KR100252512B1 - Normal Call Setup for Packet Switching in Electronic Switching System - Google Patents

Abstract

PURPOSE: A method of setting up a normal call for packet exchanging in a full electronic exchange is provided to set up or cancel a call for the packet exchanging in the full electronic exchange, so as to quickly process a call setting or a call canceling process. CONSTITUTION: If an originating PLP(Packet Level Procedure) receives a CR(Call Request) packet from a DTE(Data Terminal Equipment), the PLP transmits a CR packet confirm request (CrPktValRQ) signal to an originating packet call processing(BPCC) block, and starts a timer(T200). If the PLP receives a CR packet confirm response(CrPktValRP) signal, the PLP starts a timer(T220) and transmits a CR packet to other side. A receiving call packet confirm request(IcPktValRQ) signal is transmitted to a receiving BPCC block, and a timer(T300) is started. If a receiving call packet confirm response(IcPktValRP) signal is received from the receiving BPCC block, an incoming call packet(IC) is transmitted to a receiving DTE, and a timer(T310) is started. If a CA(Call Accept) packet is received from the receiving DTE, a CA packet confirm request(CaPktValRQ) signal is transmitted to the receiving BPCC block, and a timer(T320) is started. A data active state(DataActState) is converted when the CA packet confirm request(CaPktValRQ) signal is received. A CA packet is transmitted to a PLP of an originating exchange. The PLP transmits a call connection packet confirm request(CcPktValRQ) signal to the originating BPCC block, and starts a timer(T230). If a call connection packet confirm response(CcPktValRP) signal is received, a CC(Call Connection) packet is transmitted to an originating DTE, and a data active state(DataActState) is transitted.

Description

Method of establishing nomal call for packet switching

The present invention relates to a method for setting up and tearing down a normal call in an electronic switch that provides packet switching.

As is well known, the switching functions are broadly classified into circuit switching for normal telephone service and packet switching for data communication. In order to satisfy various services required by the user, the existing switching circuit can accommodate the packet switching function. Is gradually being improved. That is, in the related art, a dedicated packet exchanger was used for packet exchange, but as the network evolved to ISDN and B-ISDN, it was required to be able to access various networks with one exchange.

The present invention has been proposed to meet the above requirements, and an object thereof is to provide a method for setting up and releasing a normal call for packet switching to enable packet switching in an electronic switch for providing circuit switching.

In order to achieve the above object, the present invention, the terminal (DTE) is respectively connected to the source exchange and the destination exchange with a packet exchange function, the source exchange and the destination exchange is interconnected through a network, Each switch has a link layer (LAPB), a packet layer (PLP), and a packet call processing (BPCC) block in which a call request (CR) packet is transferred from the source terminal (DTE) to the source PLP. If received, the PLP sends a CR packet acknowledgment request (CrPktValRQ) signal to the calling BPCC block and starts a timer T200; If a CR packet acknowledgment (CrPktValRP) signal is received from the originating BPCC block, starting a timer (T220) and transmitting a call request packet to a counterpart; When the call request (CR) packet is received through the network at the called party's PLP, sending an incoming call packet acknowledgment request (IcPktValRQ) signal to the called party's BPCC block and starting a timer (T300); When the incoming call packet acknowledgment (IcPktValRP) signal is received from the called party BPCC block, transmitting an incoming call packet (IC) to the called party terminal (DTE) and starting a timer (T310); When a CA packet is received from the called terminal DTE, transmitting a CaPktValRQ signal to the called BPCC block and starting a timer T320; When the lake packet packet acknowledgment (CaPktValRP) signal is received from the called party BPCC block, converting to a data active state (DataActState), and transmitting a lake lock (CA) packet to the originating exchange side PLP; Transmitting a call connection packet acknowledgment request (CcPktValRQ) signal to the calling party BPCC block when a CA packet is received from the called party BPCC block and starting a timer T230; And when a call connection packet acknowledgment (CcPktValRP) signal is received from the originating BPCC block, transmitting a call connection (CC) packet to the calling terminal (DTE) and transitioning to a data active state (DataActState). do.

1 is a schematic structural diagram of a packet switched network to which the present invention is applied;

2 is a protocol stack of a source side and a destination side exchange during packet exchange according to the present invention;

3 is a state transition diagram showing a change of state in a packet layer (PLP) according to the present invention;

4 is a flowchart illustrating a process of setting up a normal call according to the present invention;

5 is a flowchart illustrating a process of releasing a normal call according to the present invention.

＊ Explanation of symbols for main parts of drawing

100,300: Terminal (DTE) 200: Switching network

210,220: Subsystem

211,221: main processor 212,222: ISDN subscriber module

213,223: packet subscriber module 230: IPC network

240: packet network 250: switch network

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic structural diagram of a packet switched network to which the present invention is applied. As shown in FIG. 1, the switching network 200 to which the present invention is applied is composed of a plurality of subsystems including an originating subsystem 210 and a destination subsystem 220 or exchangers connected to the network. In addition, the originating subsystem 210 and the destination subsystem 220 are composed of subscriber modules 212 and 222, packet subscriber modules 213 and 223, and main processor modules 211 and 221, respectively, to communicate with each other or between each module. There is an IPC network 230, a packet network 240, a switch network 250 to tie the whole system in one. The main processor modules 211 and 221 process resource management, state management, subscriber number management and translation of the entire system, the IPC network 230 and the packet network 240 have an HDLC structure, and the switch network 250 has time. Has a slot structure.

Referring to FIG. 1, the main processor modules 211 and 221 are modules in which software such as operation, maintenance, maintenance, statistics, call processing, and database of the system reside, and other processors or subscribers through the IPC network 230. In communication with the module, performs a packet call processing (BPCC) block according to the present invention.

The ISDN subscriber module (212, 222) is a module connected to the ISDN terminal (100, 300) satisfying the protocol conditions of the ISDN physical layer through the terminal interface, the packet subscriber module (213, 223) through the switch interface 250 B channel on the ISDN terminal interface Function (ie, providing a route)

The packet subscriber modules 213 and 223 relay the packet frames received in HDLC form from one time slot of the switch network interface to the packet switch network, the function of the link layer (LAPB), and the data flow control function of the packet layer (PLP). do. In addition, communication with the packet call processing (BPCC) block in the main processor (211,221) via the IPC interface 230, the connection, disconnection, switch of the LAPB connected to the ISDN terminal by the command from the packet call processing (BPCC) block Allocates, connects, and releases specific time slots in the network.

2 is a protocol stack of an originating and terminating exchange during packet exchange according to the present invention. Referring to FIG. 2, the source exchange 210 and the destination exchange 220 are composed of a physical layer, a link layer (LAPB), a packet layer (PLP), and a packet call processing application (BPCC) layer. As described, the link layer (LAPB) and the packet layer (PLP) are processed in the packet subscriber module, and the packet call processing application (BPCC) is processed in the main processor.

3 is a state transition diagram showing a change of state in a packet layer (PLP) according to the present invention. Referring to FIG. 3, a waiting state (ReadyState: S10) is a state in which a program starts and waits for an event after initialization.

The user link setup wait state (UserL2EstWaitState: S20) is a link setup request (LinkSetupRQ) signal having a call type (Cell type = Org) signal from a packet call processing (BPCC) block in a waiting state (S10) during an outgoing call processing. When you receive a transition state. Upon receiving a LinkSetupRQ signal, the PLP sends a LinkModeSetup Signal to the LAPB. Here, the link setup request (LinkSetupRQ) signal may be omitted. If this signal is omitted, the LAPB operates as 'modulo 8'. If the LAPB is to be operated as 'Modulo 128', the LinkSetup Request (LinkSetupRQ) signal cannot be omitted. After the link mode setup signal is sent to the LAPB, if the link is not set up until the timer T100 expires, the LAPB transitions to the ready status.

The network link setup waiting status (NetL2EstWaitStatus: S20) is a link setup request with the parameter that the call type is called (cell type = destination) from the packet call processing (BPCC) block in the waiting state (ReadyState: S10) during incoming call processing. Transition when a LinkSetupRQ) signal is received. When this signal is received, the destination PLP sends a LinkEstRQ signal to the LAPB to establish a link. In this case, the information required for the mode (modulo 8 or modulo 128) is also transmitted to the link establishment request (LinkEstReq) signal.

The PLP standby state (PLPReadyState: S41) is included in the L2 active state (L2 ActState: S40), and the L2 link is established.

The call waiting state (OrgWaitState: S42) is an outgoing call processing process. When a call request (CR) call is received from the user in the PLP waiting state (PLPReadyState: S41), the CR packet checking request (CrPktValRQ) signal is sent to the BPCC block. It is waiting for a signal called PID (InitCgPid) from BPCC. The PID (InitCgPid) signal then includes the ID of the child process of the BPCC to process the packet using the same call reference ID (the identifier that distinguishes the call of the packet) as the call request packet. The BPCC block has the destination address contained in the CR Packet Acknowledgment Request (CrPktValRQ) signal and locates the subsystem and PLP to be processed at the destination.

