US006930998B1
`
`(12) United States Patent
`Sylvain et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,930,998 B1
`Aug. 16, 2005
`
`(54) HYBRID TDM AND ATM VOICE
`SWITCHING CENTRAL OFFICE AND
`METHOD OF COMPLETING INTER_0FFICE
`CALLS USING SAME
`
`(75) Inventors: Dany Sylvain, Gatineau (CA); Faizel
`Lakhani, Kanata (CA)
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`W0
`W0
`
`0719068 A2
`0792076 A2
`WO 95/17789
`WO 98/28901
`
`6/1996
`8/1997
`6/1995
`7/1998
`
`........ .. H04Q 11/04
`H04Q 3/00
`H04L 12/64
`......... .. H04M 3/50
`
`* eieed by examiner
`
`(73) Assignee. £21236 Networks Limited, St. Laurent
`
`.
`
`_
`
`.
`
`.
`
`Primary Examiner—John PeZZlo
`
`Assistant Examiner_saba Tsegaye
`(74) Attorney, Agent, or Firm—WithroW & Terranova,
`PLLC
`
`ABSTRACT
`(57)
`A hybrid central of?ce for serving a plurality of subscriber
`lines While serving as a virtual access tandern to a subnet
`Work of central of?ces having a connection to an ATM
`backbone network is described. The hybrid central office
`includes a computing rnodule having a rnessaging interface
`to the ATM network, an intepworking trunk interface to the
`ATM netWork and a trunk connection to the PSTN. The
`hybrid Central of?ce Serves as a tandem Switch for other
`central of?ces connected to the subnetWork. Other central
`O?ices are preferably Connected to [he Subnetwork
`a
`signal large trunk group. All inter-of?ce call routing is
`therefore handled by the hybrid central of?ce. The hybrid
`central office also provides a gateWay to the PSTN. Inter
`of?ce calls originated and terminated Within the subnetWork
`are set up by the virtual access tandem but after call set up,
`the virtual access tandern is not involved in the call. The
`advantage is the utilization of Spare processing Capacity in a
`central of?ce to off-load inter-of?ce trunking congestion, as
`Well as a signi?cant reduction in trunking rnaintenance
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) APPL NO-I 09/206,277
`_
`(22) Flled:
`
`Dee- 7’ 1998
`
`(51) Int. Cl.7 ............................................. .. H04L 12/66
`
`(52) US. Cl. ................ .. 370/352; 370/353; 370/395.61
`
`of Search .............................. ..
`3705951939552,395-61,400—401,465—466
`
`(56)
`
`References Cited
`Us PATENT DOCUMENTS
`
`4/1993 Obara ...................... .. 370/354
`5,204,857 A *
`5,838,682 A * 11/1998 Dekelbaum et al. ...... .. 370/401
`
`' ' ' ' '
`
`' ' ' "
`
`2/2002 Liu et al. ............... .. 370/238
`6,349,096 B1 *
`2001/0028644 A1 * 10/2001 Barzegar et al.
`370/352
`2002/0010818 A1 *
`1/2002 Wei et al. ................... .. 710/62
`
`Costs'
`
`50 Claims, 7 Drawing Sheets
`
`44
`
`D
`TC
`
`42
`
`IW-MSP
`
`Hybrid Central Office
`A
`<__:>_ 23
`
`50
`
`“34
`
`CO
`
`20
`
`CO
`
`Petitioner Apple Inc. - Ex. 1016, p. 1
`
`

`

`U.S. Patent
`
`Aug. 16, 2005
`
`Sheet 1 0f 7
`
`US 6,930,998 B1
`
`————— --
`
`CM
`
`<1‘ 46
`40
`____.._.._. _.._:.._.
`
`I
`
`41
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`l
`DTC \ 42
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`~
`
`-
`
`IW MSP
`
`l \
`
`Hybrid Central Office
`>~
`28
`
`5O
`
`22
`
`( 48
`
`A
`T
`
`M
`
`/
`26
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`28 > 50 \, f 48
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`:
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`.
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`DA-MSP
`
`CO
`
`__--_.-_--.______’_.________
`
`Petitioner Apple Inc. - Ex. 1016, p. 2
`
`

