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Integrated ACK state machine in ReceivedAck method

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This commit is contained in:
Natale Patriciello
2015-10-16 10:39:02 -07:00
parent 2c0cfe1201
commit d7b98b2396
3 changed files with 91 additions and 48 deletions
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2
src/internet/model/tcp-newreno.cc
View File

@@ -78,7 +78,7 @@ TcpNewReno::NewAck (const SequenceNumber32& seq)
" ssthresh " << m_ssThresh);
// No cWnd management while recovering
if (m_inFastRec && seq < m_recover)
if (m_ackState == RECOVERY && seq < m_recover)
{
TcpSocketBase::NewAck (seq);
return;

121
src/internet/model/tcp-socket-base.cc
View File

@@ -205,7 +205,6 @@ TcpSocketBase::TcpSocketBase (void)
m_timestampToEcho (0),
m_ackState (OPEN),
m_retxThresh (3),
m_inFastRec (false),
m_limitedTx (false)
{
@@ -256,7 +255,6 @@ TcpSocketBase::TcpSocketBase (const TcpSocketBase& sock)
m_timestampToEcho (sock.m_timestampToEcho),
m_ackState (sock.m_ackState),
m_retxThresh (sock.m_retxThresh),
m_inFastRec (false),
m_limitedTx (sock.m_limitedTx)
{
@@ -689,7 +687,7 @@ TcpSocketBase::Send (Ptr<Packet> p, uint32_t flags)
{ // Try to send the data out
if (!m_sendPendingDataEvent.IsRunning ())
{
m_sendPendingDataEvent = Simulator::Schedule ( TimeStep (1), &TcpSocketBase::SendPendingData, this, m_connected);
m_sendPendingDataEvent = Simulator::Schedule (TimeStep (1), &TcpSocketBase::SendPendingData, this, m_connected);
}
}
return p->GetSize ();
@@ -1205,17 +1203,34 @@ TcpSocketBase::ReceivedAck (Ptr<Packet> packet, const TcpHeader& tcpHeader)
NS_ASSERT (0 != (tcpHeader.GetFlags () & TcpHeader::ACK));
if (tcpHeader.GetAckNumber () == m_txBuffer->HeadSequence ())
{ // Case 2: Potentially a duplicated ACK
if (tcpHeader.GetAckNumber () < m_nextTxSequence && packet->GetSize() == 0)
{
NS_LOG_LOGIC ("Dupack of " << tcpHeader.GetAckNumber ());
++m_dupAckCount;
if (tcpHeader.GetAckNumber () == m_txBuffer->HeadSequence () &&
tcpHeader.GetAckNumber () < m_nextTxSequence &&
packet->GetSize () == 0)
{
// There is a DupAck
++m_dupAckCount;
if (m_dupAckCount == m_retxThresh && !m_inFastRec)
{ // triple duplicate ack triggers fast retransmit (RFC2582 sec.3 bullet #1)
if (m_ackState == OPEN)
{
// From Open we go Disorder
NS_ASSERT (m_dupAckCount == 1);
m_ackState = DISORDER;
NS_LOG_LOGIC ("Dupack. Open -> Disorder");
}
else if (m_ackState == DISORDER)
{
if (m_dupAckCount < m_retxThresh && m_limitedTx)
{
// RFC3042 Limited transmit: Send a new packet for each duplicated ACK before fast retransmit
NS_LOG_INFO ("Limited transmit");
uint32_t sz = SendDataPacket (m_nextTxSequence, m_segmentSize, true);
m_nextTxSequence += sz;
}
else if (m_dupAckCount == m_retxThresh)
{
// triple duplicate ack triggers fast retransmit (RFC2582 sec.3 bullet #1)
m_recover = m_highTxMark;
m_inFastRec = true;
m_ackState = RECOVERY;
m_ssThresh = GetSsThresh ();
m_cWnd = m_ssThresh + m_dupAckCount * m_segmentSize;
@@ -1227,49 +1242,64 @@ TcpSocketBase::ReceivedAck (Ptr<Packet> packet, const TcpHeader& tcpHeader)
NS_LOG_DEBUG ("DISORDER -> RECOVERY");
