Abstract:
The present invention is to provide a control method for an information network connecting a plurality of telecommunication nodes by a ring transmission path and giving a plurality of priorities to frames which are exchanged among the telecommunication nodes, comprising the processes of: recognizing a bandwidth assurance value set up for each of the telecommunication nodes on the ring transmission path for each layer of the priorities; and judging whether or not a sum of the total of the bandwidth assurance value at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path when a discretionary one of the telecommunication nodes accepts an allocation of the bandwidth assurance value anew.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a network control method, telecommunication node, network management apparatus, and information network system, and in particular to a technique effectively applicable to an information network allowing a setup for reserving a telecommunication bandwidth.  
         [0003]     2. Description of the Related Art  
         [0004]     The RPR (Resilient Packet Ring) technique specified by IEEE 802.17-2004 allows three priority ratings, i.e., class A through C for a frame propagating through a ring. The class A and class B frames require an absolute assurance of a transmission bandwidth for sending a frame out to an RPR ring from an RPR station located on the RPR ring, which is called a CIR (Committed Information Rate). In order for the transmission bandwidth defined as a CIR to be absolutely assured on the RPR ring, the total of CIRs defined by each RPR station located on the RPR ring has to be smaller than the transmission bandwidth thereof.  
         [0005]     For instance, let it assume that the transmission bandwidth of an RPR ring is one Gbps and each one of six RPR stations existing on the RPR ring uniformly set the class A CIR at 200 Mbps. In this event, the total of the CIRs on the entire ring exceeds the transmission bandwidth of the RPR ring (i.e., 200 Mbps×6=1.2 Gpbs). Such a CIR setup precludes an absolute assurance for a transmission bandwidth. Accordingly, the class A CIR value set by each RPR station is notified to the other RPR stations by using a control frame flowing in the RPR ring, thereby enabling each RPR station to know the total of the class A CIRs which are currently reserved for the RPR ring according to the IEEE 802.17-2004.  
         [0006]     The IEEE 802.17-2004 lets the class A further define two subclasses, i.e., a subclass A 0  and subclass A 1 , with the subclass A 0  further specifying an operation for each RPR station notifying the RPR ring of the CIR value reserved by the own station as noted above, while the subclass A 1  not specifying as such, nor a class B CIR value specifying a notification to the RPR ring as with the subclass A 1 .  
         [0007]     The fact that the subclass A 1  and class B CIRs are not notified to the RPR ring precludes a prevention of each RPR station on an RPR ring setting the subclass A 0 /A 1  and class B CIR values where the total of which exceeds the transmission bandwidth, and a warning when such a setting has resulted.  
         [0008]     For example as shown by  FIG. 1 , in the case of transmitting among four RPR stations (i.e.,  2 - 1 ,  2 - 2 ,  2 - 3  and  2 - 4 ), each station sets respective CIR values for a subclass A 0 , subclass A 1  and class B (i.e., m 1 ,  11  and k 1  through m 4 ,  14  and k 4 ). The subclass A 0  CIR value is notified from the station which set the value to the other stations by using a control frame. The value of the subclass A 0  CIR=m 1  Mbps (megabit per second) at the RPR station  2 - 1  for example is notified to all the other RPR stations  2 - 2 ,  2 - 3  and  2 - 4 . And the RPR station  2 - 1  receives the subclass A 0  CIR values respectively set by the other stations. This enables each RPR station to know how much A 0  CIR (=m 1 +m 2 +m 3 +m 4 ) being reserved in the entire ring. Meanwhile, an A 1  CIR or B CIR is never notified mutually among the RPR stations. Under such a circumstance, each RPR station is only capable of knowing an assumed spare bandwidth by depending on the expression (1) below, in order to understand how many spare bandwidth out of the transmission bandwidth, i.e., “n” Mbps, possessed by the RPR ring: 
 
Assumed spare bandwidth= n −( m 1 +m 2 +m 3 +m 4)   (1); 
 
         [0009]     whereas the actual spare bandwidth is as expressed by (2) below: 
 
Actual spare bandwidth= n −( m 1 +m 2 +m 3 +m 4)−(11+12+13+14)−( k 1 +k 2 +k 3 +k 4)   (2) 
 
         [0010]     If each RPR station sets CIRs for a subclass A 1  and/or class B based on the assumed spare bandwidth, the total CIRs for the entire RPR ring possibly exceeds the transmission bandwidth of the RPR ring, resulting in being unable to assure the transmission bandwidth for the subclass A 1  and class B. Incidentally the subclass A 0  is continuously secured for a bandwidth by using an IDLE frame, thereby the transmission bandwidth being securely assured.  
