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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, and Ethan Blanton, TCP Congestion Control, RFC 5681.

     Naeem Khademi, Michael Welzl, Grenville Armitage, and Gorry Fairhurst, TCP Alternative Backoff with ECN
     (ABE), RFC 8511.


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
     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>.