database have been proposed, each having its advantages and disadvantages (see, for example, [RFC6836] and [RFC6837]). This document specifies an architecture for a distributed database of LISP EID-to-RLOC mappings, with an emphasis on high scalability. The LISP Delegated Database Tree (LISP-DDT) is a hierarchical distributed database that embodies the delegation of authority to provide mappings, i.e., its internal structure mirrors the hierarchical delegation of address space. It also provides delegation information to Map-Resolvers, which use the information to locate EID-to-RLOC mappings. A Map-Resolver that needs to locate a given mapping will follow a path through the tree-structured database and will contact, one after another, the nodes along that path until it reaches the leaf node(s) authoritative for the mapping it is seeking. Saucez & Iannone Expires 24 April 2025 [Page 3] Internet-Draft LISP-DDT October 2024 LISP offers a general-purpose mechanism for mapping between EIDs and RLOCs. In organizing a database of EID-to-RLOC mappings, this specification extends the definition of the EID numbering space by logically prepending and appending several fields for purposes of defining the database index key: * Database-ID (DBID) (16 bits), * Instance Identifier (IID) (32 bits), * Address Family Identifier (AFI) (16 bits), and * EID-prefix (variable, according to the AFI value). The resulting concatenation of these fields is termed an "Extended EID-prefix", or XEID-prefix. LISP-DDT defines a new device type, the "DDT Node", that is configured as authoritative for one or more XEID-prefixes. It is also configured with the set of more-specific sub-prefixes that are further delegated to other DDT Nodes. To delegate a sub-prefix, the "parent" DDT Node is configured with the RLOCs of each child DDT Node that is authoritative for the sub-prefix. Each RLOC either points to a DDT Map-Server (MS) to which an Egress Tunnel Router (ETR) has registered that sub-prefix or points to another DDT Node in the database tree that further delegates the sub-prefix. See [RFC9301] for a description of the functionality of the Map-Server and Map- Resolver. Note that the target of a delegation must always be an RLOC (not an EID) to avoid any circular dependency. To provide a mechanism for traversing the database tree, LISP-DDT defines the Map-Referral LISP message type, which is returned to the sender of a Map-Request when the receiving DDT Node can refer the sender to another DDT Node that has more detailed information. See Section 5 for the definition of the Map-Referral message. To find an EID-to-RLOC mapping, a LISP-DDT Client, usually a DDT Map- Resolver, starts by sending an Encapsulated Map-Request to a pre- configured DDT Node RLOC. The DDT Node responds with a Map-Referral message indicating that either (1) it will find the requested mapping to complete processing of the request or (2) the DDT Client should contact another DDT Node that has more-specific information; in the latter case, the DDT Node then sends a new Encapsulated Map-Request to the next DDT Node and the process repeats in an iterative manner. Conceptually, this is similar to the way that a client of the Domain Name System (DNS) follows referrals (DNS responses that contain only NS records) from a series of DNS servers until it finds an answer . Saucez & Iannone Expires 24 April 2025 [Page 4] Internet-Draft LISP-DDT October 2024 This document obsoletes [RFC8111]. 2. Requirements Language 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. 3. Definitions of Terms Extended EID (XEID): a LISP EID extended with data uniquely identifying the address space to which it belongs (LISP IID, address family, etc.). See Section 4.1 for a detailed description of XEID data. Extended EID-prefix (XEID-prefix): a LISP EID-prefix prepended with XEID data. An XEID-prefix is used as a key index into the DDT database. XEID-prefixes are used to describe database organization and are not seen as a single entity in protocol messages, though messages contain individual fields constituting XEID-prefixes. DDT Node: a network infrastructure component responsible for specific XEID-prefix(es) and for the delegation of more-specific sub-prefixes to other DDT Nodes. DDT Client: a network infrastructure component that sends DDT Map- Request messages and implements the iterative following of Map- Referral results. Typically, a DDT Client will be a Map-Resolver (as defined by [RFC9301]), but it is also possible for an Ingress Tunnel Router (ITR) to implement DDT Client functionality. DDT Map-Server: a DDT Node that also implements Map-Server functionality (forwarding Map-Requests and/or returning Map- Replies if offering a proxy Map-Reply service) for a subset of its delegated prefixes. Map-Server functions, including proxying Map- Replies, are described in [RFC9301]. DDT Map-Server peers: a list of all DDT Map-Servers performing Map- Server functionality for the same prefix. If peers are configured on a DDT Map-Server, then the latter will provide complete information about the prefix in its Map-Replies; otherwise, the Map-Server will mark the returned reply as potentially incomplete. DDT Map-Resolver: a network infrastructure element that implements Saucez & Iannone Expires 24 April 2025 [Page 5] Internet-Draft LISP-DDT October 2024 both DDT Client functionality and Map-Resolver functionality as defined by [RFC9301]. A DDT Map-Resolver accepts Map-Requests from ITRs, sends DDT Map-Requests to DDT Nodes, and implements the iterative following of Map-Referrals. Note that Map-Resolvers do not respond to clients that sent Map-Requests; they only ensure that the Map-Request has been forwarded to a LISP device (ETR or proxy Map-Server) that will provide an authoritative response to the original requester. A DDT Map-Resolver will typically maintain a cache (termed the "XXX define term?? referral cache") of previously received Map-Referral message results containing RLOCs for DDT Nodes responsible for XEID-prefixes of interest. DDT Map-Request: an Encapsulated Map-Request sent by a DDT Client to a DDT Node. The "DDT-originated" flag is set in the encapsulation header, indicating that the DDT Node should return Map-Referral messages if the Map-Request EID matches a delegated XEID-prefix known to the DDT Node. Section 6.3.1 describes how DDT Map- Requests are sent. [RFC9301] defines the position of the "DDT- originated" flag in the Encapsulated Control Message header. Authoritative XEID-prefix: an XEID-prefix delegated to a DDT Node and for which the DDT Node may provide further delegations of more-specific sub-prefixes. Map-Referral: a LISP message sent by a DDT Node in response to a DDT Map-Request for an XEID that matches a configured XEID-prefix delegation. A non-Negative Map-Referral includes a "referral" consisting in set of RLOCs for DDT Nodes that have information about the more-specific XEID-prefix covering the requested XEID. A DDT Client "follows the referral" by sending another DDT Map- Request to one of those RLOCs to obtain either an answer or another referral to DDT Nodes responsible for an XEID-prefix that is even more specific. See Section 6.1 and Section 6.3 for details on the sending and processing of Map-Referral messages. Negative Map-Referral: a reply from an authoritative DDT Node that there is no mapping for the requested XEID. A Negative Map- Referral is a Map-Referral sent in response to a DDT Map-Request that matches an authoritative XEID-prefix but for which there is no delegation configured (or no ETR registration, if sent by a DDT Map-Server). Pending Requests List: the set of outstanding requests for which a DDT Map-Resolver has received Encapsulated Map-Requests from its clients seeking EID-to-RLOC mapping for an XEID. Each entry in the list contains additional state needed by the referral- following process, including the XEID, requester(s) of the XEID (typically one or more ITRs), saved information about the last Saucez & Iannone Expires 24 April 2025 [Page 6] Internet-Draft LISP-DDT October 2024 referral received and followed (matching XEID-prefix, action code, RLOC set, index of the last RLOC queried in the RLOC set), and any LISP-Security (LISP-SEC) information [RFC9303] that was included in the DDT Client Map-Request. An entry in the list may be interchangeably termed a "pending requests list entry" or simply a "pending request". For definitions of other terms, notably Map-Request, Encapsulated Map-Request,Map-Reply, ITR, ETR, Map-Server, and Map-Resolver, please consult the LISP specification [RFC9300] and the LISP Control Plane specification [RFC9301]. 4. Database Organization 4.1. XEID-Prefixes A DDT database is indexed by Extended EID-prefixes (XEID-prefixes). An XEID-prefix is a LISP EID-prefix that includes additional data to uniquely identify the address space associated with the prefix. An XEID-prefix is composed of four binary-encoded fields, ordered by significance: * DBID (16 bits), * Instance ID (32 bits), * AFI (16 bits), * and EID-prefix (variable, according to the AFI value). * DBID (16 bits), * Padding (8 bits), * Instance ID (24 bits), * AFI (16 bits), * and EID-prefix (variable, according to the AFI value). The fields are concatenated, with the most significant fields as listed above . The DBID is the LISP-DDT Database-ID, a 16-bit field provided to allow the definition of multiple databases. Implementations that are compliant with this document must always set this field to 0. Other values of the DBID are reserved for future use. Saucez & Iannone Expires 24 April 2025 [Page 7] Internet-Draft LISP-DDT October 2024 The Instance ID (IID), defined in [RFC9300], is a 24-bit value describing the context of the EID-prefix See Section 8 of [RFC9300] for more discussion of Instance IDs. In this specification the Instance ID is extended on a 32-bit field by prepending 8 bits. The prepended bits MUST be set to zero. The AFI is a 16-bit value defining the syntax of the EID-prefix. AFI values are assigned by IANA [AFI]. 4.2. Structure of the DDT Database The LISP-DDT database for each DDT Node is organized as a tree structure that is indexed by XEID-prefixes . Leaves of the database tree describe the delegation of authority between DDT Nodes (see Section 4.3 for details regarding delegation and information kept in the database entries). DDT Map-Requests sent by the DDT Client to DDT Nodes always contain specific values for the DBID, IID, and AFI; unspecified values or ranges of values are never used for any of these fields. Thus, an XEID-prefix used as a key for searches in the database tree will have a length of at least 64 bits . A DDT Node may, for example, be authoritative for a consecutive range of 3-tuples (DBID, IID, AFI) and all associated EID-prefixes, or only for a specific EID-prefix of a single 3-tuple. Thus, XEID-prefixes/ keys of the database tree leaves may have lengths less than, equal to, or more than 64 bits. It is important to note that LISP-DDT does not store actual EID-to- RLOC mappings; it is, rather, a distributed index that can be used to find the devices (ETRs that registered their EIDs with DDT Map- Servers) that can be queried with LISP to obtain those mappings. Changes to EID-to-RLOC mappings are made on the ETRs that define them, not to any DDT Node configuration. DDT Node configuration changes are only required when branches of the database hierarchy are added, removed, or modified. 4.3. Configuring Prefix Delegation Every DDT Node is configured with one or more XEID-prefixes for which it is authoritative , along with a list of delegations of XEID- prefixes to other DDT Nodes. A DDT Node is required to maintain a list of delegations for all sub-prefixes of its authoritative XEID- prefixes; it also may list "hints", which are prefixes that it knows about that belong to its parents, to the root, or to any other point in the XEID-prefix hierarchy. A delegation (or hint) consists of an XEID-prefix, a set of RLOCs for DDT Nodes that have more detailed Saucez & Iannone Expires 24 April 2025 [Page 8] Internet-Draft LISP-DDT October 2024 knowledge of the XEID-prefix, and accompanying security information (for details regarding security information exchange and its use, see Section 9). Those RLOCs are returned in Map-Referral messages when the DDT Node receives a DDT Map-Request with an XEID that matches a delegation. A DDT Map-Server will also have a set of sub-prefixes for which it accepts ETR mapping registrations and for which it will forward (or reply, if it provides a proxy Map-Reply service) Map- Requests. One or more XEID-prefixes for which a DDT Node is authoritative, and the delegation of authority for sub-prefixes, are provided as part of the configuration of the DDT Node. 4.3.1. The Root DDT Node The root DDT Node is the logical "top" of the distributed database hierarchy. It is authoritative for all XEID-prefixes, namely, for all valid 3-tuples (DBID, IID, AFI) and their EID-prefixes. A DDT Map-Request that matches no configured XEID-prefix will be referred to the root node (see Section 7 for a formal description of conditions where a DDT Map-Request is forwarded to the root node). The root node in a particular instantiation of LISP-DDT therefore MUST be configured, at a minimum, with delegations for all defined Instance IDs and AFIs . 5. The Map-Referral Message This specification defines a new LISP message called the Map-Referral message. A Map-Referral message is sent by a DDT Node to a DDT Client in response to a DDT Map-Request message. See Section 5.4 for a detailed layout of the Map-Referral message fields. The message consists of an action code along with delegation information about the XEID-prefix that matches the requested XEID. 5.1. Action Codes The action codes are as follows: NODE-REFERRAL (0): indicates that the replying DDT Node has delegated an XEID-prefix that matches the requested XEID to one or more other DDT Nodes. The Map-Referral message contains a "map- record" with additional information, most significantly, the set of RLOCs to which the prefix has been delegated, which is used by a DDT Client to "follow" the referral. MS-REFERRAL (1): indicates that the replying DDT Node has delegated Saucez & Iannone Expires 24 April 2025 [Page 9] Internet-Draft LISP-DDT October 2024 an XEID-prefix that matches the requested XEID to one or more DDT Map-Servers. It contains the same additional information as a NODE-REFERRAL, but is handled slightly differently by the receiving DDT Client (see Section 6.3.2). MS-ACK (2): indicates that the replying DDT Map-Server received a DDT Map-Request that matches an authoritative XEID-prefix for which it has one or more registered ETRs. This means that the request has been forwarded to one of those ETRs to provide an answer to the querying ITR. MS-NOT-REGISTERED (3): indicates that the replying DDT Map-Server received a Map-Request for one of its configured XEID-prefixes that has no ETRs registered. DELEGATION-HOLE (4): indicates that the requested XEID matches a non-delegated sub-prefix of the XEID space. This is a non-LISP "hole", which has not been delegated to any DDT Map-Server or ETR. See Section 6.1.2 for details. Also sent by a DDT Map-Server with authoritative configuration covering the requested EID but for which no specific site ETR is configured. NOT-AUTHORITATIVE (5): indicates that the replying DDT Node received a Map-Request for an XEID for which it is not authoritative and has no configured matching hint referrals. This can occur if a cached referral has become invalid due to a change in the database hierarchy. However, if such a DDT Node has a "hint" delegation covering the requested EID, it MAY choose to return NODE-REFERRAL or MS-REFERRAL as appropriate. When returning action code NOT- AUTHORITATIVE, the DDT Node MUST provide the EID-prefix received in the request and the TTL MUST be set to 0. 5.2. Referral Set For "positive" action codes (NODE-REFERRAL, MS-REFERRAL, MS-ACK), a DDT Node MUST include in the Map-Referral message a list of RLOCs for DDT Nodes that are authoritative for the XEID-prefix being returned. A DDT Client uses this information to contact one of those DDT Nodes as it "follows" a referral. 5.3. "Incomplete" Flag A DDT Node sets the "Incomplete" flag in a Map-Referral message if the Referral Set is incomplete; this is intended to prevent a DDT Client from caching a referral with incomplete information. A DDT node MUST set the "Incomplete" flag in the following cases: Saucez & Iannone Expires 24 April 2025 [Page 10] Internet-Draft LISP-DDT October 2024 * If it is setting action code MS-ACK or MS-NOT-REGISTERED but the matching XEID-prefix is not flagged as "complete" in the configuration. The XEID-prefix configuration on the DDT Map- Server SHOULD be marked as "complete" when the configuration of the XEID-prefix lists all "peer" DDT Nodes that are also authoritative for the same XEID-prefix or when it is known that a local DDT Node is the only authoritative node for the XEID-prefix . * If it is setting action code NOT-AUTHORITATIVE. 5.4. Map-Referral Message Format The format of the Map-Referral message is depicted in Figure 1. 