JPH022759A - Routing system - Google Patents

Abstract

PURPOSE:To shorten a delay time by transferring a calling exchange and a repeating exchange by putting fixed path information corresponding to a logical channel number in a calling request packet on a packet, and transferring it by an reception exchange after deleting the information. CONSTITUTION:The calling exchange 3 performs the routing of a data packet depending on the result of the indexing of first and second tables setting the logical channel number in the data packet sent following the calling request packet from a terminal 1 as a key, and also, sends the packet after putting the fixed path information on the packet. The repeating exchange 4 and 5 perform the routing of the data packet depending on the result of the indexing of a third table setting the fixed path information in a received data packet as the key, and also, sends it after putting the fixed path information on the packet. The reception exchange 6, when recognizing that its own is the reception exchanging machine by indexing a fourth table setting the fixed path information in the received data packet as the key, deletes the fixed path information, and sends it to a terminal 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a routing method in a packet switching network.

Packet-switched networks have been used for communications that require high reliability, such as data transmission from data terminals, but transmission delays are not a problem, but recent technological advances have made real-time transmission of audio, video information, etc. The application area of module packet switching has expanded to media that require The present invention relates to a routing method for transferring high-speed data requiring real-time performance through a packet switching network using selective connections.

[Conventional technology]

In a packet-switched network, data is broken down into predetermined sizes called packets, and each packet is transferred with a header indicating the destination.The packet switch performs routing by checking the destination of each packet. Transfers are being made to the road. For this reason, the relay transmission path of a packet-switched network can be used more efficiently because packets from various terminals are mixed and transmitted, and the benefits include the possibility of efficient communication that takes advantage of variable speeds in video terminals, etc. There is.

On the other hand, since the packets transmitted from the originating terminal are routed packet by packet, they may take different routes between the originating and terminating exchanges, and there is a risk that the order may be reversed at the terminating exchange. For this reason, the destination exchange performs sequential control based on the sequence number in the header, and executes control to follow the order in which the messages were sent.

[Problem to be solved by the invention]

In order to apply packet switching networks to high-speed communications that require real-time performance, it is necessary to shorten the delay time between arrival and departure. Elements of delay time in a packet switching network include propagation delay time, queue delay such as waiting for sending out on a transmission path, delay due to the above-mentioned order control, etc. Of these, queue delays such as waiting for sending out on a transmission line are unique to packet switching, and the propagation delay itself is something that cannot be controlled. Therefore, the present invention aims to shorten the delay time by providing a routing method that eliminates the need for sequence control.

[Means to solve the problem]

To achieve the above object, in the present invention, in a packet switching network in which a plurality of packet switches are connected by a plurality of relay transmission paths, an originating exchange that accommodates an originating terminal, a relay exchange that accommodates a destination terminal, and a destination exchange that accommodates a destination terminal are provided. Multiple packet transfer routes are set in advance as fixed routes for pairs of originating and terminating exchanges, and the originating exchange learns the terminating exchange number from the destination address information in the call request packet from the originating terminal. , determining one of the fixed routes between the originating and terminating exchanges from the pair of the cough exchange number and the own exchange number, and storing the logical channel number in the call request packet in association with the fixed route; 1 table, a second table for storing the outgoing line and the fixed route in association with each other, and a sending means for transmitting the fixed route information as part of the packet in the packet. Each of the exchanges includes a third table for storing outgoing lines and the fixed routes in association with each other, and a receiving means for receiving the fixed route information sent as part of a packet. , a sending means for transmitting the fixed route information included in a packet as part of the packet, and the terminating switch has a fourth table for storing the outgoing line and the fixed route in association with each other. .

[Effect]

The originating exchange sequentially indexes each of the first and second tables using the logical channel number in the data packet sent following the call request packet as a key, and routes the data packet based on the results. At the same time, the sending means carries the fixed route information on the packet and sends it out, and each exchange serving as a relay exchange transmits the fixed route information carried as part of the received data packet to the receiving means. , the third table is indexed using this as a key, and the data packet is routed based on the result, and the sending means sends out the data packet with the fixed route information loaded on it, and the terminating exchange , when the fixed route information sent as part of the received data packet is extracted by the receiving means, the fourth
When the exchange determines that the own exchange is the terminating exchange, the data packet is transferred to the terminating terminal with the fixed route information deleted from the received data packet.

In the present invention, the route between the originating and terminating exchanges is selected from a plurality of routes set in advance. The route number α is determined, for example, from among the route numbers RTNO (β ways) determined by the following 2, assuming that the originating and terminating exchange numbers are m and n (m>n).

RTNO=(m(m-1)/2+n)X8+β where β is an integer that can take any value between l and β. The correspondence between these route numbers RTNO and each route is stored in a table, for example, in each exchange. It can be said that β is a number for identifying a plurality of routes set between the same originating and terminating exchange, and in this example, it is assumed that β≦8. Therefore, if a packet is sent with its route number RTNO added to the header, the receiving exchange can select a previously associated route from the route number RTNO by looking up the table.

Furthermore, if this route number corresponds to the logical channel number in the call request packet, it is possible to fix the data packet transfer route using this route number from call setup to call release.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, 1.2 is a packet terminal, 3 to 6 are packet switches, 7 and 8 are subscriber lines, 9 to 13 are relay transmission lines,
14 to 16 indicate fixed routes between originating and terminating exchanges.

