In order for Lync Server 2010 to be able to communicate with OCS 2007/OCS 2007 R2 servers and vice versa they need to know about each other.
To make Lync Server know about OCS 2007/OCS 2007 R2 servers you have to use the cmdlets Merge-CsLegacyTopology/Publish-CsTopology/Enable-CsTopology and Import-CsLegacyConferenceDirectory. These cmdlets will read information from Active Directory and import it into the configuration store for Lync Server 2010 – Central Management Server (CMS).
Similar OCS 2007/OCS 2007 R2 servers needs to learn about Lync Server entities. This is done by creating relevant objects in Active Directory representing these entities. These objects are sometimes referred to as backwards compatibility objects. They are created during activation when you run the cmdlet Enable-CsTopology and will be created for the complete topology.
The types of AD objects created are shown in the following table:
Type of Object
CN=Application Contacts, CN=RTC Service,…
An application contact object will be created for the applications running on Lync Server application servers (Get-CsService –ApplicationServer will show the servers and applications)
CN=Conference Directories, CN=RTC Service,…
A conference directory object will be created for each Lync Server UserServices instance (Get-CsService –UserServer)
CN=Global Settings,CN=RTC Service,…
A trusted server object is created for each Lync Server Registrar instance (Get-CsService –Registrar)
A pool tree structure is created for each Lync Server Registrar instance (pool, CN=Microsoft, CN=Lc Services) (Get-CsService –Registrar)
CN=Trusted MCUs,CN=RTC Service,…
A trusted MCU object is created for each MCU defined on each Lync Server ConfServices instance (Get-CsService –ConferencingServer will show the Mcus)
CN=Trusted Services,CN=RTC Service,…
A trusted service object is created for each service running on each Lync Server server. Types of service include QoS, MediationServer, HomeServer and MRAS
CN=Trusted WebComponentsServers,CN=RTC Service,…
A trusted web components server object is created for each Lync Server WebServices instance (Get-CsService –WebServer)
Location refers to the location in Active Directory, either in the Configuration naming context (CN=Services,CN=Configuration,DC=…) or in the Default naming context (CN=Microsoft, CN=System, DC=…)
The backwards compatibility objects are removed from Active Directory when the cmdlet Publish-CsTopology is run on a topology where the server has been removed.
Small tip: If you look in Active Directory using ADSIedit or LDP you’ll notice that objects created by Lync Server use mixed case characters in the CN while OCS 2007/OCS 2007 R2 use upper case characters in the CN.