Network Working Group                                          V. FullerInternet-DraftIntended status: Experimental                                   D. LewisExpires: July 22, 2017                                        V. Ermagan                                                           Cisco Systems                                                                 A. Jain                                                        Juniper Networks                                                              A. Smirnov                                                           Cisco Systems                                                        January 18, 2017                      LISP Delegated Database Tree                         draft-ietf-lisp-ddt-09Abstract   This document describes the LISP Delegated Database Tree (LISP-DDT),   a hierarchical, distributed database which 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.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 http://datatracker.ietf.org/drafts/current/.   Internet-Drafts are draft documents valid for a maximum of six months   and may be updated, replaced, or obsoleted by other documents at any   time.  It is inappropriate to use Internet-Drafts as reference   material or to cite them other than as "work in progress."   This Internet-Draft will expire on July 22, 2017.Copyright Notice   Copyright (c) 2017 IETF Trust and the persons identified as the   document authors.  All rights reserved.Fuller, et al.            Expires July 22, 2017                 [Page 1]Internet-Draft        LISP Delegated Database Tree          January 2017   This document is subject to BCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4   3.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   5   4.  Database organization . . . . . . . . . . . . . . . . . . . .   7     4.1.  XEID prefixes . . . . . . . . . . . . . . . . . . . . . .   7     4.2.  DDT database tree structure . . . . . . . . . . . . . . .   7     4.3.  Configuring prefix delegation . . . . . . . . . . . . . .   8       4.3.1.  The root DDT node . . . . . . . . . . . . . . . . . .   9   5.  DDT Map-Request . . . . . . . . . . . . . . . . . . . . . . .   9   6.  The Map-Referral message  . . . . . . . . . . . . . . . . . .  10     6.1.  Action codes  . . . . . . . . . . . . . . . . . . . . . .  10     6.2.  Referral set  . . . . . . . . . . . . . . . . . . . . . .  11     6.3.  Incomplete flag . . . . . . . . . . . . . . . . . . . . .  11     6.4.  Map-Referral Message Format . . . . . . . . . . . . . . .  11       6.4.1.  SIG section . . . . . . . . . . . . . . . . . . . . .  14   7.  DDT network elements and their operation  . . . . . . . . . .  15     7.1.  DDT node  . . . . . . . . . . . . . . . . . . . . . . . .  15       7.1.1.  Match of a delegated prefix (or sub-prefix) . . . . .  15       7.1.2.  Missing delegation from an authoritative prefix . . .  16     7.2.  DDT Map Server  . . . . . . . . . . . . . . . . . . . . .  16     7.3.  DDT client  . . . . . . . . . . . . . . . . . . . . . . .  17       7.3.1.  Queuing and sending DDT Map-Requests  . . . . . . . .  17       7.3.2.  Receiving and following referrals . . . . . . . . . .  18       7.3.3.  Handling referral errors  . . . . . . . . . . . . . .  20       7.3.4.  Referral loop detection . . . . . . . . . . . . . . .  20   8.  Pseudo Code and Decision Tree diagrams  . . . . . . . . . . .  21     8.1.  Map Resolver processing of ITR Map-Request  . . . . . . .  21       8.1.1.  Pseudo-code summary . . . . . . . . . . . . . . . . .  21       8.1.2.  Decision tree diagram . . . . . . . . . . . . . . . .  21     8.2.  Map Resolver processing of Map-Referral message . . . . .  22       8.2.1.  Pseudo-code summary . . . . . . . . . . . . . . . . .  22       8.2.2.  Decision tree diagram . . . . . . . . . . . . . . . .  24     8.3.  DDT Node processing of DDT Map-Request message  . . . . .  25       8.3.1.  Pseudo-code summary . . . . . . . . . . . . . . . . .  25       8.3.2.  Decision tree diagram . . . . . . . . . . . . . . . .  27   9.  Example topology and request/referral following . . . . . . .  27Fuller, et al.            Expires July 22, 2017                 [Page 2]Internet-Draft        LISP Delegated Database Tree          January 2017     9.1.  Lookup of 2001:db8:0103:1::1/128  . . . . . . . . . . . .  30     9.2.  Lookup of 2001:db8:0501:8:4::1/128  . . . . . . . . . . .  31     9.3.  Lookup of 2001:db8:0104:2::2/128  . . . . . . . . . . . .  32     9.4.  Lookup of 2001:db8:0500:2:4::1/128  . . . . . . . . . . .  32     9.5.  Lookup of 2001:db8:0500::1/128 (non-existent EID) . . . .  33   10. Securing the database and message exchanges . . . . . . . . .  34     10.1.  XEID-prefix Delegation . . . . . . . . . . . . . . . . .  34     10.2.  DDT node operation . . . . . . . . . . . . . . . . . . .  35       10.2.1.  DDT public key revocation  . . . . . . . . . . . . .  35     10.3.  Map Server operation . . . . . . . . . . . . . . . . . .  36     10.4.  Map Resolver operation . . . . . . . . . . . . . . . . .  36   11. Open Issues and Considerations  . . . . . . . . . . . . . . .  37   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  37   13. Security Considerations . . . . . . . . . . . . . . . . . . .  37   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  38     14.1.  Normative References . . . . . . . . . . . . . . . . . .  38     14.2.  Informative References . . . . . . . . . . . . . . . . .  38   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  39   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  401.  Introduction   LISP [RFC6830] specifies an architecture and mechanism for replacing   the addresses currently used by IP with two separate name spaces:   Endpoint Identifiers (EIDs), used end-to-end for terminating   transport-layer associations, and Routing Locators (RLOCs), which are   bound to topological location, and are used for routing and   forwarding through the Internet infrastructure.   [RFC6833] specifies an interface between database storing EID-to-RLOC   mappings and LISP devices which need this information for packet   forwarding.  Internal organization of such database is out the scope   of [RFC6833].  Multiple architectures of the database have been   proposed, each having its advantages and disadvantages (see for   example [RFC6836] and [RFC6837]).   This document specifies architecture for database of LISP EID-to-RLOC   mappings with emphasis on high scalability.  LISP-DDT is a   hierarchical distributed database, which 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, which needs to locate a   given mapping, will follow a path through the tree-structured   database, contacting, one after another, the DDT nodes along that   path until it reaches the leaf DDT node(s) authoritative for the   mapping it is seeking.Fuller, et al.            