USOO6980564B1
`
`(12) Unlted States Patent
`(10) Patent No.:
`US 6,980,564 B1
`
`Rodriguez et al.
`(45) Date of Patent:
`Dec. 27, 2005
`
`(54) MODULAR DATA COMMUNICATION
`EQUIPMENT SYSTEM
`
`5,550,984 A *
`6,026,086 A *
`
`8/1996 Gelb .......................... 709/245
`2/2000 Lancelot et al.
`............ 370/353
`
`(75)
`
`Inventors: Juan 0. Rodriguez, Alpharetta, GA
`(US); David J. Berman, Swampscott,
`MA (US); James D. Lakin, Roswell,
`GA (US)
`
`* cited by examiner
`.
`.
`Primary Examiner—Bob A. Phunkulh
`(74) Attorney, Agent, or Firm—Withrow & Terranova,
`PLLC
`
`(73) Assignee: Nortel Networks Limited, St. Laurent
`(CA)
`
`(57)
`
`ABSTRACT
`
`( * ) Notice:
`
`Subjecttto any disclaimer, the term Of this
`{)jatsenct lfsixgengedsfi gdjusted under 35
`’
`’
`’
`( ) y
`ays.
`(21) Appl. No.: 09/884,684
`
`(22)
`
`Filed:
`
`Jun. 19, 2001
`
`_
`_
`Related U'S' Appllcatlon Data
`
`A network interface unit includes an interface module for
`translating messages transmitted between one of a family of
`different types of service delivery units. Each type of service
`delivery unit provides a network service that is different than
`the network service provided by the other types of service
`delivery units in the family. The service delivery unit
`connected to the network interface unit processes messages
`received in a first format. The network interface unit thus
`
`(63) Continuation of application No. 09/753,014, filed on
`Jan. 2, 2001, now abandoned.
`
`includes a medium module configured to process data for
`transmission between the given medium and the service
`
`7
`
`................................................. H04J 3/16
`Int. Cl.
`(51)
`....................................... 370/466; 370/419
`(52) US. Cl.
`(58) Fleld of Search ................................ 370/419, 420,
`370/421’ 466’ 467’ 400’ 401; 709/249
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`delivery unit, and the interface module. The medium module
`transmits messages toward the service delivery unit in a
`second format. The interface module is configured to receive
`messages transmitted between the medium module and the
`service delivery unit. The interface module is configured to
`translate messages from the second format
`to the first
`format.
`
`5,251,207 A * 10/1993 Abensour et al.
`
`........... 370/473
`
`27 Claims, 6 Drawing Sheets
`
`26
`
`28
`
`Network interface Unit
`
`
`Service Delivery Unit
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`22
`34
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`
`
`Network
`
`
`
`
`Medium
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`Service
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`Module
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`Module
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`Page 1 of 13
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`VERIZON EXHIBIT 1001
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`VERIZON EXHIBIT 1001
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`US. Patent
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`Dec. 27, 2005
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`Sheet 1 0f 6
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`US 6,980,564 B1
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`Nr.83
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`US. Patent
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`US 6,980,564 B1
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`US. Patent
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`Sheet 6 0f 6
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`US 6,980,564 B1
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`US 6,980,564 B1
`
`1
`MODULAR DATA COMMUNICATION
`EQUIPMENT SYSTEM
`
`PRIORITY
`
`This application is a continuation of and claims priority
`from US. patent application Ser. No. 09/753,014, filed Jan.
`2, 2001, now abandoned, and entitled, “MODULAR DATA
`COMMUNICATION EQUIPMENT SYSTEM.” The dis-
`closure of that application is incorporated herein,
`in its
`entirety, by reference.
`
`FIELD OF THE INVENTION
`
`The invention relates generally to data transmission net-
`works and, more particularly, the invention relates to data
`communication equipment
`for use by data termination
`equipment.
`
`BACKGROUND OF THE INVENTION
`
`Different network services, such as cable television and
`telephone services, traditionally have been developed for
`use over different types of networks. For example, telephone
`services traditionally has been developed around the public
`switched telephone network (the “PSTN”), while cable
`television services traditionally have been developed around
`the cable television network.
`
`To provide a network service, a network access device
`(commonly known to as “Data Communications Equip-
`ment” or “DCE”) commonly is used to connect a network
`device (e.g., a telephone or television) to the network. More
`particularly, the DCE provides network devices known as
`“Data Termination Equipment” (“DTE”) with access to their
`underlying network. For additional information relating to
`DCEs and DTEs, see the family of standards relating to
`recommended standard-232 (often referred to as “RS-232”),
`which is a widely used standard interface approved by the
`Electronic Industries Alliance (“EIA”) for connecting serial
`devices.
