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TahoeCongAvoid.cpp

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/*******************************************************************************
 * This file is part of openWNS (open Wireless Network Simulator)
 * _____________________________________________________________________________
 *
 * Copyright (C) 2004-2007
 * Chair of Communication Networks (ComNets)
 * Kopernikusstr. 16, D-52074 Aachen, Germany
 * phone: ++49-241-80-27910,
 * fax: ++49-241-80-22242
 * email: info@openwns.org
 * www: http://www.openwns.org
 * _____________________________________________________________________________
 *
 * openWNS is free software; you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License version 2 as published by the
 * Free Software Foundation;
 *
 * openWNS is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 ******************************************************************************/

#include <TCP/TahoeCongAvoid.hpp>


using namespace tcp;

STATIC_FACTORY_REGISTER_WITH_CREATOR(
    TahoeCongAvoid,
    CongestionAvoidanceStrategy,
    "tcp.TahoeCongAvoid",
    wns::PyConfigViewCreator
    );


TahoeCongAvoid::TahoeCongAvoid(const wns::pyconfig::View& _pyco):
    pyco(_pyco),
    cwnd(pyco.get<unsigned long int>("congestionWindow")),
    cwnd_cnt(pyco.get<unsigned long int>("congestionWindowCounter")),
    logger(pyco.get("logger")),
    timeout(pyco.get<simTimeType>("retransmissionTimeout")),
    ndup(pyco.get<int>("numberDupACKs")),
    countDuplicateACKs()
{
    countDuplicateACKs.clear();
}

TahoeCongAvoid::~TahoeCongAvoid()
{
    countDuplicateACKs.clear();
}

void
TahoeCongAvoid::onSegmentLoss(segmentLoss reason, unsigned long int _ackNR)
{
    MESSAGE_SINGLE(NORMAL, logger, "onSegmentLoss called. Reason: " << printReason(reason));

    switch(reason)
    {
    case(TIMEOUT):
        countDuplicateACKs.clear();
        setWindowSize(1);

        break;

    case(DUPLICATE_ACK):
        if(!countDuplicateACKs.knows(_ackNR))
        {
            // increase if ndup duplicate acks occure
            // _in a row_
            countDuplicateACKs.clear();
            // 1st dup ack is 2nd ack of same nr in a row
            countDuplicateACKs.insert(_ackNR, 2);
        }
        else
        {
            int tmp = countDuplicateACKs.find(_ackNR);
            if(tmp < ndup)
            {
                tmp++;
                countDuplicateACKs.update(_ackNR, tmp);
            }
            else
            {
                unsigned long int curr_cwnd = getWindowSize();
                setWindowSize(curr_cwnd/2);
            }
        }

        break;

    default:
        break;
    }
}


void
TahoeCongAvoid::onRTTSample()
{
}

unsigned long int
TahoeCongAvoid::getWindowSize()
{
    return cwnd;
}

simTimeType
TahoeCongAvoid::getRetransmissionTimeout()
{
    MESSAGE_SINGLE(NORMAL, logger, "Retransmission timeout: " << timeout);
    return this->timeout;
}

void
TahoeCongAvoid::onSegmentAcknowledged()
{
    countDuplicateACKs.clear();

    if (cwnd_cnt >= cwnd)
    {
        cwnd++;
        cwnd_cnt = 0;
    }
    else
    {
        cwnd_cnt++;
    }
    MESSAGE_SINGLE(NORMAL, logger, "Segment acknowledged. Window size: " << cwnd);
}

void
TahoeCongAvoid::setWindowSize(unsigned long int new_cwnd)
{
    MESSAGE_SINGLE(NORMAL, logger, "Setting window size: " << new_cwnd << "(old value: " << cwnd << ")");
    cwnd = new_cwnd;
}


std::string
TahoeCongAvoid::printReason(segmentLoss reason)
{
    switch(reason)
    {
    case TIMEOUT:
        return "TIMEOUT";
        break;
    case DUPLICATE_ACK:
        return "DUPLICATE_ACK";
        break;
    default:
        assure(false, "Unknown segment loss!");
        return "";
        break;
    }
}


bool
TahoeCongAvoid::duplicateACKThresholdReached(unsigned long int _ackNR)
{
    if(countDuplicateACKs.knows(_ackNR))
        return countDuplicateACKs.find(_ackNR) == ndup;
    else
        return false;
}


void
TahoeCongAvoid::clearDuplicateACKCounter()
{
    countDuplicateACKs.clear();
}

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