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improved congestion control

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orignal 2024-06-29 09:17:11 -04:00
parent ff8941af71
commit 199d149bed
2 changed files with 154 additions and 43 deletions
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174
libi2pd/Streaming.cpp
View File

@ -69,13 +69,14 @@ namespace stream
Stream::Stream (boost::asio::io_service& service, StreamingDestination& local,
std::shared_ptr<const i2p::data::LeaseSet> remote, int port): m_Service (service),
m_SendStreamID (0), m_SequenceNumber (0),
m_TunnelsChangeSequenceNumber (0), m_LastReceivedSequenceNumber (-1),
m_Status (eStreamStatusNew), m_IsAckSendScheduled (false), m_LocalDestination (local),
m_RemoteLeaseSet (remote), m_ReceiveTimer (m_Service), m_ResendTimer (m_Service),
m_TunnelsChangeSequenceNumber (0), m_LastReceivedSequenceNumber (-1), m_PreviousReceivedSequenceNumber (-1),
m_Status (eStreamStatusNew), m_IsAckSendScheduled (false), m_IsNAcked (false), m_IsWinDropped (true),
m_IsTimeOutResend (false), m_LocalDestination (local),
m_RemoteLeaseSet (remote), m_ReceiveTimer (m_Service), m_SendTimer (m_Service), m_ResendTimer (m_Service),
m_AckSendTimer (m_Service), m_NumSentBytes (0), m_NumReceivedBytes (0), m_Port (port),
m_RTT (INITIAL_RTT), m_WindowSize (MIN_WINDOW_SIZE), m_RTO (INITIAL_RTO),
m_AckDelay (local.GetOwner ()->GetStreamingAckDelay ()),
m_LastWindowSizeIncreaseTime (0), m_NumResendAttempts (0), m_MTU (STREAMING_MTU)
m_RTT (INITIAL_RTT), m_WindowSize (INITIAL_WINDOW_SIZE), m_RTO (INITIAL_RTO),
m_AckDelay (local.GetOwner ()->GetStreamingAckDelay ()), m_PrewRTTSample (INITIAL_RTT), m_PrewRTT (INITIAL_RTT), m_Jitter (0),
m_LastWindowSizeIncreaseTime (0), m_PacingTime (INITIAL_PACING_TIME), m_NumResendAttempts (0), m_MTU (STREAMING_MTU)
{
RAND_bytes ((uint8_t *)&m_RecvStreamID, 4);
m_RemoteIdentity = remote->GetIdentity ();
@ -83,12 +84,14 @@ namespace stream
Stream::Stream (boost::asio::io_service& service, StreamingDestination& local):
m_Service (service), m_SendStreamID (0), m_SequenceNumber (0),
m_TunnelsChangeSequenceNumber (0), m_LastReceivedSequenceNumber (-1),
m_Status (eStreamStatusNew), m_IsAckSendScheduled (false), m_LocalDestination (local),
m_ReceiveTimer (m_Service), m_ResendTimer (m_Service), m_AckSendTimer (m_Service),
m_TunnelsChangeSequenceNumber (0), m_LastReceivedSequenceNumber (-1), m_PreviousReceivedSequenceNumber (-1),
m_Status (eStreamStatusNew), m_IsAckSendScheduled (false), m_IsNAcked (false), m_IsWinDropped (true),
m_IsTimeOutResend (false), m_LocalDestination (local),
m_ReceiveTimer (m_Service), m_SendTimer (m_Service), m_ResendTimer (m_Service), m_AckSendTimer (m_Service),
m_NumSentBytes (0), m_NumReceivedBytes (0), m_Port (0), m_RTT (INITIAL_RTT),
