JP2001094606A - Path calculation method and path control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relieve a processing load on a router attended with its path calculation that is placed in a large-scale network system where many packet transfer paths per one router are in existence. SOLUTION: The router acquires a connection configuration (map) of a network system 10 by executing a routing protocol, calculates a least routing path based on the acquired map and a limit value of a preset hop number (number of transfer paths for a packet) and stores a cross-referencing list between a transfer destination on the calculated least routing path and a destination of the packet to a path control table. on the other hand, when the router receives a packet, the router transfers the received packet to a transfer destination in the cross-referencing list when the destination of the received packet is coincident with a destination in the path control table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network system comprising a network and a plurality of routers connected to the network and transferring packets. A route calculation method for calculating a transfer route to a packet destination based on a map indicating a connection configuration of a network system obtained by exchanging packets with each other, and controlling transfer of a packet to a route determined by the route calculation method Related to a route control system.

[0002]

2. Description of the Related Art OSPF (Open) is used as a method for calculating the shortest path of a packet transferred in a network system.
Shortest Path First: “OSPF
version 2 "J. Moy, RFC1583, Ma
rch 1994. ). This OSP
The path calculation method used in the link state type routing protocol F will be described with reference to FIG.

FIG. 14 is a diagram showing an example of the arrangement of routers 11 to 14 indicating a packet transfer destination in a network system. In FIG. 14, the distance between the router 11 and the router 12 is 20, and the distance between the router 11 and the router 13 is 50. The distance between the router 12 and the router 13 is 10, and the distance between the router 12 and the router 14 is 30. Further, the distance between the router 13 and the router 14 is 10.

[0004] In the 0SPF, the shortest route for all destinations of the network system is calculated based on the map showing the connection configuration of the entire network system shown in FIG. 14 obtained by executing the routing protocol. Each router calculates the shortest path for each destination using the OSPF, and stores the calculated shortest path destination in a memory as the next hop as the next transfer destination in association with the packet destination. Then, when the router receives the data transfer unit which is the minimum unit of the packet,
When the destination included in the header matches the destination stored in the memory, the data transfer unit is transferred to the corresponding next hop. Conventionally, the data transfer unit is delivered to the destination of the packet by the shortest path by hop-by-hop in which the transfer of the packet to the next transfer destination based on the calculation result of the shortest path is sequentially performed for each router.

An example of a conventional packet transfer based on route calculation will be described more specifically with reference to FIG. In the example of FIG. 14, the router 11 that has received the packet data transfer unit
Is an example in which the packet is delivered to the router 14 which is the destination of the packet. In this case, the router 11 transfers the received data transfer unit to the router 12, which is the next hop, because the route calculated as a result of the 0 SPF in advance is shorter in the distance 20 of the router 12 than in the distance 50 of the router 13. When the router 12 receives the data transfer unit from the router 11, the route calculated in advance by the 0 SPF is shorter in the distance 10 of the router 13 than in the distance 30 of the router 14. Transfer to a certain router 13. When receiving the data transfer unit from the router 12, the router 13 transfers the received data transfer unit to the router 14 because the destination of the packet is the router 14.

[0006]

When the method of calculating the shortest path using the OSPF by each router constituting the network system is applied to a large-scale network system, there are many packet transfer paths per router. Therefore, there is a problem that a large load due to the route calculation is applied to the router. This causes a problem that the time required for updating the route becomes longer. Further, when a router arranged in a large-scale network system simultaneously performs a route control process based on the shortest route calculation and a packet transfer control process, it takes time for the route control process, so that the packet transfer process is delayed. However, there is also a problem that packet transfer is delayed.