         [0011]     A patent document 1 has disclosed a technique for accomplishing a fair distribution of an AF class output bandwidth by performing a bandwidth redistribution to each class of AF/EF in an MPLS network within each class, whereas having no reference to a technique for managing a relationship between the total of bandwidth allocated to each class hierarchy and the bandwidth of a physical medium.  
         [0012]     [Patent document 1] a laid-open Japanese patent application publication No. 2004-193975  
       SUMMARY OF THE INVENTION  
       [0013]     A purpose of the present invention is to provide a technique for enabling an accurate management of a total bandwidth allocated to each hierarchy based on a physical bandwidth of an information network in the information network in which priorities of frames that are exchanged among telecommunication nodes are hierarchically layered.  
         [0014]     Another purpose of the present invention is to provide an accurate bandwidth assurance within an RPR ring not only for the subclass A 0  CIRs but also for the subclasses A 1  and class B CIRs in the RPR ring.  
         [0015]     Yet another purpose of the present invention is to accurately deter a wrong bandwidth assurance by considering not only the subclass A 0  CIRs but also the subclass A 1  and class B CIRs in the RPR ring.  
         [0016]     A first aspect of the present invention is to provide a control method for an information network connecting a plurality of telecommunication nodes by a ring transmission path and giving a plurality of priorities to frames which are exchanged among the telecommunication nodes, comprising the processes of: recognizing a bandwidth assurance value set up for each of the telecommunication nodes on the ring transmission path for each layer of the priorities; and judging whether or not a sum of the total of the bandwidth assurance value at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path when a discretionary one of the telecommunication nodes accepts an allocation of the bandwidth assurance value anew.  
         [0017]     A second aspect of the present invention is to provide the control method for an information network according to the first aspect, wherein the ring transmission path is an resilient packet ring (RPR) compliant to the IEEE 802.17; the layer comprises a class A, which is made up of a subclass A 0  and subclass A 1 , and a class B; and the bandwidth assurance value is recognized for the class A and class B.  
         [0018]     A third aspect of the present invention is to provide a control method for an information network connecting a plurality of telecommunication nodes by a ring transmission path and giving a plurality of priorities to frames which are exchanged among the telecommunication nodes, comprising the processes of: collecting a bandwidth assurance value set up for each of the telecommunication nodes on the ring transmission path for each layer of the priorities by a network management apparatus which manages the telecommunication nodes; and judging whether or not a sum of the total of the bandwidth assurance value at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path by the network management apparatus when a discretionary one of the telecommunication nodes accepts an allocation of the bandwidth assurance value anew.  
         [0019]     A fourth aspect of the present invention is to provide the control method for an information network according to the third aspect, wherein the ring transmission path is an resilient packet ring (RPR) compliant to the IEEE 802.17; the layer comprises a class A, which is made up of a subclass A 0  and subclass A 1 , and a class B; and the bandwidth assurance value is collected for the class A and class B.  
         [0020]     A fifth aspect of the present invention is to provide a control method for an information network connecting a plurality of telecommunication nodes by a ring transmission path and giving a plurality of priorities to frames which are exchanged among the telecommunication nodes, comprising the processes of: notifying all the telecommunication nodes of a bandwidth assurance value set up for each of the telecommunication nodes on the ring transmission path for each layer of the priorities; and judging whether or not a sum of the total of the bandwidth assurance value at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path when a discretionary one of the telecommunication nodes accepts an allocation of the bandwidth assurance value anew.  
         [0021]     A sixth aspect of the present invention is to provide the control method for an information network according to the fifth aspect, wherein the ring transmission path is an resilient packet ring (RPR) compliant to the IEEE 802.17; the layer comprises a class A, which is made up of a subclass A 0  and subclass A 1 , and a class B; and the bandwidth assurance value for the class A and class B is notified from one of the telecommunication nodes to the others thereof.  
         [0022]     A seventh aspect of the present invention is to provide a control method for an information network connecting a plurality of telecommunication nodes by a ring transmission path and giving a plurality of priorities to first frames which are exchanged among the telecommunication nodes, comprising the processes of: notifying all the telecommunication nodes of a bandwidth assurance value set up for each thereof in the ring transmission path for each layer of the priorities by using a part of a second frame on another protocol layer for carrying the first frame; and judging whether or not a sum of the total of the bandwidth assurance value at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path when a discretionary one of the telecommunication nodes accepts an allocation of the bandwidth assurance value anew.  
