JP3786757B2 - Network communication system and communication method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a connectionless network communication system including a plurality of routers and a communication method using the system, and more particularly to a communication system suitable for performing communication with a transmission bandwidth secured between terminals and the communication method thereof. It is about.
[0002]
[Prior art]
An Internet communication system includes an IP (Internet Protocol) as a network layer protocol and provides connectionless packet delivery. In this communication system, processing such as communication path selection is generally performed for each packet to be communicated.
[0003]
In the selection of the communication path, a path that minimizes the cumulative value of cost determined by the length of the transmission path and the like is selected from the communication paths from the transmission side terminal to the reception side terminal. As a route selection method, the method described in “EWDijkstra,“ A note on two problems in connection with graphs, ”Numerische Math., Vol.1, pp.269-271, 1959” (calculation method of EWDijkstra) is known. It has been.
[0004]
Further, in the communication system described above, generally, communication quality is not guaranteed such as securing a transmission bandwidth for each communication flow. For this reason, for example, when communication on the network is congested, problems such as packet discard and a significant increase in transmission delay occur.
[0005]
In order to solve this problem, the Internet Engineering Task Force (IETF) has proposed RSVP (Resource Reservation Protocol). RSVP is a protocol that provides a function of ensuring a transmission bandwidth necessary for communication end-to-end (between terminals). RSVP is positioned above TCP / IP and has a structure independent of routing protocols. For details on RSVP, see “R. Braden, et al.,“ Resource ReSerVation Protocol (RSVP)-Version 1 Functional Specfication, ”Internet Draft, draft-ietf-rsvp-spec-13.txt, Aug. 1996”. It is described in.
[0006]
The operation of the communication system having the RSVP function will be described with reference to FIG. FIG. 19 shows an example in which a plurality of routers relay packets communicated between the transmission side terminal 1 and the reception side terminal 2.
[0007]
In this communication system, a transmitting terminal 1 and a receiving terminal 2 communicate a path message p1 for routing and a reservation message r1 for bandwidth reservation, so that a desired transmission bandwidth can be transmitted to a router on the path. Make a reservation. In this communication system, not only one-to-one communication (unicast) but also one-to-many (multicast) communication is possible.
[0008]
At the start of communication, the transmission side terminal 1 first designates the address of the reception side terminal 2 by the function of the routing protocol and transmits the path message p1 to the connected router 3. This path message is sequentially transferred by the routers 3,..., 4 on one communication path having the lowest cost, and is received by the receiving side terminal 2. At the time of forwarding, each router 3,..., 4 selects the next router on the communication path by referring to the routing table installed in its own router based on the contents of the received path message. Forward the path message to the router. Then, a path for transferring the path message is secured for a certain period of time.
[0009]
The receiving side terminal 2 that has received the path message sends a reservation message r1 back to the transmitting side terminal 1 to request each router 3,..., 4 on the communication path to secure a transmission bandwidth. Each router 3,..., 4 secures the transmission bandwidth requested by the received reservation message for a certain period of time and transfers the reservation message r1. If the transmission band cannot be secured, the reservation message is not transferred and an error message (not shown) is returned to the receiving terminal.
[0010]
When the bandwidth is secured in all the routers 3,..., 4 on the communication path, a reservation message is sent to the transmission side terminal, and the transmission side terminal starts transmission of the data packet d1. In the subsequent communication, the transmission side terminal 1 and the reception side terminal 2 regularly communicate with each other the path message p1 and the reservation message r1, and the path and transmission bandwidth in the routers 3,. Continue to secure
[0011]
[Problems to be solved by the invention]
In the above-described conventional communication system, one path with the lowest cost is selected as a communication path between the transmission side terminal and the reception side terminal, and a bandwidth is reserved for a router on the path. For this reason, if there is a router on the route that cannot secure the bandwidth due to traffic congestion or the like, the reservation is not established, and the transmission side terminal cannot start communication with guaranteed bandwidth.
[0012]
In the network, the demand for large-capacity communication such as moving image communication is increasing and the communication area is expanding. With this, the total number of routers that relay on one communication path, and the transmission paths and routers The amount of communication is increasing. For this reason, in the conventional communication system, it is expected that the probability that the bandwidth reservation will be established will be reduced in the future, and communication with guaranteed bandwidth will become more difficult.
[0013]
In view of the above, an object of the present invention is to provide a communication system and a communication method thereof capable of more reliably performing communication with a desired bandwidth between terminals.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, By connecting a plurality of terminals with a plurality of routers, when communication is performed between one terminal of the plurality of terminals and another terminal, between the one terminal and the other terminal In a network communication system connected to provide a plurality of communication paths, The one terminal is The selected session number without duplication and the communication When doing Band information indicating the required transmission bandwidth and , Multiple path messages with The other Means for sending to the terminal; At least one or more returned from the other terminal Reservation message received Means to do A means for selecting a session number set in one reservation message among the received reservation messages for the communication, and periodically transmitting the path message in which the selected session number is set, and a data packet The other Means to send to the terminal , Have The other terminal is a plurality of terminals transmitted from the one terminal. Receive the pass message Means to do , Based on the bandwidth information If the communication is possible, Said Pass message For each pass message Reservation message with session number and bandwidth information At least one Means for returning, the router comprising: In a communication path between the one terminal and the other terminal, a cumulative value of a cost when communicating from the one terminal to the other terminal via the router as a next transfer destination And means for storing a table registered in association with each other, means for receiving a plurality of the path messages transmitted from the one terminal, and forwarding the plurality of received path messages to different routers, respectively. Means for selecting, means for associating the session number set in the path message with the router that forwarded the path message for a predetermined period, and storing the session number within the predetermined period When the data packet in which the session number is set is received from the one terminal, the data packet is stored in the router stored in association with the session number. Anda means for transferring, the one The terminal The other Acquires the accumulated value of the communication cost in each communication path that can transfer the communication destined for the terminal, and obtains the number of communication paths having the same accumulated value for each accumulated value, and the accumulated value of the cost is the smallest. The path message is transmitted as many times as the number of communication paths, and when no reservation message is received within a certain period of time, the path message is transmitted according to the number of communication paths with the next lowest accumulated cost. The router forwards the path message transmitted from the one terminal in the order of the communication path with the smallest accumulated cost. A network communication system is provided.
