JPH0372749A - Packet communication system - Google Patents

Abstract

PURPOSE:To improve the exchange efficiency of a packet switchboard by connecting packet form terminal equipments with a 2nd communication line not through the packet exchange while a logical channel is set so as to send a data packet. CONSTITUTION:A line changeover control means Ka of terminal earth stations K1-Kn sets newly a satellite communication line connecting packet form terminal equipments being a caller and a called party directly when the transmission reception of a control packet caller and called party packet form terminal equipments P1-Pn and a packet switchboard X are finished and the setting of a logical channel is finished. Then the satellite communication line is switched to a newly set direct satellite communication line from the satellite communication line via the packet switchboard X and the data packet is sent further via the direct satellite communication line. Then, the quantity of the packet handled by the packet switchboard is reduced, the load is relieved and the exchange efficiency of the packet switchboard is improved.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to improvements in packet communication systems.

(Prior art) In the packet switching method, transmission data is divided into blocks of a fixed length by an exchange or a terminal device, and a header containing information necessary for transmission such as destination information is added to each block to form a packet. It is a system that transmits these packets as a unit, and has excellent service functions not found in circuit switching systems, such as communication between different speed terminals, packet multiplex communication, and communication with extremely high transmission quality. The connection forms of the packet switching method mainly include ■ Partner selection connection method: A connection in which the communication partner is not fixed and can communicate with any partner (virtual call: V
C) ■ Permanent connection: A connection in which the communication partner is always fixed to one specific partner (permanent virtual circuit:
There are two types of PVC), and the communication protocol (protocol) related to the connection operation uses the X.25 protocol recommended by CCITT.

Figure 4 shows an example of the configuration of a packet switching system built based on the x, 25 protocol. Each trunk T1 to Tn of the packet switch Devices (PADs) are connected one-to-one via communication lines L1 to Ln. The protocol conversion device is for connecting non-packet terminals NPTI to NPTm that do not have packet transmission/reception capabilities, and logically an infinite number of non-packet terminals NPT can be connected.

By the way, when data is transmitted using the virtual call method in this type of system, the conventional method is as follows, for example. That is, let us now assume that packet terminal P1 performs a calling operation to another packet terminal P2.

Then, the packet terminal P1 connects the communication line Ll with the packet switch A call request packet including the address of the destination packet terminal P2 is sent to the packet switch X. Packet switch X, which receives this call request packet, determines which packet terminal the call request is for from the destination address in the call request packet, and connects the communication line L2 with this packet terminal P2. , selects an empty logical channel from among all the logical channels held by trunk T2, and transfers the incoming call packet containing the logical channel identification information to trunk T2.
The packet is sent from the terminal P2 to the packet terminal P2. In response, the packet terminal P2 on the called side notifies the incoming call and returns a packet to the packet switch X to accept the incoming call. Then, the packet switch X sends a connection completion bucket to the packet terminal P1 on the calling side to notify that the acceptance of the call has been completed. Thus, the calling packet terminal P1
A communication path is formed between the callee and the packet terminal P2 on the called side, physically via the communication lines Ll and L2, and logically via the above-mentioned logical channels. Using this, data packets can be transmitted between the packet terminals PI and P2.

On the other hand, when the data transmission is completed and a recovery operation is performed at the packet terminal P1, for example, a recovery request packet is sent from the packet terminal P1 to the packet switch X. Then, the packet switch
At the same time, a disconnection confirmation packet is sent back to the bucket terminal P1 where the recovery operation was performed. In response to this, the packet terminal P1 returns to the standby state.

In addition, the packet terminal P2 returns to the standby state upon receiving the disconnection instruction packet, and further sends a disconnection confirmation packet back to the packet switch X to notify it of recovery confirmation. In this way, the logical communication path between both packet terminals Pi and P2 is opened, and further communication line Ll is opened.

L2 is also disconnected.

(Problems to be solved by the invention) However, such conventional packet communication systems have the following problems. That is, in the conventional system, not only the transmission of control packets performed at the time of call origination/reception and disconnection, but also the transmission of data packets performed in a state where a logical channel is set, are all performed via the packet switch X. For this reason, when the number of terminals connected to a packet switch increases, the packet switch spends a lot of time controlling the transmission of data packets flowing in from each terminal, which reduces the efficiency of the switching operations that should be performed. There was a problem.

