/* ds_tm_wred.asl - buffer management for DiffServ example		*/

/*
 *  Discrete Weighted RED for tri-color scheme
 */
#include "tmNp5.h"

#define CLR_GREEN  0b00
#define CLR_YELLOW 0b01
#define CLR_RED    0b10

/* Queue size limits for different colors */

unsigned qthresh_red_min        param_block_in_extended[ 0:1 ];
unsigned qthresh_red_max        param_block_in_extended[ 2:3 ];
unsigned qthresh_yellow_min     param_block_inout_extended[ 0:1 ];
unsigned qthresh_yellow_max     param_block_inout_extended[ 2:3 ];
unsigned qthresh_green_min      param_block_inout_extended[ 4:5 ];
unsigned qthresh_green_max      param_block_inout_extended[ 6:7 ];

/* average queue size */
unsigned Qaverage               param_block_inout_extended[ 8:9 ];

/* Queue steps (4 steps per interval) */
unsigned qstep_red     param_block_inout_extended[ 10:11 ];
unsigned qstep_yellow  param_block_inout_extended[ 12:13 ];
unsigned qstep_green   param_block_inout_extended[ 14:15 ];


/* color of the PDU (passed by FPL) */
unsigned color parameters_tm[1];

/* drop probability for current PDU */
unsigned(1) drop_pr;

/* 
 * weighted running average for the queue size 
 * as if current PDU is not dropped            
 */
unsigned(2) q_average;

/* temporaries for min and max queue sizes */
unsigned(2) qthresh_min;
unsigned(2) qthresh_max;

/* step to increment queue size threshold */
unsigned(2) q_step;

script tm_wred {

  /* 
   * compute average queue size as if the PDU is not dropped
   * Qaverage = Qaverage + 1/8*(Qcurrent-Qaverage)
   */
   q_average = Qaverage + ((blocks_in_Q + pdu_blocks)>>3) - (Qaverage>>3);

  /* Set thresholds according to color of current PDU */

  if (color == CLR_GREEN) {
        qthresh_min = qthresh_green_min;
        qthresh_max = qthresh_green_max;
        q_step = qstep_green;
   } else {
        if (color ==  CLR_YELLOW) {
              qthresh_min = qthresh_yellow_min;
              qthresh_max = qthresh_yellow_max;
              q_step = qstep_yellow;
        } else {
              qthresh_min = qthresh_red_min;
              qthresh_max = qthresh_red_max;
              q_step = qstep_red;
        }
   }

   /* 
    * Calculate drop probability, depending on the
    * threshold interval for the current packet
    */

   if ((q_average > qthresh_max) ||
       (sch_mem > sch_thresh) ||
       (port_mem > port_thresh) ||
       (used_mem > glob_thresh1)) {
          drop_pr = 0xff;  /* (100% drop probability) */
   } else {
          drop_pr = 0x00;  /* (0% drop probability)   */
          if (q_average > qthresh_min) {
                   drop_pr = 0x3f;  /* (25% drop probability) */
          }
          if (q_average > (qthresh_min+q_step)) {
                   drop_pr = 0x7f;  /* (50% drop probability) */
          }
          if (q_average > (qthresh_max-q_step)) {
                   drop_pr = 0xbf;  /* (75% drop probability) */
          }
   }

   /*  Drop decision */
   if (random[1] < drop_pr) {
        /* PDU dropped */
        drop=true;
   } else {
        /* PDU not dropped, update Qaverage */
        Qaverage=q_average;
   }
}