CA2257667C - Improved telecommunications network - Google Patents

Abstract

This invention relates to arrangements for interconnecting a plurality of stand-alone switches by data and communication channels (the latter typically used for communicating voice signals) in such a way as to make the plurality of switches act as if they were one switch. According to one arrangement of the invention, a method of controlling a plurality of associated key telephone stations within a set of the stand-alone switches is disclosed. The method includes the steps of grouping the set of stand-alone switches into a symbiotic network, and transmitting first display control data messages, over the data network, to second ones of the switches connected to the stations to control displays of the stations.
The method also includes the steps of transmitting display control messages fromthe second switching systems to the stations based on the receipt of the first message in the switching systems and transmitting, over the data network, a request to the first switches to establish a connection from the line or trunk to the stations.
The final step involves establishing a connection from the incoming trunk to thestations. Advantageously, such an arrangement provides a convenient way of achieving the advantages of a giant switch without requiring the capacity of such a switch and without requiring the geographic concentration of traffic necessary to keep the links to a giant switch reasonably short. Advantageously, a virtual symbiotic network provides an economical and flexible solution to the problem ofproviding services such as wide area Centrex.

Description

CA 022~7667 1999-01-13 IMPROVED TELECOMMUNICATIONS NETWORK

This is a division of copending Canadian Patent Application Serial No. 2,174,682 filed on April 22, 1996.
Technical Field This invention relates to improved methods and apparatus for establishing inter-office telecommunications calls.
Problem A recent trend in telecommunications networks is the demand for more and more features and services of a type requiring more than the simple connection 10 of two customers, the called customer being specified by a directory number that directly specifies the switching system serving that customer. Examples include 800 service wherein location of the called party is specified by a data base which converts an arbitrary 800 number into a conventional switch specified number; calls to large automatic call distributor systems wherein a given directory number may15 be served by agents in many locations, complex Centrex arrangements featuringcall forwarding wherein the first number is called but the calls are automatically rerouted to a second number, shared directory service wherein a call is completed to whichever of two or more telephones (for example, a cellular phone and a hometelephone or a group of key telephone stations) answers first, screened calls 20 wherein only outgoing calls to certain destinations or incoming calls from certain sources are completed; and many others.
Many of these situations are handled through the use of intelligent networks and advanced intelligent networks, networks which rely on a data base shared by many switches ffir helping to route calls properly. The requirement to25 access a data base on all calls of a certain class presents problems in m~int~ining a reliable data base and in delaying all calls for the query of such a data base.
Another class of problems is encountered in trying to meet requirements for highly reliable service and in ~ltili7ing expensive resources such as speech recognition systems which are not always efficiently utilized within one switch.

CA 022~7667 1999-01-13 The limitations of a switch are usually determined by the capacity of the switch, the traffic which can be conveniently gathered in one location, and the degree of community of interest among the telephone customers in a particular geographic area. For a particular customer, the community of interest may be S spread over more than one geographic area. This size may not be appropriate for efficient interswitch communications (the size of the trunk groups may be too small); for effcient utilization of expensive resources such as data bases dedicated to switch or speech recognition systems; or for the effective deployment of operation a~lmini.ctration and maintenance systems (switching systems may be too10 small to justify a modern sophisticated Operations, Adminjstration and Maintenance (OA&M) system.
A problem of the prior art is that the size of the switching system may be inconsistent with other factors for giving the most economic service in the face of requirements for sophisticated services.
I 5 Solution The above problems are significantly alleviated and advances made over the prior art through the use of a symbiotic network, i.e., a cluster of interconnected switching systems which appear to the outside world including both the connected customers and the connected public switch telephone network, as a 20 single switch. From the point of view of features offered to each calling customer and each incoming call and features offered to each called customer or each outgoing call, communications between members of the cluster and treated as if they were intraswitch communications through the use of interswitch signaling capabilities for ~cces~ing what is normally considered intraswitch information such 25 as the data base of a single switch, or the control process of a call, between switches of the cluster.
A virtual symbiotic network seeks to provide most of the advantages of a symbiotic network to a preselected portion of the subscribers connected to a plurality of switches. Typically, the portions of subscribers which are associated 30 via such a virtual symbiotic network are the lines of a single customer, for example, an area wide Centrex customer whose lines are served by many switches in different geographic locations. Virtual or real data circuits are provided among CA 022~7667 1999-01-13 the switches of a virtual symbiotic network in order to provide access from one switch to the data of another switch in essentially the same manner as data circuits are provided and used in a symbiotic network. However, the voice connections among the switches of a virtual symbiotic network are made through the public S switched telephone network, through conventional trunk connections, or through connections dedicated to the customer among these switches.
In accordance with one aspect of the present invention there is provided in a telecommunications network comprising a plurality of standalone switches, said plurality of stand-alone switches being interconnected by a data network for 10 transmitting data messages among said plurality of stand-alone switches, a method of controlling a plurality of associated key telephone stations within a set of said plurality of stand-alone switches, said plurality of associated stations connected to a plurality of said switches, comprising the steps of: grouping the set of said plurality of stand-alone switches into a symbiotic network; responsive to receipt in lS a first of the set of said switches of a call on a line or an incoming trunk for ones of said plurality of associated stations, transmitting first display control data messages, over said data network, to second ones of the set of said switches connected to said ones of said stations, to control displays of said ones of said stations; responsive to receipt of said first messages in said second ones of said 2~ switching systems, transmitting display control messages from said second ones of said switching systems to said ones of said stations; responsive to receipt from one of said stations in any of the set of said switches of a message indicating a request to answer said call, transmitting, over said data network, a request to said first of said switches to establish a connection from said line or incoming trunk to said one 25 of said stations; and establishing a connection from said incoming trunk to said one of said stations.
In accordance with another aspect of the present invention there is provided in a telecommunications network comprising a plurality of stand-alone switches, said plurality of stand-alone switches being interconnected by a data 30 network for transmitting data messages among said plurality of stand-alone switches, a method of controlling a plurality of associated key telephone stations within a set of said plurality of stand-alone switches, said plurality of associated CA 022~7667 1999-01-13 stations connected to a plurality of said switches, comprising the steps of:
grouping a set of ports comprising ports of said plurality of associated key telephone stations, into a virtual symbiotic network; responsive to receipt in a first of said switches of a call on an incoming trunk or line for ones of said plurality of 5 associated stations, transmitting first display control data messages over said data network to second ones of said switches connected to said ones of said stations to control displays of said ones of said stations; responsive to receipt of said first messages in said second ones of said switching systems, transmitting display control messages from said second ones of said switching systems to said ones of10 said stations; responsive to receipt from one of said stations in any of said switches of a message indicating a request to answer said call, transmitting over said data network, a request to said first of said switches to establish a connection from said incoming trunk or line to said one of said stations; and establishing a connection from said incoming trunk or line to said one of said stations.
In accordance with yet another aspect of the present invention there is provided a stand-alone telecommunications switch, connected to a plurality of other stand-alone switches by a data network for transmitting messages between said switch and said plurality of other switches, comprising: processor means, responsive to receipt of a call on an incoming trunk or line for ones of a plurality 20 of key telephone stations some of which are connected to other ones of said plurality of stand-alone switches, for controlling tr~n~mi.c~ion over said data network of first control display data messages to ones of said plurality of other switches to control displays of ones of said stations; further responsive to receipt over said data network from one of said plurality of other switches of a message25 indicating a request to answer said call, controlling an extension of a connection from said incoming trunk or line toward said one of said plurality of other switches; and further responsive to receipt of first control display data message from another switch of said plurality of other switches for controlling tr~n~mi.c.cion of a display control message to ones of said key telephone stations connected to30 said switch, and responsive to an answer message from a key telephone stationconnected to said switch for controlling tr~n~mi~ion over said data network of another message indicating a request to answer a call.

