Band control device

In a band control device having a trunking function used in an end apparatus, a relaying apparatus, and the like, a distributor distributes a traffic to a sub-logical link into which specified ones of the physical links in the logical link are aggregated so as to meet a specified condition of the traffic. Also, the physical links of a number corresponding to the traffic amount is assigned to the sub-logical link. A controller transmits/receives a message for establishing the sub-logical link to/from an opposite controller, and further relays the message to the subsequent apparatus.

DESCRIPTION OF THE EMBODIMENTS Embodiment (1) A basic arrangement of a band control device 100 according to the present invention is the same as that of the band control device 100 shown in FIG. 14 B, which is composed of a distributor 20 , a collector 30 , and an aggregation controller 40 FIG. 2 shows an embodiment of the distributor 20 according to the present invention in which the prior art distributor 20 is extended. The distributor 20 includes an identifying data table 22 prepared based on identifying information 84 from the aggregation controller 40 (see FIG. 14B ) or a management tool (not shown) (hereinafter sometimes both are commonly referred to as controller 40 ), an object identifying portion 21 for identifying the object traffic 83 a which meets a specified condition and the non-object traffic 83 b which does not meet the specified condition based on identifying data 84 a of the table 22 in a traffic 83 received from a MAC client 50 (see FIG. 14B ), an object assignment portion 24 for assigning the received object traffic 83 a to ports 10 _ 1 - 10 _ 3 connected to sub-logical links 82 _ 3 and 82 _ 4 , and a non-object assignment portion 25 for assigning the received non-object traffic 83 b to other ports 10 _ 4 and 10 _ 5 . In addition, the distributor 20 includes a manager 23 for managing the object assignment portion 24 and the non-object assignment portion 25 by update information 87 and 88 based on a signal 90 from the controller 40 , a traffic monitor 26 for monitoring the object traffic 83 a and the non-object traffic 83 b to transmit traffic amount information 86 to the manager 23 , and a monitoring timer 27 for providing a motoring timing signal 85 a to the monitor 26 based on a monitoring interval setting value 85 from the controller 40 . FIGS. 3 A- 3 C show embodiments of the identifying data tables 22 . The tables 22 are the identifying information 84 which indicates the conditions for identifying the object traffic 83 a, and there are various identification methods. For example, in the table 22 shown in FIG. 3 A, the traffic 83 having source MAC address&equals;“00:00:0e:14:32:22” and destination MAC address&equals;“00:e0:5f:53:22:21” is established to be the object traffic 83 a. Namely, the traffic 83 transmitted from the end apparatus having the MAC address&equals;“00:00:0e:14:32:22” to the end apparatus having the MAC address&equals;“00:e0:5f 53:22:21” is selected as the object traffic 83 a, which is transmitted through one of e.g. ports 10 _ 1 - 10 _(N- 1 ) corresponding to the sub-logical link. Also, it is possible to set upper layer data such as a source/destination port No. of TCP header, a source/destination IP address of IP header, and a Type Of Service (TOS) field in the table 22 . In the table 22 of FIG. 3 B, the traffic 83 addressed to the end apparatus having the destination port No.&equals;“69” and the IP address&equals;“124.10.5.38” from the end apparatus having the IP address&equals;“133.10.15.3” is established as the object traffic 83 a. Furthermore, it is also possible to establish a plurality of sub-logical links 82 _ 3 and 82 _ 4 e.g. in a single logical link 81 _ 1 as shown in FIG. 1C . FIG. 3C shows an embodiment of the table 22 corresponding to the sub-logical links 82 _ 3 and 82 _ 4 . The conditions for identifying the object traffic 83 a which occupies the sub-logical link 82 _ 3 are the same as that of FIG. 3 A, and the conditions for identifying the object traffic 83 a which occupies the sub-logical link 82 _ 4 are the source IP address&equals;“12.35.120.25”, the destination IP address&equals;“122.131.11.221” and the port No.&equals;“69”. {circle over (1)}: Occupation by Sub-logical Link In FIG. 2 , the object traffic 83 a and non-object traffic 83 b thus identified are respectively transmitted to the object assignment portion 24 and the non-object assignment portion 25 . The object assignment portion 24 transmits the object traffic 83 a to one of the ports 10 _ 1 - 10 _ 3 to which the sub-logical links 82 _ 3 and 82 _ 4 assigned by the manager 23 are connected, while the non-object assignment portion 25 transmits the non-object traffic 83 b to either of the port 10 _ 4 or 10 _ 5 assigned by the manager 23 . It is to be noted that the port corresponding to the sub-logical link is notified to the manager 23 from the controller 40 , so that this notification enables the object traffic 83 a and the non-object traffic 83 b to be transmitted to the half fixedly assigned ports. Also, it is possible for the manager 23 not only to transmit the object traffic 83 a and the non-object traffic 83 b to the half fixedly assigned ports, but also to dynamically change the number of the physical links (number of ports) aggregated into the sub-logical link corresponding to the change of the traffic amount. Furthermore, it is also possible for the manager 23 to release the sub-logical link in case the traffic amount of the object traffic 83 a is too small to occupy a single physical link. {circle over (2)}: Dynamic Change of Physical Link Number Hereinafter, the operation procedures of changing the number of the physical links (ports) assigned to the sub-logical links corresponding to the change of the traffic amount, and of releasing the sub-logical link will be described referring to FIG. 6 , after firstly describing the outline arrangement of the manager 23 in FIGS. 4 and 5 A- 5 C. FIG. 4 shows an embodiment of the manager 23 , which is composed of a threshold value table 71 , a discriminating portion 72 , a monitoring time table 73 , a counter 74 , a number changing portion 75 , and a port manager 76 . Also, the port manager 76 includes a port managing table 77 , and the counter 74 includes a decreasing counter and a releasing counter (both are not shown). The decreasing