FIG. 2 is an explanatory diagram showing an example of the packet format used in the present invention, in which 21 is a frame sequence, 22
is the address field, 23 is the control field, 24 is the frame check sequence, and 25 is the route number (RT
NO).

Figure 3 shows the logical channel numbers (LC) at the originating and terminating exchanges.
FIG. 3 is an explanatory diagram showing an example of a table that associates N) with route numbers. FIG. 4 is an explanatory diagram showing an example of a table that correlates route numbers and outgoing line numbers in each exchange.

The operation from call setup to communication will be explained step by step based on FIG. 1 below.

(2) A packet transmission request from terminal 1 is notified by a call request packet in which the address of the destination terminal, the logical channel number (LCN) to be used, etc. are written. The exchange 3 that receives the call request packet calculates the destination exchange number based on the destination terminal address in the level 3 (packet level protocol) of CCITT Recommendation X, 25. Note that the destination exchange number can be easily calculated from the destination terminal address if the numbering method of the terminal and the numbering method of the exchange are matched in advance.

(2) From the obtained destination exchange number and originating (2) exchange number, calculate the route number α using the calculation formula as described above, for example.

At this time, β is a fixed route between 8 or less originating and terminating exchanges (14
~16) Determine by a method such as using a random number less than or equal to the number, or determining by looking at the current usage status of the route between the originating and terminating exchanges. Next, as shown in FIG. 3, the correspondence between the logical channel number LCN and the route number RTNO is registered in a table.

■The packet switch 3 sets RTNO (route number) 25 in the header as shown in FIG. 2 for the data packet sent following the call request packet, and
The data packet is transmitted to the outgoing line number determined from the route number RTNO using the method shown in the figure. In addition,
The correspondence between the route number RTNO and the outgoing line number shown in FIG. 4 is such that a correspondence table is prepared in advance using, for example, a command.

(2) Each exchange 4.5 performs routing to the destination exchange 6 in the same manner as in (2). When the destination exchange 6 receives the data packet, it creates a correspondence table between the logical channel number LCN to be used and the route number RTNO as shown in FIG. 3 with the terminal, and transmits the incoming call packet to the terminal 2.

(2) If the terminal 2 is receivable, it responds to the exchange 6 using the logical channel number LCN set in the incoming call packet. The exchange 6 selects the already created logical channel number LC from the logical channel number LCN of the received packet.
The route number RTNO is calculated from the correspondence table of N to route number RTNo, the route number 25 is set in the header, and the packet is transmitted to the terminal 2 through the outgoing line determined from the route number as shown in FIG.

Thereafter, packets are transferred in the same manner. As shown in this example, the packet routing information 25 is sent attached to the header, and each exchange uses that information for routing and does not perform detouring, so call setup based on a call request is not required. The selected route will be used until released, and no packet order reversal will occur.

〔Effect of the invention〕

The present invention makes it possible to reduce delay time by providing a routing method that eliminates the need for sequence control, making it possible to apply packet switching networks to high-speed communications that require real-time performance. There are advantages to doing so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of the packet format used in the present invention, and FIG. 3 is a logical channel number (LCN) at the originating and terminating exchanges. FIG. 4 is an explanatory diagram showing an example of a table showing the correspondence between the route number (RTNO) and the outgoing line number in each exchange. . Explanation of symbols 1.2...Packet terminal, 3-6...Packet switching membrane, 7.8...Subscriber line, 9-13...Relay transmission line, 14-16...Departure/arrival exchange Fixed route between 21...
・Frame sequence, 22... Address field, 23... Control field, 24... Frame check sequence, 25... Route number (RTNO) Figure 1 Agent Patent attorney Akio Namiki

Claims (1)

[Scope of Claims] 1) In a packet switching network in which a plurality of packet switches are connected by a plurality of relay transmission paths, between an originating exchange in which an originating terminal is accommodated, a transit exchange in which a destination terminal is accommodated, and a terminating exchange in which a destination terminal is accommodated. Multiple packet transfer routes are set in advance as fixed routes for pairs of originating and terminating exchanges, and the originating exchange learns the terminating exchange number from the destination address information in the call request packet from the originating terminal, and A first method for determining one of the fixed routes between the originating and terminating exchanges from a pair of the destination exchange number and the own exchange number, and storing the logical channel number in the call request packet in association with the fixed route. a second table for storing the outgoing line and the fixed route in association with each other, and a sending means for transmitting the fixed route information as part of the packet, The first and second tables are sequentially indexed using the logical channel number in the subsequently sent data packet as a key, and the data packet is routed based on the results. Each exchange that transmits fixed route information and serves as a relay exchange has a third table that stores the outgoing line and the fixed route in association with each other, and the fixed route information is included in the packet as part of the table. and a transmitting means that transmits the fixed route information as part of the packet, and includes a receiving means for receiving the fixed route information sent as part of the received data packet. When the received fixed route information is retrieved by the receiving means, the third table is indexed using the fixed route information as a key, and the data packet is routed based on the result, and the fixed route information is added to the data packet by the sending means. The terminating exchange has a fourth table that stores the outgoing line and the fixed route in association with each other, and receives the fixed route information carried as part of the packet. When fixed route information sent as part of a received data packet is retrieved by the receiving means, the fourth table is indexed using the fixed route information as a key, and based on the result, A routing method characterized in that when the local exchange learns that the exchange is the destination exchange, the received data packet is forwarded to the destination terminal with the fixed route information deleted from the received data packet.