CA2036742C

CA2036742C - Broadband isdn packet switching arrangements

Info

Publication number: CA2036742C
Application number: CA002036742A
Authority: CA
Inventors: Ronald Anthony Spanke
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1990-03-30
Filing date: 1991-02-20
Publication date: 1996-07-30
Anticipated expiration: 2011-02-20
Also published as: CA2036742A1; EP0450818A3; JPH04225648A; ES2075344T3; DE69111657T2; EP0450818A2; EP0450818B1; US5115426A; ATE125998T1; JP2552037B2; DE69111657D1

Abstract

A broadband packet switch arrangement comprising a broadband packet unit connected to a plurality of customer lines and a video switch for selectively connecting packetized video signals from a plurality of video sources to the customer lines. The broadband packet switch unit selectively connects customer lines and transmits received control packets received from the customer lines to a control unit which responds to video request packets by controlling the video switch to connect selected video packets to the customer lines. Each customer line includes a selector circuit which receives video packets and inter-customer broadband ISDN
packets and merges them onto the customer line. After the control unit has granted permission to connect a video source to a customer line, video source change requests for the line are sent directly to the video switch which responds thereto by connecting a requested video source to the customer line.

Description

BROADBAND ISDN PACKET SWITCHING ARRANGEMENTS

Technical Field This invention relates to packet swiL~,hing sya~s for switching both video packets and non-video packets to packet service CllS10~ 1 le~ ~ over ~;uàlo~r 5 access lines.
Bach~;~ o~ d of the I~ ..ti~
The extensive use of ~lavnal cou~puLe~a and other data procescing f~"~ititiss at home and in the office gave rise to a need for voice and data ~nsmiccion and switching c~p~bilities on a wide spread basis. To satisfy this need, the 10 integrated services digital n tw~ (ISDN) providing ap~-u~i~ately 144 kilobits per second bandwidth was developed for use by telcco..l...lll-ic~tions subs~ibers. The conti luing grûwth of digital services and c~p~bilitiçs has now created a need for packet tr~ncmicsion and awitcl~ing ar~nge-~ which have the capaci~y for larger bandwidths. In lc~nse to this need for higher info~mation bandwidths, a new 15 capability known as bro~lb~nll ISDN (B-ISDN) is being developed to provide bandwidths on the order of 150 megabits per second.
The ~va~t of a 150 mçg~bit per second ch~nnçl to mllltilndes of resi-lenti~l and b~ ess ~ O~ a has caused system planners to seek new revenue g~ a~ing services which can use the band-width. One such desirable service is the 20 delivery of full motion video, e.g. television, to B-ISDN ~ O...~ ~ p~Pti7~d television signal delivery ~uil~,s a bandwidth of ap~ l-al~,ly 45 megabits per second which is well within the B-ISDN capacity, however television signals are not bursty like cûmputc~ data but are su~st~n*~lly co~ ous. Relatively few video channels can be plcsent~,d con*nllo-)cly to ~ o-. ~, a over a single 150 megabit per 25 second B-ISDN conn~l;Qn Video service can be p~vided to B-ISDN Cu~ne ~ by selectively COn.~'!;n~ one of many video sources to a single videû ch~nn~ conveyed to those . ;,. In this way a single 45 meg~bit per second video ch~nnçl on a B-ISDN
link can deliver m~ny dirre-~nl television ~ a to a euaLv~ one at a time. An30 alTangement is needed hu . ~ ,, to providc thc ncee~SA~ ~r selec~ive com1~;Lions . ~n the video sou~ces and B-ISDN videv ch~nnels on ~ ilo!n~ access lines.
In one packet switching arrangement, as described in the prior art, customer access lines are connected to a broadband packet network which providesselective packet connections among B-ISDN customers connected to the access lines.
This arrangement can be extended to provided selected video connections by attaching ~f ~' video sources as inputs to the same bro~lb~n-l packet nelwulL which provides bro~lb~nrl packet connr~l;on~ among the B-ISDN cln~lo...-- .. Although the use of the broadb~n~ packet network provides the ability to selectively connect packets5 from the video sources to CU~lULU~ access lines, it is ve;y inefficient.
Packet switching n lwu~Ls are ~esigne~ and their efficiency maximized for the selective connçctiorl of bursty data. Efficiency is achieved by sharing n~lwu,k c~a~iLy among users when some users have ilL~u,~ation to send and othersdo not. In the case of relatively conl;~uvus high bandwidth data such as video 10 signals nelwolL bandwidth is co..l;n-,ously used and is not available for sharing.
Accordingly, a si nifi~nt llu~ber of video ch~nnel~ through a br~db~n~ packet network can use up the network's capa~ y to l~ Lui~ other info,mdlion. The use of a packet n~lwo,k to switch both video and non-video packets ;esults in blocking by the packet n~,lwu~L of non-video p ~ t<, due to network capacity limits or in the use 15 of a packet ~witcliu~g n~,lwu,ll, with far greater capacity (and greater expense) than would be needed to effi~ently deliver the non-video packets among the customers.A need exists for a packet ~wilclilllg ~ng~m~ont which can efficiently colmcct packets among .;u.lv...~ ~ connc~ A ~o a plurality of ~U~lULU~,. access lines while at the same time selectively delivering bro~lh~n~ video packets to the 20 CU~IULU~ via the same C~>lv~ lines.
Summary of the ~vention This need is meet and a technical advance is achieved in accordance with the present invention in which a packet switching network, con~-e~-le~A to a plurality of ~ , by in~c,...;ng and outgoing lines, is used to provide selective 25 packet co~-ne~! ;onc among those CU~I~)LU~ and a video switch is used to selectively conn~l video signal l,a~,l~ from video sources to the ~ lOll h - ~> via the outgoing lines. The coo~ a~d use of separate video ~will,hcs and packet r..,lwolks permits g the efficien~y of each to the type of traffic it conveys, thereby improving the ~ cy and redu~in~ cost of the overall alT~ngem~nt The same C~S~ outgoing lines in the present invention convey both video packets from the video switch and customer packets from the packet switching n~,lwu,k. To avoid ~c~iEning too much traffic to a given .;uslo~r line, a singlecontrol unit which grants and denies ~.l~ ion to co.. lnic~te in response to service requests from cu~lullle.~, controls both the video switch and the packet35 network. Requests for service from C~ are received by the packet netwo.
and selectively connecte~l thereby to the control unit.