`

`U.S. Patent
`
`Aug. 16,2005
`
`Sheet 2 0f 7
`
`US 6,930,998 B1
`
`40
`
`lnterworking Translation and Routing
`
`Connectivity Control
`
`/ Messaging Connectivity
`
`FIG. 2
`
`C Call Origination D
`
`Originator
`Fabric?
`
`Attempt to Route _/ 54
`on TDIVi Fabric
`
`Attempt to Route
`on ATM Fabric
`
`Termintor
`Fabric?
`
`K 58
`TDIVI CCJII
`(TDM <--> TDM)
`
`HYBRID Call
`(TDM <--> ATM)
`FIG. 3
`
`Termintor
`Fabric?
`
`ATM Call
`[ATM <--> ATM)
`
`Petitioner Apple Inc. - Ex. 1016, p. 3
`
`

`

`U.S. Patent
`US. Patent
`
`Aug. 16,2005
`Aug. 16, 2005
`
`Sheet 3 0f 7
`Sheet 3 0f 7
`
`US 6,930,998 B1
`US 6,930,998 B1
`
`
`
`Petitioner Apple Inc.
`
`- EX. 1016, p. 4
`
`Petitioner Apple Inc. - Ex. 1016, p. 4
`
`

`

`U.S. Patent
`US. Patent
`
`Aug. 16,2005
`Aug. 16, 2005
`
`Sheet 4 0f 7
`Sheet 4 0f 7
`
`US 6,930,998 B1
`US 6,930,998 B1
`
`32
`
`
`
`34
`
`CO
`FIG. 5
`
`Petitioner Apple Inc.
`
`- EX. 1016, p. 5
`
`Petitioner Apple Inc. - Ex. 1016, p. 5
`
`

`

`U.S. Patent
`
`Aug. 16,2005
`
`Sheet 5 0f 7
`
`US 6,930,998 B1
`
`DA-MSP
`
`CO
`
`DA-MSP —
`CO
`
`___'_AM __________________ ___>.
`IAM Advisory
`)
`IAM ACK
`, IAM Advisogy
`4 ‘
`IAIVI ACK
`Connection Re ues’r
`SVC Requeg
`>
`
`4 .
`Snvchromze
`‘
`
`SvnchAck
`JAM ____________________ "H
`___________________ __A_Q__
`A M Advisory
`ACM AEIK
`
`ACM Advisory
`‘
`ACM ACK
`,
`ANM
`.
`ACM
`{- ----------------------- --<_ _______________________ __
`
`ANM Advisor ANM AgK
`ANM Advisog+_______
`‘
`ANM ACK
`,
`
`CONVERSATION
`
`REL Adviso
`
`R L Advisor
`
`REL AC!
`
`REL ACK
`
`RLC Adviso RLC Advlsory
`CACHE SVC
`‘
`
`>
`Cache ACK
`
`FIG. 6
`
`Petitioner Apple Inc. - Ex. 1016, p. 6
`
`

`

`U.S. Patent
`
`Aug. 16,2005
`
`Sheet 6 6f 7
`
`US 6,930,998 B1
`
`szék“
`
`24
`./
`
`44
`
`22 72
`
`/
`
`IW-MSP
`
`68 Q
`
`-
`
`DA-MSP —
`CO
`
`>
`IAM ACK
`>
`
`HCO
`,
`___|_AM_> IAM Advisory
`(
`IAM ACK
`IAM Advisorv
`
`Connection Request
`Connection Request,
`
`‘
`Snycnronize
`IAM
`SyncnAok
`I
`_______________________________________ "69M:
`ACM Advisory
`<
`ACM AC}?
`
`ACM Advisogy
`ACM AC
`
`_
`
`ACM ‘
`4 ----- u‘ _____ ___ ______________________________ __/iN_'\_/L
`ANM Advlsorv
`ANM ACK
`AhM Adviso
`ANM AC?
`ANM“
`
`4. _____ .._
`
`CONVERSATION
`
`_______________________________________ "BEL.
`R L Advisorv
`)
`(
`REL ACK
`REL Advisor
`
`,
`
`_
`
`REL AC ‘
`
`————B§L—B_L9 ______________________________________ n’
`B-Lg- —— - ) RLC Advisory
`)
`RLC Advisog
`
`,
`
`Coone SVC
`+
`
`Cocne ACK
`
`FIG. 7
`
`Petitioner Apple Inc. - Ex. 1016, p. 7
`
`

