Abstract:
A gateway apparatus comprising signal converter has service line concentrating unit and protection line concentrating unit, packet switch has a plurality of IP converters each line-concentrated to service line concentrating unit and protection line concentrating unit, first monitor monitoring responses from the plurality of IP converters through service line concentrating unit and protection line concentrating unit, second monitor monitoring responses from the plurality of IP converters through paths deferring from those of first monitor, failure determiner determining presence or absence of failures in at least any one of service line concentrating unit, protection line concentrating unit and the plurality of IP converters on basis of presences or absences of responses monitored by first and second monitors, respectively, and switcher switching protection line concentrating unit to be in effect to operate it as new service system when failure determiner has determined that any failure is present in service line concentrating unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-291412, filed Oct. 4, 2005, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a gateway apparatus connecting, for instance, a public switched telephone network (PSTN) and an Internet protocol (IP) network with each other. 
   2. Description of the Related Art 
   In recent years, information communication services including voices and data communications have been diversified with the increase in information communication needs and the development of communication liberalization. Such background has increased carriers who newly entered a communication service field in number and has made service competitions among carriers active. New carriers are call new comer carriers (NCCs) and provide a variety of services by using a technique such as a voice over Internet protocol (VoIP). The VoIP is a technique which packetizes digital vice data to transmit it so as to integrate a voice system network and a data system network. 
   Many NCCs take facilities such as exchanges on lease at predetermined charges from a specified carrier already having subscriber&#39;s lines. The NCCs mostly construct their own exchange networks, for instance, IP networks on their own accounts. Besides these constructions, communication systems are formed by also adding a public switched telephone network of the specified carrier. For proving services to ordinary users, the communication system utilizes such facilities multiply. 
   To connect different communication networks like the PSTN and the IP network with each other, the gateway apparatus is utilized. Such apparatus comprises an IP conversion unit converting voice data and binary data into IP packets; and a packet switch unit switching the IP packets. Each of these units functions a role as a network interface to the IP network. Jpn. Pat. Appln. KOKAI Publication No. 2000-174748 discloses a technique as a countermeasure against a failure in this interface unit. 
   By the way, in such an existing apparatus of this kind, a control unit monitors a status of a line concentrating interface connected to the IP conversion unit through a control interface. Then, the existing apparatus detects the failure in the line concentrating interface in the network interface. Therefore, if any abnormality occurs in the IP conversion unit itself, the existing apparatus cannot monitor the status of the line concentrating interface. 
   Between the line concentrating interface and the IP conversion unit, the existing apparatus can only determine that the line concentrating interface is abnormal on the grounds that all lines of set number in a service system are abnormal. Accordingly, even if the line concentrating interface are brought into protection, the existing apparatus cannot execute switching from service system to a protection system until all lines of set number in a service system become abnormal. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is invented in accordance with the above-mentioned situations and an object of the invention is to provide a gateway apparatus improving redundancy and fault-tolerance performance and a method of protection switching of the apparatus. 
   According to an aspect of the present invention, there is provided a gateway apparatus converting communication protocols among a subscriber&#39;s network, a public switched telephone network (PSTN) and a packet communication network with one another to achieve mutual communications among these networks, comprising: a subscriber&#39;s network interface terminating the PSTN to generate in-apparatus signals; a PSTN interface terminating the PSTN to generate the in-apparatus signals; a signal conversion unit packetizing the in-apparatus signals output to the packet communication network; and a packet switch path-controlling packet signals output from the signal conversion unit to transmit them to a destination in the packet communication network, wherein the signal conversion unit has a service system line concentrating unit and a protection system line concentrating unit; and the packet switch has a plurality of Internet protocol (IP) conversion units each line-concentrated to the service system line concentrating unit and the protection system line concentrating unit, the apparatus further comprising: a first monitor unit monitoring responses from the plurality of the IP conversion units through the service system line concentrating unit and the protection system line concentrating unit; a second monitor unit monitoring the responses from the plurality of the IP conversion units through paths deferring from those of the first monitor unit; a failure determining unit determining the presence or absence of failures in at least any one of the service system line concentrating unit, the protection system line concentrating unit and the plurality of the IP conversion units on the basis of the presences or absences of the responses monitored by the first and the second monitor units, respectively; and a switching unit switching the protection system line concentrating unit to be in effect to operate it as a new service system when the failure determining unit has determined that any failure is present in the service system line concentrating unit. 
