In the paper, the bit entropy and bit flow entropy of IP packet headers in CERNET backbone are analyzed, and we find that the 16 bits of identification field in IP packet header are fit to the matching field of sampling mask.

• 对CERNET主干网络流量IP报头各字段的位熵和位流熵进行分析 ；结果表明标识字段 16比特适合于抽样掩码匹配字段 .