`

`U.S. Patent
`
`Aug. 16,2005
`
`Sheet 7 0f 7
`
`US 6,930,998 B1
`
`68 Q
`22 72W \
`44
`-
`f-
`IW-MSP @ DA-MSP
`
`co
`
`24
`./
`
`Hco
`,
`___|_A\£'_> IAM Advisory
`1
`IAM ACK
`(——————
`_ Connection Regues?
`A
`
`AM Advisory
`
`I
`
`IAM ACK
`
`IAM Advisory
`
`>
`IAM ACK
`>
`Connection Request
`Connection Request
`Snychronize
`> ‘
`SynchAck
`,
`IAM
`__________________________________________ ___>
`
`ACM ACK
`
`ACM Advisory
`4 _
`ACM Advisory
`ACMA K
`ACM <-—-—
`4 _____ __
`‘m We?“
`ANM ACK>
`4ANIVI Advisor
`ANM m
`
`,-__-----______---__-___-____
`
`CONVERSATION
`(See Coll Releose Sequence Shown in FIG. 7)
`
`FIG. 8
`
`Petitioner Apple Inc. - Ex. 1016, p. 8
`
`

`

`US 6,930,998 B1
`
`1
`HYBRID TDM AND ATM VOICE
`SWITCHING CENTRAL OFFICE AND
`METHOD OF COMPLETING INTER-OFFICE
`CALLS USING SAME
`
`TECHNICAL FIELD
`
`The present invention, relates to the transfer of voice and
`voice grade telephone data over asynchronous transfer mode
`(ATM) facilities and, in particular, to a novel subnetWork
`arrangement in Which a central office serves a plurality of
`subscriber lines While serving as a virtual access tandem to
`a subnetWork of central of?ces having a connection to an
`ATM backbone netWork.
`
`10
`
`15
`
`BACKGROUND OF THE INVENTION
`
`The introduction of the Internet to the general public and
`the ensuing explosion of interest and demand for access to
`the Internet through telephone service provider netWorks has
`placed considerable strain on existing telecommunications
`infrastructure. Telephone service provider netWorks are noW
`being overWhelmed by the explosion of data traffic over an
`infrastructure that Was not intended for and is not capable of
`supporting the exponential increase in demand currently
`being experienced. This exponential increase in demand is
`particularly responsible for the exhaustion of resources at
`the access tandem level of the public sWitched telephone
`netWork (PSTN).
`Concurrently With the explosion and demand for tele
`phone services, most regulatory authorities have noW
`opened the telephone service market to competition. Con
`sequently, the incumbent service providers no longer enjoy
`a monopoly Which makes massive capital investment in
`infrastructure attractive. There has therefore been a notable
`interest in neW methods for increasing call handling capacity
`and reducing overhead and operating costs. Voice and voice
`grade data services over ATM netWorks have been proposed
`by several equipment providers as an alternative architecture
`for neW infrastructure to augment the PSTN. The inherent
`advantages and disadvantages of ATM netWorks are Well
`knoWn. ATM offers ?exible routing solutions Which enable
`more efficient use of resources than the traditional hierar
`chical structure Which has evolved in the PSTN. HoWever,
`current ATM sWitches are incapable of call set up rates
`expected by the general public. Nonetheless, the diligent
`application of ingenuity has substantially overcome the
`disadvantages of the use of ATM to support voice and voice
`grade data services and ATM subnetWorks are being con
`structed to off-load portions of the bearer traffic contributing
`to congestion in the PSTN.
`Aprincipal focus of the technical developments respect
`ing the use of ATM netWorks to relieve congestion in the
`PSTN has been the use of ATM netWorks as a transport
`backbone for voice and voice grade data. While this focus
`has lead to the invention of many valuable tools useful in
`providing reliable service at competitive rates, the problem
`of inter-of?ce trunking groWth has only been partially
`addressed. There therefore exists a need for a method and
`apparatus capable of handling trunking groWth economi
`cally, While reducing overhead maintenance costs in order to
`enable the provision of telephone services at competitive