         [0023]     An eighth aspect of the present invention is to provide the control method for an information network according the fifth aspect, wherein the ring transmission path is an resilient packet ring (RPR) compliant to the IEEE 802.17, and the second frame is the one compliant to a generic framing procedure (GFP) for carrying the first frame based on the RPR by including it.  
         [0024]     A ninth aspect of the present invention is to provide a telecommunication node for constituting an information network by connecting itself to a ring transmission path and giving a plurality of priorities to frames which are flown in the network, comprising: a notification unit for notifying the other telecommunication node of a bandwidth assurance value set up for the own telecommunication node on the ring transmission path for each layer of the priorities; a storage unit for storing the bandwidth assurance values for all the telecommunication nodes connected to the ring transmission path; and a judgment unit for judging whether or not a sum of the total of the bandwidth assurance value in a plurality of the telecommunication nodes at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path when the own telecommunication node accepts an allocation of the bandwidth assurance value anew.  
         [0025]     A tenth aspect of the present invention is to provide the telecommunication node according to the ninth aspect, wherein the ring transmission path is an resilient packet ring (RPR) compliant to the IEEE 802.17; the layer comprises a class A, which is made up of a subclass A 0  and subclass A 1 , and a class B; and the storage unit stores the bandwidth assurance value relating to the class A and class B.  
         [0026]     An eleventh aspect of the present invention is to provide a network management apparatus for managing an information network connecting a plurality of telecommunication nodes by a ring transmission path and giving a plurality of priorities to frames exchanged among the telecommunication nodes, comprising: a collection unit for collecting a bandwidth assurance value set up for each of the telecommunication nodes on the ring transmission path for each layer of the priorities; and a judgment unit for judging whether or not a sum of the total of the bandwidth assurance value at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path by the network management apparatus when a discretionary one of the telecommunication nodes accepts an allocation of the bandwidth assurance value anew.  
         [0027]     A twelfth aspect of the present invention is to provide the network management apparatus according to the eleventh aspect, wherein the ring transmission path is an resilient packet ring (RPR) compliant to the IEEE 802.17; the layer comprises a class A, which is made up of a subclass A 0  and subclass A 1 , and a class B; and the bandwidth assurance value is collected for the class A and class B.  
         [0028]     A thirteenth aspect of the present invention is to provide an information network system including a plurality of telecommunication nodes and a ring transmission path interconnecting the telecommunication nodes and giving a plurality of priorities to frames which are exchanged among the telecommunication nodes, wherein each of the telecommunication nodes includes a storage unit for storing the bandwidth assurance values for all the telecommunication nodes connected to the ring transmission path; and a judgment unit for judging whether or not a sum of the total of the bandwidth assurance value in a plurality of the telecommunication nodes at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path when the own telecommunication node accepts an allocation of the bandwidth assurance value anew.  
         [0029]     A fourteenth aspect of the present invention is to provide the information network system according to the thirteenth aspect, wherein the ring transmission path is an resilient packet ring (RPR) compliant to the IEEE 802.17; the layer comprises a class A, which is made up of a subclass A 0  and subclass A 1 , and a class B; and the storage unit stores the bandwidth assurance value relating to the class A and class B.  
         [0030]     A fifteenth aspect of the present invention is to provide an information network system including a plurality of telecommunication nodes, a ring transmission path interconnecting the telecommunication nodes and a network management apparatus for managing the telecommunication nodes and giving a plurality of priorities to frames which are exchanged among the telecommunication nodes, wherein the network management apparatus includes a collection unit for collecting a bandwidth assurance value set up for each of the telecommunication nodes on the ring transmission path for each layer of the priorities a judgment unit for judging whether or not a sum of the total of the bandwidth assurance value at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path by the network management apparatus when a discretionary one of the telecommunication nodes accepts an allocation of the bandwidth assurance value anew.  
         [0031]     A sixteenth aspect of the present invention is to provide the information network system according to the fifteenth aspect, wherein the ring transmission path is an resilient packet ring (RPR) compliant to the IEEE 802.17; the layer comprises a class A, which is made up of a subclass A 0  and subclass A 1 , and a class B; and the collection unit collects the bandwidth assurance value relating to the class A and class B.  
