Stream control transmission protocol (SCTP) performance over the land mobile satellite channel

We characterize the operation of the SCTP transport protocol over the land mobile satellite channel (LMSC), which is subject to intermittent blockages, and contrast its performance with that of TCP. In particular, we study the ability of SCTP's multihoming capability to adjust to channel blockages. For small files, SCTP's larger connection setup overheads cause single-homed connections to complete transfers slightly slower than TCP. However, depending on the ability of alternate paths, multihoming can improve transfer times so much that SCTP is competitive with an optimized TCP gateway. For large files, quirks in the congestion control of multihomed associations cause performance to deteriorate considerably; though single-homed SCTP is faster than end-to-end TCP, none of the other options can compete with a highly optimized satellite TCP gateway operating without congestion control over the satellite channel. SCTP multihoming semantics do not lend themselves to protocol-spoofing gateways, but some changes to default parameters can help. In the LMSC environment, applications would generally do best to use multihomed SCTP (if available) for small file transfers and gateway-enhanced TCP for larger transactions.