(12) United States Patent
`Cox et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US006459708Bl
`US 6,459, 708 Bl
`Oct. 1, 2002
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) APPARATUS AND METHOD FOR
`PROVIDING Tl/El
`TELECOMMUNICATIONS TRUNKS OVER
`IP NETWORKS
`
`(75)
`
`Inventors: James Cox, Cedar Park, TX (US); Jack
`Gerlach, Austin, TX (US); James
`Mott, Austin, TX (US); Robert
`Pearson, Round Rock, TX (US)
`
`(73) Assignee: Toledo Communications, Inc., Austin,
`TX (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/468,775
`
`(22) Filed:
`
`Dec. 21, 1999
`
`(51)
`Int. Cl.7 ............................. H04J 3/02; H04L 12/66
`(52) U.S. Cl. ....................... 370/537; 370/463; 370/465;
`370/466
`(58) Field of Search ................................. 370/352, 353,
`370/389, 390, 392, 401, 412, 420, 422,
`463,465,466, 467, 470, 471, 474, 537
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`4,740,955 A * 4/1988 Litterer et al. .............. 370/264
`5,426,637 A * 6/1995 Derby et al. ................ 370/401
`5,440,616 A * 8/1995 Harrington et al. ........... 379/88
`5,682,386 A * 10/1997 Arimilli et al. ............. 370/468
`5,892,764 A * 4/1999 Riemann et al. ............ 370/401
`5,910,946 A * 6/1999 Csapo ........................ 370/328
`6,044,080 A * 3/2000 Antonov ..................... 370/401
`6,064,653 A * 5/2000 Farris ......................... 370/237
`6,069,890 A * 5/2000 White et al. ................ 370/352
`6,219,348 Bl * 4/2001 Allen, Jr. et al. ........... 370/354
`
`6,298,043 Bl * 10/2001 Mauger et al.
`
`............. 370/248
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`WO
`
`1 026 848 A2
`PCT/US98/24290
`
`3/2000
`5/1999
`
`OTHER PUBLICATIONS
`
`Ramnath A Lakshmi-Ratan, XP--000851517, The Lucent
`Technologies Softswitch-Realizing The Promise Of Con(cid:173)
`vergence, Apr. 2, 1999, p. 176, col. 2, line 10-p. 181, col.
`2, line 16.
`Raffaele Nora, XP-000991295, "Circuit Emulation Over IP
`Networks", Aug. 25, 1999, pp. 187-201.
`Shaul Berger, XP--000992213, "Implement A Single-Chip,
`Multichannel VoIP DSP Engine", May 25, 2000, pp.
`101-105.
`* cited by examiner
`Primary Examiner-Hassan Kizou
`Assistant Examiner-Saba Tsegaye
`(74) Attorney, Agent, or Firm-Richard K. Huffman; James
`W. Huffman
`
`(57)
`
`ABSTRACT
`
`An apparatus and method are provided that enable Tl (or
`El) telecommunications frames to be transmitted between
`Tl (or El) telecommunications switches over a high band(cid:173)
`width packet-switched network. The apparatus includes
`trunk interface logic and network translation logic. The
`trunk interface logic is coupled a central office switch via a
`central office switch trunk, and receives the telecommuni(cid:173)
`cations frames from the central office switch. The network
`translation logic is coupled to the trunk interface logic. The
`network translation logic translates the telecommunications
`frames into network packets that the telecommunications
`frame data may be transferred over the high bandwidth
`packet-switched network.
`
`40 Claims, 8 Drawing Sheets
`
`Tl (El )-to-IP Multiplexer
`
`/00
`
`NETWORK
`TRANSLATION LOGIC
`
`NETWORK
`INTERFACE
`LOGIC
`
`Pet., Exh. 1004, p. 1
`
`

`
`U.S. Patent
`
`Oct. 1, 2002
`
`Sheet 1 of 8
`
`US 6,459, 708 Bl
`
`PSTN
`VOlCE SVVffCH
`
`B
`
`PSTN
`VOICE SIN!TCH
`
`PSTN
`VOICE SWITCH
`
`c
`
`Pet., Exh. 1004, p. 2
`
`

`
`Generation of Outbound Tl Telecommunications Frames
`204
`CHANNEL 24
`"
`
`y-205
`
`y-206J\ l
`
`~NKC.)