         [0032]     A seventeenth aspect of the present invention is to provide a control program for controlling a telecommunication node constituting an information network by connecting itself to a ring transmission path and giving a plurality of priorities to frames which are flown in the information network, wherein the control program makes the telecommunication node function as notification unit for notifying the other telecommunication nodes of a bandwidth assurance value set up for the own telecommunication node on the ring transmission path for each layer of the priorities; storage unit for storing the bandwidth assurance values for all the telecommunication nodes connected to the ring transmission path; and judgment unit for judging whether or not a sum of the total of the bandwidth assurance value in a plurality of the telecommunication nodes at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path when the own telecommunication node accepts an allocation of the bandwidth assurance value anew.  
         [0033]     An eighteenth aspect of the present invention is to provide a control program for a network management apparatus which manages an information network connecting a plurality of telecommunication nodes by a ring transmission path and giving a plurality of priorities to frames which are exchanged among the telecommunication nodes, wherein the control program makes the network management apparatus carry out the processes of: collecting a bandwidth assurance value set up for each of the telecommunication nodes on the ring transmission path for each layer of the priorities; and judging whether or not a sum of the total of the bandwidth assurance value at the present and a newly allocated value of the bandwidth assurance value exceeds a physical transmission bandwidth of the ring transmission path when a discretionary one of the telecommunication nodes accepts an allocation of the bandwidth assurance value anew. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]      FIG. 1  is a conceptual diagram describing a setup and operation of a CIR in an RPR ring as a reference technique of the present invention;  
         [0035]      FIG. 2  is a conceptual diagram exemplifying a comprisal of an information network system according to an embodiment of the present invention;  
         [0036]      FIG. 3  is a conceptual diagram exemplifying a comprisal of a network management system constituting an information network system according to an embodiment of the present invention;  
         [0037]      FIG. 4  is a conceptual diagram exemplifying a structure of a data base possessed by a network management system according to an embodiment of the present invention;  
         [0038]      FIG. 5  is a flow chart exemplifying an operation of a network management system according to an embodiment of the present invention;  
         [0039]      FIG. 6  is a conceptual diagram showing an example configuration of an RPR station constituting an information network according to another embodiment of the present invention;  
         [0040]      FIG. 7  is a conceptual diagram exemplifying a structure of a topology data base comprised by an RPR station constituting an information network according to another embodiment of the present invention;  
         [0041]      FIG. 8  is a conceptual diagram exemplifying a structure of a control frame exchanged between RPR stations constituting an information network according to another embodiment of the present invention;  
         [0042]      FIG. 9  is a conceptual diagram exemplifying a structure of a control frame, in more detail, exchanged between RPR stations constituting an information network according to another embodiment of the present invention;  
         [0043]      FIG. 10  is a conceptual diagram exemplifying an information setup of an ATD frame exchanged between RPR stations constituting an information network according to another embodiment of the present invention;  
         [0044]      FIG. 11  is a conceptual diagram exemplifying a configuration of an RPR unit constituting an information network according to yet another embodiment of the present invention; and 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]     The following is a detailed description of the preferred embodiment of the present invention while referring to the accompanying drawings.  
       First Embodiment  
       [0046]      FIG. 2  is a conceptual diagram exemplifying a comprisal of an information network system according to an embodiment of the present invention;  FIG. 3  is a conceptual diagram exemplifying a comprisal of a network management system constituting an information network system according to the present embodiment; and  FIG. 4  is a conceptual diagram exemplifying a structure of a data base possessed by a network management system according to the present embodiment.  
         [0047]     As exemplified by  FIG. 2 , an information network system according to the present embodiment includes an RPR ring  10 , a plurality of RPR stations  20  interconnected by way thereof and a network management system  30 .  
         [0048]     The RPR ring  10  is dually structured by a ringlet  11  and a ringlet  12  which have mutually opposite transmission directions of information.  
         [0049]     Each of a plurality of RPR stations interconnected by the RPR ring  10  is connected to an information network (not shown herein) such as a LAN byway of a router  60 . And each RPR station  20  generates a data frame from information received from the LAN by way of the router  60  and relays information between the LANs by way of the RPR ring  10  by using the data frame.  
         [0050]     Each RPR station  20  is connected to the network management system  30  by way of a management-use information network  13  such as SONET/SDH (synchronous optical network/synchronous digital hierarchy), other than the RPR, for example.  
