CN1997086B - Realization Method of Automatic Repeat Call Trial in Softswitch Network - Google Patents

Abstract

This invention discloses one realization method for automatic repeat calling in flexible exchange network, which comprises the following steps: in repeating, the flexible exchange updates and selects relay circuit and establishes one cross and to align new real-time transmission agreement RTP materials when the selected relay circuit in one relay gate and using original relay circuit and when the RTP is connected with calls to send out calls by use of repeated relay circuit; deleting original relay circuit adding relay circuit into cross to send out calls to original RTP materials.

Description

Realization Method of Automatic Repeat Call Trial in Softswitch Network

technical field

The present invention relates to the field of fixed network communication, in particular to a method for automatically repeating call attempts when an abnormal situation is encountered during call establishment when a softswitch network communicates with a traditional PSTN (Public Switched Telephone Network) network.

Background technique

In the traditional PSTN call process, there will be abnormal situations in the call establishment process, so that the call establishment cannot go on normally. These abnormalities are partly caused by the network or the trunk circuit. If another inter-office trunk circuit is selected to re-initiate the call, the call may still be connected, which can effectively improve the connection rate of the inter-office call. This process of reselecting the trunk circuit and trying to connect the call again after encountering an abnormality in the call connection is called automatic repeated call attempt. The abnormal factors causing the automatic repeated call retry are as follows:

1. When two-way simultaneous robbery is detected;

The so-called co-grabbing means that after an exchange establishes a call using common-channel signaling and sends an initial address message, it receives an initial address message from the other exchange while waiting for the response from the other party. At this time, it is necessary to determine whether the switching office is the master of the occupied circuit. Usually, the method of judging the odd and even number of the circuit CIC number is used, that is, the circuit with a large signaling point controls the circuit with an even CIC number, and the circuit with a small signaling point controls the circuit with an odd CIC number. circuit. If a certain switching office is not the master, it has to give up the circuit so as to provide the incoming call initiated by the other party, and it needs to reselect another trunk circuit to initiate the call and repeat the call attempt.

2. When a block message is received after sending the address message and before receiving any backward messages;

It is emphasized here that not receiving any backward message is to ensure that the other party has not received the address message before sending the blocking message, and the other party has not determined that the circuit is occupied. In this case, it is necessary to repeat the call attempt. If the backward message is received, both parties have made it clear that the circuit has been selected to establish a call, and the blocking message will not affect this call, but only the subsequent call establishment.

3. When a circuit restoration message is received after sending an address message and before receiving a certain backward message;

This call situation is similar to situation 2, the difference is that a restoration message is received. In this case, the call establishment initiated this time must be released first. If other messages are not received, it is necessary to repeat the call attempt.

4. When the continuity test fails;

Continuity check is unavoidable when using two-way relay for common-channel signaling. If the signaling is passed, it does not mean that the relay circuit is also connected. The conduction test is to test whether the relay circuit is conducted through the control of the signaling message. If it fails, the trunk circuit cannot be used for call connection, and the trunk circuit must be selected again.

5. When an unreasonable message is received during call setup.

When encountering the above five situations, the user part of the switching office will start the process of automatically repeating the call attempt to try to connect the call successfully.

Softswitch SS (softswitch), as the core of the call and control of the next generation network (NGN), provides call control and connection control with real-time services. One of its very important functions is the intercommunication with the traditional PSTN network and supports relay access. The relay media gateway is used to complete the conversion of the media flow between the circuit switching network side and the IP packet network side, and complete the call establishment between the circuit switching network and the IP network under the control of the softswitch together with the signaling gateway, see Figure 1. When establishing a call with a traditional exchange, the media connection is also divided into two parts due to different networks, one is the traditional PSTN network and the other is the IP network. NO.7 Signaling is transmitted between the softswitch and the traditional switching office through the signaling gateway (SG: signaling gateway). The softswitch uses NO.7 common channel signaling (such as ISUP) to initiate a call and inform the other party of the selection of an inter-office trunk circuit, and controls the trunk gateway through the H.248/MGCP protocol to complete the connection of the media on the IP side.