CA 022~7667 1999-01-13 - 4a -The work-at-home movement is an important factor in making it desirable to have a symbiotic network, i.e., a network which acts as if it were a single switching system, or a virtual symbiotic network. The presence of such a network means that a line to any telecommunication station served by the network5 can be treated as if it were one extension of a Centrex serving a large customer.
Similarly, such a large customer having a plurality of locations served by different switching systems of the symbiotic or virtual symbiotic network can have its telecommunication stations treated essentially as if they were all served from asingle switching system, i.e., as if they were a single Centrex location. In onelO specific application, a group of secretaries serving a group of principals is normally combined into a key telephone system which may, in turn, be part of a Centrex. In order for the secretaries to serve their principals effectively, the secretaries need a display indicating which telephone stations are currently busy, are currently being alerted so that they may answer incoming telephone calls, and be certain that if15 they are making an outgoing call, no one else will seize the same outgoing telephone line. If a symbiotic or virtual symbiotic network serves this boss/secretary group, the telephone displays are continuously updated.
Brief De~ .lion of the D~
FIG. l is a block diagram of a network in accordance with the 20 principles of the prior art;
FIG. 2 is a block diagram of a symbiotic network and a connected switch;
FIG. 3 illustrates the reception of a call in a symbiotic or virtual symbiotic network;

_ . .

CA 022~7667 1999-01-13 FIGs.4 and 5 illustrate the method of ~cessing data within a symbiotic or virtual symbiotic network;
FIG.6 illustrates the process of establishing a con.le~,lion within a symbiotic network;
S FIG.7 illustrates the process of selecting a path within a symbiotic network;
FIG.8 illustrates the process of selecting an outgoing trunk from a symbiotic network;
FIG.9 illustrates the process of selecting a port of a multi-line hunt 10 group;
FIG.10i~ st~t~s a symbiotic network used to control a key telephone system with key telephone stations connectecl to a plurality of switches of the symbiotic network and to one switch outside the symbiotic nelwc,lk;
FIG.11is a flow diagram of the method for controlling the key 15 telephone system of FIG.10;
FIG.12 illustrates the process of making a conneclion bel~ ,n a port of a symbiotic network and a port outside the symbiotic nelwolk, essentially the same process can be used to establish conneclionS within a virtual symbiotic nelwolk; FIG.13 illustrates a virtual symbiotic r.~,twolk;
FIG.14 illustrates data for implementing a wide area Centrex using a virtual symbiotic network;
FIG.15 illustrates the process of establishing a call in a virtual symbiotic network;
FIG.16 illustrates the use of a symbiotic ncLwolk for number 25 portability;
FIG.17 illustrates the data of an ingress or egress process of a symbiotic network; and FIG. 18 illustrates the data of a controlled process of a symbiotic nclwolk.
Detailed Description FIG.1 shows the tre~tment of the call in the prior art and FIG. 2 shows the trea~men~ of the call in accordance with the principles of applicant's invention.
A symbiotic network acts as if it were a single switch such that all calls from any line or trunk connecte~l to the network to any other line or trunk connected to the 35 network is treated as if it were a call from a line or trunk connecte~l to a single switch to another line or trunk connected to the same switch. In such a network, it is .

CA 022~7667 1999-01-13 desirable to permit the switches connected to the incoming hrunk or originating line to have access to all information required for est~bli~hing a call, and to give the same access to the switch connscted to the outgoing h unk or terrnin~hng line. Lines and h unks are each terrnin~ed on a port of the switch.
5 ~ FIG. 1 is a block diagram illush ating call processing in the prior art.
Shown in FIG. 1 are three switching systems (switches), Sl, S2, and S3. Trunk group T12 connects switches S1 and S2, T23 connects S2 and S3, and T13 connects S 1 and S3. An incoming h unk 11 and origin~ting line 10 connected to S 1 are served by an onigin~ting process or an incQrning process. To clarify subsequent descriptions 10 herein, these are referred to as ingress processes. If an origin~ting or incoming call is recognized as being a call that terminates on switch S3, then an egress process is established in switch S 1 and is used to conhrol the call from the S 1 side of one of the trunks in trunk group T13. All three switches are connected to a data network 6,which is used to co~ nic~te sign~ling messages ~Iween the switches. When 15 switch S1 wishes to establish a call which terminates on switch S3, then switch Sl sends a data message to S3 identifying the trunk selected for that call and the terrnin~ting party of that call. Switch S3 then est~blishes an ingress process associated with the other end of the selecte~ trunk from trunk group T13. S3 treats this as an incoming call, S3 est~blishes a connection, for example to terrnin~ting line 20 30, and associates with that ter~nin~ting line an egress process for controlling the termin~ting end of the connection within S3.
A process is a block of memory used to store all inro~ ation necess~ry to control some part of a call and is also the softwar~ neceSs~.y for interpreting this information and for controlling the call acco,dingly. Systems such as the SESS~)25 switch, manufactured by AT&T Network Systems, have an ingress process and an egress process for all calls within a switch. The ingress process performing incoming or originating functions, and the egress process ~e.Ço,l"~ng terminating or outgoing processes. (As in-licaterl above, the term ingress and egress process may actually l~lesellt two difr l~int types of processes.) Lines and trunks are connected to ports of a switching system. Each ingress or process is ~soci~te~i with a port and controls call ~,ocessing for that port.
FIG. 1 also illustrates a call according to the principles of the prior arL
The call is to a group, such as a Centrex, whose lines are spread over three switching systems, Sl, S2, and S3. In accordance with the principles of the prior art, as 35 illustrated in FIG. 1, the call happens to be received in switch S 1, which may be closer to the originator of the call. Switch S 1 does not serve the tçrrnin~ting line CA 022~7667 1999-01-13 (30), nor does it have the information necess~ry to determine where line 30 is located. rnste~l) it has the information that switch S2 can be used to access, directly or indirectly, the lines of the termin~ting Centrex. Switch Sl therefore establishes a call to switch S2 and, essenti~lly, switch S l acts as a tandem switch in the 5 connection.
Switch S2 has a table inclicating the location of all the lines in the Centrex. When switch S2 receives the call, it consults this table and detell~~ines that the desired terrnin~ting line is line 30 located on switch S3. Switch S2 therefore establishes a connection to switch S3. Again, switch S2 acts as a tandem switch. In lO this case, switch Sl and switch S2, each acting as a tandem switch, each have control of the call using an incoming process and an outgoing process.
Finally, when the call reaches switch S3, the latter receives a call from an incoming trunk (incoming from switch S2) and the call is ~lestinçA for line 30 on switch S3. From the point of view of switch S3, the,~,rol~, this is an incoming call l 5 and is controlled by an incorning process associated with the incoming trunk and a terrnin~ting process associated with the called line 30.
Note the characteristics of this arrangement for switching calls. Each switch depends upon its own data base and its own status information, indicatingwhich lines and which trunks are available and which ones are busy, and each switch 20 has full control of calls set up in that switch.
FIG. 2 similar in general format to FIG. l, illustrates the differences between switches Sl, S2, and S3 acting as independent switches and switches Sl, S2 and S3 acting together as a symbiotic network. The ~wi~ches are connected by co.. ~ ation link groups Cl3, Cl2, and C23. The co.......... ~ iC~tion links in these 25 groups being totally under the control of the switches in the symbiotic nelwoll~ can be simplified to provide only the most rudi.--e-.t;.. y co.. ~-ic~tion signal tr~ncmicsion functions. For the p.ll~ose of this desc,i~lion, the term "switch" means a stand-alone switching system with an internal Stored Program Control Processorand a co-.. ~i-iration nclwol~ for intcr;olmecting lines served by the switch, trunks 30 served by the switch, and co...n~ isation links to other switches of a symbiotic network. A connection ~I~.~,en incoming trunk l l and terminating line 30 has only l ingress process in switch l one egress process in switch 3. The egress process in switch l and the ingress process in switch 3 have been replaced by controlled processes. Each end of a co.. ~ tion path within the symbiotic n~,lwolk 5 is 35 associated with a controlled process which contains only the most nl~iment~ryinformation required to keep up the con~ ullication path. The ingress and egress , . ~ . ... ~