         [0051]     As exemplified by  FIG. 3 , the network management system  30  according to the present embodiment comprises an MPU (micro processor unit)  31 , a main storage  32 , a network interface  33 , an external storage apparatus  34 , a user interface  35  and a bus  36 .  
         [0052]     The MPU  31  controls the entirety of the network management system  30  by executing a program (not shown herein) stored by the main storage  32 .  
         [0053]     The network interface  33  is connected to each of the RPR stations  20  by way of the management-use information network  13  and collects information from the RPR stations  20  by way of the network interface  33  and management-use information network  13 .  
         [0054]     The present embodiment is configured to let the main storage  32  store a bandwidth management program  32   a  and carry out a bandwidth management processing as exemplified by a later described flow chart shown in  FIG. 5  as a result of the MPU  31  executing the bandwidth management program  32   a.    
         [0055]     The external storage apparatus  34  is equipped by a CIR value management data base  37  for storing information such as a CIR value collected from each of the RPR stations  20  by way of the management-use information network  13 .  
         [0056]     As exemplified by  FIG. 4 , the CIR value management data base  37  stores pieces of information, i.e., RPR station numbers  37   a,  subclass A 0 _CIR values  37   b,  subclass A 1 _CIR values  37   c,  class B_CIR values  37   d,  et cetera.  
         [0057]     As described above, the RPR is capable of giving three priorities, that is, classes A, B and C, to a frame propagating in the RPR ring  10 . Absolute assurance of a transmission bandwidth is required for the class A and B frames in order to send the frames to the RPR ring  10  from the RPR stations on the RPR ring, which is called as a CIR (Committed Information Rate) In order to absolutely assure a transmission bandwidth defined as a CIR, the total of CIRs defined at the respective RPR stations  20  existing on the RPR ring  10  must be smaller than a physical transmission bandwidth thereof (noted as “ring bandwidth RB” hereinafter).  
         [0058]     The present embodiment is configured in such a manner that the network management system  30  centrally manages a CIR value for each of the plurality of RPR stations  20  by using the CIR value management data base  37  thereby controlling the total of CIRs defined at the RPR stations  20  to be smaller than a physical transmission bandwidth of the RPR ring  10 .  
         [0059]     In the CIR value management data base  37 , the RPR station number  37 a stores the RPR station number uniquely given to each of the RPR stations  20  connected to the RPR ring  10 . The subclass A 0 _CIR value  37   b  and subclass A 1 _CIR value  37   c  store respective CIR values of the subclass A 0  and subclass A 1  of the class A for an RPR station  20  identified by the corresponding RPR station number  37   a.  Likewise, the class B_CIR value  37   d  stores a CIR value of the class B for an RPR station  20  identified by the corresponding RPR station number  37   a.    
         [0060]     The user interface  35 , comprising a keyboard and a display for example, is used for displaying information such as a content of the CIR value management data base  37  and for inputting information at the time of a system manager of the network management system  30  working on its management.  
         [0061]     As described above, the present first embodiment centralizes the CIRs for the plurality of RPR stations  20  by using the network management system  30  capable of collecting and managing the pieces of information such as the setup information, operating states, et cetera, of all the RPR stations  20  existing on the RPR ring  10 . The network management system  30  is capable of collecting individual CIR setup information from all the RPR stations  20  existing on the RPR ring  10  and integrally managing those pieces of information in the CIR value management data base  37 .  
         [0062]     The bandwidth management program  32   a  stored by the network management system  30  has the function of reading respective CIR values of the subclass A 0 , subclass A 1  and class B set up for each of the RPR stations  20  out thereof.  
         [0063]     And the network management system  30  simultaneously collects information on a physical transmission bandwidth (i.e., a ring bandwidth RB) possessed by the RPR ring  10  from the RPR station  20 .  
         [0064]     For example, the data base comprised by the network management system  30  for managing the RPR ring network shown by  FIG. 2  manages the CIR information of each RPR station  20  as shown by  FIG. 4 .  
         [0065]     That is, in the example shown by  FIGS. 2 and 4 , the CIR values of the subclasses A 0  and A 1  and class B are m 1 ,  11  and k 1 , respectively, for the RPR station  20  by the RPR station number  37   a  being “2-1”, and these CIR values are recorded in the subclass A 0 _CIR values  37   b,  subclass A 1 _CIR values  37   c  and class B_CIR value  37   d  for the “2-1” of the RPR station numbers  37   a  in the CIR value management data base  37 .  