[0015]
In such a network communication system, for example, communication with a bandwidth secured is performed by exchanging messages as shown in FIG. That is, in the example of FIG. 1, a plurality of path messages with different session numbers (d1, d2,...) Transmitted by the terminal 11 on the transmission side are transmitted by a plurality of routers 21. The data is transferred individually to the terminal 91 on the receiving side through the formed plurality of communication paths. The reservation message returned by the receiving terminal 91 in response to the pass message is transferred to the sending terminal 11 through the same communication path as the corresponding pass message. During this time, each router secures the transmission bandwidth required by the reservation message, and transfers the reservation message only when it can be secured. In other words, the bandwidth reservation is established in the communication path in which the reservation message is transferred to the terminal 11 on the transmission side. The terminal 11 on the transmission side selects a session number (id1 in the example of FIG. 1) set in one of the received reservation messages, and periodically transmits only the pass message in which the session number is set. . The receiving terminal 91 also periodically transmits a reservation message corresponding to the same path message. Thereby, in the communication path corresponding to the selected session number (id1), the path and bandwidth are maintained, and data packet communication is performed.
[0016]
In such a network communication system, a bandwidth is reserved for a plurality of communication paths between terminals, and one of the reserved communication paths is used for communication, so a desired bandwidth is secured. Communication can be performed more reliably than the above-described conventional example.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
Embodiment 1
FIG. 2 is an example of the configuration of the network communication system according to the embodiment of the present invention. The communication system in FIG. 2 includes a plurality of terminals, a plurality of routers, and a plurality of transmission paths that connect these devices to each other. As the terminal, for example, a computer having a communication function is used.
[0019]
In the communication system of FIG. 2, communication between terminals is performed via one or more routers. One or more communication paths exist between the terminals. For example, between the terminal 11 and the terminal 91, a route via the routers 21, 33, 72, 81, a route via the routers 21, 32, 72, 81, and a route via the routers 21, 31, 71, 81 There are a total of five routes: a route through the routers 21, 34, 44, 74, and 81 and a route through the routers 21, 35, 74, and 81.
[0020]
Further, costs are determined in advance between the routers in FIG. Here, the cost (communication cost) is a constant determined by the length of the transmission path and the like, and generally a smaller one is preferable in communication. Each router transmits a link state packet LSP (Link State Pacet) in which the name of the own router and the cost for each destination are set to other routers. FIG. 3 shows an example of the contents of the link status packet LSP. For example, FIG. 3 (a) shows the contents of the link status packet LSP transmitted by the router 35. The cost between the router 35 and the router 21 is 2, and the cost between the router 74 is 1. Represents. Based on the communicated link state packet LSP, each router generates route information and records it in a routing table formed on a memory in its own router.
[0021]
Here, a method for generating route information will be described.
[0022]
In the EWDijkstra calculation method, which is a conventional route selection method, only the route with the lowest cost is selected. That is, assuming that the cost of the own device is 0, the route that can be reached to the target device and the cumulative value of the cost on the route are obtained, and the obtained route and cost are recorded. When another route that leads to the same target device is found, the route with the lower cost is recorded, and the route with the higher cost is deleted from the record. Then, by repeating this, a route with the minimum cost is obtained. According to this method, for example, when a route is selected from the router 21 in the network of FIG. 2, route information represented by the tree structure shown in FIG. 4 is obtained. In FIG. 4, the value in () represents the cumulative value of the cost from the starting point, and the value in □ represents the code attached to the router.
[0023]
On the other hand, in the communication system of this embodiment, information on all routes is obtained. Specifically, the cost of the own device is set to 0, and the route that can be reached to the target device and the accumulated value of the cost in the route are obtained. Then, the device positioned next to the device itself on the obtained route and the accumulated value of the cost are recorded in the routing table as route information. This is repeated, and the route information is recorded for all routes that can go to the target device.
[0024]
According to this method, for example, when the router 21 is the starting point in the network of FIG. 2, route information represented by the tree structure shown in FIG. 5 is obtained. In FIG. 5, for example, focusing on the route between the routers 21 and 81, it can be seen that there are two routes with a cost of 3, and three routes with a cost of 4. Information when starting from another router can be obtained by the same method as described above.
[0025]
An example of route information recorded in the routing table of each router by this method is shown in FIG. In the figure, for the sake of convenience, only the route information of the route from the terminal 11 to the terminal 91 is shown. Also, both the destination address and the router name are represented by reference numerals attached to the respective devices in FIG. For example, in the routing table of the router 21, as shown in FIG. 6A, the routers 31 and 32 correspond to the addresses of the destination terminal 91 as the next routers of the route with the accumulated cost value of 3. The names of the routers 33, 34, and 35 are registered as the next routers of the route whose name is registered and the cumulative value of cost is 4.
[0026]
Next, the configuration of each device will be described.
[0027]
FIG. 7 shows a configuration example of each terminal.
