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Network Working Group                                        J. Peterson
Internet-Draft                                             Neustar, Inc.
Intended status: Standards Track                            July 3, 2017
Expires: January 4, 2018

An Architecture and Information Model for Telephone-Related Information


   As telephone services migrate to the Internet, Internet applications
   require tools to access and manage information about telephone
   numbers.  This document specifies a protocol-independent framework
   and information model for managing service and administration data
   related to telephone numbers.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on January 4, 2018.

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   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview of Operations  . . . . . . . . . . . . . . . . . . .   5
     3.1.  Relationship to the MODERN Framework  . . . . . . . . . .   7
   4.  The Information Model . . . . . . . . . . . . . . . . . . . .   8
     4.1.  Record Elements . . . . . . . . . . . . . . . . . . . . .   9
       4.1.1.  Identifier  . . . . . . . . . . . . . . . . . . . . .   9
       4.1.2.  Authority . . . . . . . . . . . . . . . . . . . . . .   9
       4.1.3.  Access  . . . . . . . . . . . . . . . . . . . . . . .   9
       4.1.4.  Subject . . . . . . . . . . . . . . . . . . . . . . .   9
       4.1.5.  Signature . . . . . . . . . . . . . . . . . . . . . .   9
       4.1.6.  Administrative Elements . . . . . . . . . . . . . . .  10  Contact . . . . . . . . . . . . . . . . . . . . .  10
       4.1.7.  Service Elements  . . . . . . . . . . . . . . . . . .  10  Service . . . . . . . . . . . . . . . . . . . . .  10
   Priority  . . . . . . . . . . . . . . . . . .  10
   Expiration  . . . . . . . . . . . . . . . . .  10
     4.2.  Element Value Types . . . . . . . . . . . . . . . . . . .  11
       4.2.1.  Service Types . . . . . . . . . . . . . . . . . . . .  11  Telephone Number Type . . . . . . . . . . . . . .  11
   TN Range Type . . . . . . . . . . . . . . . .  11  Domain Name Type  . . . . . . . . . . . . . . . .  11  Uniform Resource Indicator (URI) Type . . . . . .  11  Internet Protocol (IP) Address Type . . . . . . .  12  Trunk Group Type  . . . . . . . . . . . . . . . .  12  Service Provider Identifier (SPID) Type . . . . .  12
       4.2.2.  Public Key Type . . . . . . . . . . . . . . . . . . .  12
       4.2.3.  Contact Type  . . . . . . . . . . . . . . . . . . . .  12
       4.2.4.  Access Type . . . . . . . . . . . . . . . . . . . . .  12
       4.2.5.  Expiry Type . . . . . . . . . . . . . . . . . . . . .  13
       4.2.6.  Priority Type . . . . . . . . . . . . . . . . . . . .  13

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       4.2.7.  Record Identifier Type  . . . . . . . . . . . . . . .  13
       4.2.8.  Signature . . . . . . . . . . . . . . . . . . . . . .  13
       4.2.9.  Extension Type  . . . . . . . . . . . . . . . . . . .  13
   5.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     5.1.  Elements Common to All Operations . . . . . . . . . . . .  13
       5.1.1.  Requests  . . . . . . . . . . . . . . . . . . . . . .  14  Source  . . . . . . . . . . . . . . . . . . . . .  14
   Request Source  . . . . . . . . . . . . . . .  14
   Request Intermediary  . . . . . . . . . . . .  14  Subject . . . . . . . . . . . . . . . . . . . . .  15
   Request Restrictions  . . . . . . . . . . . .  15
       5.1.2.  Responses . . . . . . . . . . . . . . . . . . . . . .  15  Response Code . . . . . . . . . . . . . . . . . .  15
     5.2.  The Acquisition Operation . . . . . . . . . . . . . . . .  16
     5.3.  The Management Operation  . . . . . . . . . . . . . . . .  16
       5.3.1.  Service-to-Service Record Distribution  . . . . . . .  17
     5.4.  The Retrieval Operation . . . . . . . . . . . . . . . . .  17
     5.5.  Common Restrictions . . . . . . . . . . . . . . . . . . .  17
       5.5.1.  Route Source  . . . . . . . . . . . . . . . . . . . .  18
   6.  Implementing Operations . . . . . . . . . . . . . . . . . . .  18
     6.1.  Transport Independence  . . . . . . . . . . . . . . . . .  19
     6.2.  Bindings  . . . . . . . . . . . . . . . . . . . . . . . .  19
     6.3.  Encodings . . . . . . . . . . . . . . . . . . . . . . . .  20
     6.4.  Profiles and Extension Elements . . . . . . . . . . . . .  21
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  22
   10. Informative References  . . . . . . . . . . . . . . . . . . .  22
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  25

1.  Terminology

   In this document, the key words "MAY", "MUST, "MUST NOT", "SHOULD",
   and "SHOULD NOT", are to be interpreted as described in [RFC2119].
   This document also incorporates the terminology of the MODERN
   Framework [I-D.ietf-modern-problem-framework].

