Method for Doubly Backing up Files Asynchronously
Field of the Invention

The present invention relates to the ftetd of communication , and more
particularly to asynchronous double files backup.

Background of the Invention
Call detail record (CDR) is a report that telephone exchanges generated, which contains detailed information about calls originating from, terminating at or passing through the exchange. CDRs are used mainly for billing purpose. A call detail record is a data record that contains information related to a telephone call, such as the origination and destination addresses of the call, the time when the call started and ended, the duration of the call, the time of day the call was made and any toll charges that were added through the network or charges for operator services, among other details of the call. CDR data fields are fully populated when the underlying call/transaction ends. The CDR is an asset in managing long distance telephone costs and aids in the planning for future telecommunications needs.

Most telephone PBX (public branch exchange) and PMS (property management systems) output CDR. Generally, these get created at the end of a call but on some phone systems the data is available during the call. This data is output from the phone system by a serial link known as the Station Message Detail Recording port (SMDR).

At present, some billing centers need to delete the original CDR file after transferred successfully from wireless call server (WCS). Thus, the normal active/standby equipment synchronization mechanism may meet problem. For example, the active equipment has file 1 and file 2, and transfers file 1 to a billing center; the iMng center deletes the transferwiJ file 1 to mark that file 1 is transferred successfully. Note that, file 1 still exists in the standby equipment. If the activefetandby equipment uses the normal synchronization mechanism, then the standby equipment will think file 1 is missed in the active equipment and copy file 1 to the active equipment. The result is that the billing center will misunderstand file 1 is not transferred successfully. This confiict with billing

center transfer mechanism (transfer and delete).
Figure 1 show an existing solutton for synchronous double backup with active/standby mechanism. As shown in Figure 1, the active file handling device 1 copies the CDR file from file set A1 to B1, A1 being a backup of B1, and the standby file handling device 2 copies the CDR file from file set A2 to B2, A2 being a back up of 82. The billing center gets files from 81 or 82 and then deletes those files in 81 and 82 after transferred successfully. For synchronization between A1 and A2, if the standby file handling device 2 finds that the active file handling device 1 misses file, then it will copy the backup file to the active file handling device 1 in order to ensure file sets A1 and A2 are synchronized. For synchronization between 81 and 82, if the standby file handling device 2 finds that the active file handling device 1 misses file for a while (for example 30 minutes), then it will deletes the backup file 82 in order to ensure file sets 81 and 82 are synchronized.
It means the synchronization between A1&A2 and 81&82 are different, it will make the system more complicate and consume more system resource.
Therefore, it is necessary to find a new method to fulfill the following two requirements:
- ensure that the billing center may delete the original CDR file after transferred from the WCS successfully;
- ensure that the WCS has the CDR file backup after transferred.
Summarv of the Invention

To solve the above problem in the prior art, according to an aspect of the present invention, a method for doubly backing up files asynchronously is proposed, wherein at least two first network elements share a second network element, both of said first network elements include respectively an active file handling device and a standby file handling device. In this method, said active file handling device copies the files to the second network element, if said standby file handling device finds that said active file handling device misses the files, said standby file handling device copies backups of the files to said active file handling device, thus the files stored in said active file handling device and the files stored in said standby file handling device being synchronized.

Brief Description of the Drawings
These and many other features and advantages of the present invention will become apparent from the following description of the embodiments of the present invention with reference to the drawings, wherein:
- Fig.1 shows an existing solution for synchronous double backup with active/standby mechanism;
- Fig.2 illustrates the basic idea of the present invention;
- Fig.3 illustrates the method for doubly backing up files asynchronously according to an embodiment of the present invention;
- Fig.4 illustrates another possible case of the method of the present invention of Fig. 3.

Detailed Description of the Invention
The present invention proposes a method for doubly backing up files asynchronously. This method is based on the Idea illustrated in Figure 2.

As show in Figure 2, for example, said files are CDR files, the active and standby file handling devices are in one network element such as WCS, and the file handling device 1 is in active status. For synchronization between A1 and A2, if the standby file handling device 2 finds that the active file handling device 1 misses file(s), then it will copy backup file(s) to the active file handling device 1 so as to ensure file sets A1 and A2 are synchronized. In fact, in our solution, there exists no synchronization between file sets B1 and 82. That is to say, if the file handling device 1 is active, then the CDR files are transferred to 61 file set. OthenA^ise the CDR files are transferred to B2 file set. The active file handling device 1 copies the CDR file from file set A1 to B1. In addition, there exists no file transfer from A2 to 82, except that the file handling device 1 is unavailable.
After remove the synchronization between B1&B2, above solution consumes less system resource compare with existing solution.
For further optimizing the method of the present invention, i.e. to save hardware cost, we introduce a network element such as post process modules (PPM) to handle part of the "asynchronous double backup solution" task separately by connecting multiple WCS. The PPM is used for collecting,

