(12) United States Patent
`LaPier et al.
`
`US006333931B1
`(10) Patent No.:
`US 6,333,931 B1
`(45) Date of Patent:
`*Dec. 25, 2001
`
`-
`
`2- - -->
`
`Ilê el al. .........................
`
`5,828,666 * 10/1998 Focsaneau et al. .................. 370/389
`(54) METHOD AND APPARATUS FOR
`5,862,339 * 1/1999 Bonnaure et al. ................... 709/227
`INTERCONNECTING A
`tº º 'º. ?º
`CIRCUIT-SWITCHED TELEPHONY
`Nº 5,987,118 * 11/1999 Dickerman et al. ................. 379/264
`THEREOF
`K,
`6,021,126 * 10/1998 White et al. ......................... 370/352
`6,084,892 * 7/2000 Benash et al. ....................... 370/701
`6,111,893 * 8/2000 Volfsun et al. ...................... 370/466
`6,112,305 * 8/2000 Dancs et al. ......................... 713/156
`-
`-
`* cited by examiner
`Primary Examiner—Chau Nguyen
`Assistant Examiner—Jasper Kwoh
`(74) Attorney, Agent, or Firm—Hickman Palermo Truong
`& Becker LLP, Christopher J. Palermo
`p
`(57)
`ABSTRACT
`
`e
`
`e
`e
`-
`(75) Inventors: º; º, Nº. NJ
`; Davi
`. Oran, Acton,
`(US); Clay H. Neighbors, Reston;
`Khaled A. Gouda, Herndon, both of
`VA (US); Andrew Adamian, Potomac,
`MD (US)
`-
`(73) Assignee: Cisco Technology, Inc., San Jose, CA
`(US)
`This patent issued on a continued pros- A method and apparatus are disclosed for interconnecting &l
`ecution application filed under 37 CFR
`circuit-switched telephone network and a packet-switched
`1.53(d), and is subject to the twenty year tº:º for . among º A. sº
`patent term provisions of 35 U.S.C.
`tru? of a Circuit-SWitched te epnone network IS couple, to
`154(a)(2)
`a signaling access server that is also coupled to a signaling,
`-
`management and control network. One or more voice trunks
`Subject to any disclaimer, the term of this
`of the telephone network are coupled to one or more network
`patent is extended or adjusted under 35
`acceSS ServerS, which &l?º also coupled to the control network
`to thereby receive instructions from the signaling access
`U.S.C. 154(b) by 0 days.
`h #.
`twork
`from th 1
`1 led t
`server. I ne network access servers are also coupled to a
`"...º.º.º.º.º.º.
`server can receive call setup messages and other messages in
`standard telephone network protocol formats and convert
`them into call setup messages in a special protocol for
`communications between the signaling access server and the
`network access servers. The signaling access server can
`instruct the network access servers to establish a call,
`containing voiceband information such as modem-based
`data calls, from the voice trunks to the data network.
`Accordingly, the public switched telephone network and the
`Internet may be interconnected and may inter-communicate
`without modifying the protocols of either one.
`
`(*) Notice:
`
`(21) Appl. No.: 09/221,912
`(22) Filed:
`Dec. 28, 1998
`7
`(51) Int. Cl." ….........…..... H04Q 11/00
`(52) U.S. Cl. ........................... 370/385; 370/410; 370/352
`(58) Field of Search ..................................... 370/352–563,
`370/385, 466, 467, 410, 522; 379/88.17,
`202, 201.01–201.05, 201.11, 201.12, 202.01,
`203.01; 348/14
`
`(56)
`
`e
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,793,771 * 8/2000 Darland et al. ...................... 370/467
`
`19 Claims, 23 Drawing Sheets
`
`20
`
`Signaling Access
`Server
`
`2-- 112
`
`Signaling
`Trunks
`
`CCS7
`
`L->
`
`X.
`
`22
`
`
`
`16
`
`
`
`|P Control?