Accordingly, an object of the present invention is to reduce the processing load involved in the route calculation of a router when the router that performs the route calculation is applied to a large-scale network system having a large number of packet transfer paths per router. And

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for routing a router in a network system comprising a plurality of networks and a plurality of routers connected to the network and transferring packets. A step of acquiring a map including a connection configuration between the network and the router in the network system and a communication cost between the routers by executing the protocol, and setting a limit value of the number of hops indicating the number of transfer paths of the packet in the router; A router calculating a shortest route indicating a route having the lowest communication cost among the packet transfer routes based on the acquired map and a set limit value of the number of hops. Also, the router
By executing the routing protocol, a map including the connection configuration between the network and the router in the network system and the communication cost between the routers is obtained, and based on the obtained map and a preset limit value of the number of hops, the communication cost of the most is reduced. The shortest route which is a cheap route is calculated, and the calculated transfer destination on the shortest route is associated with the destination of the packet and stored in the route control table (route control table), while the destination of the received packet is the destination of the route control table. If it matches, the received packet is transferred to the corresponding transfer destination.

[0009] When transmitting a new packet to the network system, the router records an allowable limit value of the number of hops before the packet is transferred to the destination in a hop number limit field of the packet. When the transfer is performed, the limit value of the hop number limit field of the received packet is reduced by one and the received packet is transferred. Further, the router acquires the map of the network system, calculates the shortest route indicating the route with the lowest communication cost based on the obtained map and each preset limit value of the number of hops, and calculates the shortest route on the calculated route. The transfer destination of the packet and the destination of the packet are stored in a plurality of routing tables for each limit value of the number of hops, and when a new packet is transmitted to the network system, the hop number limit value is set in the hop number limit field. When forwarding a received packet after recording it, search the routing control table according to the limit value of the number of hops recorded in the received packet, and find the transfer destination corresponding to the destination of the received packet in the searched routing control table. Then, the limit value of the hop number limit field of the received packet is reduced by one and the received packet is transferred to the transfer destination.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram to which a route calculation method according to the present invention is applied. In FIG. 1, routers 11 to 14 transfer packets. The route calculation method of the present invention includes:
A limit value of the number of hops indicating the number of routes to the destination of the packet is set in advance for all the routers 11 to 14 on the network system. Then, each of the routers 11 to 14 calculates the shortest path that satisfies the set hop number limit value with respect to the map indicating the connection configuration of the network system obtained by executing the routing protocol. This route calculation can be executed by the following algorithm.

Here, n is the number of nodes (the number of routers), m is the number of links (the number of routers directly connected to the router),
Assuming that k is a hop number limit value, s is a node (router) that executes route calculation, and d (u, v) is a distance of a link (u, v) connected to the node s, the algorithm in step ST1 f0 (s), f0 (v) = {, v}
, s, and i = 1, 2,..., k in step ST2, and the following calculation is repeated k times. That is, for each link (u, v) connected to the node s, fi (v) = min ｛fi-1 (v), fi-1 (u) + d
The operation of (u, v)｝ is repeatedly executed from i = 1 to i = k. Here, fi (v) represents the length of the shortest path from the node s to the node v within the hop number i.

Each of the routers 11 to 14 transfers data to the destination of the packet in the shortest route by hop-by-hop transfer in which the data transfer unit, which is the minimum unit of the packet, is sequentially transferred to the route calculated by such a route calculation method. Units are delivered. Here, the calculation time of the Dijkstra method using the heap, which is the shortest path algorithm conventionally used, is O (m * logn) (however,
Let n be the number of nodes and m be the number of links when the map is represented by a graph: “FORTRAN77 Optimization Programming”, Toshihide Ibaraki, Masao Fukushima, Iwanami Shoten, 1991. ).
On the other hand, the calculation time of the algorithm for calculating the shortest path satisfying the hop number limit value, which is the path calculation method of the present invention, does not exceed O (m * k) (where k is the hop number limit value). Therefore, when the hop number limit value can be set smaller than the number of nodes, the processing load required for the route calculation can be reduced by employing the route calculation method of the present invention. As a result, delay in updating the route and delay in packet transfer can be prevented.

Hereinafter, the present invention will be described more specifically with reference to FIGS. FIG. 2 is a block diagram showing a physical configuration of a network system to which the route calculation method according to the present invention is applied. In FIG. 2, routers 11 to 15 are routers having a network client switching function. These routers 11 to 15 are connected via networks 21 to 26 shown in FIG. 1, and a network system 10 is configured as a whole.

