CN1984122B - Method for decreasing facsimile protocol frame collision - Google Patents

Abstract

The invention discloses a method for reducing the collision of fax negotiation frames. The first delay time and the second delay time are set, and the fax transfer device adjusts and sends the fax negotiation from the second fax terminal to the first fax terminal according to the set first delay time. frame time, adjusting the time for sending the fax negotiation frame from the first fax terminal to the second fax terminal according to the set second delay time. The method proposed by the invention can reduce the collision of fax negotiation frames and improve the success rate of fax.

Description

Method to reduce fax negotiation frame collision

technical field

The invention relates to facsimile technology, in particular to a method for reducing collision of facsimile negotiation frames. the

Background technique

Facsimile communication is a communication method that uses scanning and photoelectric conversion technology to send static images such as text, pictures, and photos from the source to the receiving end through wired or wireless channels, and reproduce the still images at the receiving end. Since the 1970s, due to the opening of the file fax service on the Public Switched Telephone Network (PSTN), fax communication has been vigorously developed and has become one of the means for people to transmit information. the

Referring to the fax network diagram shown in Figure 1, the fax terminal on the PSTN side is directly connected to the PSTN network, and negotiates and communicates with other fax terminals through the PSTN network; the fax terminal on the mobile side connects to a fixed wireless terminal (FWT) or mobile terminal (MS ) is connected to the mobile network, and negotiates and communicates with other fax terminals through the mobile network. In order to ensure that the fax can be negotiated normally in the mobile network, an interworking function module (InterWorking Function, IWF) specially used to process the fax service is usually integrated in the Mobile Switching Center (MSC), and the IWF transmits the fax call signaling and data It is equivalent to playing the role of a gateway, and its function is similar to that of the PSTN gateway. Among them, the IWF, the PSTN gateway, the FWT and the MS can all be referred to as fax transfer devices. the

Referring to the basic fax flow chart shown in Figure 2, after the calling and called lines are connected, negotiation communication is performed through the interaction of multiple fax negotiation frames. First, the called party sends a digital identification signal (DIS) indicating its own performance to the calling party; after receiving the DIS, the calling party returns a digital command signal (DCS) to the called party, which includes information such as encoding mode, transmission rate, scanning density, etc. ; Immediately following the DCS, the calling party sends a training sequence (TCF) to the called party to detect whether the link quality can meet the quality requirements for fax page transmission; after the called party receives the TCF, it detects the TCF and judges whether the link quality is Can meet the requirements, if so, then return to the caller a confirmation of receipt (CFR), requiring the caller to start sending fax pages, otherwise, return training failure (FTT) to the caller, requiring the caller to retrain; the caller receives the CFR After that, start to send the message data page by page, and the called party will receive it; if there are multiple pages of data to be sent, the calling party will send a multi-page signal (MPS) to the called party; if all the data has been sent, the calling party will send End of sending process (EOP); after the called party receives MPS or EOP, it judges whether the quality of the received page is good, if it is good, returns the message confirmation (MCF) to the calling party, otherwise, returns the receipt negative retraining/reception confirmation Retraining (RTN/RTP); Finally, the caller sends a disconnection (DCN) to the called party to end the entire fax process.

In order to ensure the normal progress of fax communication, the fax protocol stipulates that after the fax terminal sends a fax command frame, if it has not received a response frame within a certain period of time, it will resend the same command frame. For example, see Figure 3. After the calling and called lines are connected, the called sends a DIS to the calling. If the called has not received the DCS after the timer expires, it resends the DIS to the calling. Among them, The timer time is generally set to 3 seconds. the

With the development of mobile networks and the evolution of fixed networks, the fax network is becoming more and more complex. The influence of various factors such as wireless link delay and IP bearer in the fax communication process makes the end-to-end delay of fax more and more , such as satellite fax, long-distance fax, etc. Since the existing fax protocol is a half-duplex protocol, the fax terminal cannot send and receive fax negotiation frames at the same time. Therefore, excessive fax delays can easily cause collisions of fax negotiation frames. For example, as shown in Figure 3, due to delay Large, the called party resends the DIS and the calling party responds to the DCS during transmission, which causes the fax to fail. the

Contents of the invention

In view of this, the object of the present invention is to provide a method for reducing the collision of fax negotiation frames, reduce the collision between fax negotiation frames, and improve the success rate of fax. the

