public override void Shift()
{
WindowList.Sort();
int i;
for (i = 0; (i < WindowList.Count) && (WindowList[i].SequenceNumber == _windowBegin); i++)
{
_windowBegin = WindowList[i].RequiredAck;
OutputList.Add(WindowList[i]);
}
for (int k = 0; k < i; k++)
{
WindowList.RemoveAt(0);
}
}