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Aligning ns-3's implementation of RED with that of Linux #41

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0626f46
Removed m_cautious from doenqueue()
piyushnh Jun 6, 2019
f613cf3
Removed all usages of m_cautious
piyushnh Jun 6, 2019
939fa88
made m_ptc more readable
piyushnh Jun 6, 2019
dd3313e
removed diff values of wq,they are absent in linux version
piyushnh Jun 6, 2019
f61bcdb
removed unnecessary checking of m_iswait
piyushnh Jun 6, 2019
17511c1
fixed dequeue logic of idle time handling
piyushnh Jun 6, 2019
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157 changes: 40 additions & 117 deletions src/traffic-control/model/red-queue-disc.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -350,17 +350,7 @@ RedQueueDisc::DoEnqueue (Ptr<QueueDiscItem> item)
{
NS_LOG_DEBUG ("RED Queue Disc is idle.");
Time now = Simulator::Now ();

if (m_cautious == 3)
{
double ptc = m_ptc * m_meanPktSize / m_idlePktSize;
m = uint32_t (ptc * (now - m_idleTime).GetSeconds ());
}
else
{
m = uint32_t (m_ptc * (now - m_idleTime).GetSeconds ());
}

m = uint32_t (m_pktTimeConst * (now - m_idleTime).GetSeconds ());
m_idle = 0;
}

Expand Down Expand Up @@ -455,8 +445,7 @@ RedQueueDisc::InitializeParams (void)
NS_LOG_FUNCTION (this);
NS_LOG_INFO ("Initializing RED params.");

m_cautious = 0;
m_ptc = m_linkBandwidth.GetBitRate () / (8.0 * m_meanPktSize);
m_pktTimeConst = m_linkBandwidth.GetBitRate () / (8.0 * m_meanPktSize);

if (m_isARED)
{
Expand All @@ -480,7 +469,7 @@ RedQueueDisc::InitializeParams (void)
m_minTh = 5.0;

// set m_minTh to max(m_minTh, targetqueue/2.0) [Ref: http://www.icir.org/floyd/papers/adaptiveRed.pdf]
double targetqueue = m_targetDelay.GetSeconds() * m_ptc;
double targetqueue = m_targetDelay.GetSeconds() * m_pktTimeConst;

if (m_minTh < targetqueue / 2.0 )
{
Expand Down Expand Up @@ -519,37 +508,6 @@ RedQueueDisc::InitializeParams (void)
}
m_idleTime = NanoSeconds (0);

/*
* If m_qW=0, set it to a reasonable value of 1-exp(-1/C)
* This corresponds to choosing m_qW to be of that value for
* which the packet time constant -1/ln(1-m)qW) per default RTT
* of 100ms is an order of magnitude more than the link capacity, C.
*
* If m_qW=-1, then the queue weight is set to be a function of
* the bandwidth and the link propagation delay. In particular,
* the default RTT is assumed to be three times the link delay and
* transmission delay, if this gives a default RTT greater than 100 ms.
*
* If m_qW=-2, set it to a reasonable value of 1-exp(-10/C).
*/
if (m_qW == 0.0)
{
m_qW = 1.0 - std::exp (-1.0 / m_ptc);
}
else if (m_qW == -1.0)
{
double rtt = 3.0 * (m_linkDelay.GetSeconds () + 1.0 / m_ptc);

if (rtt < 0.1)
{
rtt = 0.1;
}
m_qW = 1.0 - std::exp (-1.0 / (10 * rtt * m_ptc));
}
else if (m_qW == -2.0)
{
m_qW = 1.0 - std::exp (-10.0 / m_ptc);
}

if (m_bottom == 0)
{
Expand All @@ -565,7 +523,7 @@ RedQueueDisc::InitializeParams (void)
}

NS_LOG_DEBUG ("\tm_delay " << m_linkDelay.GetSeconds () << "; m_isWait "
<< m_isWait << "; m_qW " << m_qW << "; m_ptc " << m_ptc
<< m_isWait << "; m_qW " << m_qW << "; m_pktTimeConst " << m_pktTimeConst
<< "; m_minTh " << m_minTh << "; m_maxTh " << m_maxTh
<< "; m_isGentle " << m_isGentle << "; th_diff " << th_diff
<< "; lInterm " << m_lInterm << "; va " << m_vA << "; cur_max_p "
Expand Down Expand Up @@ -655,44 +613,8 @@ RedQueueDisc::DropEarly (Ptr<QueueDiscItem> item, uint32_t qSize)

double prob1 = CalculatePNew ();
m_vProb = ModifyP (prob1, item->GetSize ());