counter serves to discriminate whether or not the number of the ports should be decreased, and counts “frequency” in case where the traffic amount of the object traffic 83 a is equal to or less than “a predetermined threshold value”. The releasing counter serves to discriminate whether or not the establishment of the sub-logical link 82 _ 3 should be released in case the traffic amount of the object traffic 83 a is too small to occupy a single physical link, and counts the “frequency” in case where the traffic amount of the object traffic 83 a is equal to or less than “a predetermined threshold value”. FIGS. 5 A- 5 C respectively show a threshold value table 71 , a monitoring table 73 , and a port managing table 77 . The setting values of the tables 71 , 73 , and 77 are provided by the controller 40 . In the table 71 of FIG. 5 A, as the above-mentioned “predetermined threshold value”, “traffic amount”&equals;80 Mbps, 160 Mbps, 240 Mbps, and 320 Mbps . . . , “port available rate for object traffic”&equals;80%, and “port available rate for non-object traffic”&equals;80%, are set corresponding to “port number”&equals; 1 , 2 , 3 , 4 , . . . occupied by the object traffic 83 a or the non-object traffic 83 b. In the table 73 of FIG. 5 B, as the above-mentioned “frequency”, the frequency&equals;“50” is set for a threshold value of the releasing counter and the decreasing counter. In the table 77 of FIG. 5 C, it is shown whether each of the ports 10 _ 1 - 10 _ 5 is the port for the object traffic or the non-object traffic. Namely, it is shown that the ports 10 _ 1 and 10 _ 2 are “&compfn;: port for the object traffic”, and the ports 10 _ 3 - 10 _ 5 are ″&square;: port for the non-object traffic. FIG. 6 shows operation procedure examples of changing the number of the physical links and of releasing the sub-logical link. Hereinafter, the operation of changing the number (two of physical links 80 _ 9 and 80 _ 10 at present) of the physical links 80 included in the sub-logical link 82 _ 3 shown in FIG. 2 and the releasing operation of the sub-logical link 82 _ 3 will be described. Although the sub-logical link 82 _ 4 is also established in the logical link 81 _ 3 in FIG. 2 at present, the sub-logical link 82 _ 4 is supposed not to be established. Accordingly, the port 10 _ 3 (physical link 80 _ 11 ) is a port for a non-object traffic, “&compfn;” is set in the ports 10 _ 1 and 10 _ 2 , and “&square;” is set in the ports 10 _ 3 - 10 _ 5 of the table 77 in FIG. 5B . In FIG. 2 , the traffic monitor 26 monitors the traffic amount of the object traffic 83 a and the non-object traffic 83 b per unit time based on the monitoring timing signal 85 a notified from the monitoring timer 27 at the fixed time intervals, so that the traffic amount information 86 is notified to the manager 23 . Step S 10 in FIG. 6 : The discriminating portion 72 (see FIG. 4 ) of the manager 23 receives the present traffic amount information 86 . Step S 11 : The discriminating portion 72 compares the information 86 with the threshold value table 71 . (1) In case the information 86 is the traffic amount of the object traffic 83 a &equals;100 Mbps for example, the discriminating portion 72 calculates as follows: Since the number of the physical links occupied at present is two, 160 Mbps (traffic amount in case of two physical links)×80% (available rate)&equals;128 Mbps, and 80 Mbps (traffic amount in case of one physical link)×80%&equals;64 Mbps are calculated from the threshold value table 71 . Then, the discriminating portion 72 discriminates that the present traffic amount&equals;100 Mbps is between the both traffic amounts, i.e. 128 Mbps and 64 Mbps, so that “regular level” not requiring the change of the number of the physical links is discriminated. (2) In case of the traffic amount of the object traffic 83 a &equals;150 Mbps for example, the discriminating portion 72 discriminates it to be “number increasing level” since the traffic amount&equals;150 Mbps exceeds 160 Mbps (traffic amount for two physical links)×80% (available rate)&equals;128 Mbps. (3) In case of the traffic amount of the object traffic 83 a &equals;50 Mbps for example, the discriminating portion 72 discriminates it to be “number decreasing level” since the traffic amount&equals;50 Mbps is equal to or less than 80 Mbps (traffic amount for one physical link)×80%&equals;64 Mbps. (4) Similarly, in case of the traffic amount of the object traffic 83 a &equals;50 Mbps, the discriminating portion 72 discriminates it to be “occupation releasing level” since the traffic amount&equals;50 Mbps is equal to or less than 80 Mbps (traffic amount for one physical link)×80%&equals;64 Mbps. Steps S 12 and S 13 : In case the “regular level” of (1) is discriminated at step S 11 , the discriminating portion 72 does not transmit a signal 91 to the number changing portion 75 , but resets all of the counters (decreasing counter and releasing counter) with a signal 92 . This resetting enables the count indicating how many times the traffic amount of the object traffic 83 a has been continuously equal to or less than the threshold value to be returned to the initial value “0”. Thus, the number of the physical links is maintained. Steps S 14 and S 15 : In case the “number increasing level” of (2) is discriminated at step S 11 , the discriminating portion 72 notifies the f“number increasing level” to the number changing portion 75 with the signal 91 , and then resets all of the counters with the signal 92 . The number changing portion 75 provides a number increasing instruction signal 94 to the port manager 76 . The port manager 76 changes e.g. the port 10 _ 3 in the table 77 to “&compfn;: object traffic port” from “&square;: non-object traffic port”. Then, the port manager 76 provides, to the non-object assignment portion 25 (see FIG. 2 ), the update information 88 indicating that the physical link 80 _ 11 (port 10 _ 3 ) should be deleted and the number of the links should be decremented by “1”, and provides, to the object assignment portion 24 (see FIG. 2 ), the update information 87 indicating that the deleted physical link 80 _ 11 should be added to the sub-logical link 82 _ 3 and the number of the links should be incremented by “1”. Steps S 19 . S 20 , and S 13 : In case the discriminating portion 72 discriminates the “number decreasing level” at step S 11 , the decreasing counter is incremented by “1” and