JPH09321795A - Packet switching system routing method - Google Patents

Abstract

Kind Code: A1 Abstract: The present invention relates to a routing method in a packet switching system composed of a plurality of packet switches and lines, and automatically generates a routing table for performing communication between packet switches by an optimum route. It is an object of the present invention to realize a routing method for a packet switching system that efficiently performs communication. SOLUTION: A transfer delay measurement packet is sent to an adjacent packet switch and a transfer delay time measuring unit for measuring a transfer time and a transfer delay measurement packet are received, and the packet is transferred to another packet switch by referring to a priority routing table. A routing information extraction unit that inserts the minimum transfer delay time into a transfer delay measurement packet and returns the packet, an actually measured transfer delay time,
The total transfer delay time is calculated by summing the transfer delay times in the received data, and a routing information management unit for generating a priority routing table and a routing processing unit for selecting an optimum route are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a routing method in a packet switching system including a plurality of packet switches and lines.

With the progress of the information-oriented society in recent years, the content of communication has increased from the conventional communication mainly using voice to the data communication for computer data communication.

There is a packet switching system as a communication system for efficiently performing such data communication. This is to divide the data to be transmitted from the terminal into blocks of a certain length called packets, and
The transmission order and the like are added, and the data is transmitted to the partner terminal through the vacant line.

In such packet communication, when the network is composed of a plurality of packet switches, there are a plurality of routes from the packet switch on the originating side to the packet switch on the receiving side. Therefore, in order to perform packet communication efficiently, it is necessary to use the route having the shortest transfer delay time from the plurality of routes, and a packet switching system that can efficiently perform route selection is provided. Is required.

[0005]

2. Description of the Related Art FIG. 10 is a diagram for explaining a conventional example. (A) in the figure is an example of a packet switching network, N1 to N5 are packet switching devices, and thick lines are packet switching devices N1 to N.
A line connecting 5 is shown.

(B) shows the routing table RT. The routing table RT is set when the network is constructed. In the figure, a packet switch (shown as a node in the figure) N1 is connected to a packet switch N2, a packet switch N3, and a packet switch N4, and sends a packet from the packet switch N1 to a packet switch N5 in the packet switch network. At this time, the routes are selected and transmitted in the order of the packet switch N2, the packet switch N3, and the packet switch N4 according to the designation of the routing table RT corresponding to the destination packet switch N5.

Also, in the figure, the packet switch N3
Are all packet switches N1 to N5 (excluding N3)
Connected to the routing table R as well.
A route is selected in the order of designation of T and the packet is transmitted.

As another method of generating the routing table RT, the transfer delay time is measured by transferring the packet for measuring the transfer time between the packet switches N1 to N5, and the routing table RT is automatically set. It is also possible to generate.

In the above conventional example, the packet switches N1 to N are used.
As described in the packet switching system consisting of 5,
It goes without saying that the number of packet switches is not limited to 5, but can be any number.

[0010]

In the above-mentioned conventional example, the routing between the packet switches N1 to N5 forming the packet switching network is executed according to the routing table RT set when the network is constructed. When routing is performed according to such a routing table RT, even if there is communication with high priority,
The communication is not always prioritized. Also,
In order to change the routing table RT, for example, a maintenance engineer needs to change the data from the maintenance console. However, the optimum routing table RT is set in response to the changing traffic at any time. Is impossible.

In the method of automatically generating the routing table RT, for example, a packet is sent from the packet switch N1 to all the packet switches N2 to N5 in the network, and the packet is sent to all the packet switches N2 to N5. Then, the packet switch N1 measures the transfer delay time. Similarly, the same procedure is applied to all the other packet switches N2 to N5 for all the packet switches N1 to N1 in the packet switching network.
Since it is executed for N5, the routing table RT
The load in the packet switching network is increased to generate the packet.

According to the present invention, by measuring the transfer delay time between two adjacent packet exchanges, a routing table for performing communication between the packet exchanges by the optimum route is automatically generated, and the communication is efficiently performed. We try to realize a routing method of a packet switching system that can be performed.