`Management
`NetWork
`
`Bright House Networks – Ex. 1058, Page 1
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 1 of 23
`
`US 6,333,931 B1
`
`SuÐAuÐS#7
`
`
`
`
`
`
`
`Bright House Networks – Ex. 1058, Page 2
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 2 of 23
`
`US 6,333,931 B1
`
`FIG. 1B
`
`
`
`
`
`
`
`114
`Tandem Switch
`
`116
`-
`Local Switch
`
`
`
`112
`Signaling Access
`Server
`
`1.18a.
`NetworkACCess
`Server
`
`1.18a
`
`NetworkAccess 5–
`Server
`
`1.18a
`NetWOrkACCess -—
`Server
`
`
`
`
`
`108
`
`
`
`1O7
`
`120
`Router
`
`124
`NetWork
`Service Provider
`
`Bright House Networks – Ex. 1058, Page 3
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 3 of 23
`
`US 6,333,931 B1
`
`
`
`|XC/CLEC
`Tandem/Local
`Switch
`
`Bright House Networks – Ex. 1058, Page 4
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 4 of 23
`
`US 6,333,931 B1
`
`|CP Data
`
`8 |
`
`Signaling/Management/Control
`|
`
`Z || ||
`
`fy
`ul-IN
`Q
`
`|
`
`*l
`
`º
`
`|
`
`
`
`
`
`Bright House Networks – Ex. 1058, Page 5
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 5 of 23
`
`US 6,333,931 B1
`
`Z || ||
`
`|CP Data
`
`Signaling/Management/Control
`
`No.||||||
`
`
`
`
`
`ZOZ
`
`|N| || ||
`
`Bright House Networks – Ex. 1058, Page 6
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 6 of 23
`
`US 6,333,931 B1
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`2009-996-807
`
`972
`
`Bright House Networks – Ex. 1058, Page 7
`
`

`

`U.S. Patent
`
`
`
`908
`
`Bright House Networks – Ex. 1058, Page 8
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 8 of 23
`
`US 6,333,931 B1
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Bright House Networks – Ex. 1058, Page 9
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 9 of 23
`
`US 6,333,931 B1
`
`FIG. 5
`
`
`
`502
`
`Undefined
`
`504 - Create
`
`Delete
`
`506
`
`Install Busy
`/*
`Cause IS = Command IS
`
`512
`\\
`
`
`
`508
`
`*
`
`512
`
`Delete
`Cause OOS=Command DOS
`
`528 N
`
`Cause OOS=
`Command DO
`
`
`
`
`
`
`
`OOS/Cause OOS=Config
`
`Bright House Networks – Ex. 1058, Page 10
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 10 of 23
`
`US 6,333,931 B1
`
`FIG. 6
`
`602
`
`SERVICE(COT) from SAS
`w
`DSO Capable of requested
`No 2.
`COT function?
`* \
`|
`s
`Yes
`COT yº.
`* ,
`- 2 Send SERVICEACKCOTenabled)
`612
`
`
`
`
`
`|
`
`Send SERVICEACK
`(COTfailed to SAS
`2
`
`
`
`614
`
`COT Active
`
`628
`
`626
`
`RELEASE from SAS
`SETUP from SAS
`
`622
`
`Send RELEASE
`| COMPLETE(resource
`failure) to SAS
`
`| — — — - - - -
`
`Send CALL
`PROCEEDING to SAS
`
`618 –
`|
`| Send CONNECT to SAS
`–––––––––
`Ž
`YS.
`624
`S Resources (e.g. DSP)
`{
`available for call?
