1 files changed, 714 insertions, 0 deletions
diff --git a/libtransport/src/protocols/raaqm.cc b/libtransport/src/protocols/raaqm.cc
new file mode 100644
index 000000000..8a38f8ccf
--- /dev/null
+++ b/libtransport/src/protocols/raaqm.cc
@@ -0,0 +1,714 @@
+/*
+ * 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) {
+  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
+  ConsumerContentObjectCallback *callback_content_object = VOID_HANDLER;
+  socket_->getSocketOption(ConsumerCallbacksOptions::CONTENT_OBJECT_INPUT,
+                           &callback_content_object);
+  if (*callback_content_object) {
+    (*callback_content_object)(*socket_->getInterface(), *content_object);
+  }
+
+  ConsumerInterestCallback *callback_interest = VOID_HANDLER;
+  socket_->getSocketOption(ConsumerCallbacksOptions::INTEREST_SATISFIED,
+                           &callback_interest);
+  if (*callback_interest) {
+    (*callback_interest)(*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();
+  ConsumerInterestCallback *callback = VOID_HANDLER;
+  if (TRANSPORT_EXPECT_TRUE(interest_retransmissions_[segment & mask] <
+                            max_rtx)) {
+    stats_->updateRetxCount(1);
+
+    callback = VOID_HANDLER;
+    socket_->getSocketOption(ConsumerCallbacksOptions::INTEREST_RETRANSMISSION,
+                             &callback);
+    if (*callback) {
+      (*callback)(*socket_->getInterface(), *interest);
+    }
+
+    callback = VOID_HANDLER;
+    socket_->getSocketOption(ConsumerCallbacksOptions::INTEREST_OUTPUT,
+                             &callback);
+    if (*callback) {
+      (*callback)(*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;
+  }
+
+  ConsumerInterestCallback *callback = VOID_HANDLER;
+  socket_->getSocketOption(ConsumerCallbacksOptions::INTEREST_EXPIRED,
+                           &callback);
+  if (*callback) {
+    (*callback)(*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);
+
+    callback = VOID_HANDLER;
+    socket_->getSocketOption(ConsumerCallbacksOptions::INTEREST_RETRANSMISSION,
+                             &callback);
+    if (*callback) {
+      (*callback)(*socket_->getInterface(), *interest);
+    }
+
+    callback = VOID_HANDLER;
+    socket_->getSocketOption(ConsumerCallbacksOptions::INTEREST_OUTPUT,
+                             &callback);
+    if (*callback) {
+      (*callback)(*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() {
+  if (TRANSPORT_EXPECT_FALSE(!is_running_ && !is_first_)) {
+    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()));
+    TRANSPORT_LOGD("Window full, retransmit one content interest");
+    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()));
+      TRANSPORT_LOGD("Retransmit content interest");
+      interest_to_retransmit_.pop();
+    } else {
+      index = index_manager_->getNextSuffix();
+      if (index == IndexManager::invalid_index) {
+        break;
+      }
+
+      sendInterest(index);
+      TRANSPORT_LOGD("Send content interest %u", index);
+    }
+  }
+}
+
+void 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);
+
+  ConsumerInterestCallback *callback = VOID_HANDLER;
+  socket_->getSocketOption(ConsumerCallbacksOptions::INTEREST_OUTPUT,
+                           &callback);
+  if (*callback) {
+    callback->operator()(*socket_->getInterface(), *interest);
+  }
+
+  if (TRANSPORT_EXPECT_FALSE(!is_running_ && !is_first_)) {
+    return;
+  }
+
+  // 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));
+}
+
+void RaaqmTransportProtocol::sendInterest(Interest::Ptr &&interest) {
+  interests_in_flight_++;
+  interest_retransmissions_[interest->getName().getSuffix() & mask]++;
+
+  portal_->sendInterest(std::move(interest));
+}
+
+void RaaqmTransportProtocol::onContentReassembled(std::error_code ec) {
+  rate_estimator_->onDownloadFinished();
+  TransportProtocol::onContentReassembled(ec);
+}
+
+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());
+    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
+  ConsumerTimerCallback *stats_callback = VOID_HANDLER;
+  socket_->getSocketOption(ConsumerCallbacksOptions::STATS_SUMMARY,
+                           &stats_callback);
+  if (*stats_callback) {
+    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_callback)(*socket_->getInterface(), *stats_);
+      t0_ = utils::SteadyClock::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