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Versions: 00 01 02 03 rfc3136                                           
Network Working Group                                   L. Slutsman (Ed.)
Internet Draft                                                  AT&T Labs
<draft-ietf-spirits-architecture-01.txt>                      I. Faynberg
Expires August  2001                                                H. Lu
                                                              M. Weissman
                                                      Lucent Technologies

                           The SPIRITS Architecture


Status of this Memo

   This document is an Internet-Draft and is in full conformance wit all
   provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering Task
   Force (IETF), its areas, and its working groups. Note that other groups
   may also distribute working documents as Internet-Drafts.
   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


                                 Abstract

   This document describes the architecture for supporting SPIRITS
   services, which are those originating in the PSTN and necessitating the
   interactions between the PSTN and the Internet. (Internet Call Waiting,
   Internet Caller-ID Delivery, and Internet Call Forwarding are examples
   of SPIRIT services.) Specifically, it defines the components
   constituting the architecture and the interfaces between the components.


1. Introduction

   This document describes the architecture for supporting SPIRITS
   services, which are those originating in the PSTN and necessitating the
   interactions between the PSTN and the Internet. (Internet Call Waiting,
   Internet Caller-ID Delivery, and Internet Call Forwarding are examples
   of SPIRIT services.) Specifically, it defines the components
   constituting the architecture and the interfaces between the
   components.

   The rest of the document is organized as follows:
   + Section 2 describes example SPIRITS services from the end-user point
   of view;
   + Section 3 describes the SPIRITS architecture;



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SPIRITS Architecture                                            [Page 2]


   + Section 4 contains security consideration;
   + Section 5 contains acknowledgments;
   + Section 6 contains references; and
   + Appendix contains the figure.


2. Brief Description of Example SPIRITS Services

   To illustrate the motivation for the overall SPIRIT architecture,
   this section provides a brief description of the example SPIRITS
   services:
   + Internet Call Waiting (ICW),
   + Internet Caller-ID Delivery, and
   + Internet Call Forwarding.

   These services are considered from the end-user point of view under
   the assumptions below:

   + Service subscription (or cancellation) is a separate process and
   may be done over the telephone, via postal mail, or over the Web.

   + The subscriber's IP host (e.g., a PC) is loaded with the necessary
   software [including a Personal Identification Number (PIN) and the IP
   addresses of the SPIRITS servers] for realizing the SPIRITS services.
   The software may be sent by postal mail or downloaded from the Web.

   + The subscriber activates a SPIRITS service by an act of service
   session registration, which can take place anytime after he (or she)
   is connected to the Internet. The subscriber may specify the life
   span of the session. As soon as the session ends, the SPIRITS service
   is deactivated. Naturally, the subscriber should also be able to
   deactivate a SPIRITS service anytime during the service session.

   For certain services (such as ICW or Caller-ID Delivery) the
   assumption is that the service subscriber has a single telephone line
   and a PC, which is connected to the Internet via this telephone.
   (Only under this assumption these services make sense.) Nevertheless,
   in other services (such as Web-based Call Center, in which a call
   center assistant could re-direct or reject a call presented in a
   pop-up window) this assumption may be unnecessary or even
   inapplicable.

2.1 Internet Call Waiting (ICW)

   The Internet call waiting service enables a subscriber engaged in an
   Internet dial-up session to

      o be notified of an incoming call to the very same telephone line
        that is being used for the Internet connection;

      o specify the desirable treatment of the call; and

      o have the call handled as specified.




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SPIRITS Architecture                                            [Page 3]


   The details of the ICW service lie in the ways that a waiting call
   can be treated [1]. Typical ways for handling a call include:

   + Accept the incoming call over the PSTN by terminating the Internet
   connection. (As switching cannot be done immediately, the caller may
   hear an opening announcement followed by the "ringing" tone.)

   + Forward the incoming call to another telephone number. The
   subscriber will remain connected to the Internet, while the caller
   will hear an announcement indicating the call is being forwarded and
   eventually be connected to the new destination number.

   + Accept the incoming call by voice over IP. The subscriber will
   answer the incoming call via the already established Internet
   connection. (The proposed SPIRITS architecture, however, does not
   reflect this feature.)