`P
`620
`
`|
`|
`
`No
`
`Bright House Networks – Ex. 1058, Page 11
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 11 of 23
`
`US 6,333,931 B1
`
`FIG. 7A
`
`702
`
`
`
`706
`
`CALL PROCEEDING
`
`SS7
`SSP/STP
`
`
`
`NAS
`
`716
`
`Conversation
`
`
`
`
`
`
`
`
`
`
`
`Bright House Networks – Ex. 1058, Page 12
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 12 of 23
`
`US 6,333,931 B1
`
`
`
`SS7
`SSP/STP
`
`Bright House Networks – Ex. 1058, Page 13
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 13 of 23
`
`US 6,333,931 B1
`
`FIG. 7C
`
`
`
`SS7
`SSP/STP
`
`Bright House Networks – Ex. 1058, Page 14
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 14 of 23
`
`US 6,333,931 B1
`
`FIG. 8A
`
`
`
`Conversation
`
`SS7
`SSP/STP
`
`Bright House Networks – Ex. 1058, Page 15
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 15 of 23
`
`US 6,333,931 B1
`
`FIG. 8B
`
`
`
`Conversation
`
`SS7
`SSP/STP
`
`806
`
`RELEASE COMPLETE] NAS
`
`Bright House Networks – Ex. 1058, Page 16
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 16 of 23
`
`US 6,333,931 B1
`
`
`
`SS7
`SSP/STP
`
`IAM (WCOT Indication)
`
`wº n
`
`8
`
`MAINTENANCE
`
`Bright House Networks – Ex. 1058, Page 17
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 17 of 23
`
`US 6,333,931 B1
`
`G. 8D
`FI
`
`20
`
`1 12
`
`Z
`
`N
`
`.
`
`716
`
`AM (WCOT Indication
`
`COT (Failure)
`
`814
`
`MAINTENANCE
`(COT On)
`
`MAINTENANCE
`ACK (COT On)
`
`MAINTENANCE
`(COT Off)
`
`MAINTENANCE
`ACK (COT Off)
`
`SS7
`SSP/STP
`
`SAS
`
`MAINTENANCE
`(COT On)
`
`NAS
`
`82 8
`
`COT (Failure)
`
`MAINTENANCE
`ACK (COT On)
`
`MAINTENANCE
`(COT Off)
`
`Repeat CCR
`Sequence NTimes
`
`
`
`MAINTENANCE
`ACK (COT Off)
`
`118
`830 - 832
`
`Alarm: COT Failure
`
`Bright House Networks – Ex. 1058, Page 18
`
`

`

`Bright House Networks – Ex. 1058, Page 19
`
`

`

`U.S. Patent
`
`US 6,333,931 B1
`
`
`
`
`
`
`
`
`
`Bright House Networks – Ex. 1058, Page 20
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 20 of 23
`
`US 6,333,931 B1
`
`FIG. 11
`
`118
`
`1112
`
`1106
`
`Global
`NAS
`Configuration
`
`1104
`
`|
`
`|
`
`1108
`
`y Faults + Measurements
`
`EMS for NAS
`
`SNMP
`Agent
`
`1100 TSA
`
`
`
`
`
`
`
`
`
`1101
`
`
`
`(Local or KT) Common
`EMS
`Platform
`
`1110
`
`1122
`
`912
`
`1
`12
`
`Configuration
`
`–
`
`1124
`
`Agent
`
`SAS
`
`
`
`1102
`
`1114
`
`
`
`
`
`Global
`SAS
`Configuration
`
`FTP
`| Download
`\
`1118
`
`1116
`
`Configuration
`
`Bright House Networks – Ex. 1058, Page 21
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 21 of 23
`
`US 6,333,931 B1
`
`FIG. 12
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`1200
`
`Dial Application
`
`Call Control API/SPI
`
`NAS/SAS
`Signaling
`Protocol
`
`
`
`Voice/FAX
`Service
`Provider
`
`
`
`Service
`Provider
`
`DSO/Trunk
`Service
`Control
`
`
`
`
`
`|OS Kernel
`
`
`
`
`
`P Routing
`
`
`
`DSP Complex (Modems, Voice/Fax)
`
`
`
`///
`
`Voice NetWork Trunks
`
`20
`
`Bright House Networks – Ex. 1058, Page 22
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 22 of 23
`
`US 6,333,931 B1
`
`
`
`218
`
`1300
`
`FIG. 13
`
`1322
`
`1324
`
`MAIN
`MEMORY
`1306
`
`STORAGE
`DEVICE
`1308
`
`1302
`
`1310
`
`:
`
`Bright House Networks – Ex. 1058, Page 23
`
`

`

`U.S. Patent
`
`Dec. 25, 2001
`
`Sheet 23 of 23
`
`US 6,333,931 B1
`
`FIG. 14
`
`
`
`I/O SUBSYSTEM
`905
`
`|/O Channel
`- Controller 904A-1
`
`I/O Channel
`Contoller 904A-2
`
`I/O Channel
`Controller 904A-3
`
`Originating Protocol
`Adapter 1412
`
`External Protocol
`Adapter 1414
`
`Terminating Protocol
`Adapter 1416
`
`Origination
`Call Control
`1422
`
`g
`Universal Call
`Model 1424
`
`Terminating
`Call Control
`1426
`
`Call Context 1428
`
`Bright House Networks – Ex. 1058, Page 24
`
`

`

`1
`METHOD AND APPARATUS FOR
`INTERCONNECTING A CIRCUIT
`SWITCHED TELEPHONY NETWORK AND A
`PACKET-SWITCHED DATA NETWORK, AND
`APPLICATIONS THEREOF
`
`FIELD OF THE INVENTION
`The present invention generally relates to telecommuni
`cations. The invention relates more specifically to intercon
`necting a circuit-switched telephone network to a packet
`switched data network, and methods of using the
`interconnected networks.