Taking H.248 as an example here, it is a master-slave control protocol, with the softswitch as the master and the relay gateway as the slave. It uses endpoints to describe entities that initiate and receive media streams. The endpoints include physical endpoints such as relay circuits and temporary endpoints such as RTP (Realtime Transport Protocol, real-time transport protocol) streams. These endpoints are connected together through association CTX (context), and association is a combination of endpoints connected to each other. H.248 defines a number of commands to operate and manage associations and terminations. For example, the Add command is used to add terminations to an association, and the Subtract command is used to remove a termination from the association it is in. To detach from the current association, the Move command transfers the endpoint from the current association to another association.

When the softswitch establishes a call with the traditional switching office, it is also necessary to provide automatic repeated call attempts to improve the connection rate. Usually, the implementation method of repeating the call attempt is to release the occupied media resources, reselect the trunk circuit and allocate the media resources to initiate a new call. The common practice is to release all the resources occupied by the outgoing call when the same grab causes repeated call attempts by the non-master office, and re-establish the incoming call after receiving the address signal of the other party, and re-establish the alternative circuit of the original outgoing call.

This method can be used for call establishment in traditional exchanges, but it needs to be treated differently in softswitch networks. In fact, several triggering causes of repeated call attempts all occur on the PSTN side, and have little to do with the IP network side where the call media is connected. If the trunk circuit reselected in the repeated call attempt is in the same trunk gateway as the original trunk circuit, the media connection on the IP side that has been established can be used, and this part of the connection does not need to be removed. In addition, when repeating call attempts for two-way simultaneous grabbing, during the period of waiting for release completion when releasing media resources, if this trunk circuit is selected when a new outgoing call is established, new simultaneous grabbing will be caused.

If the media connection already established on the IP network side can be fully utilized, the selection of the trunk circuit is carried out in the same trunk gateway, and the IP network and the PSTN network are treated differently, which can simplify the call connection steps and improve efficiency.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for automatically repeating call attempts in a softswitch network, so as to solve the problem that automatic repeat call attempts are required when an abnormal situation is encountered in call establishment when the softswitch network and the PSTN network are interconnected.

The present invention provides a method for realizing automatic repeated call attempts in a softswitch network, which includes the following steps for the case where the selected trunk circuits for two repeated call attempts at the same time belong to the same trunk gateway:

S1. In the process of initiating call establishment, the softswitch judges that the same grabbing occurs and it is not the master control office, then reselects the trunk circuit TRK2, controls the trunk gateway to create a new association CTX2, and allocates a new association in the new association. The real-time transport protocol resource RTP2;

S2. The softswitch controls the trunk gateway to move the previously occupied trunk circuit TRK1 to the new associated CTX2, and use the previously occupied trunk circuit TRK1 and the new real-time transport protocol resource RTP2 to connect the incoming call initiated by the master control office ;

S3. The softswitch controls the trunk gateway to move the reselected trunk circuit TRK2 to the original associated CTX1, and use the newly selected trunk circuit TRK2 and the original real-time transport protocol resource RTP1 to make repeated call attempts.

Further, the reselected trunk circuit TRK2 in step S1 and the originally occupied trunk circuit TRK1 in step S2 belong to the same trunk gateway.

Further, step S1 can be further divided into:

After the softswitch sends the initial address message to initiate a call, it receives the initial address message from the exchange of the other party, judges that a simultaneous grab has occurred, and judges whether it is the master control office according to the judging method of the master control office during the simultaneous grab;

If the softswitch judges that there is a simultaneous grab and it is not the master control office, it will reselect the trunk circuit TRK2;

The soft switch sends the newly added Add message of the H.248 protocol to the trunk gateway, creates a new association CTX2 at the trunk gateway, and adds the reselected trunk circuit TRK2 and the new real-time transport protocol termination point RTP2 to be determined;

The trunk gateway allocates RTP resources for the newly added RTP endpoint RTP2, and replies to the softswitch with a Reply message including the IP address of the RTP endpoint, the adopted voice compression algorithm, and the RTP port.

Further, step S2 can be further divided into:

The softswitch sends the move command of H.248 protocol to the trunk gateway to move the previously occupied trunk circuit termination point to the new association;

The trunk gateway returns the Reply message of the H.248 protocol to the softswitch to confirm the successful movement;

The softswitch uses the previously occupied trunk circuit and new real-time transport protocol resources to connect incoming calls initiated by the main control office.

Further, step S3 can be further divided into:

The softswitch sends the move command of the H.248 protocol to the trunk gateway, moves the reselected trunk circuit to the original association, and uses the newly selected trunk circuit and the original real-time transport protocol resource to make repeated call attempts;

After receiving the successful media establishment message returned by the trunk gateway, it sends an address signaling message of No. 7 signaling to the exchange of the opposite party, declaring that the reselected trunk circuit is occupied and an outgoing call is initiated.

Further, step S1 further includes:

In the process of initiating the call establishment, the softswitch judges that co-robbing occurs and it is the main control office, then discards the received initial address message IAM sent by the exchange, and continues the outgoing call.

The present invention also provides a method for realizing automatic repeated call attempts in a softswitch network, aiming at the situation that the trunk circuit selected for repeated call attempts and the original occupied trunk circuit belong to the same trunk gateway due to non-simultaneous snatching factors, including the following step:

A1. In the process of initiating call establishment, when it is judged that repeated call attempts are caused by non-simultaneous snatching factors, the softswitch controls the trunk gateway to delete the original trunk circuit from the original association, and retain the real-time transmission protocol resources in the original association;

A2. The softswitch controls the trunk gateway to add a newly selected trunk circuit to the original association;

A3. The softswitch sends an initial address message to the peer exchange to re-initiate the outbound call.

Further, the original relay circuit in step A1 and the newly selected relay circuit in step A2 belong to the same relay gateway.

Further, step A1 can be further divided into:

The softswitch sends a delete Subtract command to the trunk gateway to delete the unavailable original trunk circuit from the original association, and retain the real-time transport protocol resources in the original association;

After the deletion is successful, the trunk gateway returns a Reply message to the softswitch.

Further, step A2 can be further divided into:

The softswitch selects a new trunk circuit, sends a new Add command message to the trunk gateway, and adds the selected new trunk circuit termination point to the original association;

After the addition is successful, the trunk gateway returns a Reply message to the softswitch.

The present invention makes full use of the characteristics of media resource allocation and use in the softswitch network. When repeated call attempts, the trunk circuit is reselected and the original resources are reserved, so that the realization of automatic repeated call attempts is more convenient, and the efficiency of call connection is improved. Reduced the possibility of the same grab happening again in this call connection.

Description of drawings

Figure 1 is a network topology diagram of the intercommunication between softswitches and traditional switching offices;

Fig. 2 is the flow chart of setting up the media of the softswitch as the non-master office after the same grabbing occurs;

Fig. 3 is a flow chart of media establishment for automatic repeated call attempts caused by non-concurrent snatching.

Detailed ways

The technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1 is a network topology diagram of intercommunication between softswitches and traditional PSTN switching offices. In this figure, the core control device of the soft switch is called SS (soft switch, soft switch), the signaling gateway is called SG (Signaling Gateway), and the trunk gateway is called TG (Trunk Gateway). The soft switch controls the trunk gateway operation termination point through the H.248/MGCP (Media Gateway Control Protocol, Media Gateway Control Protocol) protocol command message, and the TUP/ISUP protocol is used to establish a call between the soft switch and the traditional switching office. The TUP protocol is a telephone user part (telephone user part) agreement, and the ISUP agreement is an ISDN user part (ISDN user part) agreement. The following uses the H.248 protocol and the ISUP protocol as examples to illustrate the repeated call attempt process.