CA 022~7667 1999-01-13 processes perform all control functions for the call and cause the controlled processes to be established or termin~te~ as l~uil~d. A supplementary process isstill associated with a connections to intelligent peripheral IP 24. The controlled processes are only for controlling the two ends of the intra-symbiotic network S cul-llllunication paths.
Contrast the process of establi~hing calls in the arrangement of FIG. 1 with the process using the arrangement of FIG. 2, in which the call is set up inaccordance with the principles of applicant's invention.
The ~witcl es of FIG. 1 and FIG. 2 are all program controlled switches.
10 This is shown in switch S3 of FIG. 2 which contains a processor 33, which in turn includes a memory 34. The memory contains a program for controlling operations of the switch, contains data about the ports and the routing for the switch, andcontains dynamic data such as the processes. The line segmçnt of FIG. 2 between the process and the line or trunk ~ sents the control exercised by the process, 15 acting under the control of the program, on the line or trunk.
An origin~ting or incorning process is ~igned to control one end of a call in a symbiotic network, and a terminating or outgoing process is a~igned tocontrol the other end of a symbiotic r.elw~,lk connection. The processes are entirely analogous to colnp~able processes within a single switch in the prior art. As will be 20 explained further, these p~ucesscs p~,lrO~ the same functions in a symbiotic n~lwolk as their counterparts ~1lll in a single switch except that the way in which they ~.Çoll.- these functions requires data message access to send control messages, data request messages, and data response m~ssages among the individual switches of the symbiotic ne~w~
The call is also received in switch S 1. However, switch S 1 instead of simply passing the call on to switch 2, makes an inquiry of switch S2 to ~et~rmine where the call is to be termin~tçd Switch S1 has previously determined from its own data base that the terminating number is the number of a Centrex whose descriptive table is to be found in switch S2. In l~i;,yonse to the info.l..alion obtained 30 from switch S2, switch S 1 now knows that the call is to be terminated on a line in switch S3. Switch Sl, under the control of the incorning process of the call, then checks switch S3 to dete.l..ine the equipment location of the tçrmin~ting line and to detelll~ e whether that line is busy. A "busy" test in this case includes a check of whether the line has call waiting service; a line with call waiting service is not 35 considered busy unless the line already has a waiting call. If the line is not busy, switch S 1 co-"-"~n-l~, via the same or a subsequent signaling message~ that the line CA 022~7667 1999-01-13 9 _ should be seized and marked busy so that no intervening calls are completed to that line. Switch S 1 then controls the process of selecting facilities for interconnecting switch S1 and switch S3. If co....,-~.nication paths are available between switch Sl and switch S3, then one of these co.. ~ iration paths is seized and switch Sl orders 5 that a connection be established within switch S 1 between the incoming trunk and the commllnication path and in switch S3 between the co.. l.~-ication path and the terminating line. Alternatively, a path can be reserved until the termin~ting station answers in response to a ringing signal, thereafter, the reserved path is established.
If no co....~ nication path is available bet~een switch S 1 and switch S3 because all 10 such paths are busy, switch S 1 searches for possibilities of establishing a connection to switch S3 via another switch. In this case, switch S 1 has available access to switch S2 via a co..... n-~nic~tion path and queries switch S3 for information as to the availability of a con.. ..~nicatiQn path connecting switches S3 and S2. (Suchil~ll,aLion may have been returned earlier from switch S3, e.g., along with the 15 response that the called line 30 is available.) Switch S 1 then sends a co. n...~nA to switch S2 to est~bli~h an unlllonitol~,d connection between a co---n~niC~tiQn path in C12 joining switches Sl and S2, and a c~.. lnic~tion path in C23 into connecting switch S2 and switch S3. This connection in switch S2 is under the control only of the process ~soci~t~d with the incoming trunk in switch S 1 and the ter~nin~ting line 20 in switch S3 and is disconnecteA only in response to a request from one of these pr~cesses. (This is the normal con~ inn; in addition, audit programs and craft requests may also take down the connection in case of trouble.) Switch Sl then l~ue~ls switch S3 (either through a direct request or through a request made to the t~rmin~ting process which has been activated in switch 25 S3 following the busy test of line 30 and the recognition that this line is available and should be seized for the call requested by the incoming process from switch S 1) to cooperate in establishing the path. The termin~tin~ process rnonitors for answer and tr~nsmit~ an answer message to the incoming process in switch S 1. Switch S3detects a called party disconnect, and passes a mess~ ~e to switch S 1 and responds to 30 a calling party disconnect mess~ge from switch S 1 by disconnecting line 30. The ingress and egress plvcesses co.~ ica~e via a virtual channel 52 set up between these processes and tr~nsmined over data network 6.
One of the advantages of a symbiotic n~,Lwolk is that the size of the trunk groups, connecting the symbiotic network with the rest of the public switched 35 telephone network, can be made much larger. Effectively, all outgoing trunks from the symbiotic network to another destin~tion, and one such destination may be a CA 022~7667 1999-01-13 complete symbiodc n~,lwo.k comprising a plurality of switches, can be combined into a single trunk group for trunk hunting purposes. Similarly, all the incoming trunks from a single source, and one such source may be a complete symbiotic network, can form a single trunk group for trunk hunting purposes; since the S ~lestin~tion switch of any outgoing trunk must be known to the signaling system of the source switch of what is an incoming trunk to the symbiotic network, the source switch must know the destin~tion switch of each such outgoing trunk within the group, unless a single sign~ling recipient forwards ~i n~ling messages to the right switch within the symbiotic network based on the trunk address. In FIG. 2, switch 10 S4 outside the symbiotic n~_lwolk 5, is connected to outgoing trunks 14 and 31 from switches S 1 and S3, ~s~cli-~ely, trunks 14 and 31 being part of a single group 51 for trunk hunting pul~oses. Similarly, incoming trunks 11 and 32 are connected from switch S4 to ~wilches S 1 and S3 ~spccli~ely and these two trunks are part of a single group 41 for trunk hunting pul~Joses in switch S4.
~;IG. 2 shows the ~witches of the symbiotic nclw~"k inte.connecte~ by a data network 6 for the ~ ose of exchanging data and control meSs~ges~ This generalized network may have a plurality of ~leAiratecl links and/or a ~le~1icatçA
sub~wil~h for h~n~lling the greater volume of meSsage traffic among the ~witchcs.
The ingress and egress processes of a symbiotic n~lwulk connection conveniently 20 co.. ~ icate over the data nelwull~ using a virtual channel.
The above example illustrates a number of the principles used by applicant in this embo~iment to treat all calls served by the symbiotic network as if the calls were served within a single switch. If info~ alion is not available in a switch, but is available in another switch, the normal process is to send a request for 25 the information to the second switch in accordance with applicant's invention. A
query is made by a col~ on channel sign~ling message and the controlling processthereby obtains the information which it would otherwise obtain directly within the switch if the symbiotic r~elwolk were a single switch. Further, a single originating or incoming process and a single terminating or outgoing process is used to control the 30 call instead of having control relayed through a group of incoming and outgoing processes. Third, the co~ a~ion channels inle~onneGting the switches of the symbiotic network are simple paths and do not require the normal sign~ling of information that is required for controlling tandem calls. That sign~ling need only be exchanged bel~en the switch that contains the origin~ ing or incoming process35 and the switch that contains the outgoing or termin~ting process.

