A Discrete-Event Network Simulator
API
tcp-bbr.h
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1 /*
2  * Copyright (c) 2018 NITK Surathkal
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation;
7  *
8  * This program is distributed in the hope that it will be useful,
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11  * GNU General Public License for more details.
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14  * along with this program; if not, write to the Free Software
15  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
16  *
17  * Authors: Vivek Jain <jain.vivek.anand@gmail.com>
18  * Viyom Mittal <viyommittal@gmail.com>
19  * Mohit P. Tahiliani <tahiliani@nitk.edu.in>
20  */
21 
22 #ifndef TCPBBR_H
23 #define TCPBBR_H
24 
25 #include "tcp-congestion-ops.h"
26 #include "windowed-filter.h"
27 
28 #include "ns3/data-rate.h"
29 #include "ns3/random-variable-stream.h"
30 #include "ns3/traced-value.h"
31 
33 
34 namespace ns3
35 {
36 
45 class TcpBbr : public TcpCongestionOps
46 {
47  public:
51  static const uint8_t GAIN_CYCLE_LENGTH = 8;
52 
57  const static double PACING_GAIN_CYCLE[];
62  static TypeId GetTypeId();
63 
67  TcpBbr();
68 
73  TcpBbr(const TcpBbr& sock);
74 
78  enum BbrMode_t
79  {
84  };
85 
86  typedef WindowedFilter<DataRate,
88  uint32_t,
89  uint32_t>
91 
95  static const char* const BbrModeName[BBR_PROBE_RTT + 1];
96 
103  virtual void SetStream(uint32_t stream);
104 
105  std::string GetName() const override;
106  bool HasCongControl() const override;
109  const TcpRateOps::TcpRateSample& rs) override;
111  const TcpSocketState::TcpCongState_t newState) override;
112  void CwndEvent(Ptr<TcpSocketState> tcb, const TcpSocketState::TcpCAEvent_t event) override;
113  uint32_t GetSsThresh(Ptr<const TcpSocketState> tcb, uint32_t bytesInFlight) override;
114  Ptr<TcpCongestionOps> Fork() override;
115 
116  protected:
122 
126  void AdvanceCyclePhase();
127 
135 
141 
147 
154 
158  void EnterDrain();
159 
163  void EnterProbeBW();
164 
168  void EnterProbeRTT();
169 
173  void EnterStartup();
174 
179  void ExitProbeRTT();
180 
185  uint32_t GetBbrState();
186 
191  double GetPacingGain();
192 
197  double GetCwndGain();
198 
204 
211 
218  uint32_t InFlight(Ptr<TcpSocketState> tcb, double gain);
219 
223  void InitFullPipe();
224 
230 
234  void InitRoundCounting();
235 
243 
249 
257 
263 
270 
277 
283  void SetPacingRate(Ptr<TcpSocketState> tcb, double gain);
284 
290 
297 
304 
311 
318 
324 
330 
335  void SetBbrState(BbrMode_t state);
336 
341  uint32_t AckAggregationCwnd();
342 
349 
350  private:
351  BbrMode_t m_state{BbrMode_t::BBR_STARTUP};
355  double m_pacingGain{0};
356  double m_cWndGain{0};
357  double m_highGain{0};
358  bool m_isPipeFilled{false};
359  uint32_t m_minPipeCwnd{
360  0};
361  uint32_t m_roundCount{0};
362  bool m_roundStart{false};
363  uint32_t m_nextRoundDelivered{0};
367  Seconds(0)};
369  bool m_probeRttRoundDone{false};
370  bool m_packetConservation{false};
371  uint32_t m_priorCwnd{0};
372  bool m_idleRestart{false};
373  uint32_t m_targetCWnd{0};
375  uint32_t m_fullBandwidthCount{0};
377  Time::Max()};
379  uint32_t m_sendQuantum{
380  0};
382  uint32_t m_cycleIndex{0};
383  bool m_rtPropExpired{false};
387  Seconds(0)};
388  bool m_isInitialized{false};
390  uint64_t m_delivered{0};
391  uint32_t m_appLimited{
392  0};
394  0};
395  uint32_t m_extraAckedGain{1};
396  uint32_t m_extraAcked[2]{0, 0};
397  uint32_t m_extraAckedWinRtt{0};
400  1 << 17};
401  uint32_t m_extraAckedIdx{0};
403  uint32_t m_ackEpochAcked{0};
404  bool m_hasSeenRtt{false};
405 };
406 
407 } // namespace ns3
408 #endif // TCPBBR_H
Class for representing data rates.
Definition: data-rate.h:89
Tests whether BBR sets correct value of pacing and cwnd gain based on different state.
Definition: tcp-bbr-test.cc:87
BBR congestion control algorithm.
