As described in the section Group Policy for Unified Communications Clients, one way to provide the appropriate registry settings for each user when deploying Office Communicator 2007 R2 is to define Group Policies by using the Communicator.adm administrative template. The Communicator.adm template and Group Policy documentation can be downloaded at http://go.microsoft.com/fwlink/?LinkID=140494 . For instructions about how to install the template, see Group Policy for Unified Communications Clients.

With the Kerberos or NTLM authentication method, the users Windows credentials are used automatically for authentication. In a typical Office Communications Server deployment that uses Kerberos protocol, NTLM, or both, users should not have to enter their credentials every time that they sign in, unless you want to explicitly require them to do this. The DisableNTCredentials registry key controls whether users are required to enter credentials every time that they sign in.

If users are unintentionally being prompted for credentials, the DisableNTCredentials key may be unintentionally configured on client computers, possibly through a Group Policy. To prevent the additional prompt for credentials, change the value for the following registry key to 0:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Communicator\DisableNTCredentials

To make this change to all clients in a pool, use the Communicator.adm file to update the Group Policy object for the pool.

By default, Communicator disables hyperlinks in instant messages so that URLs are presented as plain text. The behavior of hyperlinks can be modified by two different means. First, you can configure the EnableURL registry key to modify hyperlink behavior. When the EnableURL key is set to 1, hyperlinks become active and clickable in instant messages.

Second, the Intelligent Instant Message Filter in the server pool settings determines whether active hyperlinks are blocked, allowed, or converted to plain text. For more information about the Intelligent Instant Message Filter, see the Configuring Intelligent IM Filteringand Configuring URL Filteringtopics in the Administering Office Communications Server 2007 R2 documentation. The settings that you configure apply across the pool. Because these filters are applied at the server, they take precedence over the EnableURL registry key that is set on the client.

If you want users in the pool to be able to exchange active hyperlinks, either do not configure the Intelligent IM Filter or configure the Intelligent IM Filter to allow active hyperlinks. Then, configure the EnableURL key on clients (for example through Group Policy) with a setting of 1.

If you want only a select group of users to be able to exchange active hyperlinks, the users will need to be in a separate pool or Active Directory container so that you can apply the EnableURL policy to the users. Then, you must not configure the Intelligent Instant Message filter to block hyperlinks.

Organizations that want to disable video can use Group Policy, but should be aware that there are two policies affecting the use of video. The DisablePC2PCVideo disables video for sessions between two participants. The DisableAVConferencing policy disables video for conferencing sessions with more than two participants. If you want to disable all video, you should enforce both policies.

The availability of computer-to-computer calling depends on whether your organization has a Voice license, and the Telephony Mode that you have selected. As described in the section Office Communications Server 2007 R2 CALs, setting the TelephonyMode registry key to 4 disables computer-to-computer calling so that only remote call control is available. To set this registry key for clients in your organization, you can enable the Telephony Mode policy and define a setting of 4. Use the Communicator.adm template file described in the section Group Policy for Unified Communications Clients.

Also, see the Microsoft Knowledge Base article 11402, “You cannot disable the Communicator Call option in Office Communicator 2007,” at http://go.microsoft.com/fwlink/?linkid=147017 .

Several factors can affect the file transfer feature in Communicator, and the handout and multimedia playback features in the Live Meeting client. These factors include the Intelligent Instant Message Filter feature in Office Communications Server, Group Policy configuration, and client-side, antivirus software. The following list describes the various factors that may be causing file transfer issues.

• DisableFileTransfer registry key– When this Communicator registry key is set to 1, it disables the Send a File option in Communicator. If the issue is affecting one user or a few users, try disabling this registry key (set it to 0) to see whether the issue is resolved.
  
  
• Prevent File Transfer policy– When this Communicator policy is enabled, it disables the Send a File option in Communicator for the clients affected by the policy. If the issue is affecting all users in a pool, check whether this policy is enabled.
  
