Dial-in conferencing requires at least one Mediation Server and at least one PSTN gateway.

You can deploy a Mediation Server in a central site or in a branch office. In a central site, you can collocate a Mediation Server on a Front End pool or Standard Edition Server, or you can deploy it on a stand-alone server or pool. In a branch office, you can deploy a Mediation Server on a stand-alone server or as a component of the Survivable Branch Appliance (SBA).

You can deploy a PSTN gateway in a central site or in a branch office. In a branch office, the PSTN gateway can be stand-alone or a component of the SBA.

Note:
We recommend that you deploy a PSTN gateway that supports media bypass because media bypass reduces resource utilization on the Mediation Server. PSTN gateways that support media bypass handle only signaling, and not the media traffic.

For details about planning your configuration for Mediation Servers and PSTN gateways for dial-in conferencing, see Components and Topologies for Mediation Server.

During dial-in configuration, you create dial plans and dial-in conferencing access numbers. Dial plans are sets of normalization rules that specify the number and pattern of digits in a phone number and translate the phone number into the standard E.164 format for call routing. Dial-in conferencing access numbers are the numbers participants call to join a conference.

Every dial-in conferencing access number must be associated with at least one dial plan. Dial-in conferencing regions associate a dial-in conferencing access number with its dial plans. When you set up a dial plan, you specify the dial-in conferencing region that applies to the dial plan. Then when you create the dial-in access number, you select the regions that associate the access number with the appropriate dial plans.

When you create a dial plan, you specify the scope of the dial plan: user scope, pool scope, or site scope. Every user is assigned the dial plan from the narrowest scope that applies to the user. For example, a user is assigned a user-level dial plan, if one applies. If a user-level dial plan does not apply, the user is assigned a pool-level dial plan. If a pool-level dial plan does not apply, the user is assigned a site-level dial plan. If a site-level dial plan does not apply, the user is assigned the global dial plan.

Before you configure the dial plans, is it important to plan how you want to name and use regions. The following considerations apply to dial-in conferencing regions:

• A region is typically a geographical area that is associated with an office or group of offices.
  
  
• Languages are associated with dial-in access numbers. If you support geographical areas that have multiple languages, you should decide how you want to define regions to support the multiple languages. For example, you might define multiple regions based on a combination of geography and language, or you might define a single region based on geography and have a different dial-in access numbers for each language.
  
  
• When a user schedules a meeting, by default the meeting uses the region specified by that user's dial plan.
  
  
• By default, the first three dial-in access numbers for the region are included in the meeting invitation.
  
  
• It is important to name regions so that they are clearly recognizable. The user can use the names of the regions to change a meeting's region so that different access numbers are included in the invitation. (The user uses the Conferencing Add-in for Microsoft Office Outlook to change the region).
  
  
• Regions should be designed so that any invitee who wants to dial into a conference can see a local access number in the conference invitation.
  
  
• You can configure the order in which access numbers within a region appear on the Dial-in Conferencing Settings Web page (and, therefore, the order in which they appear in the conference invitation) by using Communications Server Management Shell cmdlets.
  
  
• Any user from any location can call any dial-in access number to join a conference.
  
  

Concepts