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#Congestion Control

First Loss

fl_phase
The first loss occurs in which phase, slow start or congestion avoid. The value is {ss|cong}.

fl_cwnd
The congestion window size when first loss happens. The unit is MSS.

fl_rtt
The RTT when first loss happens. The unit is ms.

Slow Start

There are three kinds of slow start algorithms used by Cubic.

  • Standard
  • ACK Train Length
  • Delay Increase

Besides, when slow start quits due to loss or connection close, we call it Abort.

STANDARD

std_ss_cnt
The number of completed Standard slow start.

std_ss_time
Average time of Standard slow start. The unit is RTT.

std_start_cwnd
Average start cwnd of Standard slow start. The unit is MSS.

std_end_cwnd
Average end cwnd of Standard slow start. The unit is MSS.

ACK TRAIN LENGTH

ack_ss_cnt
The number of completed ACK Train Length slow start.

ack_ss_time
Average time of ACK Train Length slow start. The unit is RTT.

ack_start_cwnd
Average start cwnd of ACK Train Length slow start. The unit is MSS.

ack_end_cwnd
Average end cwnd of ACK Train Length slow start. The unit is MSS.

DELAY INCREASE

delay_ss_cnt
The number of completed Delay Increase slow start.

delay_ss_time
Average time of Delay Increase slow start. The unit is RTT.

delay_start_cwnd
Average start cwnd of Delay Increase slow start. The unit is MSS.

delay_end_cwnd
Average end cwnd of Delay Increase slow start. The unit is MSS.

ABORT

abort_ss_cnt
The number of unfinished slow start.

abort_ss_time
Average time of Abort slow start. The unit is RTT.

abort_start_cwnd
Average start cwnd of Abort slow start. The unit is MSS.

abort_end_cwnd
Average end cwnd of Abort slow start. The unit is MSS.

Cong Avoid

Cubic uses a cubic function of the elapsed time from the last congestion event. The region between two continuous congestion events is called an epoch. So actually the congestion avoidance of Cubic is composed by serveral epochs.

EPOCH PHASE

An epoch period consists of three phases:

  • Searching phase, ramps up to the window size before the last congestion event.
  • Stable phase, allows the window size to stabilize for a period.
  • Max probing phase, probes for more bandwidth.

epoch_cnt
The number of epochs experienced by a connection.

epoch_time
Total time of epochs. The unit is RTT.

search_cnt
The number of searching phases experienced by a connnection.

search_time
Total time of searching phases. The unit is RTT.

probe_cnt
The number of probing phases experienced by a connection.

probe_time
Total time of probing phases. The unit is RTT.

EPOCH POINT

ep_start_cnt
The number of epochs' start points.

ep_start_cwnd
Average cwnd of epochs' start points.

ep_start_rtt
Average RTT of epochs' start points.

ep_steady_cnt
The number of epochs' steady points.

ep_steady_cwnd
Average cwnd of epochs' steady points.

ep_steady_rtt
Average RTT of epochs' steady points.

ep_end_cnt
The number of epochs' end points.

ep_end_cwnd
Average cwnd of epochs' end points.

ep_end_rtt
Average RTT of epochs' end points.

Advanced CC

Tcpdive uses five kinds of critical points to depict the fluctuation of a connection. A critial point looks like:

[point] DATE local remote id cwnd rtt time msg

point
The name of a critical point.

  • SS start, enter slow start.
  • SS end, exit slow start.
  • EP start, start point of an epoch.
  • EP steady, stable point of an epoch.
  • EP end, end point of an epoch.

DATE
year/month/day

local
DIP:DPORT, ip and port of the server.

remote
SIP:SPORT, ip and port of the client.

id
ISN of the server.

cwnd
Congestion window size, the unit is MSS.

rtt
Round trip time, the unit is ms.

time
Time elapsed from the establishment of a connection, the unit is ms.

msg
The messages conveyed by a critical point.

  • null, nothing.
  • std, use Standard slow start.
  • ack, use ACK Train Length slow start.
  • delay, use Delay Increase slow start.
  • abort, slow start aborts.
  • close, the connection is closing.
  • search, in searching phase of an epoch.
  • probe, in probing phase of an epoch.