Throughput.

hi,

i configured ipsec in two linux machines which are connected back-to-back.
i tested the through put between these machines.
and the troghuput is coming same for most of the apcket size and it only differes as fallows:
throghput is in mbps.

pkt size            IPSEC disabled.                                  IPSEC enabled.
--------------------------------------------------------------------------------------------------------
32                     24.42                                                  24.42
64                     48.83                                                  48.83
128                   97.66                                                   97.66
256                   97.66                                                   97.66
512                   97.66                                                   97.66
1024                 86.81                                                   86.81
2048                 91.92                                                   86.81 
4096                 89.3                                                     84.5

i want to know will their be any difference in 
throughput - ipsec enabled and 
throughput -ipsec disabled.

Thanx in advance.