net use: how are passwords passed from client to server

[mshen at bcm.tmc.edu]

If I log on to an NT domain,
and mount a share from an NT server (which may be a DC, or
a member of a domain), I do not have to type my NT
password at all.

If I type "net use ..." to mount a share on a Samba
server, the first time I get a prompt to type my Unix password.
When I mount another share from the same Samba server,
I need to type my password again.
(1) Why at all
(2) Why again?
Maybe I should make the Samba server a BDC and make
it to use the PDC of my logon domain?

In trying to understand the problem, I started to wonder
how passwords get passed from client to server. When Samba
uses Unix passwords it must somehow get at the cleartext
passwords. But the sniffer does not show cleartext passwords,
instead may be I was seeing the LAMNAN and NT hashes?

Thanks for any pointers.
Mingzuo