An Introduction to the Ericsson Transport Network Architecture ...

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72 Fig. 6 Software Architecture CSA CSP Control System Application Control System Platform broadcast facility is for the Central Processor to distribute calendar date and time to all Unit Processors simultaneously. The use of broadcast greatly reduces the load on the Central Processor, since the single message sent by the Central Processor is multiplied and distributed by the packet-switched nodes within the Internal Communication Network. A set of rules defines the way communication between the application programs in the Central Processor and the Unit Processors is accomplished. The rules specify the size of packages, priority handling between different messages, actions to be taken when messages or parts of messages are lost, etc. All these rules are designed into four protocol layers. Together these four layers hide all Internal Communication Network implementation details from the application. The protocols are implemented as separate software modules, and one layer can therefore be modified without affecting the others. The same protocol software is used both in the Unit Processors and in the Central Processor. It is written in the C programming language. Software Architecture General By definition, all software in the SDXC belongs to the Control System. Its purpose is to provide Operation, Administration, Maintenance and Provisioning functions via the external control interfaces, namely the Graphical User Interface and the Q-interface. The software is physically distributed between the Central Processor and the Unit Processors. There is a basic architectural distinction between platform-oriented and application-oriented software (referred to in Fig. 6 as CSP and CSA respectively). Control System Platform The Control System Platform (CSP), together with the computer hardware and its Operating System - currently UNIX SVR4.1.2 - provides a platform that offers the following services: - Internal Communication IPC, i.e. Inter-Process Communication (inter- as well as intra-processor) by way of 'sockets' - External Communication Provision of Application Programmer's Interface (API) for communication with external management applications. These services use open, standardised, 7-layer OSI stacks - Inventory Services for checking consistency between software and hardware configuration - Program loading Services for loading of software packages from the local sites as well as from the centralised network management system (FMAS) - Process handling Functions to enable supervision of processes - Run-time fault reporting Functions to enable the reporting of internal DXC Control System faults to a management system - Restart Upon the detection of a Control System fault, the nature and seriousness of the fault are evaluated and the system is subsequently restarted from a well defined point of execution. Fig. 7 The CSA Architecture, with its layered structure Control System Application The DXC CS application software constitutes all Transport Network oriented functionality. For a static description of the ERICSSON REVIEW No. 3, 1992
73 CSA, three aspects of the functionality are taken into account, thereby creating a layered structure, in order to isolate different dependencies and stimulate a modular design, Fig. 7. - The User Layer contains the functionality of the Graphical User Interface. This layer of software will develop and change considerably due to different market needs and new tools for graphical presentation. It is therefore separated from the underlying software by an interface called the Controller Interface (CI) which can be said to represent the functionality provided by the TMN Layer and offered to management systems, such as centralised OS or local GUI - The TMN Layer consists of functions for managing Network Elements specified in an objectoriented Information Model. An Information Model is becoming the standard way of specifying the manageable resources of a Network Element in the Transport Network. CCITT Recommendation G.774 describes the basis for the SDH NE Information Model, and thus forms the foundation for the DXC CS Telecommunication Management Layer (TMN). It will necessarily develop over the years, particularly since different customers will require their SDH NE deployment in stages not coherent with CCITT Recommendation G.774 releases. For the purpose of isolating these dependencies, the Information Model aspects are singled out in the TMN Layer - The System Layer For SDH NEs, CCITT Recommendations G.781-G.783 specify-through the use of Functional Block descriptions - the functionality that must be provided. The descriptions are a reasonably stable set of requirements and are singled out in the DXC CS in the System Layer so as to be distinguished from the management aspects. The object-oriented approach is used here too, i.e. the System Layer consists of a number of objects. The software described above is mapped onto the computer platform as shown in Fig. 8. From an application programmer's point of view, the Q-interface and the F-interface are handled in a similar way. The protocols are specified in the Controller Interface. OSI standards for service specifications (CMISE) are utilised. The Q-interface is a full 7-layer OSI stack, while the F-interface uses the IPC mechanism provided by the Control System Platform. Fig. 8 Mapping of the CSA software onto the computer platform
Page 1: ERICSSON REVIEW 3 1992 An Introduct
Page 4 and 5: An Introduction to the Ericsson Tra
Page 6 and 7: 60 Fig. 3 AXD 155 system integratio
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Page 10 and 11: 64 These functions and a number of
Page 12 and 13: 66 to the OS upon detection of a se
Page 14 and 15: 68 BOX 3 The SDH NE MANAGEMENT ORGA
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Page 20 and 21: 74 Functional requirements Certain
Page 22 and 23: 76 Fig 10 SMUX Control System Hardw
Page 24 and 25: AXD 4/1, a Digital Cross-Connect Sy
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Page 28 and 29: 82 Fig. 3 Time Space Switch structu
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Page 32 and 33: 86 The control signals, which come
Page 34: 88 Fig. 8 Protection Switch Unit st

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