`
`BACKGROUND OF THE INVENTION
`The public switched telephony network (PSTN) is made
`up of carriers who have agreements to interconnect with one
`another and switch calls to among one another. The PSTN
`comprises numerous switching systems, which are stored
`program controlled computers comprising line terminations.
`The switching systems connect to other switching systems,
`forming indirect links from customer premises to customer
`premises around the world.
`In a common channel signaling (CCS) network, switching
`systems interconnect using bearer channels and signaling
`channels. Bearer channels generally are 64 kbit/second
`channels that carry voice traffic such as modem calls.
`Signaling channels carry call information in a separate
`network; this is known as out-of-band signaling because call
`signaling information is communicated outside the audible
`voice band of calls. ITU Recommendation Q.700 describes
`this type of PSTN in detail.
`Only carriers may connect to the signaling network.
`However, as a result of national and international deregu
`lation of telephone systems, many new carriers are entering
`or are about to enter the field. For example, in the United
`States, in the past there have been approximately seven (7)
`major signaling carriers and numerous independent carriers,
`but in the future, there will be many new local exchange
`carriers. Internet Service Providers (ISPs), for example, are
`expected to rush into the local exchange switching market.
`In a regulated environment, the major signaling carriers
`could establish common standards and rely on trust of one
`another to ensure that proper signals were carried in the
`signaling network. In a deregulated environment, the sig
`naling network is perceived as a less trustworthy environ
`ment. In particular, in the past, the physical security of SS7
`switching facilities provided the primary overall security of
`an SS7 switching network. Now, there is less assurance that
`new carriers will maintain the same level of physical facility
`security that the major carriers have enforced in the past.
`Further, in the deregulated environment, a carrier cannot
`be trusted to connect to the network and use it in a proper
`manner. For example, a carrier could generate calls for no
`reason. A carrier could claim to have reachability to another
`location when in fact it doesn’t have that capability. A carrier
`could express state information about its circuits incorrectly.
`A carrier could generate Initial Address Messages to distant
`switches and then wait for them to time out. All these
`operations are improper and potentially harmful to other
`network elements and to the private data networks that are
`connected to such network elements.
`In data networks, firewalls are available that are based on
`UNIX computer systems, and may operate in standalone
`fashion or are integrated into routers. Firewalls can be used
`to selectively admit or deny data packets based on rules or
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`US 6,333,931 B1
`
`2
`policies. Such firewalls, however, cannot be used in SS7
`telephone networks or their component systems because
`their hardware and software is incompatible. For example,
`lower SS7 messaging layers require unique firmware and
`hardware for terminating trunks. Further, SS7 is a message
`oriented protocol that requires the use of special messages
`for graceful startup and shutdown of links. These messages
`are not supported in available firewalls.
`Accordingly, there is a need to improve signaling security
`and data channel security between signaling network enti
`ties.
