Main difference between RSA Sig and RSA Enc.

[BUYCK Jacky FTRD/DMI/CAE <jacky.buyck@rd.francetelecom.com>]

Title: Main difference between RSA Sig and RSA Enc.

Hi.
I work on IPSec tunnel under CISCO routers platform and I wonder what is the difference between the tw oauthentification method name :

        - RSA Sig
        - RSA Enc

I know that RSA Sig is the default method to negociate IPSec tunnel using X509 certificate but I wonder what is RSA Enc.

Anyone can give me some hints ?
Thansk

J.B