CA 022~7667 1999-01-13 For certain calls it may be necessary to lempol~ily connect a unit such as Intelligent P~liphelal 24 (IP 24) to a call in order to collect information from a caller or called party. One such intelligent peripheral is a speech recognition unit which in response to p~ s to a caller, receives speech information from the caller 5 an converts this speech into data possibly for tr~n~mi~sion by data messages to another switch for controlling a connection. Since intelligent peripherals are relatively e~ nsi~e, they may not be connected to every switch of a nclwolk especially if, as in the case of speech lc;cog~ ion units, a con~mon control is used for a plurality of individual speech recognition units. If such an intelligent peripheral 10 has to be conllfclccl to a call, then a separate connection to that intelligçnt peripheral is established in this case over one of the trunks of trunk group T12. The connection is under the control of the original ingress process and egress process in switch S 1 connected to one side of the selected trunk in trunk group T12. An ingress process in switch S2 connectecl to the other side of that trunk and a supple ..- ~ y process in 15 S2 for controlling the intelligent peripheral IP 24. Note that in this as in other cases, an ingress process and an egress process or an ingress process and a supple-ment~ry process are associated with every connection within a switching system.
Suppose that prior to est~b!iching the call it was necess~ry tO provide the caller with an annou~-ce~..e~n and to recognize speech col..u.~n-ls by the caller.
20 Suppose, further, that the pr~ g e l~lip,n~ nt and speech recognition e luip~ ,nt were sufficiently expensive that it was not available in switch 1. In the prior art (FIG. 1), the call would be con~-e~l~l via a switch, such as for example switch 2, which has available such e~ui~ lllcnt. In accordance with the principles of applicant's invention, this is not necess~ n~tea~l, a connection is set up between 25 switch S1 and switch S2 for the duration of the time l~,qUil~id to p~Çollll the prolll~ts and recognize the spoken co...n-~n~s by the caller. This act would be under the control of an auxiliary process in switch S2 and after the comm~n-l~ had been recognized, switch S2 would send a message over the co~ oll channel sign~ling network indicating what co.lJIl.alld had been supplied by the caller. This is the 30 equivalent of setting up a connection within switch S 1 to such c~luipllle.~t (which does not exist in this case) and having the auxiliary process which controls thespeech processing equipme. t col.. ~-ic~e within switch S1 to the controlling incoming or origin~ting process. When the speech processing e.lui~ nt is no longer needed on this call, the co....n~)nica~ion path between switch Sl and switch S2 35 can be released, as can the connections in switch S 1 and switch S2 to that communic~ion path to allow the caller to be connected to the speech processing CA 022~7667 1999-01-13 e-luip.llellt. As discussed hereinafter, the Intelligent P~,.iphel~l may be connected to a switch or a symbiotic network outside this symbiotic net-work. The ingress process and supplementary process co.. ~ r~te via a virtual channel set up ~een these processes and tr~nsmitted over data network 6.
In some cases, the switches of a symbiotic n~lwu,L may be in fairly close geographic proximity. It is then possible and desirable to provide em~lgency linkages among the ~witches to provide, for example, a back-up clock from one switch to another. Similarly, back-up data links may be provided through the use of the data links of another switch. Emergency access to E911 C.ll~lgcl cy service can 10 be routed through an ~Ite~n~e switch of the symbiotic n~lwu,L.
FIG. 3 illustrates broadly how a symbiotic n~,lwo,k operates. Action block 200 shows that a call is received on an incoming trunk. Test 202 is used to determine whether the call is tandem for this symbiotic nctwu,~, i.e., whether the destin~tion specified on the call received on the incoming trunk is a destin~ion15 connected to a switch outside the symbiotic network. If the result of test 202 in~liç~tes that this is not a tandem call, i.e., that the call can be terrnin~te~ within the symbiotic network then translation data is açcesse~ for the ter~nin~ting number (action block 204). This type of data access is further described with respect to FIG.
4. Next, the line ~soci~te~l with the terrnin~ting number is tested for busy including 20 the check for call waiting service in which case "busy" means "busy" and one call waiting (test 206). The busy test is another example of the general type of dataaccess used within a symbiotic nelwolk. If the line is not busy then a connection is established to the called customer (action block 210). The connecLion may be direct or may be reserved in the case of call waiting. This type of connection is described 25 with respect to FIG. 6. If the line is busy and the busy tone is returned (action block 208) in this case directly from the switching system conne~,Led to the incoming trunk.
The process of obtaining tr~n~l~tion info~mation for the te~rnin~ting number may include a hunt for an available line in a multi-line hunt group, as described with respect to FIG. 9. In this case, the translation info"l.ation includes 30 data for the selected available line (or a busy in~ tion if no lines are available).
If this is a tandem call then a hunt for an outgûing trunk is p~lro med (action block 212). As will be described with respect to FIG. 8, this hunt can include any outgoing trunk in the symbiotic network. Finally a connection is establishedbetween the incoming trunk and the outgoing trunk (action block 214). This 35 connection establi~hm~n~ process is described with respect to FIG. 8.