[0028]
The terminal shown includes a display unit 115 such as a display, a keyboard 116, an external storage device 117 such as a hard disk device, and a computer main body 118. The computer main body 118 includes a CPU, various memories, a communication interface circuit, and the like (not shown). By the processing of the CPU or the like, the computer main body 118 communicates via the transmission path with the communication control unit 101 that performs communication processing based on the RSVP protocol and the like, and the upper application unit 112 that performs processing according to the user's instruction. An input / output interface unit 113 is realized.
[0029]
The terminal communication control unit 101 includes an RSVP configuration unit 111 ′ illustrated in FIG. 8 and a plurality of timers 114. In FIG. 8, the RSVP configuration unit 111 ′ includes an RSVP processing unit 120 that performs RSVP processing, and a traffic processing unit 125 that manages and communicates messages and data packets.
[0030]
The RSVP processing unit 120 includes an application unit 121 having a function of creating a path message, a reservation message, and the like, and an RSVP protocol processing unit 122 that performs protocol processing such as determination of a session number based on the command. In this RSVP protocol processing unit 122, a timer 114 is used for communication state management.
[0031]
The traffic processing unit 125 includes an acceptance determination unit 127 that determines whether or not the requested bandwidth can be secured by the own device, a QOS class determination unit 126 that determines a quality class, and a packet scheduler unit 128 that performs communication control. Consists of.
[0032]
At the start of communication, the RSVP configuration unit 111 ′ of the transmission side terminal transmits a path message for bandwidth reservation. The RSVP configuration unit 111 ′ of the receiving terminal returns a reservation message when communication specified by the sent path message is possible. Note that these processing units 120 and 125 are realized by a process that the communication interface circuit and the CPU cooperate. Although the assignment of processing to the communication interface circuit and the CPU is arbitrary, in this embodiment, the portion where the program processing such as protocol processing is effective is assigned to the CPU.
[0033]
FIG. 9 shows the configuration of each router.
[0034]
The illustrated router includes a communication control unit 101 that performs communication processing based on a protocol and the like, and a plurality of input / output interface units 102 to 107. The communication control unit 101 includes the RSVP configuration unit 101 ′ illustrated in FIG. 10, the routing table 108 in which the information described in FIG. 6 is recorded, and a plurality of timers 109. The input / output interface units 102 to 107 are provided for each transmission path and are individually connected to devices 25 to 30 which are other routers and terminals. Note that the function of the communication control unit 101 can be realized by a hardware circuit or CPU program processing.
[0035]
The RSVP configuration unit 101 ′ of the router also includes an RSVP processing unit 130 and a traffic processing unit 135, as shown in FIG. The RSVP configuration unit 101 ′ of the router realizes the same function as the RSVP configuration unit 111 of the terminal except that the RSVP processing unit 130 includes a routing protocol processing unit 131 instead of the application unit 121. The routing protocol processing unit 131 accesses the routing table and generates a link state packet LSP and route information.
[0036]
In the example of FIG. 9, the devices 25 to 27 are the transmission side and the devices 28 to 30 are the reception side based on the transmission direction of the data packet. In the communication for bandwidth reservation, the router 24 transfers the path message sent from the transmission side to the reception side, and transfers the reservation message sent from the reception side to the transmission side. In this case, as viewed from the router 24, the transmission side devices 25 to 27 belong to the previous transfer source (Previous Hops), and the right side devices 28 to 30 belong to the next transfer destination (next Hops).
[0037]
Here, various messages transmitted in the communication system will be described with reference to FIGS.
[0038]
The message is composed of a header part having the format shown in FIG. 11 and one or a plurality of object parts having the format shown in FIG. Messages are classified into seven types (1 = pass message, 2 = reservation message, 4 = reservation error message, etc.) according to the message type (Msg Type) in the header part. Also, the type and number of object parts constituting the message vary depending on the message type. Each object part consists of header information (Length, Class-Num, C-Type) and object information (Object contents). By the class number (Class-Num) in the header information, the object type (2 = SESSIN , 3 = RSVP_HOP, 5 = Time_Values, etc.). The data length of each object is set to the length (length) in the header information, and the data length of the entire message is set to the RSVP length (RSVP Length) in the header part.
[0039]
FIG. 13 shows the contents of the object part of the pass message, and FIG. 14 shows the contents of the object part of the reservation message. In the figure, [] is a symbol indicating an optional object.
[0040]
In the pass message and the reservation message, a destination address, a protocol ID, a destination port number, and the like are set in the SESSION object. In the RSVP_HOP object, the IP address of the own device is set for each communication direction. That is, the IP address (PHOP) of the previous hop is set in the path message, and the IP address (NHOP) of the next hop is set in the reservation message. In the TIME_VALUES object, a value that specifies the message transmission time interval is set. In the path message, the data packet format is set in the SENDER_TEMPLATE object, and data specifying the traffic characteristics of the data packet is set in the SENDER_TSPEC object. In the reservation message, the STYLE object is set with a value that specifies one of the four methods (fixed filter method (FF), world card filter method, etc.) for securing the bandwidth. For example, when the STYLE object specifies the fixed filter method, the flow_descriptor_list object in FIG. 13 is composed of a FLOWSPEC object in which the required QOS including service class specifications is set and a FILTER_SPEC object in which the sender address is set. .
[0041]
Next, the operation of the communication system will be described with reference to FIG. Here, a case where communication is performed from the terminal 11 to the terminal 91 will be described as an example.
[0042]
FIG. 14 shows an example of a session setup procedure in the present embodiment.
[0043]
At the start of communication, in the terminal 11 that is the transmitting terminal, first, the application unit 121 generates a path message addressed to the receiving terminal 91, presents the SESSION object set therein, and the RSVP protocol processing unit. 122 requests the session number. This object includes a destination address (DestAddress), an IP protocol number (Protocol Id) indicating the type of data flow, a destination port number (DstPort), and the like.
