Chaining Overlay with Keep Alive Function

overlay                 chain 
chain-rebind-as-user    FALSE 
chain-return-error      TRUE 
chain-uri               ldap://origin.ldap.amadeus.net:9389 
chain-idassert-bind     bindmethod="simple" 
                        binddn="cn=manager,ou=diradmin,dc=amadeus,dc=com" 
                        credentials="XXXXX" 
                        mode="self" 
                        flags=non-prescriptive 
                        starttls=yes 
                        tls_cacert="/opt/symas/ssl/ca_roots/1acacert.pem" 
                        tls_reqcert=never 
chain-tls               start 
                        starttls=yes 
                        tls_cacert="/opt/symas/ssl/ca_roots/1acacert.pem" 
                        tls_reqcert=never 
chain-keepalive 120:10:15