CA 022~7667 1999-01-13 FlGs. 4-9 are flow diagrams illustrating how symbiotic network functions, comy~able to simple inL.aswilch functions in the prior art, are carried out.
FIG. 4 illustrates a simple data access subroutine. The subroutine starts with the generation of a data access request (action block 300). The identity of the S switch that contains the requested data is then det~ Lined (action block 302). In the symbiotic ne~wolll. it is necessAry that each switch cor-tAin~ the info....~l;onnecessary to determine directly or indirectly which switch has the needed data. For example if the data access request is a busy test, then each switch must containinfolmdlion inAic~ting which switch serves the terminAl~ of each direclul~ number or 10 it must contain inrolllla~iOn identifying another switch or data base that contAins that informAtion in a particular case. (If the latter is true then the determination of the switch effectively is another subroutine similar to the subroutine of FIG. 4 forAccessing data.) Once the switch has been deterFnined, test 304 is used to identify whether the switch contAining the reque~led data is the same as the switch which15 generated the data access request. If so, the data is açcesse~l in accordance with the principles of the prior art and the data access subroutine returns to the requesting program. If the identified switch is not the switch that ge.lcla~ed the data access request, then a data request mess~e is tr~n~mitte~ to the identifie~l switch (action block 310). This data message cont~inS the identity of the requesting switch, some 20 link such a request number to allow a return mess~e to be associated with therequesting data subroutine, and the identity of the switch requesting the data. The switch receiving the data request mess~ge, ~.rOlll-s the program whose flowchart is shown in FIG. S and returns a mess~e which is received by the requesting switch (action block 312). Once the response meSs~ge is received, the data requesting 25 subroutine may return to the data requesting program.
While in the plcifc~l~d embo liment, a particular seg..~- -t of office data is generally stored in one switch and accessed thererlul.l by other switches, it is also possible to replicate such data to reduce the number of inte~witch data access operations. This would be desirable if interswitch data access were relatively slow 30 and the extra lllc.l-ol y relatively inexpensive. Dynamic data, such as call processing data, cannot generally be replicated because of the high cost of the resources required to continuously update such replicated data.
FIG. 5 illustrates what happens when a switch receives a data request mess~e (action block 400), ~cesses the requested data (action block 402), and 35 tr~nsmit~ the requested data to the requesting switch (action block 404). In the return message is an identification, previously discussed, to associate the return CA 022~7667 1999-01-13 message with the requesting subroutine.
F M.6 illustrates the general process of establishing a connection within the symbiotic network. The program is started when a request is generated to connect an ingress port and an egress port (action block 500). An ingress port is 5 connected either to an origin~ting line or to an incoming trunk. An egress port is connected either to a terminating line or an outgoing trunk. Test 502is then used to determine whether the ingress port and the egress port are on the same switch. If so, then an intraswitch connection is established (action block 504) in the conventional manner of the prior art. If the ingress and the egress port are not on the same switch, 10 a path is selected between the ingress and the egress port (action block 506, further exp~n~e~ in FIG.7). After the path has been selc.,tcd, a controlled process is established for each end of each co.. ,~ a~ion link of the path (action block 508) and the controlled pl ccsses are linked to the ingress and egress processes (action block 510). Next, conn~ctions in each intslTneAi~te switch of the connection are15 established if necessary (action block 512). Such a conn~ction is necessary if the path inclu(les not only an ingress switch (connPcted to the ingress port) and an egress switch (connected to egress port) but also inchlcles an intçnn~Ai~te switch. Finally action block 514 is used to establish connections in the ingress switch ~I..een the ingress port and the port connsctçd to the ingress switch controlled process, and in 20 the egress switch bel~een the egress port and the co..~ ication link associated with the controlled process in the egress switch.
FIG. 7 illustrates the process of selecting a path. Block 600inAic~tes that a path is to be selected ~l~,en an ingress port and an egress port (or betwee ingress port and a supple .-- nt~ ~ y port, such as an intelligent peripheral, associated 25 with a supple.~f nl;~y process). Test 602is used to dete u~ine whether any co... ~ ntion links t~L~.een the ingress switch and the egress switch are available.
If so, one of the available commullication links is selected for this path (action block 604). If no co~ ;c~tion links are available bcL~.cen the ingress and egress switches, then co.~ ation link availability data is requested for links beL~e~.
30 intermeAi~ts ~wilchcs and the far switch. (For the purposes of this flow chart the near switch is the one requesting that a path be selected ) This co.. -,-;~tion link availability data is then cou-p~d with co-.. ~ ation link availability data of the near switch (action block 608) and a pair of available co-~ -ic~tion links to common inle..-.~ te switch is selected (action block 610). This procedure is very 35 similar to the procedure described for real time n~lwu,k routing in U.S. Patent 5,101,451; the symbiotic network is of course likely to be much simpler than a toll CA 022~7667 1999-01-13 network so that access information to relatively few inte~neAi~te switches will have to be examined.
In the unusual case where there are no two-link paths available between the ingress and the egress switch, a link may be selected to an inte~neAi~te switch 5 having two link paths available to the far end switch and, using that switch as a near end switch, the actions of blocks 606, 608 and 610 can be executed.
One of the advantages of the symbiotic network is that outgoing trunks for the network may be efficiently shared among all the switches of the symbiotic network. FIG. 8 illustrates the process of selecting an outgoing trunk from the 10 symbiotic ne~wulL. According to principles of the prior art, the first step in selecting an outgoing trunk is to find a route index for routing a call to a destination. A route index is well known in the prior art and is described for example in W. Ulrich, et. al:
"Tr~nsl~tion~ In The No. 1 Electronic Switching System", Bell System Technical Journal, pp. 2542-5, Septe.llbel 1964. Such a route index 15 provides an identification of a trunk group and the identific~tion of an alternate route index if that trunk group is not available. By stringing together route indexes, a highly flexible routing arrangement may be implP ~ te~ While not all switching ne~wolLs use the exact format of a route index, so~ P colllpd~dble is needed in order to have the flexible roudng arrangement. As a first step for routing an 20 outgoing call, it is necesC~Ty to dete- ..~ e a route index for the outgoing route. The trunk group of the route index is selected (action block 704). Action block 706 is used to identify the switch for selectin~ a trunk from the selected trunk group. For ease of selecting a trunk in a trunk group, a single switch is used for making this selection. This single switch m~int~in~ a record of which trunks are available in 25 order to be able to make a selection. The request to select a trunk from the selected trunk group is then sent to the i~l~ntified switch (action block 708). Test 710 is then used to dele~ ine if any trunks are available in the selecteA trunk group. If not, test 712 is used to dete ~;ne whether there is a next route index or simply a route index in~ir~ting no more trunks available and perhaps describing the blockage tre~tment.
30 If no more trunks are available, then blockage is reported to the requesting switch (action block 714). If there is a next route index, then action block 716 is used to select a trunk group of the next route index and the action bock 706 is ~e.-te.~id.
If trunks are available in a selected trunk group as indicated by a positive result in test 710, then test 720 is used to determine whether any trunks in 35 that group are available in the requesting switch. If so, then a trunk in the requesting switch is selected (action block 722), the selected trunk is marked busy (action block CA 022~7667 1999-01-13 724), and the identity of the selected trunk is repo,led to the requesting switch (action block 726). If no trunks are available from the selected trunk group and the requesting switch, then any available trunk in the selected group is selected (action block 730) and the actions previously described of action block 724 and 726 are 5 executed.
The trunks of a single trunk group can go to a plurality of different switches of a destination symbiotic network, since the traffic from any trunk can be readily switched to any terminating line of that network.
FIG. 9 is a flow diagram illustrating the process of selecting an egress 10 port for a call to a multi-line hunting group (action block 800). Such a multi-line hunting group might be for example a group of agents of an automatic all distributor that served calls to a particular telephone number. First the identity of the switch for selecting an egress port for that multi-line hunting group must be dett~rrnine~l (action block 801). A single switch is used for selecting the egress port for essentially the 15 same reasons that a single switch is used for selecting a trunk in a trunk group as discussed above with respect to FIG. 8. The request to select the egress port istr~nsmitte l to the i~Jentified switch (action block 802). The identified switchresponds with the identity of the egress port and the identity of the switch to which that egress port is connecte~l (action block 804) An egress process is then established 20 with the egress port in the switch of that egress port (action block 806) and the ingress and egress process are linked (action block 808).
