CC_NEWRENO(4)

NAME
cc_newreno - NewReno Congestion Control Algorithm

SYNOPSIS
#include <netinet/cc/cc_newreno.h>

DESCRIPTION
The NewReno congestion control algorithm is the default for TCP. Details about the algorithm can be found in RFC5681.

Socket Options
The cc_newreno module supports a number of socket options under TCP_CCALGOOPT (refer to tcp(4) and moc_cc(9) for details) which can be set with setsockopt(2) and tested with getsockopt(2). The cc_newreno socket options use this structure defined in <sys/netinet/cc/cc_newreno.h>:

    struct cc_newreno_opts {
    	int name;
    	uint32_t val;
    }

CC_NEWRENO_BETA
    Multiplicative window decrease factor, specified as a percentage, applied to the congestion window in response to a congestion signal per: cwnd = (cwnd * CC_NEWRENO_BETA) / 100. Default is 50.

CC_NEWRENO_BETA_ECN
    Multiplicative window decrease factor, specified as a percentage, applied to the congestion window in response to an ECN congestion signal when net.inet.tcp.cc.abe=1 per: cwnd = (cwnd * CC_NEWRENO_BETA_ECN) / 100. Default is 80.

MIB Variables
The algorithm exposes these variables in the net.inet.tcp.cc.newreno branch of the sysctl(3) MIB:

beta
    Multiplicative window decrease factor, specified as a percentage, applied to the congestion window in response to a congestion signal per: cwnd = (cwnd * beta) / 100. Default is 50.

beta_ecn
    Multiplicative window decrease factor, specified as a percentage, applied to the congestion window in response to an ECN congestion signal when net.inet.tcp.cc.abe=1 per: cwnd = (cwnd * beta_ecn) / 100. Default is 80.

SEE ALSO
cc_chd(4), cc_cubic(4), cc_hd(4), cc_htcp(4), cc_vegas(4), mod_cc(4), tcp(4), mod_cc(9) Mark Allman, Vern Paxson, Ethan Blanton, TCP Congestion Control, RFC 5681. Naeem Khademi, Michael Welzl, Grenville Armitage, Gorry Fairhurst, TCP Alternative Backoff with ECN (ABE), internet draft, February 2018, draft-ietf-tcpm-alternativebackoff-ecn, work in progress.

ACKNOWLEDGEMENTS
Development and testing of this software were made possible in part by grants from the FreeBSD Foundation and Cisco University Research Program Fund at Community Foundation Silicon Valley.

HISTORY
The cc_newreno congestion control algorithm first appeared in its modular form in FreeBSD 9.0.

The module was first released in 2007 by James Healy and Lawrence Stewart whilst working on the NewTCP research project at Swinburne University of Technology's Centre for Advanced Internet Architectures, Melbourne, Australia, which was made possible in part by a grant from the Cisco University Research Program Fund at Community Foundation Silicon Valley. More details are available at:

http://caia.swin.edu.au/urp/newtcp/

AUTHORS
-nosplit The cc_newreno congestion control module was written by James Healy <jimmy@deefa.com>, Lawrence Stewart <lstewart@FreeBSD.org> and David Hayes <david.hayes@ieee.org>.

Support for TCP ABE was added by Tom Jones <tj@enoti.me>.

This manual page was written by Lawrence Stewart <lstewart@FreeBSD.org>.