`1, v
`
`TOM
`
`c
`
`•
`•
`•
`
`CHANNEL2
`
`CHANNEL 1 •
`"
`
`C9
`~o
`I -
`0 C9
`I- 0
`~ _J
`Cl)
`
`CHANNEL24
`
`•
`•
`•
`
`CHANNEL2
`
`CHANNEL1
`
`TOM
`
`B
`
`"
`
`y-205
`
`y-206
`TRUNKB
`
`\JJ.
`
`d .
`.
`~
`~
`......
`~
`......
`
`=
`
`0
`I")
`!""'"
`'"""'
`N
`c c
`
`N
`
`~
`
`'Jl
`
`~
`~
`
`=-
`.....
`N
`.....,
`0
`00
`
`1200
`
`_J
`
`(/)
`w
`~
`<(
`a:
`LL
`~
`~
`cs
`0
`0
`z
`::J
`0 ro
`t-
`::J
`0
`
`FIG. 2 (Related Art)
`
`N
`
`201~
`
`10
`
`201~
`
`9
`
`8
`
`5
`
`4
`
`(/)
`w
`z
`:::i
`w
`u
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`>
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`0
`_J
`<(
`z
`<(
`('.)
`z
`~
`0
`u
`~
`
`8 KHz SAMPLER
`
`AID
`
`•
`•
`•
`
`202
`
`8 KHz SAMPLER
`
`8 KHz SAMPLER
`
`8 KHz SAMPLER
`
`8 KHz SAMPLER
`
`8 KHz SAMPLER
`
`8 KHz SAMPLER
`
`8 KHz SAMPLER
`
`•
`•
`•
`
`AID
`
`AID
`
`AID
`
`AID
`
`AID
`
`AID
`
`AID
`
`8 KHz SAMPLER 1-----+1
`
`AID
`
`1-----+1
`
`8 KHz SAMPLER 1-----+1
`
`AID
`
`1-----+1
`
`I
`
`8 KHz SAMPLER 1-----+1
`
`AID
`
`1-------+l
`
`CHANNEL2
`I CHANNEL 1 •
`
`CHANNEL 24.
`I
`
`•
`•
`•
`
`f205
`
`TOM
`
`A
`
`.[20~\
`TRUNKA
`)
`v
`
`e
`
`rJ'J.
`O'I
`~
`(It
`\0
`~
`Q
`~
`~
`lo-"
`
`Pet., Exh. 1004, p. 3
`
`

`
`U.S. Patent
`
`Oct. 1, 2002
`
`Sheet 3 of 8
`
`US 6,459, 708 Bl
`
`f'I
`
`Carrff'.r Tr1.U?!Unission versus _P(:cket-5\~,fu·hed 1Venrork Tran;smis.·rf,ons
`-----------------------·
`
`Pet., Exh. 1004, p. 4
`
`

`
`U.S. Patent
`
`Oct. 1, 2002
`
`Sheet 4 of 8
`
`US 6,459, 708 Bl
`
`N
`
`SWITCH
`
`411
`Atoe
`414
`
`If
`
`\
`
`~ : I Ti
`-•W
`A
`1 !
`~
`1,_. ==m,,,,,,,,,,,,,,,,,m;
`L4D1
`
`SWlTCH
`
`B
`
`T1
`SVVffCH
`
`MULTIPLEXER
`
`T1
`swrrcH
`
`N
`
`N lo B
`
`NtcC
`
`MUL T!PLE.XER
`
`N
`
`Pet., Exh. 1004, p. 5
`
`

`
`U.S. Patent
`
`Oct. 1, 2002
`
`Sheet 5 of 8
`
`US 6,459, 708 Bl
`
`FIG. 5
`
`Tl (El)-to-IP Multiplexer
`
`1500
`
`510
`
`520
`
`A to z
`TRUNK
`---~ INTERFACE Ml-.... ~
`LOGIC
`
`Pet., Exh. 1004, p. 6
`
`

`
`U.S. Patent
`
`Oct. 1, 2002
`
`Sheet 6 of 8
`
`US 6,459, 708 Bl
`
`FIG. 6
`
`601
`
`A
`XMIT
`
`/603-
`
`"
`
`~604\
`
`A
`RCV
`
`L502
`
`B
`XMIT
`
`B
`RCV
`
`c
`XMIT
`
`c
`RCV -
`
`D
`XMIT
`
`D
`RCV -
`
`-
`
`-
`
`Network Translation Logic
`
`1600
`
`r 610
`
`:
`
`1620
`
`/630
`
`i
`
`; 611
`APPLICATION T
`- "
`
`;
`
`...
