This paper reports our experimentation results with TCP Selective Acknowledgments TCP-Sack, which became an Internet Proposed Standard protocol recently. To understand the performance impact of TCP-Sack deployment, in this study we examined the following issues: How much performance improvement TCP-Sack may bring over the current TCP implementation, TCP-Reno. We conducted experiments both on a lab testbed and over the Internet, under various conditions of link delay and losses. In particular, how well TCP-Sack may perform over long delay paths that include satellite links. What is the performance impact of TCP connections with Sack options on those connections without Sack when the two types running in parallel, if there is any.