Definition: tcp-bbr.h:46
MaxBandwidthFilter_t m_maxBwFilter
Maximum bandwidth filter.
Definition: tcp-bbr.h:352
bool m_hasSeenRtt
Have we seen RTT sample yet?
Definition: tcp-bbr.h:404
double m_cWndGain
The dynamic congestion window gain factor.
Definition: tcp-bbr.h:356
void ModulateCwndForProbeRTT(Ptr< TcpSocketState > tcb)
Modulates congestion window in BBR_PROBE_RTT.
Definition: tcp-bbr.cc:553
uint32_t m_nextRoundDelivered
Denotes the end of a packet-timed round trip.
Definition: tcp-bbr.h:363
BbrMode_t
BBR has the following 4 modes for deciding how fast to send:
Definition: tcp-bbr.h:79
@ BBR_PROBE_RTT
Cut inflight to min to probe min_rtt.
Definition: tcp-bbr.h:83
@ BBR_DRAIN
Drain any queue created during startup.
Definition: tcp-bbr.h:81
@ BBR_STARTUP
Ramp up sending rate rapidly to fill pipe.
Definition: tcp-bbr.h:80
@ BBR_PROBE_BW
Discover, share bw: pace around estimated bw.
Definition: tcp-bbr.h:82
uint32_t m_roundCount
Count of packet-timed round trips.
Definition: tcp-bbr.h:361
uint32_t m_priorCwnd
The last-known good congestion window.
Definition: tcp-bbr.h:371
uint32_t m_extraAckedWinRttLength
Window length of extra acked window.
Definition: tcp-bbr.h:398
virtual void SetStream(uint32_t stream)
Assign a fixed random variable stream number to the random variables used by this model.
Definition: tcp-bbr.cc:142
TcpBbr()
Constructor.
Definition: tcp-bbr.cc:82
uint32_t m_extraAckedIdx
Current index in extra acked array.
Definition: tcp-bbr.h:401
Time m_probeRtPropStamp
The wall clock time at which the current BBR.RTProp sample was obtained.
Definition: tcp-bbr.h:366
std::string GetName() const override
Get the name of the congestion control algorithm.
Definition: tcp-bbr.cc:684
void CongControl(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateConnection &rc, const TcpRateOps::TcpRateSample &rs) override
Called when packets are delivered to update cwnd and pacing rate.
Definition: tcp-bbr.cc:697
bool m_rtPropExpired
A boolean recording whether the BBR.RTprop has expired.
Definition: tcp-bbr.h:383
void CwndEvent(Ptr< TcpSocketState > tcb, const TcpSocketState::TcpCAEvent_t event) override
Trigger events/calculations on occurrence of congestion window event.
Definition: tcp-bbr.cc:752
uint32_t GetSsThresh(Ptr< const TcpSocketState > tcb, uint32_t bytesInFlight) override
Get the slow start threshold after a loss event.
Definition: tcp-bbr.cc:784
uint32_t m_bandwidthWindowLength
A constant specifying the length of the BBR.BtlBw max filter window, default 10 packet-timed round tr...
Definition: tcp-bbr.h:353
double m_highGain
A constant specifying highest gain factor, default is 2.89.
Definition: tcp-bbr.h:357
Time m_probeRttDuration
A constant specifying the minimum duration for which ProbeRTT state, default 200 millisecs.
Definition: tcp-bbr.h:364
void CheckCyclePhase(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Checks whether to advance pacing gain in BBR_PROBE_BW state, and if allowed calls AdvanceCyclePhase (...
Definition: tcp-bbr.cc:284
uint32_t AckAggregationCwnd()
Find Cwnd increment based on ack aggregation.
Definition: tcp-bbr.cc:476
bool m_idleRestart
When restarting from idle, set it true.
Definition: tcp-bbr.h:372
Ptr< UniformRandomVariable > m_uv
Uniform Random Variable.
Definition: tcp-bbr.h:389
Time m_rtPropStamp
The wall clock time at which the current BBR.RTProp sample was obtained.
Definition: tcp-bbr.h:386
void UpdateBtlBw(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Updates maximum bottleneck.
Definition: tcp-bbr.cc:614
static TypeId GetTypeId()
Get the type ID.
Definition: tcp-bbr.cc:36
uint32_t m_minPipeCwnd
The minimal congestion window value BBR tries to target, default 4 Segment size.
Definition: tcp-bbr.h:359
Ptr< TcpCongestionOps > Fork() override
Copy the congestion control algorithm across sockets.
Definition: tcp-bbr.cc:792
uint32_t GetBbrState()
Gets BBR state.
Definition: tcp-bbr.cc:663
bool HasCongControl() const override
Returns true when Congestion Control Algorithm implements CongControl.