m_WindowSize (MIN_WINDOW_SIZE), m_RTO (INITIAL_RTO), m_AckDelay (local.GetOwner ()->GetStreamingAckDelay ()),
m_LastWindowSizeIncreaseTime (0), m_NumResendAttempts (0), m_MTU (STREAMING_MTU)
m_WindowSize (INITIAL_WINDOW_SIZE), m_RTO (INITIAL_RTO), m_AckDelay (local.GetOwner ()->GetStreamingAckDelay ()),
m_PrewRTTSample (INITIAL_RTT), m_PrewRTT (INITIAL_RTT), m_Jitter (0),
m_LastWindowSizeIncreaseTime (0), m_PacingTime (INITIAL_PACING_TIME), m_NumResendAttempts (0), m_MTU (STREAMING_MTU)
{
RAND_bytes ((uint8_t *)&m_RecvStreamID, 4);
}
@ -203,6 +206,12 @@ namespace stream
{
// we have received duplicate
LogPrint (eLogWarning, "Streaming: Duplicate message ", receivedSeqn, " on sSID=", m_SendStreamID);
if (receivedSeqn <= m_PreviousReceivedSequenceNumber || receivedSeqn == m_LastReceivedSequenceNumber)
{
m_CurrentOutboundTunnel = m_LocalDestination.GetOwner ()->GetTunnelPool ()->GetNextOutboundTunnel (m_CurrentOutboundTunnel);
UpdateCurrentRemoteLease ();
}
m_PreviousReceivedSequenceNumber = receivedSeqn;
SendQuickAck (); // resend ack for previous message again
m_LocalDestination.DeletePacket (packet); // packet dropped
}
@ -410,6 +419,7 @@ namespace stream
}
int rttSample = INT_MAX;
bool firstRttSample = false;
m_IsNAcked = false;
int nackCount = packet->GetNACKCount ();
for (auto it = m_SentPackets.begin (); it != m_SentPackets.end ();)
{
@ -422,6 +432,7 @@ namespace stream
for (int i = 0; i < nackCount; i++)
if (seqn == packet->GetNACK (i))
{
m_IsNAcked = true;
nacked = true;
break;
}
@ -447,8 +458,8 @@ namespace stream
m_SentPackets.erase (it++);
m_LocalDestination.DeletePacket (sentPacket);
acknowledged = true;
if (m_WindowSize < WINDOW_SIZE)
m_WindowSize++; // slow start
if (m_WindowSize < MAX_WINDOW_SIZE)
m_WindowSize++;
}
else
break;
@ -456,30 +467,58 @@ namespace stream
if (rttSample != INT_MAX)
{
if (firstRttSample)
{
m_RTT = rttSample;
m_PrewRTTSample = rttSample;
}
else
m_RTT = RTT_EWMA_ALPHA * rttSample + (1.0 - RTT_EWMA_ALPHA) * m_RTT;
// calculate jitter
int jitter = 0;
if (rttSample > m_PrewRTTSample)
jitter = rttSample - m_PrewRTTSample;
else if (rttSample < m_PrewRTTSample)
jitter = m_PrewRTTSample - rttSample;
else
jitter = std::round (rttSample / 10); // 10%
m_Jitter = std::round (RTT_EWMA_ALPHA * m_Jitter + (1.0 - RTT_EWMA_ALPHA) * jitter);
m_PrewRTTSample = rttSample;
//
// delay-based CC
if ((m_RTT > m_PrewRTT) && !m_IsWinDropped) // Drop window if RTT grows too fast, late detection
{
m_WindowSize >>= 1; // /2
m_IsWinDropped = true; // don't drop window twice
}
if (m_WindowSize < MIN_WINDOW_SIZE) m_WindowSize = MIN_WINDOW_SIZE;
int pacTime = std::round (m_RTT*1000/m_WindowSize);
m_PacingTime = std::max (MIN_PACING_TIME, pacTime);
m_PrewRTT = m_RTT * 1.1 + m_Jitter;
//
bool wasInitial = m_RTO == INITIAL_RTO;
m_RTO = std::max (MIN_RTO, (int)(m_RTT * 1.5)); // TODO: implement it better
