Abstract: Analyzing a packet header in a data communications system involves using a descriptor mask to control selective comparison between one or more bits of the packet header and one or more bits of a session descriptor. Setting a mask bit to one state indicates that a comparison between a corresponding bit of a received packet header and a corresponding bit of a session descriptor should be performed, whereas setting the mask bit to an alternative state indicates that no comparison should be performed. A comparison result is generated that indicates whether all of the one or more bits of the packet header match corresponding ones of the one or more bits of the first session descriptor. The descriptor mask and session descriptor are programmable, so that the comparison hardware design is protocol-independent.