Service in the PSTN/IN Requesting InTernet Service (spirits)

Last Modified: 2003-03-31


Steven Bellovin <>
Alec Brusilovsky <>

Transport Area Director(s):

Allison Mankin <>
Jon Peterson <>

Transport Area Advisor:

Jon Peterson <>

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Description of Working Group:

The Services in the PSTN/IN Requesting InTernet Services (SPIRITS)
Working Group addresses how services supported by IP network entities
can be started from IN (Intelligent Network) requests, as well as the
protocol arrangements through which PSTN (Public Switched Telephone
Network) can request actions to be carried out in the IP network in
response to events (IN Triggers) occurring within the PSTN/IN.  SPIRITS
concerns architecture and protocols for secure transport of IN trigger
information (requests for actions, as well as plain event
including parameters) from PSTN/IN to the IP network, and optional
responses from the IP network back to the PSTN/IN.

The SPIRITS architecture includes, but not limited to, three
independent entities:

- the SPIRITS client

- the SPIRITS server

- the PSTN/IN requesting system

The SPIRITS client is the entity that requests notification or some
actions to be performed in the IP network.  The SPIRITS server is the
entity that receives notifications or requests from the PSTN/IN and
returns optional responses back to the PSTN/IN, while initiating
execution of the services requested in the IP domain.  The SPIRITS
server and PSTN/IN requesting sytem both reside in the IP domain, with
PSTN/IN entity on the boundary between the IP and PSTN/IN networks. 
presence of three independent parties implies a requirement to support
complex trust models. Accordingly, the security architecture must
support limited trust between the parties.

The parameters passed in any SPIRITS Service request are limited
to information available from PSTN/IN entities. An example of such a
service is Internet Call Waiting: on an incoming PSTN call, an IP node
is notified of the call and can then carry out some actions. Definition
of any information or data within the PSTN is the responsibility of the
ITU-T and so is out of scope for SPIRITS.

The target of this working group is to describe building blocks for
PSTN-IP services that start from PSTN/IN requests, and not to
standardize the PSTN-IP services themselves.  The WG will focus on an
event-oriented design, rather than a service-oriented design.  Specific
services to be considered initially as examples are: (1) Incoming Call
Notification (Internet Call Waiting); (2) Internet Caller-Id Delivery;
and (3) Internet Call Forwarding and "Follow Me".


o Produce an Informational RFC that describes current practices
  for supporting the services in question.

o Produce an Informational RFC on the overall architecture of
  SPIRITS-type services.

o Develop a Standards Track RFC that specifies a protocol by
  which PSTN Intelligent Network Service Nodes (or any other
  node that implements the Service Control Function) can
  request services of IP hosts, and which can return status
  indications to the PSTN/IN.

o Consider security and privacy issues relating to providing
  functions of SPIRITS type. In particular, understand any
  threats posed by this technology and address them in the
  proposed standard.

o Develop a standards track RFC for a SPIRITS MIB to support the
  service management protocol between Internet applications and the
  PSTN/IN Service Management System.  The MIB is to conform to SNMP

SPIRITS will collaborate with other IETF WG's working on similar issues
and having expertise in PSTN/IP interworking (IPTEL, MMUSIC, PINT,
SPIRITS will also establish communication with other relevant standard
bodies (ITU-T SG11).

Goals and Milestones:

Done    Current Practice document submitted for publication as Informational
Done    Protocol Requirements Document submitted for publication as an Informational RFC
Done    SPIRITS Architecture document submitted for publication as an Informational RFC
Oct 02    On selection of IN parameters for the SPIRITS Protocol document submitted for publication as an Informational RFC
Dec 02    SPIRITS protocol submitted for publication as Proposed Standard
Jan 03    SPIRITS MIB submitted for publication as Proposed Standard

No Current Internet-Drafts

Request For Comments:

Pre-Spirits Implementations of PSTN-initiated Services (RFC 2995) (96427 bytes)
The SPIRITS Architecture (RFC 3136) (19241 bytes)
SPIRITS Protocol Requirements (RFC 3298) (36560 bytes)
The SPIRITS (Services in PSTN requesting Internet services) Protocol (RFC 3910) (0 bytes)