PCT
`
`(51) International Patent Classification 6:
`H04Q 3100, H04L 29/06
`
`WORLD INTELLECTIJAL PROPERTY ORGANIZATION
`International Bureau
`IN_TERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`WO 97/31492
`
`(11) International Publication Number:
`
`Al
`
`(43) International Publication Date:
`
`28 August 1997 (28.08.97)
`
`(21) International Application Number:
`
`PCT/IB%/00134
`
`(22) International Filing Date:
`
`21 February 1996 (21.02.96)
`
`(81) Designated States: BR, CA, CN, JP, KR, US, European patent
`(AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC,
`NL, PT, SE).
`
`(71) Applicant (for all designated States except US):
`INTER(cid:173)
`NATIONAL BUSINESS MACHINES CORPORATION
`[US/US]; Old Orchard Road, Armonk, NY 10504 (US).
`
`Published
`With international search report.
`
`{72) Inventors; and
`{75) Inventors/Applicants (for US only): TRUONG, Hong, Linh
`[DEICH]; Reidholzstrasse 37, CH-8805 Richterswil (CH).
`WONG, Johnny, Wai-Nang [CA/CH]; Leimbachstrasse 119,
`CH-8041 Zurich (CH).
`
`(74) Agent: BARTH, Carl, Otto; International Business Machines
`Corporation, Saumerstrasse 4, CH-8803 RUschlikon (CH).
`
`(54) Title: DISTRIBUTED ARCHITECTURE FOR SERVICES IN A TELEPHONY SYSTEM
`
`2
`
`TPS
`
`WSA
`
`WSB
`
`(57) Abstract
`
`The invented method and system for enabling and controlling telephony over existing networks, e.g. A TM networks, the Internet or
`other data networks, uses essentially distributed control processing employing intelligence in the typical end-user devices, e.g. workstations
`or personal computers. Parallel use of a real-time channel (to provide the needed direct voice communication) and a control channel (for
`basic services like connection buildup and termination and for supplementary services) essentially established by and from the users's
`workstations (and in principle excluding the PBXs) allows implementation of practically any imaginable function.
`
`Bright House Networks - Ex. 1008, Page 847
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`

`

`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the Per on the front pages of pamphlets publishing international
`applications under the Per.
`
`AM
`AT
`AU
`BB
`BE
`BF
`BG
`BJ
`BR
`BY
`CA
`CF
`CG
`CH
`Cl
`CM
`CN
`cs
`cz
`DE
`DK
`EE
`ES
`Fl
`FR
`GA
`
`Armenia
`Austria
`Australia
`Barbados
`Belgimn
`Burkina Paso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`COte d'lvoire
`Cameroon
`China
`Czechoslovalcia
`Czech Republic
`Germany
`Denmark
`Estonia
`Spain
`Finland
`France
`Gabon
`
`GB
`GE
`GN
`GR
`HU
`IE
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`Ll
`LK
`LR
`LT
`LU
`LV
`MC
`MD
`MG
`ML
`MN
`MR
`
`United Kingdom
`Georgia
`Guinea
`Greece
`Hungary
`Ireland
`Italy
`Japan
`Kenya
`Kyrgystan
`Democratic People's Republic
`of Korea
`Republic of Korea
`Kazakhstan
`Liechtenstein
`Sri Lanka
`Liberia
`Lithuania
`Lllllembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`Mali
`Mongolia
`Mauritania
`
`MW
`MX
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`Sl
`SK
`SN
`sz
`TD
`TG
`TJ
`TT
`UA
`UG
`us
`uz
`VN
`
`Malawi
`Mexico
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romllllia
`Russian Federation
`Sudan
`Sweden
`Singapore
`Slovenia
`Slovakia
`Senegal
`Swaziland
`Chad
`Togo
`Tajikistan
`Trinidad and Tobago
`Ukraine
`Uganda
`United Stales of America
`Uzbekistan
`VietNam
`
`Bright House Networks - Ex. 1008, Page 848
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`

`

`wo 97131492
`
`PCTIIB96/00134
`
`-
`
`- 1 -
`
`DESCRIPTION
`
`Distributed Architecture for Services in a Telephony System
`
`5
`
`10
`
`FIELD OF THE INVENTION
`
`This invention relates to telephony. in particular to a method and apparatus
`
`for enabling telephony over existing networks like the Internet or other data
`
`networks. Essentially, distributed call processing
`
`is employed using
`
`intelligence in the typical end-user devices, e.g. workstations or personal
`
`15
`
`computers.
