(12) United States Patent
`Russell et al.
`
`I 1111111111111111 11111 lllll lllll lllll lllll 111111111111111 lll111111111111111
`US006816496B2
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,816,496 B2
`*Nov. 9, 2004
`
`(54) FRAME BASED DATA TRANSMISSION
`OVER SYNCHRONOUS DIGITAL
`HIERARCHY NETWORK
`
`(75)
`
`Inventors: John Paul Russell, Sawbridgeworth
`(GB); Christopher David Murton,
`Chelmsford (GB); David Michael
`Goodman, St Albans (GB);
`Christopher Thomas William
`Ramsden, Hertford (GB); James
`Shields, Ottawa (CA)
`
`(73)
`
`Assignee: Nortel Networks Ltd., St. Laurent
`(CA)
`
`( *)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`This patent is subject to a terminal dis(cid:173)
`claimer.
`
`(21) Appl. No.: 10/233,183
`
`(22) Filed:
`
`Aug. 29, 2002
`
`(65)
`
`Prior Publication Data
`
`US 2003/0021294 Al Jan. 30, 2003
`
`Related U.S. Application Data
`
`(62) Division of application No. 09/143,466, filed on Aug. 27,
`1998, now Pat. No. 6,496,519.
`Int. Cl.7 ................................................ H04L 12/56
`
`(51)
`
`(52) U.S. Cl. ....................................................... 370/408
`(58) Field of Search ................................. 370/474, 476,
`370/498, 353-356, 466, 907, 914, 916,
`442, 464, 395.51, 232, 395.63, 395.44,
`401-403, 465
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`6,014,708 A * 1/2000 Klish
`......................... 709/232
`6,584,118 Bl * 6/2003 Russell et al. .............. 370/466
`* cited by examiner
`
`Primary Examiner-Wellington Chin
`Assistant Examiner-Brenda Pham
`(74) Attorney, Agent, or Firm-Barnes & Thornburg, LL
`
`(57)
`
`ABSTRACT
`
`A frame based data communications network is interfaced to
`a synchronous digital hierarchy network via a plurality of
`frame based data port cards incorporated into a plurality of
`synchronous multiplexers. Each port card comprises a con(cid:173)
`ventional frame based data port, a frame switch, a rate
`adapter means and a mapping means for mapping data
`frames into a plurality of SDH virtual containers. Frame
`based data is incorporated directly into a synchronous virtual
`container without encapsulation in an intermediate protocol.
`A number of topologies of a frame based data channel
`network are possible, overlaid on the underlying synchro(cid:173)
`nous transport network, including an open loop topology, a
`ring mode topology, and a backhaul topology.
`
`30 Claims, 11 Drawing Sheets
`
`Dual
`10M/100M Tx
`
`100L.
`
`1000
`
`STM-16 with 2xVC4 (STS-6c)
`~1M
`1007
`
`Up to 6 STM-4 tribs in TN16XE
`
`TN4XE
`
`STM-1 spurs or rings
`with 5x VC12 for 10M
`and 1/2xVC3 for 100M
`
`1029
`
`1005
`
`1030
`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 1
`
`

`

`U.S. Patent
`
`Nov. 9, 2004
`
`Sheet 1 of 11
`
`US 6,816,496 B2
`
`05
`
`106
`
`103
`
`100
`
`102
`
`101
`
`10L.
`
`Fig.1
`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 2
`
`

`

`U.S. Patent
`
`Nov. 9, 2004
`
`Sheet 2 of 11
`
`US 6,816,496 B2
`
`SDH/SONET
`PAYLOAD MAPPER
`
`-~200
`
`I
`
`RA TE ADAPTION
`RING OR POINT TO
`POINT MODES
`
`-~ -201
`
`ETHERNET FRAME
`SWITCH
`(Multi post MAC Bridge)
`
`----202
`
`ETHERNET
`PHYSICAL
`
`--203
`
`Fig. 2
`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 3
`
`

