An Operations Support System for Transport Networks

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An Operations Support System for Transport Networks

ERICSSONREVIEW41990Telecommunications Network ArchitectureFMAS - An Operations Support System for Transport Networks


ERICSSON REVIEWNumber 4 1990 Volume 67Responsible publisher GostaLindbergEditor GoranNorrmanEditorial staff MarttiSubscription PeterMayrViitaniemiSubscription one year $30Address S-126 25 Stockholm, SwedenPublished in Swedish, English, French and Spanish with four issues per yearCopyright Telefonaktiebolaget L M EricssonContents148 • Telecommunications Network Architecture163 • FMAS - An Operations Support System for Transport NetworksCoverThe computerized operations support systemFMAS offers centralized supervision and controlof digital transport networks.Traditionally, cross-connections between sets oftransmission equipment have been carried outmanually in coaxial distribution frames.With FMAS, operators can order thecorresponding cross-connections from a terminalat an operations centre. These connections areeffected by digital cross-connect systems locatedin the transport network nodes.


Functional blockFunctionPILPALPTLPCLPXHPAHPTHPCHPXSAMSPMSTRSTSPISEMFMCFMTSMTPILCSHCSPhysical InterfaceLower order PathAdaptationLower order PathTerminationLower order PathConnectionLower order PathCross ConnectionHiger order PathAdaptationHigher order PathTerminationHiger order PathConnectionHigher order PathCross ConnectionSection AdaptationMultiplex SectionProtectionMultiplex SectionTerminationRegenerator SectionTerminationSynchronousPhysical InterfaceSynchronous EquipmentManagement FunctionMessage CommunicationFunctionMultiplex TimingSourceMultiplex TimingPhysical InterfaceLower orderConnection SupervisionHiger orderConnection SupervisionTable 4Synchronous functional blocksConversion from/to in-station or inter-station signals(Rec. G.703)Maps the payload into the container(Rec. G.709)Adds VC Path overheadAllows flexible assignment betweenlower and higher order VCs (bidirectional)Allows flexible cross-conectionsbetween lower and higher order VCs'Processes pointer to indicate phasebetween lower and higher order VCs, assembles completehigher order VCAdds higher order path overheadAllows flexible assignment betweenhigher order VCs and STM-N (bidirectional)Allows flexible cross-connectionsbetween higher order VCs and STM-N"Processes pointer to indicate phase between higherorder VCs and STM-N, assembles complete STM-MNProvides branching to other linesystem for protectionAdds/extracts rows 5 to 9 of theSection overheadAdds/extracts rows 1 to 3 of theSection overheadConversion to/from in-station orinter-station signals (Rec. G.707)Converts performance data andalarms into object oriented messages for transmissionover DCCs (Data Communications Channels)or Q-lnterfaceProvides facilities for thetransport of TMN messages to and from the SEMFProvides timing to synchronousfunctional blocksProvides interface for externalsynchronization signalMonitoring of VC overhead in signal towardscross-connected LPX/HPX. Termination ofVC signal towards not connected LPX/HPXPermits transparent transmissionof signal from cross-connectedLPX/HPX. Generation of replacement VC signal for notconnected LPX/HPX' types of cross-connect:unidirectionalbidirectionalbroadcastloopbackmonitoringmeasurementThe various units, each of which carriesa particular type of characteristic information,are combined in the multiplexingscheme defined by CCITT, fig 2.The complete function of synchronousdigital transmission equipment can bedescribed by means of a set of functionalblocks similar to those used for plesiochronoustransmission functions.The synchronous functional blocks arelisted in table 4.Specific implementations of SDH equipment,such as digital multiplexers 6(SMUX), cross-connect systems 7(SDXC) and digital line systems 8 , are describedby means of defined combinationsof functional blocks as exemplifiedbelow.Multiplexing and synchronoustransmission of plesiochronous tributariesFig. 6 illustrates the transmission of 63plesiochronous 2 Mbit/s signals over anSTM-1 section. The relationships betweenthe SDH elements of the multiplexingscheme and the involved functionalblocks are also shown. In the firstfunctional block (LPA) after the physicalinterface (PI), the plesiochronous tributariesare mapped into a container in theSDH.Synchronous multiplexer, SMUXFig. 7 shows a generalized functionalblock diagram of Synchronous DigitalMultiplexers (SMUX). The function of aspecific SMUX, type 1, is built up of theshaded blocks. This SMUX converts anumber of plesiochronous digital tributarysignals of a lower bit rate to anaggregate synchronous signal of a higherbit rate, and vice versa In addition tothese basic functions, features such asflexible assignment of information,drop-insert and protection switchingcan be included in the general version ofan SMUX. The SPI (Synchronous PhysicalInterface) can be either electric oroptical in exchanges; between exchangesit is normally optical.Synchronous cross-connects, SDXCSynchronous digital cross-connectequipment is capable of switching andmultiplexing a variety of PDH and SDHsignals. Characteristic SDXC featuresare- cross-connection of different bitrates,e.g. 64 kbit/s to 155 Mbit/s- holding times equivalent to hours,days or longer periods- switch control and management viaTMN management interface.The signals belong to certain levels inthe transport network depending ontheir bit rates and formats. At the inputand output ports of the SDXC the signalsappear at port level, whereas theyare cross-connected at what is calledcross-connect levels. Tables 1 and 2show typical port levels; table 5 typicalcross-connect levels. The combinationsof port and cross-connect levels thatcan be handled by an SDXC determineits function and designation. For a detaileddescription of the functions of differentequipments in the SDXC family -see ref. 2.


154Crossconnectlevelbase 1,544base 2,048Port levelCross-connect levelTable 5 (left)Cross-connect levels (kbit/s) for synchronousdigital cross-connect (SDXC)1234VC-11 1,664VC-2VC-3VC-4VC-12 2,240fi,«4H4ftSRfl1 so 3nfiSTM-1140 Mbit/s34 Mbit/s2 Mbit/sVC-4VC-4 and VC-12VC-3 and VC-12VC-12Table 6 (right)SDXC functionsVCVirtual ContainerTopology Transport FunctionLN Layer Networkl_ LinkSN SubnetworkDSN Degenerate SubnetworkAssociation Transport FunctionATrailTLCSNCDSNCTLCNCClient-to-server AdaptationTrailTrail TerminationLink ConnectionSubnetwork ConnectionDegenerate SubnetworkConnectionTandem Link ConnectionNetwork ConnectionTransport Reference PointsAP Access Points to the Server LayerNetworkCP Connection PointTCP Termination Connection PointTable 7Transport Functions and Transport ReferencePointsFig. 7Generalized functional block diagram of synchronousmultiplexers (SMUX). Type 1 SMUXesmultiplex a number of plesiochronous lower bitrate tributaries into an aggregate synchronoussignal with higher bit rateFunctional blocks included In a Type 1 SMUXFig. 8 shows a generalized block diagramof synchronous digital cross-connectequipment for the 2 Mbit/s digitalhierarchy. The functional blocks are definedin table 4. Table 6 shows the functionalityof the equipment.Transport NetworkThe described architecture of the transportnetwork can be applied to PDH,SDH and ATM networks. The transportnetwork model considered is based onthe concepts of layering and partitioning- concepts which allow a high degreeof recursion. The transport of informationis described by means ofTransport Functions separated byTransport Reference Points. EachTransport Function for one-way transportis characterized by an input and anoutput. The Transport Reference Pointcombines the output and input of consecutiveTransport Functions in a bindingrelationship. Inputs and outputs oftwo-way Transport Functions are combinedin pairing relationships.Transport Functions can be divided intoTopology Transport Functions, describingthe capability to provide transport,and Association Transport Functions,which describe the particular instanceof transport, table 7. Transport Functionscan also be divided according totheir ability to be configured. StaticTransport Functions are configured pri-or to a demand for transport; basically,they provide inflexible connectivity. DynamicTransport Functions are configuredin response to a demand fortransport; they provide flexible connectivity.A number of Association TransportFunctions can be assembled intoan Abstract Transport Function.Table 8 shows different types of TransportFunction, and table 9 shows TransportReference Points binding particularAssociation Transport Functions.Typical examples of Topology TransportFunctions areLayer Network International 140Mbit/s networkLinkSubnetworkDegenerateSubnetworkA number of parallel140 Mbit/s fibreoptical line systemsbetween two crossconnectsDigital Cross-connectequipmentDigital DistributionFrameTypical examples of Association TransportFunctions areClient-to-server Analog-digital conadaptationversion in PCM(A)terminals, bit rateconversion in PDHdigital multiplexers,framing and framealignment functions


