aboutsummaryrefslogtreecommitdiffstats
path: root/libtransport/src/protocols/raaqm.cc
blob: 8f9ccc4f097151019019f34749278908899020b8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
/*
 * Copyright (c) 2017-2019 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <hicn/transport/interfaces/socket_consumer.h>
#include <implementation/socket_consumer.h>
#include <protocols/errors.h>
#include <protocols/indexer.h>
#include <protocols/raaqm.h>

#include <cstdlib>
#include <fstream>

namespace transport {

namespace protocol {

using namespace interface;

RaaqmTransportProtocol::RaaqmTransportProtocol(
    implementation::ConsumerSocket *icn_socket)
    : TransportProtocol(icn_socket, new ByteStreamReassembly(icn_socket, this)),
      current_window_size_(1),
      interests_in_flight_(0),
      cur_path_(nullptr),
      t0_(utils::SteadyClock::now()),
      rate_estimator_(nullptr),
      schedule_interests_(true) {
  init();
}

RaaqmTransportProtocol::~RaaqmTransportProtocol() {
  if (rate_estimator_) {
    delete rate_estimator_;
  }
}

int RaaqmTransportProtocol::start() {
  if (rate_estimator_) {
    rate_estimator_->onStart();
  }

  if (!cur_path_) {
    // RAAQM
    double drop_factor;
    double minimum_drop_probability;
    uint32_t sample_number;
    uint32_t interest_lifetime;

    socket_->getSocketOption(RaaqmTransportOptions::DROP_FACTOR, drop_factor);
    socket_->getSocketOption(RaaqmTransportOptions::MINIMUM_DROP_PROBABILITY,
                             minimum_drop_probability);
    socket_->getSocketOption(RaaqmTransportOptions::SAMPLE_NUMBER,
                             sample_number);
    socket_->getSocketOption(GeneralTransportOptions::INTEREST_LIFETIME,
                             interest_lifetime);

    // Rate Estimation
    double alpha = 0.0;
    uint32_t batching_param = 0;
    uint32_t choice_param = 0;
    socket_->getSocketOption(RateEstimationOptions::RATE_ESTIMATION_ALPHA,
                             alpha);
    socket_->getSocketOption(
        RateEstimationOptions::RATE_ESTIMATION_BATCH_PARAMETER, batching_param);
    socket_->getSocketOption(RateEstimationOptions::RATE_ESTIMATION_CHOICE,
                             choice_param);

    if (choice_param == 1) {
      rate_estimator_ = new ALaTcpEstimator();
    } else {
      rate_estimator_ = new SimpleEstimator(alpha, batching_param);
    }

    socket_->getSocketOption(RateEstimationOptions::RATE_ESTIMATION_OBSERVER,
                             &rate_estimator_->observer_);

    // Current path
    auto cur_path = std::make_unique<RaaqmDataPath>(
        drop_factor, minimum_drop_probability, interest_lifetime * 1000,
        sample_number);
    cur_path_ = cur_path.get();
    path_table_[default_values::path_id] = std::move(cur_path);
  }

  portal_->setConsumerCallback(this);
  return TransportProtocol::start();
}

void RaaqmTransportProtocol::resume() { return TransportProtocol::resume(); }

void RaaqmTransportProtocol::reset() {
  // Set first segment to retrieve
  core::Name *name;
  socket_->getSocketOption(GeneralTransportOptions::NETWORK_NAME, &name);
  index_manager_->reset();
  index_manager_->setFirstSuffix(name->getSuffix());
  std::queue<Interest::Ptr> empty;
  std::swap(interest_to_retransmit_, empty);
  stats_->reset();

  // Reset reassembly component
  reassembly_protocol_->reInitialize();

  // Reset protocol variables
  interests_in_flight_ = 0;
  t0_ = utils::SteadyClock::now();
}

bool RaaqmTransportProtocol::verifyKeyPackets() {
  return index_manager_->onKeyToVerify();
}

void RaaqmTransportProtocol::increaseWindow() {
  // return;
  double max_window_size = 0.;
  socket_->getSocketOption(GeneralTransportOptions::MAX_WINDOW_SIZE,
                           max_window_size);
  if (current_window_size_ < max_window_size) {
    double gamma = 0.;
    socket_->getSocketOption(RaaqmTransportOptions::GAMMA_VALUE, gamma);

