[Koha] how to ldap configration on koha

[tibabu beza]

how to ldap configration on koha. i try to configra ldap on koha like below but it give me the following fantal error.
how I can correct it  

<useldapserver>1</useldapserver>
  <!-- LDAP SERVER (optional) -->
  <ldapserver id="idm">
    <hostname>192.168.5.55</hostname>
    <base>dc=idmdomain,dc=edu</base>
    <user>cn=kohaadmin,ou=koha,dc=idmdomain,dc=edu</user>             <!-- DN, if not anonymous -->
    <pass>adama</pass>          <!-- password, if not anonymous -->
    <replicate>1</replicate>       <!-- add new users from LDAP to Koha database -->
    <update>1</update>             <!-- update existing users in Koha database -->
    <auth_by_bind>1</auth_by_bind> <!-- set to 1 to authenticate by binding instead of
                                        password comparison, e.g., to use Active Directory -->
    <principal_name>%s at my_domain.com</principal_name>
                                   <!-- optional, for auth_by_bind: a printf format to make userPrincipalName from koha userid -->
    <mapping>                  <!-- match koha SQL field names to your LDAP record field names -->
      <firstname    is="givenname"      ></firstname>
      <surname      is="sn"             ></surname>
      <address      is="postaladdress"  ></address>
      <city         is="l"              >Athens, OH</city>
      <zipcode      is="postalcode"     ></zipcode>
      <branchcode   is="branch"         >MAIN</branchcode>
      <userid       is="uid"            ></userid>
      <password     is="userpassword"   ></password>
      <email        is="mail"           ></email>
      <categorycode is="employeetype"   >PT</categorycode>
      <phone        is="telephonenumber"></phone>
    </mapping> 
  </ldapserver> 

Koha error

The following fatal error has occurred:

No "ldapserver" in server hash from KOHA_CONF: /etc/koha/koha-conf.xml at /usr/share/koha/lib/C4/Auth_with_ldap.pm line 53.
Compilation failed in require at /usr/share/koha/lib/C4/Auth.pm line 44, <DATA> line 275.
BEGIN failed--compilation aborted at /usr/share/koha/lib/C4/Auth.pm line 47, <DATA> line 275.
Compilation failed in require at /usr/share/koha/intranet/cgi-bin/mainpage.pl line 23, <DATA> line 275.
BEGIN failed--compilation aborted at /usr/share/koha/intranet/cgi-bin/mainpage.pl line 23, <DATA> line 275.

Apache	Server version: Apache/2.2.14 (Ubuntu) Server built: Apr 13 2010 19:28:27
Koha	3.00.06.010
Koha DB	3.0006010
MySQL	mysql Ver 14.14 Distrib 5.1.41, for debian-linux-gnu (i486) using readline 6.1
OS	Linux tibabu-desktop 2.6.32-22-generic-pae #33-Ubuntu SMP Wed Apr 28 14:57:29 UTC 2010 i686
Perl	5.010001