}
else if (m_inFastRec)
{ // Increase cwnd for every additional dupack (RFC2582, sec.3 bullet #3)
m_cWnd += m_segmentSize;
NS_LOG_INFO ("Dupack in fast recovery mode. Increase cwnd to " << m_cWnd);
if (!m_sendPendingDataEvent.IsRunning ())
{
SendPendingData (m_connected);
}
}
else if (!m_inFastRec && m_limitedTx && m_txBuffer->SizeFromSequence (m_nextTxSequence) > 0)
{ // RFC3042 Limited transmit: Send a new packet for each duplicated ACK before fast retransmit
NS_LOG_INFO ("Limited transmit");
uint32_t sz = SendDataPacket (m_nextTxSequence, m_segmentSize, true);
m_nextTxSequence += sz; // Advance next tx sequence
else
{
NS_FATAL_ERROR ("m_dupAckCount > m_retxThresh and we still are in DISORDER state");
}
}
// otherwise, the ACK is precisely equal to the nextTxSequence
NS_ASSERT (tcpHeader.GetAckNumber () <= m_nextTxSequence);
else if (m_ackState == RECOVERY)
{ // Increase cwnd for every additional dupack (RFC2582, sec.3 bullet #3)
m_cWnd += m_segmentSize;
NS_LOG_INFO ("Dupack in fast recovery mode. Increase cwnd to " << m_cWnd);
if (!m_sendPendingDataEvent.IsRunning ())
{
m_sendPendingDataEvent = Simulator::Schedule (TimeStep (1), &TcpSocketBase::SendPendingData, this, m_connected);
}
}
}
else if (tcpHeader.GetAckNumber () == m_txBuffer->HeadSequence () &&
tcpHeader.GetAckNumber () == m_nextTxSequence)
{
// Dupack, but the ACK is precisely equal to the nextTxSequence
}
else if (tcpHeader.GetAckNumber () > m_txBuffer->HeadSequence ())
{ // Case 3: New ACK, reset m_dupAckCount and update m_txBuffer
NS_LOG_LOGIC ("New ack of " << tcpHeader.GetAckNumber ());
// Check for exit condition of fast recovery
if (m_inFastRec && tcpHeader.GetAckNumber () < m_recover)
{ // Partial ACK, partial window deflation (RFC2582 sec.3 bullet #5 paragraph 3)
m_cWnd += m_segmentSize - (tcpHeader.GetAckNumber () - m_txBuffer->HeadSequence ());
NS_LOG_INFO ("Partial ACK for seq " << tcpHeader.GetAckNumber () << " in fast recovery: cwnd set to " << m_cWnd);
m_txBuffer->DiscardUpTo(tcpHeader.GetAckNumber ()); //Bug 1850: retransmit before newack
DoRetransmit (); // Assume the next seq is lost. Retransmit lost packet
TcpSocketBase::NewAck (tcpHeader.GetAckNumber ()); // update m_nextTxSequence and send new data if allowed by window
return;
if (m_ackState == DISORDER)
{
// The network reorder packets. Linux changes the counting lost
// packet algorithm from FACK to NewReno. We simply go back in Open.
m_ackState = OPEN;
NS_LOG_LOGIC ("New Ack. Disorder -> Open");
}
else if (m_inFastRec && tcpHeader.GetAckNumber () >= m_recover)
{ // Full ACK (RFC2582 sec.3 bullet #5 paragraph 2, option 1)
m_cWnd = std::min (m_ssThresh.Get (), BytesInFlight () + m_segmentSize);
m_inFastRec = false;
NS_LOG_INFO ("Received full ACK for seq " << tcpHeader.GetAckNumber () <<". Leaving fast recovery with cwnd set to " << m_cWnd);
else if (m_ackState == RECOVERY)
{
if (tcpHeader.GetAckNumber () < m_recover)
{ // Partial ACK, partial window deflation (RFC2582 sec.3 bullet #5 paragraph 3)
m_cWnd += m_segmentSize - (tcpHeader.GetAckNumber () - m_txBuffer->HeadSequence ());
