An Introduction to the Ericsson Transport Network Architecture ...

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Fig. 4 Control System Architecture CP UP ICM SNC Central Processor Unit Processor Internal Communication Network Switching Network Controller (only SDXC) Each unit in the system has a powerful microprocessor, and a central master computer co-ordinates all the unit processors and provides input/output. Unit processors enable the unit itself to perform a large amount of processing and so reduce the load on the central processor. All processors are connected to an Internal Communication Network (ICN). Depending on the size of the Network Elements, different internal communication network structures have been implemented, Fig. 4. The central processor houses the MIB, on which the OS and the local operator perform management operations. It will also implement parts of the MCF functionality, such as a network layer routing function between the Q- interface and the ECC subnetworks. The central processor can vary in size from small and inexpensive one-board microprocessor-based systems, to high-capacity redundant computers. Each of the different printed board assemblies under the control of the Central Processor contains its own Unit Processor. The Unit Processor is a building block consisting of a microprocessor, memories, communication controllers and A/D and D/A converters when required. The Unit Processors perform routine tasks on each printed board assembly, such as alarm surveillance, collection of performance parameters, and self-diagnostics. The Unit Processors also control the lower layers of the ECC protocol suite. The control system software modularity is ensured through the use of a layered structure combined with object-oriented techniques. Programs can be downloaded from an Operations System all the way down to a Unit Processor. Control of Switching Network Besides Unit Processors and the Central Processor, the control circuitry of the SDXC switch, SNC, is also connected to the Internal Communication Network. This means that all processors can set up and release cross-connections in the SDXC. This facility comes into use, for example, when rapid switching has to be performed due to a transport network fault discovered by an access unit. In this case the Unit Processor on the access unit immediately reconfigures the switch according to a predefined configuration previously communicated to the Unit Processor by the Central Processor. The Central Processor is always informed of the resulting configuration. Unit Processors Unit Processors typically occupy part of a board in the SDXC. A unit in the SDXC normally consists of only one board. A Unit Processor includes a microprocessor chip and memory. Its current implementation is a Motorola 68 302. A Unit Processor continuously performs tasks such as monitoring of hardware and calculation of bit errors, but at the same time it must react quickly to events such as incoming alarms from the transport network. The unit processor is therefore equipped with a real-time operating system kernel, OS 68, which gives response times on a microsecond level. SDXC CONTROL SYSTEM ARCHITECTURE General The SDXC control system may be composed of a central processor and up to a couple of 100 Unit Processors. It uses a packet-switched Internal Communication Network (ICN) which is integrated with the switch. Purchased hardware and software is used; the Central Processor being a UNIX computer, for example. Central processor The Central Processor is the coordinator and master of the complete control system. It continuously monitors the Internal Communication Network to find new Unit Processors. Local operators have access to the SDXC system via graphical workstations. These are connected to the Central Processor via an Ethernet Local Area Network, Fig. 5. Both the Central Processor and the operator workstations are UNIX machines based on SPARC architecture, the Central Processor being a ERICSSON REVIEW No. 3, 1992
71 Fig. 5 The CP is connected to the ICN by a separate Ethernet. All control signals are routed through a centralised, triplicated switch and embedded in the traffic signal CTU I Control Termination Unit Traffic signal Control signal Sun SPARC2 and the operator terminals Sun IPX. The Central Processor is connected to the Internal Communication Network by a separate Ethernet. It is separate to ensure that there is adequate capacity and security for communication with the Unit Processors. Ethernet, being a standardised interface, enables a change of Central Processor supplier without any interface boards having to be redesigned. The next version of the CP will consist of basic and optional plug-in units, forming a modular system connected to a highspeed VME backplane and mounted in a standard subrack suitable for telecommunication purposes. Internal Communication Network All processors are connected to the Internal Communication Network. It enables all processors to communicate with each other and with the switch control circuitry. The Internal Communication Network employs packet-switching techniques which enable processors to communicate using different data rates. The Central Processor uses 2 Mbit/s and Unit Processors 0.5 Mbit/s. The internal cabling that carries the SNI signals used for transport of traffic information within the SDXC is also used as a part of the Internal Communication Network." Thus, expansion of the SDXC with new equipment at the same time increases the capacity of the communication network to cater for new Unit Processors. Ongoing communication is not affected by this expansion. By utilising the SNI signals, the Internal Communication Network benefits from the reliable triplicated structure of the Switch. A single failure cannot cause a complete failure of the Internal Communication Network. All control signals are routed through a centralised packet switch. This is triplicated and each part resides on a switch plane, Fig. 5. The Central Processor gives or refuses permission to communicate within the Internal Communication Network and keeps a record of all ongoing communication. In fault situations, all the processors involved stop communicating and the fault is cleared by the Central Processor. Communication is normally between the Central Processor and the Unit Processors, but for time-critical operations direct communication between Unit Processors can be used, e.g. for fast protection switching. Broadcast messages can be distributed over the Internal Communication Network. In this case a message is sent from a processor and then duplicated by the communication network and sent to all access points where a processor may be connected. This facility is utilised by the Central Processor to find out whether any new Unit Processors have been connected to the Internal Communication Network. This happens, for example, when a magazine is equipped with a new interface unit. The Central Processor sends a broadcast message which is answered by all new Unit Processors. Another possibility with the ERICSSON REVIEW No. 3, 1992
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
Page 8 and 9: Control and Operation of SDH Networ
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
Page 18 and 19: 72 Fig. 6 Software Architecture CSA
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
Page 26 and 27: 80 Fig. 2 AXD 4/1, System Architect
Page 28 and 29: 82 Fig. 3 Time Space Switch structu
Page 30 and 31: 84 Fig. 4 AXD 4/1 Devices Devices o
Page 32 and 33: 86 The control signals, which come
Page 34: 88 Fig. 8 Protection Switch Unit st

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