`In particular, there is a need to protect internetworks,
`LANs and WANs from undesirable, undefined, or malicious
`signals and messages originating in local exchange carriers
`or other carriers outside such data networks.
`There is also a need for a system and method that can
`interconnect a data network, and servers thereof, to a circuit
`switched telephony network that uses time-division multi
`plexed signaling, for a variety of purposes. In particular,
`there is a need for a system and method that can interconnect
`a data network to a circuit-switched telephony network that
`uses Signaling System 7 protocols for signaling.
`SUMMARY OF THE INVENTION
`The foregoing needs and objects, and other needs and
`objects that will become apparent from the following
`description, are fulfilled by the present invention, which
`comprises, in one aspect a telecommunications apparatus
`that can interconnect a circuit-switched telephone network
`and a packet-switched data network to enable communica
`tion among the networks. The apparatus has a first server
`coupled to a signaling trunk of the telephone network to
`interchange call signaling messages therewith, and coupled
`to a control network. One or more second servers each are
`coupled to a voice trunk of the telephone network to
`communicate voice-band information thereon, and coupled
`to receive instructions from the first server through the
`control network, and coupled to the data network to com
`municate data thereon. First and second software compo
`ments are executed by and controlling the first server and the
`second server, respectively, and interact cooperatively to
`establish a call originating in the telephone network and
`containing voiceband information and terminating in the
`data network, based on call signaling information received
`from the signaling trunk by the first server.
`One feature of this aspect is that the first and second
`software components interact cooperatively to establish a
`call originating at one of the second servers and containing
`voiceband information and terminating in the telephone
`network, based on call signaling information generated by
`the first server and provided on the signaling trunk.
`Another feature is that the second servers are coupled to
`the data network by an Internet Protocol (IP) backbone
`apparatus, and the second servers are coupled to the first
`server and to a management network by the control network,
`and the control network, the management network, the first
`server, and the second server communicate using IP
`In another feature, the signaling trunk and the voice trunk
`originate in a Common Channel Signaling telephone net
`work. Another feature is that the signaling trunk is a Sig
`maling System 7 (SS7) trunk, and the data network is a
`global, packet-switched network that operates using Internet
`Protocol (IP) and Transmission Control Protocol (TCP).
`According to another feature, the signaling trunk is coupled
`to a Signal Transfer Point of the telephone network and each
`of the second servers is coupled to receive the voiceband
`information from a switch of the telephone network.
`
`Bright House Networks – Ex. 1058, Page 25
`
`

`

`3
`In yet another feature, the signaling trunk is coupled from
`the first server to a digital cross connect apparatus that is
`coupled to the telephone network, and each of the second
`servers is coupled by an associated voice trunk to the digital
`cross connect apparatus to receive the voiceband informa
`tion therefrom. Still another feature is that the apparatus
`includes a cross-connect apparatus logically coupled
`between the telephone network and both the signaling trunk
`and the voice trunk, and means, coupled between the sig
`naling trunk and the first server, for communicating call
`routing signals from the digital cross-connect apparatus
`through the signaling trunk and to the first server. The
`software components are configured to receive call signaling
`messages from the means for communicating and over the
`control network, and to communicate the call signaling
`messages back over the control network to the second
`Serve? S.
`Still another feature is that the software components
`comprise instructions which, when executed by the first
`server, cause the first server to carry out the steps of
`receiving a call setup message from the telephone network
`that contains a master telephone number; sending a respon
`sive message to the telephone network that contains a
`specific telephone number associated with one of the second
`servers; and setting up a call between the telephone network
`and one of the second servers that is associated with the
`specific telephone number. A related feature is that the
`software components further comprise instructions which,
`when executed by the first server, cause the first server to
`carry out the steps of receiving a call offer message from the
`30
`telephone network that contains the specific telephone num
`ber.
`Another related feature is that the software components
`further comprise instructions which, when executed by the
`first server, cause the first server to carry out the steps of
`determining that the one of the second servers has insuffi
`cient resources to set up the call; communicating a call
`release message from the first server to the telephone
`network; communicating a second responsive message from
`the first server to the telephone network, wherein the second
`responsive message contains a second specific telephone
`number that is associated with a second one of the second
`Serve? S.
