(12) United States Patent
`Malik
`
`USOO64.96504B1
`US 6,496,504 B1
`(10) Patent No.:
`*Dec. 17, 2002
`(45) Date of Patent:
`
`(54) SMART ALLOCATION OF BANDWIDTH
`FOR MULTIPLE INDEPENDENT CALLS ON
`A DIGITAL NETWORK
`
`(75) Inventor: Naeem Iqbal Malik, Fremont, CA (US)
`(73) Assignee: Ricoh Company, Ltd., Tokyo (JP)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`This patent is Subject to a terminal dis
`claimer.
`
`(21) Appl. No.: 09/129,892
`(22) Filed:
`Aug. 6, 1998
`(51) Int. Cl. ............................ H04L 12/28; H04J 3/16;
`HO4J 3/12
`(52) U.S. Cl. ........................ 370/390; 370/468; 370/524
`(58) Field of Search ................................. 358/434, 400,
`358/405; 709/238,250, 227, 226; 370/392,
`390, 431, 410, 468, 524, 264, 432, 385,
`395.1, 395.2, 381, 384
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`370/524
`10: R. et al
`:S A :
`5.44s. 559 A - 9/1995 E. - - - - - - - - - - - - - 370/468
`
`5.533.10s. A
`7/1996 E. et al... 379,201.03
`5,577,035 A * 11/1996 Hayter et al. ............ 370,395.4
`5,675,576 A * 10/1997 Kalampoukas et al. ..... 370/390
`5,790,641. A
`8/1998 Chan et al. ................. 358/434
`
`5,802,049 A * 9/1998 Watanabe ................... 370/390
`5,832,240 A 11/1998 Larsen et al. ............... 710/105
`5,963,552 A * 10/1999 Joo et al. .....
`... 370/395.32
`6,081,841. A
`6/2000 Malik ......................... 370/524
`6,097.720 A * 8/2000 Araujo et al. ............... 370/390
`6,144,661. A 11/2000 Katsube et al. ............. 370/390
`6,304,579 B1 * 10/2001 Malik ......................... 370/390
`FOREIGN PATENT DOCUMENTS
`
`9/1996
`
`WO 96/27975
`WO
`* cited by examiner
`Primary Examiner-Chau Nguyen
`ASSistant Examiner Andrew Lee
`(74) Attorney, Agent, or Firm-Oblon, Spivak, McClelland,
`Maier & Neustadt, P.C.
`(57)
`ABSTRACT
`A method and apparatus in a computer network System form
`a Setup message at a Source terminal. The Setup message
`includes a bandwidth coordination message that identifies
`respective Subchannel data rates to be used when Sending
`data to respective destination terminals. The Setup message
`identifies respective data rates and associated destination
`terminals, and the Setup message is Sent to a Switch facility,
`that interconnects the Source terminal and the respective
`destination terminals. The Switch extracts the bandwidth
`coordination message and establishes Subchannel links, Such
`as Subchannels of one or two ISDN B channels. Once the
`respective links are established, the source terminal trans
`mits a message via the Switch to the respective destination
`terminals at the data rates corresponding with the Subchan
`nel data rates established by the Switch facility, and as
`requested by the Source terminal.
`
`13 Claims, 13 Drawing Sheets
`
`100
`
`Source Terminal
`Multi-Addressing
`Mechanism
`BW Allocation
`Mechanism
`5102
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`106
`Mechanism
`Channel and Bandwidth
`Coordination Mechanism 5106
`24
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`220
`
`GUEST TEK EXHIBIT 1010
`Guest Tek v. Nomadix, IPR2019-00211
`
`

`

`U.S. Patent
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`Dec. 17, 2002
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`Dec. 17, 2002
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`U.S. Patent
`
`Dec. 17, 2002
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`Sheet 9 of 13
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`US 6,496,504 B1
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`Dec. 17, 2002
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`Dec. 17, 2002
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`US 6,496,504 B1
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`U.S. Patent
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`Dec. 17, 2002
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`Sheet 13 of 13
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`US 6,496,504 B1
`
`SEND TO SOURCE
`TERMINAL A CALL
`PROCEEDING MESSAGE
`
`RECEIVE AND STORE SETUP
`MESSAGE IN MEMORY
`
`S21
`
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`IDENTIFY
`BANDWIDTH COORDIN
`ATION MESSAGE
`
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`IDENTIFY BANDWIDTHS
`AND ASSOCIATED NUMBERS
`
`ESTABLISH LINKS FOR
`AVAILABLE ADDRESSEES &
`REQUESTED BANDWIDTHS
`
`ESTABLISH CONNECTION
`BETWEEN SOURCE AND
`DESTINATION TERMINALS
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`OF RESULTS
`
`A / C. 7.3
`
`

`

`1
`SMART ALLOCATION OF BANDWIDTH
`FOR MULTIPLE INDEPENDENT CALLS ON
`A DIGITAL NETWORK
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`This application contains Subject matter related to that
`disclosed in application Ser. No. 08/841,655 filed on Apr. 30,
`1997, now U.S. Pat. No. 6,104,505 entitled “A method and
`Apparatus For Routing Data Information Conveyed In A
`Facsimile Message”; application Ser. No. 08/955,353 filed
`on Oct. 21, 1997 now U.S. Pat. No. 5,938,735 entitled
`“Method And Apparatus For Establishing Optimized ISDN
`Communication Conditions'; application Ser. No. 09/021,
`566, filed Feb. 10, 1998, now U.S. Pat. No. 6,081,841
`“entitled Method and Apparatus for Expanding Data Rate In
`An ISDN Communication System”, commonly owned
`application Ser. No. 09/110,078, filed Jul. 2, 1998, now U.S.
