JPS61242437A - Call setting control system for pvc call between stations - Google Patents

Abstract

PURPOSE:To reduce ineffective packet traffic between stations by transmitting an origination change information packet to the opposite station when a VC connection can not be set between exchanges, and then starting VC connection processing between the exchanges when detecting an answer indicating a terminal recovers from a failure in communication from the opposite station. CONSTITUTION:An exchange 30 sends an origination request packet to an exchange 31, which when detecting a communication failure state between exchanges 31 and a terminal 21, returns a disconnection indication packet to the exchange together with an added disconnection code which indicates that the terminal is not ready. The exchange 30 after transmitting the origination change information packet to the exchange rewrites the contents of a PVC call control memory 40 provided corresponding to the local channel of a terminal 20 from a state wherein a VC connection is made between the exchangers after it originates by itself to a state in which the connection is made after a connection from the opposite station. Then, the VC connection processing between the exchanges is started when the answer indicating that the terminal recovers from a failure in communication is detected from the opposite station.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a call setup control system for PVO calls connected via a plurality of switching centers in a packet switching network.

(Prior art) PVC call is Permanent Virtua40ir
Cult) is a packet switching function that allows a terminal to send and receive data without performing call setup or call recovery procedures.

In a packet switching network where communication between packet switching centers has been defined by the X75 communication protocol, when setting up a PVC call between terminals via multiple switching centers,
Communication is performed between the terminal and the switching center in PVC mode, and VC mode (Virtual Call Mode) is established between the switching centers.
) is a method for communicating. Here, the VC mode is a Kerato switching function that requires processing procedures for connection and recovery of calls when transmitting and receiving data.

In this type of system, it is necessary to establish a VC connection between exchanges that accommodate each terminal, but it is a complicated procedure for each exchange to start VC connection processing toward the other station. It takes. Therefore, in general, one of the switching stations is defined as the primary station and the other 'f: secondary station, and VC connection processing is performed from the primary station to the secondary station. If the power of the terminal housed in the secondary station is cut off when a VC connection is started from the primary station, communication between the secondary station and the terminal becomes impossible, and the VC connection between the two stations is interrupted. is not set. For this reason, according to the prior art, the primary station periodically executes VC connection processing toward the secondary station until a terminal accommodated in the secondary station becomes able to communicate. The example of the Nokkerato sequence shown in FIG. 3 is an explanatory diagram showing the above operation.

(Problems to be Solved by the Invention) In the above-described conventional call setup control system for PVC calls between stations, if the power of the terminal housed in the secondary station is cut off, communication becomes impossible. VC connection cannot be set between both stations. Therefore, VC connection processing is periodically performed from the primary station to the secondary station until the terminal accommodated in the secondary station becomes able to communicate, which has the disadvantage of increasing invalid traffic on the network. .

An object of the present invention is to notify the other station of a call change if the VC connection cannot be established between the exchanges because the terminal accommodated in the other station is unable to communicate when establishing a VC connection between the exchanges. When a packet is sent and a response is detected from the other station indicating that the terminal that is unable to communicate has recovered normally, the V between the stations is
Eliminate the above drawback by starting the 0 connection process,
An object of the present invention is to provide a call setup control system for PVC calls between stations configured to reduce invalid traffic.

(Means for Solving the Problems) The call setup control method for PVC calls between stations of the present invention requires that both switching stations that accommodate terminals make a VC connection between the stations themselves, or that the other party A memory table is provided for each station to display whether to wait for connection from
After sending a calling packet to the other station from an exchange that is set in the memory table to initiate a connection by itself, the other station sends a disconnection instruction packet indicating that the terminal accommodated in the other station is unable to communicate. When receiving this, it sends a calling change notification packet to the other station and rewrites the memory table of the other station to the content that the VC connection between the stations is made by calling itself.
It is configured so that the memory table of the own station can be rewritten with the contents of waiting for connection from the other station.

(Example) Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a call setup control method for PVC calls between stations according to the present invention. In FIG. 1, 20 and 21 are terminals, 30 to 32 are exchanges, and 40 and 41 are terminals 20 and 21, respectively.
This is a PVO call control memory provided corresponding to the logical channel.