`
`10
`
`15
`
`20
`
`25
`
`35
`
`40
`
`US 6,333,931 B1
`
`4
`FIG. 5 is a state diagram of processes carried out by a
`Signaling Access Server;
`FIG. 6 is a state diagram of processes carried out by the
`Network Access Server to perform continuity testing;
`FIG. 7A is a call flow diagram showing messages com
`municated in carrying out certain call processing functions;
`FIG. 7B illustrates messages exchanged as in FIG. 7A,
`with an alerting function applied to the call;
`FIG. 7C illustrates messages exchanged as in FIG. 7A,
`when establishing a call that is originated by a Network
`Access Server;
`FIG. 8A illustrates messages exchanged in clearing or
`completing a call;
`FIG. 8B illustrates messages exchanged when a call is
`cleared from the Network Access Server side of the con
`nection;
`FIG. 8C illustrates messages exchanged in establishing a
`call originated by the telephone network and with successful
`continuity testing;
`FIG. 8D is a diagram of messages communicated among
`the network, Signaling Access Server, and Network Access
`Server in setting up a call, originated at the network, with
`continuity testing enabled but when continuity fails;
`FIG. 9 is a block diagram of internal components of
`Signaling Access Server including the means of intercom
`munication among the components and the output produced
`by the components;
`FIG. 10 is a block diagram of a process of converting call
`detail records;
`FIG. 11 is a block diagram of an integrated Element
`Management System;
`FIG. 12 is a block diagram of an embodiment of software
`elements that may be executed by Network Access Server;
`FIG. 13 is a block diagram of hardware components of a
`Signaling Access Server;
`FIG. 14 is a block diagram of software elements relating
`to protocol conversion that may be executed by a Signaling
`Access Server.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`A method and apparatus for interconnecting a circuit
`switched telephony network and a packet-switched data
`network are described. In the following description, for the
`purposes of explanation, numerous specific details are set
`forth in order to provide a thorough understanding of the
`present invention. It will be apparent, however, to one
`skilled in the art that the present invention may be practiced
`without these specific details. In other instances, well-known
`structures and devices are shown in block diagram form in
`order to avoid unnecessarily obscuring the present inven
`tion.
`
`System Overview
`The present disclosure will describe an invention which,
`in one embodiment, provides a distributed system for inter
`connecting one or more Network Access Servers, which are
`coupled to a data network such as the Internet, to a circuit
`switched Time Division Multiplexing telephone network
`that uses Signaling System 7 protocols for signaling. The
`interconnection is achieved, in part, using a protocol con
`verter that is configured as a Signaling Access Server
`(“SAS”) and that interworks with a Network Access Server
`(“NAS”). “Interworks” means, for example, that the Signal
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The present invention is illustrated by way of example,
`and not by way of limitation, in the figures of the accom
`panying drawings and in which like reference numerals refer
`to similar elements and in which:
`FIG. 1A is a block diagram of a preferred embodiment of
`a call monitoring system coupled to a telephony network and
`a data network;
`FIG. 1B is a network diagram of further details of the
`system of FIG. 1A;
`FIG. 1C is a block diagram of the logical placement of a
`preferred embodiment of the system of FIG. 1A;
`FIG. 2A discloses an alternate configuration of the system
`of FIG. 1C:
`FIG. 2B discloses another alternate configuration of the
`system of FIG. 1C:
`FIG. 2C is a block diagram of a process of routing a call
`using the system of FIG. 1A;
`FIG. 3 is a block diagram of a configuration of multiple
`Network Access Servers and a Signaling Access Server;
`FIG. 4 is a state diagram of processes executed by a
`Network Access Server in processing calls;
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`ing Access Server commands and manages the Network
`Access Servers using a signaling and control network; it is
`also possible for the NAS to place outgoing calls through the
`SAS to an SS7 network.