`
`The above noted interrelationship between service and
`network type has caused the network service industry to
`develop network access equipment (DCEs) that provides a
`specific service over its corresponding traditional network
`only. Continuing with the above example, the provision of
`cable television services commonly requires use of a cable
`conversion box (“cable box,” which is a type of DCE) that
`provides the direct connection to the cable network. In a
`manner similar to DCEs for other types of networks/ser-
`vices,
`the cable box typically includes medium interface
`circuitry for conforming data transmissions with the speci-
`fications required by cable networks (e.g., the well known
`DOCSIS standards, discussed herein), and service delivery
`circuitry that provides the higher level television services to
`a connected television (i.e., functions perceived by the user
`of the DTE). Among other functions, such service delivery
`circuitry may provide access to a selected set of television
`stations (e.g., based upon a user’s subscription to a cable
`company), and channel mapping functionality that maps a
`cable channel to a channel on the attached television.
`
`In recent years, however, the trend has been to provide a
`single service via any one of numerous different types of
`networks. For example, telephone services currently can be
`delivered via the circuit switched technology in the PSTN,
`or via a broadband network, such as a cable network or fiber
`optic network. Accordingly, a single DCE for use with the
`telephone services must be produced for use with each
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`network/medium type. For example, a separate telephony
`DCE must be developed for use with each of cable networks,
`fiber optic networks, wireless networks, etc .
`.
`.
`. With the
`proliferation of network services and broadband types/uses,
`this requires a rather wide variety of DCEs for each service,
`and for each network type. Although currently necessary,
`this duplication is inefficient, and causes relatively high
`deployment costs for various network services and network
`types.
`
`SUMMARY OF THE INVENTION
`
`In accordance with one aspect of the invention, a network
`interface unit includes an interface module for translating
`messages transmitted between one of a family of different
`types of service delivery units. Each type of service delivery
`unit provides a network service that is different than the
`network service provided by the other types of service
`delivery units in the family. The service delivery unit
`connected to the network interface unit processes messages
`received in a first format. The network interface unit thus
`
`includes a medium module configured to process data for
`transmission between the given medium and the service
`delivery unit, and the interface module. The medium module
`transmits messages toward the service delivery unit in a
`second format. The interface module is configured to receive
`messages transmitted between the medium module and the
`service delivery unit. The interface module is configured to
`translate messages from the second format
`to the first
`format.
`
`In some embodiments, the service delivery unit transmits
`messages in the first format, and the medium module pro-
`cesses messages received in the second format. Accordingly,
`the interface module also is configured for translating mes-
`sages from the first format to the second format.
`All the different types of service delivery units in the
`family may process data in the first format, or only one type
`of service delivery unity may process data in the first format.
`In the latter case, the other types of service delivery units in
`the family process data in different formats. The given
`medium may be a broadband medium, such as fiber optic
`technology, cable technology, or digital subscriber line tech-
`nology. The network service may include at least one of
`telephony, data service, audio service, video service, and
`Virtual Private Network service.
`
`The network unit interface also may include a connector
`for electrically and physically connecting to the service
`delivery unit. The connector is a single size that corresponds
`to the size of connectors on each of the types of service
`delivery units in the family. Among other
`things,
`the
`medium module includes a network physical
`layer and
`media control module. The network interface unit preferably
`is physically separated from the service delivery unit. The
`service delivery unit and network interface unit cooperate to
`act as data communication equipment for data terminal
`equipment.
`In accordance with another aspect of the invention, a
`service delivery unit for providing a network service coop-
`erates with a network interface unit
`to function as data
`
`termination equipment. The network interface unit is one
`type of a plurality of different types of network interface
`units. Each type of network interface unit has connection
`logic for connecting to a network medium that is different
`than the network mediums to which the other types of
`network interface units can connect. The network interface
`
`unit processes messages in a first format. The service
`delivery unit thus includes a network service module that
`
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`US 6,980,564 B1
`
`3
`provides the network service, and an interface module for
`intercepting and translating messages transmitted between
`the network service module and the network interface unit.
`
`The network service module transmits messages toward the
`network interface unit in a second format. The interface
`
`4
`execute various network services over various network
`
`types. Details and illustrative examples are discussed below.