In order to achieve the above object, the technical scheme provided by the invention is as follows:

A. Set the first delay time and the second delay time. The fax transfer device sends the first received command frame from the first fax terminal to the second fax terminal, and judges whether a response frame from the second fax terminal is received. If received, go to step B; otherwise, go to step C;

B. The facsimile transfer device judges whether the time difference between the current time and the time difference between the last received command frame from the first facsimile terminal is greater than the first delay time, if yes, then sends the received response frame to the first facsimile terminal, and ends this session Process processing; otherwise, return to step B;

C. The fax transfer device judges whether the time difference between the current time and the last command frame sent to the second fax terminal is greater than the second delay time, if yes, resends the received command frame to the second fax terminal, otherwise, returns to execute Step C. the

Wherein, the setting of the first delay duration and the second delay duration is: the fax transfer device sets the first delay duration and the second delay duration according to the fax protocol. the

Wherein, the setting of the first delay time is as follows: the fax transfer device respectively records the time when adjacent command frames are received, and sets the difference between the two times as the first delay time. the

Wherein, the fax transfer device is an IWF, or a PSTN gateway, or a FWT, or an MS. the

The command frame is a digital representation signal DIS, and the response frame is a digital command signal DCS. the

Alternatively, the command frame is TCF, and the response frame is CFR or FTT. the

Alternatively, the command frame is MPS or EOP, and the response frame is MCF or RTN/RTP. the

It can be seen that in the present invention, the transfer device adjusts the sending time of the received fax negotiation frame according to the set first delay time and second delay time, which effectively reduces the collision between fax negotiation frames, thereby improving the fax success rate. Rate. the

Description of drawings

Fig. 1 is the schematic diagram of facsimile networking in the prior art;

Fig. 2 is the basic flowchart of fax in the prior art;

Fig. 3 is the collision diagram of facsimile negotiation frame;

Fig. 4 is the flow chart of the method for reducing facsimile negotiation frame collision in the embodiment of the present invention;

Fig. 5 is the schematic diagram of the method for reducing DIS and DCS collision in the embodiment of the present invention;

Fig. 6 is a flowchart of a method for reducing collisions between DIS and DCS in an embodiment of the present invention. the

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples. the

The basic idea of the present invention is: set the first delay time and the second delay time, the fax transfer device adjusts the time for sending the fax negotiation frame from the second fax terminal to the first fax terminal according to the set first delay time, and according to the set The second delay length adjusts the time for sending the fax negotiation frame from the first fax terminal to the second fax terminal. the

Wherein, the first delay time is the delay time between the fax transfer device and the first fax terminal; the second delay time is the delay time between the fax transfer device and the second fax terminal. The fax transfer device sets the first delay time and the second delay time according to the actual situation, for example, according to the existing fax protocol, it is set to 3 seconds. the

Referring to shown in Figure 4, the method for reducing fax negotiation frame collision in the present embodiment mainly includes the following steps:

Step 401: The fax transfer device sends the command frame received for the first time from the first fax terminal to the second fax terminal, and judges whether a response frame from the second fax terminal is received, and if so, executes step 402; otherwise , go to step 404. the

Step 402: The fax relay device judges whether the time difference between the current time and the last received command frame from the first fax terminal is greater than the first delay time, if yes, execute step 403; otherwise, return to execute step 402. the

Step 403: The fax relay device sends the received response frame to the first fax terminal, and ends the process of this process. the

That is to say, if the time difference between the current time and the last received command frame from the first facsimile terminal is not greater than the first delay duration, then in order to avoid collision between the sent response frame and the command frame resent by the first facsimile terminal, the facsimile The relay device delays sending the response frame to the first fax terminal, and does not send the response frame to the first fax terminal until the time difference is greater than the first delay duration. In the time when the fax relay equipment is waiting to send the response frame, even if the fax relay equipment receives the command frame resent by the first fax terminal, it will not be forwarded to the second fax terminal. the

Here, the fax transfer device can also determine whether the time difference between the current time and the last received command frame from the first fax terminal is within a range, for example, when the time difference is between T1-15%T1 and T1+15%T1 The response frame is delayed until the time difference is greater than T1+15%T1, and the response frame is not sent to the first fax terminal. Wherein, T1 represents the first delay time. the