// Drop probability is computed, pick random number and act
if (m_cautious == 1)
{
/*
* Don't drop/mark if the instantaneous queue is much below the average.
* For experimental purposes only.
* pkts: the number of packets arriving in 50 ms
*/
double pkts = m_ptc * 0.05;
double fraction = std::pow ((1 - m_qW), pkts);

if ((double) qSize < fraction * m_qAvg)
{
// Queue could have been empty for 0.05 seconds
return 0;
}
}

double u = m_uv->GetValue ();

if (m_cautious == 2)
{
/*
* Decrease the drop probability if the instantaneous
* queue is much below the average.
* For experimental purposes only.
* pkts: the number of packets arriving in 50 ms
*/
double pkts = m_ptc * 0.05;
double fraction = std::pow ((1 - m_qW), pkts);
double ratio = qSize / (fraction * m_qAvg);

if (ratio < 1.0)
{
u *= 1.0 / ratio;
}
}

if (u <= m_vProb)
{
Expand Down Expand Up @@ -760,39 +682,27 @@ double
RedQueueDisc::ModifyP (double p, uint32_t size)
{
NS_LOG_FUNCTION (this << p << size);
double count1 = (double) m_count;
double count = (double) m_count;

if (GetMaxSize ().GetUnit () == QueueSizeUnit::BYTES)
{
count1 = (double) (m_countBytes / m_meanPktSize);
count = (double) (m_countBytes / m_meanPktSize);
}

if (m_isWait)
{
if (count1 * p < 1.0)
{
p = 0.0;
}
else if (count1 * p < 2.0)
{
p /= (2.0 - count1 * p);
}
else
{
p = 1.0;
}
}
else
{
if (count1 * p < 1.0)
{
p /= (1.0 - count1 * p);
}
else
{
p = 1.0;
}
}

if (count * p < 1.0)
{
p = 0.0;
}
else if (count * p < 2.0)
{
p /= (2.0 - count * p);
}
else
{
p = 1.0;
}


if ((GetMaxSize ().GetUnit () == QueueSizeUnit::BYTES) && (p < 1.0))
{
Expand All @@ -807,29 +717,42 @@ RedQueueDisc::ModifyP (double p, uint32_t size)
return p;
}

int RedQueueDisc::IsQueueEmpty()
{
if (GetInternalQueue (0)->IsEmpty ())
{
NS_LOG_LOGIC ("Queue empty");
m_idle = true;
m_idleTime = Simulator::Now ();

return 1;
}
return 0;
}

Ptr<QueueDiscItem>
RedQueueDisc::DoDequeue (void)
{
NS_LOG_FUNCTION (this);

if (GetInternalQueue (0)->IsEmpty ())

if (GetInternalQueue (0)->IsEmpty ())
{
NS_LOG_LOGIC ("Queue empty");
m_idle = 1;
m_idleTime = Simulator::Now ();

return 0;
}
else

else
{
m_idle = 0;
Ptr<QueueDiscItem> item = GetInternalQueue (0)->Dequeue ();

NS_LOG_LOGIC ("Popped " << item);

NS_LOG_LOGIC ("Number packets " << GetInternalQueue (0)->GetNPackets ());
NS_LOG_LOGIC ("Number bytes " << GetInternalQueue (0)->GetNBytes ());

//checking if queue becomes empty after dequeue
IsQueueEmpty();

return item;
}
}
Expand Down
3 changes: 1 addition & 2 deletions src/traffic-control/model/red-queue-disc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -298,7 +298,7 @@ class RedQueueDisc : public QueueDisc
uint32_t m_countBytes; //!< Number of bytes since last drop
uint32_t m_old; //!< 0 when average queue first exceeds threshold
uint32_t m_idle; //!< 0/1 idle status
double m_ptc; //!< packet time constant in packets/second
double m_pktTimeConst; //!< packet time constant in packets/second
double m_qAvg; //!< Average queue length
uint32_t m_count; //!< Number of packets since last random number generation
FengStatus m_fengStatus; //!< For use in Feng's Adaptive RED
Expand All @@ -308,7 +308,6 @@ class RedQueueDisc : public QueueDisc
* 2 experimental (see red-queue-disc.cc)
* 3 use Idle packet size in the ptc
*/
uint32_t m_cautious;
Time m_idleTime; //!< Start of current idle period

Ptr<UniformRandomVariable> m_uv; //!< rng stream
Expand Down