A method and device for partitioning packet classification rules are provided. According to an example of the method, one or more group are obtained by initially grouping bits included in a rule set on the network device. A local optimum combination of bits is determined for each group according to a correlation analysis on the group. A global optimum combination of bits having a minimum correlation coefficient and comprising fewest bits is determined from all the local optimum combinations of bits. The rule set is partitioned according to the global optimum combination of bits.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A method for partitioning packet classification rules, comprising: obtaining, by a network device, one or more groups by initially grouping bits included in a rule set on the network device, wherein each rule in the rule set comprises m bits, and m is an integer greater than or equal to 2; determining, by the network device, a local optimum combination of bits for each group according to a correlation analysis on the group; determining, by the network device, a global optimum combination of bits having a minimum correlation coefficient and comprising fewest bits, from all the local optimum combinations of bits; and partitioning, by the network device, the rule set according to the global optimum combination of bits. 2. The method according to claim 1, wherein initially grouping bits included in the rule set, comprising: determining, by the network device, a distinct number for each of the bits according to a first value number, a second value number and a third value number of the bit, wherein the first value number indicates a number of rules included in the rule set in which the bit is of a first value, the second value number indicates a number of rules included in the rule set in which the bit is of a second value, and the third value number indicates a number of rules included in the rule set in which the bit is of a third value; and classifying, by the network device, bits with a same distinct number into one group. 3. The method according to claim 2, wherein determining the distinct number for each of the bits according to the first value number, the second value number and the third value number of the bit, comprising: determining, by the network device, the distinct number for the bit according to the following formula: distinct number=|first value number−second value number|+n*third value number, wherein n is greater than zero. 4. The method according to claim 1, wherein determining the local optimum combination of bits for each group according to a correlation analysis on the group, comprising: beginning from i=1, generating, by the network device, C (k, i) combinations of bits by selecting i bits from all k bits included in the group, wherein k is an integer greater than or equal to 1, partitioning, by the network device, the rule set into a plurality of rule subsets according to each of the C (k, i) combinations of bits, and obtaining, by the network device, a bit string for each of the rule subsets; determining, by the network device, a correlation coefficient for each of the combinations of bits according to the respective bit strings of the rule subsets; updating, by the network device, the i by i=i+1, regenerating, by the network device, C (k, i) combinations of bits until i is greater than k; and determining, by the network device, from all the combinations of bits, a local optimum combination of bits having the minimum correlation coefficient and including the fewest bits. 5. The method according to claim 4, wherein obtaining the bit string for each of the rule subsets, comprising: determining, by the network device, whether a rule in the rule set is included in the rule subset, setting, by the network device, a bit corresponding to the rule in the bit string for the rule subset to be of 1 if the rule is included in the rule subset; and setting, by the network device, the bit corresponding to the rule in the bit string for the rule subset to be of 0 if the rule is not included in the rule subset. 6. The method according to claim 4, wherein determining the correlation coefficient for a combination of bits according to the respective bit strings of the rule subsets, comprising: determining, by the network device, a non-zero bit number which indicates a number of bits being of 1 in all the bit strings of the rule subsets corresponding to the combination of bits; determining, by the network device, a non-zero bit string number which indicates a number of bit strings of which at least one bit is of 1 in all the bit strings of the rule subsets corresponding to the combination of bits; and obtaining, by the network device, a correlation coefficient for the combination of bits according to a ratio of the non-zero bit number to the non-zero bit string number. 7. A device for partitioning packet classification rules, comprising: a processor; and a machine-readable storage medium stored with machine-executable instructions corresponding to a control logic for partitioning packet classification rule, the control logic for partitioning packet classification rule comprises a rule set, and by reading and executing the machine-executable instruction, the processor is caused to: obtain one or more groups by initially grouping bits included in the rule set, wherein each rule in the rule set comprises m bits, and m is an integer greater than or equal to 2; determine a local optimum combination of bits for each group according to a correlation analysis on the group; determine a global optimum combination of bits having a minimum correlation coefficient and comprising fewest bits, from all the local optimum combinations of bits; and partition the rule set according to the global optimum combination of bits. 8. The device according to claim 7, wherein when initially grouping bits included in the rule set, the machine-executable instructions further cause the processor to: determine a distinct number for each of the bits according to a first value number, a second value number and a third value number of the bit, wherein the first value number indicates a number of rules included in the rule set in which the bit is of a first value, the second value number indicates a number of rules included in the rule set in which the bit is of a second value, and the third value number indicates a number of rules included in the rule set in which the bit is of a third value; and classify the bits with a same distinct number into one group. 9. The device according to claim 8, wherein when determining the distinct number for each of the bits according to the first value number, the second value number and the third value number of the bit, the following formula is used: distinct number=|first value number−second value number|+n*third value number, wherein n is greater than zero. 10. The device according to claim 7, wherein when determining the local optimum combination of bits for each group according to the correlation analysis on the group, the machine-executable instructions further cause the processor to: beginning from i=1, generate C (k, i) combinations of bits by selecting i bits from all k bits included in the group, wherein k is an integer greater than or equal to 1, partition the rule set into a plurality of rule subsets according to each of the C (k, i) combinations of bits, and obtain a bit string for each of the rule subsets; determine a correlation coefficient for each of the combinations of bits according to the respective bit strings of the rule subsets; update the i by i=i+1, regenerate C (k, i) combinations of bits until i is greater than k; and determine, from all the combinations of bits, a local optimum combination of bits having the minimum correlation coefficient and including the fewest bits. 11. The device according to claim 10, wherein when obtaining the bit string for each of the rule subsets, the machine-executable instructions further cause the processor to: determine whether a rule in the rule set is included in the rule subset, set a bit corresponding to the rule in the bit string for the rule subset to be of 0 if the rule is included in the rule subset; and set the bit corresponding to the rule in the bit string for the rule subset to be of 0 if the rule is not included in the rule subset. 12. The device according to claim 10, wherein when determining the correlation coefficient for a combination of bits according to the respective bit strings of the rule subsets, the machine-executable instructions further cause the processor to: determine a non-zero bit number which indicates a number of bits being of 1 in all the bit strings of the rule subsets corresponding to the combination of bits; determine a non-zero bit string number which indicates a number of bit strings of which at least one bit is of 1 in all the bit strings of the rule subsets corresponding to the combination of bits; and obtain a correlation coefficient for the combination of bits according to a ratio of the non-zero bit number to the non-zero bit string number.