During the intercommunication process between the softswitch SS and the traditional PSTN exchange, if the call setup fails, the automatic repeat call attempt function is used to improve the connection rate. When repeated call attempts, in most cases, the reselected trunk circuit is in the same trunk gateway as the originally selected trunk circuit, so this processing can be greatly improved. The purpose of the present invention is aimed at the characteristics of the softswitch network, to provide a simple method for setting up call media in the process of repeated call attempts, to improve the efficiency of call connection, and to simplify the steps of call establishment.

The implementation method of automatically repeating call attempts in the softswitch network of the present invention is exactly for the situation that the trunk circuits selected twice belong to the same trunk gateway, including the same grabbing situation and the non-scrambling situation:

First: For repeated call attempts due to simultaneous grabbing, the softswitch, as the non-master office, is responsible for completing the connection of the incoming call initiated by the other party, and reselecting the trunk circuit to initiate the outgoing call. The key to deal with this situation is to use the originally allocated RTP resources when making a new call after repeated call attempts. You only need to select a new outgoing trunk circuit, use the original association, and add the newly selected trunk circuit. to the original association. For the original trunk circuit relinquished by the softswitch, it is directly moved to the newly established association, and the incoming call is connected together with the newly allocated RTP resources without releasing the original trunk circuit. In this way, the trunk circuit will not be selected when another call is set up because the release process takes a long time to cause the same grab again.

Second: For repeated call attempts under the abnormal conditions of other calls not caused by the same grabbing factor, the softswitch only involves one call in this case, if the newly selected trunk circuit is in the same trunk circuit as the original one Following the gateway, the existing RTP resources can be used without reallocating RTP resources.

In the present invention, for the reselected relay circuit, the relay circuit under the same relay gateway is preferentially selected during reselection. If there is no other optional relay circuit for the same relay gateway, you can only consider choosing another relay gateway, but the existing RTP resources cannot be used. When selecting a trunk circuit, the trunk gateway where the newly selected trunk circuit is located can be known.

What Fig. 2 illustrates is the call establishment processing flow caused by automatic repeated call attempts during simultaneous grabbing.

After the same grab occurs, when the softswitch is used as the master switching office, the processing is relatively simple. It only needs to discard the received initial address message IAM (Initial Address Message) and continue the outgoing call.

After simultaneous grabbing occurs, when the softswitch is used as a non-master switching office, it must first successfully connect the incoming call initiated by the other party, and then re-establish the call initiated by itself by selecting a trunk circuit. Here, the original RTP resources and trunk circuits used when initiating a call are not released. The original RTP resources are used in new outgoing calls for repeated call attempts, and the original trunk circuits are directly used by incoming calls to avoid unnecessary delays after release in the middle. Other calls select the trunk circuit, resulting in a new simultaneous grab.

The following describes the process of setting up a simultaneous call when the softswitch is used as a non-master office, and the specific process is described as follows:

Step 201: The softswitch initiates an outgoing call, sends a new (Add) command message to the trunk gateway, creates an association CTX1 in the trunk gateway, and adds the termination points TRK1 and TRK1 of the selected outgoing trunk circuit to the association. RTP endpoint, where the RTP endpoint is to be allocated by the relay gateway;

Step 202: the relay gateway allocates resource RTP1 for the increased RTP, returns a response (Reply) message to the softswitch, and informs the IP address of the RTP1 termination point, the voice compression algorithm and the RTP port used;

Step 203: After the soft switch receives the correct response from the trunk gateway, it sends an ISUP initial address message (IAM) to the called switching office, notifies the trunk circuit to be occupied, and initiates an outgoing call;

Step 204: After the softswitch sends the initial address message, if it receives the initial address message about the trunk circuit sent by the opposite switching office, it indicates that there is a simultaneous robbery. According to the judging method of the master control office at the same time, the softswitch judges whether it is the master control office or not. Here, it is assumed that the softswitch judges itself as the non-master control office;

Step 205: If the softswitch judges that there is a simultaneous grab and it is a non-master office, it will send an H.248 Add message to the trunk gateway in a similar way to the incoming call connection, requiring the trunk gateway to create a A new association CTX2, adding a new trunk circuit (TRK2) and a new RTP termination point to be determined. The trunk circuit here is selected separately, it is a newly selected trunk circuit for repeated call attempts when the softswitch is out of the office;