   + Redirect the incoming call to voice mail. The subscriber will
   remain connected to the Internet, while the caller will hear an
   announcement inviting him (or her) to leave a message.

   + Play a pre-recorded message to the calling party and disconnect the
   call. The subscriber will remain connected to the Internet.

   + Reject the incoming call. The subscriber will remain connected to
   the Internet, while the caller will hear an announcement rejecting
   the call.

   The subscriber may specify the call treatment on the fly when
   notified of an incoming call. Alternatively, the subscriber may
   specify a priori a general treatment for all calls (e.g., re-directed
   to voice mail) or call treatments tailored to the origination
   numbers. As a result, when a call comes in, the subscriber won't be
   presented the call but can examine afterwards the treatment and
   outcome of the call from the log that is kept for all the calls
   processed during the ICW service. Typical information recorded in the
   log includes the incoming call date and time, calling party number,
   calling party name, and call disposition.

2.2 Internet Caller-ID Delivery

   This service allows the subscriber to see the caller's number or name
   or both while being connected to the Internet. If the subscriber has
   only one telephone line and is using the very line for the Internet
   connection, the service is a subset of the ICW service and follows
   the relevant description in Section 2.1. Otherwise, the subscriber's
   IP host serves as an auxiliary device of the telephone to which the
   call is first sent.

2.3 Internet Call Forwarding

   The Internet call forwarding service allows a service subscriber to
   forward an incoming call to another telephone number while being
   connected to the Internet. If the subscriber has only one telephone



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SPIRITS Architecture                                            [Page 4]


   line and is using the very line for the Internet connection, the
   service is a subset of the ICW service and follows the relevant
   description in Section 2.1. Otherwise, the subscriber's IP host
   serves as an auxiliary device of the telephone to which the call is
   first sent.


3. SPIRITS Architecture

   Figure 1 of the Appendix depicts the SPIRITS architecture, which
   includes the following entities:

   1. Service Control Function (SCF) [2], which executes service logic,
   interacts with the entities in the IP domain (e.g., the SPIRITS
   Gateway and PINT Server) through the SPIRITS Client, and instructs
   the switches on how to complete a call. Physically, the SCF may be
   located in either stand-alone general-purpose computers called
   Service Control Points (SCPs) or specialized pieces of equipment
   called Service Nodes (SNs) [2].

   2. Service Switching Function (SSF) [2], which normally resides in a
   switch and is responsible for the recognition of Intelligent Network
   (IN) triggers and interactions with the SCF.

   3. SPIRITS Client, which is responsible for receiving PSTN requests
   from the SCF as well as sending responses back. It may be co-located
   with the SCF. If not, it communicates with the SCF over the D
   interface.

   4. PINT Server, which receives PINT requests from the PINT Client and
   relays them to the PSTN for execution over the E interface.

   5. SPIRITS Gateway, which is co-located with the PINT Server or
   PINT Gateway (or both when they are co-located as assumed here
   for simplicity) and serves as an intermediary between the SPIRITS
   Server and SPRITS Client via the B and C interfaces, respectively.

   6. PINT Client, which resides in the subscriber's IP host and is
   responsible for initiating PINT requests, which are sent to the PINT
   server over the A interface.

   7. SPIRITS Server, which terminates PSTN requests and is responsible
   for all interactions (e.g., incoming call notification and relaying
   the call treatment) between the subscriber and the SPIRITS Gateway.

   The rest of the Section describes the interfaces between the entities
   in detail.

3.1 Interface A

   This interface is used for sending PINT requests to PINT Server. Its
   principal use is for service session registration and as a result
   activation of a SPIRITS service (see Section 2). In addition, this
   interface may be used for service subscription.




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SPIRITS Architecture                                            [Page 5]


3.2 Interface B

   This interface serves two main purposes: 1) to notify the subscriber
   of incoming calls together with the calling number and name, if
   available; and 2) to send to the SPRITS Gateway the subscriber's
   choice of call disposition specified on the fly.

3.3 Interface C

   This interface is used for communications between the SPIRITS Client
   and SPIRITS Gateway.  The SPIRITS Gateway may in turn communicate
   with the SPIRITS Server, or may act as a virtual server, terminating
   the requests without sending them down to the SPIRITS Server.

