Hi .. I think your question should be in regards of the performance of a device when using encryption for example a PIX 501E provides
■ Maximum clear-text throughput60 Mbps
■ Maximum throughput (DES)6 Mbps
■ Maximum throughput (AES-128)4.5 Mbps
■ Maximum throughput (3DES)3 Mbps
As you can see it depends of the device you are using and also of the encryption algorithm.
PLease rate it if you find this info helpfull