Expires July 22, 2017                 [Page 3]Internet-Draft        LISP Delegated Database Tree          January 2017   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 (16   bits), and EID-prefix (variable, according to 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 also is   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 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 [RFC6833]   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 a new LISP message type, the Map-Referral, 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 6 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   preconfigured DDT node RLOC.  The DDT node responds with a Map-   Referral message that either indicates that it will find the   requested mapping to complete processing of the request or that 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.2.  Requirements Language   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described in [RFC2119].Fuller, et al.            Expires July 22, 2017                 [Page 4]Internet-Draft        LISP Delegated Database Tree          January 20173.  Definition of Terms   Extended EID (XEID):  a LISP EID extended with data uniquely      identifying address space to which it belongs, such as LISP      instance ID, Address Family etc.  See Section 4.1 for detailed      description of XEID data.   XEID-prefix:  Extended EID-prefix (XEID-prefix) is 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 prefix.   DDT node:  a network infrastructure component responsible for      specific XEID-prefix(es) and for 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 [RFC6833]), but it is also possible for an 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 proxy Map-Reply service) for a subset of its      delegated prefixes.  Map Server functions including proxying Map-      Replies are described in [RFC6833].   DDT Map Server peers:  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 returned reply as potentially incomplete.   DDT Map Resolver:  a network infrastructure element which implements      both the DDT client functionality and Map Resolver functionality      as defined by [RFC6833].  DDT Map Resolver accepts Map-Requests      from ITRs, sends DDT Map-Requests to DDT nodes and implements      iterative following of Map-Referrals.  Note that Map Resolvers do      not respond to clients which sent Map-Requests, they only ensure      that the Map-Request has been forwarded to a LISP device (ETR or      proxy Map-Server) which will provide authoritative response to the      original requestor.  A DDT Map Resolver will typically maintain a      cache of previously received Map-Referral message results      containing RLOCs for DDT nodes responsible for XEID- prefixes of      interest (termed the "referral cache").Fuller, et al.            Expires July 22, 2017                 [Page 5]Internet-Draft        LISP Delegated Database Tree          January 2017   Encapsulated Map-Request:  a LISP Map-Request carried within an      Encapsulated Control Message, which has an additional LISP header      prepended.  Sent to UDP destination port 4342.  The "outer"      addresses are globally-routable IP addresses, also known as RLOCs.      Used by an ITR when sending to a Map Resolver and by a Map Server      when forwarding a Map-Request to an ETR as documented in LISP-MS      [RFC6833].   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 7.3.1 describes how DDT Map-      Requests are sent.  Section 5 defines 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", a      set of RLOCs for DDT nodes that have information about the more      specific XEID prefix covering 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 even more specific XEID-prefix.  See      Section 7.1 and Section 7.3.2 for details on the sending and      processing of Map-Referral messages.   Negative Map-Referral:  an answer from an authoritative DDT node that      there is no mapping for the requested XEID.  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 Request 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 a XEID.  Each entry in the      list contains additional state needed by the referral following      process, including the XEID, requestor(s) of the XEID (typically,      one or more ITRs), saved information about the last referral      received and followed (matching XEID-prefix, action code, RLOC      set, index of last RLOC queried in the RLOC set), and any LISP-SEC      information ([I-D.ietf-lisp-sec]) that was included in the DDT      client Map-Request.  An entry in the list may be interchangeablyFuller, et al.            Expires July 22, 2017                 [Page 6]Internet-Draft        LISP Delegated Database Tree          January 2017      termed a "pending request list entry" or simply a "pending      request".   For definitions of other terms, notably Map-Request, Map-Reply,   Ingress Tunnel Router (ITR), Egress Tunnel Router (ETR), Map Server,   and Map Resolver, please consult the LISP specification [RFC6830] and   the LISP Mapping Service specification [RFC6833].4.  Database organization4.1.  XEID prefixes   DDT database is indexed by Extended EID-prefixes (XEID-prefixes).   XEID-prefix is LISP EID-prefix together with data extending it to   uniquely identify address space of the prefix.  XEID-prefix is   composed as binary encoding of five fields, in order of significance:   DBID (16 bits), Instance Identifier (IID, 32 bits), Address Family   Identifier (AFI, 16 bits), and EID-prefix (variable, according to AFI   value).  The fields are concatenated, with the most significant   fields as listed above.   DBID is LISP-DDT database ID, a 16-bit field provided to allow the   definition of multiple databases.  In this version of DDT DBID MUST   always be set to zero.  Other values of DBID are reserved for future   use.   Instance ID (IID) is 32-bit value describing context of EID prefix if   the latter is intended for use in an environment where addresses may   not be unique, such as on a Virtual Private Network where [RFC1918]   address space is used.  See "Using Virtualization and Segmentation   with LISP" in [RFC6830] for more discussion of Instance IDs.   Encoding of the instance ID (IID) is specified by   [I-D.ietf-lisp-lcaf].   Address Family Identifier (AFI) is a 16-bit value defining syntax of   EID-prefix.  AFI values are assigned by IANA ([AFI].4.2.  DDT database tree structure   LISP-DDT database of each DDT node is organised as a tree structure   that is indexed by XEID prefixes.  Leaves of the database tree   describe delegation of authority between DDT nodes (see more on   delegation and information kept in the database entries in   Section 4.3).   DDT Map-Requests sent by the DDT client to DDT nodes always contain   specific values for DBID, IID and AFI; never a range or unspecifiedFuller, et al.            Expires July 22, 2017                 [Page 7]Internet-Draft        LISP Delegated Database Tree          January 2017   value for any of these fields.  