JP2999033B2 - Packet relay method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet relay system for performing a packet call connection between terminal accommodation stations via a relay station.

[0002]

2. Description of the Related Art Conventionally, as a packet relay system in which packet information is transferred from a terminal accommodating station via a relay station using an ISDN communication network, a packet is transmitted using a dedicated ISDN line for transmitting a call setting request to the relay station. A packet-switched link-by-link relay system for making a call connection has been adopted.

FIG. 2 shows a configuration example of a conventional ISDN communication network for transferring packet information by the above-described packet relay system.

In the figure, reference numeral 1 denotes a time-division switch, 2 denotes a terminal accommodating device that accommodates a terminal device 5A (or 5B) via an I interface (user / network interface), and 3 denotes an ISDN via the I interface. This is a dedicated line accommodation device that accommodates the dedicated line 10. Reference numeral 4 denotes a time division multiplex highway for connecting the terminal accommodating apparatus 2 and the time division switch 1 by time division multiplexing or connecting the leased line accommodation apparatus 3 and the time division switch 1 by time division multiplexing. Reference numeral 6 denotes a control bus for transmitting a call control signal from the terminal accommodating device 2 or the leased line accommodating device 3, reference numeral 7 denotes an exchange control processing device for controlling exchange processing based on the call control signal, and reference numeral 8
Is an exchange control processing control bus that connects the exchange control processing device 7 to each device, 9 is a packet processing device that executes a protocol process for transferring packet information, 11A is a first terminal accommodation station, and 12 is a relay. The station 11B is a second terminal accommodation station. In FIG. 2, the dashed-dotted signal path indicates a path for packet information, and the dashed signal path indicates a path for signals other than packet information.

FIG. 3 shows an example of a call connection sequence of a packet call in an ISDN communication network using the above-mentioned relay system. In this example, the first terminal accommodation station 11A in FIG.
From the relay station 12 to the second terminal accommodation station 11B.

First, in the first terminal accommodating station 11A, when a SETUP message is sent to the terminal accommodating apparatus 2 from the terminal apparatus 5A accommodated therein, the terminal accommodating apparatus 2 receiving the SETUP message changes the exchange control. A call setting request is made to the processing device 7 (reference (a) in FIG. 3). Then, the switching control processor 7 responds to the call setting request by the packet processor 9
Is selected, a call setting request is sent to the packet processing device 9, and the terminal device 5 is sent to the terminal accommodation device 2.
This suggests ISDN protocol processing for A (reference (a) in FIG. 3). Then, when the ISDN protocol processing for the terminal device 5A is completed (codes (c) and (d) in FIG. 3), the packet processing device 9 sends the call request packet (from the terminal device 5A via the terminal accommodation device 2). CR) (code (e) in FIG. 3), and notifies the exchange control processing device 7 of an incoming call (code (f) in FIG. 3). Then, the exchange control processing device 7 having received the incoming call notification executes the route selection and
And outputs a call setting request to the selected relay station 12 to the leased line accommodating apparatus 3 (code (g) in FIG. 3). The leased line accommodating device 3 sends a SETUP message to the leased line accommodating device 3 of the relay station 12 in accordance with the call setting request.
Send a message.

On the other hand, in the relay station 12, when the dedicated line accommodating device 3 for the terminal accommodating station 11A receives the SETUP message, the dedicated line accommodating device 3 issues a call setting request to the switching control processing device 7. Then, the switching control processing device 7 selects the packet processing device 9 according to the call setting request, makes a call setting request to the packet processing device 9, and sends a call setting request to the dedicated line accommodating device 3 for the terminal accommodation station 11A. Indicates the ISDN protocol processing for the terminal accommodating station 11A ((c) in FIG. 3). When the ISDN protocol processing for the terminal accommodating station 11A is completed (FIG. 3).
, The dedicated line accommodating device 3 of the terminal accommodating station 11A.
Confirms the call setting to the exchange control processing device 7 of its own station (FIG. 3).
The exchange control processing device 7 of the terminal accommodation station 11A sends an acknowledgment to the packet processing device 9 of its own station (code (c) in FIG. 3). Then, the terminal accommodation station 11
The packet processing device 9 of A transmits from the dedicated line accommodating device 3 in the terminal accommodation station 11A to the ISDN dedicated line 10, and further,
The call request packet (C) is sent to the packet processing device 9 in the relay station 12 via the leased line accommodation device 3 in the relay station 12 or the like.
N) (symbol (S) in FIG. 3). Then, the packet processing device 9 of the relay station 12 notifies the exchange control processing device 7 of the local station of the incoming call (reference (S) in FIG. 3). As a result, the switching control processing device 7 of the relay station 12 selects a terminal accommodation station 11B as the final destination by performing route selection, and sends a call setting request to the selected terminal accommodation station 11B to the dedicated line accommodation device. 3 is output (reference (f) in FIG. 3). The leased line accommodating device 3 responds to the call setting request by the terminal accommodating station 11.
A SETUP message is transmitted to the leased line accommodation device 3 of B.