`
`BACKGROUND AND PRIOR ART
`
`20
`
`Computer-telephony integration is quickly developing a wide variety of
`
`applications that use well known, existing networks, e.g. the telephone
`
`networks, as well as new, often quickly expanding data networks, e.g. the
`
`Internet.
`
`25
`
`Telephony requires a real-time channel to provide the needed direct and
`
`immediate voice communication which makes it so attractive. Today, it also
`
`must provide certain supplementary services. Such supplementary services
`
`are traditionally implemented in the telephone switches, the so-called PBXs
`
`(for Private Branch Exchanges), through which the users are connected.
`
`30
`
`Some examples for such services are:
`
`Bright House Networks - Ex. 1008, Page 849
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`

`

`W097131492
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`PCTIIB96/00134
`
`-
`
`- 2 -
`
`Alternate Call - this supplementary service enables a user A to put a
`
`currently active calf to another user B on hold and place a call to, or
`
`activate a previously "on hold" call with, user C.
`
`Call Back - user A calls user B and finds that user B is busy; this
`
`5
`
`supplementary service enables user A to request a call back from user
`
`B.
`
`Camp on Call - user A calls user B and finds that user 8 is busy; this
`
`supplementary service enables the call to be placed again as soon as
`
`user B becomes free.
`
`10
`
`Deflect Call - this supplementary service enables a user to re-direct (or
`
`forward) an incoming call to another user or phone.
`
`Calt Transfer - this supplementary service enables user A to transform
`
`two of his calls {with users B and C) into a new call between users B
`
`and C.
`
`ts
`
`Directed Pickup Call - user A calls user B and the call is in the ringing
`
`state; this supplementary service enables a third user C to answer the
`
`call from a different destination.
`
`Multi-line Appearance
`
`-
`
`this supplementary service enables an
`
`incoming call to ring at two or more users; the first user who answers
`
`20
`
`gets the call.
`
`Call do not Disturb -
`
`this supplementary service enables a user to
`
`reject all incoming calls.
`
`As said above, these supplementary services are traditionally implemented
`
`25
`
`in the switches (or PBXs). Such PBXs are usually located at user's premises
`
`and connected to the public telephone network.
`
`With the advent of new and versatile networks like the Internet or ATM (for
`
`Asynchronous Transfer Mode) networks that allow the exchange and
`
`30
`
`transmission of digital data, including real time exchange of digitized voice
`
`which can be used for telephony, the traditional telephone systems are
`
`getting competition. However, when using such novel transmission tools,
`
`Bright House Networks - Ex. 1008, Page 850
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`

`

`W097/31492
`
`- 3-
`
`PCT/IB96/00134
`
`those supplementary services that were usually implemented in the PBXs
`
`are no more be available.
`
`Further, computer-network telephony requires more complex transmission
`
`5
`
`management since voice transmission is much more susceptible than data
`
`transmission to even minimal delays. Traditional call control in existing
`
`telephone networks is not adapted to provide this service for a data
`
`network.
`
`10
`
`Also, PBXs use a centralized approach to basic telephony services, i.e. call
`
`placement and termination, and to supplementary services. Due to the
`
`many functions that are performed, PBXs are generally complex and costly.
`
`They also treat the end-user equipment (e.g.
`
`the telephone sets} as simple
`
`devices that are specialized for telephony. With the wide availability of
`powerful workstations, it becomes attractive to use their capabilities for
`
`15
`
`providing at least pari of these telephony services and possibly integrate
`
`computers and telephony.