Thus XEID prefix used as key for   search in the database tree will have length of at least 64 bits.   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 length less, equal 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 which 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 which 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   knowledge of the XEID-prefix, and accompanying security information   (for details of security infomation exchange and its use see   Section 10).  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 answer, if it provides proxy Map-Reply service) Map-   Requests.   XEID prefix (or prefixes) for which DDT node is authoritative and   delegation of authority for sub-prefixes is provided as configuration   of the DDT node.  Implementations will likely develop a language to   express this prefix authority and delegation.  Since DDT   configuration is static (i.e. not exchanged between DDT nodes as part   of the protocol itself) such language is implementation-dependant and   is outside the scope of this specification.Fuller, et al.            Expires July 22, 2017                 [Page 8]Internet-Draft        LISP Delegated Database Tree          January 20174.3.1.  The root DDT node   The root DDT node is the logical "top" of the distributed database   hierarchy.  It is authoritative for all XEID prefixes, that is 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 8 for formal description of conditions   when DDT Request is forwarded to the root node).  The root node in a   particular instantiation of LISP-DDT therefore MUST be configured   with delegations for at least all defined IIDs and AFIs.5.  DDT Map-Request   A DDT client (usualy a Map Resolver) uses LISP Encapsulated Control   Message (ECM) to send Map-Request to a DDT node.  Format of the ECM   is defined by [RFC6830].  This specification adds to ECM flag "DDT-   originated".        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       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     / |                       IPv4 or IPv6 Header                     |   OH  |                      (uses RLOC addresses)                    |     \ |                                                               |       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     / |       Source Port = xxxx      |       Dest Port = 4342        |   UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     \ |           UDP Length          |        UDP Checksum           |       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   LH  |Type=8 |S|D|                Reserved                           |       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     / |                       IPv4 or IPv6 Header                     |   IH  |                  (uses RLOC or EID addresses)                 |     \ |                                                               |       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     / |       Source Port = xxxx      |       Dest Port = yyyy        |   UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     \ |           UDP Length          |        UDP Checksum           |       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   LCM |                      LISP Control Message                     |       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   D: The "DDT-originated" flag.  It is set by a DDT client to indicate      that the receiver SHOULD return Map-Referral messages as      appropriate.  Use of the flag is further described in      Section 7.3.1.  This bit is allocated from LISP message header      bits marked as Reserved in [RFC6830].Fuller, et al.            Expires July 22, 2017                 [Page 9]Internet-Draft        LISP Delegated Database Tree          January 20176.  The Map-Referral message   This specification defines a new LISP message, the Map-Referral.  It   is sent by a DDT node to a DDT client in response to a DDT Map-   Request message.  See Section 6.4 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.6.1.  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, that is used by a      DDT client to "follow" the referral.   MS-REFERRAL (1):  indicates that the replying DDT node has delegated      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 7.3.2).   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      which 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 7.1.2 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 databaseFuller, et al.            Expires July 22, 2017                [Page 10]Internet-Draft        LISP Delegated Database Tree          January 2017      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 DDT node MUST provide EID-prefix received in the      request and the TTL MUST be set to 0.6.2.  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.6.3.  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:   o  If it is setting action code MS-ACK or MS-NOT-REGISTERED but the      matching XEID-prefix is not flagged in configuration as      "complete".  XEID-prefix configuration on DDT Mapping Server      SHOULD be marked as "complete" when 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 local DDT node is      the only one authoritative for the XEID-prefix.   o  If it is setting action code NOT-AUTHORITATIVE.6.4.  Map-Referral Message FormatFuller, et al.            Expires July 22, 2017                [Page 11]Internet-Draft        LISP Delegated Database Tree          January 2017        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                          ~   +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Type: Type value 6 was reserved for future use in RFC6830, this   document allocates this value to identify Map-Referral messages.   ACT: The "action" field of the mapping record in a Map-Referral   message encodes one of the 6 action types: NODE-REFERRAL, MS-   REFERRAL, MS-ACK, MS-NOT-REGISTERED, DELEGATION-HOLE, NOT-   AUTHORITATIVE.  See Section 6.1 for description of their meaning.   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 Type field as follows:Fuller, et al.            Expires July 22, 2017                [Page 12]Internet-Draft        LISP Delegated Database Tree          January 2017   -------------------------------------------------------------------    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   -------------------------------------------------------------------   *: The "Incomplete" flag setting on Map Server originated referral of      MS-ACK and MS-NOT-REGISTERED types depend 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.      Incomplete bit is not set when the Map Server has encoded the      information, which means the referral-set includes all the RLOCs      of all Map Servers that serve the prefix.  It MUST be set when      configuration of the Map Server does not flag 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, it is   equal to the number of Ref sections in the message.   