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=6 | Reserved | Record Count | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Nonce . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . . . Nonce | +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Record TTL | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R | Referral Count| EID mask-len | ACT |A|I| Reserved | e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ c |SigCnt | Map Version Number | EID-AFI | o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ r | EID-prefix ... | d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | /| Priority | Weight | M Priority | M Weight | | R +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | e | Unused Flags |L|p|R| Loc-AFI | | f +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | \| Locator ... | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ~ Sig section ~ +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Map-Referral message format. Type: This document allocates type value 6 to identify Map-Referral messages (see Section 11). ACT: The ACT (Action) field of the mapping Record in a Map-Referral Saucez & Iannone Expires 24 April 2025 [Page 11] Internet-Draft LISP-DDT October 2024 message encodes one of the action types. See Section 5.1 for descriptions of action types defined in the present specification. Incomplete: The "I" bit indicates that a DDT Node's Referral Set of locators is incomplete and the receiver of this message SHOULD NOT cache the referral. A DDT sets the "Incomplete" flag, the TTL, and the Action field as follows: +=====================+============+==============+============+ | Type (Action field) | Incomplete | Referral Set | TTL values | +=====================+============+==============+============+ | 0 NODE-REFERRAL | No | Yes | 1440 | +---------------------+------------+--------------+------------+ | 1 MS-REFERRAL | No | Yes | 1440 | +---------------------+------------+--------------+------------+ | 2 MS-ACK | * | * | 1440 | +---------------------+------------+--------------+------------+ | 3 MS-NOT-REGISTERED | * | * | 1 | +---------------------+------------+--------------+------------+ | 4 DELEGATION-HOLE | No | No | 15 | +---------------------+------------+--------------+------------+ | 5 NOT-AUTHORITATIVE | Yes | No | 0 | +---------------------+------------+--------------+------------+ Table 1: I/TTL/ACT Settings The "Incomplete" flag setting for the Map-Server-originated referral of MS-ACK and MS-NOT-REGISTERED types depends on whether the Map-Server has the full peer Map-Server configuration for the same prefix and has encoded the information in the mapping Record. The "Incomplete" bit is not set when the Map-Server has encoded the information; this means that the Referral Set includes all the RLOCs of all Map-Servers that serve the prefix. It MUST be set when the configuration of the Map-Server does not flag the matching prefix as configured with the complete information about "peer" Map-Servers or when the Map-Server does not return all configured locators. Referral Count: Number of RLOCs in the current Referral Set. This number is equal to the number of "Ref" sections in the message (as shown Figure 1). SigCnt: Indicates the number of signatures (Signature section) present in the Record. If SigCnt is larger than 0, the signature information captured in a Signature section as described in Section 5.4.1 will be appended to the end of the Record. The number of Signature sections at the end of the Record MUST match the SigCnt. Saucez & Iannone Expires 24 April 2025 [Page 12] Internet-Draft LISP-DDT October 2024 Loc-AFI: AFI of the Locator field. If the AFI value is equal to an LISP Canonical Address Format (LCAF) AFI, the contents of the LCAF depend on the Type field of the LCAF. LCAF Type 11, is used to store security material along with the AFI of the locator. DDT Nodes and DDT Map-Servers uses this LCAF Type to include public keys associated with their child DDT Nodes for an XEID-prefix Map- Referral Record. LCAF Types and formats are defined in [RFC8060]. If the AFI value is different from the LISP Canonical Address Format (LCAF) AFI, then security keys are not included in the Record. Locator: RLOC of a DDT Node to which the DDT Client is being referred. This is a variable-length field; its length is determined by the Loc-AFI setting. All other fields and their descriptions are equivalent to those in the Map-Reply message, as defined in LISP [RFC9301]. Note, though, that the set of RLOCs correspond to the DDT Node to be queried as a result of the referral and not to the RLOCs for an actual EID-to-RLOC mapping. 5.4.1. Signature Section SigCnt counts the number of signature sections that appear at the end of the Record. The format of the signature section is described Figure 2. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /| Original Record TTL | / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Signature Expiration | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ s | Signature Inception | i +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ g | Key Tag | Sig Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | Sig-Algorithm | Reserved | Reserved | \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ ~ Signature ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Map-Referral Signature Section format. Original Record TTL: The original Record TTL for this Record that is covered by the signature. The Record TTL value is specified in minutes. Signature Expiration and Signature Inception: Specify the validity Saucez & Iannone Expires 24 April 2025 [Page 13] Internet-Draft LISP-DDT October 2024 period for the signature. The signature MUST NOT be used for authentication prior to the inception date and MUST NOT be used for authentication after the expiration date. Each field specifies a date and time in the form of a 32-bit unsigned number of seconds elapsed since 1 January 1970 00:00:00 UTC, ignoring leap seconds, in network byte order. Key Tag: An identifier to specify which key is used for this signature if more than one valid key exists for the signing DDT Node. Sig Length: The length of the Signature field in bytes. Sig-Algorithm: The identifier of the cryptographic algorithm used for the signature. Sig-Algorithm values defined in this specification are listed in Table 2. Implementations conforming to this specification MUST implement at least RSA-SHA256 for DDT signing. Sig-Algorithm type 1 (RSA-SHA1) is deprecated and SHOULD NOT be used. +===============+============+===========+============+ | Sig-Algorithm | Name | Reference | Notes | +===============+============+===========+============+ | 1 | RSA-SHA1 | [RFC8017] | DEPRECATED | +---------------+------------+-----------+------------+ | 2 | RSA-SHA256 | [RFC8017] | MANDATORY | +---------------+------------+-----------+------------+ Table 2: Sig-Algorithm Values Reserved: MUST be set to 0 on transmit and MUST be ignored on receipt. Signature: Contains the cryptographic signature that covers the entire Map-Referral Record to which this signature belongs. For the purpose of computing the signature, the Record TTL (Section 5.4) value is set to the value of Original Record TTL and the Signature field is filled with zeros. 6. DDT Network Elements and Their Operation As described above, LISP-DDT introduces a new network element, namely the DDT Node and extends the functionality of Map-Servers and Map- Resolvers to send and receive Map-Referral messages. The operation of each of these devices is described below. Saucez & Iannone Expires 24 April 2025 [Page 14] Internet-Draft LISP-DDT October 2024 6.1. DDT Node When a DDT Node receives a DDT Map-Request, it compares the requested XEID against its list of XEID-prefix delegations and its list of authoritative XEID-prefixes, and depending on whether or not there is a match, different actions are taken, as described below. 