`prices.
`
`25
`
`35
`
`40
`
`45
`
`55
`
`65
`
`2
`SUMMARY OF THE INVENTION
`
`It is therefore a primary object of the invention to provide
`a hybrid central office for serving a plurality of subscriber
`lines While also serving as a virtual access tandem to a
`subnet of central of?ces connected to an ATM backbone
`netWork.
`It is a further object of the invention to provide a subnet
`Work of central offices in Which each of the central offices
`are connected by a trunk group to an ATM-based virtual
`access tandem, Which is responsible for routing all calls
`originating in or terminating in the subnetWork.
`It is yet a further object of the invention to provide a
`subnetWork in Which the virtual access tandem is respon
`sible for routing calls originating and terminating in the
`subnetWork.
`It is yet a further object of the invention to provide a
`telephone subnetWork Which utiliZes an ATM backbone for
`completing sWitched telephone calls in Which a plurality of
`central offices are connected to the ATM backbone by
`interfaces for converting pulse code modulated (PCM) data
`to ATM cells and vice versa, and one of the plurality of
`central offices is adapted to function as a virtual tandem for
`the subnetWork.
`It is yet a further object of the invention to provide a
`method of completing an inter-of?ce call originating at a
`central office in a subnetWork that includes a plurality of
`central offices which respectively serve a plurality of sub
`scriber lines, a one of the central of?ces serving as a virtual
`tandem for the subnetWork.
`The invention therefore provides a hybrid central office
`for serving a plurality of subscriber lines While serving as a
`virtual access tandem to a subnetWork of central of?ces
`having a connection to an ATM backbone netWork, com
`prising an inter-Working bearer traf?c interface to the ATM
`backbone netWork to permit the hybrid central office to
`receive bearer traffic from and transfer bearer traffic to any
`one of the central offices in the subnetWork, the inter
`Working bearer traffic interface being adapted to convert
`pulse code modulated (PCM) data to ATM cells and vice
`versa; a trunk interface to the public sWitched telephone
`netWork (PSTN) to permit the hybrid central office to receive
`PCM data from and transfer PCM data to the PSTN; and a
`computing module having a signaling interface to the ATM
`backbone netWork to permit the computing module to send
`messages to and receive messages from any one of a
`plurality of distributed-access bearer traf?c interfaces
`respectively associated With the central offices in the sub
`netWork, the computing module being adapted to access
`information for routing inter-office calls originated at or
`terminated at any one of the central of?ces.
`In accordance With a further aspect of the invention there
`is provided a telephone subnetWork Which utiliZes an ATM
`backbone for completing sWitched telephone calls, compris
`ing in combination a plurality of central of?ces connected to
`the ATM backbone by respective interfaces for converting
`PCM data to ATM cells and vice versa, each of the central
`of?ces being respectively adapted to serve a plurality of
`subscriber lines; and a one of the plurality of central of?ces
`being further adapted to function as a virtual tandem for the
`subnetWork and to control inter-office call routing for calls
`that originate or terminate in the subnetWork.
`In yet a further aspect of the invention, there is provided
`a method of completing an inter-of?ce call originating at a
`central office in a subnetWork that includes a plurality of
`central offices which respectively serve a plurality of sub
`scriber lines, each of the central of?ces being connected to
`
`Petitioner Apple Inc. - Ex. 1016, p. 9
`
`