SigCnt: Indicates the number of signatures (sig section) present in   the Record.  If SigCnt is larger than 0, the signature information   captured in a sig section as described in Section 6.4.1 will be   appended to the end of the record.  The number of sig sections at the   end of the Record MUST match the SigCnt.  Note that bits occupied by   SigCnt were Reserved in Records embedded into messages defined by   [RFC6830] and were required to be set to zero.   Loc-AFI: AFI of the Locator field.  If AFI value is different from   LCAF AFI, security keys are not included in the record.  If AFI is   equal to the 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 can   use this LCAF Type to include public keys associated with their Child   DDT nodes for a XEID-prefix referral record.  LCAF types and formats   are defined in [I-D.ietf-lisp-lcaf].Fuller, et al.            Expires July 22, 2017                [Page 13]Internet-Draft        LISP Delegated Database Tree          January 2017   Locator: RLOC of a DDT node the DDT client is being referred to.   Lenght of this variable-length field is determined by the Loc-AFI.   All other fields and their descriptions are equivalent to those in   the Map-Reply message, as defined in LISP [RFC6830].  Note, though,   that the set of RLOCs correspond to the DDT node to be queried as a   result of the referral not the RLOCs for an actual EID-to-RLOC   mapping.6.4.1.  SIG section   SigCnt counts the number of signature sections that appear at the end   of the Record.  Format of the signature section is described below.       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      /|                      Original Record TTL                      |     / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    /  |                      Signature Expiration                     |   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   s   |                      Signature Inception                      |   i   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   g   |            Key Tag            |           Sig Length          |   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   \   | Sig-Algorithm |    Reserved   |            Reserved           |    \  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+     \ ~                             Signature                         ~       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Original Record TTL: The original Record TTL for this record that is   covered by the signature.  Record TTL is in minutes.   Signature Expiration and Inception: Specify the validity 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 1.  Implementation conforming to thisFuller, et al.            Expires July 22, 2017                [Page 14]Internet-Draft        LISP Delegated Database Tree          January 2017   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  | [RFC3447] | DEPRECATED |          |               |            |           |            |          |       2       | RSA-SHA256 | [RFC3447] | MANDATORY  |          +---------------+------------+-----------+------------+                       Table 1: Sig-Algorithm Values   Reserved: This field MUST be set to 0 on transmit and MUST be ignored   on receipt.   Signature: Contains the cryptographic signature that covers the   entire referral record that this signature belongs to.  The Record   TTL is set to Original Record TTL and the sig fields are Signature   field is set to zero for the purpose of computing the Signature.7.  DDT network elements and their operation   As described above, DDT introduces a new network element, the "DDT   node", 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 as follows.7.1.  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 acts as follows:7.1.1.  Match 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 10 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.Fuller, et al.            Expires July 22, 2017                [Page 15]Internet-Draft        LISP Delegated Database Tree          January 2017   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 may be a useful heuristic for reducing the number of   iterations needed to find an EID, particular for private network   deployments.   Referral hints, if used properly, may reduce number of referrals a   DDT client needs to follow to locate DDT Map Server authoritative for   XEID prefix being resolved.  On the other hand, incorrect use of   hints may create circular dependencies between DDT nodes (or   "referral loops").  DDT client MUST be prepared to handle such   circular referrals.  See Section 7.3.4 for discussion of referral   loops and measures DDT client must implement in order to detect   circular referrals and prevent infinite looping.   Another danger with use of hints is when DDT deployment spans   multiple administrative domains (i.e. different authorities manage   DDT nodes in the same DDT database).  In this case 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.7.1.2.  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; this 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 negative Map-Referral   with action code NOT-AUTHORITATIVE MUST be returned.7.2.  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:   o  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 proxy Map-Fuller, et al.            Expires July 22, 2017                [Page 16]Internet-Draft        LISP Delegated Database Tree          January 2017      Reply service) and a Map-Referral with the MS-ACK action MUST be      returned to the sender of the DDT Map-Request.   o  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.7.3.  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 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.  Unlike a Map Resolver that uses the ALT   mapping system (see [RFC6836]), however, a DDT Map Resolver   implements a DDT client functionality to find the correct ETR to   answer a Map-Request; this requires a DDT Map Resolver to maintain   additional state: a Map-Referral cache and pending request list of   XEIDs that are going through the iterative referral process.   DDT client functionality may be implemented on ITRs.  In this case   the DDT client will not receive Map-Request from another network   element; instead, equivalent information will be provided to the DDT   client by the means of programming interface.7.3.1.  Queuing and sending DDT Map-Requests   When a DDT client receives a request to resolve XEID (in case of DDT   Map Resolver this will be in the form of 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 case of DDT   Map-Resolved, 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 alsoFuller, et al.            Expires July 22, 2017                [Page 17]Internet-Draft        LISP Delegated Database Tree          January 2017   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 absolutely required to cache   referrals, but it doing so decreases latency and reduces lookup   delays.   