Step 404: The fax relay device judges whether the time difference between the current time and the last command frame sent to the second fax terminal is greater than the second delay time, if yes, execute step 405; otherwise, return to execute step 404. the

Step 405: the fax relay device resends the received command frame to the second fax terminal. the

That is to say, if the time difference between the current time and the last time the command frame is sent to the second fax terminal is not greater than the second delay duration, in order to avoid the collision between the retransmitted command frame and the response frame sent by the second fax terminal, the fax relay device The time for resending the command frame is delayed, and the command frame is not resent to the second fax terminal until the time difference is greater than the second delay duration. If the fax transfer device receives a response frame from the second fax terminal while waiting for the retransmission command frame, the fax transfer device will no longer resend the command frame to the second fax terminal, but will follow the process of receiving the response frame To process, that is to execute step 402 . the

Here, the fax transfer device can also determine whether the time difference between the current time and the last time the command frame is sent to the second fax terminal is within a certain range, for example, when the time difference is between T2-15% T2 and T2+15% T2 The command frame is resent, and the command frame is not resent to the second fax terminal until the time difference is greater than T2+15%T2. Wherein, T2 represents the second delay time. the

It should be noted that, if the first fax terminal still does not receive the response frame after step 403 is executed, that is, after the fax transfer device has sent the response frame to the first fax terminal, then step 402 is repeatedly executed. If after step 405 is executed, that is, after the fax relay device has resent the command frame to the second fax terminal, the fax relay device still does not receive the response frame from the second fax terminal, then step 404 is repeatedly executed. the

Wherein, the fax transfer device is an IWF, PSTN gateway, FWT, or MS. The command frame is the fax negotiation frame specified in the G3 fax process definition (T30) that the fax transfer device has received, and the response frame is the T30 regulation that is waiting to be received after the fax transfer device sends out the received fax negotiation frame. fax negotiation frame. For example, the command frame is DIS, and the response frame is DCS; or, the command frame is TCF, and the response frame is CFR or FTT; or, the command frame is MPS or EOP, and the response frame is MCF or RTN/RTP. the

Wherein, the first delay time and the second delay time can be set according to the existing fax protocol. For example, the first delay time is set to 3 seconds; or, the fax relay device records the time of receiving adjacent command frames respectively, and sets the difference between the two times as the first delay time. The second delay time is the interval for the fax relay device to continuously resend the command frame before receiving a response, and its value is defined by the fax relay device, for example, it is set to 3s. In addition, the values of the first delay duration and the second delay duration can be designed to be variable according to actual needs, for example, each time they are incremented or decremented according to a certain rule. the

Referring to FIG. 5 , taking the IWF processing the DIS from the called fax terminal and the DCS from the calling fax terminal as an example, the process of reducing the collision between DIS and DCS in this embodiment is described. Wherein, the first fax terminal is the called fax terminal; the second fax terminal is the calling fax terminal. T1 is the first delay time, that is, the delay time between the IWF and the called party; T2 is the second delay time, that is, the delay time between the IWF and the calling party. the

Referring to Fig. 6, the process of IWF adjusting DCS or DIS transmission time according to T1 or T2 in this embodiment mainly includes the following steps:

Step 601: The IWF sends the first received DIS from the called party to the calling party, and judges whether it has received the DCS from the calling party, and if so, executes step 602; otherwise, executes step 604. the

Step 602: The IWF judges whether the time difference between the current time and the last time the DIS is received is greater than T1, if yes, execute step 603; otherwise, return to execute step 602. the

Step 603: The IWF sends the received DCS to the called party, and then ends the processing of this flow. the

In addition, the IWF can also determine whether the time difference between the current time and the last received DIS is within a certain range. For example, when the time difference is between T1-15%T1 and T1+15%T1, in order to avoid collisions, the IWF delays The DCS is sent, and the DCS is not sent until the time difference is greater than T1+15%T1. During the time when the IWF waits until sending the DCS, even if the IWF receives the resent DIS from the called party, it will not forward it to the calling party. the

Step 604: The IWF judges whether the time difference between the current time and the last time the DIS is sent to the caller is greater than T2, if yes, execute step 605; otherwise, return to execute step 604. the

