TELECOMMUNICATION SYSTEM INCLUDING A CENTRAL BACK-UP MEMORY

Abstract: Telephone network comprised of a plurality of nodes (KNE) which are coupled to each other by means of transmission lines (TL), each node comprising a switching module (SN), a central module (CM) and at least one peripheral module (PM) and an operational maintenance control unit (OM), which can supply a command consisting of a sequence of sub-commands for changing the data in one or more nodes in the network being coupled to one of the nodes, there being coupled to one of the nodes a central back-up memory (BUD) containing a network register (NJ) for the sub-commands which are common to all the nodes of the network, local registers (UJ) for specific sub-commands for always one node, one local register being provided for each node, and also a sequence number Table (SN) from which a unique sequence numbe r can be assigned to each sub-command intended for storage either in the network register or in one of the local registers and a last relevant sequence number Table (LRSN) of the sub-command last registered for each of the node units being included, the sub-commands being stored in the relevant registers as soon as the operational maintenance command is produced by the control unit and before these sub-commands are transferred to the relevant node units.

Description: The invention relates to a telecommunication system, more specifically a telephony network, comprised of a plurality of nodes which are coupled to each other by means of transmission lines, each node comprising a switching module, a central module and at least one peripheral module to which user ports can be connected; a control unit for operational maintenance being coupled to one of the nodes which unit can supply a command consisting of a sequence of sub-commands for modifying the data in one or more nodes in the network; and a back-up memory being provided. Such a telecommunication system as a telephony network is described in Philips TELEcommunication Review, Vol 43, no.2, June 1985, pp. 92-104 and is used in, for example, company telephone exchanges. The network is then assembled from self-contained nodes each managing the variable and (semi)-permanent data of its "own" terminals connected to that node. If now one wants to make changes, by means of operational maintenance, in the data file of one or more nodes, for example because a telephone connection associated with one node is to be "moved" to a different node, whilst maintaining its own set number and all further facilities associated with that set number, such as the possibility of trunk and international calls, it is imperative that a protection is provided which ensures that during the "move", that is to say during the change in the data in the relevant nodes, no information is lost because of the fact that, for example, an interruption occurs in the transmission line between the node from which operational maintenance is to be effected and a node in which data must be changed. Such an interruption may be caused by "hardware" faults, such as faults in the equipment or a physical interruption of the transmission line. The invention has for its object to provide a solution for this problem to ensure that the data in one or more nodes can be changed in a reliable manner without an interruption during the change procedure resulting in one or more sub-commands forming part of a change command not or not incorrectly being effected. According to the invention, in a telecommunication system of the type described in the foregoing is the back-up memory therefore implemented as a central back-up memory which is coupled to one of the nodes and includes a network register for the sub-commands common to all the nodes of the network, and also local registers for the specific sub-commands for one node, one local register being provided for each node, and the sub-commands being stored in the relevant registers as soon as the control unit supplies the operational maintenance command and before the sub-commands are transferred to the relevant nodes. Acting thus, always one central memory is present in which the sub-commands are stored which either hold for all the nodes of the network or for one specific node. If now during carrying out of a command by means of a plurality of sub-commands an interruption occurs in the reception of the sub-commands by the node for which they are intended, these sub-commands can as yet be carried out at a later instant since the sub-commands intended for that node have been stored in the central back-up memory. Of course provisions must be made by means of which it is possible to determine which sub-command was received last by the node in which the disturbance occurs, and also for ascertaining which subcommands must as yet be transferred from the central back-up memory to that node. So as to provide a solution also for this problem, according to a preferred embodiment of the invention a Table of sequence numbers SN is included in the central back-up memory, from which a unique sequence number can be assigned to each sub-command intended for storage in either the network register or in one of the local registers of the back-up memory, whilst the central back-up memory also includes a last relevant sequence number LRSN Table of t he most recently registered sub-command for each of the nodes. The LRSN Table is continuously updated for each of the nodes as regards the sequence