com.day.ldap.LDAPConnThread network error

I am trying to configure LDAP with my AEM(5.6) instance. The error.log file shows this:

com.day.ldap.LDAPConnThread network error on LDAP connection java.io.IOException
        at com.day.ldap.client.JDAPBERTagDecoder.getElement(JDAPBERTagDecoder.java:119)
        at com.day.ldap.ber.stream.BERTag.<init>(BERTag.java:85)
        at com.day.ldap.ber.stream.BERElement.getElement(BERElement.java:149)
        at com.day.ldap.LDAPConnThread.run(LDAPConnThread.java:443)

when I try to syncAllUsers() from the jmx console, here are the errors I see:

Error.log:
com.day.ldap.LDAPSearchResults Exception: com.day.ldap.LDAPException: error result (1); 00000000: LdapErr: DSID-0C090627, comment: In order to perform this operation a successful bind must be completed on the connection., data 0, vece; Operations error com.day.ldap.LDAPException: error result (1); 00000000: LdapErr: DSID-0C090627, comment: In order to perform this operation a successful bind must be completed on the connection., data 0, vece; Operations error

Ldap.log:
com.day.crx.security.ldap.principals.LDAPPrincipalProvider Error finding user * com.day.crx.security.ldap.LDAPRepositoryException: LDAP error: com.day.ldap.LDAPException: error result (4); Sizelimit exceeded

Need insights on this