6.1.1. Matching of a Delegated Prefix (or Sub-prefix) If the requested XEID matches one of the DDT Node's delegated prefixes, then a Map-Referral message is returned with the matching more-specific XEID-prefix and the set of RLOCs for the referral target DDT Nodes, including associated security information (see Section 9 for details on security). If at least one DDT Node of the delegation is known to be a DDT Map-Server, then the Map-Referral message SHOULD be sent with action code MS-REFERRAL to indicate to the receiver that LISP-SEC information (if saved in the pending request) SHOULD be included in the next DDT Map-Request; otherwise, the action code NODE-REFERRAL SHOULD be used. Note that a matched delegation does not have to be for a sub-prefix of an authoritative prefix; in addition to being configured to delegate sub-prefixes of an authoritative prefix, a DDT Node may also be configured with other XEID-prefixes for which it can provide referrals to DDT Nodes anywhere in the database hierarchy. This capability to define "shortcut hints" is never required to be configured, but it may be a useful heuristic for reducing the number of iterations needed to find an EID, particularly for private network deployments. Referral hints, if used properly, may reduce the number of referrals a DDT Client needs to follow to locate a DDT Map-Server authoritative for the XEID-prefix being resolved. On the other hand, the incorrect use of hints may create circular dependencies (or "referral loops") between DDT Nodes. A DDT Client MUST be prepared to handle such circular referrals. See Section 6.3.4 for a discussion of referral loops and measures that the DDT Client must implement in order to detect circular referrals and prevent infinite looping. Another danger related to the use of hints is when a DDT deployment spans multiple administrative domains (i.e., different authorities manage DDT Nodes in the same DDT database). In this case, an operator managing a DDT Node may not be aware of the fact that the node is being referred to by hints. Locator addresses in hints may become stale when referred DDT Nodes are taken out of service or change their locator addresses. Saucez & Iannone Expires 24 April 2025 [Page 15] Internet-Draft LISP-DDT October 2024 6.1.2. Missing Delegation from an Authoritative Prefix If the requested XEID did not match a configured delegation but does match an authoritative XEID-prefix, then the DDT Node MUST return a Negative Map-Referral that uses the least-specific XEID-prefix that does not match any XEID-prefix delegated by the DDT Node. The action code is set to DELEGATION-HOLE, which indicates that the XEID is not a LISP destination. If the requested XEID did not match either a configured delegation, an authoritative XEID-prefix, or a hint, then a Negative Map-Referral with action code NOT-AUTHORITATIVE MUST be returned. 6.2. DDT Map-Server When a DDT Map-Server receives a DDT Map-Request, its operation is similar to that of a DDT Node, with additional processing as follows: * If the requested XEID matches a registered XEID-prefix, then the Map-Request is forwarded to one of the destination ETR RLOCs (or the Map-Server sends a Map-Reply, if it is providing a proxy Map- Reply service), and a Map-Referral with action code MS-ACK MUST be returned to the sender of the DDT Map-Request. * If the requested XEID matches a configured XEID-prefix for which no ETR registration has been received, then a Negative Map- Referral with action code MS-NOT-REGISTERED MUST be returned to the sender of the DDT Map-Request. 6.3. DDT Client A DDT Client queries one or more DDT Nodes and uses an iterative process of following returned referrals until it receives one with action code MS-ACK (or an error indication). MS-ACK indicates that the Map-Request has been sent to a Map-Server that will forward it to an ETR that, in turn, will provide a Map-Reply to the locator address in the Map-Request. DDT Client functionality will typically be implemented by DDT Map- Resolvers. Just as would any other Map-Resolver, a DDT Map-Resolver accepts Map-Requests from its clients (typically ITRs) and ensures that those Map-Requests are forwarded to the correct ETR, which generates Map-Replies. However, a DDT Map-Resolver implements DDT Client functionality to find the correct ETR to answer a Map-Request, which in turns requires a DDT Map-Resolver to maintain additional state, namely a Map-Referral cache and a pending requests list of XEIDs that are going through the iterative referral process. Saucez & Iannone Expires 24 April 2025 [Page 16] Internet-Draft LISP-DDT October 2024 DDT Client functionality may be implemented on ITRs. In this case, the DDT Client will not receive a Map-Request from another network element; instead, equivalent information will be provided to the DDT Client via a programming interface. 6.3.1. Queuing and Sending DDT Map-Requests When a DDT Client receives a request to resolve an XEID (in the case of a DDT Map-Resolver, this will be in the form of a received Encapsulated Map-Request), it first performs a longest-match search for the XEID in its referral cache. If no match is found or if a negative cache entry is found, then the destination is not in the database; a Negative Map-Reply MUST be returned, and no further processing is performed by the DDT Client. If a match is found, the DDT Client creates a pending request list entry for the XEID and saves the original request (in the case of a DDT Map-Resolver, this will be the original Map-Request minus the encapsulation header) along with other information needed to track progress through the iterative referral process; the "referral XEID- prefix" is also initialized to indicate that no referral has yet been received. The DDT Client then creates a DDT Map-Request (which is an Encapsulated Map-Request with the "DDT-originated" flag set in the message header) for the XEID but without any authentication data that may have been included in the original request. It sends the DDT Map-Request to one of the RLOCs in the chosen referral cache entry. The referral cache is initially populated with one or more statically configured entries; additional entries are added when referrals are followed, as described below. A DDT Client is not required to cache referrals, but doing so will decrease latency and reduce lookup delays. Note that in normal use, the statically configured initial referral cache for a DDT Client should include a "default" entry with RLOCs for either the root DDT Node or one or more DDT Nodes that contain hints for the root DDT Node. If a DDT client does not have such a configuration, it will return a Negative Map-Reply if it receives a query for an EID outside the subset of the mapping database known to it. If DDT message exchanges are authenticated as described in Section 9, then the DDT Client MUST also be configured with public keys of DDT Nodes pointed to by the "default" cache entry. In this case, the "default" entry will typically be for the root DDT Node. Saucez & Iannone Expires 24 April 2025 [Page 17] Internet-Draft LISP-DDT October 2024 6.3.2. Receiving and Following Referrals After sending a DDT Map-Request, a DDT Client expects to receive a Map-Referral response. If none occurs within the timeout period, the DDT Client retransmits the request, sending it to the next RLOC in the referral cache entry if one is available. If all RLOCs have been tried and the maximum number of retransmissions has occurred for each, then the pending request list entry is dequeued and discarded. In this case, the DDT Client returns no response to the sender of the original request. A DDT Client processes a received Map-Referral message according to each action code: NODE-REFERRAL: The DDT Client checks for a possible referral loop as described in Section 6.3.4. If no loop is found, the DDT Client saves the prefix returned in the Map-Referral message in the referral cache, updates the saved prefix and saved RLOCs in the pending request list entry, and follows the referral by sending a new DDT Map-Request to one of the DDT Node RLOCs listed in the Referral Set. Security information saved with the original Map- Request SHOULD NOT be included. MS-REFERRAL: The DDT Client processes an MS-REFERRAL in the same manner as a NODE-REFERRAL, except that security information saved with the original Map-Request MUST be included in the new Map- Request sent to a Map-Server (see Section 9 for details on security). MS-ACK: An MS-ACK is returned by a DDT Map-Server to indicate that it has one or more registered ETRs that can answer a Map-Request for the XEID and the request has been forwarded to one of them (or, if the Map-Server is providing a proxy service for the prefix, then a reply has been sent to the querying ITR). If the pending request did not include saved LISP-SEC information or if that information was already included in the previous DDT Map- Request (sent by the DDT Client in response to either an MS- REFERRAL or a previous MS-ACK referral), then the pending request for the XEID is complete, processing of the request stops, and all request state can be discarded. Otherwise, LISP-SEC information is required and has not yet been sent to the authoritative DDT Map-Server; the DDT Client MUST resend the DDT Map-Request with LISP-SEC information included, and the pending request