[0044]
In response to the request, the RSVP protocol processing unit 122 determines a plurality (m) of session numbers (id1, id2,..., Idm) so as not to overlap. Then, m pieces of path state information PSB (Path State Block) including the determined session number (session) and the destination address (DestAddress) in the designated object are individually generated and registered in the memory. Further, the RSVP protocol processing unit 122 starts a timer and returns the determined session number to the application unit 121.
[0045]
The application unit 121 duplicates the m path messages, and individually sets the returned m session numbers in each path message. These m path messages are sequentially transmitted to the router 21 as path messages p001, p002,..., P0m1 through the processing of the QOS class determination unit 126 and the packet scheduler unit 128.
[0046]
On the other hand, in the router 21 connected to the transmission side terminal, when the path message is received from the transmission side terminal 11, the RSVP protocol processing unit 132 checks whether or not the corresponding path state information PSB is registered. If the corresponding path status information PSB is not registered, the path status information PSB is newly generated from the setting contents of the path message and registered in the memory. This path state information PSB includes the previous transfer source address, the session number, and the like. Then, the RSVP protocol processing unit 132 starts a timer and maintains the registration of the path state information PSB until a timeout is measured by the timer. Here, the timer performs measurement for a time obtained by adding a predetermined time to the time set in the TIME_VALUES object of the path message.
[0047]
The routing protocol processing unit 131 of the router 21 searches the routing table (FIG. 6A) for the destination address in the received path message and determines one next transfer destination router (next router). At this time, for a path message having the same destination address as that of the already received path message and having a different session number, a different next router is determined. As described above, there are five routes between the terminals 11 and 91, and there are five next routers as seen from the router 21, that is, routers 31, 32, 33, 34, and 35. For this reason, for example, the router 31 is determined for the session number id1, the router 32 for the id2, the router 33 for the id3, the router 34 for the id4, and the router 35 for the id5. The received path messages are transferred to the next router as path messages p002, p022, p042, p062, and p082, respectively, through the processing of the QOS class determination unit 136 and the packet scheduler unit 138.
[0048]
Here, in the router 21 connected to the transmission side terminal, when the total number m of path messages of the same destination is less than or equal to the total number n (5 in this example) of the next routers in all routes reaching the same destination. , M next routers are selected. At this time, for example, the next router on the route having a small accumulated cost value is preferentially determined. Conversely, when m is larger than n, n next routers are selected, and for m−n path messages (p01m...), Error messages (p0m2) are sent to the transmitting side terminal 11, respectively. ...) is returned. Upon receiving this error message (p0m2...), The transmitting side terminal 11 deletes the registration of the corresponding path state information PSB and ends the management of the session.
[0049]
The other routers also perform the same operation as the router 21 when receiving the path message. That is, search and registration of the path state information PSB, determination of the next router (or receiving side terminal), activation of the timer, and transfer of the path message are performed. As a result, n path messages p002, p022, p042, p062, and p082 are transferred as p003 to p005, p023 to p025, p043 to p045, p063 to p066, and p083 to p085, respectively. Is received by the terminal 91.
[0050]
In this way, the path state information PSB is registered and the path is secured in the routers of all the routes from the transmission side terminal 11 to the reception side terminal 91.
[0051]
In the receiving terminal 91 that has received the path message, the RSVP protocol processing unit 122 checks whether the path state information PSB and the reservation state information RSB (Reservation State Block) are registered in the memory. On the other hand, the application unit 121 of the receiving terminal 91 generates a reservation message based on the received setting contents of each path message.
[0052]
When the corresponding path state information PSB and reservation state information RSB do not exist, the RSVP protocol processing unit 122 generates the path state information PSB and the reservation state information RSB based on the settings of the received path message and registers them in the memory. To do. It then starts a timer and keeps its registration until it times out. Here, the reservation state information RSB includes a session number, a next hop address (next hop), a filter spec table (Filter_spec_list), and the like.
[0053]
Furthermore, the RSVP protocol processing unit 122 inquires of the reception determination unit 127 whether or not the bandwidth required for the current communication can be secured. In response to this, the acceptance determination unit 127 determines whether or not the required bandwidth can be secured based on the setting content of the FLOWSPEC object in the reservation message to be transmitted. When the required bandwidth can be secured, the application unit 121 sequentially transmits reservation messages using the IP address (PHOP) of the previous hop set in the corresponding path state information PSB as a transmission destination. The above processing is repeated for each received path message p005, p025, p045, p066, p085, and reservation messages r006, r026, r046, r067, r086 are sequentially transmitted from the receiving side terminal 91.
[0054]
Each router that has received a reservation message also performs processing for searching and registering reservation status information RSB, starting a timer, and securing bandwidth, and when the bandwidth is secured, forwards the reservation message to the router or terminal of the previous transfer source. To do. Here, the previous transfer source router or terminal is determined by the address in the path state information PSB having the same session number. As a result, the reservation message is transferred in the reverse direction through the communication path on which the path message having the same session number is transferred. If the requested bandwidth cannot be secured due to bandwidth reservation by other communication, the router returns an error message to the receiving terminal 91 and ends the management of the session.
[0055]
Thus, the reservation message is transferred to the transmission side terminal 11 only when the bandwidth is secured by all the routers on the route. In other words, in the communication path in which the reservation message is transferred to the transmission side terminal 11, bandwidth reservation is established in all routers, and the requested bandwidth is secured. In this example, bandwidth reservation is established only in the routes of session numbers id1 and id4, and error messages r028, r048, and r088 are returned to the receiving terminal 91 in the routes of session numbers id2, id3, and id5, respectively.
