📄 rfc2458.txt
字号:
Netowrk Working Group H. Lu
Request for Comments: 2458 Editor
Category: Informational M. Krishnaswamy
Lucent Technologies
L. Conroy
Roke Manor Research
S. Bellovin
F. Burg
A. DeSimone
K. Tewani
AT&T Labs
P. Davidson
Nortel
H. Schulzrinne
Columbia University
K. Vishwanathan
Isochrome
November 1998
Toward the PSTN/Internet Inter-Networking
--Pre-PINT Implementations
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 (1998). All Rights Reserved.
Abstract
This document contains the information relevant to the development of
the inter-networking interfaces underway in the Public Switched
Telephone Network (PSTN)/Internet Inter-Networking (PINT) Working
Group. It addresses technologies, architectures, and several (but by
no means all) existing pre-PINT implementations of the arrangements
through which Internet applications can request and enrich PSTN
telecommunications services. The common denominator of the enriched
services (a.k.a. PINT services) is that they combine the Internet and
PSTN services in such a way that the Internet is used for non-voice
interactions, while the voice (and fax) are carried entirely over the
PSTN. One key observation is that the pre-PINT implementations, being
developed independently, do not inter-operate. It is a task of the
PINT Working Group to define the inter-networking interfaces that
Lu, et. al. Informational [Page 1]
RFC 2458 Pre-PINT Implementations November 1998
will support inter-operation of the future implementations of PINT
services.
Table of Contents
1. Introduction ....................................... 3
2. Terminology ....................................... 3
3. PINT Services ....................................... 4
4. Architectural Overview ............................... 5
4.1 Public Switched Telephone Network ............... 5
4.2 Pre-PINT Systems ............................... 9
5. IN-Based Solutions ............................... 20
5.1 The Lucent System ............................... 20
5.1.1 Roles of the Web Server, Service Node, and SMS ....... 20
5.1.2 A Click-to-Dial-Back Service Scenario ............... 21
5.1.3 Web Server-Service Node Interface ............... 22
5.1.4 Web Server-SMS Interface and SNMP MIB ............... 24
5.1.5 Security Considerations ........................... 26
5.2 Siemens Web Call Center ........................... 27
5.2.1 Service Description ............................... 27
5.2.2 Implementation ................................... 29
5.2.3 Derived Requirements/Lessons ..................... 35
6. Alternative Solutions ............................... 37
6.1 The AT&T System ..................................... 37
6.1.1 High Level Architecture ............................ 38
6.1.2 IP Client to CallBroker Interface .................. 39
6.1.3 Protocol ........................................... 40
6.1.4 APIs Exposed to the IP Client ..................... 41
6.1.5 Voice-Bridge Control API ........................ 41
6.2 Simple Computer Telephony Protocol ............... 41
6.2.1 Overview ........................................... 41
6.2.2 How SCTP Fits in with the Reference PINT Services .. 42
7. Session Initiation Protocol--An Emerging Standard .. 43
7.1 Overview ....................................... 43
7.2 SIP Protocol ....................................... 44
7.3 SIP Entities ....................................... 45
7.4 Providing Call Control Functionality ............... 46
8. Overall Security Considerations ..................... 47
9. Conclusion ....................................... 48
10. Acknowledgments ................................... 48
11. Appendix ....................................... 49
11.1 PSTN/IN 101 ....................................... 49
11.1.1 Public Switched Telephone Network ............... 49
11.1.2 Intelligent Network ............................... 51
11.2 Call Center Features ............................. 54
Lu, et. al. Informational [Page 2]
RFC 2458 Pre-PINT Implementations November 1998
12. References ....................................... 56
Authors' Addresses ......................................... 57
Full Copyright Statement .................................. 60
1. Introduction
This document contains the information relevant to the development of
the inter-networking interfaces underway in the Public Switched
Telephone Network (PSTN)/Internet Inter-Networking (PINT) Working
Group. It addresses technologies, architectures, and several (but by
no means all) existing pre-PINT implementations of the arrangements
through which Internet applications can request and enrich PSTN
telecommunications services. The common denominator of the enriched
services (a.k.a. PINT services) is that they combine the Internet and
PSTN services in such a way that the Internet is used for non-voice
interactions, while the voice (and fax) are carried entirely over the
PSTN.
The organization of the document is as follows. First, the basic
terminology and a short "intuitive" description of the PINT services
are provided. The rest of the information deals, in one way or the
other, with the pre-PINT support of these services where they are
used as a benchmark. Thus, an architectural overview common to all
present solutions is presented. The flow of the document then
divides into two streams: one is dedicated to the Intelligent Network
(IN)-based solutions; the other explores alternative means (i.e.,
CallBroker and Computer-Telephony Integration (CTI) approach). At
this point, the emerging standards are explored, in particular, the
Session Initiation Protocol (SIP), which promises an elegant solution
to the PINT problem. Each of the above developments is addressed in a
respective section. The final sections of the document contain the
overall security considerations, conclusion, acknowledgments,
appendix, and a set of references. The security section summarizes
the PINT security requirements derived from the pre-PINT experiences
and the appendix presents a tutorial on the PSTN, IN, and Call Center
functions.
