DISPATCH                                                  H. Schulzrinne
Internet-Draft                                                       FCC
Intended status: Standards Track                      September 30, 2016
Expires: April 3, 2017

              SIP Call-Info Parameters for Labeling Calls


   Called parties often wish to decide whether to accept, reject or
   redirect calls based on the likely nature of the call.  For example,
   they may want to reject unwanted telemarketing or fraudulent calls,
   but accept emergency alerts from numbers not in their address book.
   This document describes SIP Call-Info parameters and a feature tag
   that allow originating, intermediate and terminating SIP entities to
   label calls as to their type, spam probability and references to
   additional information.

Status of This Memo

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   This Internet-Draft will expire on April 3, 2017.

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   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Normative Language  . . . . . . . . . . . . . . . . . . . . .   3
   3.  Parameters  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  SIP Call-Info Header Field Parameters . . . . . . . . . .   5
     5.2.  SIP Global Feature-Capability Indicator . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   In many countries, an increasing number of calls are unwanted
   [RFC5039], as they might be fraudulent, illegal telemarketing or the
   receiving party does not want to be disturbed by, say, surveys or
   solicitation by charities.  Currently, called parties have to rely
   exclusively on the caller's number or, if provided, caller name, but
   unwanted callers may not provide their true name or use a name that
   misleads, e.g., "Cardholder Services".  On the other hand, many calls
   from unknown numbers may be important to the called party, whether
   this is an emergency alert from their emergency management office or
   a reminder about a doctor's appointment.  Since many subscribers now
   reject all calls from unknown numbers, such calls may also be
   inadvertently be left unanswered.  Users may also install smartphone
   apps that can benefit from additional information in making decisions
   as to whether to ring, reject or redirect a call.

   This document describes a new set of optional parameters and usage
   for the SIP [RFC3261] Call-Info header field, purpose "info" [TBD:
   re-use or define new purpose?], for labeling the nature of the call.
   The header field may be inserted by the call originator, an
   intermediate proxy or B2BUA or the terminating carrier, based on
   assertions by the caller, number-indexed databases, call analytics or
   other sources of information.  The SIP provider serving the called
   party MUST remove any parameters enumerated in this specification
   that it does not trust.  The Call-Info header field MAY be signed
   using a future "ppt" extension to [I-D.ietf-stir-rfc4474bis].  To
   ensure that an untrusted originating caller does not mislead the

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   called party, a new feature tag, sip.call-info.spam, indicates
   whether the terminating carrier will remove untrusted information.

   SIP entities MUST add a new Call-Info header field, rather than add
   parameters to an existing one.  There MAY be several Call-Info header
   fields in one request.

   As defined in [RFC3261], the Call-Info header field contains a URI
   that can provide additional information about the caller or call.
   For example, many call filtering services provide a web page with
   crowd-sourced information about the calling number.  If the entity
   inserting the header field does not have information it wants to link
   to, it MUST use an empty data URL [RFC2397] as a placeholder, as in
   "data:".  (The Call-Info header field syntax makes the URI itself

   Providers may also find the SIP Priority header (Section 20.26) field
   useful in helping called parties decide how to respond to an incoming

2.  Normative Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in BCP 14, RFC 2119

3.  Parameters

   All of the parameters listed below are optional and may appear in any
   combination and order.

   spam  The spam parameter indicates the estimated probability that the
      call is unwanted by the called party, expressed as a whole-number
      percentage between 0 and 100, inclusive, with larger numbers
      indicating a higher probability.  The computation of the estimate
      is beyond the scope of this specification.  If not specified, the
      entity inserting the Call-Info information is making no claims
      about the likelihood of being unwanted.

   type  The type parameter indicates the type of the call or caller.
      It is drawn from an extensible set of values, with the initial set
      listed below.  Gateways to analog phone systems MAY include the
      label in caller name (CNAM) information.  Automated call
      classification systems MAY use this information as one factor in
      deciding how to handle the call.  Calls SHOULD be labeled with
      types that may make it more likely that the caller will answer
      (e.g., for alert and health-related calls) if the entity inserting

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      the information is confident that the calling party number is
      valid, e.g., because the request has been signed

   reason  The reason parameter provides free-text information about the
      source of the type or spam parameter and is meant to be used for
      debugging, rather than for display to the end user.  For example,
      it may indicate the name of an external information source, such
      as a list of known emergency alerters.

   source  The source parameter identifies the entity, by host name,
      domain or IP address, that inserted the parameters above.  It uses
      the "host" ABNF syntax.