`

`US 6,930,998 B1
`
`3
`an ATM backbone network by an interface that converts
`PCM data to ATM cells and vice versa, a one of the central
`of?ces serving as a virtual tandem for the subnetWork,
`comprising the steps of:
`a) at the originating central of?ce, formulating an IAM
`relating to the inter-of?ce call, the IAM containing a desti
`nation point code (DPC) of the virtual tandem;
`b) receiving the IAM at the virtual tandem and translating
`a called number in the IAM to determine a next hop
`destination for the call;
`c) modifying the IAM to change an originating point code
`(OPC) to the point code of the virtual tandem and the
`destination point code (DPC) to the point code of the next
`hop destination for the call, and forWarding the modi?ed
`IAM to the next hop destination for the call;
`d) formulating a fabric control message and sending the
`fabric control message through the ATM backbone to a
`terminating interface in the subnetWork to enable a virtual
`circuit through the ATM backbone to transfer the call; and
`e) sending a connection message from the terminating
`interface in the subnetWork to an interface associated With
`the originating central of?ce to enable the virtual circuit for
`transferring the call through the ATM backbone.
`The invention therefore provides a novel structure for a
`subnet of central of?ces connected to an ATM backbone
`Which is adapted to relieve inter-of?ce trunking congestion
`While providing an efficient netWork structure that enables
`competitive pricing of telephone services. In accordance
`With the novel subnetWork structure, a plurality of central
`of?ces are connected by interfaces to an ATM backbone
`netWork. One of the central of?ces, preferably one having
`the most idle computing capacity, is designated as a virtual
`tandem for the subnetWork. That central of?ce can maintain
`time division multiplexed (TDM) trunk groups connected to
`other central of?ces. Each of the central offices in the
`subnetWork are connected to the ATM backbone via inter
`faces Which convert pulse code modulated (PCM) data to
`ATM cells and vice versa. Each of the central of?ces in the
`subnetWork are preferably connected to the respective inter
`faces by a single large trunk group. Consequently, all
`inter-of?ce calls originated at any one of the central of?ces
`aside from the virtual access tandem are routed to the large
`trunk group. A link set associated With the large trunk group
`points to the virtual access tandem. As a result, the virtual
`access tandem is responsible for the routing of all inter-of?ce
`calls originated Within or terminated Within the subnetWork.
`Routing and translation tables for the subnetWork are there
`fore centraliZed in the virtual access tandem. Consequently,
`translation and routing table maintenance is centraliZed and
`more efficient. Furthermore, maintenance costs for the
`physical trunking at each central of?ce are signi?cantly
`reduced because the only trunking required is a large high
`capacity trunk, Which may be a high speed optical link
`betWeen each central of?ce and the respective interface(s).
`The invention therefore provides a cost effective, ef?cient
`apparatus and method for relieving congestion in the PSTN
`Which utiliZes existent infrastructure in a very ef?cient and
`effective Way.
`
`10
`
`15
`
`25
`
`35
`
`40
`
`45
`
`55
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention Will noW be explained by Way of example
`only and With reference to the folloWing draWings, Wherein:
`FIG. 1 is a schematic diagram illustrating the principal
`components of a hybrid central of?ce in accordance With the
`invention shoWn in relation to portion of a subnetWork in
`
`65
`
`4
`accordance With the invention, as Well as the PSTN and a
`common channel signaling netWork associated With the
`PSTN;
`FIG. 2 is a schematic diagram shoWing the computing
`module of the hybrid central of?ce shoWn in FIG. 1 and
`detailing the principal functional components of the com
`puting module adapted to function in accordance With the
`invention;
`FIG. 3 is a How chart shoWing the logic of the computing
`module call-type determination function used for inter
`Working translation and routing as Well as connection broker
`connectivity control;
`FIG. 4 is a schematic diagram shoWing the signaling
`sequence and signaling paths for an inter-of?ce call com
`pleted betWeen tWo end of?ces in a subnetWork in accor
`dance With the invention;
`FIG. 5 is a schematic diagram shoWing a signaling
`sequence and signaling paths for a call Which originates in
`the PSTN and terminates at a central of?ce in a subnetWork
`in accordance With the invention;
`FIG. 6 is a call sequence diagram illustrating principal
`signaling message exchanges betWeen netWork elements in
`the call sequence shoWn in FIG. 4; and
`FIG. 7 is a call sequence diagram illustrating the principal
`signaling messages exchanged betWeen netWork elements in
`a call sequence shoWn in FIG. 5.
`FIG. 8 is a call sequence diagram illustrating the principal
`signaling messages exchanged betWeen netWork elements in
`an alternate method for implementing the call sequence
`shoWn in FIG. 5.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`This invention relates to a subnetWork of telephone cen
`tral of?ces connected through interfaces to an ATM back
`bone netWork. Aone of the central of?ces is adapted to serve
`as a virtual access tandem in the subnetWork so that inter
`of?ce trunk congestion is relieved in the subnetWork.
`System OvervieW
`FIG. 1 shoWs a portion of a subnetWork of central of?ces
`generally indicated by the reference 20 having a connection
`to an ATM backbone netWork 22. The subnetWork includes
`a plurality of central of?ces, only three of Which are shoWn
`in FIG. 1 due to space constraints. Aone of the central of?ces
`is a hybrid central of?ce 24 Which serves a plurality of
`subscriber lines (not shoWn) While serving as a virtual access
`tandem to the subnetWork 20 of central of?ce 26, each of
`Which have a connection to the ATM backbone netWork 22.
`As Will be appreciated by those skilled in the art, the hybrid
`central of?ce 24 is also connected by existing time-division
`multiplexed (TDM) trunk groups 28 to the public sWitched
`telephone netWork (PSTN) 32 and to the other central of?ces
`26. The other central of?ces 26 are likeWise interconnected
`by existing TDM trunk groups 28. As is also understood by
`those skilled in the art, associated With PSTN 32 is a
`common channel signaling netWork 34 Which typically
`operates under a Signaling System 7 (SS7) protocol Which
`permits central of?ces to communicate With other nodes in
`the PSTN.
`In order to ensure that incumbent infrastructure is utiliZed
`as ef?ciently as possible, the hybrid central office 24 is
`modi?ed only to an extent required to enable it to perform
`the functions required of the hybrid central of?ce 24 Which
`serves as a virtual access tandem in the subnetWork 20. Each
`central of?ce includes computing module (CM) 40 and a
`
`Petitioner Apple Inc. - Ex. 1016, p. 10
`
`