`
`Some approaches for integrating computers and phones are addressed by
`
`20
`
`James Burton in: "Standard Issue" in BYTE, September 1995, pp. 201-207.
`
`Burton describes several CTI
`
`(for Computer-Telephone
`
`Integration)
`
`architectures and their characteristic layout. The architectures listed by
`
`Burton, however, provide for a combined transmission of voice and control
`
`data over at
`
`least partially the same connections and are based on
`
`25
`
`connectivity to a telephone network or a PBX. The power of the end-user
`
`workstations is not exploited for basic or supplementary telephony services.
`
`US patent 4 634 812 by Hornburger et al discloses a method for transferring
`
`information including voice between computers in a decentralized telephone
`
`30
`
`control system. This system provides a data, also voice, transmitting
`
`multi-wire bus and two single wire control buses. A
`
`telephone system
`
`according to the Hornberger patent consists of identical PBXs, all being
`
`connected by two control buses and one data/voice multi-wire bus. Thus,
`
`Bright House Networks - Ex. 1008, Page 851
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`W097/31492
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`PCTIIB96/00134
`
`-
`
`- 4-
`
`this system provides a distributed control in a telephone system through
`
`multiple parallel channels and especially designed PBXs. It is a specially
`
`designed, so-to-speak self-contained, system for PBXs and does not address
`
`the idea of exploiting the power of end-user workstations for basic telephony
`
`5
`
`services and supplementary services.
`
`US patent 4 313 036 to Jabara et al describes a distributed computerized
`
`PBX, called CBX, system wherein the CBXs are connected by both a voice
`
`and a packet-switched network. Two links or channels are provided between
`
`10
`
`the CBXs: a signalling data link and a voice link. The data link is part of a
`
`virtual network which may be provided by a packet-switched network.
`
`However, this system concerns communication between PBXs for call
`
`control purposes and does not address
`
`the potential of end-user
`
`workstations for basic telephony services and supplementary services.
`
`15
`
`Various systems that use the Internet for telephony have been proposed.
`
`One such is advertised in the World Wide Web (WWW) under the Universal
`
`Resource Locator (URL) http:l/www.vocaltec.com. An overview of some
`
`other such systems with more references can be found under the URL
`
`20
`
`http://www.northcoast.comrsavetz/voice-faq.html. The systems described
`
`there exploit the power of the users' workstations for limited basic telephony
`
`services, but do neither address nor provide means for supplementary
`
`services.
`
`25
`
`Thus, it is an object of this invention to provide, for a telephone system, a
`
`distributed, i.e. workstation-oriented, architecture with more than one link
`
`between
`
`the workstations and a method for providing not only basic
`
`telephony services, such as call placement and termination, but also
`
`complex supplementary service functions.
`
`30
`
`Another object is to provide a telephone system with a distributed, i.e. not
`
`switch-centered, architecture that uses an existing network, preferably a
`
`Bright House Networks - Ex. 1008, Page 852
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`

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`W097/31492
`
`PCTIIB96/00134
`
`- 5 -
`
`packet-switched network, to implement desired basic and/or supplementary
`
`services.
`
`The invention provides a solution to the need of using existing network
`
`5
`
`infrastructure
`
`for
`
`telephony,
`
`in particular
`
`for complex supplementary
`
`services. By employing a workstation-oriented architecture, the invention
`
`provides an effective and versatile tool for implementing any desired
`
`supplementary services, that can be altered and adapted at any time with
`
`minimal effort and practically without disturbing an existing network
`
`10
`
`architecture and/or protocols used.
`
`SUMMARY OF THE INVENTION
`
`15
`
`In brief, the distributed, workstation-oriented architecture for basic and
`
`supplementary
`
`telephony services according
`
`to
`
`the
`
`invention, which
`
`services were traditionally imp~emented in the switches (PBXs), comprises
`
`setting up a first communication channel for transmitting first signals and
`
`setting up a second communication channel for second signals, whereby
`
`20
`
`both channels directly connect the end-user devices, e.g workstations.