In FIG. 1, there is a PVC between terminal 20 and terminal 21.
When setting up a call, communication between the terminal 20 and the switching center 30 and between the terminal 21 and the switching center 31 are performed using PVC.
communication between the exchange 30 and the exchange 31 is performed in the VC mode. The exchange 30 and the exchange 31 have
A PVC call control memo IJ40, 41 is provided corresponding to the PVC logical channel of the terminal 20 or terminal 21, respectively, and a VC connection between stations is established by making a call from the own station or by a connection from the other station. It stores data to display whether to wait or do so.

FIG. 2 is an explanatory diagram showing a packet sequence of the system shown in FIG. 1 according to an embodiment of the present invention. In FIG. 2, in order to establish a VC connection between the switching center 30 and the switching center 31, a call origination request (OR) is made from the switching center 30 to the switching center 31.
Send a packet. At this time, when the switching center 31 detects that communication is disabled between the switching center 31 and the terminal 21, the switching center 30Vt returns a disconnection instruction (01 packet) with a disconnection code indicating that the terminal cannot communicate. Send a reset instruction (RI) packet to the terminal 20,
Upon receiving the reset confirmation g (RF) packet from the terminal 20, it returns a disconnection confirmation (OF) packet to the switching center 31.

Next, the switching center 30 notifies the switching center 31 of a call change (FR).
) After transmitting the packet, the content of the PVC call control memory 40 provided corresponding to the logical channel of the terminal 20 shown in FIG. Rewrite the state to wait for connection from.

When the exchange 31 receives the calling change notification (PR) bucket l, it transfers the contents of the PVC call control memory 41 provided corresponding to the logical channel of the terminal 21 shown in FIG. 1 and waits for connection from the other station. VC between stations from the state where
The connection is rewritten to a state in which the connection is made by calling itself, and a call switching notification confirmation (FF) packet is returned to the switching center 30.

If the switching center 31 detects that communication is possible between the switching center 31 and the terminal 21, a call is made to the switching center 30 in order to establish a VC connection between the switching center 30 and the switching center 31 at this point. Request (OR) Bucket) 1 - Send. When the exchange 30 receives the call request (OR) packet, it returns a reset instruction (RI) packet to the terminal 20, and after receiving the reset confirmation (RF) packet from the terminal 20, it informs the exchange 31 that the connection is complete ( 00) Send a packet. When the exchange 31 completes the connection (receiving the 00 packet, it transmits a reset instruction (RI packet) to the terminal 2) and receives a reset confirmation (RF) packet from the terminal 21.

As explained above, in the following sequence, a PvC connection is established between the terminal 2o and the terminal 21, and data packets can be transmitted and received between the two terminals.

(Effects of the Invention) As explained above, the present invention is applicable when a VC connection cannot be established between exchanges because the terminal accommodated in the other station is unable to communicate when establishing a VC connection between exchanges. sends a call replacement notification packet to the other station, and when it detects a response from the other station indicating that the terminal that is unable to communicate has recovered normally, it starts VC connection processing between stations. This has the effect of being able to reduce invalid VC connection processing caused by this and the amount of invalid packet traffic between stations in such a situation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a call setup control method for PVO calls between stations according to the present invention. FIGS. 2 and 3 are explanatory diagrams showing examples of packet sequences according to the present invention and the prior art, respectively. 20, 21...Terminals 30 to 32...Switching center 40, 41...Memory patent applicant NEC Corporation representative Patent attorney Inoro Jusai 1 Zusai 2rs

Claims (1)

[Claims] PVC between multiple terminals connected via multiple exchanges
A packet switching network configured to perform PVC mode communication between the terminal and the switching center and to perform VC mode communication between the switching centers accommodating each terminal when a call is set up. In the PVC call setup control method used in This is a storage table that stores a memory table for displaying whether or not to wait for a connection from the other party, and in an exchange that is set in the memory table to automatically initiate a VC connection between the stations, the exchange When a disconnection instruction packet indicating a communication disabled state of a terminal accommodated in the partner station is received from the partner station after sending a calling packet to the partner station, a call change notification packet is sent to the partner station. rewriting the memory table of the partner station to the content that the VC connection between the stations is performed by calling itself, and rewriting the memory table of the own station to the content that the VC connection between the stations is performed by waiting for the connection from the partner station. A PVC spanning between stations characterized by being configured to allow
Call setup control method.