queue entry remains until another Map-Referral with action code MS-ACK is received. If the "Incomplete" flag is not set, the prefix is saved in the referral cache. MS-NOT-REGISTERED: The DDT Map-Server queried could not process the Saucez & Iannone Expires 24 April 2025 [Page 18] Internet-Draft LISP-DDT October 2024 request because it did not have any ETRs registered for a matching, authoritative XEID-prefix. If the DDT Client has not yet tried all of the RLOCs saved with the pending request, then it sends a Map-Request to the next RLOC in that list. If all RLOCs have been tried, then the destination XEID is not registered and is unreachable. The DDT Client MUST return a Negative Map-Reply to the requester (or, in the case of a DDT Map-Resolver, to the sender of the original Map-Request). This Map-Reply contains the least-specific XEID-prefix in the range for which this DDT Map- Server is authoritative and in which no registrations exist. The TTL value of the Negative Map-Reply SHOULD be set to 1 minute. A negative referral cache entry is created for the prefix (whose TTL also SHOULD be set to 1 minute), and processing of the request stops. DELEGATION-HOLE: The DDT Map-Server queried did not have an XEID- prefix defined that matched the requested XEID, so the XEID does not exist in the mapping database. The DDT Client MUST return a Negative Map-Reply to the requester (or, in the case of a DDT Map- Resolver, to the sender of the original Map-Request); this Map- Reply SHOULD indicate the least-specific XEID-prefix matching the requested XEID for which no delegations exist and SHOULD have a TTL value of 15 minutes. A negative referral cache entry is created for the prefix (which also SHOULD have a TTL of 15 minutes), and processing of the pending request stops. NOT-AUTHORITATIVE: The DDT Map-Server queried is not authoritative for the requested XEID. This can occur if a cached referral has become invalid due to a change in the database hierarchy. If the DDT Client receiving this message can determine that it is using old cached information, it MAY choose to delete that cached information and retry the original Map-Request, starting from its "root" cache entry. If this action code is received in response to a query that did not use cached referral information, then it indicates a database synchronization problem or configuration error. The pending request is silently discarded; i.e., all state for the request that caused this answer is removed, and no answer is returned to the original requester. 6.3.3. Handling Referral Errors Other states are possible, such as a misconfigured DDT Node (acting as a proxy Map-Server, for example) returning a Map-Reply to the DDT client; they should be considered errors and logged as such. It is not clear exactly what else the DDT Client should do in such cases; one possibility is to remove the pending request list entry and send a Negative Map-Reply to the requester (or, in the case of a DDT Map- Resolver, to the sender of the original Map-Request Alternatively, if Saucez & Iannone Expires 24 April 2025 [Page 19] Internet-Draft LISP-DDT October 2024 a DDT Client detects unexpected behavior by a DDT node, it could mark that node as unusable in its referral cache and update the pending request to try a different DDT Node if more than one is listed in the referral cache. In any case, any prefix contained in a Map-Referral message that causes a referral error (including a referral loop) is not saved in the DDT Client referral cache. 6.3.4. Referral Loop Detection In response to a Map-Referral message with action code NODE-REFERRAL or MS-REFERRAL, a DDT Client is directed to query a new set of DDT node RLOCs that are expected to have more-specific XEID-prefix information for the requested XEID. To prevent a possible "iteration loop" (following referrals back and forth among a set of DDT Nodes without ever finding an answer), a DDT Client saves the last received referral XEID-prefix for each pending request and checks to see if a newly received NODE-REFERRAL or MS-REFERRAL message contains a more- specific referral XEID-prefix; an exact or less-specific match of the saved XEID-prefix indicates a referral loop. If a loop is detected, the DDT Map-Resolver handles the request as described in Section 6.3.3. Otherwise, the DDT Client saves the most recently received referral XEID-prefix with the pending request when it follows the referral. As an extra measure to prevent referral loops, it is probably also wise to limit the total number of referrals for any request to some reasonable number; the exact value of that number will be determined during experimental deployment of LISP-DDT but is bounded by the maximum length of the XEID. Note that when a DDT Client adds an entry to its lookup queue and sends an initial Map-Request for an XEID, the queue entry has no previous referral XEID-prefix; this means that the first DDT Node contacted by a DDT Map-Resolver may provide a referral to anywhere in the DDT hierarchy. This, in turn, allows a DDT Client to use essentially any DDT Node RLOCs for its initial cache entries and depend on the initial referral to provide a good starting point for Map-Requests; there is no need to configure the same set of root DDT nodes on all DDT Clients. 7. Pseudo-code and Decision Tree Diagrams To illustrate the DDT algorithms described above and to aid in implementation, each of the major DDT Map-Server and DDT Map-Resolver functions are described below, first using simple "pseudo-code" and then in the form of a decision tree. Saucez & Iannone Expires 24 April 2025 [Page 20] Internet-Draft LISP-DDT October 2024 7.1. Map-Resolver Processing of ITR Map-Request 7.1.1. Pseudo-code Summary if ( request pending, i.e., (ITR,EID) of request same ) { replace old request with new, & use new request nonce for future requests } else if ( no match in refcache ) { return Negative Map-Reply to ITR } else if ( match type DELEGATION-HOLE ) { return Negative Map-Reply to ITR } else if ( match type MS-ACK ) { fwd DDT Map-Request to Map-Server } else { store & fwd DDT Map-Request w/o security material to node delegation } 7.1.2. Decision Tree Diagram Saucez & Iannone Expires 24 April 2025 [Page 21] Internet-Draft LISP-DDT October 2024 +-----------------+ Yes | Is request |---> Replace old request with | pending? | new nonce for future requests +-----------------+ |No | V +-----------------+ No | Match in | | referral cache? |---> Send Negative Map-Reply +-----------------+ (unlikely event, as root or hint |Yes configured on every Map-Resolver) | V +-----------------+ | Match type | Yes | DELEGATION-HOLE |---> Send Negative Map-Reply +-----------------+ |No | V +-----------------+ | Match type | Yes | MS-ACK? |---> Forward DDT Map-Request to +-----------------+ Map-Server |No | V Store original request & send DDT Map-Request w/o security material to DDT Node delegation 7.2. Map-Resolver Processing of Map-Referral Message 7.2.1. Pseudo-code Summary if ( authentication signature validation failed ) { silently drop } if ( no request pending matched by referral nonce ) { silently drop } if ( pfx in referral less specific than last referral used ) { if ( gone through root ) { silently drop } else { send request to root Saucez & Iannone Expires 24 April 2025 [Page 22] Internet-Draft LISP-DDT October 2024 } } switch (map_referral_type) { case NOT_AUTHORITATIVE: if ( gone through root ) { return Negative Map-Reply to ITR } else { send request to root } case DELEGATION_HOLE: cache & send Negative Map-Reply to ITR case MS_REFERRAL: if ( referral equal to last used ) { if ( gone through root ) { return Negative Map-Reply to ITR } else { send request to root } } else { cache follow the referral; include security material } case NODE_REFERRAL: if ( referral equal to last used ) { if ( gone through root ) { return Negative Map-Reply to ITR } else { send request to root } } else { cache follow the referral; strip security material } case MS_ACK: if ( security material stripped ) { resend request with security material if { !incomplete } { cache } } case MS_NOT_REGISTERED: Saucez & Iannone Expires 24 April 2025 [Page 23] Internet-Draft LISP-DDT October 2024 if { all Map-Server delegations not tried } { follow delegations not tried if ( !incomplete ) { cache } } else { send Negative Map-Reply to ITR if { !incomplete } { cache } } case DEFAULT: drop } 7.2.2. Decision Tree Diagram +-----------------------+ No | Auth signature Valid ?