`FIG. 1A is a block diagram of the logical placement of a
`preferred embodiment of a call monitoring system 2 within
`a telephony network 4 and a data network. System 2
`comprises one or more Network Access Servers 118, located
`at one or more service provider points of presence. Each
`Network Access Server 118 is coupled to and provides
`termination for a pre-determined number of voice network
`trunks 10. Each Network Access Server 118 has a first
`Internet Protocol network interface coupled to a data net
`work backbone 14 and a second Internet Protocol network
`interface coupled to the service provider’s management,
`signaling and control network 12. There may be more than
`two IP network interfaces so that the system supports
`redundant IP links for communication between the NAS and
`SAS.
`The data network backbone 14 is coupled to an external
`IP data network 122, such as the Internet. The data network
`backbone is owned and operated by the service provider,
`which may be an Internet Service Provider. The service
`provider’s management, signaling and control network 12 is
`generally maintained securely, according to telephone indus
`try standards, and is generally more trusted than the IP data
`network 122.
`The voice network trunks 10 may originate from any type
`of Time Division Multiplexing network infrastructure, and
`may be ISDN Primary Rate Interface trunks, T1 trunks, E1,
`T3, E3, etc. The voice network trunks 10 are matched with
`compatible digital interfaces at each Network Access Server
`118. In the preferred embodiment, the voice network trunks
`10 comprise only bearer channels. Thus, the voice network
`trunks do not carry associated signaling channels. Instead,
`all signaling channels of telephone network 4 terminate at
`Signaling Access Server 112.
`One or more Signaling Access Servers 112 are coupled to
`one or more SS7 signaling trunks 20. Each Signaling Access
`Server 112 terminates the SS7 signaling links and handles
`voice network maintenance messages, as well as call control
`messages. A particular Signaling Access Server 112 may be
`co-located with the Network Access Servers 118, or located
`near a circuit switch or Service Control Point of a telephone
`service provider. One Signaling Access Server 112 may
`provide signaling and call processing services for a large
`number of Network Access Servers 118. Each Signaling
`Access Server 112 may be replicated for redundancy. From
`the point of view of the network 4, each Signaling Access
`Server 112 represents a terminating and originating Service
`Control Point.
`The SS7 signaling trunks 20 may be A-Links, or F-Links
`that have been separated from their associated voice trunks
`and delivered to the Signaling Access Server 112 using
`separate facilities. Alternatively, SS7 signaling may be back
`hauled over voice network trunks 10. In still another
`alternative, the SS7 signaling may be encapsulated by a
`separate apparatus and backhauled over the IP Control/
`Maintenance Network 16.
`The Signaling Access Server 112 communicates with the
`Network Access Servers 118 over the management, signal
`ing and control network 12. The Signaling Access Server
`112 is coupled to the management, signaling and control
`network 12 by connection 22. Preferably, Signaling Access
`Server 112 communicates over the network 12 with Network
`Access Servers 118 using an agreed-upon protocol, which
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`US 6,333,931 B1
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`6
`may be similar to the UDP protocol. Advantageously, only
`layer 3 of the ISDN protocol is needed when the system
`operates using UDP.
`Functions of the Signaling Access Server 112 include SS7
`signaling; carrying out call control in communication with a
`Network Access Server; establishing and managing
`bi-directional calls; fault management; compiling and
`reporting on telephony statistics; implementing custom fea
`tures; and providing call detail accounting.
`Each Network Access Server 118 provides bearer channel
`termination; implements modem pools; provides IP routing;
`implements authentication, authorization, and accounting
`(AAA) functions; generates telephony tones using digital
`signal processors; provides virtual private network manage
`ment; manages faults that occur with bearer channels; and
`compiles and reports on statistical information relating to
`bearer channels. For example, a Network Access Server 118
`may provide routing functions that carry out authentication
`functions and call completion functions. Preferably, each
`Network Access Server 118 has a Q.931 protocol stack for
`use with ISDN Primary Rate Interface (PRI). Each NAS also
`contains a time division multiplexer (TDM) that chooses a
`channel and selects and assigns a free modem from among
`the modems in the NAS. Each NAS may accept a loopback
`circuit, which may be accomplished by installing a driver
`and modifying microcode that controls the TDM so as to
`permit circuits to go into a loopback.