Table 8 (right)Transport FunctionsTransportFunctionStatic(inflexibleconnectivity)Dynamic(flexibleconnectivity)155TopologyLN, L, DSNSNAssociationA, T, LC, DSNCSNCAbstractAssociationLC,TLCTRAIL, NCAssociationTransportFunctionATLC.SNCDSNC, TLCAAPAPCPTable 9Transport Reference PointsTAPTCPTCPLC, SNCDSNCTLCCPTCPCPFig. 8Generalized functional block diagram of synchronousdigital cross-connect equipment(SDXC)Trail Termination(T)SubnetworkConnection(SNC)DegenerateSubnetworkConnection(Deg SNC)Error detection,sending and receptionof alarms relatedto a characteristicsignalProcess of switchingand cross-connection.Subnetworkconnections areconfigured in themanagement process,i.e. the configurationof networkresources duringnetwork operation(allocation, routing)Connection in aDigital DistributionFrame. Degeneratesubnetwork connectionscannot beconfigured; theyLink Connection(LC)Tandem LinkConnection(TLC)result from functionalpartitioning forthe purpose of management(e.g. monitoringof parts oftandem link connections)Connection offeredby fibre optical linesystems. Link Connectionsare configuredin the commissioningprocess,i.e. the configurationof network resourcesprior to startof network operationConnection offeredby a number of linesystems in tandemtransporting thesame characteristic


156Fig. 9The pinciple of transport network layering. Twocalls in progress: one between telephone sets1 and 2, and another between telephone sets3 and 4Trail(T)signal and interconnectedthroughdistribution framesA particular instanceof a connectionthrough a layernetwork - see examplesin fig. 11.An additional Transport Function -Connection Supervision - is beingstudied. It will be used for trail monitoringand generation of output signals in adigital cross-connect if the incomingsignal is lost.Network layeringThe Transport Network is divided into anumber of Transport network Layers(TL). Each layer carries one type of characteristicinformation and has its ownmanagement capability and managedobjects. Characteristic information isdistinguished by bit rates, coding, andframe formats. Examples of types ofcharacteristic information are 2 Mbit/sinformation flows framed according toRec. G.704 and VC-4 signals accordingto Rec. G.708. Each layer of the transportnetwork is independent and can bechanged without affecting the architectureof other layers. Normally, an end-toendconnection between users employsFig. 10Generic network layering model showing theinterworking between two adjacent transportnetwork layersA Client-to-server adaptationT Trail terminationC ConnectionAP Access Point to the Server Layer NetworkTCP Termination Connection PointCP Connection Point® Client Layer Access Point


Fig. 11Examples of SDH and PDH trailsvarious types of characteristic information,which means that the informationflow must be supported by several transportnetwork layers. The principle ofnetwork layering is exemplified in fig. 9,which shows a transport network withthree layers.The Transmission Network contains- 64 kbit/s digital telephones and localexchanges- 2 Mbit/s line systems and synchronousdigital cross-connect equipment- 140 Mbit/s line systems.The corresponding network layers are- TL1, for the sourcing, sinking, transmittingand switching of 64 kbit/s signals- TL2, for the transmitting and crossconnectingof 2 Mbit/s signals- TL3, for the transmitting of 140 Mbit/ssignals.Two telephone services are shown inthe example: between subscribers 1-2and between subscribers 3-4.Fig. 10 shows, as an example, the AssociationTransport Functions involved intwo-layer signal transport. Basically, theclient-to-server adaptation occurs betweenthe client and server layers. Toillustrate the principles of the transportnetwork, the adaptation has been includedin the server network and onlythe access point to the client layer isshown in the figure (Client Layer AccessPoint).A transport layer may contain severaltrails, each carrying the same type ofcharacteristic information. TL1 in fig. 9contains two 64 kbit/s trails (64 kbit/scircuits).According to definitions used for theSDH, trails exist in three groups of layersforming circuit, path and transmissionmedia layer networks, fig. 11. A circuit isa trail in the circuit layer network, a pathis a trail in the path layer network, and asection is a trail in the transmissionmedia layer network.A circuit layer network provides telecommunicationservices to users, e.g.circuit-switched, packet-switched andleased-line services A path layer networkis used by the circuit layer networks.A transmission media layer networkis used by the path layer network. Itis dependent on the transmission media(e.g. optical fibre, radio) and can be dividedinto a Section Layer and a PhysicalMedia Layer, fig. 11.The information in a layer is carried by atrail consisting of trail terminations (T)and connections (C). A trail is terminatedby a Trail Termination Point (TTP).Network connections are terminated byTermination Connection Points (TCP). AConnection Point (CP) marks theboundary between connections. TTP,TCP and CP are reference points consistingof an output port for functionsperformed (source) and an input port forfunctions to be performed (sink). Theinput and output ports of a reference


158Fig. 12Partitioning of a network into subnetworkspoint are connected in a binding relationship.Each transport layer may contain severaltrails. For example, TL1 in fig. 9 hastwo 64 kbit/s trails. A network layer isdefined by the type of characteristic informationtransferred over its trails. In amultilayer configuration, client-to-serverrelationships exist in an iterative mannerbetween adjacent layers.Some of the existing definitions for thePDH have to be changed or new definitionshave to be adopted to permit theuse of the generic network layeringmodel for mixed SDH-PDH networks.However, the described principles canbe applied to all types of network, suchas SDH, PDH and ATM (AsynchronousTransfer Mode).Fig. 11 shows some examples of trails inthe three layers (circuit, path and transmissionmedia) of the SDH and the2 Mbit/s based PDH. Three of the examplesare explained in more detail. Iterativeclient-server relationships betweentrails, according to fig. 10, areused to describe the signal transport.Plesiochronous signal transportA plesiochronous 34 Mbit/s circuit betweentwo data terminals is carried by a140 Mbit/s digital path and a 140 Mbit/sdigital section using a coaxial cable.The plesiochronous network used isshown in fig. 15.Synchronous signal transportA synchronous 2 Mbit/s circuit betweenISDN terminals is carried by a lower orderVC-12 path, a higher order VC-4path, an STM-1 Multiplex Section, andan STM-1 Regenerator Section whichuses an optical cable in the PhysicalMedia Layer. This example is identicalwith the one shown in fig. 6. It correpondsto the following of a horizontalline from 2 Mbit/s to STM-N in fig. 2. Thesynchronous network used is shown infig. 16.Mixed SDH-PDH signal transportA plesiochronous 64 kbit/s circuit betweendigital telephones is multiplexedto a 140 Mbit/s path (plesiochronoustrails). The plesiochronous 140 Mbit/ssignal is mapped into a higher orderVC-4 path and transmitted over an opticalcable (synchronous trails). This casecorresponds to the plesiochronous140 Mbit/s signal being mapped intocontainer C-4 in fig. 2. The mixed networkused is shown in fig. 17.In fig. 11, which does not show all theexisting signal transport cases, a linebetween a 140 Mbit/s plesiochronoustrail and asynchronous VC-4 trail wouldbe needed to illustrate the case in point.Network PartitioningPartitioning of a layer network can bedescribed by means of Topology TransportFunctions, i.e. a layer network consistsof subnetworks connected bylinks. Each subnetwork, in turn, may bedivided into new subnetworks and linkedthrough an iterative process. The divisionis normally based on routing andmanagement demands. Fig. 12 shows atransport network layer representing regionalsubdivisions. Transfer of informationthrough a subnetwork is bymeans of a subnetwork or degeneratesubnetwork connection. Subnetworkconnections are interconnectedthrough link connections.Fig. 13 illustrates the connection optionsin a layer as a consequence of networksubdivision. The end-to-end connectionthrough a network has been


159Fig.13Link and network connections in the subnetworksshown in fig. 12^—^— Subnetwork connection^=^z= Link connectionFig. 14Example of a degenerate subnetwork with lineterminals connected "back-to-back"TLCSNCLCDeg SNCTandem Link ConnectionSubnetwork ConnectionLink ConnectionDegenerate Subnetwork Connection


Fig. 15 (above)Transmission of a plesiochronous 34 Mbit/ssignal between two data terminals over multiplexersand a 140 Mbit/s line systemLTRegATLine TerminalRegeneratorClient-to-server adaptationTrail terminationFig. 16 (below)Example of an SDH network transmitting 2 Mbit/ssignals over an STM-1 line system. The degenerateadaptation between the regenerator andmultiplex sections is not shown