|--> Silently drop +-----------------------+ | Yes | V +------------------------+No | Is request pending? |--> Silently drop +------------------------+ | Yes | V +------------------------------+Yes | Pfx less specific than last? |--> Silently drop +------------------------------+ |No | V +----------------------------------------------+ | What is Map-Referral type? |--> Unknown--+ +----------------------------------------------+ | | | | | | DEL_HOLE v | | | | MS_ACK | Drop | | | | | V | | MS_REF NODE_REF | Cache & return | | | | V Negative Map-Reply | | | | +----------+ | NOT_AUTH | | | Was sec | Yes | | | | | material |---> Done | | | | |stripped? | Saucez & Iannone Expires 24 April 2025 [Page 24] Internet-Draft LISP-DDT October 2024 | | V V +----------+ | | +-----------+ |No | | Yes| Pfx equal | V MS_NOT_REGISTERED | +---| to last | +------------+ | | | | used? | |"Incomplete"|Yes | | | +-----------+ | bit set? |--> Resend DDT | V V |No +------------+ request w/ | +------------+ | |No security | |Gone through| V | material | | root? | Cache & follow | | +------------+ the referral | | |No |Yes v | | | Cache & resend DDT | V V request with | Send req Send Negative security material | to root Map-Reply V +-----------+Yes +----------+Yes | Other MS |-Follow other MS---------->|Incomplete|--> Do not cache | not tried?| | bit set? | | |-Send Negative Map-Reply-->| |--> Cache +-----------+No +----------+No 7.3. DDT Node Processing of DDT Map-Request Message 7.3.1. Pseudo-code Summary Saucez & Iannone Expires 24 April 2025 [Page 25] Internet-Draft LISP-DDT October 2024 if ( I am not authoritative ) { send Map-Referral NOT_AUTHORITATIVE with "Incomplete" bit set and TTL 0 } else if ( delegation exists ) { if ( delegated Map-Servers ) { send Map-Referral MS_REFERRAL with TTL 'Default_DdtNode_Ttl' } else { send Map-Referral NODE_REFERRAL with TTL 'Default_DdtNode_Ttl' } } else { if ( EID in site) { if ( site registered ) { forward Map-Request to ETR if ( Map-Server peers configured ) { send Map-Referral MS_ACK with TTL 'Default_Registered_Ttl' } else { send Map-Referral MS_ACK with TTL 'Default_Registered_Ttl' and "Incomplete" bit set } } else { if ( Map-Server peers configured ) { send Map-Referral MS_NOT_REGISTERED with TTL 'Default_Configured_Not_Registered_Ttl' } else { send Map-Referral MS_NOT_REGISTERED with TTL 'Default_Configured_Not_Registered_Ttl' and "Incomplete" bit set } } } else { send Map-Referral DELEGATION_HOLE with TTL 'Default_Negative_Referral_Ttl' } } where architectural constants for TTL are set as follows: * Default_DdtNode_Ttl 1440 minutes * Default_Registered_Ttl 1440 minutes * Default_Negative_Referral_Ttl 15 minutes * Default_Configured_Not_Registered_Ttl 1 minute Saucez & Iannone Expires 24 April 2025 [Page 26] Internet-Draft LISP-DDT October 2024 7.3.2. Decision Tree Diagram +------------+ | Am I |No | authori- |--> Return NOT_AUTHORITATIVE | tative? | Incomplete = 1 +------------+ TTL = Default_DdtNode_Ttl |Yes | V +------------+ +-------------+ | Delegation |Yes | Delegations |Yes | exists? |---->| are |---> Return MS_REFERRAL | | | Map-Servers?| TTL = Default_DdtNode_Ttl +------------+ +-------------+ | |No |No +--> Return NODE_REFERRAL | TTL = Default_DdtNode_Ttl V +------------+ +------------+ +------------+ | EID in |Yes | Site |Yes | Map-Server | | site |---->| registered?|-->Forward---->| peers | | config? | | | Map-Request | configured?| +------------+ +------------+ to ETR +------------+ |No |No No| |Yes | | | | | | V V | | Return MS_ACK Return MS_ACK | V with INC=1 | +------------+ TTL = Default_Registered_Ttl | | Map-Server |Yes | | peers |-->Return MS_NOT_REGISTERED | | configured?| TTL = Default_Negative_Referral_Ttl | +------------+ | |No | +--> Return MS_NOT_REGISTERED | Incomplete = 1 V TTL = Default_Negative_Referral_Ttl Return DELEGATION_HOLE TTL = Default_Negative_Referral_Ttl Saucez & Iannone Expires 24 April 2025 [Page 27] Internet-Draft LISP-DDT October 2024 8. Example Topology and Request/Referral Following This section shows an example of DDT tree and several possible scenarios of Map-Requests coming to a Map-Resolver and subsequent iterative DDT referrals. In this example, RLOCs of DDT Nodes are shown in the IPv4 address space while the EIDs are in the IPv6 address space. The same principle of hierarchical delegation and pinpointing referrals is equally applicable to any address family whose address hierarchy can be expressed as a bit string with associated length. To show how referrals are followed to find the RLOCs for a number of EIDs, consider the example of EID topology for DBID=0, IID=0, AFI=2, and EID=0/0 in Figure 3. Saucez & Iannone Expires 24 April 2025 [Page 28] Internet-Draft LISP-DDT October 2024 +---------------------+ +---------------------+ | root1: 192.0.2.1 | | root2: 192.0.2.2 | | authoritative: ::/0 | | authoritative: ::/0 | +---------------------+ +---------------------+ | \ / | | \/ | | /\ | | / \ | V V V V +-----------------------+ +-----------------------+ | DDT Node1: 192.0.2.11 | | DDT Node2: 192.0.2.12 | | authoritative: | | authoritative: | | 2001:db8::/32 | | 2001:db8::/32 | +-----------------------+ +-----------------------+ | \ / | | \/ | | /\ | | / \ | | / \ | V V V V +--------------------------+ +------------------------+ | Map-Server1: 192.0.2.101 | | DDT Node3: 192.0.2.201 | | authoritative: | | authoritative: | | 2001:db8:0100::/40 | | 2001:db8:0500::/40 | | site1: 2001:db8:0103::/48| +------------------------+ | site2: 2001:db8:0104::/48| | | +--------------------------+ | | V V +---------------------------+ +---------------------------+ | Map-Server2: 192.0.2.211 | | Map-Server3: 192.0.2.221 | | authoritative: | | authoritative: | | 2001:db8:0500::/48 | | 2001:db8:0501::/48 | |site3: 2001:db8:0500:1::/64| |site5: 2001:db8:0501:8::/64| |site4: 2001:db8:0500:2::/64| |site6: 2001:db8:0501:9::/64| +---------------------------+ +---------------------------+ Figure 3: Example of DDT tree topology. DDT Nodes are configured for this "root" at IP addresses 192.0.2.1 and 192.0.2.2. DDT Map-Resolvers are configured with default referral cache entries for these addresses. The root DDT Nodes delegate 2001:db8::/32 to two DDT Nodes with IP addresses 192.0.2.11 and 192.0.2.12. The DDT Nodes for 2001:db8::/32 delegate 2001:db8:0100::/40 to a DDT Map-Server with RLOC 192.0.2.101. Saucez & Iannone Expires 24 April 2025 [Page 29] Internet-Draft LISP-DDT October 2024 The DDT Map-Server for 2001:db8:0100::/40 is configured to allow ETRs to register the sub-prefixes 2001:db8:0103::/48 and 2001:db8:0104::/48. The DDT Nodes for 2001:db8::/32 also delegate 2001:db8:0500::/40 to a DDT Node with RLOC 192.0.2.201. The DDT Node for 2001:db8:0500::/40 is further configured to delegate 2001:db8:0500::/48 to a DDT Map-Server with RLOC 192.0.2.211 and 2001:db8:0501::/48 to a DDT Map-Server with RLOC 192.0.2.221. The DDT Map-Server for 2001:db8:0500::/48 is configured to allow ETRs to register the sub-prefixes 2001:db8:0500:1::/64 and 2001:db8:0500:2::/64. The DDT Map-Server for 2001:db8:0501::/48 is configured to allow ETRs to register the sub-prefixes 2001:db8:0501:8::/64 and 2001:db8:0501:9::/64. 8.1. Lookup of 2001:db8:0103:1::1/128 The first example shows a DDT Map-Resolver following a delegation from the root to a DDT Node followed by another delegation to a DDT Map-Server. ITR1 sends an Encapsulated Map-Request for 2001:db8:0103:1::1 to one of its configured (DDT) Map-Resolvers. The DDT Map-Resolver proceeds as follows: 1. Send a DDT Map-Request (for 2001:db8:0103:1::1) to one of the root DDT Nodes (192.0.2.1 or 192.0.2.2). 2. Receive (and save in the referral cache) the Map-Referral for EID-prefix 2001:db8::/32, action code NODE-REFERRAL, RLOC set (192.0.2.11, 192.0.2.12). 3. Send a DDT Map-Request to 192.0.2.11 or 192.0.2.12. 4. Receive (and save in the referral cache) the Map-Referral for EID-prefix 2001:db8:0100::/40, action code MS-REFERRAL, RLOC set (192.0.2.101). 5. Send a DDT Map-Request to 192.0.2.101; if the ITR-originated Encapsulated Map-Request had a LISP-SEC signature, it is included. Saucez & Iannone Expires 24 April 2025 [Page 30] Internet-Draft LISP-DDT October 2024 6. The DDT Map-Server at 192.0.2.101 decapsulates the DDT Map- Request and forwards the Map-Request to a registered site1 ETR for 2001:db8:0103::/48. 7. The DDT Map-Server at 192.0.2.101 sends a Map-Referral message for EID-prefix 2001:db8:0103::/48, action code MS-ACK, to the DDT Map-Resolver. 8. The DDT Map-Resolver receives the Map-Referral message and dequeues the pending request for 2001:db8:0103:1::1. 9. The site1 ETR for 2001:db8:0103::/48 receives the Map-Request forwarded by the DDT Map-Server and sends a Map-Reply to ITR1. 