`

`US 6,930,998 B1
`
`15
`
`25
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`35
`
`40
`
`5
`TDM switch fabric 41 Which provides a link between
`subscriber lines and trunks for switching bearer traf?c.
`Attached to the sWitch fabric 42 are digital trunk controllers
`(DTC) 42 Which provide an interface to the PSTN 32 and
`inter-Working multi-service platforms (IW-MSP) 44 Which
`provide an interface to the ATM netWork 22. The interfaces
`to the ATM netWork perform several functions Which Will be
`described beloW in more detail. One of their primary func
`tions is to convert pulse code modulated (PCM) voice and
`voice grade data to ATM cells, and vice versa.
`The computing module 40 has a signaling interface 46
`With the ATM backbone netWork 22 to permit the computing
`module 40 to send messages to and received messages from
`distributed access MSPs (DA-MSP) 48 Which serve as
`interfaces to the ATM netWork 22 for the respective central
`offices 26. As described in Applicant’s co-pending patent
`application entitled APPARATUS AND METHOD FOR
`COMPLETING INTER-SWITCH CALLS USING LARGE
`TRUNK GROUPS Which Was ?led by the Applicant on Dec.
`2, 1998 and is now US. Pat. No. 6,141,342, each of the
`central offices 26 is preferably connected to the ATM back
`bone netWork 22 by a single large trunk group 50. Con?g
`uring each of the end offices 26 With a single large trunk
`group has several distinct advantages as thoroughly
`explained in Applicant’s co-pending patent application, the
`entirety of Which is incorporated herein by reference.
`FIG. 2 is a schematic diagram of the computing module
`40, shoWn in FIG. 1, and the principal functional compo
`nents of the invention developed and added to enable the
`hybrid central office to function as a virtual access tandem
`to the subnetWork 20 shoWn in FIG. 1.
`The principal functional components added to the com
`puting module 40 include inter-Working translation and
`routing, connectivity control and messaging connectivity,
`each of Which is brie?y characteriZed as:
`Inter-Working Translation and Routing—Since each of
`the central offices is preferably connected to the sub
`netWork by a single large trunk group, the translation
`and routing tables in those central offices are extremely
`simple. All inter-of?ce calls are routed to the single
`large trunk group. Consequently, it is the responsibility
`of the hybrid central office 24 to perform routing and
`translation functions for all calls that originate or
`terminate in the subnetWork 20. The translation and
`routing Will be explained beloW in more detail. A
`further inter-Working function is the responsibility for
`minimizing the incidence of inter-Working call types,
`i.e., calls Which originate in the ATM backbone and
`terminate in the PSTN. In order to accomplish this, the
`inter-Working function must determine the character of
`the originating fabric base prior to evoking an algo
`rithm shoWn beloW in FIG. 3.
`Connectivity Control—The connectivity control function
`of the Computing Module 40 performs several critical
`functions. Connectivity control is required for all calls
`Which involve an ATM component. Connectivity con
`trol is consequently required for all calls Which origi
`nate or terminate in the subnetWork 20. A further
`function of connectivity control is the selection of an
`inter-Working bridge for calls Which originate in the
`ATM netWork and terminate in the PSTN, or vice versa.
`The inter-Working bridge is a resource Which is main
`tained and allocated in the computing module 40. An
`inter-Working bridge is required for each inter-Working
`call. A further function of connectivity control is the
`formulation and sending of fabric-control messages