the releasing counter is reset (at step S 20 ). Furthermore, in case the value of the decreasing counter does not exceed the count set in the table 73 &equals;“50” (namely, in case the count indicating how many times the number decreasing level continuously occurs does not exceed “50”), the number of the physical links is maintained. Steps S 20 , S 21 , and S 15 : In case the value of the decreasing counter exceeds the count&equals;“50” (namely, in case the count indicating how many times the number decreasing level continuously occurs exceeds “50”), the number of the physical links is decremented by “1” in the same procedure as the above-mentioned procedure of incrementing the physical link by “11”, and then all of the counters are reset. {circle over (3)}: Release of Occupation Link Steps S 16 , S 17 , and S 13 : In case the “occupation release level” is discriminated at step S 11 , the discriminating portion 72 provides the signal 92 for incrementing the releasing counter by “1” to the counter 74 . The counter 74 discriminates whether or not the value of the releasing counter exceeds the counter of the releasing counter&equals;“50” in the table 73 . Resultantly, in case the count does not exceed “50”, nothing is done. Namely, the number of the links is maintained. Steps S 17 , S 18 , and S 15 : In case the value of the releasing counter exceeds the count of the releasing counter&equals;“50” in the table 73 , the counter 74 notifies the fact to the number changing portion 75 with a signal 93 , so that the number changing portion 75 provides a number decreasing instruction signal 94 to the port manager 76 . The port manager 76 sets all of the ports 10 in the table 77 to “&square;: non-object traffic port”, and notifies that all of the ports are set to “&square;” to the object assignment portion 24 and the non-object assignment portion 25 respectively by the update information 87 and 88 . The object assignment portion 24 and the non-object assignment portion 25 respectively recognize that the occupation is released to distribute the object traffic 83 a and the non-object traffic 83 b to all of the ports 10 . It is to be noted that the number decrease is discriminated by using a single decreasing counter, a single physical link is decreased, and by repeating this operation “n” physical links are decreased. Furthermore, it is possible that the counter 74 is provided with a 1-decrementing counter, a 2-decrementing counter, . . . , and a “n”-decrementing counter. The discriminating portion 72 can discriminate whether or not the object traffic amount is in the level in which physical links 1 , 2 , . . . , “n” numbers may be decremented, and physical links “n” numbers can be decremented at a single discrimination by storing the discriminated continuous counter in the decreasing counters. {circle over (4)} Degeneracy of Non-occupation Link Also, in case the degeneracy of the number of the physical links occurs by the fault in the sub-logical link established for a specified object traffic, the number is dynamically changed and returned to the original number. On the other hand, in case the fault occurs in the physical link for the non-object traffic, there is no physical link for the non-object traffic, so that the case where the non-object traffic can not be transmitted occurs. Generally, when a link down state occurs, the number itself, in the port managing table 77 , of the links aggregated by the link aggregation is decreased. The port manager 76 checks whether or not all of the ports 10 are occupied by the object traffic 83 a in the table 77 . If they are occupied, the fact is notified to the number changing portion 75 . The number changing portion 75 instructs the port manager 76 to decrease the number of the links in the port with the lowest priority. The priority of the port is supposed to be set in the apparatus. The port manager 76 updates the port managing table 77 to notify the result to the object assignment portion 24 and the non-object assignment portion 25 . Thus, the transmission disabling state of the non-object traffic 83 b can be avoided. It is to be noted that the collector 30 (see FIG. 14B ) which receives the object traffic 83 a and the non-object traffic 83 b from the distributor 20 of the opposite band control device 100 may transmit the received object traffic 83 a and the non-object traffic 83 b to the MAC client 50 of the upper layer in the same way as the prior art collector 30 . Accordingly, if at least the apparatus on the transmitting side between two end apparatuses 1 , between two end apparatus 1 , and between the relaying apparatus 2 and the relaying apparatuses 2 is 20 provided with the band control device 100 according to the present invention, it is possible to increase/decrease the number of the physical links which the above-mentioned sub-logical link 82 exclusively used for the object traffic 83 a aggregates or to release the occupation according to the traffic amount of the object traffic 83 a. As mentioned in the above {circle over (1)}-{circle over (4)}, by the embodiment (1), it is possible to assign one or more physical links to the traffic of the specified condition to guarantee the band, and to perform the band variable control of the traffic. Embodiment (2) In case the source end apparatus 1 _ 1 transmits the object traffic 83 _ 2 of the specified condition to the destination end apparatus 1 _ 5 through the relaying apparatuses 2 _ 1 and 2 _ 2 in the network of FIG. 1 D, for example, composed of the end apparatuses 1 and the relaying apparatuses 2 having the band control device 100 of the present invention, the sub-logical link which guarantees the band of the object traffic 83 _ 2 must be established respectively between the source end apparatus 1 _ 1 —the relaying apparatus 2 _ 1 , the relaying apparatus 2 _ 1 —the relaying apparatus 2 _ 2 , and the relaying apparatus—the destination end apparatus 1 _ 5 . The band control device 100 of the present invention in the source end apparatus 1 _ 1 requests the network to establish the sub-logical link for the specified object traffic between the own device 100 to the band control device 100 of the destination end apparatus 1 _ 5 , thereby realizing the establishment of the sub-logical link. Hereinafter, the arrangement of the band control device 100 of the present invention in order to establish the sub-logical link in the network and the operation procedure will be described referring to FIGS. 7 - 10 . Hereinafter, the followings will be described: (1) schematic arrangement of an extended aggregation controller 40 of the band control device 100 according to the present invention shown in FIG. 7 ; (2) schematic arrangement of a shared information table 41 included in the controller 40 in FIG. 8 ; (3) arrangement of an extended LACPDU frame where the prior art LACPDU transmitted/received between the apparatuses is extended in FIG. 9 ; and (4) operation procedure in case where the source end apparatus 1 _ 1 transmits the object traffic 83 _ 2 of the specified condition to the destination end apparatus 1 _ 5 through the relaying apparatuses 2 _ 1 and 2 _ 2 by referring to FIGS. 7 - 9 in the above (1)-(3) in FIG. 10 . FIG. 7 shows an embodiment of the aggregation controller 40 of the band control device 100 in the end apparatus 1 and the relaying apparatus 2 according to the present invention. In the arrangement of the aggregation controller 40 , an extended aggregation controller 40 b and a message controller 45 are added to the prior art controller 40 a. The controller 40 b is composed of the shared information table 41 , a message generator 42 , a message discriminating portion 43 , and a processor 44 which includes a timer 46 . FIG. 8 shows an arrangement of the shared information table 41 , which is composed of “occupation flag”, “request number”, “request band (per single link)”, “request source address (transmitting source address)”, “destination address”, “identifying condition 1”, “condition value 1”, “identifying condition 2”, “condition value 2” . . . , “identification condition m”, and “condition value m” for each sub-logical link. The establishment request of the sub-logical link in the source end apparatus is performed by the extended LACPDU frame in which the prior art LACPDU frame (see FIG. 15 ) is extended as shown in FIG. 9 . Namely, an extended message field of 32 octets is provided in a reserved field of 50 octets in the prior art frame. The extended message field is composed of 1-octet TLV type&equals;“extended distribution”, 1-octet extended distribution length&equals;“32”, 1-octet message type, 6-octet request system address, 6-octet target system address, 1-octet request band, and 16-octet information. The TLV type and the extended distribution length indicate that the extended message is the extended distribution of 32 octets. As for the message type, the setting values “01”, “02”, “03”, “04”, “05”, “06”, “07”, and “8X” (X is 1-7) respectively indicate “request”, “response”, “rejection”, “error (number)”, “error (occupied)”, “request from relaying apparatus”, “release request”, and “message in a single link”. The request system address and the target system address respectively indicate the addresses of the source apparatus and the destination apparatus. Lower three bits of the request band indicate “band per single link”. The setting values “001”, “010”, “011”, and “100” respectively indicate “10 Mbps”, “100 Mbps”, “1 Gbps”, and “10 Gbps”. Upper five bits indicate the link request number of 1-31. The identifying information field is composed of “identifying condition (kind of identifying information)” and “condition value (value of identifying information)”. FIGS. 10A and 10B show an operation procedure in case where the sub-logical link is established from the request source end apparatus 1 _ 1 to the destination end apparatus 1 _ 5 through the relaying apparatuses 2 _ 1 and 2 _ 2 . The arrangement and the connection relationship of the end apparatus 1 _ 1 , the relaying apparatuses 2 _ 1 , 2 _ 2 , and the end apparatus 1 _ 5 are the same as those shown in FIG. 14A except the band control device 100 of the present invention is used as the band control device 100 . It is to be noted that the port 10 and the physical links 80 a and 80 b indicate a plurality of ports 10 and physical links 80 in the same way as the arrangement shown in FIG. 14A . {circle over (1)}: Transmission of Occupation Request Message from end Apparatus 1 _ 1 (see FIG. 10A {circle over (1)}) The end apparatus 1 _ 1 which desires to communicate by establishing the sub-logical link exclusively used for the traffic of the specified condition is supposed to be a request side-end apparatus, and the destination end apparatus 1 _ 5 is supposed to be a response sideend apparatus. In FIG. 10 A, the request side-end apparatus 1 _ 1 determines the “number (request number)” of the physical links which the apparatus desires to occupy by e.g. instructions from an upper layer application, the monitor of the traffic amount, or the like, so that the number is provided to the processor 44 of the controller 40 b. The processor 44 writes, in the shared information table 41 , e.g. “own address (request source address)”&equals;“000:00:0e:14:32:22”, “destination address”&equals;“00:e0:5f:53:22:21”, “request number”&equals;“2”, “band per single link”&equals;“100 Mbps”, “identifying condition”, and “condition value” (“identifying condition 1”&equals;“source MAC address”, “condition value 1”&equals;“00:00:0e:14:32:22”, “identifying condition 2”&equals;“destination MAC address”, and “condition value 2”&equals;“00:e0:5f:53:22:21”, etc), and makes “occupation flag” on. In addition, the processor 44 instructs the message generator 42 to generate the request message. The generator 42 prepares the extended message of the message type&equals;“request” shown in FIG. 9 by referring to “request source address”, “destination address”, “request number”, “band per single link”, “identifying condition”, and “condition value” in the table 41 , so that the extended message is transmitted to the message controller 45 . It is to be noted that the request system address and the target system address in FIG. 9 respectively correspond to the “request source address” and the “destination address”. The message controller 45 composes the LACPDU frame by the extended message and other information to be transmitted to the relaying apparatus 2 _ 1 through any one of the ports 10 which transmits the message. It is to be noted that the transmitting ports 10 may be all of the ports occupied by the sub-logical link. Also, the processor 44 writes, in the “kind of the identifying information” and the “value of the identifying information” of the identifying data table 22 (see FIGS. 2 and 