The main consideration for planning for A/V conferencing is understanding the network bandwidth required by the type of A/V conferencing your organization requires.

Before you enable users for A/V conferencing, you should ensure your network can handle the resulting load. Without sufficient network bandwidth, the end-user experience may be severely degraded.

When planning for bandwidth usage per scenario, use the following table, which describes the average amount of bandwidth used per media type. These numbers are preliminary and will be updated in future releases.

Additionally, a new feature in Communications Server 2010, Call Admission Control, can help you manage the network bandwidth used by A/V Conferencing. For details, see Overview of Call Admission Control.

Audio/Video Capacity Planning

The network bandwidth numbers in this table represent one-way traffic only and take silence-suppression into account.

When you calculate the actual bandwidth usage for a certain scenario, it is important to understand the actual media flows, which are as follows:

In a two-party scenario:

• Users send audio streams only while they speak.
  
  
• Both participants receive audio streams.
  
  
• If video is used, both users send and receive video streams during the entire call.
  
  

In a Conferencing scenario (that is, a call with more than two participants):

• Users send audio streams only while they speak.
  
  
• All participants receive audio streams.
  
  
• If video is used, only two participants upload a video stream at a time (the Active Speaker and the Previous Active Speaker)
  
  
• If video is used, all participants receive video streams.
  
  
• If a Microsoft RoundTable conferencing device is used, two participants are uploading a RoundTable device panorama stream.
  
  
• If a RoundTable device is used, all participants are receiving a RoundTable device panorama stream.
  
  

If you deploy audio conferencing on your network, your users will need audio devices such as headsets to participate. If you also deploy video conferencing, you will need to roll out video devices, such as webcams for users and the RoundTable device for conference rooms.

We recommend that you use Microsoft UC-certified devices for all device types, to ensure an optimal end-user experience. For details about UC-certified devices, see http://go.microsoft.com/fwlink/?LinkId=186185.

For either audio or video devices, device rollout and user training are important issues for you to consider and plan for, to maximize your return on investment in conferencing.

You can greatly increase the benefits of your investment in Communications Server conferencing by enabling external users to also participate in conferences when invited. External users can include:

• Your organization’s own users, when they are working outside your firewalls and are using their laptops or other Communications Server devices.
  
  
• Users from companies you work with who also run Communications Server; to enable your users to easily contact these users, you create federated relationships with these companies.
  
  
• Any other external users who are invited specifically by your users to join specific conferences. A meeting organizer in your company can send an email invitation for a conference to an external user. The email includes a link that the outside user can click to join the conference securely.
  
  

To enable any or all of these scenarios, you deploy an Edge Server to enable secure communications between your Communications Server deployment and external users. The Communications Server solution using edge servers provides higher quality media than other solutions such as a virtual private network (VPN). For details, see External User Access.

Additionally, whether or not you deploy Edge Servers, you can enable users (either inside or outside your organization) to dial in from standard PSTN phones to join on-premise audio conferences. This is accomplished by deploying Communications Server dial-in conferencing.

Microsoft Communications Server 2010 includes many improvements and enhancements to conferencing capabilities. For more information on these changes, see New Conferencing Features.

However, these changes require you to be aware of some conferencing interoperability issues in this Beta release. If you are going to have this Beta release interoperate with previous versions of Communications Server and its clients, you must be aware of the following issues:

• Users using Microsoft Communicator "14" cannot schedule Live Meeting online conferences, or modify any migrated meetings of this type.
  
  
• Users using Microsoft Communicator "14" who need to attend Live Meeting online conferences hosted on servers running Office Communications Server 2007 R2 must have the Live Meeting client installed on their computer (in addition to Microsoft Communicator "14") to attend these meetings.
  
  
• When Live Meeting online conferences are migrated to Microsoft Communications Server 2010, meeting content does not migrate. If this content is needed, it must be uploaded again.
  
  
• Users who are migrated from previous versions of Office Communications Server to Communications Server 2010 and who use Microsoft Communicator "14" will receive a new assigned dial-in conference ID the first time they schedule an assigned dial-in conference meeting. They can use this new assigned dial-in conference ID to both schedule and attend meetings. Their old ID will continue to work for attending meetings, but not for scheduling new meetings.
  
  
• Users in federated organizations who are using Microsoft Office Communicator 2007 or Microsoft Office Communicator 2005 clients cannot join Communications Server 2010 meetings in your organization if those meetings are locked by the organizer.