Definition: tcp-bbr.cc:690
double GetCwndGain()
Gets current cwnd gain.
Definition: tcp-bbr.cc:670
void UpdateRound(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Updates round counting related variables.
Definition: tcp-bbr.cc:597
BbrMode_t m_state
Current state of BBR state machine.
Definition: tcp-bbr.h:351
bool m_roundStart
A boolean that BBR sets to true once per packet-timed round trip.
Definition: tcp-bbr.h:362
void AdvanceCyclePhase()
Advances pacing gain using cycle gain algorithm, while in BBR_PROBE_BW state.
Definition: tcp-bbr.cc:255
void EnterProbeBW()
Updates variables specific to BBR_PROBE_BW state.
Definition: tcp-bbr.cc:328
double GetPacingGain()
Gets current pacing gain.
Definition: tcp-bbr.cc:677
uint64_t m_delivered
The total amount of data in bytes delivered so far.
Definition: tcp-bbr.h:390
void InitPacingRate(Ptr< TcpSocketState > tcb)
Initializes the pacing rate.
Definition: tcp-bbr.cc:167
bool IsNextCyclePhase(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Checks whether to move to next value of pacing gain while in BBR_PROBE_BW.
Definition: tcp-bbr.cc:264
bool m_isInitialized
Set to true after first time initializtion variables.
Definition: tcp-bbr.h:388
void RestoreCwnd(Ptr< TcpSocketState > tcb)
Helper to restore the last-known good congestion window.
Definition: tcp-bbr.cc:390
bool ModulateCwndForRecovery(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Modulates congestion window in CA_RECOVERY.
Definition: tcp-bbr.cc:535
double m_pacingGain
The dynamic pacing gain factor.
Definition: tcp-bbr.h:355
static const char *const BbrModeName[BBR_PROBE_RTT+1]
Literal names of BBR mode for use in log messages.
Definition: tcp-bbr.h:95
void UpdateRTprop(Ptr< TcpSocketState > tcb)
Updates minimum RTT.
Definition: tcp-bbr.cc:355
void CheckDrain(Ptr< TcpSocketState > tcb)
Checks whether its time to enter BBR_DRAIN or BBR_PROBE_BW state.
Definition: tcp-bbr.cc:339
void SetBbrState(BbrMode_t state)
Sets BBR state.
Definition: tcp-bbr.cc:654
void HandleRestartFromIdle(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Updates pacing rate if socket is restarting from idle state.
Definition: tcp-bbr.cc:205
static const double PACING_GAIN_CYCLE[]
BBR uses an eight-phase cycle with the given pacing_gain value in the BBR ProbeBW gain cycle.
Definition: tcp-bbr.h:57
WindowedFilter< DataRate, MaxFilter< DataRate >, uint32_t, uint32_t > MaxBandwidthFilter_t
Definition of max bandwidth filter.
Definition: tcp-bbr.h:90
bool m_isPipeFilled
A boolean that records whether BBR has filled the pipe.
Definition: tcp-bbr.h:358
void EnterStartup()
Updates variables specific to BBR_STARTUP state.
Definition: tcp-bbr.cc:196
void InitRoundCounting()
Initializes the round counting related variables.
Definition: tcp-bbr.cc:149
void InitFullPipe()
Initializes the full pipe estimator.
Definition: tcp-bbr.cc:158
void UpdateAckAggregation(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Estimates max degree of aggregation.
Definition: tcp-bbr.cc:491
uint32_t m_txItemDelivered
The number of bytes already delivered at the time of new packet transmission.
Definition: tcp-bbr.h:393
bool m_packetConservation
Enable/Disable packet conservation mode.
Definition: tcp-bbr.h:370
uint32_t InFlight(Ptr< TcpSocketState > tcb, double gain)
Estimates the target value for congestion window.
Definition: tcp-bbr.cc:237
uint32_t m_extraAckedWinRtt
Age of extra acked in rtt.
Definition: tcp-bbr.h:397
void SetPacingRate(Ptr< TcpSocketState > tcb, double gain)
Updates pacing rate based on network model.
Definition: tcp-bbr.cc:219
void SaveCwnd(Ptr< const TcpSocketState > tcb)
Helper to remember the last-known good congestion window or the latest congestion window unmodulated ...
Definition: tcp-bbr.cc:376
void EnterDrain()
Updates variables specific to BBR_DRAIN state.
Definition: tcp-bbr.cc:319
void CongestionStateSet(Ptr< TcpSocketState > tcb, const TcpSocketState::TcpCongState_t newState) override
Trigger events/calculations specific to a congestion state.
Definition: tcp-bbr.cc:709
Time m_probeRttDoneStamp
Time to exit from BBR_PROBE_RTT state.