FIG. 3 is a diagram showing a functional configuration of the network system 10. As shown in FIG. In FIG. 3, routers 11-1
5 is a path control function unit 31 and a transfer control function unit 3
3 and an in-device data transfer function unit 32. Here, the path control function unit 31 is a device data transfer function unit 32
Can be exchanged with the data of the transfer control function unit 33. Also, the transfer control function unit 33 of each router
Can exchange data with each other by the transfer function of the network data transfer function unit 41 in the networks 21 to 26. Further, the route control function unit 31 of each router
Can exchange data with the route control function unit 31 of the adjacent router through the network by the data transfer function unit 32, the transfer control function unit 33, and the data transfer function unit 41 of the network in the router.

Each of the routers 11 to 15 has a network layer address (Network Layer Address: RID # 1 to RID # 5) shown in FIG.
NLA). Also, the networks 21 to 26 correspond to NID # 1 to NID shown in FIG.
It is specified by the network layer address # 6. Also, Cost # 1-2 and Cos shown in FIG.
t # 1-3, Cost # 2-3, Cost # 2-4, C
ost # 3-4 and Cost # 4-5 are communication costs set between adjacent routers, and are respectively between router 11 and router 12, between router 11 and router 13, between router 12 and router 13, and between Between router 12 and router 14,
Between router 13 and router 14, and between router 14 and router 1
5 shows the communication cost between the five.

Further, the route control function unit 31 of each router has a hop number limit value described later as an attribute value of the route control function. The hop number limit value is set to a value determined by the network administrator to be appropriate from the connection configuration of the network system. In addition, the hop number limit value may be calculated automatically by calculating the diameter of the network system in order to secure packet reachability, and based on the calculated value.

FIG. 4 is a flowchart showing the processing operation of the router. The processing operation of the router will be described with reference to the flowchart of FIG. 4 and FIGS. The route control function unit 31 of the router first executes a link state acquisition process in step S1. In this link state acquisition processing, the link state, which is the NIA of the network system to which each router is directly connected, and the communication cost corresponding thereto are acquired. FIG. 5 shows a specific example of the link state acquired by the router 11 and the corresponding communication cost. Next, in step S2, a link state advertisement process is executed. In this link state advertisement processing, the route control function unit 31 of each router utilizes data exchange with an adjacent router.
Then, the link state and the corresponding communication cost acquired in step (1) are notified to the routing control units 31 of all the other routers. As a result, a map of the network system 10 is created in each router, and as a result, the route control function units 31 of all routers can have maps of the network system 10. FIG. 6 shows a specific example of a map of the network system 10 created by the route control function unit 31 of each router, and is schematically shown using an effective graph. Note that “0” shown in FIG. 6 indicates that the communication cost during this period is zero.

Next, in step S3, a route is calculated based on this map. That is, a route for transferring the packet to the destination indicated by the network layer address NLA in the network system 10 is obtained. Then, based on the obtained route, a route control table (route control table) to be described later is created, and the created route control table is notified to the transfer control function unit 33 by the data transfer function unit 32 in the router.
The transfer control function unit 33 of each router determines the next hop (next transfer destination) that is the destination to actually send the packet with reference to the created routing control table. Hereinafter, first and second embodiments of a network system to which the above-described route calculation method of the present invention is applied will be described.

(First Embodiment) In the first embodiment, each of the routers 11 to 15 calculates the shortest path satisfying the hop number limit set for itself. The routers 11 to 15 create a route control table having a correspondence between the destination address and the calculated next hop of the route, and notify the transfer control function unit 33 of the route control table. In this embodiment, a packet 7 including a destination address field 7A in the header as shown in FIG. 7A is used as a data transfer unit which is the minimum unit of the packet. The transfer control function unit 33 retrieves the routing control table based on the destination in the destination address field 7A of the packet 7 and acquires the next hop. Then, the packet 7 is transferred to the next hop. The transfer control function of the transfer connection function unit 33 is performed by each of the routers 11 to 1.
It works autonomously at 5 and forwards the packet 7 hop-by-hop to the destination indicated by the destination address in the destination address field 7A. In the present embodiment, a path (packet transfer path) to be followed when the packet 7 is actually transferred.
Does not always match the route calculated by the router that sent the packet 7, as shown in the sequence diagram of FIG.