         [0066]     The network management system  30  is capable of grasping the total of the CIR values reserved for the entirety of the RPR ring  10  and comprehending a spare capacity of transmission bandwidth thereof by using the CIR value management data base  37 .  
         [0067]     If a CIR setup is made exceeding the transmission bandwidth of the RPR ring  10 , the network management system  30  issues a warning to an applicable RPR station.  
         [0068]     The following description is of an example operation of the network management system  30  according to the present embodiment by referring to the flow chart shown by  FIG. 5 , et cetera.  
         [0069]     First, the network management system  30  collects information on the ring bandwidth RB of the RPR ring  10  and on the CIR setup conditions of the respective classes (i.e., subclasses A 0  and A 1 , and class B) from each of the RPR stations  20 , and stores in the CIR value management data base  37  (step  201 ).  
         [0070]     Next is to calculate a spare bandwidth Ne by subtracting the ring bandwidth RB from the total of the usage bandwidth for the each class at each of the RPR stations  20  (the total of RPR stations  20 =NR) at the moment (step  202 ).  
         [0071]     Then, when an additional request for bandwidths for the subclasses A 0 , A 1  and class B occurs at a random RPR station  20  (step  203 ), the network management system  30  judges whether the additionally requested bandwidth N exceeds the current spare bandwidth Ne (step  204 ) and, if it exceeds, rejects the additional request for the request bandwidth N and issues a warning to the requester (step  206 ) followed by going back to a standby for additional request for a new bandwidth.  
         [0072]     If the requested bandwidth N is smaller than the spare bandwidth Ne in the judgment of the step  204 , judges that an allocation of the additional request for the requested bandwidth is possible and gives a permission to allocate the requested bandwidth N (step  205 ), followed by going back to the step  202  and recalculating a spare bandwidth Ne in preparation for a next allocation request.  
       Second Embodiment  
       [0073]     While the above described first embodiment has exemplified the case of the network management system  30  collecting and managing a CIR value for each of the RPR stations  20 , the second embodiment exemplifies the case of each of a plurality of RPR stations  20  mutually exchanging a setup value of a CIR and each thereof managing the CIR value. Note that the basic configuration of an information network system is the same as  FIG. 2 , and that the same component number is assigned to the same component whose description is omitted.  
         [0074]     An RPR station  20  conventionally notifies other RPR stations of a setup value of the CIR only for the subclass A 0  and the system of all the RPR stations  20  existing in an RPR ring  10  grasping the subclass A 0  CIR bandwidth of the entire RPR ring  10  is standardized by the IEEE 802.17.  
         [0075]     The present embodiment exemplifies the case of an RPR station  20  having the functions of notifying other RPR stations  20  also of CIR information of the subclass A 1  and class B, receiving the similar information from the other RPR stations  20 , and preventing a CIR setup exceeding a spare capacity from being carried out by calculating a spare capacity of the transmission bandwidth of the RPR ring  10  from the aforementioned information.  
         [0076]      FIG. 6  exemplifies a configuration of each of the RPR stations  20  according to the present second embodiment. Each of the RPR stations  20  connected to the RPR ring  10  includes a filter  21 , a transit queue  21   a,  a CIR management unit  22 , a scheduler  23 , a Drop queue  24 , an Add queue  25 , a control frame processing unit  26 , a topology data base  27 , a control frame generation unit  28 , an RPR framer  29  and an Ethernet (registered trademark) bridge  29   a.    
         [0077]     The CIR management unit  22 , control frame processing unit  26 , topology data base  27  and control frame generation unit  28  for example can be implemented by a control program such as software, firmware, et cetera, of a computer constituting an RPR station  20 .  
         [0078]     A data frame of an RPR frame coming in from the RPR ring  10  is imported by the Drop queue  24  by each class and added information is removed by the RPR framer  29 , followed by being handed over to the corresponding router  60  by way of the Ethernet bridge  29   a.    
         [0079]     Conversely, transmission data coming in from the router  60  is structured as an RPR frame by the RPR framer  29 , stored in the Add queue  25  by each class and sent out to the RPR ring  10  at a transmission timing controlled by the scheduler  23 .  
         [0080]     A frame simply passing through the RPR ring  10  is once retained by the transit queue  21 a and then sent out to the RPR ring  10  at a transmission timing controlled by the scheduler  23 .  
         [0081]     As described above, an RPR frame coming from the RPR ring  10  is sorted by the filter  21 , that is, a data frame is sorted into the Drop queue  24 , while a control frame is sorted into the control frame processing unit  26 .  