8.2. Lookup of 2001:db8:0501:8:4::1/128 The next example shows a three-level delegation: root to first DDT node, first DDT Node to second DDT Node, and second DDT Node to DDT Map-Server. ITR2 sends an Encapsulated Map-Request for 2001:db8:0501:8:4::1 to one of its configured (DDT) Map-Resolvers, which are different from those for ITR1. The DDT Map-Resolver proceeds as follows: 1. Send a DDT Map-Request (for 2001:db8:0501:8:4::1) to one of the root DDT Nodes (192.0.2.1 or 192.0.2.2). 2. Receive (and save in the referral cache) the Map-Referral for EID-prefix 2001:db8::/32, action code NODE-REFERRAL, RLOC set (192.0.2.11, 192.0.2.12). 3. Send a DDT Map-Request to 192.0.2.11 or 192.0.2.12. 4. Receive (and save in the referral cache) the Map-Referral for EID-prefix 2001:db8:0500::/40, action code NODE-REFERRAL, RLOC set (192.0.2.201). 5. Send a DDT Map-Request to 192.0.2.201. 6. Receive (and save in the referral cache) the Map-Referral for EID-prefix 2001:db8:0501::/48, action code MS-REFERRAL, RLOC set (192.0.2.221). 7. Send a DDT Map-Request to 192.0.2.221; if the ITR-originated Encapsulated Map-Request had a LISP-SEC signature, it is included. Saucez & Iannone Expires 24 April 2025 [Page 31] Internet-Draft LISP-DDT October 2024 8. The DDT Map-Server at 192.0.2.221 decapsulates the DDT Map- Request and forwards the Map-Request to a registered site5 ETR for 2001:db8:0501:8::/64. 9. The DDT Map-Server at 192.0.2.221 sends a Map-Referral message for EID-prefix 2001:db8:0501:8::/64, action code MS-ACK, to the DDT Map-Resolver. 10. The DDT Map-Resolver receives a Map-Referral(MS-ACK) message and dequeues the pending request for 2001:db8:0501:8:4::1. 11. The site5 ETR for 2001:db8:0501:8::/64 receives a Map-Request forwarded by the DDT Map-Server and sends a Map-Reply to ITR2. 8.3. Lookup of 2001:db8:0104:2::2/128 This example shows how a DDT Map-Resolver uses a saved referral cache entry to skip the referral process and go directly to a DDT Map- Server for a prefix that is similar to one previously requested. In this case, ITR1 uses the same Map-Resolver used in the example in Section 8.1. It sends an Encapsulated Map-Request for 2001:db8:0104:2::2 to that (DDT) Map-Resolver. The DDT Map-Resolver finds an MS-REFERRAL cache entry for 2001:db8:0100::/40 with RLOC set (192.0.2.101) and proceeds as follows: 1. Send a DDT Map-Request (for 2001:db8:0104:2::2) to 192.0.2.101; if the ITR-originated Encapsulated Map-Request had a LISP-SEC signature, it is included. 2. The DDT Map-Server at 192.0.2.101 decapsulates the DDT Map- Request and forwards the Map-Request to a registered site2 ETR for 2001:db8:0104::/48. 3. The DDT Map-Server at 192.0.2.101 sends a Map-Referral message for EID-prefix 2001:db8:0104::/48, action code MS-ACK, to the DDT Map-Resolver. 4. The DDT Map-Resolver receives the Map-Referral (MS-ACK) and dequeues the pending request for 2001:db8:0104:2::2. 5. The site2 ETR for 2001:db8:0104::/48 receives a Map-Request and sends a Map-Reply to ITR1. Saucez & Iannone Expires 24 April 2025 [Page 32] Internet-Draft LISP-DDT October 2024 8.4. Lookup of 2001:db8:0500:2:4::1/128 This example shows how a DDT Map-Resolver uses a saved referral cache entry to start the referral process at a non-root, intermediate DDT node for a prefix that is similar to one previously requested. In this case, ITR2 uses the same Map-Resolver used in the example in Section 8.1. It sends an Encapsulated Map-Request for 2001:db8:0500:2:4::1 to that (DDT) Map-Resolver, which finds a NODE- REFERRAL cache entry for 2001:db8:0500::/40 with RLOC set (192.0.2.201). It proceeds as follows: 1. Send a DDT Map-Request (for 2001:db8:0500:2:4::1) to 192.0.2.201. 2. Receive (and save in the referral cache) the Map-Referral for EID-prefix 2001:db8:0500::/48, action code MS-REFERRAL, RLOC set (192.0.2.211). 3. Send a DDT Map-Request to 192.0.2.211; if the ITR-originated Encapsulated Map-Request had a LISP-SEC signature, it is included. 4. The DDT Map-Server at 192.0.2.211 decapsulates the DDT Map- Request and forwards the Map-Request to a registered site4 ETR for 2001:db8:0500:2::/64. 5. The DDT Map-Server at 192.0.2.211 sends a Map-Referral message for EID-prefix 2001:db8:0500:2::/64, action code MS-ACK, to the DDT Map-Resolver. 6. The DDT Map-Resolver receives the Map-Referral (MS-ACK) and dequeues the pending request for 2001:db8:0500:2:4::1. 7. The site4 ETR for 2001:db8:0500:2::/64 receives a Map-Request and sends a Map-Reply to ITR2. 8.5. Lookup of 2001:db8:0500::1/128 (Nonexistent EID) This example uses the cached MS-REFERRAL for 2001:db8:0500::/48 learned above to start the lookup process at the DDT Map-Server at 192.0.2.211. The DDT Map-Resolver proceeds as follows: 1. Send a DDT Map-Request (for 2001:db8:0500::1) to 192.0.2.211; if the ITR-originated Encapsulated Map-Request had a LISP-SEC signature, it is included. Saucez & Iannone Expires 24 April 2025 [Page 33] Internet-Draft LISP-DDT October 2024 2. The DDT Map-Server at 192.0.2.211, which is authoritative for 2001:db8:0500::/48, does not have a matching delegation for 2001:db8:0500::1. It responds with a Map-Referral message for 2001:db8:0500::/64, action code DELEGATION-HOLE, to the DDT Map- Resolver. The prefix 2001:db8:0500::/64 is used because it is the least-specific prefix that does match the requested EID but does not match one of the configured delegations (2001:db8:0500:1::/64 and 2001:db8:0500:2::/64). 3. The DDT Map-Resolver receives the delegation, adds a negative referral cache entry for 2001:db8:0500::/64, dequeues the pending request for 2001:db8:0500::1, and returns a Negative Map-Reply to ITR2. 9. Securing the Database and Message Exchanges This section specifies the DDT security architecture that provides data origin authentication, data integrity protection, and XEID- prefix delegation. Global XEID-prefix authorization is out of scope for this document. Each DDT Node is configured with one or more public/private key pairs that are used to digitally sign Map-Referral Records for XEID- prefix(es) for which the DDT Node is authoritative. In other words, each public/private key pair is associated with the combination of a DDT Node and an XEID-prefix for which it is authoritative. Every DDT Node is also configured with the public keys of its child DDT Nodes. By including the public keys of target child DDT Nodes in the Map- Referral Records and signing each Record with the DDT Node's private key, a DDT Node can securely delegate sub-prefixes of its authoritative XEID-prefixes to its child DDT nodes. A DDT Node configured to provide hints must also have the public keys of the DDT Nodes to which its hints point. DDT Node keys can be encoded using LCAF Type 11 to associate the key to the RLOC of the referred DDT Node. If a node has more than one public key, it should sign its Records with at least one of these keys. When a node has N keys, it can sustain up to N-1 key compromises. The revocation mechanism is described in Section 9.2.1. Map-Resolvers are configured with one or more trusted public keys, referred to as "trust anchors". Trust anchors are used to authenticate the DDT security infrastructure. Map-Resolvers can discover a DDT Node's public key by either (1) having it configured as a trust anchor or (2) obtaining it from the node's parent as part of a signed Map-Referral. When a public key is obtained from a node's parent, it is considered trusted if it is signed by a trust anchor or if it is signed by a key that was previously trusted. Typically, in a Map-Resolver, the root DDT Node's public keys should Saucez & Iannone Expires 24 April 2025 [Page 34] Internet-Draft LISP-DDT October 2024 be configured as trust anchors. Once a Map-Resolver authenticates a public key, it locally caches the key along with the associated DDT node RLOC and XEID-prefix for future use. 9.1. XEID-Prefix Delegation In order to delegate XEID sub-prefixes to its child DDT Nodes, a parent DDT Node signs its Map-Referrals. Every signed Map-Referral MUST also include the public keys associated with each child DDT node. Such a signature indicates that the parent DDT Node is delegating the specified XEID-prefix to a given child DDT Node. The signature is also authenticating the public keys associated with the child DDT Nodes, and authorizing them to be used by the child DDT nodes, to provide origin authentication and integrity protection for further delegations and mapping information of the XEID-prefix allocated to the DDT Node. As a result, for a given XEID-prefix, a Map-Resolver can form an authentication chain from a configured trust anchor (typically the root DDT Node) to the leaf nodes (Map-Servers). Map-Resolvers leverage this authentication chain to verify the Map-Referral signatures while walking the DDT tree until they reach a Map-Server authoritative for the given XEID-prefix. 