    current_window_size_ += gamma / current_window_size_;
    socket_->setSocketOption(GeneralTransportOptions::CURRENT_WINDOW_SIZE,
                             current_window_size_);
  }
  rate_estimator_->onWindowIncrease(current_window_size_);
}

void RaaqmTransportProtocol::decreaseWindow() {
  // return;
  double min_window_size = 0.;
  socket_->getSocketOption(GeneralTransportOptions::MIN_WINDOW_SIZE,
                           min_window_size);
  if (current_window_size_ > min_window_size) {
    double beta = 0.;
    socket_->getSocketOption(RaaqmTransportOptions::BETA_VALUE, beta);

    current_window_size_ = current_window_size_ * beta;
    if (current_window_size_ < min_window_size) {
      current_window_size_ = min_window_size;
    }

    socket_->setSocketOption(GeneralTransportOptions::CURRENT_WINDOW_SIZE,
                             current_window_size_);
  }
  rate_estimator_->onWindowDecrease(current_window_size_);
}

void RaaqmTransportProtocol::afterDataUnsatisfied(uint64_t segment) {
  // Decrease the window because the timeout happened
  decreaseWindow();
}

void RaaqmTransportProtocol::afterContentReception(
    const Interest &interest, const ContentObject &content_object) {
  updatePathTable(content_object);
  increaseWindow();
  updateRtt(interest.getName().getSuffix());
  rate_estimator_->onDataReceived((int)content_object.payloadSize() +
                                  (int)content_object.headerSize());
  // Set drop probablility and window size accordingly
  RAAQM();
}

void RaaqmTransportProtocol::init() {
  std::ifstream is(RAAQM_CONFIG_PATH);

  std::string line;
  raaqm_autotune_ = false;
  default_beta_ = default_values::beta_value;
  default_drop_ = default_values::drop_factor;
  beta_wifi_ = default_values::beta_value;
  drop_wifi_ = default_values::drop_factor;
  beta_lte_ = default_values::beta_value;
  drop_lte_ = default_values::drop_factor;
  wifi_delay_ = 1000;
  lte_delay_ = 15000;

  if (!is) {
    TRANSPORT_LOGW(
        "WARNING: RAAQM parameters not found at %s, set default values",
        RAAQM_CONFIG_PATH);
    return;
  }

  while (getline(is, line)) {
    std::string command;
    std::istringstream line_s(line);

    line_s >> command;

    if (command == ";") {
      continue;
    }

    if (command == "autotune") {
      std::string tmp;
      std::string val;
      line_s >> tmp >> val;
      if (val == "yes") {
        raaqm_autotune_ = true;
      } else {
        raaqm_autotune_ = false;
      }
      continue;
    }

    if (command == "lifetime") {
      std::string tmp;
      uint32_t lifetime;
      line_s >> tmp >> lifetime;
      socket_->setSocketOption(GeneralTransportOptions::INTEREST_LIFETIME,
                               lifetime);
      continue;
    }

    if (command == "retransmissions") {
      std::string tmp;
      uint32_t rtx;
      line_s >> tmp >> rtx;
      socket_->setSocketOption(GeneralTransportOptions::MAX_INTEREST_RETX, rtx);
      continue;
    }

    if (command == "beta") {
      std::string tmp;
      line_s >> tmp >> default_beta_;
      socket_->setSocketOption(RaaqmTransportOptions::BETA_VALUE,
                               default_beta_);
      continue;
    }

    if (command == "drop") {
      std::string tmp;
      line_s >> tmp >> default_drop_;
      socket_->setSocketOption(RaaqmTransportOptions::DROP_FACTOR,
                               default_drop_);
      continue;
    }

    if (command == "beta_wifi_") {
      std::string tmp;
      line_s >> tmp >> beta_wifi_;
      continue;
    }

    if (command == "drop_wifi_") {
      std::string tmp;
      line_s >> tmp >> drop_wifi_;
      continue;
    }

    if (command == "beta_lte_") {
      std::string tmp;
      line_s >> tmp >> beta_lte_;
      continue;
    }

    if (command == "drop_lte_") {
      std::string tmp;
      line_s >> tmp >> drop_lte_;
      continue;
    }

    if (command == "wifi_delay_") {
      std::string tmp;
      line_s >> tmp >> wifi_delay_;
      continue;
    }