  
• Intelligent Instant Message Filter– The File Transfer Tab in the Intelligent Instant Message Filter feature allows administrators to filter the file types that can be transferred in instant message conversations, Live Meeting handouts, and multimedia playback. If the issue affects all users, the filter may have been configured unintentionally to block the file types that you want to allow. Verify the configuration of the Intelligent Instant Message Filter in the server pool settings. For more information about the Intelligent Instant Message Filter, see the Configuring Intelligent IM Filteringand Configuring File Transfer Filteringtopics in the Administering Office Communications Server 2007 R2 documentation.
  
  
• Antivirus software– An antivirus program that is running on the client might be preventing certain file types from being transferred. Try temporarily disabling the antivirus program to see whether this resolves the issue.
  
  
• Attachment Management Group Policy– Attachment Management is a set of Windows Component policies that define the file types that the client can access, based on whether an attachment is received from the restricted zone or Internet zone. You can specify high, moderate, and low risk file types. When these policies are not set or are disabled, Windows uses a built-in list of file types that can pose risk. If a user or a few users are experiencing issues with accessing a common file type such as .doc or .docx, you can check whether the high risk or medium risk policies are enabled and whether that file type is listed. For more information about the Attachment Manager, see the Microsoft Knowledge Base article 883260, Description of how the Attachment Manager works in Windows XP Service Pack 2, at http://go.microsoft.com/fwlink/?linkid=147020 .
  
  

To view or modify the Attachment Management policies

1. In the Group Policy Object Editor, expand User Configuration, expand Administrative Templates, expand Windows Components , and then click Attachment Manager.
   
   
2. Double-click Inclusion list for high risk file typesand check whether the affected file name extensions are in the list. If they are in the list, remove them.
   
   
3. Double-click Inclusion list for moderate risk file typesand check whether the affected file name extensions are in the list. If they are in the list, remove them.
   
   
4. Double-click Inclusion list for low risk file types. Enable this policy and add the affected file types to the list. Click OK.
   
   
5. Refresh the policy by running gpupdate /forceor log on again.
   
   

Audio, video, and desktop sharing problems can be caused by the misconfiguration of certain registry keys or Group Policies.

MaxMediaPort and MinMediaPort

If you use the port range registry key settings to reduce the ports that can be used for media, we recommend that you do this according to the minimums described in this section.

For client endpoints, the port range should not be reduced to the point where it can compromise the ability of the media stack to negotiate audio, video, and desktop sharing communication ports during session setup or during a call. More specifically, for an Office Communicator 2007 R2 client, the minimum port range should be 40. A smaller range of ports can result in errors during call transfer, when starting desktop sharing, and conference escalation scenarios.

Configuring a minimum of 40 ports will enable the client to evaluate the candidate transport addresses that it can use to stream audio, video, and data to another client, as described in the IETF Interactive Connectivity Establishment (ICE) protocol. Candidate addresses include local addresses and an address on the A/V Access Edge server. A minimum of 40 ports in the port range will also accommodate any escalations from a peer-to-peer call to a conference. (An escalation of a peer-to-peer call to a conference triggers a temporary doubling of the ports being used.)

The registry keys for these settings are as follows:

• HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Communicator\Portrange\Enabled REG_DWORD 1
  
  
• HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Communicator\Portrange\MaxMediaPort REG_DWORD 40039 (for example)
  
  
• HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Communicator\Portrange\MinMediaPort REG_DWORD 40000 (for example)
  
  

MaxAudioVideoBitRate

Important:
The MaxAudioVideoBitRate setting is expressed in bits, not kilobits. A setting of 512000 would be practical, whereas a setting of 512 (which you might enter if you assumed the setting is in kilobits) would not provide enough bandwidth for audio and video.

The MaxAudioVideoBitRate can be used to limit the bandwidth that Communicator can use for audio and video calls. If this key is unintentionally set too low, it can cause audio and video failures.