[0013]

FIG. 1 is a block diagram for explaining the principle of the present invention. N1 to N5 (5 may be any number of 6 or more) in the figure are packet switches, and bold lines indicate lines. In addition, the packet switch N
Since 1 to N5 have the same configuration, only the configuration of the packet switch N1 is shown as a representative.

In the packet switch Ni (i = 1 to 5),
Reference numeral 110 is a transfer for transmitting a transfer delay measurement packet to all adjacent packet switches Nj (except j = 1), receiving the transfer delay measurement packet returned from the packet switch Nj, and measuring a transfer time. Reference numeral 120 denotes a delay time measuring unit, and when a packet switch Nj receives a transfer delay measurement packet from the opposite packet switch Ni, another packet held in a priority routing table (shown as a priority routing table in the figure) RT1 Switch N
This is a routing information extraction unit that refers to the transfer delay time for k (excluding k = i, j), extracts the minimum transfer delay time, inserts it into the transfer delay measurement packet, and returns it.

Further, 130 is the total transfer delay time obtained by summing the transfer delay time measured by the transmission delay time measuring unit 110 and the transfer delay time set in the received transfer delay measurement packet, and the total transfer delay time is calculated for each route. Reference numeral 140 denotes a routing information management unit that stores the transfer delay time in a priority routing table (shown as a priority routing table in the drawing) RT1. When a call request is generated, 140 refers to the priority routing table RT1 and total transfer delay time Is a routing processing unit that selects a route that minimizes
The problem is solved by providing such a configuration.

In the above configuration, the packet switch N1
The operation will be described with an example of transferring a packet from the packet switch N5 to the packet switch N5. The transfer delay time measuring unit 110 of the packet switch N1 sends the transfer delay measurement packet DPKT to the adjacent packet switches N2 to N4. The packet switch N2 (N3, N4) that received the transfer delay measurement packet DPKT
Has the same effect. ) Is the route A _2i that minimizes the transfer delay time from the packet switch N2 to all the packet switches Ni in the network from the priority routing table RT1.
The transfer delay time t _2i is extracted, set in the transfer delay measurement packet DPKT, and transferred to the packet switch N1.

Upon receipt of the transfer delay measurement packet DPKT, the transfer delay time measuring unit 110 of the packet switch N1 obtains the difference ΔT ₂ between the time ST _{2 at} which the transfer delay measurement packet DPKT was sent and the time RT ₂ at which it was received, and manages the routing information. The unit 130 adds the time ΔT ₂ and the transfer delay time t _2i set in the transfer delay measurement packet DPKT to obtain the route A ₁₂ (where i in the route A _{ij is} the originating packet switch and j is the adjacent destination). , The total transfer delay time t _12i is set to the priority routing table RT1.
Write in.

Similarly, the transfer delay time measuring unit 110 and the routing information management unit 130 obtain the total transfer delay times t _13i and t _14i when the routes A ₁₃ and A ₁₄ are used, and the route number A _1i Along with this, the priority routing table RT1 is written. At this time, the priority routing table RT1
Are written in ascending order of total transfer delay time.

In this state, for example, the packet switch N1
When a call request is made to the packet switch N5,
The routing processing unit 140 refers to the priority routing table RT1 and sends the packet to the route with the smallest total transfer delay time, here, the route A ₁₂ .

With this operation, it becomes possible to automatically generate the priority routing table RT1 and select the route having the minimum total transfer delay time to transfer the packet.

[0021]

FIG. 2 shows an embodiment (1) of the present invention.
FIG. The figure shows the configuration of a packet switch Ni that constitutes a packet switch network.

The transfer delay time measuring unit 110, the routing information extracting unit 120, and the routing information managing unit 13 in the figure.
0, the routing processing unit 140, and the priority routing table RT1 have the same configuration as that explained in FIG. In the embodiment (1) shown in the figure, as a table to be used, in addition to the priority routing table RT1 described in the principle diagram, the measurement cycle T ₁ for measuring the transfer delay time and the delay time measurement management for designating the number of times of measurement N The configuration is such that a table 111, a subscriber information management table 151 for registering management information for each subscriber, and a communication control processing unit 150 for performing communication control according to the data of the subscriber information management table 151 are added.