Note that in normal use on the public Internet, the statically-   configured initial referral cache for a DDT client should include a   "default" entry with RLOCs for either the DDT root node or one or   more DDT nodes that contain hints for the DDT root node.  If a DDT   client does not have such 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.  While this may be desirable on private   network deployments or during early transition to LISP when few sites   are using it, this behavior is not appropriate when LISP is in   general use on the Internet.  If DDT message exchange is   authenticated as described in Section 10 then 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 DDT root node.7.3.2.  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 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 DDT client returns no response to 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      as described in Section 7.3.4.  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 listedFuller, et al.            Expires July 22, 2017                [Page 18]Internet-Draft        LISP Delegated Database Tree          January 2017      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 10 for details on      security).   MS-ACK:  This 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 doing proxy service for the prefix then 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 re-send the DDT Map-Request with LISP-SEC information      included and the pending request queue entry remains until another      Map-Referral with MS-ACK action code 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      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 (in case of DDT Map Resolver to the sender of      original Map-Request); this Map-Reply contains the least-specific      XEID-prefix in the range for which this DDT Map Server is      autoritative and no registrations exist and whose TTL value SHOULD      be set to one minute.  A negative referral cache entry is created      for the prefix (whose TTL also SHOULD be set to one 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 it does not      exist in the mapping database.  The DDT client MUST return a      negative Map-Reply to the requester (in case of DDT Map Resolver      to the sender of original Map-Request); this Map-Reply SHOULD      indicate the least-specific XEID-prefix matching the requestedFuller, et al.            Expires July 22, 2017                [Page 19]Internet-Draft        LISP Delegated Database Tree          January 2017      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 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 re-try 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 a 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 requestor.7.3.3.  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 (in case of DDT Map Resolver to   the sender of original Map-Request).  Alternatively, if 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.7.3.4.  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 that 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 7.3.3.  Otherwise, the DDT client saves the most recentlyFuller, et al.            Expires July 22, 2017                [Page 20]Internet-Draft        LISP Delegated Database Tree          January 2017   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.8.  Pseudo Code and Decision Tree diagrams   To illustrate 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 "psuedo-code" and   then in the form of a decision tree.8.1.  Map Resolver processing of ITR Map-Request8.1.1.  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 request to map-server    } else {        store & fwd DDT request w/o security material to node delegation    }8.1.2.  Decision tree diagramFuller, et al.            Expires July 22, 2017                [Page 21]Internet-Draft        LISP Delegated Database Tree          January 2017   +------------+   | Is Request | Yes   |            |----> Replace old request with   |  Pending?  |      new nonce for future requests   +------------+         |         |No         |         V   +------------+   | Match In   | No   | Referral   |----> Send Negative Map-Reply   | cache?     |      (not a likely event as root or   +------------+       hint configured on every MR)         |         |Yes         |         V   +------------+   | Match Type | Yes   | Delegation |----> Send Negative Map-Reply   | Hole?     |   +------------+         |         |No         |         V   +------------+   | Match Type | Yes   | MS-ACK?    |----> Forward DDT Map-request to Map-Server   |            |   +------------+         |         |No         |         V   Store request & Fwd DDT Request w/o security material    to DDT node delegation8.2.  Map Resolver processing of Map-Referral message8.2.1.  Pseudo-code summary      if ( authentication signature validation failed ) {          silently drop      }      if ( no request pending matched by referral nonce ) {Fuller, et al.            Expires July 22, 2017                [Page 22]Internet-Draft        LISP Delegated Database Tree          January 2017          silently drop      }      if ( pfx in referral less specific than last referral used ) {          if ( gone through root ) {              silently drop          } else {              send request to root          }      }      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:Fuller, et al.            Expires July 22, 2017                [Page 23]Internet-Draft        LISP Delegated Database Tree          January 2017              if ( security material stripped ) {                  resend request with security material                  if { !incomplete } {                      cache                  }              }          case MS_NOT_REGISTERED:              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          }      }8.2.2.  Decision tree diagram                          +----------------+                          | Auth Signature | No                          |     Valid?     |----> Silently drop                          +----------------+                                  | Yes                                  V                            +------------+                            | Is Request | No                            |  Pending?  |----> Silently drop                            +------------+                                  | Yes                                  V                    +------------------------------+ Yes                    | Pfx less specific than last? |----> Silently drop                    +------------------------------+                                  |No                                  V       +---------------------------------------------------+       |             What is Map-Referral Type?            |--UNKNOWN-+       +---------------------------------------------------+          |         |        |         |       |         |          |            VFuller, et al.            