New broadband access technologies such as hybrid fiber coaxial (HFC) are likely to provide fast and cost effective support to a variety of applications including video on demand (VoD), inter-active computer games, and Internet-type applications such as Web browsing, ftp, e-mail, and telephony. Since most of these applications use TCP as the transport layer protocol, the key to their efficiency largely depends on TCP protocol performance. We investigate the performance of TCP in terms of effective throughput in an HFC network environment using different load conditions and network buffer sizes. We find that TCP experiences low throughput as a result of the well-known problem of ACK compression. An algorithm that controls ACK spacing is introduced to improve TCP performance.