3 ), “identifying condition” and “condition value” (“identifying condition 1” and “condition value 1”, “identifying condition 2” and “condition value 2”) respectively, and notifies the “request number” to the port manager 76 . The port manager 76 sets the occupation ports of the request number to “&compfn;: object traffic port” in the port managing table 77 (see FIGS. 4 and 5 C). The occupation ports are secured one after another based on the priority. It is to be noted that the other data are not notified from the processor 44 but are set by the management tool (not shown). It is also possible to use, for the “identifying condition” and the “condition value”, e.g. information such as an IP header or a TCP header besides the MAC address. It is to be noted that if a bidirectional communication is supposed to be performed, the request side-end apparatus 10 _ 1 does not yet commence the communication of the object traffic at this point since the link on one side from the request side-end apparatus 1 _ 1 to the relaying apparatus 2 _ 1 is occupied, and the communication is commenced when the response message is received from the response side-end apparatus 1 _ 5 . {circle over (2)}: Relay of occupation request message by relaying apparatus 2 _ 1 (see FIG. 10A {circle over (2)}); {circle over (2)}′: Transmission of return occupation request message (see FIG. 10A {circle over (2)}′); and {circle over (2)}″: Transmission of error (number error) message (see FIG. 10A {circle over (2)}″) Hereinafter, the operation in which the relaying apparatus 2 _ 1 relays the occupation request message from the end apparatus 1 _ 1 to the subsequent relaying apparatus 2 _ 2 will be described. In FIG. 10A {circle over (2)}, the message controller 45 of the relaying apparatus 2 _ 1 takes out the occupation request message of the extended portion from the received LACPDU frame to be transmitted to the message discriminating portion 43 . The usual LACPDU frame portion is transmitted to the prior art aggregation controller 40 a, so that the usual aggregation process is performed. The discriminating portion 43 performs a primary process of the request message. Namely, the discriminating portion 43 confirms the “occupation flag” in the shared information table 41 (see FIG. 8 ), takes out the “source address”, the “destination address”, the “request band (band per single link, request number)”, and the “information (identifying condition and condition value)” in case of occupation flag&equals;“off” to be written in the shared information table 41 , so that the occupation flag is switched “on”. Also, the discriminating portion 43 transmits the message type&equals;“request” to the processor 44 . It is to be noted that the process in case of the occupation flag&equals;“on” will be described later referring to “{circle over (7)} upon request from other end apparatus”. Since the message type is “request”, the processor 44 notifies the “occupation request” to the subsequent apparatus. Hereinafter, e.g. the processor 44 of the band control device 100 a in the relaying apparatus 2 _ 1 in the link aggregation group connected to the preceding apparatus (end apparatus 1 _ 1 ) is referred to as the request side-processor 44 , and the processor 44 of the band control device 100 b in the link aggregation group connected to the subsequent apparatus (relaying apparatus 2 _ 2 ) is referred to as the response side-processor 44 , for convenience' sake. While the “request side” and the “response side” are similarly attached to the table 41 , the message generator 42 , the message discriminating portion 43 , and the message controller 45 , they are occasionally omitted when they are self-evident. The response side-processor 44 which has received the notification instructs the response side-message generator 42 to generate the request message. In case of &lsqb;{circle over (1)}: occupation request from the end apparatus 1 _ 1 &rsqb;, the generator 42 generates the request message by the same process to be transmitted to the message controller 45 . The controller 45 transmits the request message to the subsequent relaying apparatus 2 _ 2 from the port 10 which forms the object. Also, the processor 44 writes the same information as in case of &lsqb;{circle over (1)}: occupation request from the end apparatus 1 _ 1 &rsqb; in the identifying data table 22 of the response side-distributor 20 and the port managing table 77 included in the manager 23 . It means that the communication between the request side and the response side-end apparatuses has been set to be performed by the occupied sub-logical link. The request side-processor 44 simultaneously performs the process for securing the return sub-logical link. Namely, in FIG. 10A {circle over (2)}′, the processor 44 notifies port information 90 c for “request number” with a high priority to the port manager 23 based on the “request number” and the priority of the port included in the request message. It is to be noted that as for the priority of the port used at this time, the port with a higher priority set to each apparatus is used so that the same port may be selected between the opposite apparatuses. The port priority information is stored as the internal data of the apparatus. Also, the request side-processor 44 notifies the identifying information 84 to the identifying data table 22 (see FIG. 2 ) for identifying the traffic 83 a which forms the object. In case the request side-address and the response side-address of the MAC address, the IP address, or the like are used, the return link from the response side to the request side must be occupied. Therefore, the identifying information 84 at this time makes the traffic, an object traffic, in which the response side-address and the request side-address are respectively made a source address and a destination address. Thus, the same sub-logical link can be occupied at the time of outgoing (object traffic from the request side to the response side) and returning (object traffic from the response side to the request side). Generally in the relaying apparatus of the network, there are some cases where the band for a single physical link and the number of the links aggregated are different depending on the link aggregation group (logical link). Therefore, it is assumed that there are sections which have a band less than a required band in some relaying apparatus