text: 
  /*
   * asim.h
   * Copyright (C) 2000 by the University of Southern California
   * $Id: asim.h,v 1.3 2005/08/25 18:58:01 johnh Exp $
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program 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 General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License along
   * with this program; if not, write to the Free Software Foundation, Inc.,
   * 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
   *
   *
   * The copyright of this module includes the following
   * linking-with-specific-other-licenses addition:
   *
   * In addition, as a special exception, the copyright holders of
   * this module give you permission to combine (via static or
   * dynamic linking) this module with free software programs or
   * libraries that are released under the GNU LGPL and with code
   * included in the standard release of ns-2 under the Apache 2.0
   * license or under otherwise-compatible licenses with advertising
   * requirements (or modified versions of such code, with unchanged
   * license).  You may copy and distribute such a system following the
   * terms of the GNU GPL for this module and the licenses of the
   * other code concerned, provided that you include the source code of
   * that other code when and as the GNU GPL requires distribution of
   * source code.
   *
   * Note that people who make modified versions of this module
   * are not obligated to grant this special exception for their
   * modified versions; it is their choice whether to do so.  The GNU
   * General Public License gives permission to release a modified
   * version without this exception; this exception also makes it
   * possible to release a modified version which carries forward this
   * exception.
   *
   */
  
  // author: Debojyoti Dutta
  
  
  #ifndef _RED_ROUTER_H_
  #define _RED_ROUTER_H_
  
  #include <assert.h>
  #include <stdio.h>
  #include <math.h>
  
  
  class RedRouter {
    double MinTh, MaxTh, MaxP;
    double Lambda_L;
    double Lambda_H;
  
    void Populate();
   public:
    RedRouter(int mTh, int MTh, double MP) {
      MinTh = mTh;
      MaxTh = MTh;
      MaxP = MP; 
      Populate();
    }
    double ComputeProbability(double Lambda, double &Delay);
    short Identical(int mTh, int MTh, double MP) {
      return (mTh == MinTh &&
  	    MTh == MaxTh &&
  	    MP  == MaxP);
    }
  };
  
  void RedRouter::Populate() {
    // rho = Lambda_L: p = 0 => rho/(1-rho) = MinTh
    Lambda_L = ((double)MinTh)/((double)(1+MinTh));
  
    // rho = Lambda_H: p = Max_p => rho(1-Max_p)/(1-rho(1-Max_p)) = MaxTh;
    if (MaxP < 1)
      Lambda_H = ((double)MaxTh)/((double)(1+MaxTh))/(1-MaxP);
  }
  
  
  double RedRouter::ComputeProbability(double Lambda, double &delay) {
    double p;
    
    if (Lambda <= Lambda_L) {
      delay = Lambda/(1-Lambda);
      return 0;
    }
  
    if (MaxP < 1 && Lambda > Lambda_H) {
      delay = MaxTh;
      p = (Lambda - Lambda_H*(1 - MaxP))/Lambda;
      return p;
    }
  
    // Solve the quadratic a.p^2 + b.p + c = 0
    double a, b, c;
    a = Lambda * (MaxTh - MinTh)/(MaxP);
    b = (MaxTh - MinTh)*(1-Lambda)/MaxP + MinTh * Lambda + Lambda;
    c = MinTh*(1-Lambda)-Lambda;
  
    p = (-b + sqrt(b*b - 4 * a * c))/(2 * a);
    delay = Lambda*(1-p)/(1-(Lambda*(1-p)));
    return p;
  }
  
  
  #endif
  
  
  
  
  
  
  