FR2870417A1 - Telecommunication terminal for digital integrated services network, has processor with software to detect identifier of each telephonic terminal, where terminal transmits message over network by utilizing identifier - Google Patents

Abstract

The terminal has a digital integrated services network (RNIS) processor (14) with a set of software layers implementing a communication protocol e.g. LAP-D protocol, for managing data route in a RNIS network. The processor has software to detect an identifier (TEI) of each of telephonic terminals (T1- Tn) in line. Each terminal transmits a message in the network by utilizing the identifier.

Description

Telecommunication terminal for integrated network of

  The invention relates to integrated services digital networks (ISDN) and more particularly relates to a telecommunication terminal for such an ISDN network.

  According to a particularly advantageous application of the invention, such a terminal is intended to constitute a priority terminal from which an emergency call can be issued for, for example, transmitting alarm signals (intrusion detection, detection). fire, ...) or establish communication with emergency services.

  As is known, a telephone terminal and, in general, a telecommunications terminal, can establish a communication only if the line is free. If the line is busy, the terminal must wait for the line to clear before it can in turn establish a telephone call.

  In some cases, however, it may be necessary to be able to establish a call even if the line is busy. This is particularly the case when a call must be sent from a priority terminal in order, for example, to call emergency services (police, fire, EMS, ...). When the priority terminal is connected to an analog line of a telecommunication network, such a service is relatively easy to implement. It is advisable, in fact, to position the priority terminal in a break on the analog line, the other stations of the line being placed downstream, that is to say opposite to the telephone network to which the subscriber line is connected. FIG. 1 schematically shows a telephone installation of a subscriber in which an analog priority terminal 10 is connected to an analog telephone line L of the subscriber to which are connected a set of telephone sets P. As as seen in this figure, the line L is connected to the PSTN switched telephone network via a CAA routing autonomy switch. The priority terminal 10 is connected to the line L upstream, that is to say the side of the concentrator CAA, the other positions P being placed on the downstream segment S of the line. The terminal 10 is provided with a relay 12 which, when the line L is occupied, makes it possible to cut the downstream segment S, the upstream segment S 'of the line L, which extends between the terminal 10 and the CAA concentrator. then becoming available only for the priority terminal 10.

  Such an architecture, which is effective for establishing a communication from a priority terminal on an analog line, can not be applied on a digital line of an ISDN network because, in this case, the bus break to which are connected the terminals would have an impact on the subscriber card located at the CAA peering switch and could block this card, which would then require a complete reset of the card. Such a reset has impacts on all subscribers connected on this card. In particular, all communications in progress are cut off, even those that were urgent or priority.

  The object of the invention is therefore to overcome this disadvantage and to provide a telecommunications terminal for establishing priority calls on a busy line of an ISDN network.

  The subject of the invention is therefore a telecommunications terminal for an ISDN service integration network, comprising power supply means, an ISDN processor comprising means for implementing telecommunication protocols of the ISDN network to manage the routing of data in the ISDN network. network, characterized in that it comprises means for detecting an identifier (TEI) of each ISDN telecommunication terminal of the network, in line and means for transmitting a message in said network using the identifier of one of the terminals online.

  According to another characteristic of the invention, the means for detecting the identifier of each on-line terminal comprise frame analysis means conveyed on the network and means for extracting the identifier of said frames.

  According to yet another characteristic of the invention, the analysis means are adapted to analyze the supervision frames conveyed on the network, in particular the supervisory RR frames exchanged between the on-line terminal and the ISDN network.

  In one embodiment of the invention, the means for detecting the identifier of each on-line terminal and the means for transmitting messages using said identifier can be implemented in a software layer of the ISDN processor implementing the protocol. LAP-D.

  According to the invention, the means for transmitting a message in said network comprise means for transmitting a level 2 acknowledgment frame (UA) used to indicate that the terminal accepts the establishment or the release of a data link. , said frame containing the identifier of the online terminal.

  Finally, according to yet another characteristic of the invention, the terminal comprises means for deleting the TEI identifier from the on-line terminal, after receiving suppression frames of said TEI identifier received from the ISDN network.

  Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of non-limiting example, and with reference to the appended drawings in which: FIG. 1, of which it has already been mention is made, schematically illustrates a portion of the telephone network in which a priority terminal is connected in break on an analog line of a subscriber; FIG. 2 is a diagram illustrating the connection of a priority ISDN terminal to an SO bus of an ISDN network, in accordance with the invention; FIG. 3 is a block diagram of a priority terminal; and FIG. 4 is a diagram illustrating a flow of data exchanged between the priority terminal and the concentrator with autonomous routing of the ISDN network during the implementation of the invention.

  With reference to FIG. 1, the basic access of the ISDN network is a bus known as bus SO on which all the terminals Ti, T2, T3,..., Tn of the installation are connected in parallel by via Pl, P3, ... Pn taken as SO.

  The bus SO is connected to a digital termination of the TNR network via an SO interface. This TNR termination is connected via a U interface to the CAA routing time switch associated with the PSTN switched telephone network. Note that the notions of SO bus, CAA routing autonomy switch, digital TNR network termination, SO interface and U interface are concepts well known to those skilled in the ISDN and ISDN networks. will not be described in detail later.

  Furthermore, the architecture shown in Figure 2 is only an example of installation, the invention also applies to any type of ISDN installation depending on the elements that compose it. Thus, other architectures of ISDN installations can also be envisaged without departing from the scope of the invention, for example by providing PABX switches on the bus SO and providing, in this case, appropriate interfaces, or by connecting the switch with routing autonomy to a transit switch and / or another CAA switch.

  As is known, an ISDN network provides an interface for a user to access different networks to optimize a required data transport. It implements basic access including two B-channels supporting rates of 64 kbits per second and a D-channel that transmits at a rate of 16 kbits per second in basic access. While B-channels are primarily used to convey content data such as voice, D-channel supports signaling information relating to calls, connection establishments, service requests, data routing on B-channels and finally connection release information.

  It will also be noted that, in ISDN networks, each terminal T1, T2, T3, ... Tn has an identifier TE1, TE2, ..., TEIn. Each identifier constitutes an address for identifying a terminal online or from which a call is issued. This address information is constituted by a terminal end-point identifier (TEI) field contained in the frames carried on the ISDN network. In particular, the TEI fields are contained in the Receive Ready frames which are used by each terminal to indicate that it is ready to receive a frame or to acknowledge previously received frames.

  The installation shown in FIG. 2 is used to enable the establishment of a call from a priority ISDN terminal, namely the terminal designated by the reference numeral Ti when one or more of the other user terminals are online.

  To do this, the priority terminal Ti is adapted to force the network to release one or more resources, namely a channel B, when the bus SO is busy, to enable it to establish a priority call.

  The priority terminal Ti consists essentially of an ISDN processor 14 which communicates, via a connection interface 16 with the bus SO. Another processor 18 constituting an optional central processor of the terminal Ti may also be provided for the implementation of particular applications related to telephony, such as messaging services, etc.

  In order to be compatible with the ISDN network, which makes it possible to access different telecommunication networks, the ISDN processor 14 comprises a set of software layers each implementing a communication protocol, such as the LAP-D, LAP-LAP protocols. B, D, X25, X21, ...

  Finally, a power source 20 supplies the main components of the terminal Ti.

  In order to cause a release of the resources of the network to enable the establishment of a communication from the terminal Ti, this terminal uses the possibilities offered by the LAP-D protocol intended to convey information on the channel D. In particular, the terminal incorporates all the hardware and software means for detecting the identifier of each terminal online by analyzing the frames conveyed on the network. Thus, the ISDN processor is duly programmed to scan the frames conveyed on the bus SO, in particular the supervisory RR frames in order to detect the TEI identifier of the or each on-line terminal and to use this identifier to transmit AU frames. to cause a conflict of identifiers. The CAA switch comprises all the hardware and software means to cause a cut of the line when such a conflict is detected.

  FIG. 4 shows an exemplary embodiment of the invention according to which the two B channels of the bus SO are occupied by two telephone or data communications established from the telephone terminals T2 and T3 and according to which it is desired establish an emergency call from the priority terminal Ti. In this figure 4, the arrows represent steps of the procedure for establishing the priority call.