Next, in the network system shown in FIG. 2 and FIG.
st # 1-2 = 100, Cost # 1-3 = 20, Co
st # 2-3 = 10, Cost # 2-4 = 20, Cos
FIGS. 8 and 9 show specific examples of the operation when t # 3-4 = 40, Cost # 4-5 = 30, and the hop number limit value is set to 3. FIG. 8 is created based on the route (that is, the shortest route) calculated so that each of the routers 11 to 15 has the lowest communication cost based on the communication cost and the hop number limit value 3 set as described above. It is a routing control table. Here, FIG. 8A shows the routing control table 1A of the router 11 created by the router 11, and FIG.
2 is a routing control table 2A of the router 12 created by the router 2. FIG. 8C is a routing control table 3A of the router 13 created by the router 13, and FIG. 8D is a routing control table 4A of the router 14 created by the router 14. FIG. 8E is a routing control table 5A of the router 15 created by the router 15. In FIG. 8, a minus sign indicates that the destination and the next hop (the next transfer destination) are directly connected.

FIG. 9 shows a sequence when a packet is transmitted from the router 11 to the router 15. The packet transfer operation will be described with reference to the routing table of FIG. 8 and the sequence diagram of FIG. The packet 7 is, as shown in FIG. 9, the router 11 → the router 13 → the router 12 → the router 14.
→ Take the transfer route of router 15. When transferring the packet 7, each of the routers 11 to 14 performs the following processing.

That is, when the router 11 receives the packet of the router 15 as the destination, the router 11 has its own routing control table 1A based on the destination address RID # 5 of the packet at the time of FIG.
To obtain RID # 3 as the next hop. Then, the packet 7 is transmitted to the router 13 corresponding to the acquired RID # 3. Upon receiving the packet 7 from the router 11, the router 13 searches its own routing control table 3A based on the destination address RID # 5 of the received packet 7 at the time, and obtains RID # 2 as the next hop. Then, the packet 7 is transmitted to the router 12 corresponding to the acquired RID # 2.

When the router 12 receives the packet 7 from the router 13, the router 12 transmits the destination address R
It searches its own routing control table 2A based on ID # 5, and obtains RID # 4 as the next hop. Then, the packet 7 is transmitted to the router 14 corresponding to the acquired RID # 4. Upon receiving the packet 7 from the router 14, the router 12 searches its own routing control table 4A based on the RID # 5 of the received packet 7 at that time, and sets R as the next hop.
Obtain ID # 5. Then, the packet 7 is transmitted to the router 15 corresponding to the acquired router # 5. In this way, the packet 7 destined for the router 15 is
It is delivered to the router 15 via the route of the router 13 → the router 12 → the router 14 → the router 15. As described above, the router controls the packet transfer route using the route calculation method that limits the route search range, ie, the limitation of the number of hops. Even when a router that performs route calculation is applied to the network system, the load of the route calculation at each router does not increase as compared with the conventional method, so that the load associated with the route calculation processing at each router can be reduced.

(Second Embodiment) In the second embodiment, a value below the allowable hop number limit value preset for each of the routers 11 to 15 is set as the hop number limit value. Then, the shortest route that satisfies the limit value is assigned to each of the routers 11 to 15.
Is calculated. In this case, each of the routers 11 to 15 creates a route control table having a correspondence relationship between the destination address, the hop number limit value (1 to the allowable hop number limit value), and the calculated next hop of the route. The transfer control function unit 33 is notified of the routing control table. In the second embodiment, a destination address field 8A as shown in FIG. 7B is used as a data transfer unit which is a minimum unit of a packet.
And a hop number restriction field 8B (IP TTL field may be used) in the header.