Fig.17Transmission of a plesiochronous 64 kbit/s signalover a mixed plesiochronous synchronousnetwork. Functional description of the transmissionnetwork. The regenerator section and physicalmedia layers are not shownsplit up into a number of link and subnetworkconnections according to thedivision into subnetworks.Examples of transport networksA number of network examples are givenin order to illustrate the use of thetransmission and transport networkconcepts. For the sake of clarity, thephysical media layer - e.g. cable - hasbeen omitted.Fig. 14 illustrates the degenerate subnetworkconcept. A degenerate subnetworkconnection is created when lineterminals are connected "back-toback".A monitoring point for line systemsin the transmission network is obtained.Command-controlled switchingis not possible, however.Fig. 15 shows the transmission of a plesiochronous2 Mbit/s signal betweentwo data terminals over a transmissionnetwork consisting of digital multiplexersand a 140 Mbit/s line system overcoaxial cable. The transport networkcomprises three layers: a 34 Mbit/s circuitlayer, a 140 Mbit/s path layer, and a140 Mbit/s digital section layer. The layersare separated by Layer AccessPoints. Connections can be supervisedat the access points for the differenttrails.Fig. 15 also shows the relationship between- the physical implementation, with theassociated functional blocks in thetransmission network- trails (circuit, path, section) with theassociated functional blocks in thetransport network.Fig. 16 shows the transmission of2 Mbit/s signals in an SDH network overan STM-1 line system. Each SDH multiplexercontains the functional blocksshown in fig. 6.Figs. 17and 18show thetransmission ofa plesiochronous 64 kbit/s signal overa mixed plesiochronous/synchronousnetwork, consisting of telephones, localexchanges, digital multiplexers, andcross-connects. A functional representationof the transmission network canbe obtained according to the principlesdescribed earlier.Fig. 17 shows a simplified network model,indicating adaptations, terminationsand trails. This model can be used forfault management.Fig. 18 shows the subnetworks involvedin the example; the model outlined isrequired for configuration management.Table 10 illustrates - for the network infig. 18 - the topology in the VC-4 layer,which uses link relations over the STM-1layer. The topology of the complete networkrequires the corresponding analysesof all network layers involved.The management of the telecom networkis based on TMN Application Functions,such as Fault Management, PerformanceManagement and ConfigurationManagement, which treat thevarious atomic parts of the network asmanaged objects. Transport Functionsand Transport Reference Points arethose network resources which lead toTermination-Point managed objects inan information model. (TerminationPoints which are managed objectsshould not be mistaken for ConnectionPoints which are Reference points in afunctional model of the network).Termination Points of trails (paths andsections) can be used for fault and performancemanagement. Linking of TrailTermination Points is also necessary forconfiguration management. TerminationPoints are treated as managed objectswith manager-agent properties,their link and list relations being specifiedby the information model of thenetwork. The details of the managed objects,their attributes and values, notificationsand names are stored and handledby the TMN.


Fig.18Network partitioning: the network shown in fig. 17divided into subnetworks. The topology of theVC-4 higher order path layer is shown. This layeruses link connections in the multiplex sectionlayerTable 10Example of network topologyReferencesCCITT RecommendationsG.707, Synchronous Digital HierarchyBit RatesG.708, Network Node Interface forthe SDHG.709, Synchronous MultiplexingStructureReport Com XVIII R33E, Geneva,May 1990Andersson, J.O.: Digital Cross ConnectSystems, a System Family forthe Transport Network. Ericsson Review67 (1990) :2, pp. 72-83.Widl, W.: CCITT Standardization ofthe Transport Management NetworkEricsson Review 68 (1991):2.CCITT Rec. M.30 Principles for aTMNSoderberg, L: Architecture for IntelligentNetworks. Ericsson Review66 (1989) :1, pp. 13-22.CCITT Draft RecommendationsG.781, Structure of Recommendationson multiplexing equipment forSDHG.782, Types and general characteristicsof SDH multiplexing equipment10.G.783, Characteristics of SDH multiplexingequipment functionalblocksG.784, SDH managementTD14, WP XV/3, Geneva, July 1990CCITT Draft RecommendationsG.sdxc-1, Structure of Recommendationson cross-connect equipmentfor SDHG.sdxc-2, Types and general characteristicsof SDH cross-connectequipmentG.sdxc-3, Characteristics of SDHcross-connect equipment functionalblocksTD 5, 6,7 WP XV/3, Geneva, Feb 1991CCITT Draft RecommendationsG.957, Optical Interfaces for SDHequipment and systemsG .958, Digital Line systems based onSDH for optical cablesTD11, 12, WP XV/5, Geneva, July1990CCITT Draft RecommendationG.tna, Transport Network ArchitectureWD 3, WP XV/6, Geneva, Feb 1991CCITT Draft RecommendationG.Fmvx, Characteristics of a FlexibleMultiplexer in a PDH environmentTD61, WP XV/3, Geneva, Feb. 1991


FMAS-An Operations Support Systemfor Transport NetworksHenry TarleEricsson has developed a Facility Management System (FMAS) enabling networkoperators to improve the administration, supervision and control of transportnetworks and leased lines. FMAS forms part of Ericsson s TMOS(TELECOMMUNICATIONS MANAGEMENT AND OPERATIONS SUPPORT) familyof systems, which contains products that can be combined to provide efficient,flexible operations support for the entire telecommunications network and itsservices.The author describes FMAS and its potentials for making operations supportmore efficient.telecommunication networkmanagementtelecommunication networksOverviewThe need for new sophisticated telecommunicationsservices is rapidlygrowing; as are demands for greateravailability and higher quality of theseservices. Operators require transportnetworks with a high degree of flexibilityto be able to provide the requested servicesat short notice. At the same time itis essential that network operators canachieve efficient and cost-effective utilizationof their transport networks. Inorder to meet all these needs Ericssonhas developed a system family, TMOS(TELECOMMUNICATIONS MANAGE­MENT AND OPERATIONS SUPPORT),containing products that together canprovide operations support for an entiretelecommunications network, and itsservices. The Facility Management System,FMAS, which forms part of theTMOS family, provides operations supportdedicated to transport networks,including leased-line services. Basically,this operations support can be dividedinto administration, supervision andFig. 1FMAS enables the network operator to superviseand control the transport network and its leasedlines from a terminal in an operations centre. Thedisplay shows three different types of digitalcross-connect system in a network node. Thedesired operations are ordered with the aid of thekeyboard and the mouse


control and can involve the whole transportnetwork with its individual networkelements and circuits.A key benefit of FMAS is its ability tosupport centralized supervision of acomplete transport network. Based onCCITT/TMN principles, FMAS integratesthe administration and control of networkelements from different vendors;Digital Cross-Connect systems (DXC)and transmission products of the synchronous(SDH) and plesiochronous(PDH) digital hierarchies. FMAS is designedto meet increasing managementneeds and can manage transport networksin a hierarchical fashion.FMAS (TMOS) offers a programmingtool that can be used to design applicationsas well as adaptations to networkelements not supplied by Ericsson.To network operators FMAS means increasedcost-efficiency of network operationsby automating the managementof leased-line services, networkperformance/control and preservation,etc. An increased utilization of networktransport resources in the order of 10-25 % may be possible through the AutomaticNetwork Protection Routing facility,and a further 10-25 % through efficientrepacking of digital transmissionsystems. This is achieved by combiningFMAS with Ericsson's highly flexibleDXC systems and SDH multiplexers.FMAS also offers a network planningtool for efficient optimization of complextransport networks.To priority customers FMAS typically offersincreased and controlled serviceavailability and service quality. Networkoperators can provide leased lines atshort notice, and an optional service enablesthe customers themselves to selectroutes and bandwidths for their circuits.Box1ABBREVIATIONSADM Add/Drop MultiplexerAIS Alarm Indication SignalAU Application UnitAXE Ericsson's digital circuit switchingsystemCAP Common Application PlatformCSM Central Subscriber MultiplexDCN Data Communications NetworkDXC Digital Cross-ConnectECC Embedded Control Channel in SDHsystemsFMAS Facility Management SystemFMAS/N FMAS for centralized control of a nationalnetworkFMAS/Ft FMAS for control of a regional or metropolitannetworkFMAS/L FMAS for local control of network elementsin a nodeLAN Local Area NetworkLCN Local Communications NetworkMAS Management Application System inTMOSMML Man Machine LanguageMTP Message Transfer Protocol.Ericsson's X.25 protocolNE Network ElementNMC Network Management CentreOMC Operation and Maintenance CentreOSOSIPCMPDHOperations SystemOpen Systems InterconnectionPulse Code ModulationPlesiochronous Digital HierarchyPOSIX Portable Operating System Interfacebased on UNIXQ Q-interface, a TMN protocol0DCN Q-interface for communication via anX.25 DCN in accordance with CCITTFtec. G.773 (previously Q3)Q LCN Q-interface for local communicationin accordance with CCITT Rec G.773Q-stack (previously Q2)RSM Remote Subscriber MultiplexSDH Synchronous Digital HierarchySDXC Synchronous Digital Cross-ConnectSMN SDH Management Network, the supportinformation carried by ECCSQL Standard Query LanguageSTM Synchronous Transport ModuleTAP Telecommunication Application PlatformTMN Telecommunications ManagementNetworkTMOS Telecommunications Managementand Operations SupportUNIX An operating system for multi-usersystems. UNIX is owned by Unix InternationalCorporationWAN Wide Area NetworkWS WorkstationXy'Open An international consortium of majorcomputer manufacturers, dedicatedto setting standards which permit thesame software to run without modificationon a wide variety of computersystemsX.25 A standard protocol, specified byCCITT for packet-switched data communicationbetween computers andrelated equipmentFMAS operations support applicationsare based on an open standards (X/Open, POSIX, OSI) computing platform(CAP) which is used in all TMOS applications.The TMOS architecture provides aframework for the network operators'own applications. It combines the latesttechnology and knowhow in the fields oftelecommunication and data processing.In addition to FMAS, the followingTMOS operations support systems aredefined, fig. 2:BMAS Business Management Systemfor centrex and virtual privatenetworksCMAS Cellular Management Systemfor mobile telecommunicationsnetworksNMAS Network Management Systemfor switched networks, e.g.AXE switching and SS7 signallingnetworksSMAS Service Management Systemfor intelligent networks.FMAS can interwork with other TMOSsystems, thus ensuring efficient operationssupport for an entire telecommunicationsnetwork.