Each of the outgoing lines of the arrangement includes a selector circuit which receives both customer packets from the packet network and video packets from the video switch and selectively merges them onto the same outgoing line to a customer. Advantageously, the selector gives priority to video packets and transmits S video packets on the associated outgoing lines whenever they are present. In this way, the relatively continuous nature of video signals can be, ~ ed.
The service of providing full motion video to customers will be most popular, when customers can use the switched service the same way they use television today. An almost instantaneous ability to change channels is one desirable 10 feature of today's television. Rapid channel change is difficult to achieve in an arrangement where the channel change (video source selection) occurs at a telecull unication central office. At times, such as commercials, when many cu~ el~ substantially ~imlllt~neously change channels, the single control unit and the connection to it within the central office can be overloaded resulting in 15 significant channel change delays.
Advantageously, an embodiment is employed to avoid channel change delays. The embodiment includes a bandwidth allocation controller which records the bandwidth available to the customers and responds to initial set-up video request signals received from one of the customers by granting permission to connect a 20 video channel to that ;u~lolll~l. After permission is granted, channel changes are controlled by video source identity packets from the one customer which are sent to a video switch without any involvement by the bandwidth allocation controller. Avideo switch controller of the video switch responds to the video source identity packets by rapidly connecting the source identified in the packet to the customer via 25 the video switch. This embodiment uses the bandwidth allocation controller toallocate video bandwidth on the customer line and that bandwidth is thereafter used as directed by the customer in video source identity packets. Since the bandwidth required by one video channel is the same as is required by any other video channel, the customer can continue to rapidly change channels without being delayed by 30 consulting the bandwidth allocation controller.
A specific illustrative embodiment discloses a packet switching arrangement including a broadband packet switch connected to a plurality of customer access lines for selectively connecting customer packets between those lines and a video switch for selectively connecting video signal packets from a 35 plurality of video sources to the customer access lines. The broadband packet switch connects video service request packets received on one of the customer access lines to a bandwidth allocation controller which responds thereto by granting permission to the video switch for the connection of video signal packets to the one customer access line. Additionally, the broadband switch responds to video source request packets 5 received on the one customer access line and identifying one of the video sources by connecting the video source request packet to the video switch. The last named switch responds to the video source request packet and the previously generated permission from the bandwidth allocation controller by connecting video packets from the identified video source to the one customer access line.
According to one aspect of the invention there is provided a packet switching arrangement comprising: a packet switching network comprising a plurality of incoming lines for receiving customer packets from customers, a plurality of ongoing lines for conveying packetized information to said customers and means responsive to customer packets received on said incoming lines for selectively 15 connecting said received customer packets to said outgoing lines; a plurality of sources of video signal packets; video switch means for selectively connecting ones of said video signal packets to said outgoing lines without being transmitted through said packet switching network; and control means common to said packet switching network and said video switch means and responsive to control signals receivd from 20 said incoming lines for controlling the connections provided by said packet switching network and said video switch means.
Brief Description of the Drawin~
FIG.lis a block diagram of a switching system incorporating the present invention;
FIG. 2 is a block diagram of broadband switching module shown in FIG.l;
FIG.3 is a representation of broadband ISDN packet;
FIG.4is a block diagram of a broadband switch unit of FIG.2;
FIG. 5 is a representation of a broadband packet sent to the inputs of 30 the broadband packet switch of FIG.4;
FIGS.6 through 8 represent translation tables of information stored in the communication path circuits of FIG.4;
FIG.9is a block diagram of an interface unit of FIG.2;