In the present embodiment (1), a process for selecting a route that minimizes the total transfer delay time of packets transferred from the packet switch N1 to the packet switch N5 will be described. Transfer delay time measuring unit 110 of packet switch N2
In order to identify the route that minimizes the transfer delay time for the packet switch N5.
Routes A ₂₁ , A ₂₃ , A ₂₅ to 1, N3, N4, route numbers A ₂₁ , A ₂₃ , A ₂₅ , transmission start times ST ₁ , ST ₃ ,
Transfer delay measurement packet DPKT with ST ₅ set
(A _2i , ST _i ) is transmitted (here, i = 1, 3,
5). Further, the operations of the packet switches N1 and N3 are the same as the operations of the packet switch N2, and thus the description thereof will be omitted.

Transfer delay measurement packet DPKT
Upon receiving (A ₂₅ , ST ₅ ), the routing information extraction unit 120 of the packet switch N5 determines the route which is set in the priority routing table RT1 and which minimizes the transfer delay from the own packet switch N5 to each packet switch Ni. Of the transfer delay time t _i (in the case of the own packet switch, t ₅ = 0) is searched and set in the transfer delay measurement packet DPKT (A ₂₅ , ST ₅ ). It is transferred to the packet switch N2 as DPKT (A ₂₅ , ST ₅ , t _i ). Packet switch N1,
Since the operation of N3 is the same as the operation of the packet switch N5, the description thereof will be omitted.

Transfer delay measurement packet DPKT
(A_{twenty five}, ST_Five, T_i) Received packet switch N2
Transfer delay time measuring unit 110 is a routing information management unit.
Transfer delay time ΔT for 130_Five= RT_Five-ST_Five=
T_Five(； Route_{twenty five}) Is notified, and the routing information management unit 1
30 indicates a transfer delay in the priority routing table RT1
Interval T _FiveTo set.

When the transfer delay measurement packet DPKT (A _2i , ST _i , t _i ) is received from the packet switches N1 and N3, the total transfer sent to the packet switch N5 via the respective packet switches N1 and N3. Delay time T
_{i = RT i -ST i + t} 5; route A _2i, i = 1,3) a and, setting this to priority routing table RT1. Here, T ₅ <T ₃ <T ₁ .

With this processing, the priority routing table RT1 is generated in the packet switch N2. In the state where the priority routing table RT1 is generated in the packet switches N1 to N5 by the processes of to, the transfer delay time measuring unit 110 of the packet switch N1 identifies the route that minimizes the transfer delay with respect to the packet switch N5. , Route numbers A ₁₂ , A ₁₃ and A for the routes A ₁₂ , A ₁₃ and A ₁₄ to the adjacent packet exchanges N2 to N4.
₁₄ , the transfer delay measurement packet DPKT (A _1i , ST _i ) in which the transmission start times ST ₂ , ST ₃ , ST ₄ are set is transmitted.

Transfer delay measurement packet DPKT
(A₁₂, ST_Two) Received by the packet switch N2
The routing information extraction unit 120 uses the priority routing table.
Each packet from the own packet switch N2 by referring to
To the route that minimizes the transfer delay time to the switch exchange Ni.
Transfer delay time t_i(In the case of own packet switch N2
Is t _Two= 0), and the transfer delay measurement packet D
PKT (A₁₂, ST_Two) And transfer delay measurement packet.
DPKT (A₁₂, ST_Two, T_i) Packet switch as
Transfer to machine N1. In the present embodiment (1), the packet
Transfer delay time from the switch N1 to the packet switch N5
Since the smallest route is identified, the packet switch N2
Who has the minimum transfer delay time from the packet switch N5 to the packet switch N5
Road A_{twenty five}Transfer delay time t_i= T_FiveIs the target.

Transfer delay measurement packet DPKT
(A₁₂, ST_Two, T_Five) Received packet switch N1
Of the transfer delay time measurement unit 110_Two= R
T_Two-ST _Two), The routing information management unit 130
Is the transfer delay time Δ determined by the transfer delay time measuring unit 110.
T_TwoAnd transfer delay measurement packet DPKT (A₁₂, ST_Two,
t_Five) Transfer delay time t notified by_FiveTime T
_Five= ΔT_Two+ T_FiveFrom the packet switch N1
Route A to switch N5₁₂Delay time T when using
_TwoRegistered in the priority routing information table RT1 as
You.