165Transport networkEvolutionTraditionally, digital transmission networkshave been built up of separate,physically interconnected plesiochronoustransmission systems. Basic transmissioninterfaces have been standardizedto permit interconnection ofproducts from different vendors. But thefact that the transmission systems representdifferent maintenance principlesand interfaces has limited the possibilitiesof efficient centralization of operationand maintenance. 1,2This situation was acceptable when telephonetraffic was stable and fairly predictable.Now, demands from businesscustomers are becoming increasinglystringent, in pace with the introductionof new sophisticated services. There is aneed for managed transport networksthat can be centrally operated and maintained,provide automatic network restorationand permit control of transmissionquality.Transmission systems of the new SDH(Synchronous Digital Hierarchy) standardwith embedded control channelsfor maintenance information, and operationssupport systems with standardizedinterfaces, will provide the necessarybasis for flexible and controllabletransport networks.The integrated approach to transportnetworkingTransport Network Management ArchitectureEricsson's Transport Network ManagementArchitecture integrates operationssupport/control systems (FMASs), the(built-in) local control of the transmissionsystems, and the interlinking datacommunication facilities. The architecturepermits a hierarchical division ofoperations support, corresponding tothe local, regional and national levels ofa transport network. Various transportnetwork elements - Ericsson's as wellas those of other suppliers - can becontrolled from FMAS.Evolution towards a managed synchronousnetworkThe chosen architecture permits simple,step-by-step transition from existingPDH (Plesiochronous Digital Hierarchy)networks - with their operationssupport systems - to the centrally managedSDH networks of tomorrow, at apace set by the network operator. Itshould be noted that FMAS also permitsenhancement of the operations supportof existing PDH networks.The introduction of an SDH networkmeans that current investment in opticalfibre cable can be exploited to the full.SDH systems can be introduced as smallislands in an existing network or in theform of an overlay network.Fig. 2Example of networking between TMOS ApplicationSystems, maximizing total network operationssupport and service efficiencyBMAS Business Management System for centrex andvirtual private networksCMAS Cellular Management System tor mobile telecommunicationsnetworksNMAS Network Management System tor switchednetworks, e.g. AXE switching and SS7 signallingnetworksSMAS Service Management System for intelligentnetworks.NE Network Element


166FMASFig. 3FMAS provides operations support for transportnetworks comprising network elements, such asDXC systems and SDH and PDH transmissionsystems. Communication between FMAS andsupported network elements is via a data communicationsnetwork using the Q-interfaces recommendedby CCITT for TMN (TelecommunicationsManagement Network)SDHPDHDCNDXCSynchronous Digital HierarchyPlesiochronous Digital HierarchyData Communications NetworkDigital cross-connect systemEricsson's new Transport Network ManagementArchitecture is a total approachto successful operations support.Its implementation reduces thecosts of network operation and maximizesthe revenue-earning potential ofthe transport network.Ericsson's product program fortransport networksEricsson's product program for transportnetworks, defining the EricssonTransport Network Architecture, comprises:- A family of SDH transmission systems- A family of digital cross-connect systems(DXC)- A family of PDH transmission systems- A facility management system(FMAS).Similarities between different systemsare used to the full. For example, in thecross-connect systems the interfaceprinted board assemblies are the sameas those used in the SDH transmissionsystems, and their computing platform(CAP) is the same as in FMAS.SDH transmission systemsThe SDH transmission systems constitutea new product family which conformsto the CCITT recommendationsG.707, G.708 and G.709 for SDH:ZAP 155 An optical fibre system with abit rate of 155 Mbit/s (STM-1)for transport of up to 63 x2 Mbit/s signalsZAP 250 An optical fibre system with abit rate of 620 Mbit/s (STM-4)for transport of up to four140 Mbit/s signalsZAP 250 An optical fibre system with abit rate of 2.5 Gbit/s (STM-16)for transport of up to 16 x140 Mbit/s signals.The systems include line terminals, adddropmultiplexers and regeneratorsThey can be used to transport current1.5,2,34 and 140 Mbit/s PDH signals andalso future broadband signals.Digital cross-connect systemsThe digital cross-connect systems(DXC) constitute a new product familydesigned to provide network protection,and to improve management and utilizationof lines and the quality of leasedline services. 3 They function as semipermanentswitches for transmissionchannels with holding times of hours,days or weeks. They perform, understored program control, transparentswitching of digital transmission channels,which may be tributaries in higherordertransmission systems.Ericsson's digital cross-connect systemsconform to CCITT recommendationsfor DXC and SDXC (SynchronousDigital Cross-Connect). The programcomprises three different types of system:DCC1/0, DCC4/1 and DCC 4/4. Across-connect node may have commoncontrol equipment while the individualcross-connect systems have differentswitches in order to meet various requirements.Fig. 4Traditionally, cross-connections have beencarried out manually, for example between digitalmultiplex and line equipment in coaxial digitaldistribution frames located in terminal repeaterstationsDCC 1/0 Terminates signals with bitrates 64 kbit/s, 1.5 and2 Mbit/s. The signals are sorted,packed and cross-connectedat the N x 64 kbit/s level(N=1-31)DCC 4/1 Terminates signals at between1.5 (2) and 155 Mbit/s and


167Fig. 5Example of a transport network with operationssupport. The diagram shows Ericsson's operationssupport system and network elements andthe data network that transmits control informationFMASQSTMSDXCPNESNEADMFacility Management SystemQ-interface in TMN, in accordance with CCITTSynchronous Transport ModuleDigital cross-connect systemPDH Network ElementSDH Network ElementSDH Add/drop Multiplexercross-connects primarily 2, 34and 140 Mbit/s signalsDCC 4/4 Terminates 140 or 155 Mbit/ssignals and cross-connects atthe same level. Also providesinterfaces for STM-4 andSTM-16 signals.PDH transmission systemsEricsson's product program "Series7000 Plus" for the plesiochronous digitalhierarchy comprises:- PCM and RSM/CSM multiplexers anddigital multiplexers for 2/8, 8/34 and34/140 Mbit/s- Symmetric-pair line systems for2 Mbit/s- Optical fibre line systems for 8, 34,140 and 565 Mbit/s- A Transmission Operation and MaintenanceSystem for integration intoan FMAS operations support network.FMAS - Facility Management Systemfor transport networksThe facility management system FMASis designed to support the operation ofnew SDH, DXC and PDH systems, fig. 3.FMAS is based on a computing platformused in all TMOS systems.The continuous development of FMASwill result in the ability to provide networkmanagement for transport networksconsisting of new and differenttypes of network element. A uniformTMN/Q-interface between FMAS andthe network elements will enable an operatorto obtain a consistent networkmanagement environment for his transportnetwork.ApplicationsThe new network elements representedby DXCs and SDH multiplexers are ofparticular interest. The latter are availablein different versions with slightlydifferent functions, fig 5:ADM Add-drop multiplexers make itpossible to open an STM-N signaland drop or insert signals oflower-order bit rates. For example,a 2 Mbit/s signal can bedropped directly from an STM-1signal (155 Mbit/s) without anydemultiplexingSDH SDH multiplexers provide multiplexingof signals from thePDH and SDH hierarchies intoSTM-1, STM-4 or STM-16 signals,and vice versaSDXC The digital cross-connect systemsDCC 4/1 and DCC 4/4 canswitch transmission channelswith the desired bandwidth andalso form a bridge between PDHand SDH networks.


