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Need for PSTN Internet Notification (PIN) Services [Page 1]
A. Brusilovsky
Internet Draft V. Gurbani
A. Jain
D. Varney
Lucent Technologies
Expires: November 1999
Need for PSTN Internet Notification (PIN) Services
A Proposal for a new Working Group
<draft-brusilovsky-pin-00.txt>
Status of this Memo This document is an Internet-Draft and is in full
conformance with 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
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The list of Internet-Draft Shadow Directories can be accessed at
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1. Abstract
The purpose of this Internet Draft is to start discussion on the
issues involved in PSTN Internet Notification (PIN), as part of
interconnecting IP and Public Switched Telephone Network (PSTN) with
the intent of converging existing and creating new hybrid PSTN and IP
services. PSTN Events Notification, based on open well-defined
protocols, will promote interoperability of both the networks and
systems built by different vendors. This Internet Draft is submitted
with the goal of becoming an informational RFC.
The rest of this document is as follows:
Section 2 briefly describes the PIN services.
Section 3 describes the scope of the proposed project by introducing
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its overall architecture and identifying the interfaces to be
standardized.
Sections 4, 5, and 6 respectively address security considerations,
supply references, and provide the authors address, as required by
[1].
Section 7 acknowledges individuals providing assistance in the
creation of this document.
2. PIN Description
Current PSTN/Internet Interfaces (PINT) WG addresses connection
arrangements through which Internet applications can request and
enrich PSTN (Public Switched Telephone Network) telephony services.
Some Interworking services require Notification and requests for
services that come from PSTN/IN. Essentially, these requests will be
"mirror image" of PINT requests.
To provide interoperability between PSTN and IP networks, it is very
important to ensure notification to IP network of the events
happening in PSTN.
PSTN/IN Call Flow is organized around actions or collections of
actions called Point-In-Call (PIC). Detection Points (DPs), which are
associated with the PICs, operate between the PICs, and can be the
basis for Notification Events for Interworking with IP network. IN
furnishes "Network Intelligence" to PSTN. Similarly, it can be
utilized to initiate Notification Events to IP network.
PSTN/IN events can be grouped into two categories:
Basic events:
1. Phone off-hook.
2. Phone on-hook.
3. Voice-mail Arrival.
4. Incoming Call Notification (Attempt to Terminate Call).
Advanced events:
1. Attempt to dial number (specific event can be Attempt to Dial ISP
Number.
2. Dropping Dialed Connection (i.e. dropping ISP call).
3. ISP Connection Made.
4. Attempt to Forward Call (forwarded end point could easily be VoIP
terminal).
5. Attempt to Subscribe/Unsubscribe for a PSTN Service (i.e. Set Up
Call Forwarding).
6. Attempt to Enter Conference. (Notification only)
7. Attempt to Exit Conference. (Notification only)
8. Identification of the Speaker (talking party) to the other
participants of the Voice (or multimedia) Conference (Notification
only).
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Examples of services that are based on PIN, or use PIN as one of the
building blocks are:
1. Internet Call Waiting. ICW is the capability to provide incoming
call notification and completion options when the Subscriber is on a
dial-up IP connection.
2. Internet Call Management. PSTN call notification and control
options (flexible call screening, forwarding, etc.), delivered to an
IP client.
3. Internet Conference Management. PSTN Teleconference notification
and management from an IP Client
4. Internet Conference Mediation. Pre-Teleconference (before an
actual connection is made) management service from an IP client.
5. Advanced Caller ID Delivery [7]. Ordered incoming call
notification to multiple Subscriber's dial-up IP connections.
6. Queue Management. Notification of the status and events of the
call queue, much needed for the IP-based Call Center Control.
7. Call Progress Delivery as part of PINT services. Classic PINT
services need notification of the Call Progress.
8. Internet Call Routing (ICR). Flexible routing and control over a
dial up PSTN call from an IP host.
3. Proposed Architecture
With the proliferation and wide acceptance of the Internet, and more
so with the convergence of the Internet and PSTN, there is an
increasing desire for events occurring on the PSTN domain to be
propagated to the Internet domain. The PIN protocol attempts to fill
this void. Entities on the Internet domain can receive the events
generated by the PSTN domain and act appropriately. The major
entities that comprise of the PIN protocol are the PIN gateway, the
PIN server and various PIN clients, as depicted in Figure 1.
---------
PSTN ; IP | PIN |
Domain ; Domain ----| Client |
; --------- | | |
; | PIN |---- ---------
; .-.-| Server |
--------- --------- : | |---- ---------
| | | PIN |-.-. --------- | | PIN |
| SNF |....| Gateway | ----| Client |
| | | |-.-. --------- | |
--------- --------- : | PIN | ---------
; .-.-| Server |
; | |
; ---------
;
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Figure A illustrates the functional scalable architecture that will
support PIN Services.
Legend: SNF - Service Notification Function
.-. - PIN Protocol
--- - Standard Client/Server Protocol or, potentially,
PIN Protocol
... - Standard PSTN/SS7/IN Protocol
Service Notification Function (SNF) is located in PSTN domain and
physically can reside in IN elements (SCP, SMS, SSP) that are
specialized servers, connected to switches and other PSTN elements
[3]. SNF (PSTN) informs the PIN Gateway of the PSTN events utilizing
traditional protocols (SS7/IN). PIN Gateway then relays these events
to one or more PIN Servers. PIN Server provides Subscription for
Notification Services and aggregates Notification events for PIN
Clients. A PIN Client is an IP end-point, which has subscribed for
PIN services with one or more PIN Servers.