         [0082]     The control frame includes a so-called topology frame for indicating an operating state and setup state of other RPR stations, with the topology frame including a subclass A 0  CIR value as information. These pieces of information are extracted and managed in the topology data base  27  for each RPR station  20 . And the control frame generation unit  28  is a functional block for generating a topology frame for the purpose of notifying other RPR stations  20  of topology data of the own station. The subclass A 0  CIR setup value of the own station is mounted to the topology frame in this event and notified to the other RPR stations  20 .  
         [0083]     As exemplified by  FIG. 7 , the topology database  27  includes a description  27   a,  a variable  27   b  and a setup value  27   c.  The present second embodiment comprises a management item  27   e  (i.e., a reservedA 1 Rate [ 0 ], a reservedA 1 Rate [ 1 ], a reservedBRate [ 0 ] and a reservedBRate [ 1 ]) for the purpose of managing the subclass A 1  and class B CIRs in addition to a management item  27   d  (i.e., a reservedRate [ 0 ] and a reservedRate [ 1 ] for the purpose of managing the conventional class A 0  CIR value.  
         [0084]     This configuration enables each of the RPR stations  20  to manage all the CIRs of not only the conventional class A 0 , but also those of the subclass A 1  and class B.  
         [0085]     A frame for carrying topology information among the RPR station  20  uses an ATD (Attribute Discovery) frame whose frame format, header information and ATD information are all defined by the chapter  11 . 3 . 5  and chapter  11 . 4  of the IEEE 802.17.  
         [0086]     Information of the subclass A 1  CIR and class B CIR is notified to the RPR ring  10  by means of an ATD frame which allows a definition of information carried by the ATD frame by a type field of the typeLengthValue field shown by the IEEE 802.17— FIG. 11 . 14  (refer to IEEE 802.17— FIG. 11 . 15 ) (refer to IEEE 802.17—Table  11 . 7 ). Among them, pieces of information on the subclass A 1  CIR and class B CIR are notified by using the Organization-specific ATT shown by the chapter  11 . 4 . 8  of the IEEE 802.17.  
         [0087]     The Organization Data field shown by the IEEE 802.17— FIG. 11 . 23  writes the information as follows:  
         [0088]     1) Subclass A 1  or class B  
         [0089]     2) CIR setup value of the ringlet  0  and ringlet  1  Having received the frame, the RPR station  20  writes the CIR information in the topology data base  27 .  
         [0090]     If all pieces of the topology data of the RPR ring  10  are lined up in the topology data base  27 , the CIR management unit  22  of the RPR station  20  is able to grasp an accurate spare capacity (i.e., a spare bandwidth Ne) of the transmission bandwidth (i.e., a ring bandwidth RB) for the RPR ring  10 .  
         [0091]     The present second embodiment is configured so that the CIR management unit  22  rejects a setup and issues a warning to the setter by an appropriate alarm if a random RPR station  20  existing in the RPR ring  10  tries to set up a CIR requiring larger bandwidth than the spare capacity (i.e., a spare bandwidth Ne) of the RPR ring transmission bandwidth.  
         [0092]      FIG. 8  is a conceptual diagram exemplifying a structure of a control frame for exchanging information of the subclass A 1  CIR and class B CIR among each of the RPR stations  20  by using the control frame  40  as described above according to the present second embodiment.  
         [0093]     The control frame  40  includes a control header  41 , an attribute discovery payload  42  and a frame check sequence  43 .  
         [0094]     The control header  41  has the structure exemplified by  FIG. 9 . That is, the control header  41  includes a tt 1  field  41   a  for controlling a reaching life within an RPR ring  10 , a baseControl field  41   b  storing control information and a da field for indicating an address (i.e., a broadcast in this case).  
         [0095]     The attribute discovery payload  42  includes a control type  42   a,  a version  42   b  and a type length value  42   c.    
         [0096]     The type length value  42   c  is segmented to the respective fields, i.e., “res1”, “type”, “res2” and “length” and is set by an attDataUnit [length]. The present embodiment is configured to set the value=1023, Name=ATT_ORG_SPECIFIC (defined name of a tag), Length=Size=4 through 1023 among the type encoding exemplified by  FIG. 10 .  
         [0097]     And the part of the attDataUnit [length] is set up by the respective CIR capacities of the ringlet  0  and ringlet  1  for the subclass A 1  and those of the ringlet  0  and ringlet  1  for the class B as indicated by the data [ 0 ], data [ 1 ] through data [n- 1 ] as the “organizationData”.  