m_RTO = std::max (MIN_RTO, (int)(m_RTT * 1.3 + m_Jitter)); // TODO: implement it better
if (wasInitial)
ScheduleResend ();
}
if (acknowledged && m_WindowSize >= WINDOW_SIZE)
if (m_WindowSize > int(m_SentPackets.size ()))
m_IsWinDropped = false;
if (acknowledged || m_IsNAcked)
{
// linear growth
if (ts > m_LastWindowSizeIncreaseTime + m_RTT)
{
m_WindowSize++;
if (m_WindowSize > MAX_WINDOW_SIZE) m_WindowSize = MAX_WINDOW_SIZE;
m_LastWindowSizeIncreaseTime = ts;
}
ScheduleResend ();
}
if ((m_SendBuffer.IsEmpty () && m_SentPackets.size () > 0) // tail loss
|| int(m_SentPackets.size ()) > m_WindowSize) // or we drop window
m_IsNAcked = true;
if (firstRttSample && m_RoutingSession)
m_RoutingSession->SetSharedRoutingPath (
std::make_shared<i2p::garlic::GarlicRoutingPath> (
i2p::garlic::GarlicRoutingPath{m_CurrentOutboundTunnel, m_CurrentRemoteLease, (int)m_RTT, 0, 0}));
if (m_SentPackets.empty ())
{
m_ResendTimer.cancel ();
m_SendTimer.cancel ();
}
if (acknowledged)
{
m_NumResendAttempts = 0;
@ -557,9 +596,10 @@ namespace stream
void Stream::SendBuffer ()
{
ScheduleSend ();
int numMsgs = m_WindowSize - m_SentPackets.size ();
if (numMsgs <= 0) return; // window is full
else numMsgs = 1;
bool isNoAck = m_LastReceivedSequenceNumber < 0; // first packet
std::vector<Packet *> packets;
while ((m_Status == eStreamStatusNew) || (IsEstablished () && !m_SendBuffer.IsEmpty () && numMsgs > 0))
@ -873,6 +913,7 @@ namespace stream
m_IsAckSendScheduled = false;
m_AckSendTimer.cancel ();
}
if (!packet->sendTime) packet->sendTime = i2p::util::GetMillisecondsSinceEpoch ();
SendPackets (std::vector<Packet *> { packet });
bool isEmpty = m_SentPackets.empty ();
m_SentPackets.insert (packet);
@ -906,7 +947,7 @@ namespace stream
m_CurrentOutboundTunnel = routingPath->outboundTunnel;
m_CurrentRemoteLease = routingPath->remoteLease;
m_RTT = routingPath->rtt;
m_RTO = std::max (MIN_RTO, (int)(m_RTT * 1.5)); // TODO: implement it better
m_RTO = std::max (MIN_RTO, (int)(m_RTT * 1.3 + m_Jitter)); // TODO: implement it better
}
}
@ -935,7 +976,7 @@ namespace stream
if (freshTunnel)
{
m_RTO = INITIAL_RTO;
m_TunnelsChangeSequenceNumber = m_SequenceNumber; // should be determined more precisely
// m_TunnelsChangeSequenceNumber = m_SequenceNumber; // should be determined more precisely
}
std::vector<i2p::tunnel::TunnelMessageBlock> msgs;
@ -988,6 +1029,40 @@ namespace stream
SendQuickAck ();
}
void Stream::ScheduleSend ()
{
if (m_Status != eStreamStatusTerminated)
{
m_SendTimer.cancel ();
m_SendTimer.expires_from_now (boost::posix_time::microseconds(m_PacingTime));
m_SendTimer.async_wait (std::bind (&Stream::HandleSendTimer,
shared_from_this (), std::placeholders::_1));
}
}
void Stream::HandleSendTimer (const boost::system::error_code& ecode)
{
if (ecode != boost::asio::error::operation_aborted)
{