`FIG. 1 schematically shows an exemplary network 10 that
`may be used in connection with illustrative embodiments of
`the invention. The network 10 includes a local network
`
`module is configured to translate messages from the second
`format to the first format.
`
`device 12 that communicates with one or more of a plurality
`of different remote network devices 14 via the Internet 16.
`
`In accordance with other aspects of the invention, a
`modular data communication equipment system includes a
`family of different types of network interface units, a family
`of different types of service delivery units, and an interface
`configured to convert the format of messages transmitted
`between any one type of the network interface units and any
`one type of the service delivery units. Each type of network
`interface unit has connection logic for connecting to a
`network medium that is different than the connection media
`
`to which the other types of network interface units can
`connect. In a similar manner, each type of service delivery
`unit provides a network service that is different than the
`service provided by the other types of service delivery units.
`The network interface units are configured to communicate
`with at least one service delivery unit via formatted mes-
`sages that, as noted above, are converted by the interface.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The foregoing and advantages of the invention will be
`appreciated more fully from the following further descrip-
`tion thereof with reference to the accompanying drawings
`wherein:
`
`FIG. 1 schematically shows an exemplary network that
`may be used in connection with illustrative embodiments of
`the invention.
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`FIG. 2 schematically shows a modular network access
`system configured in accordance with illustrative embodi-
`ments of the invention.
`
`35
`
`FIG. 3 schematically shows the modular network access
`system shown in FIG. 2 in which an interface is located
`solely on a network interface unit.
`FIG. 4 schematically shows the modular network access
`system shown in FIG. 2 in which an interface is located
`solely on a service delivery unit.
`FIG. 5 schematically shows the modular network access
`system shown in FIG. 2 in which an interface is dispersed
`across a network interface unit and a service delivery unit.
`FIG. 6 schematically shows a family of network interface
`units, a family of service delivery units, and their standard
`connectors.
`
`FIG. 7 schematically shows a specific implementation of
`the network access system shown in FIG. 2.
`
`DESCRIPTION OF ILLUSTRATIVE
`EMBODIMENTS
`
`In illustrative embodiments, a network access system
`includes a family of different types of network interface
`units that each can cooperate with any one type of a family
`of different types of service delivery units to act as data
`communication equipment (“DCE”). To that end, each type
`of network interface unit and service delivery unit is both
`modular and functionally independent. Accordingly, any
`type of network interface unit preferably can physically and
`electrically connect with any type of service delivery unit to
`provide complete DCE functionality. The disclosed network
`access system thus is configured to permit commonly used
`data terminal equipment (e.g., an Internet
`telephone) to
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`Among other things, the local network device 12 may be a
`computer system, IP telephone, or network appliance. To
`connect to the Internet 16, the local network device 12 uses
`a network access system 18 (noted above and discussed in
`detail below) to connect to an Internet Service Provider
`(“ISP 20”) via some network medium 22 (also referred to
`herein as “network type 22”). The local network device 12
`and access system 18 are shown as being located at a
`customer’s premises, such as in a single office.
`The network medium 22 can be any known medium
`currently used in the art. Among other types, the network
`medium 22 may be a conventional twisted pair (e.g., tele-
`phone lines used for a Digital Subscriber Line), cable lines,
`fiber optic lines, a wireless medium (e.g., Bluetooth), or
`some combination thereof. As known in the art, data trans-
`missions across each type of network medium 22 must
`comply with a standard protocol. For example, if the net-
`work medium 22 is a cable network,
`then transmission
`across the medium 22 must comply with some accepted
`cable network data transmission standard, such as the “Data
`Over Data-Over-Cable Service Interface Specification.” For
`additional information relating to this standard, see “Data-
`Over-Cable Service Interface Specifications, Radio Fre-
`quency Interface Specification,” which is a cooperative
`effort under the direction of Cable Television Laboratories,
`Inc., with a copyright of 1999 and 2000 and document
`control number SP-RF1v1.1-104-000407, the disclosure of
`which is incorporated herein, in its entirety, by reference.
`This specification is commonly referred to in the art by the
`acronym “DOCSIS.”
`Although the network medium 22 is shown schematically
`as a single element, it may include two or more separate and
`distinct types of network media 22. For example, the net-
`work medium 22 may include a cable network and a separate
`fiber optic network. In such case,
`the access system 18
`provides access to both types of networks.
`FIG. 2 schematically shows additional details of the
`access system 18 shown in FIG. 1. Specifically, the access
`system 18 includes one unit of a family of different types of
`improved network interface units 26 that provide the nec-
`essary physical layer conversions and/or signal processing
`for transmission across a given network medium 22, and one
`unit of a family of different types of service delivery units 28
`that provide the necessary logic for permitting a given
`network service to be performed by the network device 12.