`

`U.S. Patent
`
`Nov. 9, 2004
`
`Sheet 3 of 11
`
`US 6,816,496 B2
`
`STM-N
`
`AU-4
`
`VC- 4 - - - - - - - C- 4
`
`x3
`
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`
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`
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`
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`
`44736
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`kbit/s
`6312
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`
`C- 12
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`2048
`kbit/s
`
`1544
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`
`- - - multiplexing
`
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`
`- - - mapping
`II ; mt ii SON ET specific options
`ETSI specific options
`-
`
`Fig. 3
`(Prior Art)
`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 4
`
`

`

`U.S. Patent
`
`Nov. 9, 2004
`
`Sheet 4 of 11
`
`US 6,816,496 B2
`
`270 x N columns (bytes)
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`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 5
`
`

`

`U.S. Patent
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`Nov. 9, 2004
`
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 6
`
`

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`Nov. 9, 2004
`
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 7
`
`

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`
`Nov. 9, 2004
`
`Sheet 7 of 11
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 8
`
`

`

`U.S. Patent
`
`Nov. 9, 2004
`
`Sheet 8 of 11
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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 9
`
`

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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 10
`
`

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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 11
`
`

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`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 12
`
`

`

`US 6,816,496 B2
`
`1
`FRAME BASED DATA TRANSMISSION
`OVER SYNCHRONOUS DIGITAL
`HIERARCHY NETWORK
`
`RELATED APPLICATION
`
`This application is a division of U.S. patent application
`Ser. No. 09/143,466, filed Aug. 27, 1998 now U.S. Pat. No.
`6,496,519.
`
`FIELD OF THE INVENTION
`
`The present invention relates to the carrying of data frame
`traffic over a synchronous digital network.
`
`BACKGROUND TO THE INVENTION
`
`5
`
`2
`The distinction between networks which have historically
`been considered to be local area networks and those which
`have been considered to be wide area networks is becoming
`increasingly blurred.
`Because conventional telecoms systems have developed
`in parallel with conventional datacoms systems, there is a
`significant mis-match in data rates between conventional
`datacoms protocols as used in LANs and WANs, and con(cid:173)
`ventional telecoms protocols. In general, telecoms operators
`10 provide equipment having standard telecoms interfaces, for
`example El, Tl, E3, T3, STM-1, which are used by the
`datacoms industry to provide wide area network point to
`point links. However, this is inconvenient for datacoms
`providers since datacoms protocols have developed using a
`15 completely different set of interfaces and protocols, for
`example carrier sense multiple access collision detection
`CSMNCD systems, subject of IEEE standard 802.3, and
`Ethernet which is available in 10 MBits/s, 100 MBits/s and
`1 GigaBits/s versions. Conventional datacoms protocols do
`20 not match up very well to conventional telecoms interfaces
`because of a mis-match in data rates and technologies
`between conventional datacoms and conventional telecoms.
`Several prior art attempts have been made to carry frame
`based data over telecoms networks. Prior art systems for
`25 incorporating frame based data over synchronous networks
`include schemes which contain Ethernet data frames in
`asynchronous transfer mode (ATM) cells which are then
`transported in a plesioscynchronous mode and which may
`then be transported according to ITU-T recommendation
`30 G.708 in a synchronous digital hierarchy (SDH) network. In
`this scheme, known as IMA (Inverse multiplexing of ATM),
`conceived by the ATM Forum, an ATM circuit is divided and
`input into a plurality of El circuits. This enables an ATM
`signal to be carried across a legacy network, for example a
`35 plesiosynchronous digital hierarchy (PDH) network. Ether(cid:173)
`net frames are included as the payload of the ATM cells,
`which are then carried via the El circuits over a conven(cid:173)