`Pat. No. 6,304,579 entitled “Method and Apparatus for
`Sending a 1xN Communication Message”, each of which
`having common inventorship, and the contents of all of
`which being incorporated herein by reference.
`
`15
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention pertains to communication Systems
`and methods for communicating information over digital
`networks, Such as an Integrated Services Digital Network
`(ISDN). In particular, the present invention pertains to
`establishing over an ISDND channel one or more data rate
`Selectable communication links between a Source terminal
`and one or more destination terminals via a modified ISDN
`Switch. The modified ISDN Switch handles the aggregate
`bandwidth of two ISDN B channels as a common resource
`that is available for Subdivision and allocation to one or
`more links to the one or more destination terminals. The
`aggregation of the two ISDN B channels, as well as the
`subdivision of the bandwidth afforded thereby, is performed
`without requiring the Source and destination terminals to
`perform bonding or multilink protocol processes.
`2. Discussion of the Background
`Conventional facsimile devices communicate over the
`Public Switch Telephone Network (PSTN) using analog
`Signals that are transmitted over conventional telephone
`lines. The Source terminal (e.g., a facsimile device, computer
`with Scanner and modem facilities, or another device that
`transmits and/or receives data) converts digital Scanned
`information into a corresponding analog signal So the same
`may be sent over the PSTN telephone line, via a telephone
`Switch facility, to the destination terminal. The Source ter
`minal receives the analog information and converts the
`analog information back into digital Signals which form the
`basis of an image to be printed, perhaps on facsimile paper.
`The Integrated Services Digital Network (ISDN) is
`emerging as a next generation worldwide public telecom
`munications network that will replace portions of the exist
`ing PSTN and provide a variety of services not offered by
`the PSTN. ISDN will allow for the transmission of various
`types of data between various types of ISDN terminal
`equipment (TE).
`A portion of the ISDN link between a source terminal and
`a central office, which has a Switch facility, is referred to as
`a “digital pipe'. A capacity of the digital pipe is generally
`discussed in terms of Separate channels. In particular, a
`“basic access' digital pipe includes two B channels (basic
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
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`
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`US 6,496,504 B1
`
`2
`channels) that each Support 64 kbps signaling, and a D
`channel at 16 kbps. While the total bit rate of these three
`channels is 144 kbps, framing, Synchronization and other
`overhead bits bring the total bit rate of a basic acceSS link to
`192 kbps. Furthermore, the B channels serve as separate
`communication channels. Such that the maximum data
`capacity, as view by the user, is 64 kbps per B channel, and
`16 kbps for the D channel, not 192 kbps.
`Conventional facsimile devices, Such as G3 devices, Send
`Signals at rates not exceeding 64 kbps, because only one of
`the two B channels is used. Because facsimile data is
`arranged in a predetermined format, Sending data over two
`Separate B channels would be a Sizable task because con
`ventional ISDN switches handle the B channels separately,
`and thus may send data of one of the B channels over a
`completely different route than that of the other B channel.
`AS a consequence, the different communication paths
`impose different communication delays on the respective B
`channels.
`Other devices Such as Video teleconference facilities,
`assume the processing burden of “bonding', or employing
`multilink point-to-point (multilink PPP) protocols, so as to
`increase data rates approaching 128 kbps. The bonding
`approach imposes a burden on the customer premise equip
`ment (CPE) of dialing the ISDN switch and establishing the
`Subsequent calls needed to achieve the desired data rate.