number of the last sub-commands stored in a register for the relevant unit or for the network. Thus, any hardward faults occurring during operational maintenance OM are reliably prevented from causing an OM command consisting of a sequence of sub-commands from not or not wholly being effected. The manner in which the central back-up memory in accordance with the invention can be used in a telecommunication network will now be described in greater detail by way of example with reference to the accompanying drawing. In the drawing the sole Figure is a general block circuit diagram of a telecommunication network, more specifically a telephone network of the type according to the invention, for private use. Such a network, which is described in greater detail in Philips Telecommunication Review, Vol. 43, No. 2, 1985, is generally comprised of a set of nodes KNE-1,2,3,..., n whose number is chosen optionally and which are coupled to each other by means of transmission lines allowing TDM transmission. More specifically 2 Mb/s transmission lines can, for example, be used for this purpose which can accommodate, for example, 30 PCM-channels through which mutual communication between the nodes can be effected. These nodes may be distributed over an optionally chosen geographical area, such as, for example, a company, a town, provinces, etc., depending on the needs. In this connection thoughts may, for example, go towards a larger company having several regional branches for which such a telecommunication network is available in its totality. Each node, more specifically a PABX, comprises a switching module SM, a central module CM and at least one peripheral module PM. The switching module includes a digital non-blocking switching matrix and provisions for providing clock signalling for PCM-transmission. The central module performs the control functions required for the node itself and also the communication with other nodes. A peripheral module performs preprocessing functions, for example, signalling conversions, for a group of, for example, 128 user ports. For the communication with installations which, with respect to such a relevant node, can be considered as being external, such a node may include interfaces for analogue transmission lines constituting a coupling to public telephone switching systems, for analogue coupling lines to other PBAX-systems, and for PCM-30 digital lines constituting a coupling to public networks and to networks for private usage. Each node of such a telecommunication network, three of which are shown in the Figure, is self-contained, the facilities are transparent throughout the overall network and a fully free numbering is provided. The data incorporated in the system can generally be divided into local data which are specific of a relevant node, and network data having a more general character and being the same as regards their contents for the relevant nodes. In order to ensure data-integrety for the overall network, an updating means is provided for the stock of network data stored in each node. For the sake of completeness, it should be noted that the configuration of a communication network of the type to which the invention relates, can be chosen optionally. Depending on the needs, such a configuration may be in the form of a star, a mesh or a combination thereof. By way of example let it be assumed that in the network shown in the Figure an OM-control unit is connected to KNE-1 and that a central back-up device (BUD) according to the invention is connected to KNE-2. However, the fact is stressed that both the location in which the OM-control unit is connected and the location of the central back-up device can be chosen in the network without any restrictions for each of the KNE's. At the same time, in the desc ription of the embodiment, it will be assumed that, using an operational maintenance command formed by a sequence of sub-commands, a change in the stored data must be effected in KNE-3. As the Figure shows shcematically, the back-up memory BUD includes a network register NJ and three local registers (unit-journals UJ), UJ₁, UJ₂, UJ₃ for the respective nodes KNE-1, 2 and 3. In addition, the BUD includes a Table SN of sequence numbers and a Table LRSN containing the last relevant sequence number of each of the nodes. If now by means of the OM-control unit a command intended for KNE-3 is supplied, the command consisting of a sequence of sub-commands which may relate both to changing the network data and to changing the local data, this OM command first transfers a request from KNE-1 to KNE-2 via the transmission line TL₁₂ and from KNE-2 to the BUD via the central module CM to open the SN Table. If this request is complied with, the sequence of sub-commands is thereafter transferred from KNE-1 to the BUD. To any sub-command incoming into the BUD its own sequence number is immediately assigned from the SN-Table, which number is unique in the total overall network. This number is transferred via KNE-2, TL₁2, and KNE-1 to the OM control unit and memorized there. Each SN for a sub-command is transferred to the OM control unit together with the LRSN from the LRSN Table in the BUD, the LRSN being associated with the node for which the sub-command is intended. After each sub-command received, the LRSN for the relevant node, or for all the units in the case in which the command is intended for the entire network, is updated. For each SN received by