`(FCM) Which are used to establish or allocate sWitched
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`virtual circuits through the ATM backbone for trans
`ferring bearer traffic. The FCMs contain information
`Which is required by the interfaces for the respective
`central offices to enable ATM-related fabric connec
`tions. The content of such messages Will be explained
`beloW in more detail With reference to FIGS. 4—7.
`Messaging Connectivity—Messaging connectivity is a
`fundamental part of any netWork. The messaging con
`nectivity layer hides the ATM nature of the communi
`cation path from the call processing applications of the
`computing module 40. Consequently, proxies operating
`in the messaging connectivity layer accept messages
`from the call processing applications of the computing
`module 40 and convert those messages into ATM cells
`Which are emitted into the ATM backbone netWork 22.
`The proxies likeWise receive messages from the ATM
`backbone netWork 22 and convert them into an internal
`format used by the call processing applications of the
`computing module 40.
`
`ATM NetWork Interfaces
`As shoWn in FIG. 1, interfaces are required betWeen the
`central offices 24, 26 in the subnetWork 20 and the ATM
`backbone netWork 22. Aprincipal function of the interfaces
`44, 48 is to convert PCM data to ATM cells and vice versa.
`For purposes of clarity, the interfaces are identi?ed as
`IW-MSP 44 and DA-MSPs 48. The reason for the distinction
`is that there is some difference in functionality as Will be
`explained beloW. It should be understood, hoWever, that the
`interfaces 44, 48 may be implemented on the same platform
`and require substantially identical hardWare functionality.
`The IW-MSP 44 provides an interface betWeen the hybrid
`central office 24 and the ATM backbone 22. Its principal
`functions are to provide a bridge betWeen the TDM fabric 41
`and the ATM fabric 22. It is also responsible for initiating
`application instances Which oWn inter-Working bridges
`established through the TDM fabric 41 for inter-Working
`calls and the TDM to ATM mapping associated With such
`calls. The IW-MSP also includes a functional entity herein
`after referred to as a “connection broker” Which serves the
`functions of TDM component connection control; inter
`Working bridge connection control; ATM component con
`nection control; the ATM-to-TDM interface and ATM-to
`TDM path conversion.
`The IW-MSP 44 connection broker may provide SVC
`caching services for TDM fabric to ATM bridged calls. ATM
`SVCs are sWitched virtual connections through the ATM
`netWork, Which are preferred over permanent virtual con
`nections because they permit more efficient use of netWork
`resources. In this context, the majority of the connection
`broker functionality actually resides in the DA-MSP 48
`Which is preferably delegated as master of the SVC cache
`betWeen itself and the IW-MSP 44, as Will be explained
`beloW in more detail. It should be understood, hoWever, that
`cached SVCs are not required and an SVC may be set up for
`each call routed through the ATM fabric 22. The IW-MSP 44
`also supports an ATM signaling interface and the connection
`broker must be adapted to interact With an ATM signaling
`stack for the purposes of cached SVC control. HoWever, the
`IW-MSP 44 preferably only terminates cached SVCs Which
`are controlled by the DA-MSPs 48. In order to support TDM
`fabric to ATM bridged calls, the IW-MSP 44 supports a
`connection to the TDM sWitch fabric 41 and a connection to
`the ATM backbone netWork 22. A messaging interface
`betWeen the IW-MSP 44 and the DA-MSPs 48 is also
`required. Call processing requires that messages be
`
`Petitioner Apple Inc. - Ex. 1016, p. 11
`
`