2.  Motivation

   Telephone numbers remain the worldwide standard identifier for
   routing calls and text messages over the Public Switched Telephone
   Network (PSTN).  Increasingly, real-time communications is migrating
   to the Internet, and bringing telephone numbers with it.  As
   identifiers, however, telephone numbers differ fundamentally from
   those commonly used by Internet applications.  Email, the web and
   native Voice over IP (VoIP) systems such as SIP ([RFC3261]) use
   identifiers that rely on the Domain Name System (DNS) to resolve a
   domain portion of the identifier to a particular IP address;

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   commonly, Uniform Resource Indicators (URIs) with a user and host
   component serve this purpose.  To help telephone numbers work
   similarly on the Internet, a number of efforts have specified
   mechanisms to manage and retrieve information about telephone numbers
   via network services.  SIP, for example, quickly developed a
   convention for using a TEL URI in the user part of its URIs.

   The ENUM ([RFC6116]) effort originally specified a public DNS profile
   for translating telephone numbers into URIs.  Due to the difficulty
   of coordinating the public administration of telephone numbers in the
   DNS, this work transitioned to "infrastructure" ENUM ([RFC5067]),
   which assumed private DNS implementations, each of which could give a
   different answer to the same request to translate a telephone number
   depending on who asked, or other internal factors.  The framework of
   the SPEERMINT working group ([RFC6406]), expanding on these
   requirements, differentiated the mapping of a telephone number to a
   target network (the "Look-up Function") from the mapping made by the
   originating network to the proper next-hop to reach such a target
   network (the "Location Routing Function").  To provision the data
   associated with telephone numbers, the DRINKS working group
   ([RFC6461]) designed systems for uploading back-end data to the
   services that would answer ENUM queries.

   None of the preceding efforts, however, encompassed the entire
   lifecycle of a telephone number as an Internet identifier.  They
   focused largely on service data, on how to "resolve" a telephone
   number to a location on the Internet, rather than on administrative
   questions of how numbers are acquired, how the entities associated
   with telephone numbers are authorized to provision data, and what
   kinds of systems need to be in place to allow a diverse community of
   devices, applications and users to rely on telephone numbers.  Early
   considerations were moreover based on overlapping, but not entirely
   consistent, information models: intrinsic limitations in the DNS kept
   the queries and responses of ENUM relatively simple, whereas the
   DRINKS provisioning system considered a much richer syntax.

   The need for solutions in this space is pressing, as many carriers
   worldwide contemplate migrating their entire PSTN infrastructure onto
   the Internet within the next decade.  Further pressures come from
   emerging Internet communications providers who never invested in PSTN
   infrastructure in the first place, but want access to services
   related to telephone numbers.  This includes devices, services, and
   applications on the Internet that make use of telephone numbers and
   need to distribute and manage numbering inventory: for example, an
   Internet-enabled PBX that might want to automate the process for
   allowing new connected phones to acquire numbers and provision
   contact information for their users.  Ultimately, the resources
   identified by telephone numbers must also be reachable on the

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   Internet, and different applications might want to use different
   protocols to retrieve information about numbers.  In some
   environments, there are performance constraints that would require a
   very lightweight binary protocol; in others, applications might
   prefer human-readable markup languages suitable for interfacing with
   existing APIs.  The use cases associated with these functions are
   detailed in [I-D.ietf-modern-problem-framework].

   Therefore, this document proposes a reconsideration of telephone
   service and administration data on the Internet, based on an
   information model that allows records associated with telephone
   number to be created, modified and accessed through network
   interfaces.  This document specifies no particular syntax or encoding
   for queries or responses, but instead describes an extensible
   information model for the semantics of provisioning and querying
   operations associated with a telephone number.

3.  Overview of Operations

   In TeRI, Clients use Operations to acquire, manage, or retrieve
   Records, which are typically stored at Services.  Every Operation
   consists of a Request and a Response.  Requests may pass directly
   from a Client to a Service, or they may pass through one or more
   Request Intermediaries; Request Intermediaries can modify Requests
   and Responses in transit.  A Response will contain a Response Code
   indicating the status of the requested Operation.  Both Requests and
   Responses can, in certain Operations, carry Records.  TeRI does not
   specify any specific data format or underlying protocol to
   instantiate Requests, Responses, or Records: TeRI is an abstract
   architecture that must be implemented with concrete bindings and
   encodings (see Section 6).

   The TeRI information model (see Section 4) specifies the baseline
   contents of Records, though Records are designed to be extended by
   future specifications for particular use cases or environments.
   Records provide information related to telephone numbers; a Record
   may apply to one telephone number, a block of numbers, or several
   discrete blocks of numbers.  There may be multiple Records stored at
   a Service which cover a single telephone number: this may include
   multiple Records that apply only to that one telephone number, which
   probably have been provisioned by different Authorities, as well as
   Records applying to a telephone number range which contains that one
   telephone number.  Authorities sign Records, and Clients typically
   have a trust relationship with those Authorities.

   The three TeRI Operations are as follows:

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      The Acquisition Operation enables a Client to request the
      allocation of unallocated telephone numbers that are held by a
      Service on behalf of an Authority.  A Service makes an
      authorization decision before allocating the telephone number(s)
      in accordance with the policy of the Authority.  One or more new
      Records may be created as a result of a successful Acquisition
      Operation, and the Service will pass any such Record(s) to the
      acquiring Client as well as retaining them locally at the Service.
      As a result of a successful Acquisition Operation, the
      administrative entity operating the Client will typically become a
      new Authority for the allocated telephone numbers.