PIN protocol is a specialized protocol used for communication between
the PIN gateway and PIN servers, which may, potentially, be used for
communications between PIN Servers and PIN Clients.
We are proposing new Working Group to be a "mirror image" of the PINT
WG, regarding direction of the requests for service and dealing with
Notification only.
Like PINT, PIN will not deal with IP Telephony, but rather provide
requests for services and Notifications from PSTN/IN to IP network in
order to augment, extend and enrich PSTN.
PIN WG will focus on the PIN Protocol Requirements and, optionally,
Definition of Notification Processing Language (NPL), a possible
extension to CPL, as well as defining connections of the Notification
Services to the IN DPs. NPL will allow to build new Notification
Services and provide means to describe Notification Filters for
Notification screening.
(Notification Filter example: Notification for an Attempt to Enter
Conference from a predefined number in the hours 9 through 17 only on
weekends and holidays.)
It is quite possible that existing or under development protocols
(i.e. SIP, PIP [8], MGCP, etc.) are sufficient to support PIN
Services, but that determination is for further study.
4. Security Considerations
PIN communications between the PIN Client, PIN Server, PIN Gateway
and the SNF may travel over the Internet. Thus it is essential to
provide encryption for the communications. In addition to
encryption, it is also necessary to provide authentication of both
the end points; i.e. SNF and PIN Client. PIN security has to
authenticate both end points and if the authentication succeeded,
encrypt the communications.
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PIN Security Requirements are, essentially, the same as PINT Security
Requirements outlined in [4]:
o Peer entity authentication to allow a communicating entity to prove
its identity to another in the network.
o Non-repudiation to account for all operations in case of doubt or
dispute. This could be achieved by logging all the information
pertinent to the transaction. In addition, the PSTN network will
maintain its own account of the transaction for generating bills.
o Confidentiality to avoid disclosure of information without the
permission of its owner. Although this is an essential requirement,
it is not particular to the proposed project.
o PIN Client profile verification to verify if the end user is
authorized to use a service.
In the course of the project execution, additional requirements are
likely to arise and many more specific security work items are likely
to be proposed and implemented.
Some of the PIN-specific security considerations:
o Cracking is a threat to any Service Provider (PSTN, Intranet,
Internet). It is real danger - phone companies are common targets
o Notification spoofing is one of the threats
o Existing mechanisms applied to the Internet can be implemented
o Stealing a Notification is a new type of security threat
5. References
[1] J. Postel, RFC 1543, "Instruction to RFC Authors". October 1993
[2] ITU-T Q.12xx Recommendation Series, Geneva, 1995.
[3] I. Faynberg, L. R. Gabuzda, M. P. Kaplan, and N. J. Shah, "The
Intelligent Network Standards, their Application to Services".
McGraw-Hill, 1996.
[4] S. Petrack, "IP Access to PSTN Services: Basic Service
Requirements, Definitions, and Architecture", Internet Draft
[5] Handley, Schulzrinne, Schooler, Rosenberg, "SIP: Session
Initiation Protocol", Internet Draft
[6] "Proposal for Internet Call Waiting Service using SIP", Internet
Draft
[7] L.Slutsman, "Advanced Internet Caller ID Delivery Service",
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Internet Draft
[8] J.Rosenberg, H.Schulzrinne, "SIP For Presence", Internet Draft
[9] S.Bradner, "The Internet Standards Process", RFC2026
6. Authors' Address
Alec Brusilovsky
E-mail: abrusilovsky@lucent.com
Telephone: +1-630-713-8401
Fax: +1-630-713-5840
Lucent Technologies
263 Shuman Blvd.
Naperville, IL 60566 USA
Vijay Gurbani
E-mail: vkg@lucent.com
Telephone: +1-630-224-0216
Fax: +1-630-713-5840
Lucent Technologies
263 Shuman Blvd.
Naperville, IL 60566 USA
Ajay Jain
E-mail: ajayjain@lucent.com
Telephone: +1-630-979-5218
Fax: +1-630-713-5840
Lucent Technologies
263 Shuman Blvd.
Naperville, IL 60566 USA
Doug Varney
E-mail: dvarney@lucent.com
Telephone: +1-630-979-8750
Fax: +1-630-713-5840
Lucent Technologies
263 Shuman Blvd.
Naperville, IL 60566 USA
Glossary
CPL Call Processing language
DN Destination Number
DP Detection Point
ICW Internet Call Waiting
IN Intelligent Network
MGCP Media Gateway Control Protocol
NPL Notification Processing Language
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Need for PSTN Internet Notification (PIN) Services [Page 7]
PIC Point-In-Call
PSTN Public Switched Telephone Network
SCP Service Control Point
SIP Session Initiation Protocol
SN Service Node
VoIP Voice over IP (Internet Protocol)
7. Acknowledgments
The authors would like to acknowledge Lawrence Conroy, Igor Faynberg,
Hui-Lan Lu, Shehryar Qutub, Jonathan Rosenberg and Lev Slutsman for
their contributing to the creation of this document.
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