processing, transferring files, and for storing files in respective directories for difference WCSs. Furthermore, the PPM could also perform a CDR post processing when needed, which is done usually by the billing center. Comparing with the hardware cost save, the system architecture becomes a little complex, but which is acceptable.
With reference to Figure 3, for example two WCSs are connected to the PPM 1 which is in active state, or to the standby PPM 2 when the PPM 1 fails, but the present invention is not limited to this, i.e. there may be multiple WCSs connected to the two PPMs. Assume that the file handling device 1 and PPM 1 are in active status. Note that if PPM 1 is available, then the thick active/standby path Is followed; if PPM 1 is unavailable, then the fine active/standby path is followed. It can be seen from this figure that, only one synchronization mechanism is used. For synchronization between A1 and A2 and between A3 and A4, if the standby file handling devices 2 and 4 find that the active file handling devices 1 and 3 miss files, then they will copy backup files to the active file handling devices 1 and 3 so as to ensure that the file sets A1 and A2 as well as the file sets A3 and A4 are synchronized. As shown, the active PPM 1 contains file set B1 and the standby PPM 2 contains file set B2, and there exists no synchronization between B1 and 82. Since the file handling device 1 is active, the CDR flies are transferred to 81 file set. Otherwise CDR files are transferred to 82 file set. The active file handling device 1 of WCS1 copies the CDR flle(s) from file set A1 to 81. The active file handling device 3 of WCS2 copies the CDR file(s) from file set A3 to 81. The standby file handling devices 2 and 4 won't copy CDR file(s) from WCSs 1 and 2 to the PPM.
It should be noted that, currently the WCS can configure the PPM 1 and PPM 2 with respective IP addresses, and the IP address of PPM 1 has a higher priority than that of PPM 2. Therefore, the WCS can output CDR files to the PPM 1 or PPM 2 according to its priority of IP address and available status automatically Both of the PPMs may provide a floatiPjKldress to the billing center. This means that the PPM 1 and PPM 2 are the same IP from the billing center's point of view.
Figure 4 illustrates another possible case of the method of the present invention of Fig. 3.
As shown in Figure 4, the file handling devices 1 and 4 are

active, and the PPM 1 fails. In this case, if the standby file handling devices 2 and 3 find that the active file handling devices 1 and 4 miss files, then they will copy backup files to the active file handling devices 1 and 4 so as to ensure that those file sets are synchronized. The active file handling devices 1 and 4 copy the CDR files from the WCSs 1 and 2 to the PPM 2. The standby file handling devices 2 and 3 won't copy the CDR files from WCSs 1 and 2 to the PPM 2.
Thereby with this method, a very high-level data safety with one pair of hardware equipments and a durable interface can be provided, which interface refers to the interface between the WCS and the billing center. In addition, the system architecture is not too complex and the system resource usage is not too much. It can be seen that, the use of PPM may reduce cost remarkably.
According to the lab test result, reducing one pair of CDR file synchronization mechanisms may save 20% system resource (CPU, memory, etc) while doing synchronization task for WCS with 1M subscribers capacity. Furthermore, a single PPM can handle 10M mobile phone subscribers. If we calculate with the average 500K WCS capacity, then 95% hardware cost could be saved. If we calculate with the average 1M WCS capacity, then 90% hardware cost could be saved.

Below is compare result between the existing solution and this invention solution from different point of view:

Although the exemplary embodiments of the method for doubly backing up files asynchronously of the present invention is described above in detail, the above embodiments are not exhaustive, and those skilled in the art can make numerous changes and modifications within the spirit and scope of the present invention. Therefore, the present Invention Is not limited to those

embodiments, the scope of which is defined only by the appended claims.

Claims

1.A method for doubly backing up files asynchronously, wherein at least two first network elements share a second network element, both of said first network elements include respectively an active file handling device and a standby file handling device, characterized in that, said active file handling device copies the files to the second network element, if said standby file handling device finds that said active file handling device misses the files, said standby file handling device copies backup of the files to said active file handling device, thus the files stored in said active file handling device and the files stored in said standby file handling device being synchronized.

2. The method according to claim 1, wherein said file is a call detail record.

3. The method according to any of claims 1 or 2, wherein said file stored in said second network element will be deleted after being transferred to a billing center.

4. The method according to any of claims 1-3, wherein said first network
element is a wireless call server.

5. The method according to any of claims 1-4, wherein said second network element is a post process module.

6. The method according to any of claims 1-5, wherein said active and standby file handling devices are used for processing, storing and transferring said files.

7. The method according to any of claims 1-6, wherein said second network element is used for collecting, processing, transfemng said files, and for storing said files in respective directories for each of first network elements.

8. The method according to any of claims 1-7, wherein a further second network element is provided as a standby of said second network element.

9. The method according to claim 8, wherein said active file handling device copies the files to said further second network element if said second network element fails.

10. The method according to claims 8 or 9, wherein said first network elements configure said second network element and said further second network element with respective IP addresses, and the IP address of said second network element has a higher priority than that of said further network element.

11. The method according to any of claims 8-10, wherein said first network elements transfer the files to said second network element or said further second network element according to its priority of IP address and available status automatically

12. The method according to any of claims 8-11, wherein said second network element and said further second network element provide float IP address to the billing center.