`
`Preferably, the first signals are control signals and the second signals voice
`
`signals. The two (or more) connections or channels can be established
`
`directly and independently, the second or voice channel being preferably
`
`set up subsequent to the first or control channeL The control channel, once
`
`25
`
`established, is preferably maintained permanently during a communication
`
`session. A session in this context may include interruptions or pauses in the
`
`voice connection as
`
`long as an
`
`intent
`
`to continue
`
`the
`
`telephone
`
`communication is recognizable.
`
`30 With
`
`the invention,
`
`telephony services can be
`
`implemented solely
`
`in
`
`workstations; the use of a server for a limited number of functions, e.g.
`
`address
`
`resolution or authentication, may however be
`
`required or
`
`advantageous. The switches, PBXs, if used at all, only need to provide the
`
`Bright House Networks - Ex. 1008, Page 853
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`wo 97/31492
`
`PCT/IB96/00134 -
`
`- 6 -
`
`communi_cation channels for voice and/or real-time data transport. They are
`
`not involved in the implementation of the services.
`
`Details of the invention may be extracted from the following general and
`
`5
`
`detailed description of preferred implementations.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`15
`
`20
`
`Fig. 1
`
`is an overview of one possible configuration using
`
`the
`
`invention;
`
`Fig. 2
`
`depicts the general function of the invention;
`
`Fig. 3
`
`exemplifies
`
`the call placement process executed by
`
`the
`
`invention;
`
`Fig. 4
`
`exemplifies the call back process executed by the invention;
`
`Fig. 5
`
`exemplifies the call transfer process executed by the invention;
`
`Fig. 6
`
`references one architecture of an implementation, and
`
`25
`
`Fig. 7
`
`references another architecture according to the invention.
`
`30
`
`Bright House Networks - Ex. 1008, Page 854
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`W097/31492
`
`PCTIIB96/00134
`
`- 7 -
`
`DESCRIPTION OF THE PREFERRED EMBODIMENTS
`
`A. General Description
`
`5
`
`A.l. Overview
`
`Fig.1 shows an example for a general configuration in which the invention
`
`can be applied. A network 1, which may be an ATM network or an IP
`
`(Internet Protocol) network as examples
`
`for existing digital networks
`
`10
`
`conventionally used for data transfer, links workstations (WS) 3a to 3d. Also
`
`connected to network 1 is a telephony server (TPS) 2. Further, to enable
`
`communication with a PBX 4, a first gateway (GW) 5 is also attached to
`
`network 1. A second gateway 7
`
`links network 1 to an ISDN (Integrated
`
`Service Digital Network) 6. Each of PBX 4 and ISDN 6 have connected to it
`
`15
`
`usual
`
`telephones 8 and 9 and/or appropriate workstations that allow
`
`telephony.
`
`The gateways shown in Fig.1, which are not part of this invention, usually
`
`support interworking with an ISDN and/or with an existing PBX. respectively.
`
`20
`
`Technically, a gateway is able provide signalling interworking (mapping of
`
`ISDN/PBX signalling and
`
`signalling
`
`used
`
`in
`
`a
`
`distributed,
`
`i.e.
`
`workstation-oriented, architecture), voice signal translation (between voice
`
`encoding scheme used in ISDN/PBX and that used
`
`in
`
`the distributed
`
`architecture), and/or proxy functions for ISDN/PBX users.
`
`25
`
`30
`
`The dotted lines in Fig.1 shall illustrate the telephone calls between the
`users 3a to 3d, 8, and 9: the solid lines shall indicate the attachments to the
`
`network. This will be apparent in more detail from the following description
`
`of Fig.2.
`
`Fig.2 shows an overview of the basic configuration and the essential data
`
`flow according
`
`to
`
`the
`
`invention. The
`
`invention uses a distributed.
`
`Bright House Networks - Ex. 1008, Page 855
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`W097131492
`
`PCTIIB96/00134
`
`- 8 -
`
`workstation-oriented architecture which will be apparent from the detailed
`
`description of embodiments of the invention below.