In the second embodiment, the router that sends out the packet 8 to the network system 10 first specifies the number of hops on the route to the destination of the packet 8 in the hop number limit field 8B. Write the hop count limit. In the transfer control function unit 33 of the router that passes through the packet 8, the destination and hop number restriction field 8B of the destination address field 8A of the packet 8
And retrieves the next hop by searching its own route control table based on the limit value, and transfers the packet 8 to the router corresponding to the next hop. Then, at the time of this packet transfer, the limit value of the hop number limit field 8B of the packet 8 is reduced by one. The control function of the transfer control function unit 33 operates in each router through which the packet 8 passes, and transfers the packet to the destination hop-by-hop. In the present embodiment, the route on which the packet is actually transferred coincides with the route calculated by the source router of the packet 8.

Next, the communication costs between the routers in the network system shown in FIGS.
= 100, Cost # 1-3 = 20, Cost # 2-3
= 10, Cost # 2-4 = 20, Cost # 3-4 =
40, Cost # 4-5 = 30, and a specific example of the operation when the allowable hop number limit value is set to 3 is shown in FIGS.

FIGS. 10 to 12 show the routes (that is, the shortest routes) calculated so that each router 11 to 15 has the lowest communication cost based on the communication cost and the allowable hop number limit value set as described above. This is a routing control table created based on the above. Here, FIGS. 10A, 10B, and 10C show the router 1
1 are routing control tables 1B, 1C, 1D corresponding to the respective hop number limit values 3, 2, 1 of the router 11 created for each of the hop number limit values 3, 2, 1 according to FIG. (E),
(F) is the hop number limit value 3, 2, 1 by the router 12.
Each hop number limit value of router 12 created for each router 3, 2,
1 are routing control tables 2B, 2C, and 2D corresponding to the first and second routes. Also,
FIGS. 11A, 11B, and 11C show path control according to each hop number limit value 3, 2, 1 of the router 13 created by the router 13 for each hop number limit value 3, 2, 1. Table 3B, 3
C and 3D, and FIGS. 11D, 11E, and 11F show the hop number limit values 3, 2, and 2 of the router 13 created by the router 14 for each hop number limit value 3, 2, and 1, respectively. 4 are routing control tables 4B, 4C, and 4D corresponding to No. 1. Further, FIG.
(A), (b), and (c) are routing control tables 5B corresponding to the respective hop limit values 3, 2, and 1 of the router 15 created by the router 15 for the respective hop limit values 3, 2, and 1. , 5C, 5
D. Note that the-mark in FIGS. 10 to 12 indicates that the destination and the next hop (the next transfer destination) are directly connected.

FIG. 13 shows a sequence when a packet is transmitted from the router 11 to the router 15. The packet transfer operation will be described with reference to the routing table of FIGS. 10 to 12 and the sequence diagram of FIG. Packet 8 is shown in FIG.
As shown in the figure, router 11 → router 13 → router 14 →
The transfer route of the router 15 is taken. When transferring the packet 8, each of the routers 11, 13, and 14 performs the following processing.

That is, when the router 11 receives the packet 8 of the router 15 as the destination, the router 11 sets the hop number limit value 3 and the destination address RID # of the packet written in the hop number limit field 8A of the packet 8 as shown in FIG. 5
Based on the route control table 1B (FIG. 10A), and obtains RID # 3 as the next hop. Then, the limit value of the hop number limit field 8A of the packet 8 is reduced by one to set the hop number limit value to 2, and the packet 8 is transmitted to the router 13 corresponding to the acquired RID # 3.

The router 13 which has received the packet 8 from the router 11 has its own route control table 3C (FIG. 11 (FIG. 11) based on the destination address RID # 5 and the hop number limit value 2 of the received packet 8 at the time of FIG. b)) and obtain RID # 4 as the next hop. Then, the limit value of the hop number limit field 8A of the packet 8 is reduced by one to set the hop number limit value to 1, and the packet 8 is transmitted to the router 14 corresponding to the acquired RID # 4.

When the router 14 receives the packet 8 from the router 13, the destination address R of the received packet 7 is
Based on the ID # 5 and the hop number limit value 1, its own routing control table 4D (FIG. 11F) is searched, and RID # 5 is obtained as the next hop. Then, the restriction value of the hop number restriction field 8A of the packet 8 is reduced by one to set the hop number restriction value to 0, and the router 1 corresponding to the acquired RID # 5
The packet 8 is transmitted to 5. In this way, router 1
The packet 8 destined for 5 is sent from the router 11 to the router 13
It is delivered to the router 15 via the route from the router 14 to the router 15.