`
`ENVELOPE
`LOGIC
`
`UDP/IP/MAC
`PREFIX LOGIC
`
`T62~
`- "
`
`i
`
`100 BASE TX
`PORT
`CONTROLLER'.
`
`: - /631
`
`"
`
`'
`
`:
`
`1
`
`:
`
`' ;
`
`'
`
`r612
`
`POI NT-TO-POI NT
`CONNECTION
`LOGIC
`
`Pet., Exh. 1004, p. 7
`
`

`
`U.S. Patent
`
`Oct. 1, 2002
`
`Sheet 7 of 8
`
`US 6,459, 708 Bl
`
`FIG. 7
`
`Trunk Packet Composition for Ethernet Data Network
`
`ETHERNET PREAMBLE (12 BYTES)
`
`MEADIA ACCESS CONTROL (MAC) HEADER (14 BYTES)
`
`INTERNET PROTOCOL (IP) HEADER (20 BYTES)
`
`USER DATAGRAM PROTOCOL (UDP) HEADER (8 BYTES)
`
`APP HEADER
`(14 BYTES)
`
`APP HEADER
`(14 BYTES)
`
`PORT FRAME DAT A
`(T1 - 48 BYTES, E1 - 64 BYTES)
`
`PORT FRAME DATA
`(T1 - 48 BYTES, E1 - 64 BYTES)
`
`742
`
`•
`• •
`
`APP HEADER
`(14 BYTES)
`
`PORT FRAME DATA
`(T1 - 48 BYTES, E 1 - 64 BYTES)
`
`i'45
`
`Multiple T1 (E11)
`Frames to Same
`Destination
`Multiplexer
`
`1500 BYTES MAX
`
`FIG. 8
`
`Application Header Structure
`
`1700
`
`~ 705
`
`~ 710
`
`.r 720
`
`.r 730
`
`.r 740
`
`.r 740
`
`741
`
`740
`
`1800
`
`811
`
`VER CMND FLAGS HLEN SRCP DESTP SEQ/ FRCNT SRCK DESTK
`NAO
`
`REPIP
`
`13
`
`12
`
`11
`
`10
`
`9
`
`8
`
`7
`
`6
`
`5
`
`4
`
`3
`
`BYTE 0
`
`Pet., Exh. 1004, p. 8
`
`

`
`U.S. Patent
`
`Oct. 1, 2002
`
`Sheet 8 of 8
`
`US 6,459, 708 Bl
`
`FIG. 9
`
`Methodfor Providing Tl/El Trunks Over and IP Network
`
`begin
`
`902
`
`read incoming IP
`packet queue
`
`904
`
`strip headers from IP
`packets
`
`906
`
`route frame data to
`addressed T1/E1 port
`output queue
`
`908
`
`read input queues for
`all T1/E1 ports
`
`910
`
`route frame data
`addressed to port
`within same
`multiplexer to
`addressed T1/E1 port
`output queue
`
`912
`
`route frame data
`addressed to port
`within different
`multiplexer to
`corresponding IP
`output queue
`
`914
`
`if necessary, generate
`error data and/or fill
`data; route to proper
`T1/E1 or IP output
`queue
`
`916
`
`place T1/E1 frame
`data in output queues
`into T1/E1 carrier
`stream on ports
`
`918
`
`append headers to
`data in IP output
`queue
`
`920
`
`transmit packets over
`data network
`
`922
`
`924
`
`N
`
`Pet., Exh. 1004, p. 9
`
`

`
`US 6,459,708 Bl
`
`1
`APPARATUS AND METHOD FOR
`PROVIDING Tl/El
`TELECOMMUNICATIONS TRUNKS OVER
`IP NETWORKS
`
`30
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates in general to the field of
`telecommunications, and more particularly to an apparatus
`and method for providing Tlffl telecommunications links
`over a high bandwidth data network.