`In addition, the access system 18 also includes a standard
`interface 30 for logically connecting the network interface
`unit 26 with the service delivery unit 28. Details of these
`three different components of the access system 18 are
`discussed below. It should be noted that in some embodi-
`
`ments, the network interface units 26 may be referred to as
`network interface modules. In still other embodiments, the
`service delivery units 28 may be referred to as service
`delivery modules.
`In particular,
`the network interface unit 26 includes a
`medium module 32 having hardware and software for imple-
`menting the appropriate physical layer and medium control
`processes required for transmitting data messages across the
`given network type 22. Stated another way, the medium
`module 32 implements the underlying specification for
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`US 6,980,564 B1
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`5
`transmitting data across the network medium 22 to which it
`is attached. This functionality is independent of the service
`being provided by the service delivery unit 28. The medium
`module 32 may include a single element, or a plurality of
`different devices/modules for implementing the required
`function. By way of example, if the network medium 22 is
`a cable network, then the medium module 32 may include
`the hardware and software for implementing the DOCSIS
`standard (see FIG. 7, discussed below).
`Of course, since the network interface unit 26 is but one
`type in a family of different types of network interface units
`26, then a different type of network interface unit 26 may be
`constructed for each of various different network types 22.
`Accordingly, network interface units 26 can be constructed
`for use with cable networks, twisted pair networks imple-
`menting a digital subscriber line (“DSL”), fiber optic net-
`works, and wireless networks, among others. The appropri-
`ate network interface unit 26 then is selected for use in the
`
`access system 18 based upon the network type 22 to which
`it is connected. In some embodiments (discussed below),
`multiple network interface units 26 can be used in conjunc-
`tion with one or more service delivery units 28 within a
`single access system 18.
`The service delivery unit 28 includes a network service
`module 34 for permitting the local network device 12 to
`execute a network service via the access system 18. As
`discussed in greater detail by example in FIG. 7, the network
`service module 34 includes hardware and/or software to
`process specific messages for implementing a given network
`service across some network. Of course, the network service
`module 34 provides the given service independently of the
`type of network medium 22 to which the access system 18
`is connected. As noted above, examples of the network
`service module 34 and the service delivery units 28 are
`discussed below with reference to FIG. 7.
`
`Each different type of network interface unit 26 may
`process data in a different format than the formats used by
`other types of network interface units 26. More particularly,
`a network interface unit 26 for use with a first network type
`22 may receive and transmit messages within the access
`system 18 in a different format than a network interface unit
`26 that is configured for use with a different network type 22.
`In a similar manner, each different type of service delivery
`unit 28 may process data in a different format than the
`formats used by other types of service delivery units 28. The
`interface 30 thus converts messages transmitted between the
`service delivery unit 28 and the network interface unit 26
`into an appropriate format
`that is understandable to the
`receiving network interface unit 26 or service delivery unit
`28.
`
`FIGS. 3—5 schematically show several different types of
`interfaces 30 that may be used to convert messages for-
`warded between the network interface unit 26 and the
`
`service delivery unit 28. In all such figures, messages are
`schematically shown between the interface 30 and medium
`module 32 as being in a format that is specific to the medium
`module 32 and/or the network interface unit 26. This format
`is referred to herein as being “N.I.U. format.” Conversely,
`messages between the interface 30 and the network service
`module 34 are in a format that is specific to the network
`service module 34 and/or the service delivery unit 28. This
`format is referred to herein as being “S.D.U. format.”
`FIG. 3 schematically shows the interface 30 being entirely
`within the network interface unit 26. In such case, such
`network interface unit 26 transmits messages to the accom-
`panying service delivery unit 28 in a format that the service
`delivery unit 28 can interpret (i.e., the S.D.U. format). In a
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`similar manner, such network interface unit 26 can convert
`messages received from the service delivery unit 28 (i.e.,
`messages in the S.D.U. format) into the N.I.U. format for
`processing by the medium module 32 and other components
`within the network interface unit 26.
`
`FIG. 4 schematically shows the interface 30 being entirely
`within the service delivery unit 28. In such case, such service
`delivery unit 28 transmits messages to the accompanying
`network interface unit 26 in a format
`that
`the network
`
`interface unit 26 can interpret (i.e., in the N.I.U. format). In
`a similar manner, such service delivery unit 28 can convert
`messages received from the network interface unit 26 (i.e.,
`messages received in the N.I.U. format) into the S.D.U.