`

`US 6,930,998 B1
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`7
`exchanged between the interfaces in order to start integrity
`checking, report integrity failures, etc.
`The DA-MSPs 48 likewise support a trunk interface
`connection to the central of?ces 26 and an ATM link to the
`ATM backbone netWork 22. The DA-MSPs 48 also include
`a functional component referred to as the connection broker.
`The connection broker preferably, but not necessarily, has
`responsibility for SVC caching to facilitate call set up
`response. In order to enable SVC caching, the connection
`broker must support an ATM messaging stack and an
`application programming interface (API) Which permits the
`DA-SPM connection broker to maintain SVC caches. The
`DA-MSPs 48 also supports all the functionality described
`above With reference to the IW-MSPs, except for the inter
`Working bridge functionality.
`Call-Type Determination
`FIG. 3 is a simple ?oW chart illustrating the logic used by
`the call processing applications of the computing module 40
`to make a call-type determination When a call request is
`received at the hybrid central of?ce 24. Since existing
`inter-of?ce trunks 28 (FIG. 1) may be used to complete calls
`in the subnetWork, the hybrid central of?ce 24 must perform
`a call-type determination for each call request. In step 52, an
`originating point code, for example, of an initial address
`message (IAM) is examined to determine the originator
`fabric of a call. If the call is a TDM fabric call (originating
`in the PSTN or routed over inter-of?ce trunks 28) an attempt
`is made to route the call on the TDM fabric in step 54. This
`is done in order to minimize the amount of inter-Working
`betWeen TDM and ATM sides. In order to route the call on
`the TDM fabric, the terminator fabric must be determined in
`step 56. If the terminator fabric is the TDM fabric, the call
`is determined to be a TDM fabric call in step 58. If the
`terminator fabric is ATM, the call is a hybrid call, as
`determined in step 60. Ahybrid call is a TDM fabric-to-ATM
`or ATM-to-TDM fabric call. If the originator fabric deter
`mined in step 52 is ATM, an attempt is made is step 62 to
`route the call to the ATM fabric. In order to accomplish this,
`the terminator fabric is examined in step 64 and if the
`terminator fabric is TDM, the call is a hybrid call. Other
`Wise, the call is determined to be an ATM call in step 66.
`Intra-SubnetWork Call Example
`FIG. 4 is a schematic diagram of a subnetWork 20 in
`accordance With the invention shoWing signaling paths for
`signal messages involved in the set up of an inter-of?ce call
`betWeen a ?rst central office 68 and a second central of?ce
`70 Which are respectively connected by a single large trunk
`group and DA-MSPs 72, 74 to the ATM backbone netWork
`22.
`A call is originated at the central of?ce 68 When, for
`example, a subscriber goes off-hook and dials a called
`number. In response to the dialled digits, the central of?ce 68
`consults its translation and routing tables and determines
`that the call is an inter-of?ce call. Inter-office calls may be
`routed over the TDM trunks 28 or the single large trunk
`group connected to the ATM netWork 22. In this example,
`the routing tables direct the central of?ce 68 to route the
`inter-of?ce call over the single large trunk group connected
`to the DA-MSP 72, for example, because all TDM trunks
`that could be used for the call are busy. Consequently, the
`central office formulates an SS7 initial address message
`(IAM) containing the called and the calling numbers, as Well
`as other information Well knoWn to persons skilled in the art.
`The common channel signaling netWork routes the IAM to
`the point code of the hybrid central of?ce 24 in a ?rst step
`indicated by the numeral 1 shoWn on the dashed line
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`representing the signaling path through the common channel
`signaling netWork 34. On receipt of the IAM, the hybrid
`central of?ce 24 examines its translation tables and deter
`mines that the dialled digits are served by central of?ce 70,
`also a part of the subnetWork 20. Consequently, the hybrid
`central of?ce 24 modi?es the IAM by:
`1) replacing the originating point code (OPC) With its oWn
`point code;
`2) replacing the destination point code (DPC) With the
`point code of the central of?ce 70;
`3) consulting a table respecting the occupation state of the
`single large trunk group connected to the DA-MSP 74 and
`selecting an available trunk member to serve the call. The
`available trunk member identi?cation (TID) is inserted in
`the circuit identi?cation code (CIC) ?eld of the IAM.
`It should be understood that the hybrid central of?ce 24
`maintains an occupation state table for each trunk member
`of each trunk group connected to a central office in the
`subnetWork 20. Occupation state tables are normally main
`tained and updated by central offices for all trunk groups
`Which terminate on the office. Consequently, enabling the
`hybrid central of?ce 24 to perform this function is a simple
`matter using facilities already available to the computing
`module 40 (FIG. 1). After sending the modi?ed IAM
`th