Therefore, the present invention focuses on the above-mentioned circumstances, reduces the amount of packets handled by the packet switch, and reduces the load.
The purpose of this invention is to provide a packet communication system that can improve the switching efficiency of a packet switch.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned objective 1, the present invention provides a packet type terminal with call origination/reception and disconnection! In addition to logical channel setting and opening control means for transmitting and receiving control packets to and from the packet switching equipment via the first communication line to set and release logical channels, a line connection control means; and a data packet transmission control means, and with the logical channel set, the line connection control means connects the packet type terminal of the communication partner via a second communication line without going through a packet switch; The data packet transmission control means transmits data packets to and from the communication partner packet-format terminal via the second communication line connected by the line connection control means.

Another aspect of the present invention provides, in addition to a packet switching device and a plurality of packet format terminals connected to the packet switching device via a first communication line, a line connection control device is provided corresponding to each of these packet format terminals. , this line connection control device includes a control packet transmission means, a line connection means, and a data packet transmission means, and transmits and receives the control packets transmitted and received by the corresponding packet type terminal at the time of call origination, reception, and disconnection of the corresponding packet type terminal. The control packet transmission means transmits the packet to the packet switch via the first communication line, and the line connection means sets the logical channel between the packet format terminal and the packet switch. , a communication partner packet type terminal is connected to a line connection control device corresponding to the packet type terminal via a second communication line not via the packet switch, and thereafter data packets transmitted and received by the packet type terminal are transmitted to and received by the data packet transmission means. Accordingly, the data is transmitted via the second communication line.

(Function) As a result, according to the present invention, when a logical channel is set between two packet-type terminals that communicate with each other and a packet switch, a second communication channel is established between these packet-type terminals without going through the packet switch. After that, data packet transmission between both packet type terminals will be performed via this second communication line. In other words, data packets are transferred without going through a packet switch. Therefore, the packet switch only needs to control the setting and release of logical channels at the time of call origination, call recovery, and recovery, and there is no need to control the transmission of data packets.

Therefore, the load is reduced, and it becomes possible to control connections between other packet-type terminals to the extent that the load is reduced, thereby increasing the efficiency of exchange.

According to yet another aspect of the present invention, the second route after setting up the logical channel. Since the connection between each bucket type terminal via four wires and the transmission of data packets via this second communication line are performed by the line connection control device, there is no need to change the configuration of each packet type terminal, and it is not necessary to change the configuration of each packet type terminal. You can use the configuration as is. Therefore, existing systems can be implemented relatively easily and inexpensively.

(Embodiment) FIG. 1 shows the functional configuration of a satellite packet communication system to which a packet communication system according to an embodiment of the present invention is applied.

0 In the figure, a packet switch X and a plurality of packet type terminals P1 to Pn include satellite communication earth stations HUB and Kl.
~Kn are installed in one-to-one correspondence, respectively. These earth stations HUB, Kl to Kn are connected to the packet switch X
In response to connection requests from each packet type terminal P1 to Pn, a satellite communication line is set up between each trunk T1 to Tn of packet switch X and each packet type terminal P1 to Pn, and the set satellite communication It has a function of transmitting control packets output from the packet exchange X and the packet type terminals P1 to Pn via the line. Note that one channel of each of the satellite communication lines CHI to CHn possessed by the transponder of the communication satellite S is allocated between each of the trunks T1 to Tn of the packet switch X and each of the packet type terminals P1 to Pn.

Incidentally, among the above-mentioned earth stations, earth stations 1 to Kn have a line of sight switching control means Ka in addition to the above-mentioned functions. After the transmission and reception of control packets between each packet type terminal on the calling side and the called side and the packet switching equipment A new satellite communication line will be set up between the terminals to directly connect these terminals. Then, connect the communication line to the packet switch
The satellite communication line via the satellite communication line is switched to this newly established direct satellite communication line, and thereafter data packets are transmitted via this direct satellite communication line.