`
`One key element of the novel architecture is the use of two separate
`
`s
`
`end-to-end channels between the workstations for each phone call. As
`
`shown in Fig.2, a workstation-workstation control channel 12 is provided for
`
`call control and a voice channel 13 for voice communication. Workstations
`
`A and 8 exchange control messages over control channel 12. These
`
`messages could contain name or phone number of the calling and called
`
`10
`
`users, qualify service parameters (e.g. voice encoding schemes supported
`
`by the workstation or preferred by the user). status information regarding
`
`the call (e.g. whether call is active or on hold). and specific requests by
`
`users (e.g. put user on call-back list). All messages transported on control
`
`channel 12 are handled by processes at the workstations; they are not
`
`15
`
`interpreted by the switches or routers (Figs.3 and 4) which provide the
`
`means for these channels.
`
`Another key element of the
`
`invention
`
`is
`
`that control channel 12
`
`is
`
`maintained for the duration of the call, whereas voice channel 13 need not
`
`20
`
`be sustained permanently, but is set up only when needed. For example,
`
`voice channel 13 can be released when a call
`
`is put on hold, and
`
`re-established when the call is activated again. The ability to exchange any
`
`control signals or messages over the maintained workstation-workstation
`control channel 12 allows
`the
`implementation of a wide variety of
`
`25
`
`supplementary telephony services without involvement of the switches or
`
`routers.
`
`Telephony server 2 may pertorm functions such as name/phone number
`
`registration, address resolution, and authentication. Workstations request
`
`30
`
`service from server 2 over separate workstation-server control channels 10
`
`and 11. These control channels are set up on a as-needed basis. So much
`
`for the general layout.
`
`Bright House Networks - Ex. 1008, Page 856
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`wo 97/31492
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`- 9-
`
`PCTIIB96/00134
`
`Since any of the channels mentioned, control channels 10, 11, or 12, as well
`
`as voice channel 13, respectively, can be provided by existing networks, e.g.
`
`ATM or IP networks, the invention allows the implementation of basic
`
`telephony services
`
`(i.e. call placement and
`
`termination} as well as
`
`5
`
`supplementary telephony services on practically any of the existing and
`
`evolving data networks.
`
`The
`
`following
`
`is a more general description of a set of
`
`functions
`
`implemented according to the invention; for someone skilled in the art, it is
`
`10
`
`already sufficient for carrying out the invention. Still, a subset of these
`
`functions will be addressed in much more detail further down.
`
`15
`
`20
`
`25
`
`A.ll. Basic Telephony Services
`
`1. Place and Receive a Call
`
`The steps for this process are depicted in Fig.3. User A wishes to place a
`
`call to user B; each is at one of the workstations 3a to 3d shown in Fig.1.
`
`Step 1: User A's workstation (WS A) maps user B's name or phone number
`
`address onto the network address of user B's workstation (WS B). This
`
`"address mapping" function may be provided by an appropriate server
`
`process running at telephony server 2.
`
`Step 2: Workstation A sets up a control channel (12 in Fig.2) to workstation
`
`B.
`
`Step 3: Workstation A sends a "call request" message to workstation 8 over
`the control channel.
`
`30
`
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`wo 97/31492
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`PCTIIB96/00134
`
`- 10-
`
`Step 4: Workstation 8 returns a "call confirm" message to workstation A,
`
`informing workstation A that workstation 8
`placement
`
`is able to proceed with calf
`
`5
`
`Step 5: Workstation 8 indicates to user 8 that there is an incoming call.
`
`Step 6: User 8 responds that he is answering the call.
`
`Step 7: Workstation 8 sends a "connect" message to workstation A over the
`
`1o
`
`control channel, informing workstation A that user 8 is answering the call,
`
`and asking workstation A to set up a voice channel.
`
`Step 8: Workstation A sets up a voice channel to workstation B.
`
`15
`
`Step 9: Workstation 8 indicates to user 8 that the call is now active.
`
`Step 10: Workstation A indicates to user A that the call is now active.
`
`Step 11: User A and user 8 talk over the voice channel.
