echo 1 > /proc/sys/net/ipv4/tcp_abc
From RFC 34100. A Modified Algorithm for Increasing the Congestion Window As originally outlined in [Jac88] and specified in [RFC2581], TCP uses two algorithms for increasing the congestion window. During steady-state, TCP uses the Congestion Avoidance algorithm to linearly increase the value of cwnd. At the beginning of a transfer, after a retransmission timeout or after a long idle period (in some implementations), TCP uses the Slow Start algorithm to increase cwnd exponentially. According to RFC 2581, slow start bases the cwnd increase on the number of incoming acknowledgments. During congestion avoidance RFC 2581 allows more latitude in increasing cwnd, but traditionally implementations have based the increase on the number of arriving ACKs. In the following two subsections, we detail modifications to these algorithms to increase cwnd based on the number of bytes being acknowledged by each arriving ACK, rather than by the number of ACKs that arrive. We call these changes "Appropriate Byte Counting" (ABC) [All99].
Read more: http://www.faqs.org/rfcs/rfc34100.html#ixzz0mJkZPK7k