    if (command == "lte_delay_") {
      std::string tmp;
      line_s >> tmp >> lte_delay_;
      continue;
    }
    if (command == "alpha") {
      std::string tmp;
      double rate_alpha = 0.0;
      line_s >> tmp >> rate_alpha;
      socket_->setSocketOption(RateEstimationOptions::RATE_ESTIMATION_ALPHA,
                               rate_alpha);
      continue;
    }

    if (command == "batching_parameter") {
      std::string tmp;
      uint32_t batching_param = 0;
      line_s >> tmp >> batching_param;
      socket_->setSocketOption(
          RateEstimationOptions::RATE_ESTIMATION_BATCH_PARAMETER,
          batching_param);
      continue;
    }

    if (command == "rate_estimator") {
      std::string tmp;
      uint32_t choice_param = 0;
      line_s >> tmp >> choice_param;
      socket_->setSocketOption(RateEstimationOptions::RATE_ESTIMATION_CHOICE,
                               choice_param);
      continue;
    }
  }

  is.close();
}

void RaaqmTransportProtocol::onContentObject(
    Interest::Ptr &&interest, ContentObject::Ptr &&content_object) {
  // Check whether makes sense to continue
  if (TRANSPORT_EXPECT_FALSE(!is_running_)) {
    return;
  }

  // Call application-defined callbacks
  if (*on_content_object_input_) {
    (*on_content_object_input_)(*socket_->getInterface(), *content_object);
  }

  if (*on_interest_satisfied_) {
    (*on_interest_satisfied_)(*socket_->getInterface(), *interest);
  }

  if (content_object->getPayloadType() == PayloadType::CONTENT_OBJECT) {
    stats_->updateBytesRecv(content_object->payloadSize());
  }

  onContentSegment(std::move(interest), std::move(content_object));
  scheduleNextInterests();
}

void RaaqmTransportProtocol::onContentSegment(
    Interest::Ptr &&interest, ContentObject::Ptr &&content_object) {
  uint32_t incremental_suffix = content_object->getName().getSuffix();

  // Decrease in-flight interests
  interests_in_flight_--;

  // Update stats
  if (!interest_retransmissions_[incremental_suffix & mask]) {
    afterContentReception(*interest, *content_object);
  }

  index_manager_->onContentObject(std::move(interest),
                                  std::move(content_object));
}

void RaaqmTransportProtocol::onPacketDropped(
    Interest::Ptr &&interest, ContentObject::Ptr &&content_object) {
  uint32_t max_rtx = 0;
  socket_->getSocketOption(GeneralTransportOptions::MAX_INTEREST_RETX, max_rtx);

  uint64_t segment = interest->getName().getSuffix();

  if (TRANSPORT_EXPECT_TRUE(interest_retransmissions_[segment & mask] <
                            max_rtx)) {
    stats_->updateRetxCount(1);

    if (*on_interest_retransmission_) {
      (*on_interest_retransmission_)(*socket_->getInterface(), *interest);
    }

    if (*on_interest_output_) {
      (*on_interest_output_)(*socket_->getInterface(), *interest);
    }

    if (!is_running_) {
      return;
    }

    interest_retransmissions_[segment & mask]++;
    interest_to_retransmit_.push(std::move(interest));
  } else {
    TRANSPORT_LOGE(
        "Stop: received not trusted packet %llu times",
        (unsigned long long)interest_retransmissions_[segment & mask]);
    onContentReassembled(
        make_error_code(protocol_error::max_retransmissions_error));
  }
}

void RaaqmTransportProtocol::onReassemblyFailed(std::uint32_t missing_segment) {

}

void RaaqmTransportProtocol::onTimeout(Interest::Ptr &&interest) {
  checkForStalePaths();

  const Name &n = interest->getName();

  TRANSPORT_LOGW("Timeout on content %s", n.toString().c_str());

  if (TRANSPORT_EXPECT_FALSE(!is_running_)) {
    return;
  }

  interests_in_flight_--;

  uint64_t segment = n.getSuffix();