`
`20
`
`2. Call Termination
`
`At any time, user A or user 8 may request call termination. Suppose call
`
`25
`
`termination is initiated by user A. The steps are as follows:
`
`Step 1: Workstation A sends a "terminate call" message to workstation 8
`
`over the control channel, and releases the voice channel of the call.
`
`30
`
`Step 2: Workstation B returns a "terminate calf" message to workstation A,
`
`and release voice channel also.
`
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`wo 97/31492
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`- 11 -
`
`PCT!IB96/00134
`
`Step 3: Workstation A completes call
`
`termination by
`
`releasing
`
`the
`
`workstation-workstation control channel of the call.
`
`5
`
`A.llf. Supplementary Services
`
`1. Alternate Call
`
`At some point in time, user A may have two or more calls in progress. One
`
`10
`
`of these calls (to user B) is active while the others are on hold. Suppose
`
`user A wishes to put the call to user 8 on hold and activate the call to user
`
`C. The steps are as follows:
`
`Step 1: Workstation A sends a "hold" message to workstation B over the
`
`15
`
`control channel with workstation 8, informing workstation 8 that the call is
`
`now on hold.
`
`Step 2: Workstation A sends an "active" message to workstation C over the
`control channel with workstation C. informing workstation C that the call is
`
`20
`
`now active.
`
`2. Call Back
`
`25
`
`During call placement, workstation A finds that user 8 is busy at the initial
`
`message exchange over the control channel. User A then requests a call
`
`back. The steps are illustrated in Fig.4.
`
`Steps 1 to 3: Same as those for placing a call (see above: Place and Receive
`
`30
`
`a Call, described in connection with Fig.3).
`
`Step 4: Workstation 8 responds with a "user busy" message, informing
`
`workstation A that user B is busy, but call back is possible.
`
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`W097/31492
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`PCTIIB96/00134
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`- 12 -
`
`Step 5: User A requests that he be put on user B's call back Jist.
`
`Step 6: Workstation A sends a "call back request" message to workstation 8
`
`over the control channel. This message contains user A's phone number.
`
`Step 7: Workstation 8 enters user A's phone number onto user B's call-back
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`record.
`
`When user 8 subsequently checks the call-back record, he/she will learn
`
`that user A has requested a call back.
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`3. Camp on Call
`
`This is similar to the above Call Back process, except that an attempt will be
`
`made to call user 8 again as soon as B becomes free.
`
`Steps 1 to 3: Same as those for Place and Receive a Call.
`
`Step 4: Workstation 8
`
`responds with a "user busy" message, informing
`
`workstation A that user B is busy, but camp on busy is possible.
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`Step 5: User A requests camp on call.
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`5
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`10
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`15
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`20
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`25
`
`Step 6: Workstation A sends a "camp on call" message to workstation 8
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`over the control channel.
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`Step 7: Workstation B
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`returns a
`
`"camp on confirmed" message
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`to
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`30
`
`workstation A.
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`Step 8: When user 8 becomes free and indicates that he is answering the
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`camp on call, workstation 8 resumes the call placement with workstation A,
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`at step 7 of Fig.3.
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`5
`
`4. Deflect Call
`
`User 8 may wish to forward an incoming call to another phone number
`(phone number M) immediately, or if he/she is busy, or if the call is not
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`10
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`answered after a time-out interval. Suppose user A is placing a call to user
`
`B, the steps for the case of deflect after time-out are:
`
`Steps 1 to 5: Same as those for Place an Receive a Call.
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`15
`
`Step 6: User 8 has not answered after a time-out.
`
`Step 7: Workstation B sends a "deflect call" message to workstation A over
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`the control channel. This message contains the phone number to which the
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`call is to be forwarded (phone number M).
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`Step 8: Workstation 8 releases the control channel to workstation A.
`
`Step 9: Workstation A places a call to phone number M.
