ATH_AGGR_DELIM_SZ
(((((_len) + ATH_AGGR_DELIM_SZ) < ATH_AGGR_MINPLEN) ? \
(ATH_AGGR_MINPLEN - (_len) - ATH_AGGR_DELIM_SZ) : 0) >> 2)
mindelim = (minlen - pktlen) / ATH_AGGR_DELIM_SZ;
al_delta = ATH_AGGR_DELIM_SZ + bf->bf_state.bfs_pktlen;