20367~2 -4a-FIG. 10 is a block diagram of a broadband switching module equipped to provide video services;
FIG. 11 is a block diagram of broadband switch unit of the embodiment 5 shown in FIG. 10; and FIG. 12 shows a data buffer 64' of the communication path circuits of FIG. 11.
Det~iled Description FIG. 1 is a block diagram of a telecommunication system illustrating 10 the principles of the present invention. The illustrated system includes a plurality of switching modules 501, 1000 and 6000 which are each connected to two input/output ports Pl through P62 of a time-multiplex switch 10 via a pair of bi-directional time-multiplex lines comprising, for example, time-multiplex lines 13 through 16.
Time-multiplex switch 10 completes time-shared space division paths among the 15 switching modules 501, 1000 and 6000 under control of information stored in acontrol memory 29 to enable communication among the switching modules. Control inforrnation necessary to coordinate the operation of the switching 2~742 modules and the time-multiplex switch 10 is exchanged between the ~wilcl~ g modules and between the switching modules and a central control 30 via time-multiplex switch 10 and a control distribution unit 31.
Each of the switching modules is connected to a plurality of customer S lines and trunks, e.g., 23 and 24 and either inl~,.;olmects the lines and trunks connected thereto or cooperates with the central control 30 and other ~wilching modules to complete connections between customers of different switching modulesvia the time-multiplex switch 10. Switching module 501 is a circuit swilchillg module and is connected to, for example, analog telephone customers via lines 2310 and 24. Circuit switch module 501 performs analog to digital and digital to analog conversion, time slot interchange for digitized customer signals and coop~l~tes with central control 30 and the other ~wilcllillg modules for the connection of its CUSl(~
Narrowband ISDN switching module 1000 is connected to a plurality of 15 ISDN customers via n~lowband ISDN lines 1003 and 1004 and provides connections between the ISDN customers and other customers of the system of FIG. 1. Nallowballd switching module 1000 sepal~tes the B- and D-ISDN channels, provides packet switching connections for the D ch~nnel~ and circuit switch connections for the B channels using a time slot interchanger (not shown). A system 20 of the type shown in FIG. 1 compri~ing n~lvwt,and ISDN switching modules and circuit ~wilchillg modules is shown and described in detail in Beckner et al., U.S.
Patent No. 4,592,048 and is described herein only in so far as necessary to describe the operation of bro~lb~n-l switching module 6000 and its cooperation with the other units of FIG. 1.
Broadband switching module 6000, shown in greater detail in FM. 2, comprises a broadband switch unit 6001 which is connected to a plurality of B-ISDN
cu~omt;l~ over a plurality of bi-directional B-ISDN optical fibers 6115 and 6116.
Optical fibers 6115 and 6116 convey packets of digital information at the rate of 150 megabits per second where each packet (FIG. 3) comprises 48 bytes of customer 30 information and 5 bytes of header information. The header information includes certain packet overhead inrc,llllation such as error checks and the virtual channel identifier (VCI) of the packet. The VCI of a packet uniquely identifies, on a given comlllullication path, the coi--."...-ic~tion of which the packet is a part.
Although all packets on collu~lunication paths 6115 and 6116 are in the 35 B-ISDN format, they may be parts of different collllllunications and may be to or from non-B-ISDN cu~lolllel~. For example, a B-ISDN packet virtual channel may 2~3~742 be a high bandwidth, e.g., 20 megabits per second channel between two B-ISDN
users, it may be a low bandwidth, e.g., 64 kilobits per second channel between B-ISDN users or it may be a 64 kilobits per second channel between a B-ISDN user and a narrowband ISDN telephone set on narrowband switch module 1000.
5 Broadband switch module 6000 responds to the VCIs of the packets it receives to interconnect the users of the idçntified virtual channel.
Bro~-lb~n-l switch unit 6001 of broadb:3nd switch module 6000 is connected to customer co. . -- ~ ic~tion paths 6115 and 6116, as well as to a bi-directional cc,- -~ tion path 6114 connected to an interface 6100. Broadband 10 switch unit 6001 responds to the VCI of each packet received on a co.-~ l--ic~tion path by connecting the received packet to a predetermined one or more of the outgoing optical fiber co-~ C~tion paths 6114 through 6116. The predeterminedoutput for most VCIs is selectively changed from time-to-time by a control arrangement which is discussed in more detail later herein. When the outgoing 15 co-~---ll--ication path is connected to a customer fiber, e.g., 6115 the packet is sent to the customer connected to that fiber in the same form that it was received, i.e., FIG. 3. The predetermined output for packets having certain VCIs is cc"--- I lll l~ ication path 6114 which is connected to the interface unit 6100. Fiber 6114 and the interface unit 6100 receive all B-ISDN packets conlailling system control 20 information and all B-ISDN packets which are to be connected to non-B-ISDN
customers such as customers connected to nallowl,alld switching module 1000 or circuit switch module 501.
Tntçrface unit 6100, which is described later herein, receives packets on co.-""l-i-ication line 6114 and places them in buffer storage for transmission in 25 selected time slots on selected ones of a plurality of bi-directional time-multiplex lines 1201 and 1202. Tran~mi~sion on time-multiplex lines 1201 and 1202 takes place at the rate of 64 kilobits per second. The particular time slot and time-multiplex line for a packet received from con~..-.-.-ication path 6114 is selected by interface unit 6100 in response to the VCI of the received packet. Lines 1201 are 30 connected to a time slot interchange unit 6011 and lines 1202 are connected to a packet switch unit 6400. Interface unit 6100 also receives information from the time slots on time-multiplex lines 1201 and 1202, and buffers the information until an entire B-ISDN packet is receivçd. Upon receipt of an entire packet from a given time-multiplex line, time slot interface unit 6100 affixes a preselected VCI to the 35 packet and transmits the packet to bro~dband switch unit 6001 via comlllunication path 6114.

203674~

Time slot interchange unit 6011 receives time slots of information on time-multiplex lines 1201 and selectively connects those time slots to the time slots of time-multiplex lines 6013 and 6014 for connection to the time-multiplex switch 10. Time-multiplex switch 10 connects the time slots to other ~wilchillg modules, S e.g., 1000 and 501. Similarly, inrolll~tion from other switching modules is selectively connected from time-multiplex switch 10 to time slot interchange unit 6011 in the time slots of time-multiplex lines 6015 and 6016.
Packet switch unit 6400 acc~lmlll~tes the packets from interface unit 6100 and provides narrowband packet ~witching among the time-multiplex lines 10 1202. Information ~tul-~ing to the interface unit 6100 from packet switch unit 6400 is accllmnl~ted into B-ISDN packets, provided with a preselected VCI and tr~n~mit~ed to broadband packet switch unit 6001 via con~ ul.ication path 6114.
Broadband switching module 6000 includes a control unit 6017 which operates in conjunction with central control 30 and the control units (not shown) of 15 other switching modules, e.g., 501 and 1000 to control the broadband switch unit 6001, the interface unit 6100, the time slot interchange unit 6011 and the packet switch unit 6400. In addition to control information received from central control 30 and the other switching mod~1lçs~ control information is received and tr~n~mitted by control unit 6017 from and to the customer co,~ ication paths, e.g., 6115 via the 20 packet switch unit 6400, the interface unit 6100 and the bro~db~n-1 switch unit 6001.
Control unit 6017 exercises control of the units within swilching module 6000 over conductor 6027.
Certain of the available VCIs on the B-ISDN co--...~ ication paths, e.g. 6115, are preassigned for specific purposes. For example VCI 1, which is 25 referred to as a layer management channel, is used by B-ISDN cus~c,m~ls to send and receive control ~lrolmation such as call set-up information to and from broadband switch module 6000. Bro~lh~nd switch unit 6001 recognizes each packet with VCI
1 and connects that packet to interface unit 6100 via cc,mlllullication path 6114 using a virtual channel identity which is preassigned for the exchange of control 30 information between the particular incoming co-- ...~ ication path, e.g., 6115 and interface unit 6100.
FIG.4 is a more detailed representation of broadband switch unit 6001 which comprises a broadband packet switch 6002, a controller 6006, a col ",u"~- ication path circuit, 6003 and 6004 for each colllll~unication path 6115 and 35 6116, respectively, and a cc " -l ~ l- ic~tion path circuit 6005 for collllllunication path 6114. Colllmullication path circuits 6004 and 6005 are substantially identical to 203674~

