Method, device and system for backup

A backup method, comprising:

• obtaining a serial number of a data packet from an active device;
• obtaining a serial number of a data packet from a standby device by calculating a sum of the serial number of the data packet from the active device and a specific increment value;
• packaging the serial number of the data packet from the standby device into a packet to be backed-up;
• and
• sending the packet to be backed-up.

A backup device, comprising:

• a first receiving module, configured to receive a packet to be backed-up;
• a first analyzing module, configured to obtain a serial number of a data packet from an active device by analyzing the packet, wherein the serial number is carried in the packet;
• a first summing module, configured to obtain a serial number of a data packet from a standby device by calculating the serial number of the data packet from the active device and a specific increment value;
• and
• a first backup module, configured to determine that an increment of the serial number of the data packet from the active device exceeds a first increment threshold and back up the serial number of the data packet from the standby device upon the determination.

A backup device, comprising:

• a first obtaining module, configured to obtain a serial number of a data packet from an active device;
• a second summing module, configured to obtain a serial number of a data packet from a standby device by calculating a sum of the serial number of the data packet from the active device and a specific increment value;
• a first packaging module, configured to package the serial number of the data packet from the standby device into a packet to be backed-up;
• and
• a first sending module, configured to send the packet to be backed-up.

A backup system, comprising:

• a backup device, wherein the backup device further comprising:
• a first receiving module, configured to receive a packet to be backed-up;
• a first analyzing module, configured to obtain a serial number of a data packet from an active device by analyzing the packet, wherein the serial number is carried in the packet;
• a first summing module, configured to obtain a serial number of a data packet from a standby device by calculating the serial number of the data packet from the active device and a specific increment value;
• and
• a first backup module, configured to determine that an increment of the serial number of the data packet from the active device exceeds a first increment threshold and back up the serial number of the data packet from the standby device upon the determination;
• and
• the other backup device, wherein the other backup device further comprising:
• a first obtaining module, configured to obtain the serial number of the data packet from the active device;
• a second summing module, configured to obtain the serial number of the data packet from the standby device by calculating a sum of the serial number of the data packet from the active device and the specific increment value;
• a first packaging module, configured to package the serial number of the data packet from the standby device into a packet to be backed-up;
• and
• a first sending module, configure to send the packet to be backed-up.