Satellite Transport Protocol (STP): An SSCOP-based Transport Protocol for Datagram Satellite Networks

We describe the adaptation of an ATM-based protocol, the Service Specific Connection Oriented Protocol (SSCOP), for use as a transport protocol in a datagram-based satellite data network. This protocol operates with high throughput and efficiency over links with a large bandwidth-delay product, including those with a high bit error or packet loss rate. We discuss the modifications to SSCOP necessary for it to operate over an IP-based satellite network. We then compare the performance of the modified protocol (the Satellite Transport Protocol, or STP) with that of conventional TCP and TCP with selective acknowledgments (TCP-Sack). We find that STP performs comparably to TCP-Sack in terms of forward throughput over simulated satellite channels. However, STP uses significantly less bandwidth on the return path, and is relatively insensitive to variations in round trip delay, making it an attractive candidate for asymmetric networks. Finally, STP exhibits very good performance in a rate controlled environment, even when the bit error ratio is severely degraded.