`tional PDH network. However, this prior art scheme has a
`disadvantage of a high packetization header overhead,
`40 which can comprise up to 20% of the SDH payload.
`Another prior art system aimed at carrying frame based
`data over synchronous digital networks is the conventional
`Ethernet remote bridge. This system is based on the known
`PPP protocol, for example, as implemented by the packet on
`Sonet (POS phy) system of PMC Sierra. However, in this
`scheme, a high packetization overhead is present and pack(cid:173)
`aging delays are relatively high.
`Manufacturers such as CISCO, and Bay Networks pro(cid:173)
`duce equipment for both of the above mentioned inverse
`multiplexing of ATM, and Ethernet bridge systems.
`A further prior art scheme uses a plurality of fiber optic
`repeaters to provide native Ethernet rate connections
`between a customer premises and a LAN switch. However,
`this solution dedicates a whole fiber to Ethernet rate, which
`is an inefficient use of the fiber optic cable resources.
`
`Historically, the telecommunications industry has devel(cid:173)
`oped separately and largely independently from the com(cid:173)
`puting industry. Conventional telecommunications systems
`are characterized by having high reliability circuit switched
`networks for communicating over long distances, whereas
`data communications between communicating computers is
`largely based upon shared access packet communications.
`Datacoms may operate over a local area, to form a local
`area network (LAN) or over a wide area to form a wide area
`network (WAN). Historically the difference between a LAN
`and a WAN is one of geographical coverage. A LAN may
`cover communicating computing devices distributed over an
`area of kilometers or tens of kilometers, whereas a WAN
`may encompass communicating computing devices distrib(cid:173)
`uted over a wider geographical area, of the order of hundreds
`of kilometers or greater.
`Conventional local area networks are generally taken to
`be digital data networks operating at rates in excess of 1
`MBits/s over distances of from a few meters up to several
`kilometers. Conventional local area networks are almost
`universally serial systems, in which both data and control
`functions are carried through the same channel or medium.
`Local area networks are primarily data transmission systems
`intended to link computer devices and associated devices
`within a restricted geographical area. However, many local
`area networks include speech transmission as a service. A
`plurality of computer and associated devices linked together
`in a LAN may range from anything from a full-scale
`mainframe computing system to small personal computers.
`Since a local area network is confined to a restricted geo- 45
`graphical area, it is possible to employ vastly different
`transmission methods from those commonly used in tele(cid:173)
`communications systems. Local area networks are usually
`specific to a particular organization which owns them and
`can be completely independent of the constraints imposed 50
`by public telephone authorities, the ITU, and other public
`services. Local area networks are characterized by compris(cid:173)
`ing inexpensive line driving equipment rather than the
`relatively complex modems needed for public analogue
`networks. High data transmission rates are achieved by 55
`utilizing the advantages of short distance.
`Conventional wide area networks operate in general on a
`greater scale than local area networks. A wide area network
`is generally employed whenever information in electronic
`form on cables leaves a site, even for short distances. Data 60
`transmission rates involved are generally between a few
`hundred and a few thousand bits per second, typically up to
`50 kilobits per second. The distances involved in a wide area
`network are from around 1 kilometer to possible thousands
`of kilometers, and error rates are greater than with local area 65
`networks. Wide area networks are generally carried over
`public telecommunications networks.
`
`SUMMARY OF THE INVENTION
`
`One object of the present invention is to provide high data
`rate, high reliability functionality available with conven(cid:173)
`tional local area networks, but over a wide area network
`transported on a long distance high capacity synchronous
`digital network.
`Another object of the present invention is to overcome
`data rate mis-matched between conventional datacoms sys(cid:173)
`tems and conventional telecommunications systems in an
`efficient manner.
`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 13
`
`