`format for processing by the network service module 34 and
`other components within the service delivery unit 28.
`For the interfaces 30 in FIGS. 3 and 4 to be operate
`properly,
`they must be preprogrammed to convert from
`specific, predetermined formats of the accompanying net-
`work interface units 26 and service delivery units 28. More
`particularly, the interface 30 must be preprogrammed to be
`usable with one or more different format types of network
`interface units 26 and service delivery units 28. For
`example, the interface 30 in FIG. 3 may be preprogrammed
`to convert messages to/from a network interface unit 26 for
`a cable network, and messages to/from a service delivery
`units 28 providing telephone services.
`Accordingly, such network interface unit 26 can couple
`with any service delivery units 28 providing telephone
`services. Conversely, if such network interface unit 26 is
`coupled with a service delivery unit 28 for providing data
`services,
`then the interface 30 will not properly convert
`messages and thus, the access system 18 will not properly
`operate as a DCE.
`To overcome this potential problem shown by example,
`some embodiments of the interface 30 are configured to be
`compatible with more than one type of network interface
`unit 26 and/or service delivery unit. For example, the above
`exemplary interface 30 of FIG. 3 also may be configured to
`understand and convert messages for service delivery units
`28 that provide any one or more of data services and video
`services. In a similar manner, the interface 30 of FIG. 4 also
`may be configured to understand and convert messages for
`coupled network interface units 26 that are used with any
`one or more of fiber optic networks, DSL networks, and
`various types of wireless networks.
`In some embodiments, a single network interface unit 26
`can be configured to couple with more than one network
`type 22. In a similar manner, a single service delivery units
`28 can be configured to provide more than one network
`service.
`In such case,
`the interface 30 may be prepro-
`grammed to convert messages from multiple network types
`22 to one or more specified network service.
`FIG. 5 schematically shows an access system 18 in which
`the interface 30 is distributed between the network interface
`
`unit 26 and the service delivery unit 28. Such system utilizes
`a standardized format
`to communicate between coupled
`network interface units 26 and service delivery units 28.
`This format preferably is identical for all types of network
`interface units 26 and all types of service delivery units 28.
`Accordingly, any type of network interface unit 26 can
`communicate with any type of service delivery unit, thus
`eliminating the limitations to the embodiments discussed
`above with regard to FIGS. 4 and 5.
`To that end, the network interface unit 26 includes an
`N.I.U. interface 30A that cooperates with an S.D.U. inter-
`face 30B to convert messages to appropriate formats. The
`N.I.U.
`interface 30A converts messages from the N.I.U.
`
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`US 6,980,564 B1
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`7
`format to the standardized format, and from the standardized
`format
`to the N.I.U. format. Accordingly,
`in a manner
`similar to the interfaces 30 shown in FIGS. 3 and 4, the
`N.I.U. interface 30A is preconfigured to operate with the
`particular network medium/media 22 to which the network
`interface unit 26 is connected.
`
`Conversely, the S.D.U. interface 30B converts messages
`from the S.D.U. format to the standardized format, and from
`the standardized format to the S.D.U. format. The S.D.U.
`
`interface 30B thus also is preconfigured to operate with the
`particular network serVice(s) provided by the network ser-
`vice module 34.
`
`In illustrative embodiments, each type of network inter-
`face unit 26 has a physical connector 36 that is a standard-
`ized size to couple with a corresponding standardized sized
`mating connector 38 on each type of service delivery unit
`28. FIG. 6 schematically shows a family of different types of
`network interface units 26, and a family of different types of
`service delivery units 28. Although different, each type of
`network interface unit 26 has an identical type of connector
`36 for connecting with one or more service delivery units 28.
`In a similar manner, each type of service delivery unit 28
`also has an identical type of connector 38 for connecting
`with one or more network interface units 26.
`
`FIG. 7 schematically shows one embodiment of the
`access system 18 shown in FIG. 1. This is but one of many
`different types of access systems 18 that may implement
`illustrative embodiments of the invention and thus, is not
`intended to limit the scope of the invention. Accordingly,
`discussion of this access system 18 is exemplary only. The
`access system 18 of FIG. 7 includes two modular network
`interface units 26A and 26B that both couple with a single
`service delivery unit 28 via a generally shown interface 30.
