Network Working Group H. Lu, Editor
Request for Comments: 2995 I. Faynberg
Category: Informational J. Voelker
M. Weissman
W. Zhang
Lucent Technologies
S. Rhim
J. Hwang
Korea Telecom
S. Ago
S. Moeenuddin
S. Hadvani
NEC
S. Nyckelgard
Telia
J. Yoakum
L. Robart
Nortel Networks
November 2000
Pre-SPIRITS Implementations of PSTN-initiated Services
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This document contains information relevant to the work underway in
The Services in the PSTN/IN Requesting InTernet Services (SPIRITS)
Working Group. It describes four existing implementations of
SPIRITS-like services from Korea Telecom, Lucent Technologies, NEC,
and Telia in cooperation with Nortel Networks. SPIRITS-like services
are those originating in the Public Switched Telephone Network (PSTN)
and necessitating the interactions of the Internet and PSTN.
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Surveying the implementations, we can make the following
observations:
o The ICW service plays the role of a benchmark service. All
four implementations can support ICW, with three specifically
designed for it.
o Session Initiation Protocol (SIP) is used in most of the
implementations as the base communications protocol between the
PSTN and Internet. (NEC's implementation is the only exception
that uses a proprietary protocol. Nevertheless, NEC has a plan
to support SIP together with the extensions for SPIRITS
services.)
o All implementations use IN-based solutions for the PSTN part.
It is clear that not all pre-SPIRITS implementations inter-operate
with each other. It is also clear that not all SIP-based
implementations inter-operate with each other given that they do not
support the same version of SIP. It is a task of the SPIRITS Working
Group to define the inter-networking interfaces that will support
interoperation of the future implementations of SPIRITS services.
Table of Contents
1. Introduction ................................................ 3
2. Service Description of Internet Call Waiting ................ 4
3. Korea Telecom's ICW Implementation .......................... 5
3.1. Overview .................................................. 5
3.2. Network Architecture ...................................... 6
3.3. Network Entities .......................................... 7
3.3.1. SSP ..................................................... 7
3.3.2. SCP ..................................................... 7
3.3.3. IP ...................................................... 7
3.3.4. ICW Server System ....................................... 7
3.3.5. ICW Client System ....................................... 8
3.3.6. Firewall ................................................ 9
3.4. Network Interfaces ........................................ 9
3.5. Protocols ................................................. 9
3.5.1. Intelligent Network Application Part Protocol (INAP) .... 9
3.5.2. PINT Protocol ........................................... 9
3.6. Example Scenarios ........................................ 11
3.6.1. ICW Service Subscription ................................ 11
3.6.2. ICW Client Installation ................................. 11
3.6.3. ICW Service Activation .................................. 12
3.6.4. Incoming Call Notification .............................. 14
3.6.5. Incoming Call Processing ................................ 15
3.6.5.1. Accept the Call ....................................... 16
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3.6.5.2. Forward the Call to Another Number .................... 18
3.6.6. ICW service De-activation ............................... 20
4. The Lucent Technologies Online Communications Center ........ 21
4.1 Overview ................................................... 21
4.2. Architecture .............................................. 22
4.3. Protocol and Operations Considerations .................... 25
5. NEC's Implementation ........................................ 28
5.1. Overview .................................................. 28
5.2. Architecture and Overall Call Flow ........................ 29
5.3. Interfaces and Protocols .................................. 31
5.3.1. SCP (SPIRITS Client)-SPIRITS Server Interface ........... 31
5.3.1.1. Connecting to SPIRITS Services ........................ 31
5.3.1.2. Message Types ......................................... 31
5.3.1.2.1 Connection Management Message Type ................... 31
5.3.1.2.2. Data Message Type ................................... 33
5.3.2. SPIRITS Server-ICW Client Application Interface ......... 34
5.3.3. Secure Reliable Hybrid Datagram Session Protocol
(SRHDSP) for Use .............................................. 35
5.3.3.1. Overview .............................................. 35
5.3.3.2. Session Initiation .................................... 35
5.3.3.3. Secure Reliable Datagram Transport .................... 36
5.3.3.4. Session closure ....................................... 36
6. Telia/Nortel's Implementation ............................... 36
6.1. Overview .................................................. 36
6.2. Architecture and Protocols ................................ 37
6.3. Security .................................................. 39
7. Security Considerations ..................................... 40
8. Conclusion .................................................. 40
9. References .................................................. 41
10. Authors' Addresses ......................................... 41
11. Full Copyright Statement ................................... 44
1. Introduction
This document contains information relevant to the work underway in
The Services in the PSTN/IN Requesting InTernet Services (SPIRITS)
Working Group. It describes four existing implementations of
SPIRITS-like services from Korea Telecom, Lucent Technologies, NEC,
and Telia in cooperation with Nortel Networks. SPIRITS-like services
are those originating in the Public Switched Telephone Network (PSTN)
and necessitating the interactions of the Internet and PSTN.
Invariably supported by the implementations examined in this document
is the Internet Call Waiting (ICW) service. With ICW, service
subscribers, while using their telephone lines for Internet access,
can be notified of incoming voice calls and specify how to handle the
calls over the same telephone lines.
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The document first gives a detailed description of the ICW service.