`

`US 6,816,496 B2
`
`25
`
`3
`Another object of the present invention is to incorporate
`frame based data directly into a synchronous digital hierar(cid:173)
`chy payload, without encapsulation in an ATM cell or other
`intermediate carrier.
`Another object of the present invention is to incorporate 5
`frame based data into a synchronous network without incur(cid:173)
`ring high processing delays, and without incurring a high
`packetization header overhead.
`According to one aspect of the present invention, there is
`provided a frame based data communications network com- 10
`prising:
`a plurality of computer devices each having a frame based
`data channel interface;
`a plurality of synchronous multiplexers, each having a
`frame based data channel interface and a synchronous digital 15
`communications port, and capable of interfacing between a
`frame based data protocol and a synchronous digital network
`protocol;
`wherein said plurality of computing devices communicate
`with each other over a plurality of frame based data 20
`channels, said frame based data channels carried over a
`synchronous digital transport network connecting said plu(cid:173)
`rality of synchronous multiplexers.
`Preferably, said frame based channel interface interfaces
`directly between said frame based data protocol and said
`synchronous digital network protocol without traversing any
`intermediate protocols.
`Preferably, said frame based data channel interface com(cid:173)
`prises: means for mapping a data frame of said frame based 30
`data channel to at least one payload of said synchronous
`network protocol.
`The synchronous digital transport network may comprise
`a synchronous digital hierarchy (SDH) network in accor(cid:173)
`dance with ITU-T G70.X, an example of which is the 35
`synchronous optical network (SONET) in accordance with
`ITU-T recommendation G.708 and related recommenda(cid:173)
`tions.
`Synchronous multiplexers may comprise add-drop
`multiplexers, or terminal multiplexers.
`According to a second aspect of the present invention,
`there is provided a synchronous digital multiplexer com(cid:173)
`prising:
`a plurality of telecoms tributary interfaces;
`a frame based data channel interface; and
`a synchronous digital channel port.
`By providing a plurality of telecoms tributaries in addition
`to a frame based data access port in a synchronous
`multiplexer, frame based data channels may be entered
`directly into synchronous digital hierarchy virtual container
`payloads in an efficient manner.
`Preferably said frame based channel interface comprises:
`a frame based data channel physical port;
`a frame based data channel switch communicating with
`said frame based data channel physical port;
`a rate adaption means for converting data at a frame based
`data channel rate into a bitstream of a data rate capable of
`being carried in at least one virtual container; and
`a synchronous digital network payload mapper for map- 60
`ping said bitstream into said at least one virtual container.
`According to a third aspect of the present invention there
`is provided a method of communicating frame based data
`over a synchronous digital network comprising the steps of:
`modifying a data rate of said frame based data to a rate 65
`compatible with a synchronous digital network virtual con(cid:173)
`tainer; and
`
`50
`
`4
`inputting said rate adapted frame based data directly into
`at least one said synchronous digital network virtual con(cid:173)
`tainer.
`Preferably said method comprises the steps of:
`concatenating a plurality of said virtual containers
`together; and
`containing a said data frame into said plurality of con(cid:173)
`catenated virtual containers.
`The invention includes a method of creating a frame
`based data channel within a synchronous digital channel
`comprising the steps of:
`modifying a data rate of said frame based data outside said
`synchronous digital channel to a rate compatible with said
`synchronous digital channel; and
`mapping said rate adapted frame based data directly to
`said synchronous digital channel.
`Said step of mapping preferably comprises containing
`said modified data frame based data into at least one virtual
`container.
`The invention includes a communications network com(cid:173)
`prising:
`a plurality of network components supporting an OSI
`layer 2 frame based data channel;
`a plurality of network components supporting at least one
`synchronous digital channel; and
`a plurality of network components capable of transferring
`data frames of said OSI layer 2 data channel directly into and
`out of a plurality of payloads of said at least one synchro(cid:173)
`nous digital channel.
`The invention includes a data communications network
`comprising:
`a plurality of network devices each comprising: an OSI
`layer 2 frame switching device; a rate adaption device for
`adapting a data rate between an OSI layer 2 data rate and a
`synchronous transmission data rate; and a mapping device
`for mapping data between said OSI layer 2 frame switch and
`a synchronous digital channel;
`wherein said plurality of mapping devices communicate
`over said synchronous digital channel; and
`said plurality of OSI layer 2 frame switching devices
`communicate over an OSI layer 2 channel carried on said
`synchronous digital network.
`Said OSI layer 2 channel may comprise a ring channel
`linking said plurality of network devices.
`Said OSI layer 2 channel may comprise a plurality of
`point to point channels linking pairs of individual said OSI
`layer 2 frame switches.
`The invention includes a communications network com(cid:173)
`prising:
`a plurality of network devices each comprising: a rate
`adaption device for adapting a data rate between an OSI
`55 layer 2 data rate and a synchronous transmission data rate;
`and a mapping device for mapping data between an OSI
`layer 2 channel and a synchronous digital channel;
`wherein said plurality of mapping means communicate
`over said synchronous digital channel; and
`said plurality of rate adaption means communicate over
`said OSI layer 2 channel carried on said synchronous digital
`channel.
`Said OSI layer 2 channel may comprise a ring channel.
`
`40
`
`45
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`For a better understanding of the invention and to show
`how the same may be carried into effect, there will now be
`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 14
`
`