`Thus, two Separate links are established. In particular, by
`assuming the burden of maintaining two separate commu
`nication connections with the ISDN Switch, the CPE can
`give the appearance to a user that a 128 kbps channel is
`available to the user. However, the bonding approach is
`cumbersome in that the ISDN Switch assumes each of the B
`channels may be handled independently, and therefore
`impart different delays into the Separate B channels. AS a
`consequence, the CPE must compensate for the delayS
`between the respective B channels, and piece together the
`received and transmitted information So as to avoid Syn
`chronization problems.
`Multilink PPP schemes attack the same problem from a
`different approach, although also placing a similar proceSS
`ing and data management burden on the CPE. The multilink
`PPP schemes use a conventional ISDN switch and attempts
`to make the ISDN switch oblivious to the operation of
`combining B channels to provide an effective data rate
`approaching 128 kbps. The multilink protocol involves
`dividing the user's Source data into Specific fragments,
`including overhead information in the respective packets, So
`that the packets may be sent over all available channels, and
`later recombined in a contiguous fashion. AS with bonding,
`multilink PPP places a computational and management
`burden on the CPE, rather than at the ISDN Switch.
`AS recognized by the present inventor, a limitation with
`conventional ISDN networks and the Source and destination
`terminals that operate therewith, is that the B channels are
`identified as Static, fixed-bandwidth channels that may not
`be fully utilized by either the source or destination terminals.
`Moreover, while each B channel is allocated 64 kbps, a
`Source or destination terminal may or may not be able to
`Support the data rate, and thus may use the channel at lower
`data rates. However, the capacity for the channel remains at
`64 kbps, and thus unless the Source and destination terminals
`actually use a full 64 kbps. Signaling Scheme, a portion of the
`available bandwidth (related to signaling speed) is wasted.
`In light of this limitation, the present inventor identified
`that the “subchannelization' of one or more ISDN B chan
`nels is not performed with conventional Systems, but would
`
`

`

`US 6,496,504 B1
`
`15
`
`3
`be beneficial if the Subchannelization allowed the “wasted”
`portion of the bandwidth to be used for other communication
`tasks. Moreover, if a modified ISDN Switch were available
`that could receive a message, or messages, from the Source
`terminal, and route the message, or messages, as Subchannel
`messages to one or more destination terminals at a user
`Selectable Subchannel bandwidth (i.e., data rate), signifi
`cantly greater flexibility in terms of end-user communication
`Speed, accessibility, and user-friendly operation could be
`achieved.
`Conventionally, the function served by the ISDN D
`channel, is twofold. First, the D channel is used to establish
`and maintain signaling between the CPE and the ISDN
`Switch (operated by the telephone company). Thus, the D
`channel carries signaling information Such as that required
`for dialing the telephone number of the destination terminal
`and making the connection between the Source terminal and
`the destination terminal. A more complete description of the
`D channel as employed in narrowband and broadband
`ISDN, as well as ISDN terminal equipment, protocols, data
`rates, etc. is provided in the literature, for example in
`Stallings, W., “Data and Computer Communications”, 5"
`Edition, Prentice Hall, 1997, pages 740–769 (hereinafter
`“Stallings”), the contents of this book being incorporated
`herein by reference.
`FIG. 1 is a block diagram of a conventional ISDN system
`100 having a source facsimile 10 at a source facility 1 that
`communicates via an ISDN Switch 22 to a destination
`facsimile 16 (or other type of destination terminal, Such as
`a computer, ISDN equipped photocopier, etc.) in a destina
`tion facility 2. The source facsimile 10 communicates via a
`terminal adapter 10A, shown as an internal device, although
`a separate external terminal adapter may be used as well.
`The terminal adapter 10A provides a protocol (physical layer
`and intermediate layer) conversion function for converting
`signal protocols such as V.35, RS-232, Universal Serial Bus
`(USB), IEEE 1394 (FireWire), etc. to an ISDN compliant
`protocol over a 4-wire interface. In the Source facility 1, the
`bonding or multilink PPP mechanism may be incorporated
`in the source terminal 10, terminal adapter 10A or in the NT1
`14.
