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tcp_bbr_load="YES"
To enable the TCP stack you must place the following line in the sysctl.conf(5):
net.inet.tcp.functions_default=bbr
The core design of BBR is about creating a model graph of the network path by estimating the maximum BW and minimum RTT on each ACK.
| cwnd | |
| Cwnd controls, for example "target cwnd rtt measurement" and "BBR initial window". | |
| measure | |
| Measurement controls. | |
| pacing | |
| Connection pacing controls. | |
| policer | |
| Policer controls, for example "false detection threshold" and "loss threshold". | |
| probertt | |
| Probe RTT controls. | |
| startup | |
| Startup controls. | |
| states | |
| State controls. | |
| timeout | |
| Time out controls. | |
Besides the variables within the above scopes the following variables are also exposed in the net.inet.tcp.bbr branch:
| clrlost | |
| Clear lost counters. | |
| software_pacing | |
| Total number of software paced flows. | |
| hdwr_pacing | |
| Total number of hardware paced flows. | |
| enob_no_hdwr_pacing | |
| Total number of enobufs for non-hardware paced flows. | |
| enob_hdwr_pacing | |
| Total number of enobufs for hardware paced flows. | |
| rtt_tlp_thresh | |
| What divisor for TLP rtt/retran will be added (1=rtt, 2=1/2 rtt etc). | |
| reorder_fade | |
| Does reorder detection fade, if so how many ms (0 means never). | |
| reorder_thresh | |
| What factor for rack will be added when seeing reordering (shift right). | |
| bb_verbose | |
| Should BBR black box logging be verbose. | |
| sblklimit | |
| When do we start ignoring small sack blocks. | |
| resend_use_tso | |
| Can resends use TSO? | |
| data_after_close | |
| Do we hold off sending a RST until all pending data is ack'd. | |
| kill_paceout | |
| When we hit this many errors in a row, kill the session? | |
| error_paceout | |
| When we hit an error what is the min to pace out in usec's? | |
| cheat_rxt | |
| Do we burst 1ms between sends on retransmissions (like rack)? | |
| minrto | |
| Minimum RTO in ms. | |
, , , , , ACM Queue, Vol. 14, BBR: Congestion-Based Congestion Control, September / October 2016.
http://www.net.in.tum.de/fileadmin/bibtex/publications/papers/IFIP-Networking-2018-TCP-BBR.pdf, , , , , , IFIP Networking 2018, Towards a Deeper Understanding of TCP BBR Congestion Control, May 2018.
| TCP_BBR (4) | December 17, 2023 |
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