ECN (ABE)" proposal to the New Reno congestion control algorithm module.
ABE reduces the amount of congestion window reduction in response to
ECN-signalled congestion relative to the loss-inferred congestion response.
More details about ABE can be found in the Internet-Draft:
https://tools.ietf.org/html/draft-ietf-tcpm-alternativebackoff-ecn
The implementation introduces four new sysctls:
- net.inet.tcp.cc.abe defaults to 0 (disabled) and can be set to non-zero to
enable ABE for ECN-enabled TCP connections.
- net.inet.tcp.cc.newreno.beta and net.inet.tcp.cc.newreno.beta_ecn set the
multiplicative window decrease factor, specified as a percentage, applied to
the congestion window in response to a loss-based or ECN-based congestion
signal respectively. They default to the values specified in the draft i.e.
beta=50 and beta_ecn=80.
- net.inet.tcp.cc.abe_frlossreduce defaults to 0 (disabled) and can be set to
non-zero to enable the use of standard beta (50% by default) when repairing
loss during an ECN-signalled congestion recovery episode. It enables a more
conservative congestion response and is provided for the purposes of
experimentation as a result of some discussion at IETF 100 in Singapore.
The values of beta and beta_ecn can also be set per-connection by way of the
TCP_CCALGOOPT TCP-level socket option and the new CC_NEWRENO_BETA or
CC_NEWRENO_BETA_ECN CC algo sub-options.
Submitted by: Tom Jones <tj@enoti.me>
Tested by: Tom Jones <tj@enoti.me>, Grenville Armitage <garmitage@swin.edu.au>
Relnotes: Yes
Differential Revision: https://reviews.freebsd.org/D11616
mod_cc.4 and mod_cc.9 respectively to avoid any possible confusion with the cc.1
gcc man page. Update references to these man pages where required.
Requested by: Grenville Armitage
Approved by: re (kib)
MFC after: 3 days
FreeBSD" FreeBSD Foundation funded project.
- Add new man pages for the modular congestion control, Khelp and Hhook
frameworks (cc.4, cc.9, khelp.9 and hhook.9).
- Add new man pages for each available congestion control algorithm (cc_chd.4,
cc_cubic.4, cc_hd.4, cc_htcp.4, cc_newreno.4 and cc_vegas.4).
- Add a new man page for the Enhanced Round Trip Time (ERTT) Khelp module
(h_ertt.4).
- Update the TCP (tcp.4) man page to mention the TCP_CONGESTION socket option,
cross reference to cc.4 and remove references to the retired
"net.inet.tcp.newreno" sysctl MIB variable.
In collaboration with: David Hayes <dahayes at swin edu au> and
Grenville Armitage <garmitage at swin edu au>
Sponsored by: FreeBSD Foundation
MFC after: 3 months