[0056]
When receiving the error message, the receiving side terminal 91 deletes the registration of the corresponding reservation status information RSB and ends the management of the session. In addition, the receiving side terminal 91 checks the registration status of the reservation status information RSB, and updates the registration message corresponding to the reservation status information RSB for which registration is maintained, such as the RSB of session numbers id1 and id4, for refreshing the registration. Send regularly. This transmission is performed, for example, at time intervals set in the TIME_VALUES object.
[0057]
On the other hand, in the transmitting terminal 11 that has received the reservation message, the application unit 121 extracts the session number set in the reservation message. When a plurality of reservation messages having the same destination are received, one of the session numbers is selected. At this time, for example, when the session number (id1 in this example) of the reservation message received first is selected, the route with the smallest transmission delay can be selected. Then, the transmission side terminal 11 transmits the path message p011 in which the selected session id1 is set, and thereafter periodically transmits the path message for refreshing the registration.
[0058]
As described above, the path message and the reservation message are periodically transferred on the communication path corresponding to the session number selected by the transmission side terminal 11. When the path status information PSB corresponding to the received path message has already been registered, the router and the receiving side terminal 91 that have received the path message restart the timer corresponding to the path status information PSB and maintain the registration. Let Similarly, when the reservation state information RSB corresponding to the received reservation message has already been registered, the router and the transmission side terminal 11 that have received the reservation message also restart the timer corresponding to the reservation state information RSB, and Maintain registration. On the other hand, the path message and the reservation message are not transferred on the route corresponding to the session number that has not been selected, and the registration of the corresponding path state information PSB and reservation state information RSB is deleted according to the timer timeout.
[0059]
Then, the application unit 121 of the transmitting terminal 11 generates a data packet addressed to the receiving terminal 91 and starts data communication. This data packet is transmitted through the processing of the QOS class determination unit 126 and the packet scheduler unit 128, and is used as data packets p012 to p014 using the path and bandwidth secured corresponding to the selected session number id1. Then, it is transferred to the receiving side terminal 91.
[0060]
When the transmission of the data packet ends, the application unit 121 of the transmission side terminal 11 ends the transmission of the path message that has been periodically transmitted. As a result, the registration corresponding to the selected session number id1 is also automatically deleted due to timeout, and the management of the session ends.
[0061]
As described above, in the communication system according to the present embodiment, bandwidth reservation by RSVP is performed for a plurality of routes connected to the receiving side terminal, and data transfer is performed using one of the routes for which reservation is established. it can. Accordingly, it is possible to increase the probability that the bandwidth reservation is established, that is, the probability that data communication with a desired bandwidth can be performed, compared to the conventional method of performing the bandwidth reservation with the route with the minimum cost. Further, in this communication system, bandwidth reservation for a plurality of paths can be performed in parallel, so that bandwidth reservation can be established in a short time. Further, this communication system has an advantage that the transmission side terminal 11 does not need to know information on a plurality of routes connected to the destination device.
[0062]
By the way, in the above procedure, the management of the session (id4) that has been established as a bandwidth reservation and has not been selected as a communication target is performed in response to the stop of transmission of the path message. It can also be implemented by sending a release (PathTear) message. A specific example of this procedure will be described with reference to FIG.
[0063]
In FIG. 16, in response to the establishment of the reservation on the routes of session numbers id1 and id4, the transmitting terminal 11 transmits a path message p111 corresponding to the selected id1, while releasing the path corresponding to id4 not selected. Send message p171. The path release message is sequentially transferred to the receiving terminal 91 via the route id4. In the router and receiving side terminal that have received this message, the RSVP protocol processing unit deletes the registration of the corresponding path state information PSB and reservation state information RSB without waiting for the timer to time out. Thereby, all the management of the session corresponding to id4 is completed.
[0064]
According to this procedure, it is possible to quickly release the reserved bandwidth to the router on the route that has been reserved and is not selected as the communication target, reducing the impact on other communications. can do.
[0065]
Embodiment 2
Next, a communication system according to the second embodiment of the present invention will be described.
[0066]
In the communication system according to the second embodiment of the present invention, the session setup procedure is different from that of the first embodiment. In addition, the configuration of the communication system and the like are the same as those described with reference to FIGS. 2 to 10, and the same names and symbols are used in the following description.
[0067]
FIG. 17 shows an example of a session setup procedure in the present embodiment.
[0068]
At the start of communication, in the terminal 11, first, the application unit 121 generates a path message addressed to the terminal 91 on the receiving side, presents the SESSION object set therein, and requests a session number from the RSVP protocol processing unit 122. To do. In response to the request, the RSVP protocol processing unit 122 determines one session number (id1), generates path state information PSB including the determined session number and the destination address in the presented object, and the like in the memory. sign up. Further, the RSVP protocol processing unit 122 starts a timer and returns the determined session number to the application unit 121. The application unit 121 sets the returned session number in the path message, and transmits the path message p201 to the router 21.
[0069]
When the router 21 connected to the transmission side terminal receives a path message from the transmission side terminal 11, the RSVP protocol processing unit 132 checks whether or not the corresponding path state information PSB is registered in the memory. If the corresponding path status information PSB is not registered, the path status information PSB is newly generated from the setting contents of the path message and registered in the memory. Then, a timer is started and the registration of the path state information PSB is maintained until a timeout occurs. The routing protocol processing unit 131 searches the routing table (FIG. 6A) for the destination address in the received path message and determines one next router. At this time, for a path message having the same destination address as that of the already received path message and having a different session number, a different next router is determined. Note that a router on a route having a small accumulated cost value may be preferentially selected. Then, the routing protocol processing unit 131 transmits a path message to the determined next router (router 31).