between two end apparatuses. In this case, there is a possibility that the following problems arise: (1) Since the section is occupied by the object traffic, other communication can not be performed; (2) In the communication between two end apparatuses, the section becomes a bottleneck. In order to solve the problems, in FIG. 10A {circle over (2)}″, the request side-processor 44 compares the band of the link aggregation group connected to the subsequent apparatus with the request band by referring to the shared information table 41 (see FIG. 8 ). Since at least one physical link which is not occupied is required for the other communication, the process for decreasing the occupation number is performed in case the condition of “group band”>“request band” is not satisfied. Namely, the request side-processor 44 instructs the message generator 42 to decrease the value of the “request number” in the shared information table 41 to generate an error (number) message. The message generator 42 transmits the generated message to the message controller 45 . The message controller 45 transmits the error (number) message from the port with the lowest priority for the request side to the request source side-end apparatus 1 _ 1 . The port which has received the message is excluded from the object of the occupation. The relaying apparatus or the end apparatus which has received the error (number) message releases the secured link. The relaying apparatus further relays the message to the request side, so that by repeating the relay, the message is transmitted to the end apparatus. {circle over ( 3 )}:Securing return occupation link by response side-end apparatus 1 13 5 (see FIG. 10A {circle over (3)}) {circle over (3)}′:Sending back response message of link securing completion (see FIG. 10A {circle over (3)}′); and {circle over (3)}″:Sending back rejection message In FIG. 10A {circle over (3)}, the discriminating portion 43 of the end apparatus 1 _ 5 performs a primary process of the request message received through the message controller 45 (see &lsqb;{circle over (2)}: relay of the occupation request message by relaying apparatus 2 _ 1 &rsqb;. Furthermore, the discriminating portion 43 transmits the message type&equals;“request” to the processor 44 . The processor 44 secures the ports of the request numbers sequentially from the port with higher priority based on the port information stored as the internal data and the request message, so that the port is notified to the port manager 76 (see FIG. 4 ). The port manager 76 sets the port in the port managing table 77 to secure the sub-logical link of the object traffic 83 . Furthermore, the processor 44 notifies the identifying information (identifying condition and condition value, see FIGS. 8 and 9 ) of the request message to the identifying data table 22 (see FIGS. 2 and 3 ). In the same way as the case of &lsqb;{circle over (2)}′: transmission of the return occupation request message in the relaying apparatus&rsqb;, the traffic is established where the request side address is made a destination address and the response side address is made a transmitting source address. Thus, the return sub-logical link is secured. In addition, the processor 44 instructs the message generator 42 to generate the message in FIG. 10A {circle over (3)}′. The message generator 42 transmits the response message to the request side-end apparatus 1 _ 1 through the message controller 45 by using the return link. Although the number of links according to the occupation request can be secured at the present time, there are some cases where the response side-end apparatus 1 _ 2 does not desire to secure the occupation link for the end apparatus 1 _ 1 for some reason such as the case where priority is given to the occupation from another end apparatus. In order to attend to this case, the end apparatus 1 _ 2 can return the response message (see FIG. 9 ) in which the request number is decreased, so that a part of the request number can be rejected. Furthermore, in case the end apparatus 1 _ 2 can not respond to all of the request number in FIG. 10A {circle over (3)}″, it can return the rejection message to the request side-end apparatus 1 _ 1 . In this case, the occupation can not be performed. {circle over (4)}: Support for a Single Link with a Large Bandwidth As the interval between the relaying apparatuses 2 _ 1 and 2 _ 2 shown in FIG. 1 B, there is a possibility that some parts have only a single physical link 80 of a large band without considering the redundancy in the arrangement of the system. The process in such a case will be described based on the arrangement of FIG. 1B . FIG. 11 shows a network in which the end apparatus 1 and the relaying apparatus 2 are connected with a single physical link 80 . It is supposed that a port 10 a _ 1 connected to the band control device 100 of the present invention is connected to the physical link through a scheduler 60 and a port 10 a _ 2 in the relaying apparatuses 2 _ 1 and 2 _ 2 in FIG. 1B . It is to be noted that the scheduler 60 is included in the band control device 100 . FIG. 12 shows a connection between the distributor 20 and the scheduler 60 shown in FIG. 11 more in detail. The object assignment portion 24 and the non-object assignment portion 25 respectively transmit the object traffic 83 a and the non-object traffic 83 b to the port 10 a _ 1 . The port 10 a _ 1 provides the received traffics 83 a and 83 b to the scheduler 60 . The scheduler 60 transmits the traffics 83 a and 83 b to the port 10 a _ 2 connected to the physical link 80 based on a schedule management signal 98 from the processor 44 (see FIG. 7 ). In FIG. 10A {circle over (4)}, the relaying apparatus 2 _ 1 receives the request message from the end apparatus 1 _ 1 , and secures the return link in the same way as the case &lsqb;{circle over (2)} : Relay of occupation request message by relaying apparatus 2 _ 1 &rsqb;. The response side-processor 44 of the relaying apparatus 2 _ 1 instructs the message generator 42 to generate the request message which does not secure the number, since there is only one physical link 80 to the subsequent relaying apparatus 2 _ 2 . The message generator 42 transmits the generated request message to the relaying apparatus 2 _ 2 . At this time, the processor 44 instructs the scheduler 60 to preferentially process the object traffic which meets the specified