Next, the packet communication system of this embodiment will be explained based on the above configuration. Assume now that the packet terminal P1 makes a call to the packet terminal P2 as shown in FIG. Then, the packet terminal P1 first selects an empty logical channel from among all the logical channels (for example, a maximum of 4096 channels) held by the trunk T1 to which it corresponds among the trunks T1 to Tn of the packet switch X, and A call request packet (C
R packet) and transmits it to the earth station. Then, the earth station 1 sets up a satellite communication line CHI between the earth station HUB corresponding to the packet 2 exchange It is transmitted to the satellite communication earth station HUB via the line CHI. The thus transmitted CR packet is frequency-converted and returned to the original signal at the earth station HUB, and then transferred to the trunk T1 of the packet switch X.

On the other hand, the packet switch packet terminal P2 is identified. And this packet terminal P1
The same logical channel as the logical channel represented by the logical channel identification information included in the CR packet is selected from among all the logical channels possessed by the trunk T2 corresponding to A packet (CN packet) is created and transferred from trunk T2 to earth station HUB. Note that 3. If the same logical channel as the one included in the above CR packet is not free, it is determined that it is busy and a control packet to that effect is sent to the calling side packet terminal P1. do. When the above CN packet is transferred, the earth station HUB sets up a satellite communication line CH2 between the earth station 2 on the called side, converts the above CN packet into a signal format suitable for satellite communication, and then transmits the satellite communication. 2 to the earth station via line CH2. CN transmitted to this earth station to 2
The packet is returned to the original signal and then transferred to the called packet terminal P2.

On the other hand, the packet terminal P2 on the called side receives the CN packet and learns that an incoming call has occurred, creates an incoming call acceptance packet (CA packet), and transfers it to the earth station 2. At this time, the same logical channel identification information as the logical channel identification information included in the CN packet is inserted into the CA packet. Then, the above CA packet is converted to a signal form suitable for satellite communication at the earth station 2, and then transmitted to the earth station HUB via the satellite communication line CH2, where it is converted back to the original signal. It was later introduced into packet switch X. In response to this, the packet switch Forward. Then, this CC packet is transmitted to the earth station 1 via the satellite communication line CHI, and from this earth station 1 is transferred to the calling side packet terminal P1. Thus, a logical channel for data packet (DT packet) transmission is established between the calling side packet terminal P1 and the called side packet terminal P2.

Now, when the logical channel settings are completed, 1 selects an empty satellite communication channel for the calling earth station, and sends packets between it and the called earth station 2 as shown in Figure 1. A direct satellite communication line CHj that does not go through exchange X is set up. Then, the communication line used between the packet terminal P1 and the packet terminal P2 on the calling side is connected to the packet switch X.
Switch from the satellite communication lines CHI, CH2 via 5 to the above-mentioned direct satellite communication line CHj,
is open. Therefore, the DT packets sent from the packet terminals PI and P2 on the calling and called sides are transmitted via the satellite communication line CHj without going through the packet switch X, as shown in FIG. That will happen.

FIG. 3 shows an example of the format of this DT packet. The head of the data contains a general format identifier, logical channel identification information consisting of a logical channel group number and a logical channel number, and a confirmation of delivery of the DT packet. A receiving sequence number and a transmitting sequence number used for this purpose are respectively added. Furthermore, this D
During the transmission period of the T packet, the packet switch X maintains the logical channel as a busy channel even if no DT packet arrives.

When the transmission of the DT packet is then completed and, for example, a recovery operation is performed at the packet terminal P1, the packet terminal P1 transfers a recovery request packet (CQ packet) 6 to the earth station. Then, at the earth station 1, a satellite communication line CHI is set up between the earth station HUB corresponding to the packet exchanger It also returns to the line CHI and transmits the above CQ packet to the earth station HUB via this satellite communication line CHI. Therefore, the recovery request from the packet terminal P1 is transmitted to the packet switch X. Then, the packet switch
Transfer to B, and then send a disconnection confirmation packet (CF packet)
is created and transferred to the earth station HUB from the trunk T1 corresponding to the packet terminal P1 on the recovery requesting side. Earth station HUB
is a satellite communication line CH between the earth station of the communication partner and 2.
2 and connect the above CI via this satellite communication line CH2.
The packet is transmitted to the earth station 2. At the same time, the CF packet is sent back to the earth station 1 on the restoration requesting side via the satellite communication line CHI.