      The Management Operation enables a Client to push new values for a
      Record to a Service.  In the baseline Operation described in this
      document, the Client pushes the entire value of the Record to the
      Service.  The Service then makes an authorization decision to
      determine whether or not the Client is permitted to upload the
      Record in question.  The policy behind those authorization
      decisions is outside the scope of this document, though at a high-
      level, the Client must be an Authority for a telephone number in
      order to publish and modify Records associated with that number.
      However, outside of hierarchical Authorities, Clients will not be
      able to modify or delete Records related to that number that have
      been provisioned by other Authorities.

      The Retrieval Operation enables a Client to request one or more
      Records that are stored at a Service.  Some Records may contain
      public information, and some may contain information that requires
      an authorization decision to be made before it is shared with a
      Client.  Note that Services may have trust relationships with
      Request Intermediaries, and that the Response may depend on that
      trust relationship rather than on the Service's trust relationship
      with the Client.  Although a Client acquires Records from a
      Service, a Client need not have a trust relationship with it -
      typically, the Client trusts the Record because it trusts the
      Authority which signed the Record rather than the Service that
      holds or delivers the Record.

   All entities that act as TeRI Services will offer at least the
   Management and Retrieval interfaces, and some will also offer the
   Acquisition interface.  All entities that act as TeRI Clients will
   implement at least the Retrieval Operation; others may implement the
   client side of one or both of the Management and Acquisition

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3.1.  Relationship to the MODERN Framework

   The MODERN Framework [I-D.ietf-modern-problem-framework] enumerates a
   series of actors and use cases related to telephone number
   administration on the Internet.  In terms of actors, it details
   interactions between Users, Communications Service Providers (CSPs),
   Registries, Registrars, and Government Entities.  These actors
   implement the interfaces and Operations of TeRI Clients or Services
   in support of various use cases.  Typically, Users, CSPs, and
   Government Entities act as TeRI Clients, and CSPs, Registries, and
   Registrars act as TeRI Services.

   In the MODERN framework, the lifecycle of a number begins with a
   Registry.  Registrars acquire telephone numbers from Registries, and
   make those numbers available for allocation.  Thus, an Acquisition
   Operation is used by a Registrar that acquires numbers from a
   Registry, and this Request, if successful, will result in the
   creation of a Record that is returned in the Response.  That Record
   renders the Registrar an Authority for the telephone numbers in
   question, but that Record will contain exclusively Administrative
   Data, with no Service Data.

   In some cases, that Registrar will also fulfil the role of a CSP, and
   as a CSP, it will allocate those numbers to Users and generate any
   associated Records itself.  Alternatively, a Registrar that does not
   act as a CSP may in turn act as a TeRI Service to which CSPs, and
   potentially Users, will send Acquisition Requests to acquire number
   blocks or individual numbers.  Through that process, CSPs and Users
   can also become Authorities for telephone numbers.  New Records
   containing Administrative Data indicating the contact information and
   so forth of the CSP or the User will be generated when that
   allocation occurs; those Records will be stored at the Registrar.
   The Registrar may also house a "glue" Record of Service Data that
   indicates the servicing CSP for the telephone number, and in
   particular the Retrieval interface of that CSP where Records with
   further Service Data can be found.

   The Authorities who create and propagate Records of Service Data are
   typically CSPs and Users.  Most commonly, CSPs will store these
   Service Data Records, and make them accessible through a Retrieval
   interface.  CSPs may also propagate these Records to various external
   directories; the signature of the CSP and expiry data in the Record
   will prove its integrity and freshness to any relying party.  It is
   envisioned that multiple Authorities may create Records for different
   services that are associated with a given telephone number.

   Finally, CSPs and Users may query a Retrieval interface at a CSP to
   acquire Records containing Service Data that will enable them to

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   route communications.  The Retrieval interface will enable Clients to
   ask for Records associated with particular services, though Retrieval
   can present Clients with a number of service options.  Entities may
   also query the Retrieval Interface of Registrars to acquire
   Administrative Data about a telephone number, though it is likely
   that authorization policies will restrict access to that data.
   Government Entities may have legal relationships with Registrars that
   grant them authorization privileges with regard to Administrative

4.  The Information Model

   The fundamental building block of the TeRI model is the Record.  A
   Record is created by an Authority who has authority over a particular
   telephone number or a set of numbers.  There may be more than one
   Authority who is authorized to create Records for a particular
   telephone number, and a TeRI service may have multiple Records
   corresponding to a single telephone number, including potentially
   overlapping Records associated with a range of numbers that
   encompasses a particular telephone number.  Under various
   circumstances detailed in Section 5, participants in the numbering
   ecosystem may create, read, update, and modify Records.

   Records contain Elements that hold data about the telephone number.
   Elements in this information model have a Name, which may optionally
   be associated with a Type and Value.  Records are divided into two
   broad categories: Administrative Records and Service Records.
   Administrative Records hold data about how records have been
   allocated that is typically generated by a Registrar or similar
   entity that distributes numbers; they include information on the
   administrative contacts for telephone numbers, and so on.  Service
   Records hold data required to initiate communication with the
   resources reachable at a telephone number; these Records are
   typically generated by an assignee or delegate such as a CSP.

   The distinction between Administrative and Service Records exists so
   that Clients performing Retrieval Queries can ask for one instead of
   the other.  Some Clients may be authorized to receive Service Records
   for a particular telephone number but not Administrative Records, or
   vice versa.  In practice, a Record may contain both Administrative
   and Service Elements, but the creators of Records may find it useful
   to keep the two types of information separate.  If a Record contains
   both Administrative and Service Elements, it may be returned in a
   Retrieval Query for either, provided the Client is authorized to
   receive the Elements within.

