Last Post: October 1, 2006:
A MAC service data unit (MSDU) that will be TKIP encrypted is first appended with an 8 octet TKIP MIC. Then the new data unit is considered for fragmentation.
If the TKIP encrypted data unit will meet the fragmentation threshold for size it is first fragmented into a series of data units (fragments) each of which will be small enough after encryption to not exceed the fragmentation threshold. Only the first data unit in the series carries the MIC. All but perhaps the last data unit is the same size.
Then each data unit is TKIP encrypted (adding 12 octets each) and queued for transmission.
It looks like both statements are correct. It helps everyone if you provide both the book name and page number for suspect quotations.
I hope this helps. Thanks. /criss