In the second terminal accommodating station 11B, when the dedicated line accommodating device 3 for the relay station 12 receives the SETUP message, the dedicated line accommodating device 3 issues a call setting request to the switching control processing device 7. Then, the switching control processing device 7 selects the packet processing device 9 according to the call setting request, makes a call setting request to the packet processing device 9, and sends a call setting request to the dedicated line accommodating device 3 for the relay station 12. This suggests ISDN protocol processing to the relay station 12 ((S) in FIG. 3).

When the ISDN protocol processing for the relay station 12 is completed (reference numeral (t) in FIG. 3), the relay station 12
The dedicated line accommodating device 3 confirms the call setting to its own switching control processing device 7 (reference numeral (h) in FIG. 3), and the switching control processing device 7 of the relay station 12 responds to the packet processing of its own station. An acknowledgment response is sent to the device 9 (reference numeral (T) in FIG. 3). Then, the packet processing device 9 of the relay station 12 changes the leased line accommodation device 3 in the relay station 12 to the ISDN leased line 10, and further,
Via the dedicated line accommodation device 3 or the like in the terminal accommodation station 11B,
A call request packet (CN) is transmitted to the packet processing device 9 in the terminal accommodating station 11B (code (T) in FIG. 3). Then, the packet processing device 9 of the terminal accommodating station 11B notifies the switching control processing device 7 of its own station of an incoming call (code (g) in FIG. 3). As a result, the switching control processor 7 of the terminal accommodating station 11B determines the terminating terminal and outputs a call setting request to the terminal accommodating apparatus 2 of the own station because the own station is the terminal accommodating station of the final destination. Then, the terminal accommodating device 2 that has received the output request outputs a SETUP message to the terminal device 5B of the final destination (reference numeral (n) in FIG. 3).

[0010] Then, via a response between the terminal device 5B and the terminal accommodating device 2 (codes (d) and (nu) in FIG. 3), the call setting of the exchange control processing device 7 of the terminal accommodating station 11B is confirmed ( The code (f) in FIG. 3), and further, an acknowledgment response from the switching control processing device 7 to the packet processing device 9 (code (no) in FIG. When the incoming call request packet (CN) is transmitted (symbol (c) in FIG. 3), the terminal device 5A of the terminal accommodation station 11B is changed from the terminal device 5A of the terminal accommodation station 11A to the final destination.
The call connection of the packet call up to B is completed (reference (h) in FIG. 3), and the subsequent substantial data transfer becomes possible.

Incidentally, the conventional example shown in FIGS. 2 and 3 is as follows.
In the case where the terminal is connected to the target terminal accommodation station via one relay station, when a plurality of relay stations are interposed to the target terminal accommodation station, both the ISDN protocol processing and the packet protocol processing are performed. (For example, in FIG. 3, reference numerals (se), (so), (ta), (h), (tsu),
(A series of processing shown in (T)) is repeated for each adjacent relay station.

[0012]

However, when a call connection of a packet call is performed by the above-mentioned conventional packet relay system, all of the ISDN between the terminal accommodating station and the relay station or between the relay stations is performed. Since it is necessary to perform both the ISDN protocol processing and the packet protocol processing using the dedicated line, there are the following problems (1) and (2).