Expires July 22, 2017                [Page 24]Internet-Draft        LISP Delegated Database Tree          January 2017         |        |         |       |         |       DEL_HOLE      DROP         |        |         |       |      MS_ACK        |         |        |         |       |         |          V         |        |     MS_REF   NODE_REF     |      Cache & return         |        |         |       |         V      negative map-reply         |        |         |       |    +---------+         |   NOT_AUTH       |       |    | Was sec | Yes         |        |         |       |    | material|         |        |         |       |    |Stripped?|----> Done         |        |         V       V    +---------+         |        |       +------------+      | No         |        |   Yes | Pfx equal  |      VMS_NOT_REGISTERED |   +---| to last    |  +------------+         |        |   |   | used?      |  | Incomplete | Yes         |        |   |   +------------+  | bit set?   |---> Resend DDT         |        V   V          |No      +------------+     request w         |  +------------+       |               |No         security         |  |  Gone      |       V               |           material         |  |  Through   |   Cache & follow      V         |  |  Root?     |   the referral     Cache & resend DDT         |  +------------+                    request with         |    |No      |Yes                   security material         |    |        |         |    V        V         |  Send req   Send negative map-reply         |  to root         V +-----------+ Yes                        +-----------+ Yes | Other MS  |----Follow other MS-------->|Incomplete |----> Don't cache | not tried?|                            |bit set?   | |           |---Send negative map-reply->|           |----> Cache +-----------+ No                         +-----------+ No8.3.  DDT Node processing of DDT Map-Request message8.3.1.  Pseudo-code summaryFuller, et al.            Expires July 22, 2017                [Page 25]Internet-Draft        LISP Delegated Database Tree          January 2017    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 minuteFuller, et al.            Expires July 22, 2017                [Page 26]Internet-Draft        LISP Delegated Database Tree          January 20178.3.2.  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 map    |----> Return MS_REFERRAL |            |     | 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|       |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       |No               +--> Return MS_NOT_REGISTERED       |                      Incomplete = 1       V                      ttl = Default_Negative_Referral_Ttl Return DELEGATION_HOLE  ttl = Default_Negative_Referral_Ttl9.  Example topology and request/referral following   This chapter shows example DDT tree and several possible scenarios of   Map-Requests coming to a Map Resolver and subsequent iterative DDT   referrals.  For the sake of example RLOCs of DDT nodes are shown inFuller, et al.            Expires July 22, 2017                [Page 27]Internet-Draft        LISP Delegated Database Tree          January 2017   IPv4 address space while the EIDs are in IPv6 AF.  The same principle   of hierarchical delegation and pinpointing referrals is equally   applicable to any AF whose address hierarchy can be expressed as a   bitstring with associated length.  DDT tree of IPv4 prefixes is   another AF with immediate practical value.   To show how referrals are followed to find the RLOCs for a number of   EIDs, consider the following example EID topology for DBID=0, IID=0,   AFI=2, and EID=0/0Fuller, et al.            Expires July 22, 2017                [Page 28]Internet-Draft        LISP Delegated Database Tree          January 2017      +---------------------+  +---------------------+      |  root1: 192.0.2.1   |  |  root2: 192.0.2.2   |      | authoritative: ::/0 |  | authoritative: ::/0 |      +---------------------+  +---------------------+                 |         \   /        |                 |          \ /         |                 |           X          |                 |          / \         |                 |         /   \        |                 |        |     |       |                 V        V     V       V  +-------------------------+  +--------------------------+  |  DDT node1: 192.0.2.11  |  |  DDT node2: 192.0.2.12   |  |     authoritative:      |  |      authoritative:      |  |      2001:db8::/32      |  |       2001:db8::/32      |  +-------------------------+  +--------------------------+                 |         \   /        |                 |          \ /         |                 |           X          |                 |          / \         |                 |         /   \        |                 |        |     |       |                 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|           +---------------------------+   +---------------------------+   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 to 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.Fuller, et al.            Expires July 22, 2017                [Page 29]Internet-Draft        LISP Delegated Database Tree          January 2017   The DDT nodes for 2001:db8::/32 delegate 2001:db8:0100::/40 to a DDT   Map Server with RLOC 192.0.2.101   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::/649.1.  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 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 referral cache) Map-Referral for EID-prefix       2001:db8::/32, action code NODE-REFERRAL, RLOC set (192.0.2.11,       192.0.2.12)   3.  Send DDT Map-Request to 192.0.2.11 or 192.0.2.12   4.  Receive (and save in referral cache) Map-Referral for EID-prefix       2001:db8:0100::/40, action code MS-REFERRAL, RLOC set       (192.0.2.101)   5.  Send DDT Map-Request to 192.0.2.101; if the ITR-originated       Encapsulated Map-Request had a LISP-SEC signature, it is includedFuller, et al.            Expires July 22, 2017                [Page 30]Internet-Draft        LISP Delegated Database Tree          January 2017   6.  DDT Map Server at 192.0.2.101 decapsulates the DDT Map-Request       and forwards to a registered site1 ETR for 2001:db8:0103::/48   7.  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.  DDT Map Resolver receives Map-Referral message and dequeues the       pending request for 2001:db8:0103:1::1   9.  site1 ETR for 2001:db8:0103::/48 receives Map-Request forwarded       by DDT Map Server and sends Map-Reply to ITR19.2.  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, 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 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 referral cache) Map-Referral for EID-prefix        2001:db8::/32, action code NODE-REFERRAL, RLOC set (192.0.2.11,        192.0.2.12)   3.   Send DDT Map-Request to 192.0.2.11 or 192.0.2.12   4.   