Supported scenarios include the following:

• An enterprise Office Communications Server user is able to place a local or long distance outbound call to the public switched telephone network (PSTN) by using a service provider Session Initiation Protocol (SIP) trunk.
  
  
• An enterprise Office Communications Server user is able to receive an inbound PSTN call to his/her Direct Inward Dialing (DID) number by using a service provider SIP trunk. If the service provider supports number portability, you can keep your pre-existing DID.
  
  
• The Calling Party Number (that is, used to show caller ID) is supplied (if allowed) for inbound and outbound calls.
  
  
• An active call can be placed on hold and off hold.
  
  

Any other scenario is outside the scope for the Office Communications Server 2007 R2 release. Some examples include the following:

• E.911 support for outbound calls.
  
  
• Invoking any service provider call conferencing functionality over the SIP trunk. (This is separate from the conferencing functionality provided by Office Communications Server.)
  
  
• Invoking any service provider call forwarding/redirect functionality over the SIP trunk. (This is separate from the call forwarding/redirect functionality provided by Office Communications Server.)