[0070]
When the other router receives the path message, it registers the path status information PSB, determines the next router (or receiving side terminal), and transfers the path message, similarly to the router 21 described above. As a result, the path message p201 is transferred as p202 to p205 and received by the receiving terminal 91.
[0071]
In the receiving terminal 91 that has received the path message, the RSVP protocol processing unit 122 checks whether the path state information PSB and the reservation state information RSB are registered. On the other hand, the application unit 121 of the receiving terminal 91 generates a reservation message based on the received setting contents of each path message. When the corresponding path state information PSB and reservation state information RSB do not exist, the RSVP protocol processing unit 122 generates the path state information PSB and the reservation state information RSB based on the settings of the received path message and registers them in the memory. To do. It then starts a timer and keeps registration until it times out. Further, the RSVP protocol processing unit 122 inquires of the reception determination unit 127 whether or not the bandwidth required for the current communication can be secured. When the required bandwidth can be secured, the application unit 121 transmits the reservation message r206 with the previous hop IP address (PHOP) set in the corresponding path state information PSB as the transmission destination. In addition, the receiving side terminal 91 periodically transmits a reservation message corresponding to the reservation state information RSB for which registration is maintained for refreshing the registration.
[0072]
Each router that has received the reservation message also performs generation and registration of the reservation status information RSB and processing for securing the bandwidth, and when the bandwidth is secured, the reservation message is transferred to the router or terminal of the previous transfer source. As a result, the reservation message is transferred in the reverse direction through the communication path on which the path message having the same session number is transferred. If the requested bandwidth cannot be secured, the router returns an error message to the receiving terminal 91 and ends the management of the session. In this example, the router 71 cannot secure the bandwidth for the reservation message r206 and returns an error message. When receiving the error message, the receiving side terminal 91 deletes the registration of the corresponding reservation status information RSB and ends the management of the session.
[0073]
On the other hand, when the timer has timed out without receiving a reservation message corresponding to the transmitted pass message, the transmitting terminal 11 repeats the above process and transmits a pass message p221 in which a new session number is set. . The path message p221 is transferred from the router 21 to the next router 31, and is transferred to the receiving terminal 91 through a communication path different from that of the first path message p201.
[0074]
In this example, the reservation message corresponding to the pass message p221 is not transferred to the transmission side terminal 11, and the reservation message r251 corresponding to the third pass message p241 is received by the transmission side terminal 11 for the first time. In the sending terminal 11 that has received the reservation message, the application unit 121 extracts the session number (id3 in this example) set in the reservation message. Then, a path message p253 in which the extracted session id3 is set is transmitted, and thereafter the path message is periodically transmitted for refreshing registration.
[0075]
As described above, the path message and the reservation message are periodically transferred on the communication path corresponding to the session number id3, and the transmission side terminal 11, the router, and the reception side terminal 91 on the same path restart the timer by restarting the timer. Registration of the path state information PSB and the reservation state information RSB is maintained.
[0076]
Then, the application unit 121 of the transmitting terminal 11 generates a data packet addressed to the receiving terminal 91 and starts data communication. This data packet is transferred to the receiving side terminal 91 using the path and bandwidth secured corresponding to the session number id3. When the transmission of the data packet ends, the application unit 121 of the transmission side terminal 11 ends the transmission of the path message, whereby the management of the same session on the route is completed. Note that session management may be immediately terminated by transmission of a path release message at the transmitting terminal 11.
[0077]
As described above, in the communication system according to the present embodiment, for a plurality of routes that can relay communication, a path and a bandwidth are secured for each route. The influence on the communication can be further reduced.
[0078]
Embodiment 3
Next, a communication system according to the third embodiment of the present invention will be described.
[0079]
The communication system according to this embodiment also differs from the above two embodiments in the session setup procedure. In addition, the configuration of the communication system and the like are the same as those described with reference to FIGS. 2 to 9, and the same names and symbols are used in the following description.
[0080]
FIG. 17 shows an example of a session setup procedure in the present embodiment.
[0081]
Each terminal of this embodiment obtains route information of a routing table in a connected router by communication. In the transmission side terminal 11, there are five communication paths from the terminal 91 to the terminal 11 from the path information obtained from the router 21 (see FIG. 6A), and among these, a path with a cumulative cost value of 3 exists. It can be seen that there are three routes with two and a cumulative cost value of four.
[0082]
At the start of communication, in the transmission side terminal 11, first, the application unit 121 generates a path message addressed to the reception side terminal 91, presents the SESSION object set therein, and sends the session number to the RSVP protocol processing unit 122. Request. At this time, the number p (2 in this example) of the route having the minimum accumulated cost is also presented. Upon receiving the request, the RSVP protocol processing unit 122 determines p session numbers (id1, id2) so as not to overlap. Then, p pieces of path state information PSB including the determined session number and the destination address in the designated object are individually registered, and the timer is started. The application unit 121 duplicates the p path messages, and individually sets the determined p session numbers in each path message. Then, the set path messages p301 and p321 are sequentially transmitted to the router 21.
[0083]
When the router 21 receives the path message from the transmission side terminal 11, the RSVP protocol processing unit 132 checks whether or not the corresponding path state information PSB is registered, and the corresponding path state information PSB is not registered. Registers the path state information PSB in the memory. Then, a timer is started, and the registration of the path state information PSB is maintained until a timeout occurs. The routing protocol processing unit 131 searches the routing table (FIG. 6A) for the destination address in the received path message and determines one next transfer destination router (next router). At this time, for a path message having the same destination address as that of the already received path message and having a different session number, a different next router is determined. In this example, the router 31 is determined for the session number id1 and the router 32 is determined for the id2. Each received path message is transferred to the next router as path messages p302 and p322.
[0084]
When the other router receives the path message, it also registers the path status information PSB, determines the next router (or receiving side terminal), and transfers the path message in the same manner as the router 21 described above. As a result, the p path messages p302 and p322 become p303 to p305 and p323 to p325, respectively, are transferred along different paths, and are received by the terminal 91 which is a receiving terminal.
[0085]
In the receiving terminal 91 that has received the path message, the RSVP protocol processing unit 122 checks whether the path state information PSB and the reservation state information RSB are registered. On the other hand, the application unit 121 of the receiving terminal 91 generates a reservation message based on the setting contents of each received path message. When the corresponding path state information PSB and reservation state information RSB do not exist, the RSVP protocol processing unit 122 registers the path state information PSB and reservation state information RSB based on the settings of the received path message, and starts a timer. And keep the registration until it times out. Furthermore, the RSVP protocol processing unit 122 inquires of the reception determination unit 127 whether or not the bandwidth required for the current communication can be secured. When the required bandwidth can be secured, the application unit 121 sequentially transmits reservation messages using the IP address (PHOP) of the previous hop set in the corresponding path state information PSB as a transmission destination.
[0086]
Each router that has received the reservation message also performs generation and registration of reservation status information RSB and processing for bandwidth reservation, and when the bandwidth is secured, forwards the reservation message to the pre-transfer source router or sender terminal. . As a result, the reservation message is transferred in the reverse direction through the communication path on which the path message having the same session number is transferred. If the requested bandwidth cannot be secured, the router returns an error message to the receiving terminal 91 and ends the management of the session.
[0087]
When receiving the error message, the receiving side terminal 91 deletes the registration of the corresponding reservation status information RSB and ends the management of the session. Further, the receiving side terminal 91 checks the registration state of the reservation state information RSB, and periodically transmits a reservation message corresponding to the reservation state information RSB for which registration is maintained, for refreshing the registration. In this example, an error message is returned to the receiving side terminal 91 for each reservation message corresponding to the session numbers id1 and id2.
[0088]
In the terminal 11 on the transmission side, when the timer has timed out in a state where the reservation message corresponding to the transmitted path message is not received, the number of routes with the next smallest accumulated cost (3 in this example) is set as p. The above process is repeated, and a path message in which new session numbers (id3, id4, id5) are set is transmitted. The path messages p341, p361, and p381 thus transmitted are transferred from the router 21 to the next routers 33, 34, and 35 that have not been selected, and are transferred to the receiving terminal 91 through different communication paths.
[0089]
On the other hand, in the transmitting terminal 11 that has received the reservation message, the application unit 121 extracts the session number set in the reservation message. When a plurality of reservation messages having the same destination are received, one of the session numbers is selected. At this time, for example, when the session number (id3 in this example) of the reservation message received first is selected, the route with the smallest transmission delay can be selected. Then, the transmission side terminal 11 transmits the path message p353 in which the selected session id3 is set, and thereafter periodically transmits the path message for refreshing the registration.
[0090]
As described above, the path message and the reservation message are periodically transferred on the communication path corresponding to the session number id3, and the transmission side terminal 11, the router, and the reception side terminal 91 on the same path restart the timer by restarting the timer. Registration of the path state information PSB and the reservation state information RSB is maintained.
[0091]
Then, the application unit 121 of the transmitting terminal 11 generates a data packet addressed to the receiving terminal 91 and starts data communication. This data packet is transferred to the receiving side terminal 91 using the path and bandwidth secured corresponding to the session number id3. When the transmission of the data packet ends, the application unit 121 of the transmission side terminal 11 ends the transmission of the path message, whereby the management of the same session on the route is completed.
[0092]
It should be noted that the transmission of the path release message at the transmitting terminal 11 may immediately terminate the management of the session used for data communication or the session for which the bandwidth reservation has been established but has not been selected.
[0093]
As described above, in the communication system according to the present embodiment, a plurality of routes capable of relaying communication are grouped, and in order to secure a path and a band for each group, other systems in the system are compared with the first embodiment. In addition to reducing the influence on communication, it is possible to shorten the time required to establish a bandwidth reservation with respect to the second embodiment.
[0094]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a communication system and a communication method for enabling communication with a desired bandwidth secured between terminals more reliably.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a session setup procedure in the present invention.
FIG. 2 is a diagram showing an example of a network for explaining an embodiment of the present invention.
FIG. 3 is an example of a link state packet in the network of FIG. 2;
FIG. 4 shows an example of a tree structure representing route information obtained by a conventional method.
FIG. 5 shows an example of a tree structure representing path information obtained based on FIG. 2 according to the present invention.
6 is an example of route information in the routing table of each router in FIG. 2;
FIG. 7 is a block diagram illustrating a configuration example of a terminal.
FIG. 8 is a diagram illustrating a configuration example of a communication control unit of a terminal.
FIG. 9 is a block diagram illustrating a configuration example of a router.
FIG. 10 is a diagram illustrating a configuration example of a communication control unit of a router.
FIG. 11 is a format diagram of a header part of a message packet.
FIG. 12 is a format diagram of an object part of a message packet.
FIG. 13 is a configuration diagram of a path message.
FIG. 14 is a configuration diagram of a reservation message.
FIG. 15 is a diagram showing an example of a session setup procedure in the first embodiment.
FIG. 16 is a view showing another example of the session setup procedure.
FIG. 17 is a diagram showing an example of a session setup procedure in the second embodiment.
FIG. 18 is a diagram showing an example of a session setup procedure in the third embodiment.
FIG. 19 is an explanatory diagram of a conventional RSVP session setup procedure.
