How to define a large Tx Buffer and a little Rx Buffer?

How to define a large Tx Buffer and a little Rx Buffer?

We are developping a TCP project on RCM3200, in which TCP_BUF_SIZE is defined to 5840.
But each of Tx & Rx buffer has only 2920(5840/2=2920).

In our project much datum(about 10 Kbytes/s) need be sent,but a little datum(about 9 Bytes/min) need be sent.
So we wish a large Tx Buffer and a little Rx Buffer.
But we donot know how to define them(a large Tx Buffer and a little Rx Buffer).

Can you help us?
Thanks.
:stuck_out_tongue: