Sink模块的状态机很简单，只有INIT和DISCARD两个，非强制状态只有DISCARD用于包的销毁。Sink模块的作用就是销毁从输入流接收到的包，并且返回关于包的一系列统计量。
Init的入口代码为
/* Initilaize the statistic handles to keep */
/* track of traffic sinked by this process. */
bits_rcvd_stathandle =op_stat_reg ("Traffic Sink.Traffic Received (bits)", OPC_STAT_INDEX_NONE,OPC_STAT_LOCAL);
bitssec_rcvd_stathandle =op_stat_reg ("Traffic Sink.Traffic Received (bits/sec)", OPC_STAT_INDEX_NONE,OPC_STAT_LOCAL);
pkts_rcvd_stathandle =op_stat_reg ("Traffic Sink.Traffic Received (packets)", OPC_STAT_INDEX_NONE,OPC_STAT_LOCAL);
pktssec_rcvd_stathandle =op_stat_reg ("Traffic Sink.Traffic Received (packets/sec)", OPC_STAT_INDEX_NONE, OPC_STAT_LOCAL);
ete_delay_stathandle =op_stat_reg ("Traffic Sink.End-to-End Delay (seconds)", OPC_STAT_INDEX_NONE,OPC_STAT_LOCAL);
bits_rcvd_gstathandle =op_stat_reg ("Traffic Sink.Traffic Received (bits)", OPC_STAT_INDEX_NONE,OPC_STAT_GLOBAL);
bitssec_rcvd_gstathandle =op_stat_reg ("Traffic Sink.Traffic Received (bits/sec)", OPC_STAT_INDEX_NONE,OPC_STAT_GLOBAL);
pkts_rcvd_gstathandle =op_stat_reg ("Traffic Sink.Traffic Received (packets)", OPC_STAT_INDEX_NONE,OPC_STAT_GLOBAL);
pktssec_rcvd_gstathandle =op_stat_reg ("Traffic Sink.Traffic Received (packets/sec)", OPC_STAT_INDEX_NONE, OPC_STAT_GLOBAL);
ete_delay_gstathandle =op_stat_reg ("Traffic Sink.End-to-End Delay (seconds)", OPC_STAT_INDEX_NONE,OPC_STAT_GLOBAL);
op_stat_reg函数的作用是返回进程模型中节点或模块统计量，即初始化统计量句柄，第一个参数为统计量所在组的名称
所以上述代码分别返回的是局部统计量和全局统计量，包括：收到的bit数，bit速率，包数，包速率，端对端延时
DISCARD仅有出口代码：
/* Obtain the incoming packet. */
pkptr = op_pk_get (op_intrpt_strm ());
从输入流中获取包的指针
/* Caclulate metrics to be updated. */
pk_size = (double) op_pk_total_size_get (pkptr);
ete_delay = op_sim_time () - op_pk_creation_time_get (pkptr);
计算包的总体大小和包传输延时
/* Update local statistics. */
op_stat_write函数功能为写入统计量，第一个参数为统计量的统计量句柄，第二个参数为统计量将写入的值。
op_stat_write (bits_rcvd_stathandle, pk_size);收到的bit数
op_stat_write (pkts_rcvd_stathandle, 1.0); 收到的包
op_stat_write (ete_delay_stathandle, ete_delay);端对端延时
op_stat_write (bitssec_rcvd_stathandle, pk_size); bit速率
op_stat_write (bitssec_rcvd_stathandle, 0.0);
op_stat_write (pktssec_rcvd_stathandle, 1.0); 包速率
op_stat_write (pktssec_rcvd_stathandle, 0.0);
/* Update global statistics. */全局统计量
op_stat_write (bits_rcvd_gstathandle, pk_size);
op_stat_write (pkts_rcvd_gstathandle, 1.0);
op_stat_write (ete_delay_gstathandle, ete_delay);
op_stat_write (bitssec_rcvd_gstathandle, pk_size);
op_stat_write (bitssec_rcvd_gstathandle, 0.0);
op_stat_write (pktssec_rcvd_gstathandle, 1.0);
op_stat_write (pktssec_rcvd_gstathandle, 0.0);
/* Destroy the received packet. */
op_pk_destroy (pkptr); 销毁包