  // Do not retransmit interests asking contents that do not exist.
  if (segment > index_manager_->getFinalSuffix()) {
    return;
  }

  if (*on_interest_timeout_) {
    (*on_interest_timeout_)(*socket_->getInterface(), *interest);
  }

  afterDataUnsatisfied(segment);

  uint32_t max_rtx = 0;
  socket_->getSocketOption(GeneralTransportOptions::MAX_INTEREST_RETX, max_rtx);

  if (TRANSPORT_EXPECT_TRUE(interest_retransmissions_[segment & mask] <
                            max_rtx)) {
    stats_->updateRetxCount(1);

    if (*on_interest_retransmission_) {
      (*on_interest_retransmission_)(*socket_->getInterface(), *interest);
    }

    if (*on_interest_output_) {
      (*on_interest_output_)(*socket_->getInterface(), *interest);
    }

    if (!is_running_) {
      return;
    }

    interest_retransmissions_[segment & mask]++;
    interest_to_retransmit_.push(std::move(interest));

    scheduleNextInterests();
  } else {
    TRANSPORT_LOGE("Stop: reached max retx limit.");
    onContentReassembled(std::make_error_code(std::errc(std::errc::io_error)));
  }
}

void RaaqmTransportProtocol::scheduleNextInterests() {
  bool cancel = (!is_running_ && !is_first_) || !schedule_interests_;
  if (TRANSPORT_EXPECT_FALSE(cancel)) {
    schedule_interests_ = true;
    return;
  }

  if (TRANSPORT_EXPECT_FALSE(interests_in_flight_ >= current_window_size_ &&
                             interest_to_retransmit_.size() > 0)) {
    // send at least one interest if there are retransmissions to perform and
    // there is no space left in the window
    sendInterest(std::move(interest_to_retransmit_.front()));
    interest_to_retransmit_.pop();
  }

  uint32_t index = IndexManager::invalid_index;

  // Send the interest needed for filling the window
  while (interests_in_flight_ < current_window_size_) {
    if (interest_to_retransmit_.size() > 0) {
      sendInterest(std::move(interest_to_retransmit_.front()));
      interest_to_retransmit_.pop();
    } else {
      index = index_manager_->getNextSuffix();
      if (index == IndexManager::invalid_index) {
        break;
      }

      sendInterest(index);
    }
  }
}

bool RaaqmTransportProtocol::sendInterest(std::uint64_t next_suffix) {
  auto interest = getPacket();
  core::Name *name;
  socket_->getSocketOption(GeneralTransportOptions::NETWORK_NAME, &name);
  name->setSuffix((uint32_t)next_suffix);
  interest->setName(*name);

  uint32_t interest_lifetime;
  socket_->getSocketOption(GeneralTransportOptions::INTEREST_LIFETIME,
                           interest_lifetime);
  interest->setLifetime(interest_lifetime);

  if (*on_interest_output_) {
    on_interest_output_->operator()(*socket_->getInterface(), *interest);
  }

  if (TRANSPORT_EXPECT_FALSE(!is_running_ && !is_first_)) {
    return false;
  }

  // This is set to ~0 so that the next interest_retransmissions_ + 1,
  // performed by sendInterest, will result in 0
  interest_retransmissions_[next_suffix & mask] = ~0;
  interest_timepoints_[next_suffix & mask] = utils::SteadyClock::now();

  sendInterest(std::move(interest));

  return true;
}

void RaaqmTransportProtocol::sendInterest(Interest::Ptr &&interest) {
  interests_in_flight_++;
  interest_retransmissions_[interest->getName().getSuffix() & mask]++;

  TRANSPORT_LOGD("Send interest %s", interest->getName().toString().c_str());
  portal_->sendInterest(std::move(interest));
}

void RaaqmTransportProtocol::onContentReassembled(std::error_code ec) {
  rate_estimator_->onDownloadFinished();
  TransportProtocol::onContentReassembled(ec);
  schedule_interests_ = false;
}

void RaaqmTransportProtocol::updateRtt(uint64_t segment) {
  if (TRANSPORT_EXPECT_FALSE(!cur_path_)) {
    throw std::runtime_error("RAAQM ERROR: no current path found, exit");
  } else {
    auto now = utils::SteadyClock::now();
    utils::Microseconds rtt = std::chrono::duration_cast<utils::Microseconds>(
        now - interest_timepoints_[segment & mask]);

