Ldap authentication for asterisk sip users

The ldap server is running on the separate machine. I need to have ldap authentication for the sip users in the asterisk.
The configuration which i have done is,
in extconfig.conf
sipusers => ldap,“dc=bksys,dc=co,dc=in”,sip
sippeers => ldap,“dc=bksys,dc=co,dc=in”,sip
extensions => ldap,“dc=bksys,dc=co,dc=in”,extensions
sip.conf => ldap,“dc=bksys,dc=co,dc=in”,config

in res_ldap.conf

Actually the users in the ldap server is like “bala” with their password. The sip username is like numbers(e.g 43902740). I need to map the sip user to users in the ldap. For example i want to map 43902740 to bala. For this what i needs to more in the configuration.
Kindly revert back me this at the earliest.

Thanks in advance,