   The following initial set of types are defined.  The call types are
   generally based on the caller's telephone number or possibly an
   assertion by a trusted caller, as the content cannot be not known.
   The definitions are meant to be informal and reflect the common
   understanding of subscribers who are not lawyers.  Other strings may
   be used; there does not appear to be a need for defining vendor-
   defined strings as the likelihood of confusion between a service-
   provider-specific usage and a later extension to the list appears
   low.  Additional labels are registered with IANA.

   business  Calls placed by businesses, i.e., an entity or enterprise
      entered into for profit.  This type is used if no other, more
      precise, category fits.

   debt-collection  Calls related to collecting of debt owed or alleged
      to be owed by the called party.

   emergency-alert  Calls that provide the recipient information
      regarding an emergency.

   fraud  The call is considered to be fraudulent.

   government  A call placed by a government entity, if no more specific
      label such as "health" or "debt-collection" is known or applies.

   health  Informational calls by health plans, health care
      clearinghouses or health care provider, where health care means
      care, services, or supplies related to the health of an

   informational  Calls intended to convey information to the called
      party about a transaction such as package delivery, appointment
      reminder, order confirmation.  This call type is only used if the

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      calling party believes to have an established business
      relationship with the called party.

   not-for-profit  A call placed by a not-for-profit organization,
      including for soliciting donations or providing information.

   personal  A non-business, person-to-person, call, e.g., from a
      residential line or personal mobile number.

   political  Calls related to elections or other political purposes.

   public-service  Calls that provide the recipient information
      regarding public services, e.g., school closings.

   spam  A call that is likely unwanted, if not otherwise classified.

   spoofed  The calling number for this call has been spoofed.

   survey  A call that solicits the opinions or data of the called

   telemarketing  Calls placed in order to induce the purchase of a
      product or service to the called party.

   trusted  The call is being placed by a trusted entity and falls
      outside the other categories listed.  This may include call backs,
      e.g., from a conferencing service, or messages from
      telecommunication carriers and utilities.

4.  Example

   "Call-Info: <http://wwww.example.com/5974c8d942f120351143>
   ;source=carrier.example.com ;purpose=info ;spam=85 ;type=fraud
   ;reason="FTC list""

5.  IANA Considerations

5.1.  SIP Call-Info Header Field Parameters

   This document defines the 'spam', 'type', 'reason' and 'source'
   parameters in the Call-Info header in the "Header Field Parameters
   and Parameter Values" registry defined by [RFC3968].

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    | Header Field | Parameter Name | Predefined Values | Reference  |
    | Call-Info    | reason         | No                | [this RFC] |
    | Call-Info    | source         | No                | [this RFC] |
    | Call-Info    | spam           | No                | [this RFC] |
    | Call-Info    | type           | Yes               | [this RFC] |

5.2.  SIP Global Feature-Capability Indicator

   This document defines the feature capability sip.call-info.spam in
   the "Global Feature-Capability Indicator Registration Tree" registry
   defined in [RFC6809].

   Name  sip.call-info.spam

   Description  This feature-capability indicator when used in a
      REGISTER response indicates that the server will add, inspect,
      alter and possibly remove the Call-Info header field parameters
      defined in the reference.

   Reference  [this RFC]

6.  Security Considerations

   The security considerations in [RFC3261] (Section 20.9) apply.  A
   user agent MUST ignore the parameters defined in this document unless
   the SIP REGISTER response contained the sip.call-info.spam feature
   capability.  SIP entities MUST remove any parameters defined here
   that were provided by untrusted third parties.

7.  Acknowledgements

   Jim Calme and other members of the Robocall Strikeforce provided
   helpful comments.

8.  References

8.1.  Normative References

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

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   [RFC2397]  Masinter, L., "The "data" URL scheme", RFC 2397,
              DOI 10.17487/RFC2397, August 1998,

   [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,

   [RFC3968]  Camarillo, G., "The Internet Assigned Number Authority
              (IANA) Header Field Parameter Registry for the Session
              Initiation Protocol (SIP)", BCP 98, RFC 3968,
              DOI 10.17487/RFC3968, December 2004,

   [RFC6809]  Holmberg, C., Sedlacek, I., and H. Kaplan, "Mechanism to
              Indicate Support of Features and Capabilities in the
              Session Initiation Protocol (SIP)", RFC 6809,
              DOI 10.17487/RFC6809, November 2012,

8.2.  Informative References

              Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
              "Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-13
              (work in progress), September 2016.

   [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>.

Author's Address

   Henning Schulzrinne
   450 12th Street SW
   Washington, DC  20554

   Email: henning.schulzrinne@fcc.gov

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