Oracle Database Discussions

In Data Guard Redo Transport and Network Best Practices for oracle database 10g R2 document, it has been recommended to set the size of TCP Socket buffers (RECV_BUF_SIZE & SEND_BUF_SIZE) to three times the bandwidth delay product (BDP).
You calculate BDP by multiplying Bandwidth with Round trip Time (RTT).
I have little confusion regarding RTT. When you use PING (and do not specify packet size) to find out RTT, you get RTT for 32 bytes packet. In case your Primary DB is generating redo at the rate of 4K/ms how would you calculate RTT? If i Simply ping my standby server from primary server with 32 bytes of data i get RTT equals to 1ms but if I ping standby server by sending a packet of 4K then i get RTT equals to 3ms. Which RTT value will i use in that case to find the BDP.