`2. Description of the Related Art
`Along with the widespread proliferation of the telephone
`in the early 1900's came the attendant development of the
`supporting infrastructure required to interconnect millions
`of these communication devices. A complex network of
`wires, cables, and switching equipment was developed to
`support the switching of calls from their source to their
`destination. To a significant degree, this infrastructure is still
`in place today.
`The backbone of the public switched telephone network
`(PSTN) consists of a network of local exchanges, or local
`switches. A local switch is the point at which all of the
`telephones within a its local area connect into the PSTN. A
`switch is also referred to as a central office switch or a
`telecommunications switch. Each of the telephones in a
`local area are connected to a pair of telephone wires and all
`of the telephone wires in the local area originate at the
`central office switch. When a user picks up the receiver of
`his/her telephone, equipment within the local switch gener(cid:173)
`ates the dial tone that he/she hears in the receiver. When the
`user dials a destination number, the equipment in the local
`exchange decodes the number and routes the call to its
`destination. If the destination telephone is also connected to
`the local switch, or central office switch, then the equipment
`connects the calling telephone pair to the destination tele(cid:173)
`phone pair for the duration of the call. During the
`conversation, voice signals are transmitted as over the
`connected pairs of wires. When the user hangs up the 40
`telephone receiver, then the switching equipment terminates
`the connection between the two pair of wires.
`The above scenario applies, however, only to the inter(cid:173)
`connection of telephones within a local exchange. There are,
`in fact, hundreds of thousands of local exchanges all over the 45
`world. And to support the switching of calls from telephones
`in a source exchange to a destination exchange, there also
`exists a network of cables and supporting equipment. A
`cable or other medium that interconnects telephone
`exchanges, or telecommunications switches, is referred to as 50
`a trunk. A trunk typically is specified to support an average
`number of calls between its source telecommunications
`switch and destination telecommunications switch. Hence,
`when a call is placed from a source telephone interfaced to
`the source switch to a destination telephone interfaced to the 55
`destination switch, the switching equipment in both the
`source exchange and the destination exchange interact to
`effect the call. The source telecommunications switch
`decodes the called number and switches, or routes, the call
`over one of the trunks connected to the destination 60
`exchange. The destination telecommunications switch
`receives the call over the trunk from the source exchange,
`and further decodes the called number so that the call is
`routed to the destination telephone. In any metropolitan area
`today, there is network of local telephone exchanges along 65
`with their associated inter-exchange trunks to handle the
`switching of calls made within that area.
`
`20
`
`2
`Similarly, these larger, metropolitan networks of
`exchanges are interconnected together in the same manner:
`A series of trunks interconnect all of the metropolitan areas
`within the United States and likewise, trunks interconnect
`most of the countries of the world. A trunk is the primary
`interconnection media for the PSTN.
`In earlier years, as noted above, trunks essentially con(cid:173)
`sisted of some number of wires between two central office
`switches. But in addition to the wires, trunks also consisted
`10 of a number of in-line signal amplifiers to prevent degrada(cid:173)
`tion of the analog voice signals that were routed over the
`interconnecting trunks.
`In the 1960's, a major development within the telecom-
`15 :~~~~~:~Yn~f~!~~rfut:~~~~~e~~~:~,e:~~~i~te~~et~a::~::
`drastically reducing the number of wires which were there(cid:173)
`tofore required to provide trunk interconnections between
`central office switches. This development, the Tl carrier
`protocol, prescribes a series of time-division multiplexed
`formats for the transmission of digitized telephone conver(cid:173)
`sation data, each of which allow up to 24 separate conver(cid:173)
`sations to be carried between switches on the same pair of
`telephone wires. A basic Tl signal is a pulse coded modu-
`25 lation carrying 24 8-bit data elements, each of the 8-bit data
`elements containing a digitized and encoded sample of one
`of the 24 conversations. Samples are taken from each of the
`24 conversations, or channels, at a rate of 8,000 samples per
`second and these samples are continuously transmitted at a
`1.544 Mbps carrier frequency over a single pair of wires. A
`125-microsecond portion of the transmission that contains
`encoded samples from channels 1 through 24 is known as a
`Tl frame. In actual practice, out-of-band signaling bits and
`other information are also contained in a Tl frame however
`the basic structure of a Tl frame is as described' above.