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`20
`
`25
`
`5. Call Transfer
`
`Suppose user A has two calls in progress: a call with user B which is on
`
`hold and a call with user C which is active. User A requests to have user B
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`JO
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`and user C connected, and his/her calls to these users terminated. This
`
`process is shown in Fig.5. The steps are:
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`Step 1: Workstation A sends a "hold" message to workstation C over the
`
`control channel with workstation C.
`
`Step 2: Workstation A sends a "receive transfer call" message to workstation
`
`s
`
`C over the control channel with workstation C, requesting workstation C to
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`accept a transfer call from workstation 8.
`
`Step 3: Workstation C returns a "transfer confirm" message to workstation A,
`and waits for a transfer call from workstation 8.
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`10
`
`Step 4: Workstation A sends a "place transfer call" message to workstation
`
`8 over the control channel with workstation 8, requesting workstation 8 to
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`place a transfer call to workstation C.
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`15
`
`Step 5: Workstation C returns a "transfer confirm" message to workstation A.
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`20
`
`25
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`30
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`Step 6: Workstation 8 places a transfer call to workstation C.
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`Step 7: Workstation A initiates termination of his/her call to workstation B.
`
`Step 8: Workstation A initiates termination of his/her call to workstation C.
`
`6. Directed Pickup Call
`
`Suppose user A calfs user 8 and the call is in the ringing state. A third
`
`user C wishes to answer the calf. The steps are as follows_
`
`Step 1: Workstation C sets up a control channel to workstation B.
`
`Step 2: Workstation C sends a "pickup query" message to workstation 8 to
`
`find out whether call pick-up is possible or not. User C's phone number is
`
`included in this message.
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`Step 3: Workstation 8 returns a "pickup allowed" message to workstation C.
`
`Step 4: Workstation C sends a "pickup request" message to workstation 8,
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`5
`
`requesting call pickup.
`
`Step 5: Workstation 8 sends a "directed pickup" message to workstation A
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`which contains user C's phone number, instructing workstation A to place a
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`10
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`15
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`call to user C.
`
`7. Multi-line Appearance
`
`Suppose user A places a call to a phone number that has multi-line
`
`appearance. Workstation A maps the destination phone number onto a list
`
`of network addresses. This "address mapping" function is provided by a
`
`server process running at the telephony server. Workstation A then places
`
`separate calls to each of these addresses. Workstation A will proceed with
`
`the first destination that answers, and terminates the call placement to the
`
`20
`
`other addresses.
`
`8. Call do not Disturb
`
`Suppose user 8 has requested call do not disturb. Any workstation A
`
`attempting to place a call to user 8 will get a "do not disturb" message over
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`the control channel in return.
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`25
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`30
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`B. Detailed Description of Specific Functions
`
`8.1. Reference Architecture
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`5
`
`Figs.6 and 7 show the reference architecture of a communication system
`
`employing
`
`the
`
`invention. The basic
`
`telephony services
`
`(mainly call
`
`establishment, call termination) and supplementary services (e.g. call hold,
`
`call back, call transfer, call deflection) are implemented by an enabling layer
`
`at the workstation. Integrated are functions such as address resolution,
`
`10
`
`voice encoding, and authentication.
`
`Until now, a user was identified by a name or a phone number. In the
`
`following, users will be identified by their respective e-mail address.
`
`15
`
`Fig.6 depicts an architecture according
`
`to
`
`the
`
`invention
`
`in an ATM
`
`(Asynchronous Transfer Mode) environment. Physical layer 18 and ATM
`
`layer 17 are standard design features. TCP (Transmission Control Protocol)
`
`connection is set up over IP, i.e. Internet Protocol 15, which runs on top of
`AAL5, i.e. ATM Adaptation Layer 16. The implementation of IP on an ATM
`network is available off-the-shelf.
`
`20
`
`Voice communication requires QoS (Quality of Service) guarantee from
`
`transport services interface 14, e.g. acceptable end-to-end delay and delay
`
`jitter. The voice channel
`
`is established by a VCC
`
`(Virtual Channel
`
`25
`
`Connection) with QoS. Encoded voice samples are sent in ATM cells. Q.2931
`
`and SAAL (Signalling ATM Adaptation Layer) are signalling protocols for
`vee setup and release. Transport services interface 14 provides transport
`for voice and control channels.
