We are trying to enable TLS on top of ldap connections.  Once, i change startls to FALSE or required

$config['auth_ldap_starttls'] = TRUE;

$config['auth_ldap_starttls'] = 'required';

I get the following message:

What does it mean exactly ?  Version mismatch ? Cert error ? 

When I check packet capture, i see the following:

And inside the client response ( packet # 9 ), there is this:

Does it mean that observium can't find a certificate ?  If so, which directory should i place certs ? I have another app on the same box that is using ldap with tls and it is working just fine.

Also, what TLS versions are supported by observium ? 

Has anybody experienced the same issue ? Were you able to resolve it ? 

Appreciate your responses.

Thank you