`The NT1 14 connects the Source facilities 1, via a two
`wire line 15, to a Switching module 26 located at the ISDN
`Switch 22. Alternatively, a Second network termination
`(NT2) may be used at the source facility 1 between NT1 and
`the terminal adapter to provide a Switching and concentra
`tion function, Such as with a digital private branch exchange
`(PBX). Likewise, the NT1 may be replaced with a NT12 that
`performs the functions of both the NT1 and NT2.
`At the ISDN Switch 22, the Switching module 26 connects
`to a processor 24 and another Switching module 28 via a bus
`27, which allows digital commands and data to be passed
`between the respective switching modules 26 and 28, and
`the processor 24.
`The equipment at the destination facility 2 may or may not
`be exactly similar to that of the source facilities 1. In the
`system shown in FIG. 1, the destination facility 2 includes
`the destination facsimile 16 having a terminal adapter 16A
`incorporated therein, which connects to another NT1 20 as
`60
`shown. The NT1 20 connects to the Switching module 28 in
`the ISDN Switch 22, via another two-wire line 17 as shown.
`Several Subaddresses 16S1-16SN may connect to the des
`tination facsimile 16 by way of Separate dedicated lines
`18S1 to 18SN.
`ISDN communications is based on a seven layer protocol
`Stack, as explained in reference to FIG. A.5 of Stallings, for
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`example. Control Signaling is accomplished between the
`respective user-network interface and occurs at a third layer
`of the protocol Stack (i.e., the "network layer) and is named
`I.451/Q.931. Thus, establishing and maintaining control
`Signaling for a communication link is established between
`the source facility 1 and a destination ISDN facility 2
`through the D channel, and in particular, the ISDN network
`layer, data link layer and physical layer.
`FIG. 2 is a frame structure 200 of a transmission from the
`Source facilities 1 to the ISDN Switch 22, for an ISDN basic
`rate access. The frame structure 200 includes 48 bits which
`are transmitted in 250 usec. Components of the frame
`structure 200 include framing bits, F, dc balancing bits, L, B
`channel bits for the first B channel (16 per frame), B1, B
`channel bits for the second B channel (16 bits per frame),
`B2, D channel bits (4 per frame), D, auxiliary framing bit,
`Fa. A more detailed description of the frame Structure, as
`well as a corresponding frame Structure for the frames Sent
`from the ISDN Switch 22 to the Source facilities 1, is
`described in Stallings, pp. 212-215.
`A link access protocol (LAPD) D channel is defined for
`establishing particular LAPD frames that are exchanged
`between the Subscriber equipment (either at the Source
`facility 1 or at the destination facility 2) and the ISDN switch
`22. The call control protocol I.451/Q.931 is used on the D
`channel to establish, maintain and terminate connections on
`B channels.
`The D channel is primarily used for Signaling purposes
`and is used to dial the number of the destination terminal and
`establish the connection by which the data is transmitted
`from the Source terminal 1 to the destination terminal 2 over
`the B channels. However, as presently recognized, once the
`D channel connection is established, the D channel may
`continue to be used free of charge to receive another call or
`to make additional connections for the Second line, third line
`or the like, provided that the Subchannelization feature is
`incorporated into the ISDN architecture. Thus, a synergistic
`effect of combining Subchannelization with aggregating two
`B channels is that the common D channel allows for all the
`information regarding Setup connections to be done by the D
`channel, without an additional charge to the ultimate users.
`FIG. 3 illustrates the Signaling Sequence between the
`Source facility 1 and the ISDN switch 22. In order to
`establish each B channel connection between the Source
`facility 1 and the destination facility 2, an initial communi
`cation link must be established on the D channel between the
`Source facility 1 and the destination facility 2. To this end,
`a Series of messages is Sent back and forth between the
`Source facilities 1 and the ISDN Switch 22. This communi
`cation between the Source facilities 1 and ISDN Switch 22
`occurs on a continuing basis on the D channel, while
`communications are maintained between the Source facili
`ties 1 and destination facilities 2 on one of the B channels.
`AS shown in FIG. 3, Several different messages are Sent
`between the Source facilities 1 and ISDN Switch 22 while the
`D channel is maintained. A similar, redundant procedure is
`performed when the second B channel is established for
`bonding or multilink PPP purposes.
`The direction of the arrows in FIG. 3 indicates a direction
`of communication between the Source facilities 1 and the
`ISDN Switch 22. The process for establishing a connection
`is initiated by the Source facilities 1 by first Sending a Setup
`message. Particular features of the Setup message will be
`discussed with respect to FIG. 4, however the purpose of the
`Setup message is to provide general information regarding
`the request to connect to the ISDN Switch 22. Next, the
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`S
`ISDN Switch 22 responds with a call proceeding message
`that indicates that call establishment has been initiated.