Step 605: The IWF resends the received DIS to the calling party. the

In addition, the IWF can also determine whether the time difference between the current time and the last DIS sent to the caller is within a certain range, for example, when the time difference is between T2-15%T2 and T2+15%T2, in order to avoid collision, The IWF delays the time for resending the DIS, and does not resend the DIS to the calling party until the time difference is greater than T2+15%T2. During the time when the IWF is waiting to resend the DIS, if it receives the DCS from the calling party, the IWF will not resend the DIS to the calling party, but process it according to the process of receiving the DCS, that is, execute step 602 . the

It should be noted that, if the called party still does not receive the DCS after the IWF has sent the DCS to the called party, step 602 is repeated. If the IWF still does not receive the DCS from the calling party after the IWF has resent the DIS to the calling party, step 604 is repeatedly executed. the

Wherein, the values of T1 and T2 are set by the IWF according to the actual situation. For example, the value of T1 can be set as the time difference between the IWF receiving adjacent DISs. If the IWF has not received the second DIS when receiving the DCS, that is to say, the IWF cannot calculate T1 based on the time of receiving the adjacent DIS, then the IWF can preset a T1 duration, and according to the preset T1 adjusts the sending time of the DCS. In the subsequent transmission process of the fax negotiation frame, the IWF can always process according to the preset T1, and can also adjust the preset T1 according to the actual situation. the

The value of T2 can be set as the time difference between the time when the IWF sends the DIS to the calling party and the time when the IWF receives the DCS from the calling party. Since the IWF does not know when the caller sends the DCS, the DIS retransmitted by the IWF may collide with the DCS sent by the caller on the way. Once a collision occurs, it is likely to cause subsequent retransmitted frames to continue to collide, resulting in Fax calls failed. In order to avoid this situation, the value of T2 can be designed to be variable according to the actual situation. For example, the duration of T2 can be increased according to certain rules to avoid continued collision of subsequent retransmitted frames and ensure the fax success rate. the

It can be seen that the method provided by the present invention reduces the collision of fax negotiation frames and improves the success rate of fax. the

It should be noted that the process of IWF adjusting the sending time of DCS or DIS according to the set T1 or T2 has been described in detail above, and the processing of various fax negotiation frames by other transfer devices is similar to the above situation. I won't go into details here. the

The purpose, technical solutions and beneficial effects of the present invention have been further described in detail above. It should be understood that the above description is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. shall be included in the protection scope of the present invention. the

Claims (8)

1. A method for reducing fax negotiation frame collision, characterized in that, A. Set the first delay time and the second delay time. The fax transfer device sends the first received command frame from the first fax terminal to the second fax terminal, and judges whether a response frame from the second fax terminal is received. If received, go to step B; otherwise, go to step C; B. The facsimile transfer device judges whether the time difference between the current time and the time difference between the last received command frame from the first facsimile terminal is greater than the first delay time, if yes, then sends the received response frame to the first facsimile terminal, and ends this session Process processing; otherwise, return to step B; C. The fax transfer device judges whether the time difference between the current time and the last command frame sent to the second fax terminal is greater than the second delay time, if yes, resends the received command frame to the second fax terminal, otherwise, returns to execute Step C. 2 . The method according to claim 1 , wherein the setting the first delay time and the second delay time is: the fax transfer device sets the first delay time and the second delay time according to the fax protocol. 3. The method according to claim 1, wherein the setting of the first delay duration is as follows: the fax relay equipment respectively records the time when adjacent command frames are received, and sets the difference between the two times as the first delay duration. 4. The method according to claim 1 or 3, wherein the fax transfer device is an interworking function module IWF, or a public switched telephone network PSTN gateway, or a wireless fixed terminal FWT, or a mobile terminal MS. 5. The method according to claim 2, wherein the fax transfer device is an interworking function module IWF, or a gateway of the public switched telephone network PSTN, or a fixed wireless terminal FWT, or a mobile terminal MS. 6. The method according to claim 1 or 3, wherein the command frame is a digital display signal DIS, and the response frame is a digital command signal DCS. 7. The method according to claim 1 or 3, wherein the command frame is a training sequence TCF, and the response frame is a confirmation CFR or a training failure FTT. 8. The method according to claim 1 or 3, wherein the command frame is a multi-page signal MPS or a process end EOP, and the response frame is a message confirmation MCF or a negative retraining/receiving affirmative retraining RTN/RTP.

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