`
`30
`
`Enabling layer 19 uses the services provided by transport services interface
`
`14 for establishing control channels and voice channels. Specifically, both
`
`workstation-server and workstation-workstation control channel are realized
`
`by TCP connections as indicated by block 15. Enabling layer 19 supports an
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`API
`
`(Application Programming
`
`Interface) which can be used
`
`for the
`
`development of telephony applications.
`
`Fig.7 depicts an architecture according to the invention in an IP (Internet
`
`5
`
`Protocol) environment. The physical layer is an IP subnet technology 26 able
`
`to provide the required services. QoS for the voice channel can be provided
`
`by a pair of RSVP (Resource Reservation Protocol) flows because an RSVP
`
`flow is uni-directional. Encoded voice samples are sent in UDP (User
`
`Datagram Protocol) packets using TCP/UDP protocol 24 and transport
`services interface 23. In this case, RSVP is the signalling protocol used
`
`10
`
`between the workstations and the routers to establish the needed RSVP
`
`flows.
`
`In such an IP subset, encoded voice packets can also be sent in UDP
`
`15
`
`packets without RSVP. This is a best-effort service and no QoS guarantee is
`
`provided. Transport services interface 23 provides transport capacity for
`
`voice and control channels. Enabling layer 22 supports an API 21 which can
`
`be used for developing telephony applications.
`
`20
`
`So much for the functionality of the invention. Some selected functions will
`
`be described further below in extensive detail to clarify the invention.
`
`The abbreviations already introduced above, e.g. WS for workstation, WS A
`
`for workstation of user A as shown in the drawings, will be exclusively used.
`
`25
`
`Control messages exchanged over WS-server and WS-WS control channels
`
`are used to implement the basic and supplementary services. These control
`
`channels are realized by TCP connections.
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`30
`
`Each control message contains a code which indicates the name of the
`
`control message and optionally a list of parameters (this list may be empty).
`
`For convenience, a control message is denoted by:
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`message-name (parameter fist)
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`This notation will be used
`
`in
`
`the description of how the basic and
`
`supplementary services are implemented. In addition, only the parameters
`
`s
`
`relevant to the procedure being described are listed, in order not to include
`
`unnecessary details.
`
`Several timers are used in the implementation descriptions. These timers
`
`operate as follows. A timer is stopped when an expected event occurs
`
`10
`
`before it expires. If, for whatever reason, the timer expires, some recovery
`
`action will be taken. In the implementation descriptions, unless otherwise
`
`specified, the recovery action is to terminate the phone call, using the
`
`procedure described in Section 8.11.2. below.
`
`8.11. Basic Telephony Services
`
`Basic telephony services include call placement and call termination.
`
`15
`
`20
`
`1. Call Placement
`
`Suppose user A at workstation A (WS A) wishes to place a call to user B at
`
`workstation B (WS B) and user B is free to accept the call. The basic steps
`
`25
`
`are depicted in Fig .3, there using the generic terms of Section A.ll. Details
`
`of the implementation at WS A and WS 8 are described below.
`
`Step 1: WS A maps user B's e-mail address onto WS B's TCP address.
`
`JO WS A procedure:
`
`Upon receiving a request for call placement from user A, WS A sets up a
`
`TCP connection to the telephony server. This connection will be used as the
`
`WS-server control channel. The setting up of a TCP connection
`
`is a
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`well-known procedure. WS A then prepares a AdrQuery (user B's e-mail
`
`address) control message and sends this message to the telephony server.
`
`The telephony server, upon receiving the AdrQuery control message, checks
`
`5
`
`its address mapping database. If an entry for user B's e-mail address is
`
`found, the telephony server prepares an AdrRsp (WS B's TCP address)
`
`control message, and returns this message to WS A; otherwise, an AdrRsp
`
`(user B not registered) is prepared and returned. In both cases, the TCP
`
`connection between WS A and