`'
`The Tl carrier protocol is the basis protocol that is used
`to transmit trunk data within the United States. Today, it is
`more common to find high speed inter-exchange trunk links
`such as T3 links or OC-48 links. These links are, however,
`aggregates of Tl links that are generated by combining Tl
`link signals through devices commonly referred to as add
`drop multiplexers (ADMs). In Europe, the basis protocol
`used for trunks is El. The El protocol varies from the U.S.
`standard in terms of the encoding of the signals, in terms of
`the number of channels that are sampled and transmitted at
`the 8,000 sample/second rate, and in the absence of signal(cid:173)
`ing bit information. In El, there are 32 channels per frame
`rather than 24. To achieve the 8,000 sample/second rate, the
`El carrier is transmitted at 2.048 Mbps. In Europe, ADMs
`are also used to aggregate El links into higher speed trunks
`such as E3 trunks.
`The benefits provided by the Tl(El) protocol caused a
`significant expansion in the services provided over the.
`PSTN. As a result, telephone service providers have invested
`substantially in switching equipment that provides trunk
`signals compatible with the Tl(El) protocol. It is virtually
`impossible today to find a telecommunications switch which
`does not employ some form of the Tl protocol for the
`provision of inter-switch trunks. And service providers have
`continued to increase their investment in Tl switching
`technologies for nearly forty years. As alluded to above, a
`typical present day trunk consists of a number of aggregated
`Tl links, the most common form adhering to OC-48 proto(cid:173)
`col. OC-48 prescribes a 2.5 Gbps transmission rate.
`Two developments during the 1980's, however, began to
`push the telecommunications industry to provide expanded
`and more varied services, i.e., services other than the trans-
`
`35
`
`Pet., Exh. 1004, p. 10
`
`

`
`US 6,459,708 Bl
`
`4
`packet-switched network to deliver Tl frames to their
`intended destination.
`
`SUMMARY
`
`3
`mission of voice signals. Advances in microcircuit design
`and fabrication techniques have enabled a significant per(cid:173)
`centage of the civilized world to have a computer in the
`home or office. In conjunction, advances in computer net(cid:173)
`working techniques and protocols have enabled all of those
`computers to communicate over the Internet. The Internet is
`a global network of interconnected computers that utilize a
`packet-switched communications protocol known as Inter(cid:173)
`net Protocol (IP). And since the cables and trunks within the
`PSTN already provided the initial skeletal structure for
`integrating local, metropolitan, and global networks of
`computers, telephone service providers began to provide,
`and continue to provide, routing and distribution services for
`computer data that is transmitted via the Internet.
`Five years ago, approximately 95 percent of the traffic
`passed over the PSTN was voice traffic. Today, voice traffic
`accounts for only 50 percent; computer data accounts for the
`remaining 50 percent of the traffic. And projections indicate
`that within another five years, computer data will account for
`over 90 percent of the traffic that is transmitted. Telephone
`service providers are now just beginning to significantly
`invest in packet-switched equipment for routing of computer
`data, or IP data.
`The definite trend, both in terms of use and advances, is
`away from conventional synchronous networks based upon
`the Tl(El) protocol, and towards very high speed packet(cid:173)
`switched networks. Consequently, present day telephone
`service providers are beginning to provide packet-switched
`network routers for the routing of computer data in collo(cid:173)
`cation with their central office switching equipment. In such 30
`an arrangement, the central office Tl(El) switching equip(cid:173)
`ment provides for the transmission of telecommunications
`signals over the Tl-based network and the packet-switched
`equipment is used to route computer data over high band(cid:173)
`width data networks. And while a number of developments 35
`have allowed packet-switched data to be transmitted over Tl
`trunks in the form of Tl frames, there is no extant system
`that allows Tl protocol frames to be transmitted over a
`packet-switched IP network. Granted, techniques and equip(cid:173)
`ment exist for the transmission of voice-type signals over 40
`packet-switched networks, but these techniques require the
`complete replacement of Tl equipment within a PSTN
`switch with voice-over-IP (VOiP) equipment. Because of
`their substantial investment in Tl(El) switching equipment,
`telephone service providers are reluctant to make the change
`to VOiP.