collllllunication path circuit 6003, which is shown in detail in FIG. 4. Each col~ lunication path circuit receives packets from a B-ISDN line, e.g., 6116 andbuffers them in a buffer 61. A tran~mitter 62 reads a packet from buffer 61 and,responsive to the received VCI, reads a new VCI and physical routing header from5 translation table 63 in preparation for sending the packet to broadband packet switch 6002. The tr~n~mitter 62 replaces the incoming packet VCI with the new VCI, appends the physical routing header to the packet and transmits the packet and physical routing header to the bro~dband switch network 6002. A packet, as tran~mitted to bro~lh~n-l packet switch 6002, is shown in FIG. 5.
Bro~db~nd packet switch 6002 responds to the physical routing header of each packet it receives by tr~n~mitting that packet to a conllllullication path circuit, e.g., 6004 i~1entified by the physical routing header. The identified collllllunication path circuit 6004 receives the packet and stores it in a buffer 64. A
tr~n~mitt.qr 65 reads packets from the buffer 64, removes the physical routing header 15 and transmits the packet in B-ISDN format (FIG. 3) to the destin~tion customer on coll~llunication path 6115. Communication path circuit 6005 responds similarly to transmit packets from bro~lb~n-l packet switch 6002 to the interface unit 6100 over the comlllullication path 6114.
Translation table 63 of a co....~ ication path circuit, e.g., 6003 stores 20 the physical routing header and the new VCI for each packet received on its connected com,llullication path, e.g., 6116. For VCIs which identify collllllunication among cu~lom~l~, the new VCI and physical routing header stored in tr~n~l~tion table 63 are colll~uled by control unit 6017 and tr~n~mitted to table 63 when a connection is set-up. Other VCIs on the co..-.~ -ication paths, e.g. 6115, are 25 permanently assigned to a switching function and the new VCI and physical routing headers associated therewith are stored in the translation table 63 when the system is initi~li7~A For example, VCI 1 is acsignçd to be a control information channel on both co.--.~ -ication paths 6115 and 6116. The physical routing header stored with regard to VCI 1 in translation tables 63 of comlllullication path circuits 6003 and 30 6004 identifies the comlllunication path circuit 6005 which is connected to the interface unit 6100 via co-"~ -ication path 6114. The new VCI stored in each translation table 63, is unique for each collllllullication path 6115 and 6116 so that the interface unit 6100 can distinguish the source of the control information.
FIGS. 6, 7 and 8 are representations of translation table 63 of 35 comlllutlication path circuits 6003, 6004 and 6005, respectively. Each line of the represented translation tables corresponds to a received VCI (VCI IN) from one of 20367~2 g co~ unication paths 6114,6115 or 6116 and identifies the physical routing header(PRH) to be appended to the packet and the new VCI (VCI OUT) to be used to to replace the received VCI . The first line of FIG. 7 shows that when a B-ISDN packet is received in VCI 1 (the preassigned control channel) a physical routing headerS (PRH) defining collllllullication path circuit 6005 is to be appended to the packet and the new VCI of 17 is to be used to replace the received VCI of 1 before the packet is tr~n.~mitted to the broadband packet switch 6002. Similarly, as shown in FIG. 6,when a packet having VCI 1 is received from co" " "u~- ication path 6116 by comlllullication path circuit 6003, a physical routing header defining col,lmullication 10 path circuit 6005 and a new VCI of 16 are appended to the packet before it istr~n~mitted to bro~lbfln-1 packet switch 6002. It can be seen from these two examples that although each of the replesented packets is received in the control channel VCI 1 and sent to the same co"-"~"-~icfltion path circuit 6005 they are each given different VCIs (16 and 17) which are tr~n~mitted through colllmullication path 15 circuit 6005 to interface 6100. The distinctive VCIs of 16 and 17 are used todistinguish between information from comlllullication path circuit 6003 and commllnication path 6004. The second lines of FIGS. 6 and 7 represent an ongoingcommunication between customers attached to comlllullication paths 6115 and 6116.
As shown in FIG. 6, packets received in VCI 18 at colll"lullication path circuit 6003 20 are sent to co"-"~ licfltion path circuit 6004 of co~lllllullication path 6115 in VCI 64.
The other direction of the colllmullication is represented in FIG. 7, which shows that packets received from co, I ll~ cation path 6115 in VCI 64 are sent to collllllullication path circuit 6003 of co, .~ ation path 6116 in VCI 18. Thetranslation table represented in FIG. 8 shows the physical routing headers and new 25 VCIs to be assigned to packets received on communication path 6114 in VCIs 16,17 and 65.
Interface unit 6100 is shown in greater detail in FIG. 9. All control packets and packets for non-B-ISDN customers are switched by broadband switch unit 6001 to interface unit 6100 via co"..",lllication path 6114 in the format shown in 30 FIG. 3. The header portion of each packet received by interface 6100 is applied via path 6123 to controller 6124 which interprets the VCI of the packet in accordance with path completion information stored in controller 6124. This stored information specifies the one of a plurality of buffer registers 6121, which is to receive each incoming packet. Responsive to the VCI of an incoming packet, controller 6124 35 controls the packet demultiplexer 6120 to gate the customer inf,llllation portion of the packet to the buffer register 6121 specified by the path completion inforrnation in 203~742 controller 6124. Each buffer register is uniquely associated, by the operation of a multiplexor 6122, with a predetermined time slot on a predeterminçd time-multiplex line, e.g. 1201 and 1202. Time slot multiplexer 6122 gates 1 byte from each buffer 6121 to the predetermined time slots at the rate of 1 byte per buffer per 125 5 microseconds (64 kilobits per second) as described in detail in the above-mentioned Beckner et al., patent.
Tnterf~ce 6100 also includes a time slot demultiplexer 6125, which is connected to receive illfclmalion from time-multiplex lines 1201 and 1202. In a reverse operation of time slot multiplexer 6122, each time slot received by 10 interface 6100 on time-multiplex lines 1201 and 1202 is uniquely associated with one of a plurality of buffers 6126 by the operation of time slot demultiplexer 6125.
When a buffer 6126 accllm~ tes an entire packet (48 bytes) it sends a signal via a connection 6128 to controller 6124, which responds thereto by reading the packetfrom the signaling buffer 6126 and connecting the packet to outgoing 15 cc"--" ,~"- ication path 6114 via packet multiplexer 6127. Also in response to the signal from a buffer 6126 on path 6128, controller 6124 generates a 5 byte packet header co~ ~inillg the VCI associated with the signaling buffer and thus associated with the time slot which provides data to that buffer. The generated header is tr~nsmitted to packet multiplexer 6127 where it is appended to the packet from 20 buffer 6126 for tr~nsmi~sion on co,l~l,wlication path 6114.
As previously discussed, control information received by interface unit 6100 in VCIs 16 and 17 of co" " "~ ;cation path 6114 is connected by the operation of int~rf;lce unit 6100 to packet switch unit 6400 (FIG. 2) via a predetermined time-multiplex line 1202 and a pre~eterminçd time slot. Packet switch unit 6400 in turn 25 connects the control information to control unit 6017 via a processor interface 6300.
In addition to the well-known capability for controlling time slot interchange unit 6011, packet switch unit 6400 and for cooperating with other switching modules, control unit 6017 controls the operation of the broadb~nrl switch unit 6002 and the interface unit 6100 to provide connections between B-ISDN customers connected to30 colllmullication paths 6115 and 6116 and belw~;ell B-ISDN customers connected to co"-"""-ication paths, e.g. 6115 and non-B-ISDN customers connected to other switching modules, e.g., 1000. Control over such connections is implemented by controlling the contents of translation tables 63 of the comllluilication path circuits, e.g. 6003, and the path completion information in controller 6124.

