tcp-highspeed.cc

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/*
 * Copyright (c) 2014 Natale Patriciello, <natale.patriciello@gmail.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */
 
#include "tcp-highspeed.h"
 
#include "tcp-socket-state.h"
 
#include "ns3/log.h"
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("TcpHighSpeed");
NS_OBJECT_ENSURE_REGISTERED(TcpHighSpeed);
 
TypeId
TcpHighSpeed::GetTypeId()
{
    static TypeId tid = TypeId("ns3::TcpHighSpeed")
                            .SetParent<TcpNewReno>()
                            .AddConstructor<TcpHighSpeed>()
                            .SetGroupName("Internet");
    return tid;
}
 
TcpHighSpeed::TcpHighSpeed()
    : TcpNewReno(),
      m_ackCnt(0)
{
    NS_LOG_FUNCTION(this);
}
 
TcpHighSpeed::TcpHighSpeed(const TcpHighSpeed& sock)
    : TcpNewReno(sock),
      m_ackCnt(sock.m_ackCnt)
{
    NS_LOG_FUNCTION(this);
}
 
TcpHighSpeed::~TcpHighSpeed()
{
    NS_LOG_FUNCTION(this);
}
 
Ptr<TcpCongestionOps>
TcpHighSpeed::Fork()
{
    return CopyObject<TcpHighSpeed>(this);
}
 
/**
 * @brief Congestion avoidance of TcpHighSpeed
 *
 * As implementation choice, we increment cWnd only by MSS, when the right
 * number of ACK has been received. At this point, the important question is:
 * what is the "right number of ACK" ?
 *
 * As you can recall from RFC, Highspeed works this way:
 *
 *               w = w + a(w)/w
 *
 * Let's start when a(w) is 1 (so it is classical NewReno). The formula then is
 * the classical text-book version for NewReno:
 *
 *               w = w + 1 / w
 *
 * So, for each segment acked, we increase the window by the quantity 1/w. Or,
 * instead of adding the 1/w quantity for each segment acked, we can track the
 * number of segments acked (m_ackCnt) and increment by 1 MSS when m_ackCnt
 * reaches w.
 *
 * When a(w) > 1, it means that each segment acked has a different "weight".
 * For instance, when it is equal to 2, we need to increase the window by the
 * quantity 2/w. But, this means that one segment acked is equivalent (from
 * the point of view of incrementing cWnd) to two segments acked in NewReno
 * (1/w + 1/w). That a coefficient is, in other word, the weight of each segment
 * acked. More weight, less ACK are necessary to increment cWnd, which is
 * exactly the Highspeed principle.
 *
 * @param tcb internal congestion state
 * @param segmentsAcked count of segments acked
 */
void
TcpHighSpeed::CongestionAvoidance(Ptr<TcpSocketState> tcb, uint32_t segmentsAcked)
{
    NS_LOG_FUNCTION(this << tcb << segmentsAcked);
 
    uint32_t segCwnd = tcb->GetCwndInSegments();
    uint32_t oldCwnd = segCwnd;
 
    if (segmentsAcked > 0)
    {
        uint32_t coeffA = TableLookupA(segCwnd);
        m_ackCnt += segmentsAcked * coeffA;
    }
 
    while (m_ackCnt >= segCwnd)
    {
        m_ackCnt -= segCwnd;
        segCwnd += 1;
    }
 
    if (segCwnd != oldCwnd)
    {
        tcb->m_cWnd = segCwnd * tcb->m_segmentSize;
        NS_LOG_INFO("In CongAvoid, updated to cwnd " << tcb->m_cWnd << " ssthresh "
                                                     << tcb->m_ssThresh);
    }
}
 
std::string
TcpHighSpeed::GetName() const
{
    return "TcpHighSpeed";
}
 
/**
 * @brief Get slow start threshold following HighSpeed principles
 *
 * @param tcb internal congestion state
 * @param bytesInFlight Bytes in flight
 *
 * @return the slow start threshold value
 */
uint32_t
TcpHighSpeed::GetSsThresh(Ptr<const TcpSocketState> tcb, uint32_t bytesInFlight)
{
    NS_LOG_FUNCTION(this << tcb << bytesInFlight);
 
    uint32_t segCwnd = bytesInFlight / tcb->m_segmentSize;
 
    double b = 1.0 - TableLookupB(segCwnd);
    uint32_t ssThresh = static_cast<uint32_t>(std::max(2.0, segCwnd * b));
 