         [0098]     And such control frames  40  are exchanged among the RPR stations  20 , and recorded in the management item  27   d  and management item  27   e  of the topology database  27 , thereby enabling the CIR management units  22  of all the RPR stations  20  connected to the RPR ring  10  to manage not only the subclass A 0  CIR value but also the subclass A 1  and class B CIR values.  
       Third Embodiment  
       [0099]     In the case of transmitting information by building an RPR ring  10  on a SONET/SDH, transmitting it as an RPR/over/GFP/SONET by using a GFP (Generic Framing Procedure) frame is common.  
         [0100]     While the above described second embodiment notifies the information of the subclass A 1  CIR and class B CIR by an ATD frame (i.e., a control frame  40 ), in the case of using a GFP frame, however, an Extension Header of the GFP frame can also be used as a method for notifying other RPR stations of the information of the subclass A 1  CIR and class B CIR.  
         [0101]      FIG. 11  is a conceptual diagram exemplifying a configuration of an RPR unit  70  for carrying out an operation of structuring a frame when sending the frame by layering as described above.  
         [0102]     The RPR unit  70  contains RPR stations  20  connected to a plurality of Ethernet ports  74 , and comprises a GEP framer  71  and a VCAT framer  72 . The VCAT framer  72  is connected to an optical communication medium  73  on which an RPR ring  10  is built.  
         [0103]     That is, the RPR framer  29  within the RPR station  20  encapsulates a MAC frame  81  in an RPR_MAC frame  82 , and the GEP framer  71  further encapsulates the RPR_MAC frame  82  in a GFP frame  83 .  
         [0104]     The VCAT framer  72  maps the GFP frame  83  in a VCAT frame  84  of the VCAT (Virtual Concatenate), and further encapsulates the VCAT frame  84  in a SONET frame  85  and exchanges with the optical communication medium  73 .  
         [0105]     That is, the GFP frame  83  includes a type field  83   a,  a type field error check &amp; correction unit  83   b,  an extended header field  83   c  and an extended header field error check &amp; correction unit  83   d.    
         [0106]     The present third embodiment is configured to mount the setup values of the subclass A 1  and class B CIRs relating to the ringlets  0  and  1  at each of the RPR stations  20  constituting the above described RPR ring  10  on a part of the GFP frame  83  (i.e., the extended header field  83   c  in this case) and notify all the other RPR stations  20  within the RPR ring  10 .  
         [0107]     Note that a usage method of the extended header field  83   c  for the GFP frame  83  is to allocate a specific part of the extended header field  83   c  from the head part down sequentially per each of the RPR stations  20  by using the above described RPR station number  37   a  for example, and to store the setup values of the subclass A 1  and class B CIRs relating to the own station in the specific part allocated to the own station over at each of the RPR stations  20 .  
         [0108]     This configuration enables each of the RPR stations  20  to identify as to which RPR station  20  a setup value of a CIR belongs to by using an offset value from the head part of the specific part in the extended header field  83   c.    
         [0109]     As described thus far, the above described each embodiment according to the present invention enables each RPR station  20  to recognize information on the subclass A 1  and class B CIRs of the other RPR stations  20  accurately if all the RPR stations  20  within the RPR ring  10  integrally comprise either one mechanism of the above described first, second or third embodiments. This prevents a wrong setup of a CIR exceeding the physical transmission bandwidth of the RPR ring  10  (i.e., the ring bandwidth RB), which means that the RPR ring  10  comprises a capability of providing the end users connecting to each of the RPR stations  20  with a class B service assuring a complete bandwidth by way of the router  60 .  
         [0110]     Note that it goes without saying that the present invention can be changed variously within the scope thereof in lieu of being limited to the configurations exemplified by the above described embodiments.  
         [0111]     The present invention enables an accurate management of the total bandwidth given to each layer of priorities for frames which are exchanged among telecommunication nodes based on the physical bandwidth of an information network therein in which the priorities for the aforementioned frames are layered.  
         [0112]     Also enabled is an accurate bandwidth assurance within an RPR ring for not only the subclass A 0  CIR but also the subclass A 1  and class B CIRs in the RPR ring.  
         [0113]     Also enabled is a definite prevention of a wrong bandwidth assurance in consideration of not only the subclass A 0  CIR but also the subclass A 1  and class B CIRs in the RPR ring.