    // Update stats
    updateStats((uint32_t)segment, rtt.count(), now);

    if (rate_estimator_) {
      rate_estimator_->onRttUpdate((double)rtt.count());
    }

    cur_path_->insertNewRtt(rtt.count(), now);
    cur_path_->smoothTimer();

    if (cur_path_->newPropagationDelayAvailable()) {
      checkDropProbability();
    }
  }
}

void RaaqmTransportProtocol::RAAQM() {
  if (!cur_path_) {
    throw errors::RuntimeException("ERROR: no current path found, exit");
    exit(EXIT_FAILURE);
  } else {
    // Change drop probability according to RTT statistics
    cur_path_->updateDropProb();

    double coin = ((double)rand() / (RAND_MAX));
    if (coin <= cur_path_->getDropProb()) {
      decreaseWindow();
    }
  }
}

void RaaqmTransportProtocol::updateStats(uint32_t suffix, uint64_t rtt,
                                         utils::TimePoint &now) {
  // Update RTT statistics
  stats_->updateAverageRtt(rtt);
  stats_->updateAverageWindowSize(current_window_size_);

  // Call statistics callback
  if (*stats_summary_) {
    auto dt = std::chrono::duration_cast<utils::Milliseconds>(now - t0_);

    uint32_t timer_interval_milliseconds = 0;
    socket_->getSocketOption(GeneralTransportOptions::STATS_INTERVAL,
                             timer_interval_milliseconds);
    if (dt.count() > timer_interval_milliseconds) {
      (*stats_summary_)(*socket_->getInterface(), *stats_);
      t0_ = now;
    }
  }
}

void RaaqmTransportProtocol::updatePathTable(
    const ContentObject &content_object) {
  uint32_t path_id = content_object.getPathLabel();

  if (path_table_.find(path_id) == path_table_.end()) {
    if (TRANSPORT_EXPECT_TRUE(cur_path_ != nullptr)) {
      // Create a new path with some default param

      if (TRANSPORT_EXPECT_FALSE(path_table_.empty())) {
        throw errors::RuntimeException(
            "[RAAQM] No path initialized for path table, error could be in "
            "default path initialization.");
      }

      // Initiate the new path default param
      auto new_path = std::make_unique<RaaqmDataPath>(
          *(path_table_.at(default_values::path_id)));

      // Insert the new path into hash table
      path_table_[path_id] = std::move(new_path);
    } else {
      throw errors::RuntimeException(
          "UNEXPECTED ERROR: when running,current path not found.");
    }
  }

  cur_path_ = path_table_[path_id].get();

  size_t header_size = content_object.headerSize();
  size_t data_size = content_object.payloadSize();

  // Update measurements for path
  cur_path_->updateReceivedStats(header_size + data_size, data_size);
}

void RaaqmTransportProtocol::checkDropProbability() {
  if (!raaqm_autotune_) {
    return;
  }

  unsigned int max_pd = 0;
  PathTable::iterator it;
  for (auto it = path_table_.begin(); it != path_table_.end(); ++it) {
    if (it->second->getPropagationDelay() > max_pd &&
        it->second->getPropagationDelay() != UINT_MAX &&
        !it->second->isStale()) {
      max_pd = it->second->getPropagationDelay();
    }
  }

  double drop_prob = 0;
  double beta = 0;
  if (max_pd < wifi_delay_) {  // only ethernet paths
    drop_prob = default_drop_;
    beta = default_beta_;
  } else if (max_pd < lte_delay_) {  // at least one wifi path
    drop_prob = drop_wifi_;
    beta = beta_wifi_;
  } else {  // at least one lte path
    drop_prob = drop_lte_;
    beta = beta_lte_;
  }

  double old_drop_prob = 0;
  double old_beta = 0;
  socket_->getSocketOption(RaaqmTransportOptions::BETA_VALUE, old_beta);
  socket_->getSocketOption(RaaqmTransportOptions::DROP_FACTOR, old_drop_prob);

  if (drop_prob == old_drop_prob && beta == old_beta) {
    return;
  }

  socket_->setSocketOption(RaaqmTransportOptions::BETA_VALUE, beta);
  socket_->setSocketOption(RaaqmTransportOptions::DROP_FACTOR, drop_prob);

  for (it = path_table_.begin(); it != path_table_.end(); it++) {
    it->second->setDropProb(drop_prob);
  }
}

void RaaqmTransportProtocol::checkForStalePaths() {
  if (!raaqm_autotune_) {
    return;
  }

  bool stale = false;
  PathTable::iterator it;
  for (it = path_table_.begin(); it != path_table_.end(); ++it) {
    if (it->second->isStale()) {
      stale = true;
      break;
    }
  }
  if (stale) {
    checkDropProbability();
  }
}

}  // end namespace protocol

}  // namespace transport