   With such measures taken, it becomes possible to detect failures on individual ports of an IP conversion unit  14  and it becomes possible to shorten failure time and prevent performance deterioration of a system as well as perform a failure recovery. 
   According to the present invention, the gateway apparatus with improved redundancy and fault-tolerance performance and the method of protection switching of the apparatus can be provided. 
   Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
       FIG. 1  is an exemplary system view showing an embodiment of a communication system regarding the present invention; 
       FIG. 2  is an exemplary system block diagram showing an existing voice communication system; 
       FIG. 3  is an exemplary functional block diagram showing an embodiment of a gateway apparatus  1  in  FIG. 1 ; 
       FIG. 4  is an exemplary block diagram showing a protection configuration of a control unit  16  and a packet switch  15  in  FIG. 3 ; 
       FIG. 5  is an exemplary signal schematic view of a packet switch  15  and an IP conversion unit  14 ; 
       FIG. 6  is an exemplary functional block diagram showing a control unit  16   a  in  FIG. 5 ; 
       FIG. 7  is an exemplary flowchart showing operations of a gateway apparatus in an embodiment of the present invention; 
       FIG. 8  is an exemplary view showing an example of configuration information on the IP conversion unit  14  in the control unit  16 ; and 
       FIG. 9  is an exemplary view showing a threshold (m) setting table for switching over a line concentrating interface in detecting a failure in the line concentrating interface. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a system view illustrating an embodiment of a communication system regarding the present invention. In  FIG. 1 , a gateway apparatus  1  firstly houses a plurality of subscriber&#39;s lines  114  on a subscriber&#39;s network SN. The gateway apparatus  1  is connected to an IP network DN. IP network DN is a packet communication network and formed as a unique network, etc., of an NCC. The gateway apparatus  1  may also be connected to the Internet as the IP network DN. 
   The subscriber&#39;s network SN includes a subscriber&#39;s terminals  5 , base stations CS 1 s of a mobile phone system, radio terminals PS 1 s, and the like. The subscriber&#39;s terminals  5  and the base stations CS 1  are connected to the gateway apparatus  1  via the subscriber&#39;s lines  114 . The subscriber&#39;s lines  114  are access lines assigned to each of a plurality of subscriber&#39;s terminals  5  and to each of the radio terminals PS 1 . 
   The gateway apparatus  1  transmits signals (digital data signals such as voice data, and video and image data), generated from the subscriber&#39;s network SN, to the IP network DN. The gateway apparatus  1  transmits signals destined to terminals in the subscriber&#39;s network SN from the IP network DN to the subscriber&#39;s network SN to make incoming calls to the corresponding terminals. Thereby, interactive communication paths among the subscriber&#39;s terminal  7  belonging to the IP network DN, subscriber&#39;s terminals  5  and the radio terminals PS 1 s may be set arbitrarily. Further, in the system shown in  FIG. 1 , the IP network DN is provided with network monitoring equipment ME. The monitoring equipment ME communicates a variety of items of information to and from the gateway apparatus  1  via the IP network DN and mainly manages an operation status of the gateway apparatus  1 . 
     FIG. 2  is a system block diagram showing an existing voice communication system. In  FIG. 2 , an exchange  3  of a PSTN XN houses the subscriber&#39;s terminals  5  of the subscriber&#39;s network SN via the subscriber&#39;s lines  114 . The exchange  3  is a facility belonging to the PSTN XN. In combining the system shown in  FIG. 1  and the system shown in  FIG. 2 , the gateway apparatus  1  is disposed closer to the subscriber&#39;s terminals  5  than the exchange  3 . Therefore, the inter-line connecting point between the subscriber&#39;s network SN and the PSTN XN becomes the connecting point between the gateway apparatus  1  and the exchange  3 . That is, the gateway apparatus  1  is arranged closer to the subscriber&#39;s network SN than the inter-line connecting point between the subscriber&#39;s network SN and the line exchange network XN. Communication protocols among the subscriber&#39;s network SN, the PSTN XN and the IP network DN are different from one another. 