(1) At the stations (terminal accommodating stations and relay stations) involved in the packet transfer, the leased line accommodating devices 3, I
If any one of the SDN dedicated line 10 and the packet processing device 9 is not mounted or has a failure, the call connection of the packet call becomes impossible, the packet call becomes a call loss, and the quality of the communication network is degraded. .

(2) When non-ISDN relay stations are mixed in a communication network to be used, the range in which the packet relay function is provided is limited to a range excluding the non-ISDN relay stations, which imposes restrictions on the construction of the communication network.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents the quality of a communication network from deteriorating due to a call loss of a packet call, and secures a packet relay function for a non-ISDN relay station in an ISDN network. It is an object of the present invention to provide a packet relay system that can perform the packet relay.

[0016]

A packet relay system according to the present invention establishes a call connection of a packet call between terminal accommodation stations via a relay station. A common line signal processing device for transmitting a call setting request required for call connection via a common line signal control line, and a dedicated line accommodation device for transmitting a call request packet required for call connection via a dedicated line. A packet processing device for executing a protocol process for transferring packet information, and an exchange control processing device for controlling exchange processing by these common line signal processing device, dedicated line accommodating device and packet processing device. .

Further, the switching control processor treats the common line signal processor, the dedicated line accommodating device and the packet processor as a terminal device to be call-connected virtually, and connects these virtual terminal devices to each other. A virtual terminal control unit connected by a link is provided.

In the virtual terminal control unit, the ISD
By accommodating multiple protocols such as N protocol, packet protocol, common channel signal protocol,
An arbitrary protocol process can be selected for each virtual link set between the virtual terminal devices, and two of the two packet relay systems, a link-by-link relay system in a packet-switched mode and a link-by-link relay system in a circuit-switched mode, are selected. A call connection of a packet call is performed by selecting and using one that is suitable for the communication situation.

However, the link-by-link relay system in the circuit switching mode refers to a system for performing a call connection of a packet call using a common channel signal control line for transmitting a call setup request.
The link-by-link relay method in the packet switching mode refers to a method of performing a call connection of a packet call using an ISDN leased line for transmitting a call setting request.

[0020]

In the packet relay system according to the present invention, in the exchange serving as a station for transmitting a packet call, a link-by-link relay system in a packet-switching mode or a link-by-link relay system in a circuit-switching mode depends on the communication situation. Either of the dedicated line accommodating device and the ISDN dedicated line and the packet processing device in the exchange is not mounted or is in failure and the link-by-link relay system in the packet switching mode is used. In the event that it becomes impossible to realize, by controlling the common line signal processing device, it is possible to realize the link-by-link relay system in the circuit switching mode, and to prevent the quality deterioration of the communication network due to the packet loss of the packet call. it can.

When non-ISDN relay stations are mixed in a communication network to be used, the non-ISDN relay station is also used as a packet relay station by using a link-by-link relay method in a circuit switching mode. Thus, the restriction on the construction of the communication network for the call connection of the packet call can be eliminated.

[0022]

1 and 4 show examples of the configuration of a communication system which executes a packet relay system according to an embodiment of the present invention. In addition, about the structure common to the conventional example shown in FIG. 2, description is abbreviate | omitted or simplified by attaching the same number. In the communication systems shown in FIG. 1 and FIG. 4, both of the communication systems shown in FIGS. 1 and 4 perform the call connection of the packet call from the terminal device of the first terminal accommodation station to the terminal device of the second terminal accommodation station via the relay station. In this case, there is a difference in the configuration of the relay station and the like, which causes a difference in the call connection sequence of the packet call according to the embodiment of the present invention.

In the communication system shown in FIGS. 1 and 4, reference numeral 20 denotes a first terminal accommodating station, 21 and 22 denote relay stations, and 23 and 24 denote second terminal accommodating stations. Also, 30
Is a non-ISDN leased line, 31 is the non-ISDN leased line 30
Is an exchange control processing device that controls the exchange process based on the call control signal. Reference numeral 35 denotes a common line signal processing device for controlling the non-ISDN leased line accommodating device 31 and for controlling a signal such as a call connection by a circuit switching system (common line signal system). This is a common line signal control line that connects between them. In FIGS. 1 and 4, a dashed-dotted signal path indicates a packet information path, and a dashed signal path indicates a signal path other than packet information.

