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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>.

Debian                                           August 6, 2019                                    CC_NEWRENO(4)