Then it proceeds to discuss each of the four implementations. The
final sections of the document contains security considerations, the
conclusion and references.
It is important to note that even though the term "SPIRITS server" is
used throughout the document, it has no universal meaning. Its
connotation depends on the context and varies from implementation to
implementation.
2. Service Description of Internet Call Waiting
Internet call waiting is the single service that is specifically
supported by all the implementations in question. In a nutshell, the
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.
The details of the ICW service lie in the ways that a waiting call
can be treated, which vary from implementation to implementation. In
this section, we describe the features that are supported by at least
one of the implementations. They are as follows:
o Incoming Call Notification - The subscriber is notified of an
incoming call over the Internet, without having any effect on the
telephone line that is being used by the modem. When a call comes
in, the subscriber is presented with a pop-up dialog box on the
PC. The dialog box may display any combination of the calling
party number, calling party name, and calling time. Note that the
display of the calling party name (or number) requires the
availability of the caller name (or number) delivery feature.
o Online Incoming Call Disposition - Once informed of the incoming
call, the subscriber has various options (indicated in the pop-up
window) for handling the call. Possible options are:
+ Accepting the call over the PSTN line, thus terminating the
Internet (modem) connection
+ Accepting the call over the Internet using Voice over IP (VoIP)
+ Rejecting the call
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+ Playing a pre-recorded message to the calling party and
disconnecting the call
+ Forwarding the call to voice mail
+ Forwarding the call to another number
+ Rejecting (or Forwarding) on no Response - If the subscriber fails
to respond within a certain period time after the dialog box has
been displayed, the incoming call can be either rejected or
handled based on the treatment pre-defined by the subscriber.
o Automatic Incoming Call Disposition - Incoming calls are
automatically handled based on dispositions pre-defined by the
subscriber without his or her real-time intervention. The
subscriber can pre-define the default disposition (e.g., re-
directed to voice mail) for general calls as well as customized
dispositions for calls from specific numbers. In the latter case,
the subscriber selects a particular disposition for each
originating number and stores this information in a profile. When
a call comes in, the subscriber won't be presented the call but
can examine the treatment and outcome of the call from the caller
log (as described in the call logging bullet). Naturally, this
feature also allows the subscriber to specify the desired
treatment for calls originating from private or unpublished
numbers.
o Multiple Call Handling - Multiple calls can arrive during call
disposition processing. With multiple call handling, the
subscriber is notified of the multiple calls one by one.
o Call Logging - A detailed log of the incoming calls processed
during the ICW service is kept. Typical information recorded in
the log include the incoming call date and time, calling party
number, calling party name, and call disposition.
3. Korea Telecom's ICW Implementation
3.1. Overview
Korea Telecom's ICW implementation supports most of the features
described in Section 2. (The major exception is the feature of
receiving the incoming call over the Internet using voice over IP.)
In addition, the Korea Telecom implementation supports flexible
activation and de-activation of the ICW service:
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o Automatic Activation/De-activation - When Internet dial-up
connection is set up, the ICW service is activated or de-activated
automatically.
o Manual Activation/De-activation - The subscriber can de-activate
the ICW service manually when call notification is not desired
during the Internet dial-up session and activate it when needed.
3.2. Network Architecture
Figure 1 depicts the network architecture of the Korea Telecom ICW
service. The Service Switching Point (SSP), Service Control Point
(SCP), and Intelligent Peripheral (IP) are legacy PSTN IN elements
based on IN CS-1. In contrast, both the ICW Server System and the
ICW Client System are new network elements that are installed in the
Internet domain to support of the ICW service.
+---------------------------+ | +--------------+
|+--------+propr-+---------+| PINT | |(Proxy Server)| PINT
||(ICW SL)|ietary|(UAC/UAS)||--- -||-----| ICW |----+
||SCF/SDF |------| SCGF || firewall |Server System | |
|+--------+ i/f +---------+| | +------------- + |
| SCP | | |
+------+--------------+-----+ | |
|INAP |INAP | firewall=====
| | | |
+---+---+ +---+---+ |
| IP | | SSP | |
+-------+ +---+---+ +-------------+
| +---+ | (UAC/UAS) |
+---+---+ || || | ICW |
|---------| LEX |-------------- + + |Client System|
+---+ +-------+ +++++----+-------------+
|| || (callee)
+ + ICW Subscriber's Phone and PC
+++++
(caller)
INAP : Intelligent Network Application Protocol
PINT : PSTN/Internet Interworking Protocol
SL : Service Logic
UAS : User Agent Server
UAC : User Agent Client
Figure 1: Network Architecture of the Korea Telecom ICW Service
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3.3. Network Entities
3.3.1. SSP
The SSP performs the Service Switching Function (SSF) and Call
Control Function (CCF). When detecting that the called party is busy
(T_Busy), the SSP sends a query to the SCP and processes the call
under the control of the SCP.
3.3.2. SCP
The SCP performs the Service Control Function (SCF) and Service Data
Function (SDF). It, when queried, instructs the SSP to process the
call based on the service logic. In the case of the ICW service, the
service logic ultimately governs the notification of a waiting call
to an online ICW subscriber and the disposition of the call. In
addition, the SCP perfor