[Explanation of symbols]
11, 12, 13, 14, 15, 91, 92, 93 ... terminal
21, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 44, 71, 72, 74, 81, 3m ... router
51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 ... transmission path
p001 to p005, p021 to p025, p041 to p045, p061 to p081, p0m1... path message
p0m2 Path error message
r006 to r010, r026, r027, r046, r047, r067 to r070, r086, r087 ... reservation message
r028, r029, r048, r049, r088, r089 ... reservation error message
p011, r018, r071 ... refresh
r072, r019 ... timeout
p012, p013, p014 ... Data packets
p101 ... pass message, p171 ... pass blocking message
p112, p113, p114 ... data packets
r119 ... timeout
p201-p205 ... Pass message
r206, r207 ... Reservation message
r208, r209 ... Reservation error message
p221, p222 ... pass message,
r226 ... Reservation message
r227 ... Reservation error message
p241-p245 ... pass message
r246-r251 ... Reservation message
r252 ... reservation message, p253 ... pass message,
p254 ... Data packet
r254 ... timeout
p301-p305, p321-p325 ... pass message
r306, r307, r326, r327 ... reservation message
r308, r309, r328, r329 ... reservation error message
p341 to p345, p361 to p366, p381 to p385 ... pass message
r346-r350, r367-371 ... Reservation message
r386, r387 ... Reservation message
r388, r389 ... Reservation error message
r351, r352 ... Reservation message
r372, r376 ... timeout
p353 ・ ・ ・ Pass message
p354, p355 ... Data packet
111 '... RSVP component of the terminal
101 ′ ・ ・ ・ RSVP component of router
120 ... RSVP processing part of the terminal
130: RSVP processing part of router
125 ... Traffic processing unit of terminal
121 ... Application section
131: Routing protocol processing unit
122, 132... RSVP protocol processor
126, 136 ... QOS class determination part
127, 137... Reception determination unit
128, 138 ... Packet scheduler section
102 to 107 ... I / O interface section

Claims (3)

By connecting a plurality of terminals with a plurality of routers, when communication is performed between one terminal of the plurality of terminals and another terminal, between the one terminal and the other terminal In a network communication system connected to provide a plurality of communication paths,
The one terminal includes a session number chosen without overlapping, a plurality of paths message set and a bandwidth information indicating a transmission bandwidth required when performing the communication, it transmits the control information to the other terminal Means for receiving at least one reservation message returned from the other terminal, and means for selecting a session number set in one reservation message among the received reservation messages for the communication When having sends the path message set the session number chosen regularly, means for transmitting the data packets addressed to the second terminal, and
The second terminal includes means for receiving a plurality of said path message sent from the one terminal, if possible is the communication based on the bandwidth information for each of the path message, in the path message session Means for returning at least one reservation message in which a number and bandwidth information are set,
In the communication path between the one terminal and the other terminal, the router communicates with the router serving as the next transfer destination from the one terminal to the other terminal via the router. A means for storing a table in which accumulated values of costs are associated with each other, a means for receiving a plurality of the path messages transmitted from the one terminal, and a plurality of the received path messages. Means for selecting to forward to a different router; means for associating the session number set in the path message with the router that forwarded the path message for a predetermined period; and within the predetermined period When the data packet in which the stored session number is set is received from the one terminal, the stored rule is related to the session number. A means for transferring the data packet to the data, and
The one terminal has means for obtaining a cumulative value of communication costs in each communication path capable of transferring communication destined for the other terminal, and obtaining the number of communication paths having the same cumulative value for each cumulative value. Then, the path message is transmitted by the number of communication routes having the smallest accumulated cost value, and the reservation message is not received within a certain time, and the number of communication routes having the next smallest accumulated cost value is have line transmission of the path message,
The router forwards the path message transmitted from the one terminal in the order of communication paths with a small cumulative cost value;
A network communication system. The network communication system according to claim 1, wherein
The one terminal selects a session number set in the reservation message received first for the communication;
A network communication system. By connecting a plurality of terminals with a plurality of routers, when communication is performed between one terminal of the plurality of terminals and another terminal, between the one terminal and the other terminal A network communication system that is connected so that a plurality of communication paths are provided, and a communication method for performing communication in which bandwidth is secured,
The one terminal includes a session number chosen without overlapping, a plurality of paths message set and a bandwidth information indicating a transmission bandwidth required when performing the communication, it transmits the control information to the other terminal step for selecting the stroke, the stroke of receiving at least one reservation message sent back from said another terminal, the session number is set to one reservation message of the received reservation message for the communication When having sends the path message set the session number chosen periodically, the step of transmitting a data packet addressed to the other terminal, and
It said other terminal includes a step of receiving a plurality of said path message sent from the one terminal, if possible is the communication based on the bandwidth information for each of the path message, in the path message session Returning at least one reservation message in which a number and bandwidth information are set, and
In the communication path between the one terminal and the other terminal, the router communicates with the router serving as the next transfer destination from the one terminal to the other terminal via the router. A process of storing a registered table in association with a cumulative value of costs, a process of receiving a plurality of the path messages transmitted from the one terminal, and a plurality of the received path messages. A step of selecting to transfer to a different router, a step of storing the session number set in the path message and the router that has transferred the path message for a predetermined period, and within the predetermined period , when receiving the data packets the session number stored is set from the one terminal, said Le being stored in association with the session number It has a step of transferring the data packet to the data, and
The one terminal has a process of acquiring a cumulative value of communication costs in each communication path capable of transferring communication destined for the other terminal, and obtaining the number of communication paths having the same cumulative value for each cumulative value. Then, the path message is transmitted by the number of communication routes having the smallest accumulated cost value, and the reservation message is not received within a certain time, and the number of communication routes having the next smallest accumulated cost value is Send a pass message,
The router forwards the path message transmitted from the one terminal in the order of communication paths with a small cumulative cost value;
A communication method characterized by the above.

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