bool PieQueueDisc::DropEarly()

in simulation/src/traffic-control/model/pie-queue-disc.cc [270:332]

• 53 lines of code
• 15 McCabe index (conditional complexity)

bool PieQueueDisc::DropEarly (Ptr<QueueDiscItem> item, uint32_t qSize)
{
  NS_LOG_FUNCTION (this << item << qSize);
  if (m_burstAllowance.GetSeconds () > 0)
    {
      // If there is still burst_allowance left, skip random early drop.
      return false;
    }

  if (m_burstState == NO_BURST)
    {
      m_burstState = IN_BURST_PROTECTING;
      m_burstAllowance = m_maxBurst;
    }

  double p = m_dropProb;

  uint32_t packetSize = item->GetSize ();

  if (GetMaxSize ().GetUnit () == QueueSizeUnit::BYTES)
    {
      p = p * packetSize / m_meanPktSize;
    }

  // Safeguard PIE to be work conserving (Section 4.1 of RFC 8033)
  if ((m_qDelayOld.GetSeconds () < (0.5 * m_qDelayRef.GetSeconds ())) && (m_dropProb < 0.2))
    {
      return false;
    }
  else if (GetMaxSize ().GetUnit () == QueueSizeUnit::BYTES && qSize <= 2 * m_meanPktSize)
    {
      return false;
    }
  else if (GetMaxSize ().GetUnit () == QueueSizeUnit::PACKETS && qSize <= 2)
    {
      return false;
    }

  if (m_useDerandomization)
    {
      if (m_dropProb == 0)
        {
          m_accuProb = 0;
        }
      m_accuProb += m_dropProb;
      if (m_accuProb < 0.85)
        {
          return false;
        }
      else if (m_accuProb >= 8.5)
        {
          return true;
        }
    }

  double u =  m_uv->GetValue ();
  if (u > p)
    {
      return false;
    }

  return true;
}