Packet capture for measurement of several network parameters on high-speed networks requires high clock resolution and the capability of analyzing different protocol functions for behavioral functionality. Herein, we present a practical packet-capture tool that time-stamps packet arrival at the data-link layer with nanosecond resolution and with the capability of forwarding packets to the application layer in real time. Our tool can be used to analyze both network performance and behavioral functionality for high-speed networks. We build this tool on a NetFPGA card and with minimum dependencies on off-line data processing. Different from existing specialized packet-capture cards, our card allows packets to be time-stamped at both the data-link and application layers. We present the design and evaluation of our proposed tool. We tested the accuracy of our tool and compared it to that of a commercial specialized packet-capture card, and show that they are equivalent. Additionally, our tool provides different functionality.