20367~

Control unit 6017 controls all co~ lunication on co~ -ication paths 6114 through 6116 and time multiplexer lines 1201 and 1202. To I l l~i n~
such control, information regarding the capacity of each connection facility and the use of each VCI and time slot within the system of F~G. 2 is stored in control S unit 6017 and updated whenever a collllllullication change occurs. This information is used as discussed below to complete connections involving B-ISDN customers.
The following is an example of the establishment of an inter-B-ISDN
connection from an origin~ting customer connected to comlllullication path circuit 6004 to a destination customer connected to cc,llllllunication path circuit 6003. The 10 originating customer generates a control packet identifying the originating customer, the destination customer and the bandwidth to be allotted to the connection. This packet is tran~mitted to broadb:~nd switch unit 6001 including a B-ISDN header identifying VCI 1, the preassigned B-ISDN control channel. In response to the packet including the VCI 1, collullullication path circuit 6004 of broadband switch 15 unit 6001 affixes to the packet a physical routing header identifying coml~lullication path circuit 6005 and changes the incoming VCI 1 to new VCI 17 (see FIG. 7, line 1) which identifies a control packet from co,,-,,---l-ication path circuit 6004. The modified packet is then sent to co,-"",-,-ication path circuit 6005 via the broadband packet switch 6002. Coll.-llullication path circuit 6005 receives the packet from broadband packet switch 6002 and transmits it over path 6114 to interface unit 6100.
In response to the VCI 17 and the path completion inrolllla~ion stored in controller 6124, the packet interfa~e unit 6100 places the bytes of the customerinformation portion of the packet in predetermined time slots of a predeterminedtime-multiplex line 1202 to packet switch unit 6400.
Packet switch unit 6400 receives the packet in the predetermined time slot of the predetermined time-multiplex line which is reserved for control packets and connects the packet to control unit 6017 via processor interface 6300. The connection of control packets to the associated control unit is described in detail in the previously mentioned Beckner et al., patent. Control unit 6017 interprets the 30 incoming packet as a request for connection between the comlllullication paths 6115 and 6116 connected to cc." " ,--.~ i~ation path circuits 6004 and 6003, respectively and consults a table (not shown) to ascertain whether sufficient bandwidth exists through both of these collllllunication path circuits to serve the requested co,l~llunication.
When insufficient bandwidth exists at either of the cc,ll-.~lullication path circuits, 35 control unit 6017 returns a control message to the origin;lting customer via packet switch unit 6400, the interface 6100 and broadband switch unit 6001 denying the 2~3~742 connection. Alternatively, when sufficient bandwidth is present, control unit 6017 transmits a set up message over connector 6027 to controller 6006 of broadband switch unit 6001. The set up message specifies the VCIs which are to be used for the connection on each of the comlllu-lication paths 6115 and 6116.
In the present example, VCI 64 is specified for use on co,-""~ ication path 6115 at col--.-,~ ic~tion path circuit 6004 and VCI 18 is specified for use by co------..nication path 6116 at co--..--ll.-ication path circuit 6003 as represented in FIGS.6 and 7 at line 2. In response to the set up message, controller 6006 stores in the translation table 63 of trunk controller 6004 (F~G.7) data specifying the physical 10 routing header (6003) to be affixed to each packet received in the VCI 64 on colll--u~l-ication path 6115 to direct packets to trunk controller 6003 and datadefining the VCI 18 which is to replace the incoming VCI 64. Similarly, controller 6006 stores in the translation table 63 of trunk controller 6003 (FIG.6) the physical routing header and VCI 64 which are to be used for packets received at 15 co----llll--ication path circuit 6003 in VCI 18. In addition to the set up ofcollllllullication path circuit translation tables 63 of coll~ unication path circuits 6003 and 6004, a control message is sent to both the cri~in~tion and te~nin~tioncu~lolllt;l~ via a B-ISDN control path through the interface unit 6100 and broadband switch unit 6001 identifying that a connection is established and the VCIs to use for 20 that connection. Since the entire connection involves only a broadband switch 6001, no other unit within broadb~n-l switching module 6000 needs to be controlled to provide the connection.
Calls are also set up be~weell narrowband subscribers connected, for example, to narrowband switch module 1000 (FIG. 1) and broadband ISDN
25 subscribers connected to bro~db~nd switch module 6000. Such a call requires aconnection from the originating co---.~ --ication path, e.g., 6115 to the interface 6100, connection through interface 6100 to time slot interchange unit 6011 via atime slot on a predetermined time-multiplex line 1201 and a connection to narrowband switch unit 1000 via the time-multiplex switch 10. A request for such a 30 connection is received from the ori~in~ting B-ISDN customer in the control channel VCI 1 of that customer and is forwarded as described above to control unit 6017.The latter unit determines the availability of bandwidth on co"~ltlll-ication paths 6115 and 6114 for call completion. It ascertains, by collmlunication with central control 30 and n~lvwl,and switch unit 1000, the availability of the destination and 35 the identity of a path through time-multiplex switch 10 to that destination. The establishment of paths between switching modules via time slot interchange units, 2~31~7~2 e.g. 6011, and a time-multiplexed switch 10 is described in detail in the above discussed Beckner et al., patent.