`

`US 6,816,496 B2
`
`5
`described by way of example only, specific embodiments,
`methods and processes according to the present invention
`with reference to the accompanying drawings in which:
`FIG. 1 illustrates schematically elements of a first
`embodiment data network carrying a frame based data
`channel over a synchronous data channel;
`FIG. 2 illustrates schematically a frame based data chan(cid:173)
`nel port component of a synchronous digital multiplexer
`according to a first embodiment of the present invention;
`FIG. 3 illustrates schematically a prior art synchronous
`digital hierarchy multiplexing structure;
`FIG. 4 illustrates schematically a synchronous digital
`hierarchy; STM frame and payload;
`FIG. 5 illustrates schematically a plurality of synchronous 15
`digital multiplexers connected together by means of a plu(cid:173)
`rality of frame based data ports, supporting an Ethernet
`tandem switching mode channel carried on a synchronous
`digital loop;
`FIG. 6 herein illustrates a plurality of synchronous digital
`multiplexers, each having a frame based data port, support(cid:173)
`ing an Ethernet ring carried on an underlying synchronous
`digital loop;
`FIG. 7 illustrates schematically a logical view of the
`Ethernet ring and synchronous digital loop of FIG. 6;
`FIG. 8 illustrates schematically a plurality of synchronous
`digital multiplexers each having a frame based data port,
`supporting a plurality of point to point Ethernet channels in
`a backhaul mode of connection, carried over a synchronous
`digital loop;
`FIG. 9 herein illustrates a first example of a deployment
`of a frame based data channel over a synchronous digital
`hierarchy network;
`FIG. 10 illustrates schematically a second example of 35
`deployment of frame based data channels over a synchro(cid:173)
`nous digital hierarchy network; and
`FIG. 11 illustrates schematically a third example of
`deployment of a plurality of frame based data channels over
`a synchronous digital hierarchy network.
`
`6
`terminal multiplexers, 100, 101 connected to each other by
`an optical fiber communications link 102; a first datacoms
`router 103 communicating with first terminal multiplexer
`100; a second datacoms router 104 communicating with
`5 second terminal multiplexer 101; a first computer device 105
`communicating with first datacoms router 100; and a second
`computer device communicating with second datacoms
`router 104. Each of first and second computer devices 105,
`106, first and second routers 103, 104 and first and second
`10 terminal multiplexers 100, 101 comprise a frame based data
`channel interface. First and second computer devices com(cid:173)
`municate frame based data with each other over the routers
`and over the optical fiber communications link. Communi-
`cation between first and second multiplexers 100, 101 is via
`a synchronous digital network protocol, for example the
`synchronous digital hierarchy protocol (SDH) or synchro-
`nous optical network protocol (SONET) as specified in
`ITU-T recommendation G.709 and related recommenda-
`tions. Communication between the computing devices 105
`20 and 106 and the respective datacoms routers 103, 104 is by
`conventional data frame based data communications proto(cid:173)
`col.
`In this specification, the term frame based data commu(cid:173)
`nications protocol or system is used to refer to any data
`25 communications system or protocol in which blocks of data
`are assembled within OSI layer 2. Both traffic data and
`control data may be contained within the OSI layer 2 frame.
`Frames in OSI layer 2 systems may comprise packets or
`blocks of data bytes of variable length. Examples of con-