In the communication system shown in FIGS. 1 and 4, each terminal accommodating station and each relay station function as a packet switch.
No. 0 has all the necessary components as an exchange for executing the relay system of one embodiment of the present invention.

That is, as shown, the first terminal accommodating station 20 includes a time-division switch 1, a terminal accommodating device 2 accommodating the terminal device 5A via the I interface, and the non-ISDN
A dedicated line accommodating device 31 accommodating the dedicated line 30, a time division multiplex highway connecting the terminal accommodating device 2 and the time division switch 1 and the dedicated line accommodating device 31 and the time division switch 1 by time division multiplexing. 4, a control bus 6 for transmitting a call control signal from the terminal accommodating device 2 or the dedicated line accommodating device 31, an exchange control processor 32 for controlling an exchange process based on the call control signal, and the exchange control processor 32 It includes an exchange control processing control bus 8 for connecting devices, a packet processing device 9 for executing a protocol process for transferring packet information, and the like.
5 and a common line signal control line 36.

The exchange control processor 32 includes:
The common line signal processing device 35, the dedicated line accommodating device 31, and the packet processing device 9 are virtually treated as terminal devices to be connected to a call, and the first and the second linking these virtual terminal devices to each other for a call connection. A second virtual terminal control unit (see reference numerals 41, 42, 43, 44, 45, 46 in FIG. 5) is provided.

Each virtual terminal control unit accommodates an ISDN protocol, a packet protocol, and a common channel signal protocol. As a packet relay system for performing a call connection of a packet call, a link-by-link relay system in a packet switching mode, Any of the exchange mode link-by-link relay method can be selectively used.

Here, the link-by-link relay system in the packet switching mode refers to a system in which a call connection of a packet call is performed using an ISDN dedicated line for transmitting a call setting request to a relay station or the like. The link-by-link relay system in the circuit switching mode refers to a system in which a call connection request for a packet call is transmitted using a common channel signal control line for transmitting a call setting request to a relay station or the like.

In this virtual terminal control unit, after setting up a virtual link (end-to-end communication link in a virtual state) between the virtual terminal apparatuses, the mounting state and the failure state of the apparatus in its own station are analyzed. It recognizes which of the above two packet relay systems is available. If both packet relay systems are available, based on the priorities of the relay systems set in the exchange control processor 32 in advance,
Determine the packet relay method to be used.

The procedure of call connection of a packet call in the communication system shown in FIGS. 1 and 4 will be described below with reference to FIGS.
It will be described based on.

FIG. 5 shows a call connection procedure in the packet relay system according to one embodiment of the present invention, mainly for the operation of the virtual terminal control unit of the switching control processor 32, in the case of the system of FIG. Things.

First, from the terminal device 5A accommodated in the first terminal accommodation station 20 to the terminal device 5 accommodated in the second terminal accommodation station 23,
The switching control processing device 32 of the first terminal accommodation station 20 receives the call setting request to B through the lower layer. Then, the exchange control processing device 32 recognizes the protocol type of the lower layer, and activates the first virtual terminal control unit 41 in order to set up a call with the terminal device 5A according to the protocol.

Then, the virtual terminal controller 41 controls the establishment of the virtual link T1 with the terminal device 5A, determines a route based on the result of the number translation, and selects a relay system for the route. I do.

The procedure for selecting the relay system is as follows. First, the mounting state and the failure state of the dedicated line accommodating device in the local station, the dedicated line terminated in the dedicated line accommodating device, the packet processing device, and the like are analyzed. Check the relay method that can be used for the corresponding route determined earlier. Specifically, it is determined whether the link-by-link relay system in the circuit switching mode or the link-by-link relay system in the packet switching mode can be used according to the mounting state or the failure state of the device. If both of these relay systems can be used, the relay system to be used is selected based on the relay system priority set in the exchange control processing device 32 in advance. Then, the second virtual terminal control unit 42 is activated in order to set up a call to the relay station 21 in the selected relay system.