     FIG. 3  is a functional block diagram illustrating an embodiment of the gateway apparatus  1  shown in  FIG. 1 . In  FIG. 3 , the gateway apparatus  1  comprises a control unit  16 , a subscriber&#39;s line interface  11 , a public network interface  12  and a control interface (I/F) unit  17 . 
   The subscriber&#39;s line interface  11  conducts interface control for the subscriber&#39;s lines  114  and the public line interface  12  conducts interface control for public lines  115 . In other words, the subscriber&#39;s line interface  11  houses subscriber&#39;s terminals and the radio base station via the subscriber&#39;s lines  114  to provide an exchange station side interface for an integrated service digital network (ISDN). The public network interface  12  is connected to the public line  115  to provide a terminal side interface for the ISDN. Communication quantities of the public lines  115  are pre-designed on the basis of a demand forecast of traffic. 
   Further, the gateway apparatus  1  in  FIG. 3  has an IP conversion unit  14  and a packet switch  15 . The IP conversion unit  14  is disposed between the control unit  16  and the IP network DN to perform a protocol conversion between networks. Namely, the IP conversion unit  14  converts time division multiple signals supplied via another communication network (such as PSTN XN) into IP packets to input them to the packet switch  15 . The IP packets are routed in accordance with destination IP addresses to be transmitted to the IP network DN through a local area network (LAN) cable  117 . The IP conversion unit  14  converts the IP packets input from the IP network DN through the LAN cable  117  and the packet switch  15  into the time division multiple signals. The control unit  16  communicates a variety of pieces of information with the IP conversion unit  14  through a control interface unit  17 . The packet switch  15  is connected to the control unit  16  via an external LAN  18 . 
   In  FIG. 3 , the number of housed lines of the subscriber&#39;s lines  114  to be housed in the subscriber&#39;s line interface  11  is made equal to that of the public lines  115  to be housed in the public network interface  12 , namely, the traffic. On the contrary, the number of housed lines of the subscriber&#39;s lines  114  to be housed in the subscriber&#39;s line interface  11  is made larger than that of the public lines  115  to be housed in the public network interface  12 . Such configuration is advantageous to design the communication system. 
   The control unit  16  controls the whole of the gateway apparatus  1 . That is to say, the control unit  16  requires control for the subscriber&#39;s lines  114  and the public lines  115  of the subscriber&#39;s line interface  11  and of the public network interface  12 . Moreover, the control unit  16  comprehensively manages the failures detected by the subscriber&#39;s line interface  11  and by the public network interface  12 . 
   The control unit  16  of the gateway apparatus  1  is connected to the network monitoring equipment ME via the IP network DN. The monitoring equipment ME communicates with the control unit  16  to displays the information, being comprehensively managed, on the side of the monitoring equipment ME then it may monitor and mange the gateway apparatus  1  remotely. Further, the monitoring equipment ME has a threshold setting unit  20 . The setting unit  20  is used for inputting a threshold related to failure detection. 
   In  FIG. 3 , the control unit  16  is connected to the IP network DN through the IP conversion unit  14  and the packet switch  15 . Every subscriber&#39;s line interface  11  and  12  and control unit  16  has a dedicated central processing unit (CPU) and a memory (not shown) and operates through each computing processing of each of the CPUs on the basis of programs stored each memory. 
     FIG. 4  is a block diagram showing protection (redundancy) configurations of the control unit  16  and the packet switch  15  in  FIG. 3 . The packet switch  15  is constituted of a double structure of a service system line concentrating interface unit  151  and a protection system line concentrating interface unit  152 . The control unit  16  has a control unit  16   a . The line concentrating interface units  151  and  152  notify status signals indicating their own driving statuses to the control unit  16   a  in response to poling requests, etc, respectively. The control unit  16   a  recognizes the driving status of the packet switch  15  to supply a control signal based on the recognition result to a relay control circuit  159 . The relay control circuit  159  outputs relay control signals to control switching of a plurality of relays (mentioned later) disposed in the packet switch  15  on the basis of the driving statuses of the line concentrating interface units  151  and  152 . 
     FIG. 5  is a signal schematic view of the packet switch  15  and a plurality of conversion units  14 . In  FIG. 5 , the packet switch  15  is connected to the IP network DN through an active port and a stand-by port. The active and the stand-by ports are connected to the line concentrating interface units  151  and  152  through a switch unit  23 . On the other hand, the control unit  16   a  is connected to the line concentrating interface units  151  and  152  through an external LAN  18  and a switch unit  21 . Furthermore, the line concentrating interface units  151  and  152  are connected to the plurality of the IP conversion units  14  through a switch unit  22 . The IP conversion units  14  consist of a plurality of substrates possible to be inserted/extracted. 
   Each switch unit  21 ,  22  and  23  is, for instance, a relay and switch-controlled by control from a relay control circuit  159 . The control unit  16   a  is connected to the plurality of the IP conversion units  14  from a service system control interface unit  17  through an internal LAN  19 . 
   The plurality of the IP conversion units  14  in  FIG. 5  are provided with status detection points via the external LAN  18  or the internal LAN  19 . Out of them, detection points detecting statuses of the line concentrating interfaces  151  and  152  of the LAN switch, etc., via the external LAN  18  are set to A, and detection points detecting the statuses of the IP conversion units  14  through the internal control communication (internal LAN  19 ) or registers with the statuses stored therein are set to B. To distinguish the plurality of the IP conversion units  14 , suffixes (1-n) are provided for the A and B. Each of the IP conversion unit  14  is connected to the switch unit  22  to switch over the connecting routes in accordance with the control from the relay control circuit  159 . 
     FIG. 6  is a functional block view showing the control unit  16   a . The control unit  16  integrally executes a variety of kinds of control regarding the operations of the gateway apparatus  1  through the processing of the control processor CPU  161  on the basis of control programs stored in a ROM  162  and a RAM  163 . Specifically, the control unit  16  controls a connecting status of a communication path at a time division time switch (not shown) on the basis of the communication quantity of time division multi path connecting between the public network interface  12  and the time switch and of the communication quantity of the public line  115 . 
   A clock control unit  165  selects an arbitrary subscriber&#39;s line as a clock master from the public network interface  12 . The selected clock master is connected to the clock control unit  165  via a clock supply line to supply the master clock to the clock control unit  165 . The clock control unit  165  generates inner clocks synchronizing with a network clock from the master clock. The inner clocks are distributed and supplied to each part of the gateway apparatus  1  through a clock distribution lines. Thereby, the gateway apparatus  1  operates in synchronization with the network clock. 
   In addition, the control unit  16   a  includes an internal LAN interface unit  167  to be connected to the internal LAN  19  and an external LAN interface unit  168  to be connected to the external LAN  18 . These units are controlled by a network interface control unit  166 . 
   In the configuration of  FIG. 5 , the control unit  16   a  outputs monitoring signals to each IP conversion unit  14  through the line concentrating interface unit  151  via the external LAN  18 . Getting responses form the IP conversion units  14 , the control unit  16   a  can determine that the lines of the corresponding to the line concentrating interface unit  151  are normal. If the lines are abnormal, the control unit  16   a  monitors the statuses of the IP conversion units  14  via the control unit interface unit  17 . If the statuses of the IP conversion units  14  are normal, the control unit  16   a  determines that the interface unit  151  is abnormal, and on the contrary, if they are abnormal, it determines that the IP conversion units  14  are abnormal. When determining the occurrence of the abnormality in the active system line concentrating interface unit  151 , the control unit  16   a  executes the protection switching to switch over from the active system line concentrating interface unit  151  to the protection system line concentrating interface unit  152 . 