  As is known in the event of unavailability of network resources for establishing a call from the terminal T1, any establishment request message sent from the terminal Ti sent in the ISDN D-channel (level 3) will be rejected by the network (step 22) in the form of a message called end release issued by the CAA concentrator by specifying the cause, that is to say signaling that no circuit or channel is available to establish this communication. The priority terminal T1 then analyzes the supervisory RR frames that travel on the bus SO in order to know the TEI address of the terminal or terminals in communication. As is known, these RR frames are exchanged between the network and the terminals every 10 seconds for the duration of the communication (s).

  As soon as the priority terminal Ti has located one or more communication terminals, and has extracted the TEI identifier of the incriminated terminal (s), it sends, in the following step 24, an AU (Unnumbered Acknowledgment) frame using the identifier of one of the active terminals on the bus SO. Such a UA frame corresponds to a level 2 acknowledgment frame sent generally to indicate that the terminal accepts the establishment or release of a data link. This UA frame is normally sent in response to an unnumbered control frame received from the CAA concentrator. However, no level 2 command having been previously issued by the CAA concentrator, this UA frame received by the concentrator is then considered as a non-solicited frame, that is to say, sent spontaneously. After receiving this frame, the CAA concentrator transmits a TEI address verification frame (step 26). This phase consists in asking the terminal having the identifier conveyed by the frame UA to confirm its identifier. In response to this request, the hub receives, in the next step 28, two responses from one of the terminal T3 whose address corresponds to that taken by the priority terminal and the other from the priority terminal. When the network receives these two responses for the same TEI identifier, it considers that there is a TEI identifier conflict on the SO bus and removes this network identifier by transmission in the network, by the CAA concentrator, of a network. deletion frame of the borrowed TEI identifier. The priority terminal then deletes the borrowed TEI identifier, and takes over its own TEI for all future exchanges. At the expiration of a predetermined period of time, for example of the order of a few seconds, the resource of the channel B supporting the communication is released in the network.

  In the next step 30, the priority terminal renews its call a few seconds later, for example 10 seconds later, by sending an establishment message using its own identifier TEI1. This call is normally accepted by the CAA switch because at least one B-channel has been released following the deletion of one of the active TEIs on the bus. In the case where the network rejects this call, the priority terminal renews the resource release procedure by issuing a new UA frame. If no terminal is in communication, that is to say in the absence of supervision RR frame, the priority terminal renews the call, for example periodically, for example every 10 seconds.

  As is conceivable, the invention, according to which the priority terminal uses the address of one or more terminals online to develop unsolicited frames to generate a conflict of identifiers and thus cause a deletion of the identifier concerned makes it possible to cut off a communication previously established without affecting the integrity of the bus to which the terminals are connected and thus avoids any dysfunction within the network.

Claims (6)

  A telecommunication terminal for an ISDN ISDN comprising power supply means (20), an ISDN processor (14) having means for implementing ISDN network telecommunication protocols to manage the routing of data in the ISDN network. network, characterized in that it comprises means for detecting an identifier (TEI) of each ISDN telecommunication terminal of the network, in line and means for transmitting a message in said network using the identifier of one of the terminals online.   2. Terminal according to claim 1, characterized in that the means for detecting the identifier of each terminal in line comprise frame analysis means conveyed on the network and means for extracting the identifier of said frames.   3. Terminal according to claim 2, characterized in that the analysis means are adapted to analyze the supervision frames conveyed over the network, in particular the supervision frames (RR) exchanged between the on-line terminal and the ISDN network.   4. Terminal according to any one of the preceding claims, characterized in that the means for detecting the identifier of each terminal in line and the means for transmitting messages using said identifier are located in a software layer of the ISDN processor (14). ) implementing the LAP-D protocol.   Terminal according to any one of claims 1 to 4, characterized in that the means for transmitting a message in said network comprise means for transmitting a level 2 acknowledgment frame (UA) used to indicate that the terminal accepts the establishment or release of a data link, said frame containing the identifier of the online terminal.   6. Terminal according to any one of claims 1 to 5, characterized in that it comprises means for deleting the TEI identifier of the on-line terminal, after receiving suppression frames of said TEI identifier received from the ISDN network.