The CR packet acknowledgment wait state (CrValRqstate: S43) is a state of waiting for a CR packet acknowledgment (CrPktvalRP) signal when an InitCgPid signal is received from a BPCC block in an outgoing standby state (OrgWaitState).

The DTE wait state (DTEWaitState: S44) receives a CR packet acknowledgment (CrPktValRP) signal from the BPCC block in the CR packet acknowledgment wait state (CrValRqState: S43) during outgoing call processing. The CR Packet Acknowledgment (CrPktValRP) signal contains all the information about the destination (ie, subsystem location, required subscriber boards, etc.) and therefore calls the call to the corresponding PLP layer of the subsystem. Deliver the packet and wait for a response from the called process. This state is also present in ITU-T X.25.

CC packet check wait state (CcValRqState: S45) is a DAC wait state (DTEWaitState: S44), when a call accept (CA) packet is received from the destination, the CC packet is sent to the BPCC block to query the validity and usefulness of this packet. It sends a CcPktValRQ signal and waits for a response.

In the data active state (FlowcontrolReadyState or DataActState, S49), the CC packet acknowledgment (CcPktValRP) signal is received in the CC packet acknowledgment wait state (CcValRqState: S35) or the CA packet acknowledgment response (CaPktValRqState: S48). Receives CaPktValRP) signal and delivers call accept (CA) packet to calling party. From this point on, flow of user data begins.

Incoming call packet acknowledgment wait state (IcPktValRqState: S46) is a call request (CR) packet received from the calling party in PLP waiting state (PLPReadyState: S41), and the incoming call packet acknowledgment request (IcPktRQ) signal to the BPCC block. Wait for an incoming call packet acknowledgment (IcPktValRP) signal. If the call request (CR) packet received from the calling party is a valid value, the " IcPktValRP " signal is received. If it is invalid, the " IcPktValNok " signal is received.

DCE waiting state (DCEWaitState: S47) receives an incoming packet acknowledgment (IcPktValRP) signal from the BPCC block in the incoming call packet acknowledgment wait state (IcPktVal RqState) and sends an incoming call (IC) packet to the called terminal. This state is also described in ITU-T X.25.

CA packet confirmation wait state (CaPktValRqState: S48) receives a Call Accept (CA) packet from the destination terminal in DCE standby state (DCEWaitState), and requests CA packet confirmation to the BPCC block to confirm the validity and validity of this packet. Sending a (CaPktValRQ) signal and waiting for a response, which is one of incoming call processing.

The DTE release wait state (DTEClrRqState: S51) is a state in which a call clear (CLR) packet has been received from the terminal in DataActState, CcValReqState, DTEWaitState, DCEWaitState, and CaPktValRqState. This state is a state in the release process that sends a ClrCgRelRQ (if called) or ClrCdLcRelRQ (if called) signal to the BPCC block to verify the validity / validity of the received call release (CLR) packet. to be.

Release response wait state (NclrRqState: S52) receives ClrCgLcRelRP (if calling party) or ClrCdLcRelRQ (if calling party) signal from BPCC block in DTEClrRqState (S51), and clear confirm (CC) packet to DTE side. It sends a clear request packet to the other side of the network and waits for the response. When it receives a Clear Confirm (CC) packet from the other side of the network, it enters the PLP waiting state (PLPReadyState: S41). Transition

The release packet check wait state (NclrValRqState: S54) is a state in which a clear packet is received from the other side of the network in DTEWaitState, CcValReqState, DataActive, DCEWaitState, and CaPktValRqState.The NclrCgRelRQ It is in the process of releasing a signal (if called) or NclrCdLcRelRQ (if called) and waiting for a response.

The DCE release indication state (DCEClearIndState: S55) sends a clear indication (CI) packet to the terminal when NclrValRqState (S54) receives NclrCdLcRelRP (if called) or NclrCgLcRelRP (if called). Waiting for the response. This state is also indicated in ITU-T X.25, and is a state during the release process. When a clear confirm (CC) packet is received from the terminal side, the state transitions to the PLP waiting state (PLPReadyState: S41).

LinkRelWaitState sends LinkRelReq signal to LAPB when it receives LinkRelRQ signal to release link layer from BPCC block in any state of PLP, and waits for the response. Transition to the state (ReadyState).

As such, the signals transmitted between the PLP and BPCC blocks are shown in Tables 1a and 1b.