When the necessary co~"l,unication paths are available, control 6017 sends set up messages to controller 6006 of broadband switch unit 6001 and to 5 controller 6124 of interf~ce unit 6100 to specify the VCIs and time slots to be used to provide necessary connections. In the present example, it is ~sumecl that VCI 80 on co~ ication path 6115 and VCI 65 on co" "nl l i-ication path 6114 are selected by control unit 6017 to complete the connection. Controller 6006 responds to the set up message from control unit 6017 by storing inrollllation in the translation tables 10 represented in line 3 of FIGS. 7 and 8. The set up message from control unit 6017 to controller 6124 specifies a selected time slot on a selected time-multiplexed line 1201 for use in making the requested connection. Controller 6124 responds to the set up message from control unit 6017 by storing in the controller 6124 pathcompletion information for controlling the tr~n~mi~ion of information received in 15 VCI 65 of co,,,,-~,-ication path 6114 to the selected time slot to time slot interchange unit 6011 and for connecting information received in the selected time slot from time slot interchange unit 6011 to VCI 65 on co"""ll~ tion path 6114.
In the prece ling examples, connections were established in response to call set up packets from br~adb~nd customers. Connections between broadband and 20 n~,owl,alld customers are also established in response to request messages from narrowband cu~ el~. The following is an example of a call set up between a narrowband cu~mer connected to path 1004 (FIG. 1) and a bro~lb~nd customer connected to co"..llunication path 6116. The call set up message identifying thenarrowband and bro~clb~nd customers is received from path 1004 by nalluwband 25 switching module 1000 and folw~uded to central control 30 via previously established control paths through the time-multiplex switch 10 and control distribution unit 31 which are known in the art and described in detail in the aforementioned Beckner et al. patent. Central control 30 transmits the set up message to the broadband switching module 6000 via pre-established control paths30 through the control distribution unit 31 and the time-multiplex switch 10 to the time slot interchange unit 6011 (FIG. 2). The time slot interchange unit 6011 connects the set up message to control unit 6017.
Control unit 6017 responds to the set up message in the same manner that it responds to a call set up packet from a broadband customer requesting a 35 bro~db~nrl-to-narrowband connection, that is, the control unit selects VCIs and physical routing headers for the broadband connection to and from con""u,lication ~3S~42 path 6116 and interface 6100. Further, control unit 6017 controls interface 6100 to complete the necessary connections through interface 6100 to bi-directionally connect the information making up the requested commllnication between time slotinterchange unit 6011 and co~ ullication path 6114. The rem~indtor of the path S from time slot interchange unit 6011 to path 1044 of nall~wl,and switching module 1000 is described in detail in the aforementioned Beckner et al. patent.
VIDEO SWITCIIING ARRANGEMENT
Broadband switch module 6000 provides 150 megabit per second capacity to bro~db~n~1 cu~ el ~ attached by co,--" " ~,~ication paths 6115 and 6116.
10 This large capacity makes possible the connection to customers of packetized video signals which require appr~ ately 45 megabits per second. A broadband switch module 6000 can be used to provide video signals to the cu~lolllels. FIG. 10 shows an embodiment of the broadband switch module shown in FIG. 2 which is equipped to provide video services. The following describes the embodiment of FM. 10. It 15 should be noted that units having the same numerical design~tion in FIG. 10 as in FIG. 2 operate in substantially the same manner previously described and are notdiscussed in detail herein below.
The embodiment of FIG. 10 includes a video switch 100 which operates under the control of a video controller 118 and a plurality of video sources 102 and 20 103. Each of the video sources generates and tr:~nsmit~, via an associated path 105 and 106 respectively, signals in the bro~db~nd ISDN format of FIG. 3. Video switch 100 is of the type shown and described in G. W. Richards, U. S. Patent No.4,566,007 and provides circuit switched connections from any of the video source inputs, e.g., 105, to one or more of a plurality of outputs, e.g., 107 and 108.
25 Outputs 107 and 108 are connected to broadb~nrl switch unit 6001 which distributes the packetized video signals to cu~ .,r con~llullication paths 6115 and 6116.
Packetized video signals, unlike bursty con~uler data, continuously use a relatively high bandwidth. That is, when a customer wants to watch a television program from one of the video sources 102 or 103 the video signals which are 30 connected to a co,-"--ll.-ic~tion path, e.g., 6115 require a bandwidth of 45 megabits per second for the entire length of the program. If the signals for the program were connected to the collllllunication path 6115 by the broadband packet switch 6002large amounts of switch bandwidth would be used, reducing the switch bandwidth available to provide other connections. When a number of customers are all 35 receiving a video signal, the available switch bandwidth is further reduced.

