I queried this in 2.6.18 (SUSE 10.2): /proc/sys/net/ipv4>cat tcp_congestion_control reno And in the 2.6.20 till latest linus-git - it is cubic. So searching through all the different implementation (net/ipv4/): /hdc1/download/2.6/linux-2.6-latest/net/ipv4>grep tcp_congestion_ops *.c tcp.c:extern struct tcp_congestion_ops tcp_reno; tcp_bic.c:static struct tcp_congestion_ops bictcp = { tcp_cong.c:struct tcp_congestion_ops tcp_reno = { tcp_cubic.c:static struct tcp_congestion_ops cubictcp = { tcp_highspeed.c:static struct tcp_congestion_ops tcp_highspeed = { tcp_htcp.c:static struct tcp_congestion_ops htcp = { tcp_hybla.c:static struct tcp_congestion_ops tcp_hybla = { tcp_illinois.c:static struct tcp_congestion_ops tcp_illinois = { tcp_input.c: const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; tcp_input.c: const struct tcp_congestion_ops *ca_ops tcp_lp.c:static struct tcp_congestion_ops tcp_lp = { tcp_scalable.c:static struct tcp_congestion_ops tcp_scalable = { tcp_vegas.c:static struct tcp_congestion_ops tcp_vegas = { tcp_veno.c:static struct tcp_congestion_ops tcp_veno = { tcp_westwood.c:static struct tcp_congestion_ops tcp_westwood = { tcp_yeah.c:static struct tcp_congestion_ops tcp_yeah = { and for cubic it is implemented in net/ipv4/tcp_cubic.c. http://netsrv.csc.ncsu.edu/export/cubic-paper.pdf -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