LT-TCP: End-to-end framework to improve TCP performance over networks with lossy channels

TCP performance over wireless links suffers substantially when packet error rates increase beyond about 1% - 5%. This paper proposes end-end mechanisms to improve TCP performance over lossy networks with potentially much higher packet loss rates. Our proposed scheme separates congestion indications from wireless packet erasures by exploiting ECN. Timeout effects due to packet erasures are combated using a dynamic and adaptive Forward Error Correction (FEC) scheme that includes adaptation of TCP's Maximum Segment Size. Proactive and reactive FEC overhead enhance TCP SACK to protect original segments and retransmissions respectively. Dynamically changing the MSS tailors the number of segments in the window for optimal performance. SACK and timeout mechanisms are used as a last resort. ns-2 simulations show that our scheme substantially improves TCP performance even for packet loss rates up to 30%, thus extending the dynamic range and performance of TCP over networks with lossy (e.g., wireless) links.