if (m_IsNAcked) // || m_WindowSize < int(m_SentPackets.size ())) // resend one packet
ResendPacket ();
// delay-based CC
else if (!m_IsWinDropped && int(m_SentPackets.size ()) == m_WindowSize) // we sending packets too fast, early detection
{
m_WindowSize >>= 1; // /2
m_IsWinDropped = true; // don't drop window twice
if (m_WindowSize < MIN_WINDOW_SIZE) m_WindowSize = MIN_WINDOW_SIZE;
int pacTime = std::round (m_RTT*1000/m_WindowSize);
m_PacingTime = std::max (MIN_PACING_TIME, pacTime);
}
//
else if (m_WindowSize > int(m_SentPackets.size ())) // send one packet
SendBuffer ();
else // pass
ScheduleSend ();
}
}
void Stream::ScheduleResend ()
{
if (m_Status != eStreamStatusTerminated)
@ -1005,6 +1080,16 @@ namespace stream
{
if (ecode != boost::asio::error::operation_aborted)
{
if (m_RTO > INITIAL_RTO) m_RTO = INITIAL_RTO;
m_SendTimer.cancel (); // if no ack's in RTO, disable fast retransmit
m_IsTimeOutResend = true;
m_IsNAcked = false;
ResendPacket (); // send one packet per RTO, waiting for ack
}
}
void Stream::ResendPacket ()
{
// check for resend attempts
if (m_NumResendAttempts >= MAX_NUM_RESEND_ATTEMPTS)
{
@ -1021,27 +1106,42 @@ namespace stream
{
if (ts >= it->sendTime + m_RTO)
{
it->resent = true;
if (ts < it->sendTime + m_RTO*2)
it->resent = true;
else
it->resent = false;
it->sendTime = ts;
packets.push_back (it);
if (packets.size () >= 1) break;
}
}
// select tunnels if necessary and send
if (packets.size () > 0)
{
m_NumResendAttempts++;
if (m_IsNAcked) m_NumResendAttempts = 1;
else if (m_IsTimeOutResend) m_NumResendAttempts++;
if (m_NumResendAttempts == 1 && m_RTO != INITIAL_RTO)
{
// congestion avoidance
m_RTO *= 2;
m_WindowSize -= (m_WindowSize + WINDOW_SIZE_DROP_FRACTION) / WINDOW_SIZE_DROP_FRACTION; // adjustment >= 1
if (m_WindowSize < MIN_WINDOW_SIZE) m_WindowSize = MIN_WINDOW_SIZE;
// loss-based CC
if (!m_IsWinDropped)
{
m_WindowSize >>= 1; // /2
m_IsWinDropped = true; // don't drop window twice
if (m_WindowSize < MIN_WINDOW_SIZE) m_WindowSize = MIN_WINDOW_SIZE;
int pacTime = std::round (m_RTT*1000/m_WindowSize);
m_PacingTime = std::max (MIN_PACING_TIME, pacTime);
}
//
}
else
else if (m_IsTimeOutResend)
{
m_TunnelsChangeSequenceNumber = m_SequenceNumber;
m_IsTimeOutResend = false;
m_RTO = INITIAL_RTO; // drop RTO to initial upon tunnels pair change
m_WindowSize = INITIAL_WINDOW_SIZE;
m_IsWinDropped = true;
int pacTime = std::round (m_RTT*1000/m_WindowSize);
m_PacingTime = std::max (MIN_PACING_TIME, pacTime);
if (m_RoutingSession) m_RoutingSession->SetSharedRoutingPath (nullptr);
if (m_NumResendAttempts & 1)
{
@ -1058,9 +1158,11 @@ namespace stream
}
}
SendPackets (packets);
if (m_IsNAcked) ScheduleSend ();
}
ScheduleResend ();
}
else
ScheduleSend ();
if (!m_IsNAcked) ScheduleResend ();
}
void Stream::ScheduleAck (int timeout)

23
libi2pd/Streaming.h
View File

@ -52,15 +52,17 @@ namespace stream