`Each network interface unit 26A and 26B includes logic for
`coupling with one network type 22, while the service
`delivery unit 28 provides two different types of network
`services. It should be noted that the interface 30 shown
`
`schematically in FIG. 7 can be similar to any one of those
`shown in FIGS. 3—5. In some embodiments, the interface 30
`is a component that is external to both the network interface
`unit 26A or 26B and the service delivery unit 28.
`More particularly, the access system 18 shown in FIG. 7
`includes a cable network interface unit 26A for providing a
`connection to a cable network, and a fiber network interface
`unit 26B for providing a connection to a fiber optic network.
`To those ends, the cable network interface unit 26A includes
`a tuner 40 to provide the physical layer tuning functions, and
`a DOCSIS MAC and Scheduler 42 that implements DOC-
`SIS standards via the tuner 40. For example, the DOCSIS
`MAC and Scheduler 42 may coordinate cable transmissions
`with other transmissions on the cable network, control
`bandwidth allocations and quality of service, and commu-
`nicate with a head end device across the cable network. Both
`the tuner 40 and DOCSIS MAC and Scheduler 42, which
`function in this embodiment as the medium module 32, may
`be conventionally available devices.
`The fiber network interface unit 26B includes an optical
`to electrical converter 44 for converting incoming light
`signals to electrical signals. The converter 44 also includes
`logic for executing MAC functions on the fiber network to
`permit multiple different users on a network (i.e., external to
`the user’s premises) to share its use. In illustrative embodi-
`ments,
`the converter 44, which functions as the medium
`module 32 in this embodiment,
`includes a conventional
`PON (passive optical network) diode receiver and laser
`transmitter, such as a gigabit Ethernet PON microchip.
`
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`The service delivery unit 28 includes a processor 46 for
`executing much of the logic required by the service delivery
`unit, an Ethernet module 48 for communicating with an
`Ethernet card on a computer (i.e., thus providing a readily
`available and simple connection to such computer), and an
`IP telephony module 50 for providing IP telephony services
`to one or more IP telephones. The processor 46 and IP
`telephony module 50 are discussed in greater detail below.
`In addition, the service delivery unit 28 includes four plugs
`52 for coupling the IP telephony module 50 with up to four
`different IP telephones, and one plug 54 for coupling the
`Ethernet module 48 with a computer.
`The IP telephony module 50 includes logic for commu-
`nicating with one or more IP telephones, and executing the
`functions requested by such telephone(s). Among other
`things, those functions may include distinguishing between
`the different coupled telephones, directing incoming data to
`the appropriate telephone, forwarding data from one tele-
`phone to an appropriate receiving device (e.g., using an
`appropriate IP address), signaling processes, and line card
`functions. Of course, other functions typically executed for
`such purposes also are implemented in the IP telephony
`module 50. To these ends, the IP telephony module 50 may
`include an IP stack, MGCP Signaling, and a line card. For
`example, these may be implemented, at least in part, by the
`combination of a digital signal processor (“DSP”), sub-
`scriber line access controller (“SLAC”), and a subscriber
`line interface circuit (“SLIC”) that together are preconfig-
`ured to execute the necessary functions.
`The processor 46 provides overall controlling function-
`ality for the service delivery unit 28, and specific function-
`ality to the Ethernet module 48 and the IP telephony module
`50.
`In particular,
`the processor 46 may implement and
`maintain quality of service requirements, which are trans-
`mitted to the network interface unit 26 (e. g., a telephone call
`may require a specific quality of service), resource manage-
`ment within the service delivery unit 28 between the various
`modules, and media access control (“MAC”) functionality
`for the Ethernet module 48 on behalf of a computer, which
`may be coupled with a local area network. To implement
`these and other functions,
`the processor 46 may be any
`conventional processor in the art. For example, the processor
`46 may be the POWERPCTM 850 Processor, distributed by
`Motorola, Inc. of Schaumburg, Ill.
`As noted above, use of the disclosed system is not limited
`to the disclosed types of network services and network types
`22. Principles of various embodiments thus can be applied
`to other network types 22 and network services currently
`available. In fact, such principles are expected to apply to
`future network types and network services not currently
`deployed.
`Use of the disclosed modular access system 18 thus
`permits a single network interface unit 26 to cooperate with
`one or more of many different types of service delivery unit
`28 to act as data communication equipment for a coupled
`network device. In a similar manner, the access system 18
`also permits a single service delivery unit 28 to cooperate
`with one or more of many different
`types of network
`interface units 26 for the same purposes. This eliminates the
`need for a multitude of specialized DCEs that each are
`specific to both one type of network and one type of network
`service,
`thus providing flexibility and saving equip