3.4 Interface D

   This interface is for communications between the SPIRITS Client and
   the SCF. Specifically, from the SCF to the SPIRITS Client, the
   parameters associated with the applicable IN triggers are sent. From
   the SPIRITS Client to SCF, the subscriber's call disposition is sent.
   The SCF "transforms" the user's disposition into appropriate actions,
   such as playing an announcement to the caller, and resuming the
   suspended call processing in the SSP.

3.5 Interface E

   This interface is for sending PINT requests to the SCF for execution.


4. Security Considerations

   It is assumed that the interface C is between trusting entities. In
   addition, the assumption that the PINT Client and SPIRITS Server are
   collocated dictates that the security considerations for the A and B
   interfaces are exactly the same.


5. Acknowledgments

   We would like to thank Alec Brusilovsky, Jorgen Bjorkner, Jim Buller,
   Lawrence Conroy, Jorge Gato, Dave Hewins, Naoto Makinae, and Dave
   Shrader for their comments and input.

6. References

   [1] Lu, H. (Editor), I. Faynberg, J. Voelker, M. Weissman, W. Zhang,
   S. Rhim, J. Hwang, S. Ago, S. Moeenuddin, S. Hadvani, S. Nyckelgard,
   J. Yoakum, and L. Robart, "Pre-SPIRITS Implementations of PSTN-
   Initiated Services ", RFC 2995.

   [2] Faynberg, I., L. Gabuzda, M. Kaplan, and N.Shah, "The Intelligent
   Network Standards: Their Application to Services", McGraw-Hill, 1997.





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SPIRITS Architecture                                            [Page 6]


Appendix




                                            ......................
            +----------------+              .                    .
            | +------------+ |              .   +------------+   .
            | |            | |       A      .   |            |   .
            | | PINT Client|********************|PINT Server/|********
            | |            | |              .      Gateway   |       *
            | +------------+ |              .   +------------+   .   *
            |                |              .                    .   *
            |  Subscriber's  |              .                    .   *
            |                |              .                    .   *
            |  IP Host       |              .                    .   *
            |                |              .   +------------+   .   *
            | +------------+ |              .   | SPIRITS    |   .   *
            | | SPIRITS    | |       B      .   | Gateway    |   .   *
            | | Server     |********************|            |   .   * E
            | |            | |              .   +------------+   .   *
            | +------------+ |              .          *         .   *
            +----------------+              .          *         .   *
                                            ...........*..........   *
                 //-------\\                           *             *
              ///           \\\                        *             *
             |   Subscriber's  |                       *  C          *
             |   Telephone     |                       *             *
              \\\           ///                        *             *
                \\ -------//                           *             *
                     *                                 *             *
                     *                                 *             *
           ++++++++++++++++++++++++++  PSTN   ++++++++++++++++++++++++++
                     *                                 *             *
                     *                                 *             *
                     *                          +------------------+ *
                     * Line                     | SPIRITS Client   | *
                     *                          |                  | *
            +--------------------+          +---+----- D  ---------+-*+
            |                    | INAP/SS7 |                         |
            |Service Switching   ************Service Control Function |
            |    Function        |          |                         |
            |                    |          +-------------------------+
            |                    |
            |                    |
            +--------------------+

                  Figure 1:  SPIRITS Architecture


Author's Addresses

      Igor Faynberg
      Lucent Technologies
      Room 4D-601A
      101 Crawfords Corner Road
      Holmdel, NJ 07733-3030 US
      E-mail: faynberg@lucent.com



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SPIRITS Architecture                                            [Page 7]

      Telephone: +1 732 949 0137

      Hui-Lan Lu
      Lucent Technologies Room 4C-607A
      101 Crawfords Corner Road
      Holmdel, NJ 07733-3030 US
      E-mail: huilanlu@lucent.com
      Telephone: +1 732 949 0321

      Mark Weissman
      Lucent Technologies
      Room NE406B
      200 Lucent Lane
      Cary, NC 27511
      E-mail: maw1@lucent.com
      Telephone: +1 919 463 3258

      Lev Slutsman
      AT&T Labs
      Room D5-3D26
      200 Laurel Avenue
      Middletown, NJ 07748
      E-mail: slutsman@att.com
      Telephone: 732-420-3756


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<draft-ietf-spirits-architecture-01.txt>                  August  2001