168Fig. 6FMAS significantly reduces operating costs fortransport networks, while increasing the availabilityand performance quality of the transportnetwork and supported servicesStrategic benefitsNew and extended demands on thetransport network are mainly made bylarge enterprises that are dependent onconnections beteween their privatenodes. They need communications- between PABXs- between computers- between MANs (Metropolitan AreaNetworks)- between WANs (Wide Area Networks)- for video conferences.Such major customers require highavailability and performance and shortservice delivery time. Network operators,on their part, want to reduce theircosts. FMAS and supported DXC andSDH transmission products offer costefficientsolutions to these problems -solutions that may turn present operatingcost trends in a more favourabledirection, fig. 6.FMAS offers network operators andtheir customers strategic and competitivebenefits, as described below.Benefits to network operatorsImproved operations support- Operations support of a completetransport network. A key feature ofFMAS is its ability to support networkoperators with centralized management,integrating and coordinatingthe administration and control of differenttypes of network element- Automation of configuration and performancecontrol of leased-line servicesand transport circuits, rangingfrom 64 kbit/s to broadband- Automation of operation and maintenanceof network elements (DXC,SDH, PDH).More efficient use of network resources- Increased network utilization in theorder of 10-25%. FMAS increasesthe pay-off from network investmentsthrough the Automatic Network ProtectionRouting facility, primarily operatingon DCC4/4 and 140 (155)Mbit/s transport circuits. In the caseof a network failure, FMAS automaticallyand in real time orders the DXCs


169Table 1Equipment Typical applications of FMAS andnetwork elementsDCC 1/0 Management of leased lines forn x 64 kbit/s (n = 1 -31), e.g. settingup 64 kbit/s leased lines andpaths through the network.64 kbit/s signals can be sorted andpacked in DCC 1/0 nodes to give2 Mbit/s transmission systems ahigh fill factorDCC 4/1 Automated management of circuits,from 2 Mbifs up to 140/155Mbit/s. With its ability to handle allbandwidths. it improves the fill factorsof existing 140/155 Mbit/stransmission networks. It replacesthe traditional back-to-back multiplexingin exchanges. Bridging betweenSDH and PDH networks canbe arrangedDCC 4/4 Automatic protection routing of140/155 Mbit/s circuits in case ofcircuit failure. Provisioning ofbroadband leased-line services,etc.SDH/PDH Centralized alarm supervision, faultlocalization, performance monitoring,provisioning of circuits, synchronousadd/drop multiplexing,etc.to set up the logically best alternativeroute between end points in the network- Increased line system fill factor by10-25 %. Efficient repacking of lower-orderline systems into higher-ordersystems will increase the fill factor.This is achieved by combiningFMAS with Ericsson's highly flexibleDXC and SDH multiplexers- Bridging between SDH and PDH networks.The combination of EricssonDXCs and FMAS permits the interfacingbetween optical transmission systems,using the SDH standard, to begradually and smoothly introducedinto an existing PDH network. Thismeans that there will be no need foroperating a separate SDH network- Modular expandability. FMAS permitsa network operator to economicallycontrol anything from a singleDXC, using a basic FMAS single workstationconfiguration, to an FMASmulti-computer configuration controllinga large number of networkelements of different types- FMAS-TMOS networking. SinceFMAS is built on the TMOS commonplatform completed by FMAS applicationsoftware, FMAS can cooperatewith, or incorporate wholly or partially,the other members of the TMOSfamily. This will guarantee a networkoperator full flexibility and adaptabilityto future needs of operations support.Less complex network layout and easyplanning make for reliable and efficientoperation- Hierarchic configuration. Operationssupport can be divided into hierarchiclevels, e.g. local (node), regionaland national. FMAS operations centrescan be allocated different geographicalareas in a "flat" network ordifferent transport network layers(logical levels) of an SDH network 4- Network planning tool. The FMASNetwork Planning Tool (NPT) may benecessary for routing optimizationand fault tolerance evaluation. TheNPT operates on a network modelthat can easily be updated from theFMAS operating database- Duplicated FMAS. FMAS can be duplicatedso that operation can bemaintained even in case of a systembreakdown. The two systems - oneexecuting and the other standby -may be placed in geographically separatecentres- FMAS benefits from all the significantcharacteristics and features of theTMOS concept.Benefits to customersIn response to business customerneeds, FMAS offers the following importantquality and time and cost savingbenefits.- Increased service availability. The automaticprotection routing system reconfiguratesthe network in the caseof a failure in a path or circuit. Leasedlines can be allocated different priorityclasses. They can thus be giventhe highest possible availability whenrequired- Secured service quality. Throughmonitoring and performance analysesof leased lines, FMAS permitscontracted service quality to be secured.Weak parts of the network,with deteriorated performance, canbe detected early and localized- Service privisioning with short deliverytime- Customer control of leased lines, enablingend users to partly controlrouting and bandwidth reconfigurationsof their own circuits.ApplicationsTypical applications for differentnetwork elementsCertain applications can be consideredmore or less typical of the network elementin question, table 1.Major FMAS applications providing operationssupport for transport networksand leased lines are described in thefollowing section. DXC and SDH/PDHsystems are used in the way described intable 1.MANAGEMENT OF THE TRANSPORTNETWORKCompliance with internationalstandardsFMAS applications are based on theManagement Framework defined byOSI (Open Systems Interconnection)principles for the TMN (TelecommunicationsManagement Network). Accordingto these standards/recommendations,


170FMAS functions/applications are categorizedin a number of functional areas,fig. 7.Configuration managementFMAS configuration management functionsprovide means for adding and removingnetwork elements and paths/circuitsin the transport network. Facilitiesfor network restoration and networkplanning are also supported. Some examplesof functions are given here.Network configurationNetwork configuration denotes a groupof functions needed to identify and configurephysical resources in order toachieve a network infrastructure, theputting into service and removal of networkelements and their physical interconnections,or of equipment in the networkelements, etc. Whenever changesare made, the FMAS database is updatedPath and circuit provisioningPath and circuit (leased-line) provisioninginvolves the establishment of logicalconnections through the network. Thepaths/circuits are set up by FMAS issuingcross-connect commands to theDCCs. Provisioning can be made ad hocwhen ordered by the operator or accordingto a predefined schedule.Scheduling of reconfigurations is a valuabletool that enables the operator tomeet customers' demands for flexibilityand to utilize network resources moreefficiently over periods of specifiedlengths.Protection switchingFor a transport network section a protectionswitching function (1:N) can bedefined from FMAS. This switchingfunction is invoked autonomously bythe network elements at both ends ofthe section in which a transmission failurehas occurred. The function is limitedto switching to a standby network resourcebetween the original pair of networkelements.Protection routingIn the case of a network failure - loss ofsignal, high bit error rate, a major cablefailure, etc. - the protection routingfunction automatically and in real timerestores the affected paths and circuits(leased lines), fig. 8. FMAS builds up analarm picture of all alarms arriving fromthe network elements concerned. A protectionrouting analysis is then made byFMAS based on this alarm picture, onthe preset priorities of the affectedpaths, etc.Fig. 7FMAS functional areas according to TMN principles