9.2. DDT Node Operation Upon receiving a Map-Request, the DDT Node responds with a Map- Referral as specified in Section 6. For every Record present in the Map-Referral, the DDT Node also includes the public keys associated with the Record's XEID-prefix and the RLOCs of the child DDT Nodes. Each Record contained in the Map-Referral is signed using the DDT Node's private key. 9.2.1. DDT Public Key Revocation The node that owns a public key can also revoke that public key. For instance, if a parent DDT Node advertises a public key for one of its child DDT Nodes, the child DDT Node can at a later time revoke that key. Since DDT Nodes do not keep track of the Map-Resolvers that query them, revocation is done in a pull model, where the Map- Resolver is informed of the revocation of a key only when it queries the node that owns that key. If the parent DDT Node is configured to advertise that key, the parent DDT Node must also be signaled to remove the key from the Records it advertises for the child DDT Node; this is necessary to avoid further distribution of the revoked key. Saucez & Iannone Expires 24 April 2025 [Page 35] Internet-Draft LISP-DDT October 2024 To securely revoke a key, the DDT Node creates a new Record for the associated XEID-prefix and locator, including the revoked key with the R bit set. (See Section 4.7 of [RFC8060] for details regarding the R bit.) The DDT Node must also include a signature in the Record that covers this Record; this is computed using the private key corresponding to the key being revoked. Such a Record is termed a "revocation record". By including this Record in its Map-Referrals, the DDT Node informs querying Map-Resolvers about the revoked key. A digital signature computed with a revoked key can only be used to authenticate the revocation and SHOULD NOT be used to validate any data. To prevent a compromised key from revoking other valid keys, a given key can only be used to sign a revocation for that specific key; it cannot be used to revoke other keys. This prevents the use of a compromised key to revoke other valid keys as described in [RFC5011]. A revocation record MUST be advertised for a period of time equal to or greater than the TTL value of the Record that initially advertised the key, starting from the time that the advertisement of the key was stopped by removal from the parent DDT Node. 9.3. Map-Server Operation Similar to a DDT Node, a Map-Server is configured with one or more public/private key pairs that it must use to sign Map-Referrals. However, unlike DDT Nodes, Map-Servers do not delegate prefixes and as a result do not need to include keys in the Map-Referrals they generate. 9.4. Map-Resolver Operation Upon receiving a Map-Referral, the Map-Resolver MUST first verify the signature(s) by using either a trust anchor or a previously authenticated public key associated with the DDT Node sending the Map-Referral. If multiple authenticated keys are associated with the DDT Node sending this Map-Referral, the Key Tag field (Section 5.4.1) of the signature can be used to select the correct public key for verifying the signature. If the key tag matches more than one key associated with that DDT Node, the Map-Resolver MUST try to verify the signature with all matching keys. For every matching key that is found, the Map-Resolver MUST also verify that the key is authoritative for the XEID-prefix in the Map-Referral Record. If such a key is found, the Map-Resolver MUST use it to verify the associated signature in the Record. If (1) no matching key is found, (2) none of the matching keys is authoritative for the XEID-prefix in the Map-Referral Record, or (3) such a key is found but the signature is not valid, the Map-Referral Record is considered corrupted and MUST be discarded. This may be due to expired keys. The Map- Saucez & Iannone Expires 24 April 2025 [Page 36] Internet-Draft LISP-DDT October 2024 Resolver MAY try other siblings of this node if there is an alternate node that is authoritative for the same prefix. If not, the Map- Resolver CAN query the DDT Node's parent to retrieve a valid key. It is good practice to use a counter or timer to avoid repeating this process if the Map-Resolver cannot verify the signature after several attempts. Once the signature is verified, the Map-Resolver has verified the XEID-prefix delegation in the Map-Referral. This also means that public keys of the child DDT Nodes were authenticated; the Map- Resolver must add these keys to the authenticated keys associated with each child DDT Node and XEID-prefix. These keys are considered valid for the duration specified in the Record's TTL field. 10. Deployment Experience TBD 11. IANA Considerations IANA has made the an early temporary allocation for message type 6, "LISP DDT Map-Referral", in the "LISP Packet Types" registry group. IANA is requested to make the allocation permanent and modify the "LISP Packet Types" as shown in Table 3. +======+=======================+=================+ | Code | Message | Reference | +======+=======================+=================+ | 6 | LISP DDT Map-Referral | [This document] | +------+-----------------------+-----------------+ Table 3: LISP DDT Map-Referral Message Type Allocation 12. Security Considerations Section 9 describes a DDT security architecture that provides data origin authentication, data integrity protection, and XEID-prefix delegation within the DDT infrastructure. This document specifies how DDT security and LISP-SEC [RFC9303] complement one another to secure the DDT infrastructure, Map-Referral messages, and the Map-Request/Map-Reply protocols. LISP-SEC can use the DDT public-key infrastructure to secure the transport of LISP-SEC key material (the One-Time Key) from a Map- Resolver to the corresponding Map-Server. For this reason, when LISP-SEC is deployed in conjunction with a LISP-DDT mapping database Saucez & Iannone Expires 24 April 2025 [Page 37] Internet-Draft LISP-DDT October 2024 and the path between the Map-Resolver and Map-Server needs to be protected, DDT security as described in Section 9 MUST be enabled as well. 13. References 13.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC) Trust Anchors", STD 74, RFC 5011, DOI 10.17487/RFC5011, September 2007, . [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, February 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9300] Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A. Cabellos, Ed., "The Locator/ID Separation Protocol (LISP)", RFC 9300, DOI 10.17487/RFC9300, October 2022, . [RFC9301] Farinacci, D., Maino, F., Fuller, V., and A. Cabellos, Ed., "Locator/ID Separation Protocol (LISP) Control Plane", RFC 9301, DOI 10.17487/RFC9301, October 2022, . [RFC9303] Maino, F., Ermagan, V., Cabellos, A., and D. Saucez, "Locator/ID Separation Protocol Security (LISP-SEC)", RFC 9303, DOI 10.17487/RFC9303, October 2022, . 13.2. Informative References [AFI] IANA, "Address Family Numbers", . Saucez & Iannone Expires 24 April 2025 [Page 38] Internet-Draft LISP-DDT October 2024 [RFC6836] Fuller, V., Farinacci, D., Meyer, D., and D. Lewis, "Locator/ID Separation Protocol Alternative Logical Topology (LISP+ALT)", RFC 6836, DOI 10.17487/RFC6836, January 2013, . [RFC6837] Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to Routing Locator (RLOC) Database", RFC 6837, DOI 10.17487/RFC6837, January 2013, . [RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch, "PKCS #1: RSA Cryptography Specifications Version 2.2", RFC 8017, DOI 10.17487/RFC8017, November 2016, . [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. Smirnov, "Locator/ID Separation Protocol Delegated Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, May 2017, . Contributors Vince Fuller VAF.NET Internet Consulting Email: vince.fuller@gmail.com Darrel Lewis ICANN Los Angeles, CA 90292 United States of America Email: darrel.lewis@icann.org Vina Ermagan Google United States of America Email: ermagan@gmail.com Amit Jain Juniper Networks Email: atjain@juniper.net Saucez & Iannone Expires 24 April 2025 [Page 39] Internet-Draft LISP-DDT October 2024 Anton Smirnov Cisco Systems, Inc. De Kleetlaan 6a 1831 Diegem Belgium Email: as@cisco.com Authors' Addresses Damien Saucez (editor) Inria France Email: damien.saucez@inria.fr Luigi Iannone (editor) Huawei Technologies France S.A.S.U. 18, Quai du Point du Jour 92100 Boulogne-Billancourt France Email: luigi.iannone@huawei.com Saucez & Iannone Expires 24 April 2025 [Page 40]