The virtual terminal control unit 42 includes a virtual terminal control unit 4
After controlling the establishment of the virtual link T2 with the relay station 1, the lower protocol of the corresponding relay system is controlled, and a call setting request is transmitted to the relay station 21. Then, the exchange control processing device 32 in the relay station 21 receives this through the lower layer, recognizes the protocol type of the lower layer, and performs the first virtual setting in order to set up a call with the virtual terminal controller 42 in the corresponding protocol. The terminal control unit 43 is started.

The virtual terminal control unit 43 performs establishment control of the virtual link T3 with the virtual terminal control unit 42,
A route is determined based on the result of the number translation, and the same procedure as in the case of the virtual terminal control unit 41 is used to determine the mounting state and failure state of the device in the station and the relay method priority set in the exchange control processing device 32 in advance. Based on the order and the like, a relay system to be used for the corresponding route is selected. Then, the virtual terminal control unit 44 is activated in order to set up a call to the terminal accommodation station 23 in the selected relay system.

The virtual terminal control unit 44 includes the virtual terminal control unit 4
3, the control of the lower link protocol of the corresponding relay system is performed, and the terminal accommodation station 2
3 is transmitted. Then, the switching control processor 32 in the terminal accommodating station 23 receives this through the lower layer, recognizes the protocol type of the lower layer, and performs the first setting in order to set up a call with the virtual terminal controller 44 in the corresponding protocol. The virtual terminal control unit 45 is started.

The virtual terminal control unit 45 performs establishment control of the virtual link T5 with the virtual terminal control unit 44, and then determines the terminal device 5B of the receiving terminal based on the result of the number translation, and determines the terminal device 5B. The virtual terminal control unit 46 is activated in order to set up a call with respect to.

The virtual terminal control unit 46 includes the virtual terminal control unit 4
After the control of establishing the virtual link T6 with the terminal device 5B, the lower protocol type of the terminal device 5B is recognized, and the establishment of the virtual link T7 with the terminal device 5B is controlled by the corresponding protocol.

Thereafter, the virtual terminal controller 46, the virtual terminal controller 45, the virtual terminal controller 44, the virtual terminal controller 43,
The response is transmitted in the order of the virtual terminal control unit 42 and the virtual terminal control unit 41, and the virtual links are connected to each other, whereby the call setting between the terminal devices 5A and 5B is completed.

As described above, in the case of the system shown in FIG. 1, a call connection is established between the terminal accommodating station 20 and the relay station 21 by a link-by-link relay system in a circuit switching mode, and the relay station 21 and the terminal accommodating station 23 are A call connection is made by a link-by-link relay method in an exchange mode.

In FIG. 5, L1, L2, and L3 are assigned to the respective protocols accommodated in the respective virtual terminal controllers, but L1 indicates Layer 1 in the OSI open system model, and L2 indicates L1. Indicates Layer 2 in the OSI open system model, and L3 indicates Layer 3 in the OSI open system model. Although not shown in detail, in the case of the system shown in FIG. 4, all the stations are connected by the link-by-link relay method in the circuit switching mode via the same virtual link connection.

Next, the procedure of the call connection of the packet call in the system shown in FIGS. 1 and 4 will be described in detail with reference to FIGS. 6 and 7.

FIG. 6 shows a call connection sequence of a packet call for the system of FIG. The system shown in FIG. 1 is a case in which a call connection of a packet call is performed by mixing the link-by-link relay system in the circuit switching mode and the link-by-link relay system in the packet switching mode.

First, in the terminal accommodating station 20, the terminal accommodating apparatus 2 which has received the SETUP message from the terminal apparatus 5A issues a call setting request to the exchange control processing apparatus 32 (reference numeral (a) in FIG. 6). Then, the exchange control processing device 32
The packet processing device 9 is selected by the call setting request,
A call setting request is made to the corresponding packet processing device 9 and call setting reception confirmation is made to the terminal accommodating device 2 (code (a) in FIG. 6). Then, the packet processing device 9
Outputs the call setting confirmation to the exchange control processor 32,
When a call request packet (CR) from the terminal device 5A is received (reference numerals (c), (d), and (e) in FIG. 6), an incoming call notification is sent to the exchange control processor 32 (reference code (c) in FIG. 6). )).
Then, the exchange control processor 32 receiving the incoming call notification
Executes the route selection to select the relay station 21, and sends a call setting request to the selected relay station 21 to the common line signal processing device 3.
5 to the relay station 21 (reference numeral (g) in FIG. 6).