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4.1.  Record Elements

   A Record is made up of Elements, which may contain Service or
   Administrative Data.  All Records can contain the following generic

4.1.1.  Identifier

   Every Record has an Identifier, which is a globally unique identifier
   of the Record.  The Identifier will typically be created at the same
   time as the Record itself, at a time when an assignment or delegation
   has occurred (as described in [I-D.ietf-modern-problem-framework]).

4.1.2.  Authority

   Every Record contains an Authority Element indicating the source of
   the data: either the entity that provisioned the data with the
   Service, or the external source from which the Service collected the
   data.  The Authority element ideally gives a logical identity of the
   source of the data.  A public key value may also be associated with
   an Authority element.

4.1.3.  Access

   Every Record contains an Access Element indicating the conditions
   under which Retrieval Requests can acquire the Record.  The Access
   Element is set by the Authority generating the Record.

4.1.4.  Subject

   Every Record has a Subject.  As TeRI Records concern telephone
   numbers, the Subject of a Record is an array of either a telephone
   number type or a telephone number range type.  The simplest Record
   Subject is an array with one element consisting of a single telephone

4.1.5.  Signature

   Optionally, a Record contains a Signature element.  The Signature
   element contains a signature over the concatenation of the other
   elements given the Record.  Signatures are provided by the Authority
   responsible for the Record.

   [Syntax TBD]

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4.1.6.  Administrative Elements

   Records that contain Administrative Elements are Administrative
   Records.  The baseline TeRI specification sets only one
   Administrative Element, the Contact.  Contact

   Every Administrative Record has at least one Contact.  The Contact
   contains administrative data about the assignee of the telephone
   number, though additionally Contacts may contain information about
   delegates (as defined in [I-D.ietf-modern-problem-framework]).
   Typically, this information would be set by the Registrar; policies
   outside the scope of this specification dictate the sorts of entities
   that may be designated as Contacts in Records.

4.1.7.  Service Elements

   Records that contain a Service Element are Service Records.  The most
   important Service Element is simply called Service, and it contains
   an identifier for a communications resource reachable through a
   telephone number.  More than one Service Element can appear in a
   given Record.  Other Service Elements may be defined by later
   specifications.  Service

   Records optionally have one or more Service entries.  A Service may
   be of any Service Type, as given in Section 4.2.1.  Optionally,
   subelements modify how a Service Element should be retained.  Priority

   Optionally, a Service may specify a weighted Priority associated with
   a Record.  Priorities are between 0 and 1, with a value of 1 having
   the highest priority.  Expiration

   Optionally, a Service may specify an absolute time at which a Record
   will no longer be valid, should a client or intermediary wish to
   cache a Record.  In the absence of an Expiration element, Records may
   be cached for a maximum of twenty-four hours.

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4.2.  Element Value Types

   The remainder of a Record is made up of Elements.  Elements types are
   specified in this section.  Every Element Type has a Type Code.  A
   Type Code is used as a short form for the Element in a Record.

4.2.1.  Service Types  Telephone Number Type

   The telephone number type conforms to the telephone number syntax
   given in [RFC3966] Section 3, in the ABNF for "telephone-subscriber."

   Type Code: T

   [TBD - need for subtying?  E.164, Service Code, Short Code, Prefix,
   Nationally-Specific and Unknown. ]  TN Range Type

   The TN range type consists of a prefix of a telephone number (per
   [RFC3966] "telephone-subscriber"), and is semantically equivalent to
   all syntactically-valid telephone numbers below that prefix.  For
   example, in the North American Numbering plan, the prefix 157143454
   would be equivalent to all numbers ranging from 15714345400 to

   [TBD - identify alternative ways of specifying ranges, potentially as
   separate element types]

   Type Code: R  Domain Name Type

   The domain name type conforms to the syntax of RFC1034 Section 3.5
   and Section 2.1 of [RFC1123].

   Type Code: D  Uniform Resource Indicator (URI) Type

   The Uniform Resource Indicator (URI) type conforms to the syntax for
   URIs given in [RFC3986] (see Section 3).

   Type Code: U

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   The IP Address type conforms to the ABNF syntax of either the
   IPv4address given in RFC3986 (Appendix A) or the IPv6reference of

   Type Code: I  Trunk Group Type

   The trunk group type conforms to the "trunk-group-label" ABNF given
   in [RFC4904] (Section 5).

   Type Code: G  Service Provider Identifier (SPID) Type

   The SPID type consists of a four-digit number.

   [TBD - introduce other elements for alternative SPID syntaxes]

   Type Code: ?

4.2.2.  Public Key Type

   The Credential type consists of a public key [encoding TBD].

   Type Code: C

4.2.3.  Contact Type

   The contact type follows the conventions of jCard [RFC7095].

   Type Code: C

4.2.4.  Access Type

   The access type consists of a string, which is set to the values
   "Public," "Semi-restricted" or "Restricted."  If either "Semi-
   restricted" or "Restricted" appears as the access type, the Element
   will need to be accompanied by a Permissions Element.  [TBD - work to
   be done here]

   Type Code: A

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4.2.5.  Expiry Type

   The Expiry type is an absolute time conformant to the syntax of

   Type Code: E

4.2.6.  Priority Type

   The Priority type contains a number between 0 and 1, conforming to
   the specification of the "q" parameter of the Contact header field in

   Type Code: P

4.2.7.  Record Identifier Type

   The Record Identifier Type consists of a unique identifier for a
   record [format TBD].