Therefore, the recovery requesting packet terminal P1 is notified of the recovery confirmation, and as a result, the packet terminal P1 is restored to the standby state. On the other hand, when the above CI packet is sent, the earth station receives 2
Then, the communication line used is switched from the satellite communication line CHj for DT packet transmission to the satellite communication line CH2 connecting with the packet switch X, and the CI packet is transferred to the packet terminal P2. Therefore, the packet terminal P2 transfers the CF packet to the earth station 2 to be sent back to the packet switch X, and then returns to the standby state. On the other hand, when the CF packet is returned from the packet terminal P2 via the satellite communication line CH2, the packet switch X releases the logical channel set between each of the packet terminals PI and P2.

If this is absolutely impossible, by setting up satellite communication lines CHI and CH2 between each packet terminal PI and P2 and the packet switch X, each packet terminal PI and Control packets are transmitted between P28 and packet switch X, while after setting the logical channel, each packet terminal Pi,
By setting up a direct satellite communication line CHj between P2, DT packets are transmitted without going through packet switch X, so packet switch It is only necessary to set up and release logical channels accordingly. Therefore, compared to the conventional method in which all packets from control packets to DT packets are transmitted via the packet switch, the load on the packet switch X can be reduced.
exchange efficiency can be increased.

In addition, in this embodiment, the communication f! Since line switching control is performed by the earth stations K, 1 to Kn, conventional packet terminals such as packet terminals and protocol converters can be used as they are. Therefore, a highly versatile system can be constructed without requiring major configuration changes.

However, the present invention is not limited to the above embodiments. For example, in the above embodiment, communication line switching control is performed at the earth station, but if the packet type terminal is directly connected to the communication line, the packet type terminal may be provided with line switching control means. Furthermore, even if the packet type terminal is directly connected to the communication line, a line interface may be provided between the packet type terminal and the communication line, and the line switching control may be performed through this line interface. Furthermore, the communication system may be one that uses a terrestrial communication line in addition to one that uses a satellite communication line, and the gist of the present invention also covers other packet transmission procedures, control procedures and control contents of line connection control means, etc. Various modifications can be made without departing from the above.

[Effects of the Invention] As described in detail above, according to the present invention, in a state where a logical channel is set, a communication partner's packet format terminal is connected via a communication line without going through a packet switch, and this immunity is achieved. By transmitting data packets to and from the communication partner's packet format terminal via the communication line, the amount of packets handled by the packet switch is reduced and the load is reduced. It is possible to provide a packet communication method that can improve exchange efficiency.

[Brief explanation of drawings]

Figures 1 to 3 are for explaining the packet communication system of the present invention. Figure 1 is a schematic configuration diagram of a satellite packet communication system to which the same system is applied, and Figure 2 is a diagram of the packet communication system. FIG. 3 is a diagram showing an example of the structure of a data packet, and FIG. 4 is a diagram showing an example of the structure of a conventional packet transmission system. X...Packet switch, T1-Tn...Trunk,
P1 to Pn...Packet format terminal, PT...Packet terminal, PAD...Protocol conversion device, S...Communication satellite, HUB, Kl to Kn...Earth station, Ka...
Line switching control means, CHI to CHn, CHj...satellite communication channels. 1

Claims (2)

[Claims] (1) Comprising a packet switch and a plurality of packet-type terminals connected to the packet switch via a first communication line, each of the packet-type terminals communicating with the packet switch when making/receiving and disconnecting calls. a logical channel setting/opening control means for setting and releasing a logical channel by exchanging control packets via the first communication line; and a packet format terminal of a communicating party in a state where the logical channel is set. a line connection control means for connecting between the two via a second communication line not via the packet switch, and a packet type terminal of the communication partner via the second communication line connected by the line connection control means. 1. A packet communication system comprising: a data packet transmission control means for transmitting data packets between data packets. (2) comprising a packet switch, a plurality of packet format terminals connected to the packet switch via a first communication line, and a line connection control device provided corresponding to each of these packet format terminals, The line connection control device includes:
a control packet transmission means for transmitting control packets transmitted and received by the packet type terminal to and from the packet switching equipment via the first communication line during call origination/reception and disconnection of a corresponding packet type terminal; and a corresponding packet type; In order to connect a line connection control device corresponding to a communication partner packet type terminal with a logical channel set between the terminal and the packet switch via a second communication line that does not go through the packet switch. 1. A packet communication system comprising: a line connection means; and a data packet transmission means for transmitting data packets sent and received by a packet-type terminal via the second communication line.