    NS_LOG_DEBUG("Calculated b(w) = " << b << " resulting (in segment) ssThresh=" << ssThresh);
 
    return ssThresh * tcb->m_segmentSize;
}
 
uint32_t
TcpHighSpeed::TableLookupA(uint32_t w)
{
    if (w <= 38)
    {
        return 1;
    }
    else if (w <= 118)
    {
        return 2;
    }
    else if (w <= 221)
    {
        return 3;
    }
    else if (w <= 347)
    {
        return 4;
    }
    else if (w <= 495)
    {
        return 5;
    }
    else if (w <= 663)
    {
        return 6;
    }
    else if (w <= 851)
    {
        return 7;
    }
    else if (w <= 1058)
    {
        return 8;
    }
    else if (w <= 1284)
    {
        return 9;
    }
    else if (w <= 1529)
    {
        return 10;
    }
    else if (w <= 1793)
    {
        return 11;
    }
    else if (w <= 2076)
    {
        return 12;
    }
    else if (w <= 2378)
    {
        return 13;
    }
    else if (w <= 2699)
    {
        return 14;
    }
    else if (w <= 3039)
    {
        return 15;
    }
    else if (w <= 3399)
    {
        return 16;
    }
    else if (w <= 3778)
    {
        return 17;
    }
    else if (w <= 4177)
    {
        return 18;
    }
    else if (w <= 4596)
    {
        return 19;
    }
    else if (w <= 5036)
    {
        return 20;
    }
    else if (w <= 5497)
    {
        return 21;
    }
    else if (w <= 5979)
    {
        return 22;
    }
    else if (w <= 6483)
    {
        return 23;
    }
    else if (w <= 7009)
    {
        return 24;
    }
    else if (w <= 7558)
    {
        return 25;
    }
    else if (w <= 8130)
    {
        return 26;
    }
    else if (w <= 8726)
    {
        return 27;
    }
    else if (w <= 9346)
    {
        return 28;
    }
    else if (w <= 9991)
    {
        return 29;
    }
    else if (w <= 10661)
    {
        return 30;
    }
    else if (w <= 11358)
    {
        return 31;
    }
    else if (w <= 12082)
    {
        return 32;
    }
    else if (w <= 12834)
    {
        return 33;
    }
    else if (w <= 13614)
    {
        return 34;
    }
    else if (w <= 14424)
    {
        return 35;
    }
    else if (w <= 15265)
    {
        return 36;
    }
    else if (w <= 16137)
    {
        return 37;
    }
    else if (w <= 17042)
    {
        return 38;
    }
    else if (w <= 17981)
    {
        return 39;
    }
    else if (w <= 18955)
    {
        return 40;
    }
    else if (w <= 19965)
    {
        return 41;
    }
    else if (w <= 21013)
    {
        return 42;
    }
    else if (w <= 22101)
    {
        return 43;
    }
    else if (w <= 23230)
    {
        return 44;
    }
    else if (w <= 24402)
    {
        return 45;
    }
    else if (w <= 25618)
    {
        return 46;
    }
    else if (w <= 26881)
    {
        return 47;
    }
    else if (w <= 28193)
    {
        return 48;
    }
    else if (w <= 29557)
    {
        return 49;
    }
    else if (w <= 30975)
    {
        return 50;
    }
    else if (w <= 32450)
    {
        return 51;
    }
    else if (w <= 33986)
    {
        return 52;
    }
    else if (w <= 35586)
    {
        return 53;
    }
    else if (w <= 37253)
    {
        return 54;
    }
    else if (w <= 38992)
    {
        return 55;
    }
    else if (w <= 40808)
    {
        return 56;
    }
    else if (w <= 42707)
    {
        return 57;
    }
    else if (w <= 44694)
    {
        return 58;
    }
    else if (w <= 46776)
    {
        return 59;
    }
    else if (w <= 48961)
    {
        return 60;
    }
    else if (w <= 51258)
    {
        return 61;
    }
    else if (w <= 53667)
    {
        return 62;
    }
    else if (w <= 56230)
    {
        return 63;
    }
    else if (w <= 58932)
    {
        return 64;
    }
    else if (w <= 61799)
    {
        return 65;
    }
    else if (w <= 64851)
    {
        return 66;
    }
    else if (w <= 68113)
    {
        return 67;
    }
    else if (w <= 71617)
    {
        return 68;
    }
    else if (w <= 75401)
    {
        return 69;
    }
    else if (w <= 79517)
    {
        return 70;
    }
    else if (w <= 84035)
    {
        return 71;
    }
    else if (w <= 89053)
    {
        return 72;
    }
    else if (w <= 94717)
    {
        return 73;
    }
 
