TCP/IP over ATM over poor quality links is known to fail catastrophically. It mainly comes from the fact that TCP incorrectly assumes loss or corruption of data to be due to network congestion, and that TCP reacts inappropriately based on its congestion control mechanism. One of the main issues emerging in satellite networks is the efficient and assured delivery of data. In this paper, a Service Specific Coordination Function for Transparent Assured Delivery with AAL5 (SSCF-TADA5) is described. The SSCF-TADA5 guarantees the transparent assured delivery of data in TCP/IP over ATM over degraded physical link conditions such as a satellite radio link. This link is characterized by large bandwidth-delay product, high error rate with burst errors, and low throughput. The SSCF-TADA5 is coordinated with Service Specific Connection Oriented Protocol (SSCOP). The SSCF-TADA5 and SSCOP are integrated with IP over ATM as a new Service Specific Convergence Sublayer (SSCS) of ATM Adaption Layer (AAL) 5 for user data transfer. We discuss the design of the SSCF-TADA5, and then compare the TCP/IP performance with and without the SSCF-TADA5. The results of the test show that assured delivery with SSCF-TADA5 significantly mitigate the degradation in the most severe cases that are characterized with a combination of high error rate and high channel utilization.