Similarly, the delay time measurement packet DPKT (A ₁₃ , ST) received from the packet switches N3 and N4 is received.
₃ , t ₅ ) and the transfer delay times T ₃ and T ₄ obtained from the DPKT (A ₁₄ , ST ₄ , t ₅ ) are compared with the total transfer delay time T ₂ when the route A ₁₂ is used, The priority routing table RT1 is rewritten in ascending order of total transfer delay time. Here, T ₂ <T ₃ <T ₄ .

In the embodiment (1), the measurement cycle T ₁
And delay time measurement management table 11 that specifies the number of measurements N
1 is provided, and when the measurement cycle T ₁ is designated, the total transfer delay time is measured at the cycle T ₁ and the priority routing table RT1 is updated periodically. When the number of times of measurement N is specified, the processes of to are repeated N times, the average value of the total transfer delay times is calculated, and the average value is written in the priority routing table RT1. The total transfer delay time t _{1i5N in the figure} indicates that the total transfer delay time to the packet switch N5 was measured N times using the _route A _1i and the average value was taken.

FIG. 3 shows a sequence diagram (1) of the embodiment (1) of the present invention. In the sequence diagram (1) shown in the figure, the designation N of the number of measurements in the delay time measurement management table 111 is N.
= 1.

Measurement of transfer delay time of packet switch N2
The transfer delay measurement packet DPKT (A_{twenty five},
ST_Five) Is sent to the packet switch N5. Routing information extraction unit 12 of packet switch N5
0 is the transfer delay time in the priority routing table RT1
t_iRefer to, when the transfer delay of the route with the minimum transfer delay time
(Here, the packet transfer destination is the packet switch N5.
Therefore, t _Five= 0. ) And set the transfer delay
Constant packet DPKT (A_{twenty five}, ST_Five, T _Five) As a package
To the switch exchange N2.

The packet switch N2 receives the received transfer
Delay measurement packet DPKT (A_{twenty five}, ST_Five, T_Five)
Route A_{twenty five}Delay time T when using_FiveSeeking
You. Similarly, the transfer delay is delayed for the packet switches N3 and N1.
Total measurement packet DPKT (A_{twenty five}, ST_Five), And then fold
From the returned packets, each route A_{twenty one}, A _{twenty three}To
Calculate the total transfer delay time when used, and
The table RT1 is generated.

From the transfer delay time measurement unit 110 of the packet switch N1, the transfer delay measurement packet DPKT (A ₁₂ ,
ST ₂ ) is sent to the packet switch N2. Routing information extraction unit 12 of packet switch N2
0 refers to the transfer delay time t _i in the priority routing table RT1, sets the transfer delay time of the route with the minimum transfer delay time, and transfers the transfer delay measurement packet DPKT (A ₁₂ , S ₁₂
T _2, t ₅₎ sends to the packet switch N1 as.

The packet switch N1 receives the received transfer
Delay measurement packet DPKT (A_{twenty five}, ST_Five, T_Five)
Route A₁₂Delay time T when using_TwoSeeking
You. Similarly, the transfer delay to the packet switches N3 and N4 is delayed.
Total measurement packet DPKT (A_1i, ST_i), And then fold
From the returned packets, each route A₁₃, A ₁₄To
Calculate the total transfer delay time when used, and
The table RT1 is generated.

By this processing, the total transfer delay time is obtained, and the priority routing information table RT1 is automatically generated by arranging in order from the smallest delay time. N is 1
In other cases, the processes of to are repeated, the transfer delay time is measured N times, the average value thereof is obtained, and the priority routing table RT1 is generated.

FIG. 4 shows a sequence diagram (2) of the embodiment (1) of the present invention. The sequence diagram (2) shown in the figure is an example in which the measurement period T ₁ is designated in the delay time measurement management table 111.

In this case, each time T ₁ elapses,
The packet switch N1 sends a transfer delay measurement packet DPKT _i (A ₁₂ , ST ₂ ) to the packet switch N2 to measure the transfer delay time.