const size_t STREAMING_MTU_RATCHETS = 1812;
const size_t MAX_PACKET_SIZE = 4096;
const size_t COMPRESSION_THRESHOLD_SIZE = 66;
const int MAX_NUM_RESEND_ATTEMPTS = 9;
const int WINDOW_SIZE = 6; // in messages
const int MAX_NUM_RESEND_ATTEMPTS = 10;
const int MAX_STREAM_SPEED = 1730000000; // 1 - 1730000000 // in bytes/sec // no more than 1.73 Gbytes/s
const int MIN_PACING_TIME = 1000000 * STREAMING_MTU / MAX_STREAM_SPEED; // in microseconds
const int INITIAL_WINDOW_SIZE = 10;
const int MIN_WINDOW_SIZE = 1;
const int MAX_WINDOW_SIZE = 128;
const int WINDOW_SIZE_DROP_FRACTION = 10; // 1/10
const double RTT_EWMA_ALPHA = 0.125;
const double RTT_EWMA_ALPHA = 0.9;
const int MIN_RTO = 20; // in milliseconds
const int INITIAL_RTT = 8000; // in milliseconds
const int INITIAL_RTO = 9000; // in milliseconds
const int INITIAL_PACING_TIME = 1000 * INITIAL_RTT / INITIAL_WINDOW_SIZE; // in microseconds
const int MIN_SEND_ACK_TIMEOUT = 2; // in milliseconds
const int SYN_TIMEOUT = 200; // how long we wait for SYN after follow-on, in milliseconds
const size_t MAX_PENDING_INCOMING_BACKLOG = 128;
@ -231,8 +233,11 @@ namespace stream
template<typename Buffer, typename ReceiveHandler>
void HandleReceiveTimer (const boost::system::error_code& ecode, const Buffer& buffer, ReceiveHandler handler, int remainingTimeout);
void ScheduleSend ();
void HandleSendTimer (const boost::system::error_code& ecode);
void ScheduleResend ();
void HandleResendTimer (const boost::system::error_code& ecode);
void ResendPacket ();
void ScheduleAck (int timeout);
void HandleAckSendTimer (const boost::system::error_code& ecode);
@ -242,8 +247,12 @@ namespace stream
uint32_t m_SendStreamID, m_RecvStreamID, m_SequenceNumber;
uint32_t m_TunnelsChangeSequenceNumber;
int32_t m_LastReceivedSequenceNumber;
int32_t m_PreviousReceivedSequenceNumber;
StreamStatus m_Status;
bool m_IsAckSendScheduled;
bool m_IsNAcked;
bool m_IsWinDropped;
bool m_IsTimeOutResend;
StreamingDestination& m_LocalDestination;
std::shared_ptr<const i2p::data::IdentityEx> m_RemoteIdentity;
std::shared_ptr<const i2p::crypto::Verifier> m_TransientVerifier; // in case of offline key
@ -254,14 +263,14 @@ namespace stream
std::queue<Packet *> m_ReceiveQueue;
std::set<Packet *, PacketCmp> m_SavedPackets;
std::set<Packet *, PacketCmp> m_SentPackets;
boost::asio::deadline_timer m_ReceiveTimer, m_ResendTimer, m_AckSendTimer;
boost::asio::deadline_timer m_ReceiveTimer, m_SendTimer, m_ResendTimer, m_AckSendTimer;
size_t m_NumSentBytes, m_NumReceivedBytes;
uint16_t m_Port;
SendBufferQueue m_SendBuffer;
double m_RTT;
int m_WindowSize, m_RTO, m_AckDelay;
uint64_t m_LastWindowSizeIncreaseTime;
int m_WindowSize, m_RTO, m_AckDelay, m_PrewRTTSample, m_PrewRTT, m_Jitter;
uint64_t m_LastWindowSizeIncreaseTime, m_PacingTime;
int m_NumResendAttempts;
size_t m_MTU;
};