Signal notation Signal direction function LinkSetupRQ BPCC-> PLP The signal to establish the link LinkSetupRP PLP-> BPCC Signal that the link is established LinkRelRQ BPCC-> PLP Signal to unlink LinkDiscRP PLP-> BPCC A signal that the link has been released InitCgPid BPCC-> PLP Notice that a BPCC child process has been allocated to handle the call CrPktValRQ PLP-> BPCC Signal that the CR packet has been received CrPktValRP BPCC-> PLP Signal confirming that the CR packet is normal and valid IcPktValRQ PLP-> BPCC Signal that a CR has been received from the other side of the network IcPktValRP BPCC-> PLP Signal from the other side of the network confirming that the CR is normal and valid CaPktValRQ PLP-> BPCC Signal that the CA packet is received from the terminal CaPktValRP BPCC-> PLP Signal confirming that the received CA packet is a normal and valid packet CcPktValRQ PLP-> BPCC Signal that a CA packet has been received from the other side of the network CcPktValRP BPCC-> PLP Signal confirming that CA packet received from the other side of network is normal and valid ClrCgLcRelRQ PLP-> BPCC Signal that clear packet is received from calling terminal ClrCgLcRelRP BPCC-> PLP Signal confirming that clear packet received from calling party is normal and valid NclrCgLcRelRQ PLP-> BPCC Signal that the calling party has received a clear packet from the other side of the network. NclrCgLcRelRP BPCC-> PLP Signal that confirms that the clear packet received from the other side of the network on the calling side is normal / valid

Signal notation Signal direction function ClrCdLcRelRQ PLP-> BPCC Signal indicating that clear packet is received from terminal at called party ClrCdLcRelRP BPCC-> PLP Signal confirming that clear packet received from terminal is normal and valid at called party NclrCdLcRelRQ PLP-> BPCC Signal that the receiving party receives clear packet from the other side of the network. NclrCdLcRelRP BPCC-> PLP Signal that confirms that the clear packet received from the other side of the network on the called party is normal and valid CrPktValNokRP BPCC-> PLP Response that the received CR packet is not normal CaPktValNokRP BPCC-> PLP Response that received CA packet is not normal IcPktValNokRP BPCC-> PLP Reply that the Encrypting Packet is not normal CcPktValNokRP BPCC-> PLP Response that received CC packet is not normal

4 is a flowchart illustrating a normal call setup process according to the present invention. Referring to FIG. 4, the originating side (Orig_Side) includes a terminal (DTE), a link layer (LAPB), a packet layer (PLP), and an originating packet call processing (BPCCo) block, and the called party (Dest_Side) is a terminal (DTE). ), A link layer (LAPB), a packet layer (PLP), and a destination packet call processing (BPCCt) block. Each of these layers is performed in the packet subscriber module and the main processor of the corresponding exchange subsystem, and has a hierarchical structure according to OSI, as described in FIG.

The originating packet call processing (BPCCo) block sends a Link Setup Request (LinkSetupRQ) signal to the PLP, and the PLP is in the Ready State and then receives a LinkSetup Request (LinkSetupRQ) signal from the BPCCo block to the LAPB. Transmit to the User Link Setting Waiting State (UserL2EstWaitState) after transmitting the Set (LinkModeSet) signal. Here, the PLP starts a timer T100 upon receiving a LinkSetupRQ signal.

When the terminal (DTE) transmits the SABM to the LAPB according to the HDLC protocol, the LAPB transmits a UA to the DTE and a LinkEstInd signal to the PLP. In this case, when the LAPB receives the LinkModeSet signal in the ready state, the LAPB transitions to the MFC wait state (WaitMFC_State), transmits the link setting indication signal (LinkEstInd), and then transitions to the MFC_State.

When the PLP receives a LinkEstInd signal from the LAPB, the PLP transitions to a PLP ReadyState and transmits a LinkSetupRP signal to the BPCCo block. This operation establishes the originating link.

On the other hand, when the PLP is in a waiting state (ReadyState: S10) and receives a LinkSetup Request (LinkSetupRQ) signal from the BPCCt block, the called party transitions to the network link setup waiting state (NetL2EstWaitState) and sends a LinkEstReq signal. Send to LAPB. Accordingly, the LAPB sends a SABM to the DTE to request a link setup. When the LAPB receives the UA from the DTE, the LAPB transmits a LinkEstCfm signal to the PLP. When the PLP receives a LinkEstCfm signal from the LAPB, the PLP transitions to the PLP standby state (PLPReadyState: S41) and transmits a LinkSetupRP signal to the BPCCt block. Here, the called party PLP starts the timer T120 when receiving the link setup request (LinkSetupRQ) signal and starts the timer T110 when receiving the link setup confirmation (LinkEstCfm) signal. By this operation, the receiver is set up as a link.