Receive (and save in referral cache) Map-Referral for EID-prefix        2001:db8:0500::/40, action code NODE-REFERRAL, RLOC set        (192.0.2.201)   5.   Send DDT Map-Request to 192.0.2.201   6.   Receive (and save in referral cache) Map-Referral for EID-prefix        2001:db8:0501::/48, action code MS-REFERRAL, RLOC set        (192.0.2.221)   7.   Send DDT Map-Request to 192.0.2.221; if the ITR-originated        Encapsulated Map-Request had a LISP-SEC signature, it is        included   8.   DDT Map Server at 192.0.2.221 decapsulates the DDT Map-Request        and forwards to a registered site5 ETR for 2001:db8:0501:8::/64Fuller, et al.            Expires July 22, 2017                [Page 31]Internet-Draft        LISP Delegated Database Tree          January 2017   9.   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.  DDT Map Resolver receives Map-Referral(MS-ACK) message and        dequeues the pending request for 2001:db8:0501:8:4::1   11.  site5 ETR for 2001:db8:0501:8::/64 receives Map-Request        forwarded by DDT Map Server and sends Map-Reply to ITR29.3.  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 example   Section 9.1.  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 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.  DDT Map Server at 192.0.2.101 decapsulates the DDT Map-Request       and forwards to a registered site2 ETR for 2001:db8:0104::/48   3.  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.  DDT Map Resolver receives Map-Referral(MS-ACK) and dequeues the       pending request for 2001:db8:0104:2::2   5.  site2 ETR for 2001:db8:0104::/48 receives Map-Request and sends       Map-Reply to ITR19.4.  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 asks the same Map Resolver used in example   Section 9.2.  It sends an Encapsulated Map-Request for   2001:db8:0500:2:4::1 to that (DDT) Map Resolver, which finds a NODE-Fuller, et al.            Expires July 22, 2017                [Page 32]Internet-Draft        LISP Delegated Database Tree          January 2017   REFERRAL cache entry for 2001:db8:0500::/40 with RLOC set   (192.0.2.201).  It proceeds as follows:   1.  Send DDT Map-Request (for 2001:db8:0500:2:4::1) to 192.0.2.201   2.  Receive (and save in referral cache) Map-Referral for EID-prefix       2001:db8:0500::/48, action code MS-REFERRAL, RLOC set       (192.0.2.211)   3.  Send DDT Map-Request to 192.0.2.211; if the ITR-originated       Encapsulated Map-Request had a LISP-SEC signature, it is included   4.  DDT Map Server at 192.0.2.211 decapsulates the DDT Map-Request       and forwards to a registered site4 ETR for 2001:db8:0500:2::/64   5.  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.  DDT Map Resolver receives Map-Referral(MS-ACK) and dequeues the       pending request for 2001:db8:0500:2:4::1   7.  site4 ETR for 2001:db8:0500:2::/64 receives Map-Request and sends       Map-Reply to ITR29.5.  Lookup of 2001:db8:0500::1/128 (non-existent 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 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   2.  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 configured delegations       (2001:db8:0500:1::/64 and 2001:db8:0500:2::/64).   3.  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.Fuller, et al.            Expires July 22, 2017                [Page 33]Internet-Draft        LISP Delegated Database Tree          January 201710.  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 the   scope of this document.   Each DDT node is configured with one or more public/private key   pair(s) that are used to digitally sign referral records for XEID-   prefix(es) that the DDT node is authoritative for.  In other words,   each public/private key pair is associated with the combination of a   DDT node and a XEID-prefix that it is authoritative for.  Every DDT   node is also configured with the public keys of its children DDT   nodes.  By including 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 children DDT nodes.  A DDT node   configured to provide hints must also have the public keys of the DDT   nodes that its hints point to.  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.  Revocation mechanism is   described in Section 10.2.1.   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 either by having it configured as a trust anchor,   or by 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 public keys should 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.10.1.  XEID-prefix Delegation   In order to delegate XEID sub-prefixes to its children, 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 node is delegating the specified   XEID-prefix to a given child DDT node.  The signature is also   authenticating the public keys associated with the children nodes,   and authorizing them to be used by the children DDT nodes to provide   origin authentication and integrity protection for furtherFuller, et al.            Expires July 22, 2017                [Page 34]Internet-Draft        LISP Delegated Database Tree          January 2017   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.10.2.  DDT node operation   Upon receiving a Map-Request, the DDT node responds with a Map-   Referral as specified in Section 7.  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 children DDT   nodes.  Each record contained in the Map-Referral is signed using the   DDT node's private key.10.2.1.  DDT public key revocation   The node that owns a public key can also revoke that public key.  For   instance if a parent 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 is configured to   advertise this key, the parent 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.   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.  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 theFuller, et al.            Expires July 22, 2017                [Page 35]Internet-Draft        LISP Delegated Database Tree          January 2017   advertisement of the key was stopped by removal from the parent DDT   node.10.3.  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 they do not need to include keys in the Map-Referrals they   generate.10.4.  Map Resolver operation   Upon receiving a Map-Referral, the Map Resolver MUST first verify the   signature(s) by using 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 of the signature can be   used to select the right 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 verifying 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 no   matching key is found, or if none of the matching keys is   authoritative for the XEID-prefix in the Map-Referral record, or if   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 Resolver MAY try other siblings of this   node if there is an alternative node 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 resolver cannot verify the   signature after several trials.   Once the signature is verified, the Map Resolver has verified the   XEID-prefix delegation in the Map-Referral, and authenticated the   public keys of the children DDT nodes.  