`Yet service providers are still pressed to increase tele(cid:173)
`communications capacity through the addition of trunks
`between their telecommunications exchanges. But because
`they are quite reluctant to abandon their substantial invest(cid:173)
`ment in existing Tl(El) switching equipment, they consis(cid:173)
`tently choose to add trunks that employ Tl(El)-based net(cid:173)
`work equipment. The choice to utilize Tl(El) equipment is
`relatively expensive when compared to utilizing packet(cid:173)
`switched network equipment. And in addition, the choice is
`short-sighted due to the fact that the industry is moving
`toward the increased use of packet-switched networks.
`Therefore, what is needed is an apparatus that allows
`service providers to add Tl(El) trunks between central
`office switches that takes advantage of high speed packet(cid:173)
`switched data networks.
`In addition what is needed is a Tl(El)-to-IP multiplexing
`system that interfaces to Tl(El) telecommunications
`switching equipment but effects a Tl(El) carrier link over a
`high bandwidth data network.
`Furthermore, what is needed is a method for sending
`Tl(El) signals between Tl(El) switches that utilizes a
`
`45
`
`10
`
`15
`
`20
`
`To address the above-detailed deficiencies, it is an object
`of the present invention to provide an apparatus for imple(cid:173)
`menting a Tl(El) trunk between two central office switches
`that utilizes a packet-switched data network as the transmis-
`sion medium.
`Accordingly, in the attainment of the aforementioned
`object, it is a feature of the present invention to provide a
`multiplexer, for transmitting/receiving central office switch
`communications from/to a first central office switch to/from
`a second central office switch, the multiplexer utilizing a
`high bandwidth data network for communicating. The mul(cid:173)
`tiplexer includes trunk interface logic and network transla(cid:173)
`tion logic. The trunk interface logic is coupled to the first
`central office switch via a central office switch trunk, and
`receives/transmits the central office switch communications
`from/to the first central office switch. The network transla-
`tion logic is coupled to the trunk interface logic. The
`network translation logic translates the central office switch
`communications to/from data network communications, so
`that the central office switch communications may be trans-
`25 ferred over the high bandwidth data network to/from the
`second central office switch, thereby providing all channels
`of the central office switch trunk between the first and
`second central office switches.
`An advantage of the present invention is that telephone
`service providers can utilize packet-switched technology to
`implement a Tl(El) trunk without having to change out their
`existing Tl(El) central office switches.
`Another object of the present invention is to provide
`Tl(El)-to-IP multiplexer that interfaces to a TI(El) central
`office switch but implements a Tl(El) carrier link over a
`high bandwidth data network.
`In another aspect, it is a feature of the present invention
`to provide an apparatus for transmitting telecommunications
`frames between telecommunications switches via a high
`bandwidth data network. The apparatus has a plurality of
`telecommunications interface ports, network translation
`logic, and a network interface port. The plurality of tele(cid:173)
`communications interface ports are each configured to trans(cid:173)
`mit and receive frames associated with a corresponding
`telecommunications trunk, where the corresponding tele-
`communications trunk interconnect two of the telecommu(cid:173)
`nications switches. The network translation logic is coupled
`to the plurality of telecommunications interface ports. The
`50 network translation logic translates outgoing frames into
`outgoing data packets for transmission over the high band(cid:173)
`width data network, and translates incoming data packets
`into incoming frames for distribution to the plurality of
`telecommunications interface ports. The network interface
`55 port is coupled to the network translation logic. The network
`interface port provides full-duplex routing of the outgoing
`data packets and the incoming data packets over the high
`bandwidth data network, where the full-duplex routing
`enables all channels of the corresponding telecommunica-
`60 tions trunk to interoperate between the telecommunications
`switches.
`In a further aspect, it is a feature of the present invention
`to provide a telecommunications carrier multiplexer, for
`providing trunk signals between telecommunications
`65 switches, where the trunk signals are transmitted over a
`packet-switched data network. The telecommunications car(cid:173)
`rier multiplexer includes trunk interface logic, network
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`Pet., Exh. 1004, p. 11
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`US 6,459,708 Bl
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`telecommunications signals, and high speed data networks
`for the transmission of data signals.
