which parameter must match the binddn parameter of the master server?

Wrong, correct is updatedn

13.4.2. Set up the slave slapd
Install the slapd software on the host which is to be the slave slapd server. The configuration of the slave server should be identical to that of the master, with the following exceptions:
Do not include a replica directive. While it is possible to create “chains” of replicas, in most cases this is inappropriate.
Do not include a replogfile directive.
Do include an updatedn line. The DN given should match the DN given in the binddn= parameter of the corresponding replica= directive in the master slapd config file.
Make sure the DN given in the updatedn directive has permission to write the database (e.g., it is listed as rootdn or is allowed access by one or more access directives).
Use the updateref directive to define the URL the slave should return if an update request is received.

http://www.openldap.org/doc/admin21/replication.html