`FIG. 1B is a network diagram of further details of the
`system of FIG. 1A. Signaling Access Server 112 is coupled
`to a local area network or LAN 108 that comprises numerous
`network devices, such as Network Access Servers
`118a–1180. An example of a Network Access Server is the
`Cisco Model AS5300, commercially available from Cisco
`Systems, Inc., San Jose, Calif. Such Network Access Servers
`contain modems or digital signal processors for handling
`data calls communicated between nodes of the LAN 108 and
`external nodes such as server 109.
`FIG. 1B shows an exemplary configuration in which only
`one Signal Transfer Point (STP) 104 of one carrier is
`coupled to Signaling Access Server 112. Thus, there is only
`one external point at which signaling information from
`network 4 can reach Signaling Access Server 112. However,
`many Signaling Access Servers 112 may be connected to
`numerous carriers. In this environment, there is an acute
`need to protect the Signaling Access Server 112, and the
`LAN 108, from malicious or undesirable signaling
`messages, requests, or other information.
`Signaling Access Server 112 communicates using SS7
`messages. The SS7 messages are communicated using a
`stack comprising ISUP format messages, MTP-3 format
`messages, MTP-2 format messages, and MTP-1 format
`messages. The stack may also use TCAP, SCCP, MTP-3,
`MTP-2, and MTP-1 protocols.
`FIG. 1C is a block diagram of the logical placement of a
`preferred embodiment of the system 2 in a telephone net
`work. Signaling Access Server 112 is coupled by an A-link
`to Signal Transfer Point (STP) 104, which may be associated
`with a Competitive Local Exchange Carrier (CLEC) home
`gateway. The Network Access Servers 118 are coupled by
`voice links V to one or more switches such as local switch
`116, tandem switch 114, and tandem/local switch 128. The
`STP104 may be coupled by a B-link to another STP106 that
`is associated with an Incumbent Local Exchange Carrier
`(ILEC) gateway. The STP106 may be coupled to the tandem
`switch 114 and if so, the tandem switch thereby provides
`ILEC access. The STP 104 is also coupled by A-links to the
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`US 6,333,931 B1
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`7
`tandem/local switch 128 and local switch 116. The tandem/
`local switch 128 communicates with an inter-exchange
`carrier and a CLEC where as the local switch 116 is
`associated with the CLEC. In this configuration, the system
`2 emulates an end office switch that terminates calls.
`Signal transfer points 104,106 generally comprise packet
`switches that create a star network for communication of
`signaling information. An STP may carry out global title
`translation and other network-related services. Service con
`trol points, such as SCP 102, carry out network-related
`services, such as global title translation or mapping an
`800-type telephone number to an address or point code. The
`general structure and functions of STPs and SCPs are well
`known in the field.
`In the preferred embodiment, the Signaling Access Server
`112 and Network Access Servers 118 communicate using a
`special signaling protocol. In one embodiment, the special
`signaling protocol is based on Q.931 with certain custom
`enhancements. Alternatively, the communications may
`involve delivering the SS7 signaling directly to the Network
`Access Server and having it operate as an SS7 signaling
`point itself. The preferred embodiment, however, has several
`important advantages, including:
`1. The Network Access Server 118 need not implement
`SS7 protocols, especially certain low-level legacy pro
`tocols such MTP-1 or MTP-2, which are burdensome
`and may require special hardware or firmware.
`2. The Network Access Server 118 can be configured with
`increased capacity (“scaled”) according to the number
`of bearer channels supported in a particular platform. In
`contrast, not all platforms are well suited to the task of
`terminating SS7 signaling.
`3. Configuring the SS7 signaling in a separate platform
`permits aggregation and improved management,
`because the Signaling Access Servers and Network
`Access Servers need not be co-located. In contrast, one
`Signaling Access Server can service many Network
`Access Servers that are in different geographic loca
`tions.
`4. The Signaling Access Server is specialized for signal
`ing termination and conversion. Accordingly, it can be
`more easily optimized for high performance and scal
`ability.
`5. The SAS can provide signal interworking between the
`Network Access Servers and the large number of SS7
`variants