On the other hand, in the relay station 21, when the switching control processor 32 receives the call setting request from the terminal accommodating station 20 via the common channel signal processor 35, it performs the route selection. Then, the switching control processing device 32 transmits the call setting request to the packet processing device 9 ((c) in FIG. 6), and confirms the call setting from the packet processing device 9 (FIG. 6).
To the common line signal processing unit 35.
Then, the common line signal processing device 35 is
The call setting confirmation is transmitted to the common line signal processing device 35 of
The common line signal processing device 35 of the terminal accommodating station 20 notifies the switching control processing device 32 of the local station of the call setting confirmation ((C) in FIG. 6). Then, the exchange control processor 32 of the terminal accommodating station 20 sends a confirmation response to the packet processing apparatus 9 of its own station (reference numeral (c) in FIG. 6), and relays from the packet processing apparatus 9 of the terminal accommodating station 20. Packet processing device 9 in station 21
Then, a call request packet (CN) is transmitted to the server (reference numeral (S) in FIG. 6). The packet processing device 9 of the relay station 21 that has received the incoming call request packet (CN) notifies the exchange control processing device 32 of its own station of the incoming call (code (S) in FIG. 6). As a result, the exchange control processing device 32 of the relay station 21 outputs a call setting request to the terminal accommodating station 23 selected in the previous route selection to the leased line accommodating device 3 (reference numeral in FIG. 6). (S)). The leased line accommodating device 3 sets the leased line accommodating device 3 of the terminal accommodating station 23 in accordance with the call setting request.
Send an UP message.

In the terminal accommodating station 23, the leased line accommodating apparatus 3 which has received the SETUP message from the relay station 21 issues a call setting request to the switching control processing apparatus 32 of the own station. Then, the switching control processing device 32 issues a call setting request to the packet processing device 9 and confirms the call setting reception to the leased line accommodating device 3 ((G) in FIG. 6). Then, the exchange control processing device 32 that has received the call setting confirmation (reference numeral (t) in FIG. 6) from the packet processing device 9 outputs a call setting instruction to the leased line accommodation device 3. And the relay station 21
On the side, when the exchange control processing device 32 receives the call setting confirmation from the leased line accommodating device 3 (code (h) in FIG. 6), the exchange control processing device 32 sends an acknowledgment response to the packet processing device 9 of its own station. (Refer to FIG. 6). Then, the relay station 21
The packet processing device 9 in the terminal accommodation station 23 transmits the packet in the terminal accommodation station 23 from the leased line accommodation device 3 in the relay station 21 to the ISDN leased line 10 and further through the leased line accommodation device 3 in the terminal accommodation station 23. Incoming request packet (C
N) (symbol (te) in FIG. 6). Then, the packet processing device 9 of the terminal accommodating station 23 notifies the switching control processing device 32 of its own station of the incoming call (reference (g) in FIG. 6). As a result, the exchange control processing device 32 of the terminal accommodation station 23
Since the own station is the terminal accommodating station of the final purpose, it determines the destination terminal, outputs a call setting request to the terminal accommodating apparatus 2 of the own station, and the terminal accommodating apparatus 2 which has received the output request makes the final objective. The SETUP message is output to the terminal device 5B (see (n) in FIG. 6). Then, a response between the terminal device 5B and the terminal accommodating device 2 (reference numeral (d) in FIG. 6,
(V)) The exchange control processor 32 of the terminal accommodation station 23
The call setting is confirmed (reference (f) in FIG. 6), and furthermore, after waiting for an acknowledgment response from the switching control processing device 32 to the packet processing device 9 (reference (no) in FIG. 6), the packet processing device 9 sends the final purpose. When the call request packet (CN) is transmitted to the terminal device 5B of the terminal (5) in FIG. 6 (from (c) in FIG. 6), the terminal device 5A of the terminal accommodation station 20 to the terminal device 5B of the terminal accommodation station 23 of the final destination. The call connection of the packet call is completed ((h) in FIG. 6), and the subsequent substantial data transfer becomes possible.

FIG. 7 shows a call connection sequence of a packet call for the system of FIG. The system shown in FIG. 4 is a case in which a call connection of a packet call is performed by only the link-by-link relay system in the circuit switching mode among the two packet relay systems described above.

First, in the terminal accommodating station 20, the terminal accommodating apparatus 2 which has received the SETUP message from the terminal apparatus 5A issues a call setting request to the exchange control processing apparatus 32 (reference numeral (a) in FIG. 7). Then, the exchange control processing device 32
The packet processing device 9 is selected by the call setting request,
A call setting request is made to the packet processing device 9 and a call setting reception confirmation is made to the terminal accommodating device 2 (reference (a) in FIG. 7). Then, the packet processing device 9
Outputs the call setting confirmation to the exchange control processor 32,
When a call request packet (CR) from the terminal device 5A is received (codes (c), (d), and (e) in FIG. 7), an incoming call notification is sent to the exchange control processing device 32 (code (c) in FIG. 7). )).
Then, the exchange control processor 32 receiving the incoming call notification
Executes the route selection to select the relay station 22, and transmits a call setting request to the selected relay station 22 to the common line signal processing device 3.
5 to the relay station 22 (reference (g) in FIG. 7).

On the other hand, in the relay station 22, when the exchange control processing device 32 receives the call setting request from the terminal accommodating station 20 via the common channel signal processing device 35, it performs route selection. Then, the switching control processing device 32 transmits the call setting request to the common channel signal processing device 35 ((C) in FIG. 7). Then, the common line signal processing device 3 of the relay station 22
5 through the common line signal processing device 35 of the terminal accommodating station 24, the call setting request is notified to the exchange control processing device 32 of the relay station 22, and the exchange control processing device 32 of the terminal accommodating station 24 determines the destination terminal. Then, the call setting request is notified to the packet processing device 9 of the terminal accommodating station 24 (code (q) in FIG. 7).

When the switching control processing device 32 of the terminal accommodating station 24 receives the call setting confirmation from the packet processing device 9 of the own station (reference symbol (c) in FIG. 7), it exchanges it with the common line signal processing of the own station. Notify the device 35. The call setting confirmation notified to the common line signal processing device 35 of the terminal accommodating station 24 is performed by using the common line signal control line by using the exchange control processing device 32 of the relay station 22 and the exchange control processing device of the terminal accommodating station 20. 32 in that order. When the exchange control processing device 32 of the terminal accommodating station 20 responds to the packet processing device 9 of the local station in response to the reception of the call setting confirmation (reference (c) in FIG. 7), the non-ISDN dedicated line 30 is connected. Using this, an incoming call request packet (CN) is transmitted from the packet processing device 9 of the terminal accommodating station 20 to the packet processing device 9 of the terminal accommodating station 24 via the relay station 22 (code (S) in FIG. 7). . The packet processing device 9 of the terminal accommodating station 24 that has received the incoming call request packet (CN) notifies the exchange control processing device 32 of the local station of the incoming call (code (S) in FIG. 7). As a result, the exchange control processing device 32 of the terminal accommodation station 24 outputs a call setting request to the terminal accommodation device 2 of its own station based on the previously determined destination terminal, and receives the call setting request request. The terminal accommodating device 2 outputs the SETUP message to the terminal device 5B of the final purpose (reference (c) in FIG. 7). Then, via the response between the terminal device 5B and the terminal accommodating device 2 (symbols (S) and (T) in FIG. 7), the call setting confirmation for the exchange control processing device 32 of the terminal accommodating station 24 is performed. Waiting for an acknowledgment (indicated by (h) in FIG. 7) from the processing device 32 to the packet processing device 9, the packet processing device 9 calls the incoming request packet (CN) to the terminal device 5B as the final destination.
Is transmitted (reference symbols (T) and (T) in FIG. 7), the terminal device 5A of the terminal accommodating station 20 transmits the final target terminal accommodating station 24.
The call connection of the packet call to the terminal device 5B is completed (reference (g) in FIG. 7), and the subsequent substantial data transfer becomes possible.