171Fig. 8Automatic protection routing controlled by FMAS.The necessary rerouting is performed in DXCsystems on command from FMASFMAS calculates a new optimal routingfor all paths/circuits affected by thefault. Then the appropriate orders areissued by FMAS to each individual networkelement, which performs the desiredsequence of cross-connections.FMAS is capable of restoring paths atone predefined bit rate level; that is, atone multiplexing level between 1.5/2and 155 Mbit/s.If requested by the operator, the protectionrouting function can be set to amode that requires the rerouting to beacknowledged before being effected byFMAS.Fault managementFMAS fault management functions minimizethe impact of failures on servicethrough functions for fault detection,identification and localization. This supportenables the operator to make decisionson corrective action with a minimumof delay.Alarm supervision and monitoringFMAS checks the operating status of- the FMAS system- network elements- paths and circuits- the links between FMAS and the networkelements.FMAS requests and receives from thenetwork elements alarm signals that indicatestatus changes, such as loss ofsignal, synchronization error and highbit error rate. On the basis of these reports,FMAS determines the nature andseverity of a fault and informs the operator.All alarms are logged, togetherwith the operator's confirmation andcomments.Alarm analysis and fault localizationFMAS analyses alarms in order to beable to identify and locate network failures.Alarm filtering is used to trace thesource of a major alarm by separatingprimary and secondary alarms. For example,when a transmission fault resultsin many network elements sendingalarm indication signals (AIS), FMASanalyses these signals to localize thesource of the fault.Alarm reportingFMAS presents alarm reports, whichcan be tailored to the requirements ofthe network operator. Reports can bepresented via terminals and printers orbe displayed graphically on workstationVDUs.TestsFault diagnosis and localization is facilitatedby FMAS functions that automaticallyorder network elements to carryout tests. These tests are chosen on thebasis of continual analysis of the alarmsituation. Actions that can be orderedinclude: testing of circuits betweenFMAS and network elements or of thelatters' hardware and software, loopbackof traffic, injection of error signalsto test alarm functions. Tests can also beinitiated on operator command.Performance managementFMAS performance management functionsanalyse the quality of service andoverall performance of the transportnetwork.Performance monitoringThe status and performance of the networkare monitored continuously by thenetwork elements, from their own perspective.FMAS requests data from the


172network elements and collects andstores this information for further processing.FMAS produces reports on path/circuit end-to-end performance: bit errorrate, unavailable seconds, erroredseconds, etc.Network performance analysisFMAS network performance analysisfunctions produce information on variousissues from data collected from thenetwork elements. Causes for intermittenttraffic fault conditions and othertypes of troublesome degraded performancecan be analysed and localizedto a specific equipment, transport networksection, etc. This will help operatorsto direct preventive maintenanceto where it is needed.Performance reporting and presentationFMAS can produce performance reportson command from operators, onschedule or when a preset threshold valuefor some parameter has been exceededPerformance reports can be tailoredto the operator's requirements.They can be presented on terminals,printers or graphically on workstationVDUs.Security managementFMAS functions for security managementprotect the resources and servicesof the transport network, for example:Transaction securityFMAS allows for assigning different levelsof authority and user profiles to differentoperators. Thus, operators' accesscan be limited to those FMASfunctions which they have been trainedto handle and which concern their individualtasks.Data communication securityCommands from other FMASs and externaloperations systems are checkedas regards the authority of the source,the validity of the command and consistencywith previously received commands.MANAGEMENT OF LEASED LINESTMOS/FMAS supports management ofleased lines of various bandwidths in anumber of functional areas, such as:- Configuration management- Fault management- Performance management- Security management- Charging- Customer control.FMAS provides a central resource formanaging leased-line services of variousbandwidths; their provision, the collectionand analysis of data relating toquality of service, security managementand automated billing and accounting.Customers can be assigned differentFig. 9FMAS Network Planning Tool


173Fig. 10The FMAS graphics user interface, which is basedon Open Look, supports the use of the NetworkPlanning Tool (NPT) included in the system. Inthis example the NPT is used to display thecurrent network diagram (View), to input currentnetwork data (File) and to calculate (Analysis) theeconomically optimum path (Shortest Path)between two network nodes. Other calculationsgive the maximum transport capacity and showpotential bottleneckspriority levels in the network, which allowsthe network operator to offer premium-qualityservices to subscriberswho require them.Customer controlNetwork operators can offer their moreadvanced customers control of leasedlines. Such a customer, usually a largecompany with geographically distributedunits, is given its own "logical"FMAS which controls the company'stransport network including all leasedlines. The customer only sees and manageshis own virtual private network andhas no detailed knowledge of the completetransport network.A first step towards complete customercontrol is to provide the customers withnetwork information, such as- the results of performance monitoring,e.g. quality-of-service parameters- fault management data, e.g. alarms inthe virtual private network- an overall view of their "own" network.The right to information can be providedas an individual service, separate fromthat which permits the customer tomake changes in the network by meansof commands.NETWORK PLANNING TOOLThe FMAS Network Planning Tool, NPT,is an efficient aid for network operatorsin planning transport networks with ahigh degree of complexity, fig. 9. Themain applications are described here.Network designThe network planner can plan and optimizea new network, or modify or extendan existing network.Analysis, test and simulation of networkbehaviourThe planner can determine the degreeof utilization and efficiency of a network.He can also simulate differentfault situations or additional traffic loadand in this way determine the survivabilitymargin of the network.NPT environmentThe NPT provides a graphics, menu-drivenuser interface, similar to that ofFMAS. This facilitates an FMAS operator'sinterpretation of the networkplanning environment, fig. 10.


174Fig.11Example of the division of the overall FMASoperations support function into hierarchic levelsFMAS/NFMAS/RFMAS/LNEOSQDCNLCNCentralized national FMAS for control of one ormore regional transport networksRegional FMAS for control of one or more localtransport networksLocal FMAS for control of one or moreindividual network elements in a network nodeNetwork ElementExternal Operations System connected toFMASO-lnteriace In TMN in accordance with CCITTData Communications NetworkLocal Communications NetworkThe NPT can be connected to a networkoperating FMAS, thus allowing the networkplanner to easily transport all necessaryinformation on-line from the continuouslyupdated FMAS network databaseto the NPT. The network plannercan also send planning results from theNPT to the operating FMAS. The NPTcan also be run, independently of anoperating FMAS, on its own separatecomputer system, CAP.Network control architectureLocal, regional and national controllevelsFMAS management functions can be dividedinto different hierarchic functionlevels: local (FMAS/L), regional (FMAS/R) and national (FMAS/N), fig. 11. Physically,this functionality may be integratedinto one, or divided into a number ofoperations sites. For example, in someimplementations FMAS/N may have onlya rudimentary picture of the network;all detailed administration of individualnetwork elements is left to the lowerlevelFMAS/R and FMAS/L systems. Inother implementations all FMASs mayhave access to the same detailed information.Advantages of a hierarchic controlstructureOperations support systems - such asFMAS - that permit a hierarchic controlstructure offer a number of major advantages.Decentralization for greater operationalreliabilityThe impact of a system breakdown of acentralized (national) support system isconsiderably reduced. In such a casethe lower-level support systems maintaincontrol over their networks.Hierarchic control structure of a flattransport networkIn principle, each geographical area of alarge network can be planned and operatedindividually, which reduces administrationcomplexity. Different FMASscan interwork to coordinate activitiesthat concern more than one geographicalarea, fig. 12.A flat transport network is not layered;all resources in the network are placedin the same physical layer regardless ofbit rate, type of network element, etc.The network is partitioned into regionsof varying sizes, which in turn can bepartitioned into subregions at a lowerlogical level. The regions, with the associatedoperations support systems, maypreferably coincide with the geographicalareas of responsibility in the networkoperator's organization.Hierarchic control structure of a layeredtransport networkA transport network can be divided intolayers, fig. 13, primarily with respect tothe bit rates used. Each layer can beprovided with its own operations supportsystem and be controlled andplanned independently of the other layers.Such an arrangement has all theadvantages described above.Fig. 13 shows a simplified SDH transportnetwork divided into three layers(logical levels).- A national network based on STM-16systems for 2.5 Gbit/s, possibly withsome additional STM-4 systems for620 Mbit/s- Several regional networks, ring ormesh shaped, based on STM-4 systemswith some additional STM-1 systemsfor 155 Mbit/s- Several local networks, ring or meshshaped, based on STM-1 systems.


