Question on RAS ICV (Integrity Check Value)

Hi Sometime back there was a thread of discussion on the RAS ICV. I tried to download the previous message digests. But i did not find any decisive mails for future H.323 versions. Can u please tell me how do the present implementations handle ICV generation and ICV verification (at the receiving side) ? I can only think of re-encoding/ decoding the message, which i think shall be a big processing overhead. Thanks in anticipation, aseem@trillium.com