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.Fuller, et al.            Expires July 22, 2017                [Page 36]Internet-Draft        LISP Delegated Database Tree          January 201711.  Open Issues and Considerations   There are a number of issues with the organization of the mapping   database that need further investigation.  Among these are:   o  Defining an interface to implement interconnection and/or      interoperability with other mapping databases, such as LISP+ALT.   o  Additional key structures for use with LISP-DDT, such as to      support additional EID formats as defined in [I-D.ietf-lisp-lcaf]   o  Management of the DDT Map Resolver referral cache, in particular,      detecting and removing outdated entries.   o  Best practices for configuring hint referrals (or vice verse      avoiding using them).   Operational experience will help answer open questions surrounding   these and other issues.12.  IANA Considerations   This document makes no request of the IANA.13.  Security Considerations   Section 10 describes a DDT security architecture that provides data   origin authentication, data integrity protection, and XEID-prefix   delegation within the DDT Infrastructure.   Global XEID-prefix authorization is beyond the scope of this   document, but the SIDR working group [RFC6480] is developing an   infrastructure to support improved security of Internet routing.   Further work is required to determine if SIDR's public key   infrastructure (PKI) and the distributed repository system it uses   for storing and disseminating PKI data objects may also be used by   DDT devices to verifiably assert that they are the legitimate holders   of a set of XEID prefixes.   This document specifies how DDT security and LISP-SEC   ([I-D.ietf-lisp-sec]) complement one another to secure the DDT   infrastructure, Map-Referral messages, and the Map-Request/Map-Reply   protocols.  In the future other LISP security mechanisms may be   developed to replace LISP-SEC.  Such future security mechanisms   should describe how they can be used together with DDT to provide   similar levels of protection.Fuller, et al.            Expires July 22, 2017                [Page 37]Internet-Draft        LISP Delegated Database Tree          January 2017   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   and the path between Map-Resolver and Map-Server needs to be   protected, DDT security as described in Section 10 should be enabled   as well.14.  References14.1.  Normative References   [I-D.ietf-lisp-lcaf]              Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical              Address Format (LCAF)", draft-ietf-lisp-lcaf-22 (work in              progress), November 2016.   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels", BCP 14, RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <http://www.rfc-editor.org/info/rfc2119>.   [RFC3447]  Jonsson, J. and B. Kaliski, "Public-Key Cryptography              Standards (PKCS) #1: RSA Cryptography Specifications              Version 2.1", RFC 3447, DOI 10.17487/RFC3447, February              2003, <http://www.rfc-editor.org/info/rfc3447>.   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The              Locator/ID Separation Protocol (LISP)", RFC 6830,              DOI 10.17487/RFC6830, January 2013,              <http://www.rfc-editor.org/info/rfc6830>.   [RFC6833]  Fuller, V. and D. Farinacci, "Locator/ID Separation              Protocol (LISP) Map-Server Interface", RFC 6833,              DOI 10.17487/RFC6833, January 2013,              <http://www.rfc-editor.org/info/rfc6833>.14.2.  Informative References   [AFI]      "Address Family Identifier (AFIs)", IANA , Febuary 2007,              <http://www.iana.org/assignments/address-family-numbers/              address-family-numbers.xhtml>.   [I-D.ietf-lisp-sec]              Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D.              Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-12              (work in progress), November 2016.Fuller, et al.            Expires July 22, 2017                [Page 38]Internet-Draft        LISP Delegated Database Tree          January 2017   [LISP-TREE]              Jakab, L., Cabellos-Aparicio, A., Coras, F., Saucez, D.,              and O. Bonaventure, "LISP-TREE: a DNS hierarchy to support              the lisp mapping system", Selected Areas in              Communications, IEEE Journal , 2010,              <http://ieeexplore.ieee.org/xpls/              abs_all.jsp?arnumber=5586446>.   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,              and E. Lear, "Address Allocation for Private Internets",              BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,              <http://www.rfc-editor.org/info/rfc1918>.   [RFC5011]  StJohns, M., "Automated Updates of DNS Security (DNSSEC)              Trust Anchors", STD 74, RFC 5011, DOI 10.17487/RFC5011,              September 2007, <http://www.rfc-editor.org/info/rfc5011>.   [RFC6480]  Lepinski, M. and S. Kent, "An Infrastructure to Support              Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,              February 2012, <http://www.rfc-editor.org/info/rfc6480>.   [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, <http://www.rfc-editor.org/info/rfc6836>.   [RFC6837]  Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to              Routing Locator (RLOC) Database", RFC 6837,              DOI 10.17487/RFC6837, January 2013,              <http://www.rfc-editor.org/info/rfc6837>.Appendix A.  Acknowledgments   The authors would like to express their thanks to Lorand Jakab,   Albert Cabellos-Asparicio, Florin Coras, Damien Saucez, and Olivier   Bonaventure for their work on LISP-TREE [LISP-TREE] and LISP iterable   mappings that inspired the hierarchical database structure and lookup   iteration approach described in this document.  Thanks also go to   Dino Farinacci and Isidor Kouvelas for their implementation work; to   Selina Heimlich and Srin Subramanian for testing; to Fabio Maino for   work on security processing; and to Job Snijders, Glen Wiley, Neel   Goyal, and Mike Gibbs for work on operational considerations and   initial deployment of a prototype database infrastructure.  Special   thanks go to Jesper Skriver, Andrew Partan, and Noel Chiappa; all of   whom have participated in (and put up with) seemingly endless hours   of discussion of mapping database ideas, concepts, and issues.Fuller, et al.            Expires July 22, 2017                [Page 39]Internet-Draft        LISP Delegated Database Tree          January 2017Authors' Addresses   Vince Fuller   Email: vaf@vaf.net   Darrel Lewis   Cisco Systems   Email: darlewis@cisco.com   Vina Ermagan   Cisco Systems   Email: vermagan@cisco.com   Amit Jain   Juniper Networks   Email: atjain@juniper.net   Anton Smirnov   Cisco Systems   Email: as@cisco.comFuller, et al.            Expires July 22, 2017                [Page 40]