In the packet relay system according to one embodiment of the present invention described above, for example, in the terminal accommodation station that originates a packet call, the leased line accommodation device 3, the ISDN leased line 1
0, if any one of the packet processing devices 9 is not mounted or is in failure and the link-by-link relay method in the packet switching mode cannot be realized, the common line signal processing device 35
, It is possible to realize a link-by-link relay system in a circuit switching mode, and to prevent deterioration of the quality of a communication network due to a call loss of a packet call.

When a non-ISDN relay station is mixed in a communication network to be used, the non-ISDN relay station is used as a packet relay station by using a link-by-link relay method in a circuit switching mode. Thus, the restriction on the construction of the communication network for the call connection of the packet call can be eliminated.

In the communication systems shown in FIGS. 1 and 4, the exchange serving as the station for executing the present invention is the first terminal accommodating station 20, but the present invention is not limited to the relay station or the second terminal accommodating station. It can also be used in stations.

Further, in the embodiment, the case where the number of relay stations is one has been described, but the present invention can be effectively used even when there are a plurality of relay stations.

[0056]

As is apparent from the above description, in the packet relay system according to the present invention, in the exchange serving as a station transmitting a packet call, the link-by-link relay in the packet switching mode is performed according to the communication situation. System or circuit-switched mode link-by-link relay system can be selectively used. For example, any of the dedicated line accommodating device, the ISDN dedicated line, and the packet processing device in the exchange are not installed or are in failure. If the link-by-link relay method in the packet switching mode becomes impossible to realize,
By controlling the common line signal processing device, a link-by-link relay system in a circuit switching mode can be realized, and deterioration of the quality of a communication network due to a call loss of a packet call can be prevented.

When a non-ISDN relay station is mixed in a communication network to be used, the non-ISDN relay station is used as a packet relay station by using a link-by-link relay method in a circuit switching mode. Thus, the restriction on the construction of the communication network for the call connection of the packet call can be eliminated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first communication system that executes an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional communication system.

FIG. 3 is a packet call connection sequence diagram according to a conventional packet relay system.

FIG. 4 is a configuration diagram of a second communication system that executes one embodiment of the present invention.

FIG. 5 is an explanatory diagram of a call connection process in one embodiment of the present invention.

FIG. 6 is a packet call connection sequence diagram according to an embodiment of the present invention.

FIG. 7 is a packet call connection sequence diagram according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Time division switch 2 Terminal accommodating device 3, 31 Dedicated line accommodating device 4 Time division multiplex highway 5A, 5B terminal device 6 Control bus 8 Exchange control processing device bus 9 Packet processing device 10 ISDN exclusive line 20, 23, 24 Terminal accommodating station 21, 22 relay station 30 non-ISDN leased line 32 exchange control processing unit 35 common line signal processing unit 36 common line signal control line 41 to 46 virtual terminal control unit T1 to T7 virtual link

Claims (1)

(57) [Claims] 1. A packet relay system for establishing a call connection of a packet call between terminal accommodation stations via a relay station, wherein an exchange serving as a station for transmitting the packet call receives a call setting request required for the call connection. A common line signal processing device for transmitting via a common line signal control line, a dedicated line accommodating device for transmitting a call request packet required for call connection via a dedicated line, and a protocol for transferring packet information Equipped with a packet processing device that executes processing, and an exchange control processing device that controls exchange processing by these common line signal processing device, dedicated line accommodating device, and packet processing device, and the exchange control processing device includes: A virtual terminal control unit that treats the common line signal processing device, the dedicated line accommodating device, and the packet processing device virtually as terminal devices to be call-connected, and connects these virtual terminal devices to each other by a virtual link. The virtual terminal control unit accommodates a plurality of protocols such as an ISDN protocol, a packet protocol, and a common channel signal protocol, thereby enabling arbitrary protocol processing to be selected for each virtual link set between the virtual terminal devices. A link-by-link relay system in a circuit switching mode for making a call connection of a packet call using a common channel signal control line for transmitting a call setup request, and a packet call using an ISDN dedicated line for sending a call setup request. Packet connection characterized by performing a call connection for a packet call by selecting and using one of two packet relay systems, which is a packet exchange mode link-by-link relay system for making a call connection, and a communication condition. Relay method.