Step 206: The relay gateway allocates resource RTP2 for the newly added RTP, and responds to the softswitch with a Reply message, including the IP address of the RTP2 node, the voice compression algorithm used, and the RTP port, etc.;

Step 207: The softswitch needs to use the original trunk circuit TRK1 in the associated CTX1 for incoming calls, and use the reselected trunk circuit TRK2 in the associated CTX2 to initiate a new outgoing call, so it needs to switch between the two associations following the circuit. The soft switch sends a move (Move) command, first transferring the original trunk circuit node TRK1 to the new associated CTX2 associated with RTP2;

Step 208: the trunk gateway returns a reply (Reply) to the softswitch;

Step 209: the softswitch sends the H.248 move (Move) command to the trunk gateway, and transfers the new trunk circuit node TRK2 to the original association CTX1 associated with RTP1;

Step 210: the trunk gateway returns a Reply to the softswitch;

Step 211: The softswitch prepares the media connection for both outgoing and incoming calls, and resends the address signaling message No. 7, ie, the initial address message IAM, to the other party's exchange for the outgoing call, declaring that the circuit is occupied. So far, the media has been re-arranged, and the subsequent continuations will be completed according to the usual procedures, which will not be fully listed here.

Fig. 3 illustrates the call establishment processing flow of automatic repeated call attempts caused by non-concurrent grabbing factors. Repeated call attempts caused by reasons other than the same call only involve one call, and its process is a little simpler, as follows:

Step 301: The softswitch initiates a call, sends an H.248 Add message to the trunk gateway, creates an association CTX1 in the trunk gateway, and adds the selected termination point of the outbound trunk circuit to the association TRK1 and RTP endpoint, where the RTP endpoint is to be determined by the relay gateway;

Step 302: the relay gateway allocates resource RTP1 for the increased RTP, and responds to the softswitch with a Reply message, including the IP address of the RTP1 node, the voice compression algorithm used and the RTP port, etc.;

Step 303: After receiving the correct response from the trunk gateway, the softswitch sends the initial address message (IAM) of ISUP to the called switching office, and notifies the trunk circuit to be occupied;

Step 304: When other events requiring automatic repeated call retries occur, the call connection encounters an abnormality here. The abnormal type is mainly on the side of the traditional switching center, and has no influence on the IP network side. Therefore, the softswitch needs to reselect the trunk circuit to try again. If the selected trunk circuit is in the same trunk gateway as the original trunk circuit, the allocated media resources can continue to be used without being released;

Step 305: The soft switch sends an H.248 Subtract command to the trunk gateway to delete the unavailable trunk circuit TRK1 from the association, and retain the RTP1 resources in the association, so that it is unnecessary to reset the RTP1 media Steps for stream properties;

Step 306: the relay gateway returns a reply (Reply) to the softswitch;

Step 307: the softswitch selects a new trunk circuit TRK2, sends an Add message to the trunk gateway, and adds the termination point of the trunk circuit TRK2 in the associated CTX1;

Step 308: the trunk gateway returns a Reply to the softswitch;

Step 309: After receiving the correct response from the trunk gateway, the softswitch sends the No. 7 address signaling message, that is, the initial address message IAM, and uses the newly selected trunk circuit TRK2 and the originally allocated resource RTP1 to send to the opposite switching office Re-initiate the call, claim the circuit and initiate the call.

The above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without Deviation from the spirit and scope of the technical solutions of the present invention shall be covered by the claims of the present invention.