An example of the usefulness of a symbiotic network is a distributed key telephone system having stations connecte~ to a plurality of the ~wilches of the symbiotic n~,lwo,k (E;IG. 10). Each key telephone station has a display for in~ ating 25 the status (busy, idle, ringing, hold) of certain other stations, and indicadons of incoming calls. The key stations also have buttons or keys to allow a stadon to pickup an incoming call, join a conversation, disconnect from a call or place a call on hold. In a modern key telephone system, the stadon has a single co,...".-l-ic~tion path to its connecte~ switch, and a two way data link to receive signals for 30 controlling its display, and to transmit signals representing the operation or release of the keys or buttons. The objective is to allow a station to pickup calls on any of a small plurality of equivalent line appearances, and to monitor the status of these line appearances. Thus, for example, a secleta y may monitor the telephones of one ormore principals, and answer calls when the principals do not do so. Autonomous 35 key telephone systems are expensive but the equivalent of key telephone service can be provided from a switching system, and, in accordance with the principles of this applicant's invention, from a symbiotic network. When all stations are idle, no processes are required. However, when an incoming call for any station of the key telephone system is received or when any of the key telephone system stations originates a call, processes are established for each key telephone station. These 5 processes control tr~ncmicsion of display control signals to their associated key telephone station and receive in~ atiQnc of the op~ ~ion or release of buttons or keys from their associated station. Each station control process co....--..nic~tes with the control processes of the other stations in order to update the displays of these other stations in response to operations or release of push buttons or keys by its 10 associated key telephone station. When an incoming call is received, all stations receive the display control signals and selecte~ station(s) receive in a~ ition a ringing signal. When any station answers the inComing call, a symbiotic network connection is established from the incoming trunk to that station, and the displays of other stations are updated. If another station also picks up, a confel~,nce connection 15 is established between the incoming trunk and the two stations.
In an ~ltern~tive embo~liment, a path is established to a lead station as soon as the call is received, which path stays up during the ringing interval. If another station answers, the call is then l~ .,t~,d to that other station. In one arT~ngem~nt, the lead station is the one that ans-.~r~d the most recent call.
Each key telephone stadon has its outgoing signals ~etected in the connected switch, and these signals are tr~nsmin~A as m~ss~gss to the control processes for each station of the key telephone systern for tr~ncmission to the associated key station. Similarly, incQming call requests have their cc,ll~s~onding lamp control mess~ges sent to these control processes.
FIG. 11 is a flow diagrarn illustrating the processing of a key telephone system call. An incoming call for the key telephone system is received (action block 900). The ingress process is acsigne~l to the incoming trunk and under the control of this ingress process incoming call data is tr~ncmitt~d to the processes controlling the a~pro~iate stations of the key telephone system (action block 902). Translation 30 inforrnation stored for the key telephone system in one or more of the switches of the symbiotic network is ~cesse~l in order to identify which key telephone stations are to receive calls for the called number. The processes associated with these key telephone stations are either established and made active or are already active since key telephone stations are informed of calls answered by other stations. These 35 processes then transmit to their associated key telephone stations, display control messages for inrlic~ting to these stations that an incorning call has been received CA 022~7667 1999-01-13 (action block 904). In some cases the message will be not only a display controlmess~ge, but also a message to cause an alerting signal to be generated at the key telephone station. When one of the key telephone stations subsequently answers the call, that key telephone station sends a message to the switch to which it is connected 5 and this message is routed to the control process for that key telephone station (action block 906). This process then becol.les an egress process for this call and in co~p~,~alion with the ingress process associated with the incoming trunk causes a connection to be established between the incoming trunk and the answering station of the key telcl,hone system (action block 908). The answer data is tr~ncmitte~ to 10 the processes controlling the other stations of the key telephone system which need to know about the answer (action block 910). These ~lucesses then transmit display control messages for the answer to the applupliate stations of the key telephonesystem (action block 912). The key telephone system can use analog telephones ordigital telephones such as Integrated Services Digital Network (ISDN) telephones.
A key telephone station of a key telephone system that is not connected to a switch of the symbiotic network may still be served basically by the symbiotic network. The distinction here is that when a connection is to be made, the connection must be made from a switch of the symbiotic network via a trunk to a switch of the key telephone switch, switch S4 in this case. The control of ~ign~ling 20 messages among the memh~rs of the key telephone system is otherwise the same.The translation data for the key telephone stations must identify the key telephone station attached to the outside switch. The ingress process in the symbiotic network and the egress process in the outside switch co.-....vnic~te directly via the si n~ling n~,twolk 6. Effectively, the key telephone station attached to switch S4 is part of a 25 virtual symbiotic network that includes the real symbiotic network 5. Virtual symbiotic ne~w~,lLs are ~ sse~l hereinafter with respect to FIGs. 13-15.
An enh~n~e~ path selection and connection routine must be used. The enh~ncem~ont is illustrated in FIG. 12 which shows that a request is generated to connect ingress port to a port outside the symbiotic network (action box 1000).
30 First, an outgoing trunk is selected for the connection to the port outside the network using the methods of selecting an outgoing trunk previously described (action box 1002). An egress process is established for the outgoing trunk (action box 1004) and a connection is established between the other end (an incoming end) of that trunk and the terrnin~ting port outside the network using conventional call setup 35 procedures (action box 1006). Also, a connection is established between the ingress port and the outgoing trunk (action box 1008). The informational and control CA 022~7667 1999-01-13 ~ign~ling for the key telephone station is carried out between the process for the key telephone station connecte~l outside the symbiotic r.~,lwolL and the other key telephone station processes in the sarne way as it is carried out when all key stations are in the symbiotic network.
Switch S4 establishes an egress process for controlling its connected key telephone station (action block 1010). The egress process on switch S4 and the ingress process conn~cted to the ingress port are then connected by a virtual signaling channel carried over data n~,lwol~ 6 (action block 1012). A connection is est~bli~he~l via an outgoing trunk from symbiotic netwolk 5 going directly or via the 10 public switched telephone network to switch S4, and a connection to the key telephone station is established in switch S4 (action block 1014).
As defined herein, a symbiotic r,~,lwolL comprises a group of swilches each of which can access data in any of the ~witches of the group. The swi~ches are connectç~l by co.. ~nication links and each switch has access to availability data of 15 these co..~ ication links. A single two-way trunk group or two one-way trunk groups can be used to interconnect two symbiotic netwolLs, since each such netwolL
acts essenti~lly as one switch; the individual trunks of the group can connect any of the switches of one symbiotic network with any of the switches of the other symbiotic network.
In some cases, it may be desirable to use more than one trunk group to connect a symbiotic network to a col~lon ~estin~tion. For example, a separate trunk group may be reserved for 911 traffic to ensure that e.llcrgency calls can be completed even if the public nelwolk is overloaded. A business may buy a trunk group to which its own traffic is restricted.
Many of the advantages of a symbiotic nelwolL are obtained in a virtual symbiotic network by providing virtual channels for co.~ ication between ingressand egress processes of conl-eclions to switches that are not in the same symbiotic network. For example, such a virtual channel can be used to control a key telephone station connected to a switch, or another symbiotic network, outside the original 30 symbiotic network. Effectively, in FIG. 10 all the key stations connected to switches S 1, S2 and S3 are part of symbiotic network 5. The key station connected to switch S4 is part of a virtual symbiotic network with the other key telephone stations.Virtual symbiotic nelwc,lLs are especially useful for serving the stations of a single customer, the station being scattered over several swilches, each of the several35 switches being used largely or primarily for serving other customers. Such a virtual symbiotic network is imple...e~-t~1 through translation data in each of the switches of CA 022~7667 1999-01-13 the virtual symbiotic network; this translation data in-licates that when a connection is set up between stations of the virtual symbiotic nelwvlk, a virtual channel is est~bliched bel~. een the control processes of the stations to allow data for enhanced call features to be exchanged. The translation information can indicate that a given 5 station is a member of more than one virtual symbiotic network.
Symbiotic netwvlk~ and virtual symbiotic nelwvlks are ideal vehicles for implem~nting Centrex type features whenever the stations of the sharing Centrex features are distributed over a plurality of switches. The facility of a virtual channel for signaling bel~,en ingress and egress processes on different switches allows the 10 data for the Centrex to be cc,~ only ~ccessec~ and exchanged bel~een these switches.
Foreign exchange service can be provided efficiently and at low cost using the &cilities of a symbiotic network or virtual symbiotic network. For exarnple, the foreign tennination is given a class of service which defines it as one 15 member of a virtual symbiodc network, the other ~ k l being the local termination. If the two termin~tions are part of a symbiotic or virtual symbiotic network, foreign exchange service can be provided even more easily since the terminals of the symbiotic nelwvlk operate as if they were on a con~lllon switch.
Symbiotic n~,twv,ks are a convenient way of locadng telephone 20 Op~,lalOl~ and their associated operator ~C~i~t~nce switches remotely from a centralized o~.ator ~ t~nce switch. The operator ~Csi~t~nce switches can be combined into one symbiodc network. Operators working from home or from scattered locadons can be combined into a virtual symbiodc netwul~ and derive many of the ~llefils of being in a single symbiodc network.