`Subsequently, the ISDN Switch 22, Sends a connect message
`that indicates call acceptance by the Source facilities 1. The
`Source facilities 1 then sends a connect acknowledge Signal
`that indicates the user has been awarded the call. When the
`user wishes to disconnect a call, the user Sends a disconnect
`message via the source facilities 1 to the ISDN switch 22,
`requesting connection clearing. In response, a release mes
`sage is sent from the ISDN switch 22, indicating the intent
`to release the channel and call reference. In response the
`Source facilities 1 issues a release complete message, indi
`cating that the release of the channel and the call reference.
`Subsequently, the call and information flow through the B
`channel is terminated.
`FIG. 4 shows the structure of a conventional ISDN D
`channel Setup message. The Setup message includes respec
`tive LAPD frames (e.g., 501, 503 . . . ) of different sizes
`(measured in Octets). The message includes a flag frame 501
`that is one octet in length, followed by a Service access point
`identifier (SAPI) frame 503 having a command/response bit
`(CR) and address field extension bit (0). The SAPI frame
`503 is joined with the terminal end point identifier (TEI)
`frame 505, each of which are one octet in length. A control
`frame 507, is one or two octets in length, and is followed by
`an information frame 509, which has a variable length
`between 0 and 128 Octets. A frame check Sequence frame
`511 follows and occupies two octets in length. An end frame
`513 Serves as an end of Setup message flag.
`The SAPI frame 503 includes a first subfield “SAPI”, that
`identifies a protocol layer-3 user, as well as Subframes C/R
`and 0, that are used as a predetermined formatting feature of
`SAPI. The terminal end point identifier frame 505, is used to
`provide a unique terminal end point identifier that is used to
`identify the user's equipment. The control frame 507 defines
`the type of frame format that will be employed Such as an
`information frame, Supervisory frame, and unnumbered
`frame for example. The information frame 509, includes a
`variable number of octets varying from 0 to 128 and contains
`respective Subfields that contain any Sequence of bits that
`form an integer number of octets.
`Thus, when a user wishes to Send data to a destination,
`information in the information field is passed directly to the
`destination user without the ISDN switch deciphering the
`contents of the information. Following the information field
`509, the frame check sequence 511 is included and performs
`an error-detection function by calculating a code from the
`remaining bits of the frame, exclusive of the flags. The
`normal code is a cyclical redundancy check code. Finally,
`the end flag frame 513, includes a specific code indicating
`the end of the Setup message.
`As identified by the present inventor, a limitation with the
`conventional ISDN setup architecture is that there is no
`Suitable approach for arranging a single 128 kbps connection
`between a Source terminal and a destination terminal, by
`way of the ISDN switch. Nor does the conventional ISDN
`Setup architecture enable the feature of Subchannelization, or
`1xN communications as discussed in co-pending Applica
`tion entitled “Method and Apparatus for Sending a 1xN
`Communication Message”. Because the conventional ISDN
`Switch handles the different B channels independently, the
`ISDN Switch imparts a significant degree of uncertainty
`regarding the communications paths assigned to different B
`channels that both have common origins and destinations
`the net result being different, and perhaps non-static, inter
`channel delay. Conventional bonding and multilink PPP
`based Systems overcome the delay obstacle imposed by the
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`ISDN switch by employing more expensive and complex
`Source and destination equipment So as to accommodate the
`processing and management overhead for “combining two
`B channels. Furthermore, many conventional ISDN termi
`nals Such as G3 facsimile machines, are not configured to
`communicate over a 128 kbps link, as it is presumed that no
`more than 64 kbps is available for facsimile transmissions.
`Neither do conventional ISDN terminals, such as G3 fac
`Simile machines, enable the operation of Subchannelization,
`where channel Speeds range from 1 kbps to 128 kbps
`depending on usage demands/requests.
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`SUMMARY OF THE INVENTION
`Accordingly one object of the present invention is to
`provide a novel method, apparatus and System that provides
`expanded data rates in ISDN networks and subchanneliza
`tion of ISDN channels for use in 1xN messaging that
`overcomes the above limitations of existing methods, appa
`ratuses and Systems.
`It is a further object of the present invention to provide a
`Source ISDN terminal configured to transmit a request
`message to a network Switch, indicating that the Source
`terminal requests that the network Switch handle one or both
`B channels as a composite channel for transmission of one
`or more Subchannels having a composite data rate of up to
`128 kbps.
