/// <summary>
/// process ACK event (see spec. p 12)
/// </summary>
/// <param name="isTriggeredByTimer"></param>
protected void processACKEvent(bool isTriggeredByTimer)
{
try
{
//(1).Find the sequence number *prior to which* all the packets have been received
long ackNumber;
ReceiverLossListEntry entry = receiverLossList.getFirstEntry();
if (entry == null)
{
ackNumber = largestReceivedSeqNumber + 1;
}
else
{
ackNumber = entry.getSequenceNumber();
}
//(2).a) if ackNumber equals to the largest sequence number ever acknowledged by ACK2
if (ackNumber == largestAcknowledgedAckNumber)
{
//do not send this ACK
return;
}
else if (ackNumber == lastAckNumber)
{
//or it is equals to the ackNumber in the last ACK
//and the time interval between these two ACK packets
//is less than 2 RTTs,do not send(stop)
long timeOfLastSentAck = ackHistoryWindow.getTime(lastAckNumber);
if (Util.getCurrentTime() - timeOfLastSentAck < 2 * roundTripTime)
{
return;
}
}
long ackSeqNumber;
//if this ACK is not triggered by ACK timers,send out a light Ack and stop.
if (!isTriggeredByTimer)
{
ackSeqNumber = sendLightAcknowledgment(ackNumber);
return;
}
else
{
//pack the packet speed and link capacity into the ACK packet and send it out.
//(7).records the ACK number,ackseqNumber and the departure time of
//this Ack in the ACK History Window
ackSeqNumber = sendAcknowledgment(ackNumber);
}
AckHistoryEntry sentAckNumber = new AckHistoryEntry(ackSeqNumber, ackNumber, Util.getCurrentTime());
ackHistoryWindow.add(sentAckNumber);
//store ack number for next iteration
lastAckNumber = ackNumber;
}
catch (Exception exc)
{
Log.Write(this.ToString(), exc);
}
}
/**
* write a NAK triggered by a received sequence number that is larger than
* the largestReceivedSeqNumber + 1
* @param currentSequenceNumber - the currently received sequence number
* @throws IOException
*/
protected void SendNAK(long currentSequenceNumber)
{
NegativeAcknowledgement nAckPacket = new NegativeAcknowledgement();
nAckPacket.AddLossInfo(largestReceivedSeqNumber + 1, currentSequenceNumber);
nAckPacket.SetSession(session);
nAckPacket.DestinationID = session.Destination.SocketID;
//put all the sequence numbers between (but excluding) these two values into the
//receiver loss list
for (long i = largestReceivedSeqNumber + 1; i < currentSequenceNumber; i++)
{
ReceiverLossListEntry detectedLossSeqNumber = new ReceiverLossListEntry(i);
receiverLossList.Insert(detectedLossSeqNumber);
}
endpoint.DoSend(nAckPacket);
//logger.info("NAK for "+currentSequenceNumber);
statistics.incNumberOfNAKSent();
}
/**
* write a NAK triggered by a received sequence number that is larger than
* the largestReceivedSeqNumber + 1
* @param currentSequenceNumber - the currently received sequence number
* @throws IOException
*/
protected void sendNAK(long currentSequenceNumber)
{
try
{
NegativeAcknowledgement nAckPacket = new NegativeAcknowledgement();
nAckPacket.addLossInfo(largestReceivedSeqNumber + 1, currentSequenceNumber);
nAckPacket.setSession(session);
nAckPacket.setDestinationID(session.getDestination().getSocketID());
//put all the sequence numbers between (but excluding) these two values into the
//receiver loss list
for (long i = largestReceivedSeqNumber + 1; i < currentSequenceNumber; i++)
{
ReceiverLossListEntry detectedLossSeqNumber = new ReceiverLossListEntry(i);
receiverLossList.insert(detectedLossSeqNumber);
}
endpoint.doSend(nAckPacket);
//logger.info("NAK for "+currentSequenceNumber);
statistics.incNumberOfNAKSent();
}
catch (Exception exc)
{
Log.Write(this.ToString(), exc);
}
}