     FIG. 7  is a flowchart illustrating operations of the gateway apparatus in the embodiment. In  FIG. 7 , the gateway apparatus firstly sets a determination reference of the protection switching. That is, in starting up the system, the threshold setting unit  20  of the operation management equipment ME sets to perform the protection switching when the threshold of the protection switching of the line concentrating interface units  151  is set to (m) and when failures of (m) ports (m≦n) are detected (step S 1 ). This setting is possible to be changed from the management equipment ME as needed also after starting up the system. 
   The number (x) of failures at the monitoring points A 1 -An of the plurality of the IP conversion units  14  are then monitored as needed via the external LAN  18 , and if x&lt;m, usual operations are continued without switching the protection (redundancy) (step S 3 ). If x≧m, the presences/absences of the failures at the monitoring points B 1 -Bn of the plurality of the IP conversion units  14  are monitored through the internal LAN  19  (step S 4 ). If there is no failure at the monitoring points B 1 -Bn, an effective system of the interface unit  151  is switched. Namely, if the service system is a “0” system, a “1” system becomes in effect. On the contrary, if the service system is the “1” system, the “0” system becomes in effect. Thereby, the protection switching between the line concentrating interface units  151  and  152  is executed appropriately (steps S 7 -S 9 ). On the contrary, if there is any failure at the monitoring points B 1 -Bn in step S 4 , it is determined whether or not the monitoring ports A 1 -An and the monitoring ports B 1 -Bn are the same port (step S 5 ). If they are the same port, since it is concluded that a failure has occurred, the IP conversion unit  14  having the failure should be replaced (step S 6 ). 
   In the above-described procedures, it is supposed that the control unit  16   a  has detected failures more than (m) ports out of the monitoring points A 1 -An in a state that the line concentrating interface unit  151  is the service system. At this moment, the control units  16   a  presumes that the line concentrating interface unit  151  (“0” system) is abnormal to switch the switches  22  and  23  to switch the line concentrating interface unit  152  (“1” system) to the effective system when all the monitoring points B 1 -Bn are normal, or when the faulty ports of the monitoring points B 1 -Bn are not the same port as the faulty ports of the monitoring points A 1 -An. 
   In a status in which the line concentrating interface unit  151  is the active system, when any of the monitoring points B 1 -Bn is abnormal, the control unit  16   a  presumes that the corresponding IP conversion units  14  are abnormal and replaces the abnormal IP conversion units  14 . 
   In contrast, in a status in which the line concentrating interface unit  152  is the active system, when the control unit  16   a  detects failures of not less than (m) ports out of monitoring points A 1 -An, and also when all the monitoring points B 1 -Bn are normal, or when the faulty ports of the monitoring points B 1 -Bn are not the same port as the faulty ports of the monitoring points A 1 -An, the control unit  16   a  presumes that the line concentrating interface unit  152  is abnormal to switch the switches  22  and  23  and it switches the line concentrating interface unit  151  into the effective system. 
   In the status where the line concentrating interface unit  152  is the service system, when any of the monitoring points B 1 -Bn is abnormal, the control unit  16   a  assumes that the corresponding IP conversion units  14  are abnormal to replace the IP conversion units  14 . 
     FIG. 8  is a view illustrating an example of configuration information of the IP conversion unit  14  in the control unit  16 .  FIG. 9  shows a threshold (m) setting table to switch the line concentrating interface units  151  and  152  when any failure is detected at the line concentrating interface units  151  and  152 . The number of mounted setting ports (n) of the IP conversion units  14  in the configuration information limits the inputs of the thresholds (m) so as to be m≦n is satisfied. In this example, n=6 and m=4. These values may be set by the operations from the management equipment ME. It is acceptable for the gateway apparatus  1  to directly set the values of (n) and (m). That is to say, the gateway apparatus  1  may locally set the values of (n) and (m). Further, the operations from the management equipment ME remotely enable the protection switching of the line concentrating interface units  151  and  152  to utilize the switching for failure classifications and maintenances. Accordingly, the gateway apparatus improved in its redundancy and fault-tolerance performance and the method of the protection switching of the apparatus can be provided. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.