`It is yet another object of the present invention to provide
`a method and network Switch that establishes the composite
`channel with Subchannelization between the Source terminal
`and one or more destination terminal(s).
`These and other objects are achieved with an inventive
`method, apparatus and System that forms a Setup message at
`a Source terminal, a non-exhaustive description of which
`follows. The Setup message includes a request for Subchan
`nelization of one or both B channels So as to maximize
`communication efficiency when Sending a 1xN message to
`one or more destination facilities, or Separate messages to
`one or more facilities. The Source terminal Sends the Setup
`message with the request to the Switch, where the Switch
`invokes a channel and bandwidth coordination mechanism
`that Subdivides the bandwidth of one or both B channels for
`communication between the Source terminal, and one or
`more destination terminals. The Setup message also indi
`cates whether or not a 1xN extension message is included.
`When a data message is sent to more than one destination
`facility, a request is made for a desired data rate to be used
`for each of the destination facilities identified in the setup
`message. The Switch then determines whether both B chan
`nels are needed to Support the communication request made
`by the Source terminal and determines whether the commu
`nication resources are available at the identified destination
`terminal(s). When one of the destination terminal(s) cannot
`Support the requested communication capacity requested by
`the Source terminal, that destination terminal offers a counter
`proposal to at least one of the Switch and/or Source terminal.
`If the counter proposal is accepted by the Source terminal
`and/or Switch, the Switch changes the communication Speed
`to that destination terminal. In this way, the communication
`capacity of one or both of the B channels is optimized when
`Sending either a regular data message or a 1xN extension
`message to one or more destination terminals.
`A facet of the present invention is the use of a modified
`ISDN Switch, modified to handle two B channels as a single
`channel, the combined channel capacity of which may be
`Subchannelized based on user requests. The modified Switch
`includes a processor-based channel and bandwidth coordi
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`

`7
`nation mechanism configured to determine if a Source ter
`minal requests Subchannelization of one or both B channels
`and coordinates the allocation of the available bandwidth
`from the one or both of the B channels to respective
`destination facilities identified as recipients of the message
`(S) from the Source terminal.
`BRIEF DESCRIPTION OF THE DRAWINGS
`A more complete appreciation of the invention and many
`of the attendant advantages thereof will be readily obtained
`as the Same becomes better understood by reference to the
`following detailed description when considered in connec
`tion with the accompanying drawings, wherein:
`FIG. 1 is a block diagram of a conventional ISDN
`communication System;
`FIG. 2 is a conventional frame Structure for communi
`cating between a source terminal and an ISDN switch in
`ISDN basic rate access;
`FIG. 3 is a conventional control Signaling protocol for
`ISDN basic services;
`FIG. 4 is a conventional link acceSS protocol D channel
`message format for a Setup message using an I.451/Q.931
`meSSage Structure,
`FIG. 5 is a block diagram of Smart bandwidth allocation
`System including a data rate expansion mechanism and a
`channel and bandwidth coordination mechanism according
`to the present invention;
`FIG. 6 is a block diagram of the Signal processing
`mechanisms and Selected components in a Source, or
`destination, terminal according to the present invention;
`FIG. 7 is a block diagram of components included in a
`processor of the digital network Switch according to the
`present invention;
`FIG. 8 is a block diagram of components included in a
`Source terminal or destination terminal;
`FIG. 9 is a plan view of a display and a keypad of the
`Source terminal of FIG. 5;
`FIG. 10 is a modified link access protocol of the D
`channel (LAPD) setup message structure incorporating a
`1xN coordination message and bandwidth coordination
`message according to the present invention;
`FIG. 11 is a block diagram of a bandwidth coordination
`meSSage,
`FIG. 12 is a flowchart of a method for initiating a
`Subchannelization communication Session according to the
`present invention; and
`FIG. 13 is a flowchart of a process implemented in the
`modified ISDN switch for identifying and coordinating the
`Subchannelization features of the present invention as initi
`ated by the Source terminal.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`Referring now to the drawings, wherein like reference
`numerals designate identical or corresponding parts
`throughout the Several views, and more particularly to FIG.
`5 thereof, there is illustrated a modified integrated digital
`service network (ISDN) system 1000 in which a source
`terminal 100 of a source facility 101 communicates with
`multiple destination facilities 2A to 2N via an ISDN Switch
`220, modified to provide a 1xN switch function and Sub
`channelization function, as will be explained herein. The
`Source terminal 100 is included in the source facilities 101,
`located