Claims (10)

1. the realization method of repeating call attempt automatically in a kind of softswitch network, for the situation that the selected trunk circuit of twice repeating try call when grabbing simultaneously at taking place belongs to same trunk gateway, it is characterized in that, comprises the steps: S1. In the process of initiating call establishment, if the softswitch judges that a co-control has occurred and it is not the master control office, it will re-select the trunk circuit, control the trunk gateway to create a new association, and allocate a new real-time call to the new association. transport protocol resources; S2. The softswitch controls the trunk gateway to move the previously occupied trunk circuit to a new association, and use the previously occupied trunk circuit and the new RTP resource to continue the incoming call initiated by the master control office; S3. The softswitch controls the trunk gateway to move the reselected trunk circuit to the original association, and use the newly selected trunk circuit and the original RTP resources to make repeated call attempts. 2. The method according to claim 1, characterized in that, the reselected relay circuit described in step S1 and the former occupied relay circuit described in step S2 belong to the same relay gateway. 3. The method according to claim 1, characterized in that step S1 can be further divided into: After the softswitch sends the initial address message to initiate a call, it receives the initial address message from the exchange of the other party, judges that a simultaneous grab has occurred, and judges whether it is the master control office according to the judging method of the master control office during the simultaneous grab; If the softswitch judges that there is a simultaneous grab and it is not the master control office, it will re-select the trunk circuit; The soft switch sends the new Add message of the H.248 protocol to the trunk gateway, creates a new association at the trunk gateway, and adds the reselected trunk circuit and the new real-time transport protocol termination point to be determined; The trunk gateway allocates RTP resources for the newly added RTP termination point, and replies to the softswitch with a Reply message including the IP address of the RTP termination point, the adopted voice compression algorithm and the RTP port. 4. the method for claim 1, is characterized in that, step S2 can be further divided into: The softswitch sends the move command of H.248 protocol to the trunk gateway to move the previously occupied trunk circuit termination point to the new association; The trunk gateway returns the Reply message of the H.248 protocol to the softswitch to confirm the successful movement; The softswitch uses the previously occupied trunk circuit and new real-time transport protocol resources to connect incoming calls initiated by the main control office. 5. The method according to claim 1, characterized in that step S3 can be further divided into: The softswitch sends the move command of the H.248 protocol to the trunk gateway, moves the reselected trunk circuit to the original association, and uses the newly selected trunk circuit and the original real-time transport protocol resource to make repeated call attempts; After receiving the successful media establishment message returned by the trunk gateway, it sends an address signaling message of No. 7 signaling to the exchange of the opposite party, declaring that the reselected trunk circuit is occupied and an outgoing call is initiated. 6. The method according to claim 1, wherein step S1 further comprises: In the process of initiating the call establishment, the softswitch judges that co-robbing occurs and it is the main control office, then discards the received initial address message IAM sent by the exchange, and continues the outgoing call. 7. the realization method of automatic repeat call trial in a kind of softswitch network, the trunk circuit that causes repeat trial call selection for non-simultaneous snatching factor and the original occupied trunk circuit belong to the same trunk gateway situation, it is characterized in that, Including the following steps: A1. In the process of initiating call establishment, when it is judged that repeated call attempts are caused by non-simultaneous snatching factors, the softswitch controls the trunk gateway to delete the original trunk circuit from the original association, and retain the real-time transmission protocol resources in the original association; A2. The softswitch controls the trunk gateway to add a newly selected trunk circuit to the original association; A3. The softswitch sends an initial address message to the peer exchange to re-initiate the outbound call. 8. The method according to claim 7, wherein the original relay circuit in step A1 and the newly selected relay circuit in step A2 belong to the same relay gateway. 9. method as claimed in claim 7, is characterized in that, step A1 can be further divided into: In the process of initiating call establishment, when it is judged that repeated call attempts are caused by factors other than the same preemption, the softswitch sends a delete Subtract command to the trunk gateway to delete the unavailable original trunk circuit from the original association, and retain the original association. Real-time transport protocol resources; After the deletion is successful, the trunk gateway returns a Reply message to the softswitch. 10. the method for claim 7, is characterized in that, step A2 can be further divided into: The softswitch selects a new trunk circuit, sends a new Add command message to the trunk gateway, and adds the selected new trunk circuit termination point to the original association; After the addition is successful, the trunk gateway returns a Reply message to the softswitch.

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