Specialized circuits such as IP 24 may be included in a virtual symbiotic network, for example, with the stadons sharing Centrex fea~es, or with the stadons of a symbiodc ne,lwolL so that larger groups of such circuits may be physically located, and controlled, together, and may share common resources; for example, many speech recognition front end circuits can share one bulk ll~llloly.
The switches of a large cellular teleco.l.. l-l~ tion~ network can be combined into a single symbiodc network. This simplifies the problem of "handingoff" traffic from one cellular mobile switch to another when the connected mobile moves from one area to another.
FIG. 13 illustrates a virtual symbiotic network. The network comprises 35 three switches S7, S8,...,S9 each connected to a plurality of telephone stations 101,...,102; 103,...,104; and 105,...,106; respecdvely. The switches are CA 022~7667 1999-01-13 inlerconnected by the public switched telephone network 100. Each switch may contain lines which are not part of the virtual symbiotic network. (Some of these lines may be part of another virtual symbiotic nelwulk.) When a connection is made between stations on the virtual symbiotic network (i.e., one of the stations S 101,...,102; 103,...,104; and 105,...,106,) an ingress process 110 is acsoci~ted with the origin~ting station and an egress process 111 is associated with the termin~tingstation. A virtual channel 120 is established between the ingress process and the egress process to permit these processes to exchange data and to access data in the switches in which each of these processes reside.
FIG. 14 illustrates some of the tr~nsl~ti-)n information that is required to implement a virtual symbiotic n~,~wo.L, in this case, for Centrex type service. The p~ translation entry for one of the stations on the symbiotic network, entry 1100, includes data for locating a supplemçnt~ry table 1101, and an identifiration of the virtual symbiotic network 1102. The data for locating may be a direct or indirect 15 address, or, especially if the table is located in another switch, a key for locating that table; the key may be tied to the identific~tion of the virtual symbiotic network.
Table 1110 is a table to translate between the access number (typically an abbreviated number dialed by a Centrex e~çn~iQn) and a convention~l telephone number 1112 for routing the call to the station specified by the access number 1111.
FIG. 15 illustrates the process of establishing a call in a virtual symbiotic n~,lwolL. The process of establishing a call begins when the origin~ting station lifts its receiver (acdon block 1200). The origin~ting office assigns an ingress process to the call (actdon block 1202). The station dials a virtual symbiotic network number (in this case, a Centrex number) (action block 1204). The translation data of 25 the origin~ting switch illustrated in FIG. 14 provides the virtual symbiodc network identification and an address of the virtual symbiodc nelwo L table (action block 1206). The virtual symbiodc nelwo-L table provides the telephone number ofthe desdnatdon (action block 1208). (A full telephone number is used to simplify the routing of the call.) The call is then established to the termin~ting switch but the 30 SS7 signaling m~Ss~ge used to establish the call includes a virtual symbiotic network in-liratQr and the idçr.t;r~calion of the virtual symbiotic r.elwo.L (actdon block 1210).
While the l -cfel~d embo limçnt uses SS7, altçrn~tive sign~ling arr~ngemçnt~ can be used instead. For example, a p~lictary message standard could be used in order to avoid mo lifi~ions of the standards governing SS7. The termin~ting office assigns 35 an egress process (action block 1212). A virtual channel is then established between the ingress process of the originating switch and the egress process of the CA 022~7667 1999-01-13 terrnin~fing switch (action block 1214). This allows these two switches to exchange all h~rol.llation necess~ry for implçmenting the specialized service. The connection in the terrnin~fing switch is established under the control of the egress process (action block 1216). The control and exchange of information between the ingress5 and egress processes can, for example, be used to reroute the call to another station of the virtual symbiotic network in another switch.
In an ~ltern~tive embodiment, a call setup request message can be sent to the ~ermin~ting switch (or a switch containing data for selecting an available member of a multi-line hunt group) in advance of establishing any connections so10 that a busy test can be performed and a line seized before a voice connection is established.
While in FIG. 10, the key telephone stations connected to swi~cht,s Sl, S2 and S3 are part of a symbiotic nclwul~, they can also form all or part of a virtual symbiotic network with the control ~,lucesses for each station cû.. ~nis~ting by15 virtual data ch~nnel.c and with the switches inlelcolme~Led as discussed for FIG. 13.
The key telephol1e stations in either event can be parlt of a larger custûm~r network such as a Centrex network.
FIG. 16 illustrates another application of symbiotic network for number portability. By number portability, in this case is meant the ability to switch a 20 customer station from one line termination associated with one location to another line termin~fion associated with a different location. In the specific embo~iim~ont shown in FIG. 16, a subscriber dials a request to register at the new location (action block 1300). Such a request should include in~olllla~ion to identify the subscriber's telephone number and privacy data such as a personal identifi~afiQn number to 25 ensure that an outside individual cannot effectively hltelee~t calls for that subscriber by taking on the di~clul y number of that subscriber. The receiving switch verifies the pC~OI al idenhfic~ion number from the data base for the subscriber or for the customer from which the subscriber is a memb~r and notifies the switch containing data for that subscriber (action block 1302). The switch then updates the data base 30 (action block 1304). The subscriber receives a verification annonncement (action block 1306) as a partial insurance against the misuse. An announcçmçnt is sent to the original location and is repeated periodically if no answer is received. (action block 1308). The attributes of the symbiotic network or a virtual symbiotic network including a port connected to the subscriber's new wall jack appea~dnce make the35 movement of subscribers relatively straightforward because the data for the subscribers is effectively shared among the switches of the symbiotic or virtual CA 022~7667 1999-01-13 symbiotic network.
A symbiotic network can be used to improve the reliability of service to specialized customers such as stockbrokers for whom loss of service can be devastating. First, the agents of the stockbroker can be distributed over a number of S switches of the symbiotic network. Protection is obtained against the loss of any of these switches since incoming calls to any switch can readily be completed to any other switch of the symbiotic network. Secondly, trunk groups from other switches may be connected to more than one switch of the symbiotic network, so that if one switch fails, traffic can flow through the other ~witches. Third, the individual agents 10 may be arranged to have key telephone stations connected to two switches with the connection to one of the two switches normally unused. Effectively, a symbiotic network is like one giant switch so that the failure of one of its switches is like the failure of only a sc~...ent of the giant switch.
FIGs. 17 and 18 show the partial contents of ingress and egress 15 processes and controlled plocesses ,~ ec~ ely. An ingress/egress processes (FIG.
17) includes the iclentific~tion of the port controlled by the process, i~1entific~tion of the port at the other end, of a connection (i.e., the idçntifir~tion of the terrnin~ting line of a line port or a trunk port connected to the syrnbiotic network, not at intra-symbiotic network port.) The ingress/egress process also inc~ ies links to other20 control processes, suppl~ ..e .~ plvcesses, and controlled processes. Also included is the called directory number, path information for the call, and data describing the characteristics of the trunk or line connected to the port. In contrast, a controlled process (FIG. 18) only cont~in~ the identity of the aCsoci~teA port and the portconnected by the switch of the controlled process to that port. While it may be 25 desirable to also have info.lllaLion, for reverse linkage in order to be able to notify the controlling ~iocesses, (i.e., the ingress and/or egress processes) of failures in network connec~,ons for the purposes of establishing and disconnecting calls thespecified data a~eals to be all that is nccess~ y The techniques rliccussed herein for the symbiotic network can be used 30 individually or in combination for a virtual symbiotic network. Some of the techniques can be applied to only a portion of the lines of a switch, such as the lines for a particular customer. For example, if a call involves a line of such a customer, the data access arrangel,~nts of FlGs. 4 and 5 can be used to access a master data base for the customer; the switch l~plesenting the data access must know the identity 35 of the switch that contains this master data base (which includes a table such as table 1110 of FIG. 14) and stores that identity in its data base. The use of combined trunk groups such as 41 and 51 can be used for private trunk groups inlclcolmecting switches of such a customer to provide greater diversity of facilities to protect against trouble or disaster conditions. The technique of an advance request for a busy test or an advance selection of an available line of multi-line hunt groups as 5 described in FIG. 9 can be used in such arrangemel1ls to avoid establishing unnecessary connections.
The technique of FIG. 7 can be used in conjunction with private trunks dedicated perm~nently or through a software defined network in~..;o-mecting switches of a virtual symbiotic network. Similarly, the techniques of FIG. 8 can be 10 used to select a private trunk ( le~ic~te~l perm~nen~ly or through a software defined network) interconnecting ~witches of a virtual symbiotic network.
In the prc~ d embodiment, the virtual ch~nnelc bel~een processes are channels on a pe.lll~ ent virtual channel be~.een the switches of these processes. In addition, the switches themselves use virtual channels over such permanent virtual 15 circuits to co.. ~ni~te bel~e~ the controls of these switches.
It is to be understood that the above description is only of one plcrel.~;d embo~im~nt of the invention. Nulllcl~ us other arrange.l,en~s may be devised by one skilled in the art without departing from the scope of the invention. The invention is thus limited only as defined in the accompanying claims.