2 ~ 2 In the present embodiment, the video signal packets on outputs 107 and 108 are not connected to co~ llunication paths 6115 and 6116 by broadband packetswitch 6002 but are combined with other packets destined for the co,~ ication paths in the coll-lllunication path circuit, e.g., 6003 as shown in FIG. 11. Each of the video outputs 107 and 108 of video switch 100 is uniquely associated with one of the co,-",-l"-ication path circuits 6003 and 6004, respectively, and is connected to a buffer 64' of the associated coll~llunication path circuit. Buffer 64' functions in a manner similar to buffer 64 of FIG. 4 except that that buffer 64' merges the video packets from video switch 100 with the packets from broadband packet switch 6002before they are sent by the tr~nsmitter 65 to a customer. FIG. 12 shows buffer 64' of comlllullication path 6003 in greater detail and represents the buffer 64' used in all of the co",~ lni~ation path circuits of the present embodiment.
Buffer 64' comprises a data buffer 111, which is connected by path 109 to receive packets from bro~b~n~l packet switch 6002, and a video buffer 112, which is connected by path 107 to receive video packets from video switch 100. The outputs of video buffer 112 and data buffer 111 are connected to a gate circuit 114 which selectively connects packets to output 110 for connection to tr~n~mitter 65.
Gate circuit 114 operates under the control of output selector 113 which receives inputs from both the data buffer 111 and video buffer 112.
The input signals to the output selector 113 from buffers 111 and 112 indicate when a packet is present in the respective buffers for tr~n~mi~ion.
Whenever a video packet is available in video buffer 112 output selector 113 controls gate circuit 114 to gate the video packet to tr~n~mitter 65, regardless of the contents of data buffer 111. Alternatively, when no video packet is available, output selector 113 controls gate circuit 114 to connect packets from data buffer 111 to tr~n~mitt~r 65. Giving priority to the video packets is desirable since the video signal they represent is continuous in nature and substantial delay in the delivery of video packets can adversely affect the quality of video image presented to the customer.
The following describes the connection of signals from video source 102 to a customer attached to co"-.~--..~ication path 6116. A video connection to a customer is established in response to a video request control packet from that customer. The video request packet, which iclentifies the requesting customer and the particular video source 102 desired, is connected to control unit 6017 via the 35 broadband switch unit 6001 and the interface 6100 in same manner that the previously discussed call set up packets are connected to 6017. Control unit 6017 203~742 responds to video requests by analyzing the available bandwidth to determine if the request can be satisfied. When insufficient bandwidth exist on co,-"-,l-"ication path 6116 to the requesting customer, control unit 6017 denies the request and notifies the requesting customer of such denial via a packet message. ~lt~ tively, when 5 bandwidth is available, the control unit 6017 returns a packet indicating such to the requesting customer and transmits a connection control message to video switch controller 11 8 via path 6027. Video switch controller 11 8 responds to the connection control message by controlling video switch 100 to connect video packets from video source 102 to path 107 which is associated, by connection to 10 co",-~ ication path circuit 6003, with co-~ icatir~n path 6116. Packets from video switch 100 are received by the buffer 64' of col"lllunication path 6003 and are tr~nsmitted to the requesting customer as described above.
A connection is terminated by a video disconnect packet from the customer. The video disconnect packet is connected from co, . .,--" ,- ication path 6116 15 to control unit 6017 which deallocates the previously allocated bandwidth on communication path 6116 and notifies video switch controller 118 to disconnect the path through video switch 100.
The allocation of bandwidth for video connections and all other connections to co. - -. . -~ ation paths 6115 and 6116 is performed by the control unit 20 6017 on the basis of capacity tables stored thereby. Centralizing the allocation of bandwidths is done to improve the efficiency of the system as a whole. Once video bandwidth has been allocated on a co.. ~ ication path, e.g., 6116 the control unit 6017 need not be consulted unless a change in allocation is needed. Changing video sources (changing channels) in the present embodiment does not require changes in 25 bandwidth allocation and therefore does not require the intervention of control unit 6017.
A broadb~nd switch unit 6001 (FIG. l l ) of a broadb~nd switch module 6000 equipped to provide video service includes a col~ uilication path circuit 6007 which is connected to an input/output port of broadband packet switch 6002. A
30 co-llmuilication path 120 of colllmullication path circuit 6007 is connected to video switch controller 118. Co,-ll--l-l-ication path circuit 6007 is used to rcJlw~d channel change requests to video switch controller 11 8 after a video connection has been established by controller 6017. That is, once video connection permission has been granted by control unit 6017 to a colll,-~ -ication path, e.g., 6116 the particular video 35 source which is used to occupy that connection is controlled by video switch controller 118 in response to requests from customers.

After permission to use video bandwidth has been granted by control unit 6017 and a video source, e.g., 102 has been connected to a co...,..l-nication path e.g. 6116, as described above, the particular video source can be changed without consulting control unit 6017. A video source change is initiated when a customerS connected to a cc .... - ~ ication path circuit, e.g., 6116 transmits a video source identity packet to its associated co.-...--..-ic~tion path circuit, e.g., 6003. The video source identity packet includes a predetermined video source identity VCI which in the present example is VCI 200. Tr:~n~mitter 62 (FIG. 11) upon accessing translation table 63 changes the packet VCI to 203 and affixes a physical routing header 10 identifying co-lllllunication path circuit 6007 as shown in line 3 of FIG. 6. The VCI
of 203 is unique to coll-,llunication path circuit 6003 so that the video switchcontroller 118 can identify the source of the change request. Broadband packet switch 6002 responds to the physical routing header from table 63 and gates the packet with VCI 203 to collu-lunication circuit 6007 which forwards the video 15 source identity packet to video switch controller 118 via co~ unication path 120.
Video switch controller 118 responds to the packet requesting a change from one video source, e.g., 102 to another video source, e.g., 103 by selectively connecting a new video source, e.g., 103 to path 107. No changes are required in the operation of buffer 64' which continues to connect video packets to co.~llunication path circuit 20 6116 regardless of the source of those packets.

Claims

1. A packet switching arrangement comprising;
a packet switching network comprising a plurality of incoming lines for receiving customer packets from customers, a plurality of outgoing lines for conveying packetized information to said customers and means responsive to customer packets received on said incoming lines for selectively connecting saidreceived customer packets to said outgoing lines;
a plurality of sources of video signal packets;
video switch means for selectively connecting ones of said video signal packets to said outgoing lines without being transmitted through said packet switching network; and control means common to said packet switching network and said video switch means and responsive to control signals received from said incoming lines for controlling the connections provided by said packet switching network and said video switch means.

