This study evaluates the performance of the Transport Control Protocol (TCP) over IPv4 and IPv6 networks. Key performance metrics like bandwidth, throughput, and latency are measured. Simulations are conducted using OPNET Network simulator to transmit HTTP and FTP traffic over IPv4 and IPv6 networks using TCP New Reno. The results show that IPv6 has higher throughput but also higher latency than IPv4. This is because the larger IPv6 header size increases processing time. However, IPv6 shows lower packet loss than IPv4.