As described above, the router controls the packet transfer route by using the route calculation method in which the route search range is limited, that is, the limitation of the number of hops. Therefore, there are many packet transfer routes per router. Even when a router that performs route calculation is applied to a large-scale network system, the processing load of the route calculation at each router is not as large as that of the conventional method, and therefore, the load associated with the route calculation processing of each router can be reduced. Further, it is possible to limit the number of hops of a route that a packet follows to a destination. As described above, in the first and second embodiments, even when applied to a large-scale network, the load required for the route calculation processing of each router can be reduced as compared with the conventional method of calculating the shortest distance. it can. Therefore, the route can be updated quickly. Further, it is possible to prevent a packet transfer delay due to a delay in path control.

[0033]

As described above, according to the present invention, the router obtains a map including the connection configuration between the network and the router in the network system and the communication cost between the routers based on the execution of the routing protocol, and obtains the packet. When the limit value of the number of hops indicating the number of transfer routes is set, the shortest route indicating the route with the lowest communication cost among the transfer routes of the packet is calculated based on the acquired map and the set limit value of the number of hops. Therefore, even when a router is applied to a large-scale network system in which a large number of packet transfer routes exist per router, the router only needs to calculate the route within the set limit of the number of hops. Thus, the load associated with the calculation of the packet transfer path can be reduced. Also, the router calculates the shortest route, which is the route with the lowest communication cost, based on the acquired map and the preset limit value of the number of hops, and associates the calculated transfer destination on the shortest route with the packet destination. When the destination of the received packet matches the destination of the routing control table, the received packet is forwarded to the corresponding destination, so that the load associated with the route calculation of the router is reduced. While you can
Fast routing of routers is possible, and therefore packets can be transferred quickly.

When transmitting a new packet to the network system, the router records an allowable limit value of the number of hops before the packet is transferred to the destination in a hop number limit field of the packet, and When forwarding is performed, the limit value of the hop number limitation field of the received packet is reduced by one, and the packet is forwarded. Similarly, the load associated with the route calculation of the router can be reduced.
In addition, quick route control of the router becomes possible. Further, the router acquires the map of the network system, calculates the shortest route indicating the route with the lowest communication cost based on the obtained map and each preset limit value of the number of hops, and calculates the shortest route on the calculated route. The transfer destination of the packet and the destination of the packet are stored in a plurality of routing tables for each limit value of the number of hops, and when a new packet is transmitted to the network system, the hop number limit value is set in the hop number limit field. When forwarding a received packet after recording it, search the routing control table according to the limit value of the number of hops recorded in the received packet, and find the transfer destination corresponding to the destination of the received packet in the searched routing control table. Then, the limit value of the hop count limit field of the received packet is reduced by one and the packet is forwarded to the forwarding destination. It is possible to reduce the load due to road calculation allows rapid routing of the router.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a calculation state of a shortest route with a hop restriction to which a route calculation method according to the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a network system to which a route control system according to the present invention is applied.

FIG. 3 is a diagram showing a functional configuration of the network system.

FIG. 4 is a diagram showing a flow of processing of a route control function in each router of the network system.

FIG. 5 is a diagram showing a specific example of a link state in the network system.

FIG. 6 is a diagram schematically showing a map created by each unit in the network system.

FIG. 7 is a diagram showing a format of a packet communicated in the network system (FIG. 7A shows a packet format corresponding to the first embodiment;
(B) is a packet format corresponding to the second embodiment.

FIG. 8 is a diagram showing a routing control table created by each router in the network system (first embodiment).

FIG. 9 is a diagram specifically showing a sequence when a packet is transferred in the network system (first embodiment).

FIG. 10 shows each router 11 in the network system;
FIG. 12 is a diagram showing a routing control table created in Step No. 12 (second embodiment).

FIG. 11 shows each router 13 in the network system;
FIG. 14 is a diagram showing a routing control table created in each of steps 14 (second embodiment).

