(a) Basic features of TCP connections (9 types in total, serial numbers 1 to 9); (b) Content features of TCP connections (13 types in total, serial numbers 10 to 22); (c) Time-based traffic features of the connection records (9 types in total, serial numbers 23 to 31); (d) Host-based traffic features of the connection records (10 types in total, serial numbers 32 to 41).