Maybe the following will help you........
PC-NFS Authentication Service
By default, PC-NFS presents itself to NFS servers as the nobody user. With
nobody privileges, all personal computer user files appear as owned by nobody,
and consequently you cannot distinguish between different personal computer users.
The authentication capability of the rpc.pcnfsd daemon allow you to monitor system
resources and security by recognizing individual users and assigning them different
privileges.
With the rpc.pcnfsd daemon running, a PC-NFS user can issue the net name
command from a personal computer to log in to PC-NFS in the same manner as
a user can log in to AIX. The user's name and password are verified by the
rpc.pcnfsd daemon. This authentication procedure does not make a server more
secure, but it does provide more control over access to files that are available
through NFS.