the OM control unit the simultaneously received LRSN is also memorized. Thus, the OM control unit knows the SN and LRSN for each sub-command, after the entire sequence of sub-commands have been transferred to the BUD. After the entire sequence of sub-commands have been transferred from the OM control unit to the BUD, the OM control unit instructs the BUD to close the SN Table. Thereafter the sub-command can be transferred to KNE-3 for changing data in this node by means of those sub-commands. When each sub-command is transferred to the KNE-3 the associated SN and LRSN are simultaneously transferred with this sub-command. Before KNE-3 executes the sub-command, the unit first checks whether the sequence number SN of the last sequence number LSN received by KNE-3, this LSN being memorized in a memory associated with the central module, is equal to the LRSN received together with the new sub-command. If LSN = LRSN this implies that for KNE-3 no sub-commands have got lost, so that this sub-command can be executed. After execution of the sub-commands the LSN is replaced in the memory of the central module of KNE-3 by the SN of the sub-command just executed. If LSN ≠ LRSN, KNE-3 refuses to execute the sub-command and of course does then not change the LSN stored in the memory of the central module, as obviously the connection LT₁₃ between KNE-1 and KNE-3 or KNE-3 itself has been non-operational during some time. KNE-3 now sends a request to the BUD for sending from NL and/or UJ3 all the sub-commands having a SN higher than the LSN. In reply to this request the BUD sends to KNE-3 all the sub-commands having a SN > LSN from the register for KNE-3 (UJ3) and possibly from the network register (NJ), the sub-commands being sent in a sequence of increasing sequence numbers. In this way all the sub-commands are indeed received in the appropriate sequence by KNE-3 for execution, so that there is no risk of inconsistency in the data file of the network.

Claims: A telecommunication system, more specifically a telephony network, comprised of a plurality of nodes which are coupled to each other by means of transmission lines, each node comprising a switching module, a central module and at least one peripheral module to which user ports can be connected; a control unit for operational maintenance being coupled to one of the nodes, which unit can supply a command consisting of a sequence of sub-commands for changing the data in one or more nodes in the network; and a back-up memory being provided, characterised in that the back-up memory is implemented as a central back-up memory which is coupled to one of the nodes and includes a network register for the sub-commands common to all the nodes of the network, and also local registers for specific sub-commands for one node, one local register being provided for each node, and the sub-commands being stored in the relevant registers as soon as the control unit supplies the operational maintenance command and before the sub-commands are transferred to the relevant nodes. A telecommunication system as claimed in Claim 1, characterized in that the central back-up memory includes a sequence number Table from which a unique sequence number can be assigned to each sub-command intended for storage either in the network register or in one of the local registers of the back-up memory, and that the central back-up memory also includes a last relevant sequence number Table of the sub-command last registered for each of the nodes. A telecommunication system as claimed in Claim 2, characterized in that each node includes a memory in which the sequence number of the sub-command performed last by that unit is stored. A telecommunication system as claimed in Claims 2 and 3, characterized in that each sub-command is transferred together with the associated sequence number and the last relevant sequence number of the node for which the sub-command is intended to that node and that each node includes comparator members which each time a sub-command is received check whether the last sequence number stored in the node is equal to the relevant sequence number received last for that node. A telecommunication system as claimed in Claim 4, characterized in that the sub-command is executed by a node unit when the last sequence number of that unit is equal to the last relevant sequence number received together with the sub-command and that thereafter the sequence number of the executed sub-command is stored in the unit as the last sequence number. A telecommunication system as claimed in Claim 4, characterized in that the sub-command is refused by a node unit when the last sequence number of that unit is not equal to the last relevant sequence number and that means are provided for transferring from the central back-up memory, all the commands having a sequence number exceeding the last sequence number stored in that unit, to the network register and/or the local register for the relevant unit to that unit. A telecommunication system as claimed in at least one of the preceding Claims, characterized in that the control unit for operational maintenance and the central back-up register within the network can optionally be connected to any of the node units.

Inventors: WESTERHOF, RUDOLPHUS HENRICUS WILHELMUS MARIA, WILLEMSTEIN, RUUD ALBERT SOPHIA
Applicants: N.V. PHILIPS' GLOEILAMPENFABRIEKEN
Application year: 1987
Main classification: H04Q3
IPC codes: H04M3, H04Q3, H04M11, G06F11