    return 73;
}
 
double
TcpHighSpeed::TableLookupB(uint32_t w)
{
    // NOLINTBEGIN(bugprone-branch-clone)
    if (w <= 38)
    {
        return 0.50;
    }
    else if (w <= 118)
    {
        return 0.44;
    }
    else if (w <= 221)
    {
        return 0.41;
    }
    else if (w <= 347)
    {
        return 0.38;
    }
    else if (w <= 495)
    {
        return 0.37;
    }
    else if (w <= 663)
    {
        return 0.35;
    }
    else if (w <= 851)
    {
        return 0.34;
    }
    else if (w <= 1058)
    {
        return 0.33;
    }
    else if (w <= 1284)
    {
        return 0.32;
    }
    else if (w <= 1529)
    {
        return 0.31;
    }
    else if (w <= 1793)
    {
        return 0.30;
    }
    else if (w <= 2076)
    {
        return 0.29;
    }
    else if (w <= 2378)
    {
        return 0.28;
    }
    else if (w <= 2699)
    {
        return 0.28;
    }
    else if (w <= 3039)
    {
        return 0.27;
    }
    else if (w <= 3399)
    {
        return 0.27;
    }
    else if (w <= 3778)
    {
        return 0.26;
    }
    else if (w <= 4177)
    {
        return 0.26;
    }
    else if (w <= 4596)
    {
        return 0.25;
    }
    else if (w <= 5036)
    {
        return 0.25;
    }
    else if (w <= 5497)
    {
        return 0.24;
    }
    else if (w <= 5979)
    {
        return 0.24;
    }
    else if (w <= 6483)
    {
        return 0.23;
    }
    else if (w <= 7009)
    {
        return 0.23;
    }
    else if (w <= 7558)
    {
        return 0.22;
    }
    else if (w <= 8130)
    {
        return 0.22;
    }
    else if (w <= 8726)
    {
        return 0.22;
    }
    else if (w <= 9346)
    {
        return 0.21;
    }
    else if (w <= 9991)
    {
        return 0.21;
    }
    else if (w <= 10661)
    {
        return 0.21;
    }
    else if (w <= 11358)
    {
        return 0.20;
    }
    else if (w <= 12082)
    {
        return 0.20;
    }
    else if (w <= 12834)
    {
        return 0.20;
    }
    else if (w <= 13614)
    {
        return 0.19;
    }
    else if (w <= 14424)
    {
        return 0.19;
    }
    else if (w <= 15265)
    {
        return 0.19;
    }
    else if (w <= 16137)
    {
        return 0.19;
    }
    else if (w <= 17042)
    {
        return 0.18;
    }
    else if (w <= 17981)
    {
        return 0.18;
    }
    else if (w <= 18955)
    {
        return 0.18;
    }
    else if (w <= 19965)
    {
        return 0.17;
    }
    else if (w <= 21013)
    {
        return 0.17;
    }
    else if (w <= 22101)
    {
        return 0.17;
    }
    else if (w <= 23230)
    {
        return 0.17;
    }
    else if (w <= 24402)
    {
        return 0.16;
    }
    else if (w <= 25618)
    {
        return 0.16;
    }
    else if (w <= 26881)
    {
        return 0.16;
    }
    else if (w <= 28193)
    {
        return 0.16;
    }
    else if (w <= 29557)
    {
        return 0.15;
    }
    else if (w <= 30975)
    {
        return 0.15;
    }
    else if (w <= 32450)
    {
        return 0.15;
    }
    else if (w <= 33986)
    {
        return 0.15;
    }
    else if (w <= 35586)
    {
        return 0.14;
    }
    else if (w <= 37253)
    {
        return 0.14;
    }
    else if (w <= 38992)
    {
        return 0.14;
    }
    else if (w <= 40808)
    {
        return 0.14;
    }
    else if (w <= 42707)
    {
        return 0.13;
    }
    else if (w <= 44694)
    {
        return 0.13;
    }
    else if (w <= 46776)
    {
        return 0.13;
    }
    else if (w <= 48961)
    {
        return 0.13;
    }
    else if (w <= 51258)
    {
        return 0.13;
    }
    else if (w <= 53667)
    {
        return 0.12;
    }
    else if (w <= 56230)
    {
        return 0.12;
    }
    else if (w <= 58932)
    {
        return 0.12;
    }
    else if (w <= 61799)
    {
        return 0.12;
    }
    else if (w <= 64851)
    {
        return 0.11;
    }
    else if (w <= 68113)
    {
        return 0.11;
    }
    else if (w <= 71617)
    {
        return 0.11;
    }
    else if (w <= 75401)
    {
        return 0.10;
    }
    else if (w <= 79517)
    {
        return 0.10;
    }
    else if (w <= 84035)
    {
        return 0.10;
    }
    else if (w <= 89053)
    {
        return 0.10;
    }
    else if (w <= 94717)
    {
        return 0.09;
    }
    else
    {
        return 0.09;
    }
    // NOLINTEND(bugprone-branch-clone)
}
 
} // namespace ns3