Transfer delay measurement packet DPKT _i (A ₁₂ ,
The operation of the packet switch N2 that receives ST ₂ ) is similar to the operation described in the embodiment (1) of FIG. Also,
The packet switch N1 can send a transfer delay measurement packet to another packet switch Ni, and the measurement cycle can be set to an arbitrary time for each packet switch Ni.

FIG. 5 shows a sequence diagram (3) of the embodiment (1) of the present invention. The figure shows the measurement of the transfer delay time when a failure occurs in the route A ₁₂ between the packet switch N1 and the packet switch N2. Here, when the route failure is detected, the routes other than the route A ₁₂ (in the figure, the route A ₁₃
However, the same applies to all other routes), and the priority routing table RT1 is generated from the result.

By this processing, it becomes possible to generate the priority routing table RT1 in the network corresponding to the faulty state and perform the optimum routing according to the priority routing table RT1.

FIG. 6 is a diagram for explaining the embodiment (2) of the present invention. In the subscriber information management table 151 of the packet switch Ni of the embodiment (2), the service class is registered in correspondence with the subscriber address, and the priority routing table RT1 is constructed for each service class (shown as a class in the figure) i. are doing.

As described above, the service class i (i = 1 in the figure is an example) is registered in correspondence with the subscriber address DTA, and the transfer delay time described in the embodiment (1) of FIG. The packet is efficiently transferred by performing the measurement for the service class i, generating the data of the priority routing table RT1 for the service class, and performing the routing for each service class according to the priority routing table RT1. it can.

FIG. 7 is a diagram for explaining the embodiment (3) of the present invention. In the embodiment (3), the resource management processing unit 160 corresponds to the service class described in the embodiment (2), and the resource management processing unit 160 corresponds to the communication having a high priority. The resource amount R ₁ to be allocated is registered in the resource management table 161.

For high priority communication, the allocated resources are used to perform communication,
To prevent resource shortage for high priority communication.

FIG. 8 is a diagram for explaining the embodiment (4) of the present invention. The configuration of FIG. 8 has a configuration in which a threshold value O ₁ for determining traffic congestion corresponding to the time zone Tm and a traffic monitoring unit 162 are added to the resource management table 161 of the embodiment (3) described in FIG. 7.

In the configuration shown in the figure, the resource management table 161 specifies the resource amount R ₁ to be secured for high priority communication in the time zone Tm. The traffic monitoring unit 162, for example, routes A ₁₂ , A ₁₃ , A ₁₄
Performs each of the traffic monitoring, if the traffic route A ₁₂ exceeds a threshold value O ₁ notifies the routing processing unit 140 that exceeds a threshold O _1.

Here, assuming that the priorities p1, p2, p3 of the packets P1, P2, P3 are p1>p2> p3, if the traffic of the route A ₁₂ exceeds the threshold value O ₁ , the packet of low priority is given. order, in the order of P3, P2, P1, and transfers toward another path a _13, a ₁₄ (route a ₁₃ ,, in the figure shows the order to be transferred to another route). While the traffic on the route A ₁₂ exceeds the threshold O ₁ ,
Continue sending low priority packets to other routes.

The traffic monitoring unit 162 is to continue the monitoring of the traffic, for example, when it is detected that the traffic route A ₁₂ falls below the threshold value O _1, the threshold O ₁
Is notified to the routing processing unit 140,
The routing processing unit 140 transfers the packet P2 having the higher priority among the packets P2 and P3 transferred to the route A ₁₃ to the route A ₁₂ .

By this processing, packets of low priority are transferred to other routes according to the traffic congestion state,
It is possible to guarantee communication of packets with high priority. FIG. 9 shows a diagram for explaining the embodiment (5) of the present invention. The configuration of FIG. 9 is the packet terminal D accommodated in the packet switch N1 in the embodiment (4) described in FIG.
It is a figure explaining the procedure at the time of making a call to the packet terminal DTb accommodated in the packet switch N5 from Ta.

In the subscriber information management table 151 of FIG. 9, information on whether or not to use the priority routing table RT1 is written for each subscriber's joining address DTA. When using, the priority routing table RT1 is written. The routing is executed by using the table RT1, and when it is not used, the routing is executed according to the normal routing table RT2.