   Type Code: U

4.2.8.  Signature

   [Syntax TBD]

   Type Code: S

4.2.9.  Extension Type

   This code is reserved for future use.

   Type Code: X

5.  Operations

   In this section are detailed the three TeRI Operations: Acquisition,
   Management, and Retrieval Operations.

5.1.  Elements Common to All Operations

   All Operations in the TeRI model consist of Requests and Responses.
   A Request from a TeRI Client to a Service may attempt to create,
   read, update, or delete TeRI Records.  Requests may use Restrictions
   to focus only on particular parts of a TeRI Record.  A Response gives
   the result of the Operation back to the Client, which may indicate
   success of failure.

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5.1.1.  Requests

   All TeRI Requests have a Source, a Subject, and optionally a set of
   Restrictions which further specify the nature of the Request.  Some
   Requests will contain the Identifier of the Record they concern;
   others will query for all Records matching a given Subject.  Source

   The Source is a required element in all Requests.  In this
   specification, two categories of Sources are defined: Request Source
   and Request Intermediary.  At least one of these Sources must be
   present in a Retrieval Request, and multiple Sources are permitted.
   Responses do not contain a Source.

   Future specifications may extend the set of Source types.  Request Source

   Every Request generated by a Client has a Request Source, which
   identifies the originator of the Request.  This represents the
   logical identity of the user or service provider who first sent the
   Request, rather than the identity of any Intermediate entity.  This
   field is provided in the Source to authenticate the poser of the
   Request, so that the Service can make any necessary authorization
   decisions as it formulates a Response.

   In some service deployments, an Intermediary may wish to mask the
   Request's Source from a Service.  The removal of the Request's Source
   by an Intermediary is permitted by TeRI, but any Intermediary that
   removes the Request Source must provide a Request Intermediary for
   the Source element.

   A Request Source element has a Type, which indicates how the logical
   identity of the originator of the Request has been represented.  The
   Type field of the Request Source is extensible.  Initial values
   include a domain name, a URI and a telephone number.

   The Type element of the Request Source is followed by a Value, which
   contains the identity.  The format of the identity is determined by
   the Type.  Request Intermediary

   Optionally, Requests may contain one or more Request Intermediary
   elements in the Source.  A Request Intermediary resides between the
   originator of the Request (the Client) and the Service, where it may

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   aggregate queries, proxy them, transcode them, or provide any related
   relay function to assist the delivery of Requests to the Service.

   The Request Intermediary element, like the Request Source, contains
   the logical identity of the service that relayed the Request.  This
   field is provided in the Source for those deployments in which the
   Service makes an authorization decision based on the identity of the
   Intermediary rather than a Request Source.

   A Request Intermediary element has a Type, which indicates how the
   logical identity of the Intermediary has been represented.  The Type
   element of the Request Intermediary is extensible.  Initial values
   include a domain name, an X.509 certificate subject, or a URI.

   The Type of the Request Intermediary element is followed by a Value,
   which contains the identity.  The format of the identity is
   determined by the Type.  Subject

   All Requests have a Subject.  The Subject identifies the resource
   that the Request concerns.  Responses only contain a Subject if the
   Subject of the Response differs from that of the original Request,
   which may occur when (for example) the Subject contains a broad
   range, and the Service replies with a more narrow Subject.  Future
   specifications, including Profiles, may define alternative Subject
   elements.  Request Restrictions

   TeRI Request Restrictions consist of a Name with an optional Type and
   an Optional Value.  Most Restrictions are specific to the Operation.

5.1.2.  Responses

   All TeRI Responses will have a Responde Code, and may contain one or
   more Records.  Response Code

   All Responses contain a Response Code.

   Response Codes defined by this document include: Success, Subject
   Does Not Exist, Subject Conflict, No Suitable Records Exist for
   Subject, Subject Syntax Error, No Suitable Records Exist for
   Restriction, Unauthorized Source, Route Source Topology Unavailable.


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5.2.  The Acquisition Operation

   An Acquisition Request has a Source and a Subject, and may have one
   or more Restrictions.  An Acquisition Response has a Response Code,
   and will contain one Record if it is successful.

   The Subject of an Acquisition Request always specifies a Telephone
   Number Type or a Telephone Number Range Type.  If the Subject
   contains a particular telephone number, then the Acquisition Request
   is a Request to acquire that particular telephone number.  If it is a
   range, the Acquisition Request should be considered to be for the
   entire range, but future Restrictions defined for this the Request
   might limit the scope of the resources requested.  The Service will
   determine whether or not the Client is authorized to acquire the
   resources in question based on the Source of the Acquisition Request.

   The Response to an Acquisition Request will contain a Success
   Response Code if the resource can be allocated.  The Subject of a
   Success Response will always contain the Telephone Number Type or
   Telephone Number Range that has been allocated.  A successful
   Acquisition Response must contain a Record with a Identifier Element;
   that Record may also contain an Element containing tokens or other
   material that the Client might use to acquire credentials from a
   Credential Authority (see [I-D.ietf-modern-problem-framework]).  By
   default, this Record will contain only Administrative Elements,
   without Service Elements.  If a requested telephone number (or range)
   is already allocated, or a telephone number in the specified range is
   not available, then a Subject Conflict Response Code is returned.