Definition: tcp-bbr.h:368
uint32_t m_extraAcked[2]
Maximum excess data acked in epoch.
Definition: tcp-bbr.h:396
Time m_rtProp
Estimated two-way round-trip propagation delay of the path, estimated from the windowed minimum recen...
Definition: tcp-bbr.h:376
uint32_t m_appLimited
The index of the last transmitted packet marked as application-limited.
Definition: tcp-bbr.h:391
void UpdateModelAndState(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Updates BBR network model (Maximum bandwidth and minimum RTT).
Definition: tcp-bbr.cc:632
void UpdateControlParameters(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Updates control parameters congestion windowm, pacing rate, send quantum.
Definition: tcp-bbr.cc:645
Time m_ackEpochTime
Starting of ACK sampling epoch time.
Definition: tcp-bbr.h:402
Time m_cycleStamp
Last time gain cycle updated.
Definition: tcp-bbr.h:381
void CheckFullPipe(const TcpRateOps::TcpRateSample &rs)
Identifies whether pipe or BDP is already full.
Definition: tcp-bbr.cc:294
void EnterProbeRTT()
Updates variables specific to BBR_PROBE_RTT state.
Definition: tcp-bbr.cc:367
DataRate m_fullBandwidth
Value of full bandwidth recorded.
Definition: tcp-bbr.h:374
void HandleProbeRTT(Ptr< TcpSocketState > tcb)
Handles the steps for BBR_PROBE_RTT state.
Definition: tcp-bbr.cc:411
Time m_rtPropFilterLen
A constant specifying the length of the RTProp min filter window, default 10 secs.
Definition: tcp-bbr.h:384
uint32_t m_targetCWnd
Target value for congestion window, adapted to the estimated BDP.
Definition: tcp-bbr.h:373
uint32_t m_sendQuantum
The maximum size of a data aggregate scheduled and transmitted together.
Definition: tcp-bbr.h:379
void SetSendQuantum(Ptr< TcpSocketState > tcb)
Updates send quantum based on the network model.
Definition: tcp-bbr.cc:462
uint32_t m_ackEpochAckedResetThresh
Max allowed val for m_ackEpochAcked, after which sampling epoch is reset.
Definition: tcp-bbr.h:399
void ExitProbeRTT()
Called on exiting from BBR_PROBE_RTT state, it eithers invoke EnterProbeBW () or EnterStartup ()
Definition: tcp-bbr.cc:397
bool m_probeRttRoundDone
True when it is time to exit BBR_PROBE_RTT.
Definition: tcp-bbr.h:369
uint32_t m_fullBandwidthCount
Count of full bandwidth recorded consistently.
Definition: tcp-bbr.h:375
void UpdateTargetCwnd(Ptr< TcpSocketState > tcb)
Updates target congestion window.
Definition: tcp-bbr.cc:469
uint32_t m_cycleIndex
Current index of gain cycle.
Definition: tcp-bbr.h:382
uint32_t m_extraAckedGain
Gain factor for adding extra ack to cwnd.
Definition: tcp-bbr.h:395
void CheckProbeRTT(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
This method handles the steps related to the ProbeRTT state.
Definition: tcp-bbr.cc:440
static const uint8_t GAIN_CYCLE_LENGTH
The number of phases in the BBR ProbeBW gain cycle.
Definition: tcp-bbr.h:51
void SetCwnd(Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
Updates congestion window based on the network model.
Definition: tcp-bbr.cc:563
uint32_t m_ackEpochAcked
Bytes ACked in sampling epoch.
Definition: tcp-bbr.h:403
friend class TcpBbrCheckGainValuesTest
TcpBbrCheckGainValuesTest friend class (for tests).
Definition: tcp-bbr.h:121
Congestion control abstract class.
TcpCAEvent_t
Congestion avoidance events.
TcpCongState_t
Definition of the Congestion state machine.
Simulation virtual time values and global simulation resolution.
Definition: nstime.h:105
static Time Max()
Maximum representable Time Not to be confused with Max(Time,Time).
Definition: nstime.h:297
a unique identifier for an interface.
Definition: type-id.h:59
Construct a windowed filter.
void(* DataRate)(DataRate oldValue, DataRate newValue)
TracedValue callback signature for DataRate.
Definition: data-rate.h:327
Time Seconds(double value)
Construct a Time in the indicated unit.
Definition: nstime.h:1326
Time MilliSeconds(uint64_t value)
Construct a Time in the indicated unit.
Definition: nstime.h:1338
Every class exported by the ns3 library is enclosed in the ns3 namespace.
Compares two values.
Information about the connection rate.
Definition: tcp-rate-ops.h:174
Rate Sample structure.
Definition: tcp-rate-ops.h:140