where can I find the "sequence control" in the packet?

I don't know how to find the seq_ctl information in the sending-out packet.
I think it should be found in the function orinoco_xmit(), but the
comment in this function make me confused,

/* Clear the 802.11 header and data length fields -some
 * firewares (e.g. Lucent/Agere 8.xx) appear to get confused 
 * if this isn't done. */
hermes_clear_words(hw, HERMES_DATA0, 
                              HERMES_802_3_OFFSET - HERMES_802_11_OFFSET);
if all the 802.11 information is cleared, where can I find it? is it
useless for orinoco driver?

the 802.11 header defined ad below:
struct ieee802_11_hdr {
         u16 frame_ctl;
         u16 duration_id;
         u8 addr1[ETH_ALEN];
         u8 addr2[ETH_ALEN];
         u8 addr3[ETH_ALEN];
         u16 seq_ctl;
         u8 addr4[ETH_ALEN];
} __attribute__ ((packed));


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