`FIG. 2 is a block diagram illustrating how elements within
`a present day central office switch are used to convert analog
`telecommunications signals to digital Tl carrier frames.
`FIG. 3 is a timing diagram depicting El frames being
`continuously transmitted over an El trunk as compared to
`packet-switched data being transmitted over both a 100
`Mbps packet-switched data network.
`FIG. 4 is a block diagram of a system according to the
`present invention for providing Tl trunk interconnections
`between Tl telecommunications switches via a high band(cid:173)
`width data network.
`FIG. 5 is a block diagram illustrating a Tl(El)-to-IP
`multiplexing apparatus according to the present invention.
`FIG. 6 is a block diagram providing details of network
`translation logic within a Tl(El)-to-IP multiplexer.
`FIG. 7 is a diagram illustrating the composition of a Tl
`trunk packet according to the present invention for trans(cid:173)
`mission over a high speed Ethernet network.
`FIG. 8 is a diagram depicting the structure of an appli(cid:173)
`cation header for a Tl frame packet according to the present
`invention.
`FIG. 9 is a flow chart illustrating a method according to
`the present invention for transmitting Tl trunk data over a
`high speed data network.
`
`DETAILED DESCRIPTION
`
`10
`
`5
`translation logic, and network interface logic. The trunk
`interface logic transmits and receives trunk frames corre(cid:173)
`sponding to a particular telecommunications trunk, where
`the particular trunk interconnects a first telecommunications
`switch and a second telecommunications switch. The net(cid:173)
`work translation logic is coupled to the trunk interface logic
`and translates the trunk frames associated with the first and
`second telecommunications switches into network packets
`for transmission over the high bandwidth data network. The
`network translation logic has application envelope logic that
`appends a corresponding application header to each of the
`trunk frames to form a plurality of application packets,
`where the corresponding application header provides control
`data that enables transmission of a corresponding trunk
`frame. The network interface logic is coupled to the network 15
`translation logic and provides full-duplex routing of the
`network packets over the data network. Each of the network
`packets has an application packet set, comprising those of
`the application packets that are generated during a 250-
`microsecond interval. Each of the network packets also has 20
`an IP header, appended to the application packet set to form
`an IP datagram, that provides IP network routing informa(cid:173)
`tion for the application packet set.
`In yet another aspect, it is a feature of the present
`invention to provide a telecommunications switch intercon- 25
`nection apparatus. The telecommunications switch intercon(cid:173)
`nection apparatus includes a trunk frame multiplexer and a
`data network router. The trunk frame multiplexer receives
`trunk frames from a source central office switch, and trans(cid:173)
`lates the trunk frames into network packets. The data net- 30
`work router is coupled to the trunk frame multiplexer. The
`data network router transmits the network packets over a
`high speed data network, where the network packets are
`transmitted in such a manner as to effect transmission of the
`trunk frames from the source central office switch to a 35
`destination central office switch.
`Another advantage of the present invention is that tele(cid:173)
`phone service providers can employ unused bandwidth on
`their packet-switched networks to carry Tl (El) trunk data.
`Yet a further object of the present invention is to provide a
`method for sending Tl(El) signals between Tl(El) switches
`that utilizes a packet-switched network to deliver Tl frames
`to their intended destination.
`In yet a further aspect, it is a feature of the present
`invention to provide a method for interconnecting central 45
`office switches via a high bandwidth data network. The
`method includes receiving telecommunications frames from
`a source central office switch for delivery to a destination
`central office switch, translating the telecommunications
`frames into a plurality of network data packets and trans- 50
`mitting the plurality of network data packets over the high
`bandwidth data network, and converting the plurality of
`network data packets back into the telecommunications
`frames and providing the telecommunication frames to the
`destination central office switch.
`Yet a further advantage of the present invention is that
`multiple Tl(El) trunks can be added between a number of
`central office switches over the same packet-switched net(cid:173)
`work medium.
`
`In view of the above background on techniques for
`transmitting Tl/El telecommunications signals between
`central office switches, several related art examples will now
`be discussed with reference to FIGS. 1 through 3. These
`examples illustrate the problems associated with increasing
`the number of telecommunications trunks between telecom-
`munications switches. More specifically, present day tele(cid:173)
`phone service providers maintain Tl/El equipment to pro(cid:173)
`vide for the transmission of telecommunications signals
`40 between Tl/El switches, and they are beginning to provide
`packet-switched network equipment for the transmission of
`data signals between computer devices connected to a high
`bandwidth packet-switched network. In spite of the trend
`toward the eventual elimination of Tl/El networks
`altogether, telephone service providers must continue to use
`the more expensive Tl/El equipment to provide trunks
`between switches, primarily because their investment in
`Tl/El equipment within the switches is substantial; the
`incremental cost of providing additional Tl/El trunk
`devices is less than that which would otherwise be required
`to completely change over a switch from Tl/El technology
`switching equipment to packet-switched technology switch(cid:173)
`ing equipment. Following this discussion, a detailed descrip(cid:173)
`tion of the present invention will be provided with reference
`55 to FIGS. 4 through 9. The present invention solves the
`above-noted problems in that it provides an apparatus and
`method that allows telephone service providers to add Tl/El
`telecommunications trunks between switches without hav(cid:173)
`ing to utilize a Tl/El technology network. Instead, a packet
`60 switched network is used to carry the Tl/El signals between
`switches. The Tl/El signals are translated into network data
`packets and these network packets are then transmitted over
`the service provider's existing high speed packet-switched
`data network.
`Now referring to FIG. 1, a diagram 100 is presented
`illustrating how present day voices switches employ Tl/El
`trunks for the transmission of telecommunications signals
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`These and other objects, features, and advantages of the
`present invention will become better understood with regard
`to the following description, and accompanying drawings
`where:
`FIG. 1 is a diagram illustrating how present day central
`office switches employ Tl trunks for the transmission of
`
`Pet., Exh. 1004, p. 12
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`25
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`7
`and how in conjunction they employ high speed data net(cid:173)
`works for the transmission of data. The diagram 100 depicts
`three central office switches 101 at locations A, B, and C.
`Telephones 102 and modems 104 are connected to central
`office switches 101 A and B. Telephones 102 are connected
`to central office switch B 101. The central office switches
`101 are interconnected by Tl trunks 110, or higher speed
`trunks 110 based upon the Tl protocol. The diagram 100
`also shows that two of the three central office switches 101
`are each connected to a router 115. Each of the routers 115 10
`is connected to a high speed data network 120. In addition,
`the diagram 100 shows two other data network devices 121
`connected to the high speed data network 120. These two
`data network devices 121 could be embodied as routers 121
`for network traffic or they 121 could be data servers 121 with 15
`embedded routing equipment which are directly accessed
`over the network 120.
`Operationally, telephones 102, modems 104, and other
`telecommunications devices (not shown) such as facsimile
`machines typically transmit and receive analog voice signals
`when communicating with a corresponding central office
`switch 101. Generally, these central office switches 101 are
`geographically located within a few miles of the telephonic
`devices 102, 104 because analog signals degrade over even
`short distances. The central office switch 101 is the primary
`point at which analog telecommunications devices 102, 104
`interface to the public switched telephone network (PS1N).
`One skilled in the art will appreciate that though there are
`devices such as ISDN modems (not shown) and DSL
`modems (not shown) that provide a digital interface to the
`PSTN, the vast majority of telephonic devices 102, 104
`interface to the PSTN using analog signals. In addition,
`although for clarity purposes FIG. 1 only depicts two
`telephones 102 connected to each of the PS1N switches 101,
`one skilled in the art will appreciate that PSTN switches 101
`have the capacity to interface to thousands of telecommu(cid:173)
`nications devices 102, 104.
`When a call is placed from a telephone 102 at point A to
`a telephone 102 at point B, the central office switch 101 at
`point A routes the telecommunications signals provided by
`the telephone 101 at point A to the central office switch 101
`at point B by partially decoding the destination telephone
`number provided by the telephone 102 at point A Central
`office switch B 101 further decodes the destination tele(cid:173)
`phone number to establish a full-duplex connection between
`the two telephones 102. More specifically, a full-duplex
`connection is a connection in which telecommunications
`sig