2. The arrangement of claim 1 wherein said packet switching network comprises means responsive to control packets received on said incoming lines for connecting said control packets to said control means; and said control means comprises means responsive to said control packets for controlling the connections provided by said packet switching network and said video switch means.

3. The arrangement of claim 1 wherein each of said outgoing lines comprises a selector means for receiving customer packets from said packet switching network and video signal packets from said video switch means and for selectively merging said customer packets and said video signal packets onto one of said outgoing lines.

4. The arrangement of claim 3 wherein said selector means interleaves said customer packets from said packet switching network and said video signal packets from said video switch means into a stream of packets on one of said outgoing lines.

5. The arrangement of claim 3 wherein said selector means of a first outgoing line comprises means for selectively connecting a video signal packet from said video switch means onto said first outgoing line whenever a video signal packet is present at said selector.

6. A packet switching arrangement comprising:
a packet switching network comprising a first communication path comprising a first input line and a first output line, a second communication path comprising a second input line and a second output line and means responsive to customer packets received on said first input line for selectively connecting said received packets to said second output line;
a plurality of sources of video signal packets, video switch means for selectively connecting ones of said video signal packets to said second output line contemporaneously with the connection by saidpacket switching network of packets from said first input line to said second output line; and means responsive to control packets received at said input lines for connecting said control packets to a control means;
said control means is common to said packet switching network and said video switch means and is responsive to said control packets for controlling theselective connection of said customer packets from said first input line to said second output line by said packet switching network and for controlling the selective connection of said video signal packets to said second output line by said videoswitch means.

7. The arrangement of claim 6 wherein said control means performs bandwidth allocation of a path for said packetized information from said video switch to selected ones of said outgoing lines and performs set up of paths for customer packets containing messages from said incoming lines through said packet switching network.

8. The arrangement of claim 6 wherein said messages include channel selection messages, said channel selection message being fed by said packet switching network to said video switch means, and said video switching means effecting changes in the selection of said video signal packets in response to said channel selection messages.

9. The arrangement of claim 6 wherein said control packets comprise customer control packets received at first input line and video control packets received at said second input line; and said control means is responsive to said customer control packets for controlling the selective connection of said customer packets from said first input line to said second output line and responsive to said video control packets forcontrolling the selective connection of said video signal packets to said secondoutput line by said video switch means.

10. The arrangement of claim 6 wherein said second outgoing line comprises a selector means for receiving customer packets from said packet switching network and video signal packets from said video switch means and for selectively merging said customer packets from said packet switching network andsaid video signal packets from said video switching means onto said second outgoing line.

11. A video packet switching arrangement comprising:
video switch means connected to a plurality of customer access lines for selectively connecting video signal packets from a plurality of video sources to said customer access lines;
control means, responsive to a video service request packet received on one of said customer access lines, for sending connection permission signals to said video switch means;
means for connecting a video source identity packet received on said one customer access line to said video switch means, said video source identity packet identifying one of said video sources; and said video switch means comprises means responsive to said permission signals and said video source identity packet for connecting video signal packets from said identified video source to said one customer access line.

12. The arrangement of claim 11 comprising a packet switch means for selectively connecting packets received on said customer access lines to other ones of said customer access lines and to said control means.

13. The arrangement of claim 11 said control means comprises means for recording the available bandwidth on said one customer access line and for sending said permission signals when the bandwidth available on said one access line exceeds the bandwidth required to convey video signal packets from one of said video sources.

14. A video packet switching arrangement comprising:

video switch means connected to a plurality of customer access lines for selectively connecting video signal packets from a plurality of video sources to said customer access lines;
control means, responsive to a video service request packet received on one of said customer access lines and identifying a first one of said video sources, for sending connection permission signals identifying said first video source to said video switch means;
said video means comprises means responsive to said connection permission signals for connecting said first video source to said one customer access line;
means for connecting a video source change packet received on said one customer access line to said video switch means, said video source change packetidentifying a second one of said video sources; and said video switch means comprises means responsive to said connection permission signals and said video source change packet for disconnecting said first video source from said one customer access line and for connecting video signal packets from said second video source to said one customer access line.

15. The arrangement of claim 14 wherein said first means for connecting comprises a packet switch means for selectively connecting packets received on said customer access lines to other ones of said customer access lines and to said first control means.

16. The arrangement of claim 15 wherein said first control means comprises means for recording the available bandwidth on said one customer access line and for sending said connection permission signals when the bandwidth available on said one access line access the bandwidth required to convey video signal packets from said first video source.

17. A packet switching arrangement for providing packet switched interconnection among a plurality of customer access lines and for providing packet switched video services to said customer access lines, comprising:
broadband packet switch means connected to said customer access lines for selectively connecting customer packets between said customer access lines;

a video switch means for selectively connecting video signal packets from a plurality of video sources to said customer access lines;
means in said broadband packet switch means for connecting a video service request packet received on one of said customer access lines to a bandwidth allocation controller;
said bandwidth allocation controller comprising means responsive to said video service request packet for granting permission to said video switch means for the connecting of video signal packets to said one customer access line;
means, in said broadband switch means, responsive to a video source request packet received on said customer access line and identifying one of saidvideo sources for connecting said video source request packet to said video switch means; and said video switch means comprises means responsive to said video source request packet and to the grant of permission by said bandwidth allocation controller for connecting packets from said identified video source to said one customer access line.

18. A broadband switching module comprising:
a broadband switch unit comprising interface means connected to a plurality of incoming and outgoing lines and broadband packet switch means for selectively connecting broadband packets received on said incoming lines to saidoutgoing lines;
video switch means operable for connecting to any one of said outgoing lines any one of a plurality of video signals receivable from a plurality of video sources;
video switch control means responsive to a receipt of permission signals for operating said video switch means to establish video switch connections fromone of said plurality of video sources to one of said outgoing lines and furtherresponsive to channel change signals received on one of said incoming lines for connecting another of said video sources to said one outgoing line; and a bandwidth allocation control unit responsive to control signals received on said incoming lines for generating said permission signals.

19. The module of claim 18 wherein said interface means comprises selector means for selecting packets from said broadband packet switch means and from said video switch means for transmission on each of said outgoing lines.