Hello~ I don't understand to following. ---------------------------- Writing the Transmit control word. MSF_TBUF_CONTROL_BASE is associated with TBUF element. I thought MSF_TBUF_CONTROL_BASE + tbuf_element, But MSF_TBUF_CONTROL_BASE + (tbuf_element <<3) in IXP2400/2800 Programming chapter 5 Um... What is reason about tbuf_elemnt <<3? Please, advice me~ ref. MSF_TBUF_CONTROL_BASE = 0x1800 Thanks.