175Fig. 12Example of a "flat" transport network with ahierarchic control structureFig. 13Example of a layered transport network with ahierarchic control structure.Typical bit rates for the different layers areindicated


176types of DXC system, whereas AddDropMultiplexers (ADM) are used primarily inthe regional and local transport networks.In a hierarchic transport network withextremely reliable links between the layers(protection switching system 1:1 isused), each layer can be given its ownoperations support system that is independentof other layers. Protection routingis then best arranged separatelywithin each layer and is controlled bythe FMAS belonging to the layer. DifferentFMASs interwork in order to simplifythe problems associated with the provisioningof switching paths between subscribersbelonging to different FMAS regions.The example given shows thestrong relationship between the divisionof the transport network into layers andthe levels of operations support.Flexibility of the SDH ManagementNetwork (SMN)The new network elements, the DigitalCross-Connect Systems and SDH systems(Add/Drop Multiplexers, etc), canbe controlled by FMAS through a datacommunications network and throughEmbedded Control Channels (ECC) inthe SDH transport network.FMAS is capable of monitoring and controllingvarious types of SDH networkstructure in a flexible way. Fig. 14 showsan example with standardized Q-interfaces:Q/DCN and Q/LCN interfaces betweenFMAS and DCC/SDH network elements,and Q/ECC interfaces betweenSDH network elements. Control informationto a network element, with nodirect DCN link from FMAS, reaches itsdestination network element throughthe ECC after having passed other networkelements.Step-by-step implementation of SDHnetworks with operations supportThe flexibility of FMAS and the controlsystems in Ericsson's various networkelements permit different strategies forthe implementation of transport networkswith the associated operationssupport functions. A major advantage ofFMAS is that the support for PDH networkscan be integrated into the overalloperations support network.The following example shows step-bystepimplementation of a national trans-Fig. 14Example of an SDH Management Network (SMN)for control of DXC/SDH network elements fromFMAS. A star and a ring SDH Management Subnetwork(SMS-1 and SMS-2) are indicatedNMCSNEECCSMSNetwork Management CentreSDH Network ElementEmbedded Control Channel (In SDH circuit)SDH Management Subnetwork


177port network with operations support,fig. 15 The network is divided into twolayers, the long-distance network andregional networks. The latter also includemetropolitan networks The followingsteps are proposed.Step 1SDH line systems are introduced intothe long-distance network, and ADMrings are built up in metropolitan networks.An FMAS/LD for the long-distancenetwork managing the SDH linesystems (STM-4 and STM-16) is implemented,providing for basic functionality,such as collection of alarm and performancedata.The ADM ring networks are equippedwith local FMAS/L systems (not shownin fig. 15). FMAS/L contains functionsfor collecting alarm and performancedata and also functions that supporttraffic routing in the ring networks.Step 2DXCs are introduced into the long-distancenetwork, primarily for protectionrouting. The FMAS/LD system is upgradedwith functions to support themanagement of DCC 4/4 (STM-1). SpecificDXC functions and applications ofFMAS, such as protection routing, aretested and put into operation.Step 3Metropolitan networks are growing withthe introduction of more and largerADMs and DCC 4/1. More local FMAS/Lsystems are introduced and/or upgradedto support DCC 4/1 as well. A regionalFMAS/R system is introduced to serveas a superior management systemthroughout a Regional/Metropolitan area.This system also provides protectionrouting functions in this area.Step 4Regional and long-distance networkscontinue to grow, with further introductionof all types of network element. Thevarious FMASs for local, regional andlong-distance networks are graduallyupgraded with respect to processing capacityand functionality. A superiorFMAS function, FMAS/N, is introducedto provide coordination betweenFMASs and end-to-end control of circuitsthroughout the network.This and other introduction strategiesare possible, taking advantage of theheriarchic control structure of FMASand Ericsson's flexible SDH networkelements.Fig.15Example of a layered transport network withoperations support.The network is divided into two layers, both ofwhich contain DXC nodes. One layer contains thelong-distance network and the other regionalnetworks, some of which may be metropolitannetworksFMAS/LD FMAS supporting the long-distance network


178Fig.16A typical FMAS hardware configuration, comprisinga number of computers in servers and workstationsconnected via an LANLANXWSLocal Area NetworkGraphics terminalWorkstationFMAS system architectureGeneralFMAS configurations can be designedto match the individual transport networkrequirements as regards operationssupport, network size, etc. Thegeneral FMAS system architecture comprisesa number of FMASs, communicatingvia services defined in the TMN/Q/DCN and LCN interfaces over DataCommunications and Local CommunicationsNetworks, fig. 11.For communication with other FMASs,or operations systems from other vendors,FMAS provides a TMN/Q protocol.(TMN-Q covers services from all layers- 1-7 - in the OSI Reference Model. TheX.25 protocol is used for layers 1-3 inthis model).Foreach specific FMAS implementationthe system can be designed for the bestbalance of cost versus reliability. Differentversions are available, including afault-tolerant hardware variant. FMAScan be configured to operate economicallyfrom small to large numbers ofnetwork elements.System configurationThe FMAS hardware configuration canflexibly meet the network operator's requirementsin order to achieve properfunctionality and performance at thespecific site. Processor capacity, memorysize, number of communications interfacesand workstations etc. are allscalable Some examples are given below.A typical FMAS implementation consistsof a multi-computer configurationcomprising a number of servers, fig. 16.The database server has two discs attachedwhich can be used in what iscalled a mirror-write configuration, thusincreasing safety in case of failure onone disc. Different disc sizes are available.In the example shown in fig. 16 thedatabase server also acts as a file serverfor the other computers connected tothe LAN cluster.The application server can be dimensionedfor the intensive computing thatis required in certain FMAS applications.The communication server, which mayhold additional circuit boards, e.g. forthe X.25 interfaces, handles externalcommunication and closely relatedtasks.Each workstation includes a graphicscolour display and a mouse (pointingdevice) for use by the operator. FMASprovides an easy-to-use menu systemconforming to the Open Look specification.Configurations for large systemsThere is no maximum configuration ofthe FMAS operations system, whichmeans that each installation can beadapted according to site-specific conditions.Demanding applications mayneed a greater number of servers thanthose shown in fig. 16.Several workstations and X-terminalsfor FMAS operators' interaction areavailable, one of which can be used as asystem console.Configurations for small systemsThree different configurations are availablefor small FMASs:A data file server with a graphics VDUand at least one disc storeThe single server handles databases,communication and FMAS applicationsA workstation with disc storeThe CPU capacity is on par with thatof a file server, but the disc capacityand internal memory size are limitedalthough entirely adequate for mostsmall configurations


179Fig.17The FMAS graphics user interlace, which is basedon the Open Look industry standard, supportsfive functional areas, which are shown at the topin the main FMAS window.The area Performance Management has beenchosen from the menu, and the associated mainwindow is displayed. The relevant object isselected from the View items and displayedgraphically in suitable detail, but in this figure it ishidden behind another window. The next menuitem chosen is Monitoring, and the associatedpull-down menu is shown. From this menu, thewindows Parameters and Monitoring Interval havebeen chosen. In this example the displayedparameters concern a Path Termination Point(PTP).The desired alternatives are selected and activatedby the operator with the aid of the mousePersonal computerIf a PC is used, the system performancemust be analysed in each individualcase.Remote controlFMAS can be controlled remotely from astand-alone workstation connected viaa DCN. The workstation can be configuredin the manner described abovefor small configurations.User interfaceWorkstations for graphics presentationin accordance with the X Window System,an industry de facto standard forgraphics terminals 5 , can be connectedto the operators' user interface. The interfaceis designed so as to minimize therisk of operator errors, thus making operationssupport easy and cost-effective.Some characteristic features of theinterface are:Task-oriented menusFMAS users work in a user-friendly environmentbased on the Open Look UserInterface, providing task-oriented menusand forms tailored to each user'sunique job requirements. It is an applicationdesign task to define the menusand forms, using tools provided by CAPMulti-accessUsing FMAS menus, a user can performseveral tasks, for one or several FMASsor other operations support systems.Multiple active windows allow a user tostart an operation in one window and tocontinue in another with a minimum ofeffort and knowledge of backgroundoperations.Graphics presentationsFMAS displays network status, reportsand maps in a user-friendly graphics format,fig. 17.On-line helpWhen the Help key is pressed from anymenu screen, an FMAS 'help window"appears in a separate window, givinginformation at the relevant level of detail.FMAS - an ApplicationsSystem of the TMOS familyFMAS belongs to the TMOS family and


180Fig.18TMOS application systems can be created byselecting and combining Application Units (AU)from the TMOS source systemFig.19TMOS main building blocksFMAS, for example, comprises Application Units(AU) dedicated to transport network support, aswell as applicable AUs of the CAP and TAPplatformsAUTAPCAPApplication UnitTelecommunication Application PlatformCommon Application Platformbenefits from all the characteristic featuresof the family as described below.Integrated management of atelecommunications networkTechnology advancesTMOS belongs to the next generation ofoperations support (operation and management)systems that are focusing onnew and traditional telecom services inan competitive environment. It coversboth network and service management.The latest advances in the field of informationtechnology have been employedwhen developing TMOS operationssupport systems and relatedfunctions, in terms of reliability, manageability,capacity and user friendliness,etc.Physically, TMOS consists of a multicomputerconfiguration of workstationsand servers in a local area network(LAN). Operations support systems ofthe TMOS family can be employed by alltypes of operation and maintenancecentre (OMC and NMC).Integrated operations supportThe concept of integrated operationssupport means efficient management,within one concept/system, of the increasingcomplexity of operations in amulti-service and multi-vendor telecommunicationsenvironment.The TMN Q-interface standards underdevelopment in different standardizationbodies will pave the way for integratedoperation and maintenance.TMOS will fully support this interactionprocess - from present proprietary interfacesto open interfaces connectingdifferent network elements and operationssupport systems.Terms and definitionsTMOS comprises products that can becombined to meet the operations supportrequirements for different classesof applications, and a system for developmentof new functions and applications.TMOS - source system and applicationsystemsTMOS is a source system out of whichdifferent application systems can becreated by combining selected TMOSbuilding blocks (Application Units).A specific combination of buildingblocks that is selected, tested and deliveredis called a TMOS Application System,fig. 18.A central part of each TMOS applicationsystem is a relational database containinga model of the supported network.The model is continuously updated,with information from the network elements- e.g. alarms - and with commandsfrom and actions taken by thenetwork operation and maintenancestaff. Thus, the network model reflectsthe current status of the supported network.Management application systemsAt present, the following classes ofTMOS Management Application Systems(MAS) are defined:BMAS Business Management Systemfor centrex and virtual privatenetworksCMAS Cellular Management Systemfor mobile telecommunicationsnetworksFMAS Facility Management System fortransport networksNMAS Network Management Systemfor switched networks, e.g. AXEswitching and SS7 signallingnetworks


Fig. 20TMOS in a multi-vendor environmentTMOS/I TMOS system that integrates operations supportfor several areas, e.g. networks or network partswith equipment from different vendorsTMOS/E TMOS system for support of Ericsson networkelementsO-OS Operations support system for network elementsnot supplied by Ericsson. O-OS may be a TMOSsystemO-NE Network elements not supplied by EricssonSMAS Service Management System forintelligent networks.xMAS denotes any future TMOS applicationsystem not yet defined.Application UnitsAn MAS is a combination of ApplicationUnits (AU), some of which maybe identicalwith those of other MASs. An AU maycontain optional functions and alternativeperformance data.Platforms and programming toolsTMOS programming (i.e. design) capabilitiesare expressed with the TMOSplatform concept. ATMOS platform providesan open, layered infrastructure forthe implementation of application functions,fig. 19. 'Open', in this context,means that such functions can be developedby Ericsson or by network operators.TMOS has optional programming tools;a set of Application Programming Interfaces(API), suitable for C++ programming.The following functions can beimplemented with the aid of API andadded to the TMOS standard programs:- Extended or new applications- Gateway functions towards computersystems for administrative applications- Interfaces for connection of networkelements not supplied by Ericsson.The programming tools comprise a setof AUs including programming rules, anumber of APIs, a test environment anda list of suitable programming tools. AnAPI containsfunctionsforexternal communications,command handling, filemanagement, time activation, log handling,authorization checking, and accessto preprocessed data.The following platforms are now available,fig. 19:CAP Common Application Platform or"the computer system"CAP defines the computing environmentthat ensures an openand flexible architecture. CAPsupports the use of X/Open, UNIXSystem V, the database interfacelanguage SQL, C+ + , X WindowSystemTAP Telecommunication ApplicationPlatform or "the information system"TAP provides a network model databasethat stores the attributes ofeach network element and alsoalarms and commands. User (operator)interfaces to network facilities,etc, can also be included.Characteristics and benefitsOne system - many applicationsTMOS is a modular system. Different applicationsystems can be created bycombining a wide range of ApplicationUnits.This modularity and one-system featurewill provide the users with specificmeans to enhance operation, but withoutthe disadvantages of increasing thenumber of different systems.System interworkingThe modular structure of TMOS alsomeans that two or more application systems,such as FMAS and BMAS, can coexistand interwork on the same hardwareand software platform while stilloperating as independent applications.NetworkingThe TMOS concept provides flexible allocationand use of functions and resourceswithin and between interconnectedTMOS Application Systems. Forexample, status reports can be createdby processing data from different TMOSsystems and their supported networks,fig. 2.The benefits of networking betweenTMOS systems can be applied to differentmodes of operation. Strategically,this networking may provide a competitiveedge to an operator's ability to maximizenetwork and service efficiency,and to generate revenues.Support of a multi-vendor environmentTMOS programming tools can be usedto adapt TMOS to network elements andoperations support systems from othervendors, fig. 20. TMOS provides inter-


182faces that conform to TMN recommendations/specificationsdefined byCCITT, ANSI and ETSI, i.e. X.25, ACSE/ROSE, CMISE/CMIP and FTAM.The ability to handle equipment of differentmanufacture contributes to therealization of integrated network managementwith all its advantages, such ashigh quality of service, fast service provisioningand staff efficiency.Open application environment based onstandardsThe TMOS system architecture is preparedfor the management of new andfuture services and network concepts,and for the integration of new softwareand hardware technology. This is due tothe open system architecture and theuse of internationally agreed standards.PortabilityThe division of the TMOS system intothree separate components - CAP, TAPand application - means that any componentcan be improved or exchangedindependently. Industry standards areapplied throughout when designingTMOS and, hence, the system softwareas a whole can be transferred between anumber of different hardware platforms,enabling new technology to be introducedinto TMOS systems.Tailored adaptationsThe use of standards such as X/Openand SQL makes it possible for networkoperators to tailor their own adaptationson-line in existing application systems.(The programming tool API is not necessaryfor this purpose.)ScalabilityTMOS offers configurations that meetdifferent requirements for capacity andreliability. Resources can be adapted toboth the network size and the number ofusers.Reliability and availabilityHigh reliability requirements can be metby the use of fault-tolerant computers.FMAS also permits duplication to geographicallyseparated centres with executiveand standby operation. In thisway, operations support is protectedagainst the effects of catastrophic failures.Consistent operations support environmentThe TMOS concept, and the similaritiesbetween the various TMOS applicationsystems, enable the operating companyto handle different types of network andnetwork element in a homogenous wayThis simplifies training of staff and enablesthem to cover a wider range oftasks. The layered concept and the portabilityof TMOS application systems alsoenable the operating company to establisha consistent hardware andsoftware environment as far as networkmanagement systems are concerned,resulting in simplified purchasing proceduresand lower maintenance costs.User-friendly man-machine interfaceThe use of modern workstations for theoperator positions brings about a wholenew way of working with network managementsystems, in a manner that isefficient, logical and easy to learn. AllTMOS Application Systems offer userinterfaces based on graphics, menusand forms, resulting in high staff performance.SummaryThe Facility Management System FMASis Ericsson's response to the new andrapidly changing needs of efficient operationssupport for transport networks.FMAS, together with Ericsson's highlyflexible digital cross-connect systemsand SDH network elements, provide acompetitive state-of-the-art edge to operators'ability to maximize network utilization,and to generate revenues fromsupported leased-line services, withcontrolled quality and short lead time.Typical expanding applications to besupported are: communication betweenprivate nodes, computer-to-computercommunication, wide area networks,and video conferences.FMAS is the cornerstone of Ericsson'snew Transport Network ManagementArchitecture, focusing on operationssupport. This architecture creates newfacilities for totally integrated, cost-effectiveoperations support based on thefollowing elements:- Firstly, FMAS offers a total networkmanagement approach through itsability to support new and existingtransport network products, in cooperationwith otherTMOS orothervendors'operations support systems- Secondly, the new network elements- the digital cross-connect systemsand SDH systems (Add-Drop Multiplexers,etc) - can be effectively controlledby FMAS via a data communicationsnetwork, and via EmbeddedControl Channels (ECC) located withinthe SDH transport network- Thirdly, the Transport Network ManagementArchitecture is uniquelysupported by the openness of theTMOS/FMAS system concept; FMASmeets the current development ofTMN standards and interfaces. It isbuilt on a computing platform (CAP)on which functions/features can bedeveloped, by Ericsson or by networkoperators, allowing the system to beadapted to present and future requirements.References1. Bergendahl, J. and Ekelund.S.: TransportNetwork Development. EricssonReview 67(1990):2, pp. 54-59.2. Breuer, H.-J. and Hellstrom, B.: SynchronousTransmission Networks.Ericsson Review 67 (1990):2, pp. 60-71.3. Andersson, J.-O.: Digital Cross-ConnectSystems - a System Family forthe Transport Network. Ericsson Review67(1990):2, pp. 72-83.4. Widl, W.: Telecommunications NetworkArchitecture. Ericsson Review 67(1990):4, pp. 148-162.5. Asker, B.: Graphic User Interfaces.Ericsson Review 67(1990):3, pp. 138-146.


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