condition by the schedule managing signal 98 . The scheduler 60 preferentially transmits the object traffic within the traffic, and processes the non-object traffic in the same way as the usual case. While the relaying apparatus 2 _ 2 which has received the request message not securing the number does not occupy the return link, the request side-processor 44 notifies the scheduler 60 to preferentially process the object traffic in the same way as the relaying apparatus 2 _ 1 . It is to be noted that in case of using a route with a single physical link, a message type is temporarily changed. Namely, the upper 4 bits of the message type in FIG. 9 are changed to “1000&equals;8”, while the lower four bits are not changed. The apparatus which has received the message discriminates the message of a single link by the upper 4 bits, and can recognize the message type by the lower 4 bits. When relaying the message, the relaying apparatus returns the upper bits to “0000” so that the former message type is restored to be transmitted to the subsequent apparatus. {circle over (5)}: Release of Occupied Link (see FIG. 10A {circle over (5)}) When the object traffic communication is completed, it is necessary to release the occupation link and to avoid the state where the band is uselessly occupied. When having completed the transmission of the object traffic using the occupied sub-logical link in the request side-end apparatus 1 _ 1 , for example, the upper layer notifies that the transmission is completed to the processor 44 (see FIG. 7 ). The processor 44 instructs the message generator 42 to generate the link release request message. The message generator 42 generates the release request message in which the message type is made “release request” (see FIG. 9 ) to be transmitted from the occupied ports 10 , so that the occupation of the ports is released. Specifically, the processor 44 makes the occupation flag of the shared information table 41 (see FIGS. 7 and 8 ) “off”, and all of the ports of the port managing table (see FIGS. 4 and 5 C) “&square;” indicating the non-occupation state. In the relaying apparatus 2 _ 1 having received the release request message, the request side-processor 44 confirms the message type&equals;“release request”, and releases the occupation link in the same way as the above. In addition, the request side-processor 44 notifies the response side-processor 44 that there is a release request in order to transmit the release request message to the subsequent relaying apparatus 2 _ 2 . The response side-processor 44 proceeds the generation of the release request message in order to relay the release request message to the relaying apparatus 2 _ 2 , and releases the occupation port on the response side. In case no release request message is transmitted nor relayed for some reason in the above-mentioned procedure, an unnecessary sub-logical link is not released. Therefore, in the relaying apparatuses 2 _ 1 and 2 _ 2 , and the response side-end apparatus 1 _ 2 , the traffic monitor 26 (see FIG. 2 ) monitors the object traffic to provide the traffic amount information 86 to the discriminating portion 72 (see FIG. 4 ) of the manager 23 . The discriminating portion 72 instructs the processor 44 to release the occupation in the absence of object traffic for a fixed period based on the traffic amount information 86 . The processor 44 releases the occupation state. {circle over (6)}: Decreasing Operation of Occupation Number (see FIG. 10A {circle over (6)}) (1) If the physical link is disconnected due to a failure, or (2) if the non-object traffic increases, there are some cases where the number of the physical links of the object traffic must be decreased. Hereinafter, the process in case where the physical link 80 is disconnected between the relaying apparatuses 2 _ 1 and 2 _ 2 in the arrangement of FIG. 1 D and the non-object traffic increases will be described. (1.1) In Case Disconnected Physical Link is Occupation Link In case the physical link 80 _ 10 included in the sub-logical link 82 _ 3 is disconnected for example, the processor 44 (see FIG. 7 ) checks whether or not the substitution link exists in the relaying apparatuses 2 _ 1 and 2 _ 2 which have detected the disconnection in the same process as the case of the usual occupation. In the presence of the substitution link, the processor 44 performs a process of substituting the link for the disconnected link, i.e. a changing process of the port managing table 77 (see FIGS. 4 and 5 C). In the absence of the substituting link, the processor 44 decreases the value of the “request number” in the shared information table 41 (see FIGS. 7 and 8 ) by one. In addition, the processor 44 instructs the message generator 42 to prepare the error (number) message (see FIG. 9 ) for decreasing the number, and to transmit the message to the apparatus (end apparatus 1 _ 1 in case of relaying apparatus 2 _ 1 , and end apparatus 1 _ 2 in case of relaying apparatus 2 _ 2 ) opposite to the side where the disconnection of the message is detected. The end apparatuses 1 _ 1 and 1 _ 2 which have received the error (number) message perform the process for releasing the occupation of the link with the lowest priority. This process is the same as the usual request of the occupation number, and releases the occupation of the link instead of securing the link of the occupation number. (1.2) In Case Disconnected Physical Link is Non-occupation Link In case the physical link 80 _ 12 is disconnected for example, the port manager 76 (see FIG. 4 ) checks whether or not there are any non-occupation link except the disconnected link, by referring to the port managing table 77 , in the relaying apparatuses 2 _ 1 and 2 _ 2 which have detected the disconnection, and instructs the processor 44 to decrease the number of the occupation link in the absence of the other non-occupation links. The process hereafter is the same as (1.1) “the case of no substituting link”. Thus, the number of the occupation link is decreased. (2) In Case Non-object Traffic Increases The traffic monitor 26 (see FIG. 2 ) of each apparatus monitors the non-object traffic 83 b. In case it is discriminated that the traffic amount has exceeded the port available rate for the non-object traffic set in the threshold value table 71 (see FIG. 5 ), the discriminating portion 72 (see FIG. 4 ) confirms the traffic amount of