FIG. 12 is a diagram showing a routing control table created by a router 15 in the network system (second embodiment).

FIG. 13 is a diagram specifically showing a sequence when a packet is transferred in the network system (second embodiment).

FIG. 14 is an explanatory diagram showing a calculation state of a shortest route obtained by a conventional route calculation method.

[Explanation of symbols]

1A to 1D, 2A to 2D, 3A to 3D, 4A to 4D, 5
A to 5D: Routing control table (routing control table), 7, 8 ...
Packet, 7A, 8A: destination address, 8B: hop number limit field, 10: network system, 11-
Reference numeral 15: router, 21 to 26: network, 31: path control function unit, 32: internal device data transfer function unit, 33: transfer control function unit, 41: network data transfer function unit
RID # 1 to RID # 5: network layer addresses (addresses of routers 11 to 15), NID # 1 to NID
# 6: Network layer address (network 21
To 26 addresses).

Claims (4)

[Claims] 1. A network system comprising a plurality of networks and a plurality of routers connected to each network and transferring packets, wherein a routing protocol of the router executes a network between the network and the router in the network system. Obtaining a map including a connection configuration and communication cost between routers; setting a limit value of the number of hops indicating the number of transfer routes of the packet in the router; and obtaining the map and the set number of hops. The router calculates the shortest route indicating the route with the lowest communication cost among the transfer routes of the packet based on the limit value of the route. 2. A route control system in a network system comprising a plurality of networks and a plurality of routers connected to each network and transferring packets, wherein the router executes the routing protocol to execute the routing system. Means for acquiring a map including a connection configuration between a network and a router in the network and a communication cost between the routers, and a map based on the acquired map and a preset limit value of the number of hops indicating the number of transfer paths of the packet. Calculating means for calculating a shortest path indicating a path having a low communication cost; a path control table in which a transfer destination on the path calculated by the calculating means and a destination of the packet are stored in association with each other; The destination of the received packet matches the destination in the routing table. Transfer means for transferring the received packet to a corresponding transfer destination, wherein a plurality of routers sequentially transfer the packet using the transfer means to deliver the packet to a destination of the packet. A routing control system, characterized in that: 3. A route control system in a network system comprising a plurality of networks and a plurality of routers connected to each network and transferring a packet, wherein a destination of the packet is recorded in a header of the packet. A destination field, and a hop number restriction field in which a hop number restriction value indicating the number of transfer paths of the packet is recorded. The router, when transmitting a new packet to a network system, Means for recording an allowable limit value of the number of hops before the packet is transferred to a destination in a hop number limit field of the packet, and a limit of the hop number limit field of the received packet when the received packet is transferred. Transfer means for reducing the value by one and transferring it to the next destination. Routing system being characterized in that so as to deliver the packet to a destination of the packet by the router sequentially transfers the packets using each said transfer unit. 4. A route control system in a network system comprising a plurality of networks and a plurality of routers connected to each network and transferring a packet, wherein a destination of the packet is recorded in a header of the packet. And a hop number limit field in which a hop number limit value indicating the number of transfer paths of the packet is recorded, and the router is configured to execute a routing protocol to execute communication between the network and the router in the network system. Means for obtaining a map including a connection configuration between the routers and communication costs between routers, and calculating a shortest path indicating a path having the lowest communication cost based on the obtained map and each preset limit value of the number of hops. Calculating means, and a transfer destination on the route calculated by the calculating means. A plurality of routing tables in which the destination of the packet is stored for each limit value of the hop number, and when a new packet is transmitted to the network system, the packet is transmitted to the destination in the hop number limit field of the packet. Means for recording an allowable limit value of the number of hops to be transferred; and, when receiving the packet and transferring the received packet, searching a routing control table according to the limit value of the number of hops recorded in the received packet. And when a transfer destination corresponding to the destination of the received packet in the retrieved routing control table is detected, the transfer means for reducing the hop number limit field of the received packet by one and transferring the packet to the transfer destination. A plurality of routers sequentially transfer the packet using the transfer means, respectively, Wherein the packet is delivered to a destination of the packet.