Using different clients to change password result in different stored password's form

Hi list, as I don't know if this behavior comes from my slapd itself, I'm not giving too much details on it. Here is what's happening: in slapd.conf I have: 'password-hash {SSHA}' so I'm expecting that each password attribute change results in a new SSHA hashed password. Our users can change their password on several ways which all result in different stored password'hashes (cleartext (!), SHA, but not SSHA). Does the hashing type is specified on the client's side and not enforced by the directory? Can someone give me some pointers for doc explaining how password's change mechanism works in openldap?

kfx