`3o ventional frame based data communications protocols
`include IEEE standard 802.3 CSMNCD local area network
`systems, Ethernet systems, conventional token ring systems,
`conventional token bus systems, conventional fiber distrib(cid:173)
`uted data interface FDDI systems and conventional dual
`queue dual bus (DQDB) systems.
`Communication between first and second routers 103, 104
`and respective first and second terminal multiplexers 100,
`101 is by a frame based data technology as will be under(cid:173)
`stood by those skilled in the art. First and second terminal
`40 multiplexers 100, 101 may be separated geographically by
`distances from the order of a few meters to thousands of
`kilometers. The arrangement shown in FIG. 1 is a simplified
`arrangement, and in practice many computer devices, many
`routers and many multiplexers will be interconnected to
`45 form an integrated frame based data communications system
`carried over a synchronous digital network.
`As mentioned hereinbefore, a problem with transporting
`data contained in conventional datacoms frame based data
`50 systems over conventional synchronous digital telecoms
`transport systems is that there is a mis-match of data rates
`between the datacoms domain and the telecommunications
`domain.
`Therefore, for communication of datacoms systems data
`at first and second routers 103, 104 with first and second
`terminal multiplexers 100, 101 efficient conversion between
`the frame based data datacoms system and the synchronous
`digital network protocols needs to be achieved.
`Hereinafter, specific methods and embodiments according
`to a best mode herein will be described specific to synchro(cid:173)
`nous digital hierarchy telecommunications systems in accor(cid:173)
`dance with ITU recommendation G.709, and an IEEE stan(cid:173)
`dard 802.3 frame based data carrier system, a representative
`example of which is the Ethernet system. However, the
`general principles, methods and apparatus according to the
`present invention encompass synchronous digital networks
`in general, and OSI layer 2 frame based data carrier systems
`
`DETAILED DESCRIPTION OF THE BEST
`MODE FOR CARRYING OUT THE INVENTION
`
`There will now be described by way of example the best
`mode contemplated by the inventors for carrying out the
`invention. In the following description numerous specific
`details are set forth in order to provide a thorough under(cid:173)
`standing of the present invention. It will be apparent
`however, to one skilled in the art, that the present invention
`may be practiced without limitation to these specific details.
`In other instances, well known methods and structures have
`not been described in detail so as not to unnecessarily
`obscure the present invention.
`Referring to FIG. 1 herein, there is illustrated schemati(cid:173)
`cally elements of a first embodiment data network according 55
`to the present invention. A frame based data communica(cid:173)
`tions system carried over a synchronous digital network is
`provided by the arrangement shown in FIG. 1. In this
`specification, the terms synchronous network and synchro(cid:173)
`nous digital network are used to refer to a time division 60
`multiplexed synchronous transport layer in OSI layer 1.
`Conventional examples of such networks include the syn(cid:173)
`chronous digital hierarchy (SDH) of ITU-T recommendation
`G70.X, which incorporates synchronous optical network
`(SONET) systems specified in ITU-T recommendation 65
`G.709 and related recommendations. The data network
`elements comprise first and second synchronous digital
`
`Petitioners Microsoft Corporation and HP Inc. - Ex. 1035, p. 15
`
`