The packet terminal DTa sends out a call request packet CR (DTa, DTb), and the packet switch N
The communication control processing unit 150 of No. 1 is the resource management processing unit 160.
Then, the traffic of the route that minimizes the transfer delay is inquired. Upon receiving the inquiry request, the resource management processing unit 160 notifies the communication control processing unit 150 whether or not the traffic on the route having the minimum transfer delay exceeds the threshold O ₁ .

When the threshold O ₁ is not exceeded, the communication control processing unit 150 notifies the routing processing unit 140 of the use of the priority route, and the routing processing unit 140 receiving the priority route use notification gives priority to the routing processing unit 140. Routing table R
A call request packet CR in which T1 is searched by the service class, the route A ₁₂ that minimizes the transfer delay is selected, and the priority route use facility F ₁ is added to the route A ₁₂
(DTa, DTb, F ₁ ) is transmitted. When the use of the priority route is not notified, the normal routing table RT2 is used.
Call request packet CR (DTa, DTb) according to
Is sent.

The communication control processing unit 150 refers to the subscriber information management table 151, and when the priority route use designation is registered, sends a priority route use notification to the routing processing unit 140.

The selected route depends on the congestion of the adjacent exchange.
If the packet cannot be transferred, the next transfer delay is
Sends a packet to the Sana route. Call request packet
CR (DTa, DTb, F₁) Received adjacent packet
Routing processing unit 140 of the exchange N2
Facility F used₁Is added, so the packet
By performing the same processing as the exchange N1, the transfer delay is reduced.
Perform routing to select the smallest route. priority
Route use facility F ₁If is not added,
In the same way as described for the case changer N1, the normal routine is executed.
Normal routing processing by referring to the table RT2
Perform

Also, via a plurality of packet switches,
When packets are transferred, the same processing is executed in each packet switch. Call request packet C from the packet terminal DTa
When the communication control processing unit 150 of the packet switch N1 detects that the priority route use facility F ₁ is added in R (DTa, DTb, F ₁ ), it refers to the subscriber information management table 151. If the use of the preferential route use facility F ₁ is permitted, the preferential route use is notified to the routing processing unit 140, and the routing processing unit 140 executes the routing process according to the procedure described in.

Further, referring to the subscriber information management table 151 corresponding to the subscribers (DTa, DTb), the traffic management threshold value O ₂ for each subscriber is set to the resource management processing unit 16.
Notify 0. The resource management processing unit 160 monitors the traffic with the traffic monitoring unit 162, and monitors whether or not the threshold value O ₂ is exceeded. If the traffic value exceeds the threshold value O ₂ , the routing processing unit 140 notifies the routing processing unit 140 of the resource usage threshold value O _2. When the routing processing unit 140 is notified that the resource usage threshold O ₂ is exceeded, the routing processing unit 140 executes the routing processing according to the procedure described in FIG.

[0059]

According to the present invention, the route from the packet switch accommodating the source terminal to the packet switch accommodating the destination terminal that minimizes the packet transfer delay time is automatically selected for routing. This makes it possible to reduce the transfer delay time in the network.

Furthermore, by setting a priority for each service class and securing a resource for each priority, it becomes possible to preferentially perform communication with respect to communication having a high priority.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the principle of the present invention.

FIG. 2 illustrates an embodiment (1) of the present invention.

FIG. 3 is a sequence diagram (1) according to the embodiment (1) of the present invention.

FIG. 4 is a sequence diagram (2) according to the embodiment (1) of the present invention.

FIG. 5 is a sequence diagram (3) in the embodiment (1) of the present invention.

FIG. 6 illustrates an embodiment (2) of the present invention.

FIG. 7 is a diagram illustrating an embodiment (3) of the present invention.

FIG. 8 is a diagram illustrating an embodiment (4) of the present invention.

FIG. 9 is a diagram illustrating Embodiment (5) of the present invention.

FIG. 10 illustrates a conventional example.