5.3.  The Management Operation

   A Management Request comprises a Source, a Subject, and one or more
   Records; it also may contain one or more Restrictions.  A Management
   Response contains a Response Code, and optionally may contain a

   The Subject of a Management Request always specifies a Telephone
   Number Type or a Telephone Number Range Type.  In almost all
   circumstances, however, the Service will locate that Record(s) that a
   Management Request modifies through the Identifier Restriction on
   each Record in the Management Request.

   A Management Request contains at least one Record; it may contain
   multiple Records.  Each Record in the Management Request must contain
   a Record Identifier Element which designates the Record that the
   Client is requesting that the Service provision as or replace with
   the Record included in the Management Request.  The Service will

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   authorize whether or not the Client is authorized to modify the
   Record in question via the Source of the Management Request.

   The Management Operation not only provisions Records at a Service,
   but also provisions at the Service any information needed by the
   Service to make authorization and policy decisions when responding to
   Retrieval Requests.  This information is tied to the Access Element
   of the Record.

5.3.1.  Service-to-Service Record Distribution

   TeRI Records contain the signature of the Authority who generated
   them, and as such, a relying party trusts a Record based on that
   signature rather than based on the Service from which a Record was
   retrieved.  This permits architectures that allow a Records to be
   duplicated across a distributed Service.  Distribution protocols are
   left to future specifications.

5.4.  The Retrieval Operation

   Every Retrieval Request comprises a Source and a Subject, and may
   have one or more Restrictions.  A Retrieval Response has a Response
   Code, optionally one or more Records, and optionally a Subject, if
   the Subject differs from that of the Request.

   Retrieval Requests optionally contain Restrictions; a Request with no
   specified Restrictions requests that the Service return any Records
   associated with the Subject.  In a Request, the presence of one or
   more Restrictions limits the scope of the Request to Records about
   the Subject containing those Elements, or the Restrictions otherwise
   qualify the Request.  Typically a Restriction will specify a Service
   or Service Type that the Client seeks Records for.

   Successful Retrieval Responses always contain one or more Records;
   unsuccessful Responses never contain Records.

5.5.  Common Restrictions

   Restrictions are broadly structured around Elements, typically the
   Service, Contact, and Identifier Elements.  A TeRI Request may
   contain a Restriction based on any Element, be it a baseline Element
   or a Service or Administrative Element, including Elements that are
   defined in future specifications.  Semantically, a Restriction may
   target Records that contain a particular Element, or only Elements
   with a particular subtype or even value.  Multiple Restrictions may
   appear in a Request, and Restrictions are always additive, which is
   to say that Restriction always narrow then target of a Request.

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   Restrictions may either name a target Element, or both an Element and
   a value.  For example, a Management Request replacing an existing
   Record must name as its target with a Restriction both the Identifier
   Element and the value, which is the identifier for the Record.  A
   Retrieval Request for a particular Subject might restrict itself to
   Service elements, or even Service elements that have a particular
   subtype, such as a URI.

5.5.1.  Route Source

   Optionally, Retrieval Requests may contain a Route Source which
   functions in much the same way as a Restriction.  A Route Source
   identifies a reference point in the network from which any Service
   Elements in the response should be calculated.  It therefore always
   designates a network element, though depending on the circumstances,
   it may be an endpoint, a gateway, a border device, or any other agent
   that makes forwarding decisions for telephone calls and related
   services.  A Route Source is a subelement of the Source element.

   A Route Source element has a Type, which indicates how the network
   element has been represented.  The Type field of the Request Source
   is extensible.  Initial values include a domain name, an IP address
   or a trunk group.

   The Type of the Route Source element is followed by a Value, which
   designates the network element.  The format of the identity is
   determined by the Type.

6.  Implementing Operations

   This framework specifies an abstract Request/Response protocol that
   enables a Client to send Requests to a Service about telephone
   numbers or related telephone services.  Requests may pass through one
   or more Intermediaries on their way from a Client to a Service; for
   example, through aggregators or service bureaus.  A Client
   establishes the Subject of a Request, and optionally includes one or
   more Restrictions to focus the scope of the Request.  When a Service
   receives a Request, it performs any necessary authorization and
   policy decisions based on the Source.  If policy permits, the Service
   generates a Response, which will consist of a Response Code and one
   or more Records associated with the Subject.  The Service then sends
   the Response through the same path that the Request followed;
   transactional identifiers set by the Client and Service correlate the
   Request to the Response and assist any intermediary routing.

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6.1.  Transport Independence

   The information model provided for Requests and Responses in this
   framework is independent of any underlying transport or encoding.
   Future specifications will define Bindings that specify particular
   transports and Encodings for Requests and Responses.  In some
   deployment environments, for example, a binary encoding and
   lightweight transport might be more appropriate than the use of a web
   protocol.  This specification provides a template of requirements
   that must be addressed by any encoding scheme.