Subsequently, when the caller receives a CR (Call Request) packet having a logical channel number (LCN) = x from the DTE in the PLP waiting state (PLPReadyState), the PLP transitions to the calling wait state (OrgldWaitState) and simultaneously goes to the BPCCo block. Transmit CR packet confirmation request (CrPktValRQ) signal. At this time, the BPCCo block analyzes the CR packet included in the received CR packet confirmation request (CrPktValRQ) signal to verify validity, and creates a child process of BPCC to process the call, and the ID is transmitted to the PLP through the InitCgPid signal. To pass. When the PLP receives the InitCgPid signal, it transitions to CrValRqState (S43), starts the timer T210, and waits for a response signal. When the CR packet acknowledgment (CrPktValRP) signal is received from the BPCCo block, the PLP transitions to the DTEWaitState (S44) and simultaneously transmits a Call Request packet (TxLcn = x, RxLcn = y) to the called party and starts the timer T200.

When the called PLP receives the CR packet from the calling PLP, the called PLP transmits an incoming call acknowledgment request (IcPktValRQ) signal to the called packet call processing block (BPCCt), starts the timer T300, and transitions to IcPktValRqState (S46). The BPCCt block analyzes the received incoming call (IC) packet and transmits the 'IcPktValRP' signal to the PLP if it is a normal call and transmits a 'Nok' response if there is an error. When the called party PLP receives the incoming call acknowledgment (IcPktValRP) signal, it sends an Encrypting Call (IC) packet (Lcn = y) to the DTE side, starts a timer T310, and transitions to DCEWaitState (S47). The destination terminal (DTE) transmits a CA packet (Lcn = y) to the PLP if the call can be received. Accordingly, the PLP transmits a CA packet confirmation request (CaPktValRQ) signal to the BPCCt block and transitions to CaPktValRqState (S48). Start the T320.

Upon receiving the CA packet acknowledgment (CaPktValRP) signal from the BPCCt block, the called party PLP transitions to DataActState (S49) and transmits a call accept packet (TxLcn = y, RxLcn = x) to the calling party PLP.

When the originating PLP receives the CA packet from the called party, it transmits a CC packet acknowledgment request (CcPktValRQ) signal to the BPCCo block, starts the timer T230, and transitions to CcValRqState (S45). When the CC packet acknowledgment (CcPktValRP) signal is received from the BPCCo block, the PLP transitions to the DataActState (S49) and transmits the CC packet (Lcn = x) to the originating DTE.

By this operation, call setup is completed, and the calling party PLP and the called party PLP are in a data activation state (S49) and can transmit the packet data of the user to each other.

5 is a flowchart illustrating a process of releasing a normal call according to the present invention. Referring to Figure 5, there is a DTE, LAPB, PLP, BPCC, BPCC on one side and BPCC, PLP, LAPB, DTE on the other side is connected through the network, if one side is the calling party, the other side is called party, If one side is called, the other side is called. That is, the call release process can be started from either the calling party or the called party.

One side of the PLP starts the timer T400 when it receives a clear (CLR) packet (Lcn = x) from the DTEWait, CcValReq, or DataActive when the calling party receives DCEWait, CaPktValReq, or a call clear from the DTE in the DataActive state. In addition, the ClrCgLcRelRQ signal is transmitted to the BPCC block, and the DTEClearRqState (S51) transitions. Subsequently, when the ClrCgLcRP signal is received from the BPCC, the PLP transmits a Clear Request packet (TxLcn = x, RxLcn = y) to the other side, transitions to NclrRqState (S52), and transmits a CLC (Lcn = x) packet to the DTE side.

When the other PLP receives the Clear Request packet through the network, it transmits an NclrCdLcRelRQ signal to its BPCC block, transitions to NclrValRqState (S54), and starts timer T420. Then, when the NclrCdLcRelRP signal is received from the BPCC block, it transitions to DCEClrIndState, starts timer T430, transmits a Clear Confirm packet (TxLcn = y, RxLcn = x) to one side PLP through the network, and sends a CLI packet (Lcn = y) to its DTE. Send it. Subsequently, when the CLC packet is received from its DTE, the timer T110 starts and transitions to the PLP standby state (PLPReadyState: S41).

