Are you sure your host is dsd? if so try like below :

LITTLE=
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = dsd)(PORT = 1521))
)
(CONNECT_DATA = (SID = LITTLE)(SERVER = DEDICATED))
)

Also try commenting out the following line in sqlnet.ora :
# NAMES.DIRECTORY_PATH= (TNSNAMES, ONAMES)