the object traffic 83 a, and confirms whether or not the occupation link number can be decreased from the available rate. In case the link number can be decreased, the port manager 76 (see FIG. 4 ) instructs the processor 44 (see FIG. 7 ) to decrease the number. The process hereafter is the same as the cases (1.1) and (1.2) except that the message is transmitted to both of the request side-end apparatus 1 _ 1 and the response side-end apparatus 1 _ 2 . {circle over (7)}: Upon Request from Other end Apparatus (see FIG. 10B {circle over (7)}) In the present invention, it is possible to establish a plurality of sub-logical links in a single logical link (link aggregation group). Hereinafter, the process performed in case the occupation request is transmitted from another end apparatus on the route occupied between certain end apparatuses will be described referring to FIG. 10B . (1) In Case of Newly Requested Route Being Securable The route can be secured by the same signaling as the usual method. However, in case the route has been already occupied by the request between the other end apparatuses (in case of the occupation flag of the shared information table 41 of FIGS. 7 and 8 &equals;“on”), the sub-logical link condition for the subsequent group is stored in the shared information table 41 . For example, in case the object traffic 83 _ 2 desires to occupy the interval between the end apparatuses 1 _ 4 and 1 _ 8 when the object traffic 83 _ 1 occupies the interval between the end apparatuses 1 _ 1 and 1 _ 5 by the sub-logical links 82 _ 1 , 82 _ 3 , and 82 _ 5 in FIG. 1 D, the interval between the relaying apparatuses 2 _ 1 and 2 _ 2 has already been occupied by the sub-logical link 82 _ 3 . Therefore, the information of another sub-logical link 82 _ 4 for the interval between the end apparatuses 1 _ 4 and 1 _ 8 is held in the shared information table 41 (see FIG. 8 ), so that both of the sub-logical links 82 _ 3 and 82 _ 4 are set in the identifying data table 22 of the relaying apparatuses 2 _ 1 and 2 _ 2 as shown in FIG. 3C . Also, in case only a port of the requested occupation number can be occupied, the same process as the usual sequence shown in FIG. 10A is performed, so that the number which can be occupied is secured. (2) In Case of Newly Requested Route Not Being Securable (see FIG. 10B {circle over (7)}′) The error (occupied) message (see FIG. 9 ) indicating that the route can not be secured is returned. Namely, in FIG. 7 , the processor 44 confirms that the occupation flag of the sub-logical link 82 _ 3 &equals;“on” in the shared information table 41 (see FIG. 8 ), and instructs the message generator 42 to generate the error (occupied) message in case the requested band can not be secured. The generator 42 sends back the generated message to the request source side-end apparatus 1 _ 1 (see FIG. 10B {circle over (7)}′). The end apparatus 1 _ 1 which has received the message stands by for a fixed time, and then again requests the occupation (see FIG. 10B {circle over (7)}″). Hereinafter, the process sequence in case where an object traffic (not shown) desires to occupy the interval between the end apparatuses 1 _ 4 and 1 _ 5 when the object traffic 83 _ 1 occupies the interval between the end apparatuses 1 _ 1 and 1 _ 5 by the sub-logical links 82 _ 1 , 82 _ 3 , and 82 _ 5 will be described referring to FIG. 10B . Firstly, the request message of the occupation number is transmitted to the relaying apparatus 2 _ 2 from the end apparatus 1 _ 4 through the relaying apparatus 2 _ 1 (at step S 1 ). Since the relaying apparatus 2 _ 2 can not establish the sub-logical link in the logical link between its own apparatus and the response side-end apparatuses 1 _ 5 , the error (occupied) message is sent back to the request side-end apparatus 1 _ 4 (at step S 2 ). The end apparatus 1 _ 4 which has received the message stands by for a fixed time based on the timer 46 (see FIG. 7 ) of the processor 44 (at step S 3 ), and then performs the resending process (at step S 4 ). The sequence hereafter is the same as the usual sequence. {circle over (8)}: Decreasing Operation of Occupation Number upon a Plurality of Sub-logical Links Established In case the occupation number of the physical links within the logical link 81 _ 3 is decreased by a failure or the like in FIG. 1 D, the relaying apparatuses 2 _ 1 and 2 _ 2 where a plurality of sub-logical links 82 _ 3 and 82 _ 4 are established in a single logical link 81 _ 3 decrease the occupation number in the sub-logical link with a lower priority determined based on the available rate. The processor 44 (see FIG. 7 ) compares the available rates (priorities) of sub-logical links at the time of decreasing the number. As a result, the number in the sub-logical link with the lowest priority is decreased in the same procedure as &lsqb;{circle over (6)}: decreasing operation of occupation number&rsqb;. As described above, a band control device according to the present invention is arranged such that a distributor distributes a traffic to a sub-logical link into which specified ones of the physical links in the logical link are aggregated so as to meet a specified condition of the traffic. Therefore, it becomes possible to guarantee the band of the traffic. Also, the band control device according to the present invention is arranged such that the physical links of a number corresponding to the traffic amount are assigned to the sub-logical link. Therefore, it becomes possible to perform a band variable control according to the traffic amount. Furthermore, the band control device according to the present invention is arranged such that a message for establishing the sub-logical link is transmitted/received to/from an opposite controller, and the message is relayed to the subsequent apparatus. Therefore, it becomes possible to perform a trunking of establishing the sub-logical link in the network. As a result, the network has a redundant arrangement by the trunking function and more secure network can be provided to the communication or the like of the basic business. Also, in case Ethernet which enables a long distance transmission is used as a network, a band guarantee and a redundancy can be provided to the communication between bases of an intranet or the like by applying the band control device of the present invention to WAN (Wide Area Network) and MAN (Metro Area Network).