On the other hand, when one side PLP receives a Clear Confirm packet from the other side through the network, it starts the timer T110 and transitions to the PLP standby state (PLPReadyState: S41).

On the other hand, when a LinkRelRQ signal is received from the BPCC in any state, one side PLP sends a LinkRelReq signal to the LAPB, starts timer T150, and transitions to the LinkRelWaite state. When one side of the LAPB receives the LinkRelReq signal from the PLP, the LAPB transitions from MFC_State to WaitRel_State and transmits a DISC to the DTE. When the UA is received from the DTE, the LAPB transitions to the ReadyState (S10) and transmits a LinkRelCfm signal to the PLP. The PLP transitions to the ReadyState (S10) when the LinkRelCfm signal is received. When the link is released by the BPCC block as described above, it is not necessary to transmit the LinkDiscRP signal from the PLP to the BPCC.

If the link is cleared by the DTE, the DTE sends a DISC to the LAPB, whereby the LAPB sends the UA to the DTE and sends a LinkRelInd signal to the PLP. When the PLP receives the LinkRelInd signal, the PLP sends a LinkDiscRP signal to the BPCC block to inform the release of the link and transitions to the ReadyState (S10).

As described above, according to the present invention, it is possible to set up and release a call for packet exchange in an electronic switchboard, and thus it is convenient to use, and in particular, the call setup and release process can be quickly processed.

Claims (2)

A terminal (DTE) is connected to an originating exchange and a destination exchange each equipped with a packet switching function, and an originating exchange and a destination exchange are interconnected through a network, and each exchange has a link layer (LAPB) and a packet layer ( PLP), in a switching network in which a packet call processing (BPCC) block is implemented, When a Call Request (CR) packet is received from the calling terminal (DTE) to the calling PLP, the PLP transmits a CR Packet Confirm Request (CrPktValRQ) signal to the calling BPCC block and starts a timer (T200). ; If a CR packet acknowledgment (CrPktValRP) signal is received from the originating BPCC block, starting a timer (T220) and transmitting a call request packet to a counterpart; When the call request (CR) packet is received through the network at the called party's PLP, sending an incoming call packet acknowledgment request (IcPktValRQ) signal to the called party's BPCC block and starting a timer (T300); When the incoming call packet acknowledgment (IcPktValRP) signal is received from the called party BPCC block, transmitting an incoming call packet (IC) to the called party terminal (DTE) and starting a timer (T310); When a CA packet is received from the called terminal DTE, transmitting a CaPktValRQ signal to the called BPCC block and starting a timer T320; When the lake packet packet acknowledgment (CaPktValRP) signal is received from the called party BPCC block, converting to a data active state (DataActState), and transmitting a lake lock (CA) packet to the originating exchange side PLP; Transmitting a call connection packet acknowledgment request (CcPktValRQ) signal to the calling party BPCC block when a CA packet is received from the called party BPCC block and starting a timer T230; And When a call connection packet acknowledgment (CcPktValRP) signal is received from the originating BPCC block, transmitting a call connection (CC) packet to the calling terminal (DTE) and transitioning to a data active state (DataActState). Normal call setup method for packet exchange in electronic switching center. A terminal (DTE) is connected to an originating exchange and a destination exchange each equipped with a packet switching function, and an originating exchange and a destination exchange are interconnected through a network, and each exchange has a link layer (LAPB) and a packet layer ( PLP), in a switching network in which a packet call processing (BPCC) block is implemented, When a call release (CLR) packet is received from one terminal, the corresponding PLP transmits a call release packet confirmation request (ClrCgLcRelRQ) signal to its BPCC block and starts a timer (T400); When one PLP receives a Release Packet Acknowledgment (ClrCgLcRelRP) signal from its BPCC block. Transmitting a call release packet to the other side, starting a timer T410, and sending a call release confirmation (CLC) packet to its own terminal; Receiving a release packet from the other side, the other PLP sends a release packet acknowledgment request (NclrCdLcRelRQ) signal to its BPCC block and transmits a timer (T420); When a call release packet acknowledgment (NclrCdLcRelRP) signal is received from the other BPCC block, transmitting a call release indication (CLI) packet to its own terminal and transmitting a Clear Confirm packet to one side; And Transitioning to a PLP waiting state when a call release confirmation (CLC) packet is received from a terminal at the other PLP, and transitioning to a PLP wait state when a clear confirmation packet is received from a counterpart at a PLP of one side; Normal call release method for packet exchange in electronic switching center.

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