. .

Claims (4)

Claims:

1. In a telecommunications network comprising a plurality of stand-alone switches, said plurality of stand-alone switches being interconnected by a data network for transmitting data messages among said plurality of stand-alone switches, a method of controlling a plurality of associated key telephone stations within a set of said plurality of stand-alone switches, said plurality of associated stations connected to a plurality of said switches, comprising the steps of:
grouping the set of said plurality of stand-alone switches into a symbiotic network;
responsive to receipt in a first of the set of said switches of a call on a line or an incoming trunk for ones of said plurality of associated stations, transmitting first display control data messages, over said data network, to second ones of the set of said switches connected to said ones of said stations, to control displays of said ones of said stations;
responsive to receipt of said first messages in said second ones of said switching systems, transmitting display control messages from said second ones of said switching systems to said ones of said stations;
responsive to receipt from one of said stations in any of the set of said switches of a message indicating a request to answer said call, transmitting, over said data network, a request to said first of said switches to establish a connection from said line or incoming trunk to said one of said stations; and establishing a connection from said incoming trunk to said one of said stations.

2. The method of claim 1:
wherein one additional key telephone station is connected to an additional switch, said additional switch being outside said symbiotic network;
wherein transmitting first display control data messages comprises transmitting first display control data messages to said additional switch;
wherein the step of transmitting display control messages comprises the step of transmitting display control messages from said additional switch to said one additional key telephone station;

wherein the step of transmitting a request to said first of said switches comprises:
responsive to receipt from said one additional station of a message indicating a request to answer said call, transmitting a request to said first of said switches to establish a connection from said incoming trunk or line to said additional switch and establishing a connection in said additional switch to said one additional key telephone station.

3. In a telecommunications network comprising a plurality of stand-alone switches, said plurality of stand-alone switches being interconnected by a data network for transmitting data messages among said plurality of stand-alone switches, a method of controlling a plurality of associated key telephone stations within a set of said plurality of stand-alone switches, said plurality of associated stations connected to a plurality of said switches, comprising the steps of:
grouping a set of ports comprising ports of said plurality of associated key telephone stations, into a virtual symbiotic network;
responsive to receipt in a first of said switches of a call on an incoming trunk or line for ones of said plurality of associated stations, transmitting first display control data messages over said data network to second ones of said switches connected to said ones of said stations to control displays of said ones of said stations;
responsive to receipt of said first messages in said second ones of said switching systems, transmitting display control messages from said second ones of said switching systems to said ones of said stations;
responsive to receipt from one of said stations in any of said switches of a message indicating a request to answer said call, transmitting over said data network, a request to said first of said switches to establish a connection from said incoming trunk or line to said one of said stations; and establishing a connection from said incoming trunk or line to said one of said stations.

4. A stand-alone telecommunications switch, connected to a plurality of other stand-alone switches by a data network for transmitting messages between said switch and said plurality of other switches, comprising:
processor means, responsive to receipt of a call on an incoming trunk or line for ones of a plurality of key telephone stations some of which are connected to other ones of said plurality of stand-alone switches, for controlling transmission over said data network of first control display data messages to ones of said plurality of other switches to control displays of ones of said stations;
further responsive to receipt over said data network from one of said plurality of other switches of a message indicating a request to answer said call, controlling an extension of a connection from said incoming trunk or line towardsaid one of said plurality of other switches; and further responsive to receipt of first control display data message from another switch of said plurality of other switches for controlling transmission of a display control message to ones of said key telephone stations connected to saidswitch, and responsive to an answer message from a key telephone station connected to said switch for controlling transmission over said data network of another message indicating a request to answer a call.