   It is a design goal of this work that the semantics of Requests and
   Responses survive interworking through translations from one encoding
   to another; for example, when an Intermediary receives a binary
   Request from a Client, it should be able to transcode it to an XML
   format to send to a Service without discarding any of the original

6.2.  Bindings

   A TeRI Binding is an underlying protocol that carries Requests and
   Responses.  Future specifications may define Bindings in accordance
   with the procedures in the IANA Considerations sections of this

   By underlying protocol, this specification means both transport-layer
   protocols as well as any application-layer protocols that the Binding
   requires.  Thus an example Binding might specify a combination of
   TCP, TLS, HTTP and SOAP as the underlying transport for TeRI.
   Alternatively, it might only specify a very lightweight underlying
   protocol like UDP.  A Binding may be specific to a particular
   Encoding, or it may be independent of any Encoding.

   Bindings must specify whether they are continuous, transactional or
   non-transactional.  A continuous Binding creates a persistent
   connection between two TeRI entities over which many, potentially
   unrelated, Requests and Responses might flow.  Many Bindings defined
   for use between an Intermediary and a Service will have this
   property, as Intermediaries may aggregate on behalf of many Clients,
   and opening a separate transport-layer connection for each new
   Request would be inefficient.  A transactional Binding creates a
   temporary connection between two TeRI entities for the purpose of
   fulfilling a single Request; any Responses to the Request will use
   the same connection to return to the sender of the Request.  Finally,
   a non-transactional Binding does not rely on any sort of connection
   semantics: the senders of Requests and Responses will always initiate
   a new instance of the Binding to send a message.

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   This document makes no provision for discovering the Bindings
   supported by a TeRI Client, Intermediary or Service.  Intermediaries
   may transcode between Bindings if necessary when acting to connect a
   Client and a Service, especially if the Client and Service support no
   Bindings in common.

   A Binding specification must enumerate all categories of metadata
   required to establish a connection using a Binding.  For some
   Bindings, this might comprise solely an IP address and a port; for
   other Bindings, this might instead require higher-layer application
   identifiers like a URI.  This metadata includes any identifiers
   necessary for correlating Requests to Responses in a continuous or
   non-transactional Binding; any Encoding making use of these Bindings
   must specify how it carries those elements.

   Bindings must also describe the security services they make
   available.  Bindings must have a means of providing mutual
   authentication, integrity and confidentiality between Clients,
   Intermediaries and Services.  If a Binding supports TLS, for example,
   these features can be provided by using TLS in an appropriate
   deployment environment.

6.3.  Encodings

   A TeRI Encoding specifies how the Request and Response are
   constructed syntactically.  An Encoding may be specific to a
   particular Binding, or it may be specified independently of any

   An Encoding may define an object format; for example, an XML or JSON
   object, described with any appropriate schemas, or an ABNF
   description.  An Encoding might alternatively specify a mapping of
   the semantic elements of Requests and Responses on to the existing
   fields of headers of a protocol, especially when that protocol has
   been defined as an underlying protocol Binding.  Encodings must also
   define whether or not they provide a bundling feature that allows
   multiple Requests to be carried within particular objects or

   Every Encoding must specify how each semantic Element Type of a
   Request and Response will be represented.  For all baseline TeRI
   Restrictions and Element Types, the Encoding specifies whether values
   will be text or binary, how they will be encoded.  Many baseline
   Element Types (such as telephone numbers) can appear in different
   places in a TeRI message; Encodings need only specify these common
   element types once.  Due to the extensibility of TeRI, however,
   future specifications might define Element Types that an Encoding

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   does not address.  Profiles using those extensions and Encodings must
   explain their interaction.

   Encodings must also describe the security services they make
   available.  In particular, encodings must describe a means of
   providing authentication of the Sources and Authorities of Requests
   and Responses respectively, as well as an integrity check over
   critical elements including the Subject of Requests and the Record of

   [TBD - we may define more about the computation of this signature,
   including canonicalization of elements, in this framework, and make
   it a requirement for encodings to support this mechanism]

6.4.  Profiles and Extension Elements

   For particular deployment environments, only one Binding, Encoding
   and set of Restrictions or other extended elements may be meaningful.
   Future specifications may therefore define TeRI Profiles, which
   describe a particular deployment environment and the Binding,
   Encoding and set of Elements and Restrictions it requires.

   Profiles may encompass extensions to baseline TeRI, and any new
   Elements or Restrictions necessary may be defined within the Profile.
   It is not necessary for a TeRI Service to understand extension
   Elements that appear in Records or as Restrictions in a Query: if a
   Service receives a Query with a Restriction, it can search Records
   with the target Subject for Elements matching the Restriction and
   return only those that apply.  As such there is no formal capability
   negotiation for extensions in the TeRI model: a Record may contain
   Elements beyond baseline TeRI that a particular Client does not
   understand and must ignore; similarly, a Service may receive a Query
   with a Restriction that applies to no Records collected at the
   Service, in which case the Service returns a "No Suitable Records
   Exist for Restriction" Response Code.

7.  Security Considerations

   The framework of this document differs from previous efforts to
   manage telephone numbers on the Internet largely by offering a much
   richer set of security services.  In particular, it requires that
   three entities be capable of authenticating themselves to one another
   at the layer of a binding: Clients, Intermediaries and Services.  It
   furthermore requires object security at the encoding layer so that
   Sources and Authorities can sign data in order to authenticate
   Requests and Responses that may pass through Intermediaries, and
   moreover so that Authorities can prove to Clients that their Records
   are authoritative even when the Authority does not operate the

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   Service.  The requirements that bindings and encodings must satisfy
   to meet these security needs are specified in Section 6.1.