NS_LOG_INFO ("Partial ACK for seq " << tcpHeader.GetAckNumber () << " in fast recovery: cwnd set to " << m_cWnd);
m_txBuffer->DiscardUpTo(tcpHeader.GetAckNumber ()); //Bug 1850: retransmit before newack
DoRetransmit (); // Assume the next seq is lost. Retransmit lost packet
}
else if (tcpHeader.GetAckNumber () >= m_recover)
{// Full ACK (RFC2582 sec.3 bullet #5 paragraph 2, option 1)
m_cWnd = std::min (m_ssThresh.Get (), BytesInFlight () + m_segmentSize);
m_ackState = OPEN;
NS_LOG_INFO ("Received full ACK for seq " << tcpHeader.GetAckNumber () <<". Leaving fast recovery with cwnd set to " << m_cWnd);
}
}
else if (m_ackState == LOSS)
{
// Go back in OPEN state
m_ackState = OPEN;
NS_LOG_LOGIC ("New Ack. Loss -> Open");
}
NewAck (tcpHeader.GetAckNumber ());
m_dupAckCount = 0;
}
// If there is any data piggybacked, store it into m_rxBuffer
if (packet->GetSize () > 0)
{
@@ -2372,7 +2402,7 @@ TcpSocketBase::NewAck (SequenceNumber32 const& ack)
// Try to send more data
if (!m_sendPendingDataEvent.IsRunning ())
{
m_sendPendingDataEvent = Simulator::Schedule ( TimeStep (1), &TcpSocketBase::SendPendingData, this, m_connected);
m_sendPendingDataEvent = Simulator::Schedule (TimeStep (1), &TcpSocketBase::SendPendingData, this, m_connected);
}
}
@@ -2463,8 +2493,6 @@ TcpSocketBase::PersistTimeout ()
void
TcpSocketBase::Retransmit ()
{
m_inFastRec = false;
// If erroneous timeout in closed/timed-wait state, just return
if (m_state == CLOSED || m_state == TIME_WAIT) return;
// If all data are received (non-closing socket and nothing to send), just return
@@ -2473,10 +2501,11 @@ TcpSocketBase::Retransmit ()
// According to RFC2581 sec.3.1, upon RTO, ssthresh is set to half of flight
// size and cwnd is set to 1*MSS, then the lost packet is retransmitted and
// TCP back to slow start
m_ssThresh = GetSsThresh ();
m_cWnd = m_segmentSize;
m_nextTxSequence = m_txBuffer->HeadSequence (); // Restart from highest Ack
m_dupAckCount = 0;
m_ackState = LOSS;
m_ssThresh = GetSsThresh ();
NS_LOG_INFO ("RTO. Reset cwnd to " << m_cWnd <<
", ssthresh to " << m_ssThresh << ", restart from seqnum " << m_nextTxSequence);
DoRetransmit (); // Retransmit the packet

16
src/internet/model/tcp-socket-base.h
View File

@@ -88,6 +88,21 @@ typedef std::deque<RttHistory> RttHistory_t;
* this class is modified from the original NS-3 TCP socket implementation
* (TcpSocketImpl) by Raj Bhattacharjea <raj.b@gatech.edu> of Georgia Tech.
*
* Ack state machine
* ---------------------------
*
* The socket maintains two state machines; the TCP one, and another called
* "Ack state machine", which keeps track of the phase we are in. Currently,
* ns-3 manages the states:
*
* - OPEN
* - DISORDER
* - RECOVERY
* - LOSS
*
* Another one (CWR) is present but not used. For more information, see
* the TcpAckState_t documentation.
*
*
* Fast retransmit
* ---------------------------
@@ -841,7 +856,6 @@ protected:
// Fast Retransmit and Recovery
SequenceNumber32 m_recover; //!< Previous highest Tx seqnum for fast recovery
uint32_t m_retxThresh; //!< Fast Retransmit threshold
bool m_inFastRec; //!< currently in fast recovery
bool m_limitedTx; //!< perform limited transmit
};