[Explanation of symbols]

 N1 to N5 packet switch 110 transfer delay time measurement unit 111 delay time measurement management table 120 routing information extraction unit 130 routing information management unit 140 routing processing unit 150 communication control processing unit 151 subscriber information management table 160 resource management processing unit 161 resource management Table 162 Traffic monitoring unit RT1 Priority routing table RT2 Normal routing table RT Routing table DTi terminal

Claims (9)

[Claims] 1. A packet switching system comprising a plurality of packet switching devices and a plurality of lines connecting the packet switching devices to each other, wherein all packet switching devices (Nj, j = 1) adjacent to the packet switching device (Ni) are connected to each other. except for)
, A transfer delay measurement packet that transmits a transfer delay measurement packet, receives the transfer delay measurement packet returned from the packet switch (Nj), and measures the transfer time; and the packet switch (Nj). When a transfer delay measurement packet is received from the opposite packet switch (Ni),
The transfer delay time for other packet switches (excluding Nk, k = i, j) held in the priority routing table is referred to, the minimum transfer delay time is extracted, inserted into the transfer delay measurement packet, and returned. The total transfer delay time is calculated by taking the sum of the transfer delay time measured by the routing information extraction unit and the transfer delay time measurement unit and the transfer delay time set in the received transfer delay measurement packet, and the total transfer for each route. A routing information management unit that accumulates the delay time as a priority routing table, and a routing processing unit that selects the route that minimizes the total transfer delay time by referring to the priority routing table when a call request occurs, Routing delay measurement from the packet switch (Ni) to the packet switch (Nk) to the adjacent packet switch (Nj) A route in which the total transfer delay time obtained by adding the transfer delay time measured by transferring the packet and the transfer delay time to the incoming packet switch (Nk) held in the priority routing table by the adjacent packet switch (Nj) is minimum. A routing method of a packet switching system characterized by selecting and executing. 2. The routing method of the packet switching system according to claim 1, further comprising a delay time measurement management table for setting a condition for activating the transfer delay time measurement unit of the packet switch (Ni), the delay time measurement management table being provided. 2. The routing method of the packet switching system according to claim 1, wherein a measurement cycle for activating the transfer delay time measuring unit is set, and the transfer delay time is measured each time a predetermined time elapses. 3. The routing method of the packet switching system according to claim 1, wherein a predetermined number of consecutive activations of the transfer delay time measuring unit is set in the delay time measurement management table of the packet switch (Ni), and transfer is performed. The routing method of the packet switching system according to claim 1, wherein the delay time is an average value measured a predetermined number of times. 4. The routing method of the packet switching system according to claim 1, wherein a service class registration unit for registering a service class of the subscriber is provided in a subscriber information management table of the packet switch (Ni), and a transfer delay time 2. The routing method for a packet switching system according to claim 1, wherein the measurement is executed for a service class and the priority routing table is configured for the service class. 5. The routing method of the packet switching system according to claim 4, wherein a resource management processing unit that manages resources allocated to high priority communication for each route of the packet switching device (Ni), Provide a resource management table for registering resources to be allocated to high-frequency communication, and for high-priority communication, perform communication using the high-priority resource allocated in the resource management table. The routing method of the packet switching system according to claim 4. 6. The routing method of the packet switching system according to claim 1, wherein a traffic monitoring unit that measures a traffic volume for each route of the packet switch (Ni), and the route in the resource management table for each route. If you set a threshold to determine whether to send the traffic of the other route to another route, and the traffic of the selected route exceeds the threshold,
2. The routing method of the packet switching system according to claim 1, wherein the communication with low priority is sent to the next selected route. 7. The routing method of a packet switching system according to claim 5, wherein the amount of resources to be allocated to high-priority communication and a traffic threshold value for bypassing the communication are set in the resource management table for each time zone. 7. The routing method of the packet switching system according to claim 5, wherein: 8. The routing method for a packet switching system according to claim 1, wherein when a subscriber uses a route having a minimum transfer delay time, a threshold for setting an upper limit of traffic for each subscriber is set as the subscriber information management. The routing method of the packet switching system according to claim 1, wherein a table is set to restrict traffic using a route having a minimum transfer delay time for each subscriber. 9. The routing method of a packet switching system according to claim 1, wherein when a subscriber sends a calling packet, an information element designating that routing is performed according to the priority routing table is set in the calling packet. The routing method of the packet switching system according to claim 1, wherein the routing method is performed by transmitting the packet.