   [TBD - more]

8.  IANA Considerations

   This specification defines several registries: A registry of
   Elements, a registry of Element Types, and a registry of Response

   This document creates a registry of Elements for use with this
   framework.  This registry is extensible, with an IANA Registration
   policy of Specification Required.  Any new Element registered must
   supply the name of the Element, the name of the parent Element in the
   information model, and a code point.  [TBD]

   This specification pre-provisions the Element Types registry with the
   entries given in Section 6.  These elements are indexed by their Type
   Code.  This registry is extensible, with an IANA Registration policy
   of Specification Required.  Any new Element Type registered must
   supply the name of the Element Type, the name of the parent element
   in the information model, and a Type Code.

   This document furthermore creates a registry of Response Codes.  This
   registry is pre-provisioned with the values given in Section 5.5.

9.  Acknowledgements

   The authors would like to thank Chris Wendt, Paul Kyzviat and Dale
   Worley for their input into this specification.

10.  Informative References

              Peterson, J. and T. McGarry, "Modern Problem Statement,
              Use Cases, and Framework", draft-ietf-modern-problem-
              framework-02 (work in progress), March 2017.

   [RFC1123]  Braden, R., Ed., "Requirements for Internet Hosts -
              Application and Support", STD 3, RFC 1123,
              DOI 10.17487/RFC1123, October 1989,

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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,

   [RFC3324]  Watson, M., "Short Term Requirements for Network Asserted
              Identity", RFC 3324, DOI 10.17487/RFC3324, November 2002,

   [RFC3325]  Jennings, C., Peterson, J., and M. Watson, "Private
              Extensions to the Session Initiation Protocol (SIP) for
              Asserted Identity within Trusted Networks", RFC 3325,
              DOI 10.17487/RFC3325, November 2002,

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,

   [RFC3966]  Schulzrinne, H., "The tel URI for Telephone Numbers",
              RFC 3966, DOI 10.17487/RFC3966, December 2004,

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,

   [RFC4474]  Peterson, J. and C. Jennings, "Enhancements for
              Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", RFC 4474,
              DOI 10.17487/RFC4474, August 2006,

   [RFC4904]  Gurbani, V. and C. Jennings, "Representing Trunk Groups in
              tel/sip Uniform Resource Identifiers (URIs)", RFC 4904,
              DOI 10.17487/RFC4904, June 2007,

   [RFC4916]  Elwell, J., "Connected Identity in the Session Initiation
              Protocol (SIP)", RFC 4916, DOI 10.17487/RFC4916, June
              2007, <http://www.rfc-editor.org/info/rfc4916>.

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   [RFC5039]  Rosenberg, J. and C. Jennings, "The Session Initiation
              Protocol (SIP) and Spam", RFC 5039, DOI 10.17487/RFC5039,
              January 2008, <http://www.rfc-editor.org/info/rfc5039>.

   [RFC5067]  Lind, S. and P. Pfautz, "Infrastructure ENUM
              Requirements", RFC 5067, DOI 10.17487/RFC5067, November
              2007, <http://www.rfc-editor.org/info/rfc5067>.

   [RFC5727]  Peterson, J., Jennings, C., and R. Sparks, "Change Process
              for the Session Initiation Protocol (SIP) and the Real-
              time Applications and Infrastructure Area", BCP 67,
              RFC 5727, DOI 10.17487/RFC5727, March 2010,

   [RFC5954]  Gurbani, V., Ed., Carpenter, B., Ed., and B. Tate, Ed.,
              "Essential Correction for IPv6 ABNF and URI Comparison in
              RFC 3261", RFC 5954, DOI 10.17487/RFC5954, August 2010,

   [RFC6116]  Bradner, S., Conroy, L., and K. Fujiwara, "The E.164 to
              Uniform Resource Identifiers (URI) Dynamic Delegation
              Discovery System (DDDS) Application (ENUM)", RFC 6116,
              DOI 10.17487/RFC6116, March 2011,

   [RFC6406]  Malas, D., Ed. and J. Livingood, Ed., "Session PEERing for
              Multimedia INTerconnect (SPEERMINT) Architecture",
              RFC 6406, DOI 10.17487/RFC6406, November 2011,

   [RFC6461]  Channabasappa, S., Ed., "Data for Reachability of Inter-
              /Intra-NetworK SIP (DRINKS) Use Cases and Protocol
              Requirements", RFC 6461, DOI 10.17487/RFC6461, January
              2012, <http://www.rfc-editor.org/info/rfc6461>.

   [RFC6698]  Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
              2012, <http://www.rfc-editor.org/info/rfc6698>.

   [RFC6950]  Peterson, J., Kolkman, O., Tschofenig, H., and B. Aboba,
              "Architectural Considerations on Application Features in
              the DNS", RFC 6950, DOI 10.17487/RFC6950, October 2013,

   [RFC7095]  Kewisch, P., "jCard: The JSON Format for vCard", RFC 7095,
              DOI 10.17487/RFC7095, January 2014,

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   [RFC7340]  Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure
              Telephone Identity Problem Statement and Requirements",
              RFC 7340, DOI 10.17487/RFC7340, September 2014,

Author's Address

   Jon Peterson
   Neustar, Inc.

   Email: jon.peterson@neustar.biz

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