2. Terminology
This document uses the following terminology:
Authentication -- verification of the identity of a party.
Authorization -- determination of whether or not a party has the
right to perform certain activities.
PINT Gateway -- the PSTN node that interacts with the Internet.
Lu, et. al. Informational [Page 3]
RFC 2458 Pre-PINT Implementations November 1998
User or Customer -- the person who asks for a service request to be
issued. In the context of PINT Services, this person will use an
Internet host to make his or her request. The term "user" is also
used to describe a host originating the PINT service request on
behalf of this person.
3. PINT Services
This document addresses four services initially identified by the
PINT Working Group and presently supported by pre-PINT
implementations. These services are: click-to-dial-back, click-to-
fax, click-to-fax-back and voice-access-to-content.
Note that the word "click" should not be taken literally. It is
rather used to point out that initiation of the related services
takes place on the Internet, where point and click are the most
prevalent user actions. In other words, a service request could
originate from any type of IP-based platforms. There is no
implication that these services must be implemented by a device
within the PSTN or the Internet running a Web server.
The common denominator of the PINT services is that they combine the
Internet and PSTN services in such a way that the Internet is used
for non-voice interactions, while the voice (and fax) are carried
entirely over the PSTN. (An example of such a service is combination
of a Web-based Yellow Pages service with the ability to initiate PSTN
calls between customers and suppliers in a manner described in what
follows.)
Some of the benefits of using the PSTN are high quality of the voice,
an ability to route the call to different locations depending on
pre-set criteria (for example, time of the day, day of the week, and
geographic location), outstanding security and reliability, and
access to flexible, low cost, and secure billing and charging
systems. The benefits of using the Internet are the uniform, well-
defined, and widely-used interfaces available anywhere, anytime.
Click-to-Dial-Back
With this service, a user requests (through an IP host) that the PSTN
call be established between another party and himself or herself. An
important pre-requisite for using this service is that the user has
simultaneous access to both the PSTN and Internet.
One example of an application of this service is on-line shopping: a
user browsing through an on-line catalogue, clicks a button thus
inviting a call from a sales representative. Note that (as is the
case with the all-PSTN Free-Phone, or "800", service) flexible
Lu, et. al. Informational [Page 4]
RFC 2458 Pre-PINT Implementations November 1998
billing arrangements can be implemented here on behalf of the service
provider. In addition (and also similarly to the Free-Phone/800), the
PSTN could route the call depending on the time of day, day of week,
availability of agents in different locations, and so on.
Click-to-Fax
With this service, a user at an IP host requests that a fax be sent
to a particular fax number. In particular this service is especially
meaningful when the fax is to be sent to someone who has only a fax
machine (but no access to the Internet). Consider, as an example, a
service scenario in which a Web user makes a reservation for a hotel
room in Beijing from a travel service page containing hotel
information of major cities around the world. Suppose a specific
Beijing hotel chosen by the user does not have Internet connection
but has a fax machine. The user fills out the hotel reservation form
and then clicks a button sending out the form to the travel service
provider, which in turn generates a fax request and sends it together
with the hotel reservation form to the PSTN. Upon receiving the
request and the associated data, the PSTN translates the data into
the proper facsimile format and delivers it to the Beijing hotel as
specified in the fax request.
Click-to-Fax-Back
With this service, a user at an IP host can request that a fax be
sent to him or her. (Consider the user of the previous example, who
now requests the confirmation from the Beijing Hotel. Another useful
application of the service is when size of the information that a
user intends to get is so large that downloading it to the user's PC
over the Internet will require a long time and a lot of disk space.)
Voice-Access-to-Content
With this service, a user at an IP host requests that certain
information on the Internet be accessed (and delivered) in an audio
form over the PSTN, using the telephone as an informational
appliance. One application of this service is to provide Web access
to the blind. (This may require special resources--available in the
PSTN--to convert the Web data into speech.)
4. Architectural Overview
4.1 Public Switched Telephone Network
From an application perspective, Internet nodes are interconnected
directly, as shown in Figure 1. When two machines are to communicate,
they will have the address of the destination end system, and will
Lu, et. al. Informational [Page 5]
RFC 2458 Pre-PINT Implementations November 1998
send network level datagrams, assuming that the underlying
infrastructure will deliver them as required.
_____
__ _____/ \_____
[__] / \
[----]-.-.-.-. Internet .-.
\_____ _______/ |
__ \__./ __ .
[__] / [__] |
[----]-. [----]-.
Key: .-.-. Internet Access Link
Figure 1
Where all nodes are on the same (broadcast) network, there is no need
for intervening routers; they can send and deliver packets to one
another directly. The Internet nodes are responsible for their own
communications requests, and act as peers in the communication
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -