Portal and R/3 Integration with LDAP

Hi,

If we connect our Portal UME engine to LDAP and also want to connect our R/3 system to LDAP, do both Portal and R/3 maintain separate connections to LDAP? Or do we connect our Portal UME to SAP Web AS ABAP and then connect SAP Web AS ABAP to LDAP? The following link (http://help.sap.com/saphelp_nw04s/helpdata/en/0c/632441cd87a12be10000000a1550b0/content.htm) seems to suggest that we connect our Portal UME to SAP Web AS ABAP and then connect SAP Web AS ABAP to LDAP. I just want to make sure as I've heard most Portal installations connect directly to LDAP.