`

`US 6,816,496 B2
`
`7
`in general, and are not restricted to the specific examples of
`synchronous digital hierarchy networks or Ethernet net(cid:173)
`works.
`Referring to FIG. 2 herein, there is illustrated schemati(cid:173)
`cally components of an Ethernet port card comprising a
`synchronous digital multiplexer. The Ethernet port card is
`incorporated into a synchronous digital hierarchy multi(cid:173)
`plexer (or a SONET mulitplexer), so that as well as having
`a plurality of tributary interfaces for telecoms channels, for
`example El, Tl, E3, T3, STM-1, the multiplexer also has an 10
`interface for frame based data systems, eg Ethernet.
`Fundamentally, SDH multiplexers operate to time divi(cid:173)
`sion multiplex bit oriented data. A plurality of lower data
`rate telecoms tributaries are multiplexed into a set of virtual
`containers operating at higher data rates. The SDH multi(cid:173)
`plexing structure according to ITU-T recommendation
`G.70X is illustrated schematically in FIG. 3 herein. A set of
`STM frames are assembled to contain a plurality of virtual
`containers which are carried as an STM payload as illus(cid:173)
`trated in FIG. 4 herein. On the other hand, conventional 20
`datacoms routers and equipment are frame oriented devices
`which operate on packets of data. The Ethernet port card
`adapts the Ethernet data frames to a rate which matches a
`rate which can be multiplexed into a virtual container, and
`maps each Ethernet data frame into one or more SDH virtual 25
`containers directly without any further encapsulation in
`intermediate protocols.
`For example, a 10 MBits/s Ethernet channel may be
`mapped onto 5 VC12 containers, each VC12 container
`having a rate of 2.048 MBits/s. The 5 VC12 containers are 30
`concatenated together to carry the 10 MBits/s Ethernet
`channel.
`For entry of a 100 MBits/s Ethernet channel into the
`synchronous network, a single 100 MBits/s Ethernet channel 35
`may be mapped into 2 concatenated VC3 containers each
`having a capacity of 51.84 10 MBits/s to carry an Ethernet
`1 GBits/s channel over a synchronous network, the Ethernet
`channel is mapped into 7 VC4 containers, each having a
`capacity of 139 MBits/s.
`The Ethernet port card of FIG. 2 herein comprises a
`conventional Ethernet physical port 201, the Ethernet physi-
`cal port communicating with an Ethernet frame switch 202
`which may comprise a conventional frame switch, such as
`available from Plaintree, MMC, or TI; a rate adaption means 45
`203 for adapting between Ethernet rates and SDH rates
`equivalent to the rates of the virtual containers; and an SDH
`payload mapper 204 for mapping Ethernet frames into one
`or more SDH payloads. Rate adaption means 203 and SDH
`payload mapper 204 may be implemented as a field pro- 50
`grammable gate array (FPGA) or an application specific
`integrated circuit (ASIC).
`Operation of SDH payload mapper 204 is disclosed in the
`applicant's co-pending U.S. patent application entitled
`"Payload Mapping in SDH Networks", a copy of which is 55
`filed herewith. Data frames are mapped directly into SDH
`virtual containers for transport across an SDH network
`without adapting through any intermediate protocols.
`Rate adaption means 203 comprises a first plurality of
`Ethernet ports operating at 10 MBits/s; and 100 MBits/s in 60
`accordance with IEEE standard 802.3; and a second plural-
`ity of ports operating at 2 MBits/s, 50 MBits/s and 100
`MBits/s communicating with SDH payload mapper 204.
`Rate adaption means 203 comprises a plurality of through
`channels for adapting IEEE standard 802.3 data frames into 65
`bitstreams having data rates of 2 MBits/s, 50 MBits/s and
`100 MBits/s. Rate adaption means 203 comprises a plurality
`
`8
`of multiple channels each adapting an IEEE standard 802.3
`rate data frame channel to a 2 MBits/s, 50 MBits/s or 100
`MBits/s bitstream channel. Rate adaption means 203 oper(cid:173)
`ates effectively as a packet buffer, since Ethernet Data
`5 Frames issue from the Ethernet frame switches at a higher
`rate than they can be multiplexed into SDH virtual contain(cid:173)
`ers. Rate adaption means 203 inputs Ethernet data frames
`from Ethernet frame switche