This article describes the best practices to configure XenApp 6 to deliver Avaya IP softphone R6.

With HDX RealTime audio enhancements in Citrix XenApp 6, you can publish Avaya IP softphone to your end users and enable a rich audio experience.

There are many different scenarios for using the Avaya softphone; the one discussed in this article is the Road Warrior mode which requires audio devices on the client machine. In this mode, the IP phone and the softphone are able to share the same extension number. The voice traffic also goes over the ICA audio virtual channel. This article describes how you can configure the softphone to get the best possible user experience in XenApp.

Tested Softphones and Operating System Platforms

The softphones specifically tested by Citrix with XenApp 6 are Avaya IP softphone R6. Citrix foresee no compatibility issues with other current Avaya softphones (such as one-X Agent). For the latest compatibility information, visit the Citrix Ready website.

Memory and CPU Consumption of Avaya Softphones

The memory and CPU consumption of the Avaya softphones are not measured by Citrix. Memory and CPU consumption might not increase linearly with the number of simultaneous users. 

Codec Selection and Bandwidth Consumption

Between the user device and the XenApp server in the data center, Citrix recommends using XenApp’s Optimized-for-Speech codec setting, also known as Medium quality audio. This codec is specially optimized for voice-over-IP. It consumes approximately 34 Kbps of network bandwidth (17 Kbps in each direction).

Between the XenApp server and the Avaya IP-PBX, the softphone uses whatever codec is configured or negotiated. G711 provides best voice quality but has the highest bandwidth requirement of 80 to100 Kbps per call (depending on Network Layer2 overhead). G729 provides good voice quality and has the lower bandwidth requirement of 30 to 40 Kbps per call (depending on Network Layer2 overhead). 

Configuration

The following are the XenApp configuration guidelines:

• Choose the Optimized-for-Speech (Medium quality) audio codec setting.

• On each user device, install the Citrix 12.0 online plug-in for Windows or the 11.100 release of the Linux Receiver (these versions include the Optimized-for-Speech audio codec technology).

• Use good quality headsets with noise and echo cancellation.

In addition, if delivering softphones to users on a Wide Area Network (WAN) connection, the following additional configuration settings are recommended:

• To ensure adequate processing power for real-time traffic, you might need to allocate two virtual CPUs when running XenApp on a hypervisor.

• Use Citrix Repeater and Branch Repeater between the data center and the remote office for Quality-of-Service (QoS). 

Citrix Access Gateway

The Avaya IP softphone is supported when Access Gateway Enterprise is configured to use the Windows plug-in and a unique Intranet IP is assigned per user. 

Installing the Softphone

The Avaya softphone must be configured to make it aware that it is running in a multi-user environment. You will receive few errors when you install the softphone on Windows Server 2008 R2. Ignore all errors and continue with the installation. The following are few errors that you are most likely to receive:

“Avaya IP Softphone R6 requires that the Telephony API (TAPI) services files are installed and configured on your system.

One or more of your TAPI files (for example: TAPI.DLL) is missing from your system. Avaya IP Softphone will not function until theTAPI services are installed and configured.”

The following is a screen shot of the error:

The installation continues if you ignore all the errors.

After the installation is complete, create the registry keys mentioned in the following table.

Caution! Refer to the Disclaimer at the end of this article before using Registry Editor.

Configuring the Softphone

There are no special steps required to publish the phone. After the softphone is published, you can launch the phone from your client. It will prompt you to log on to your extension.

1. Provide the details of the call server and user credentials.

   

2. After logging on, start the Tuning Wizard from Audio menu.

   

3. Ensure that Citrix HDX Audio is selected as the playback and recording device. 

   

4. Preferably, use a headset or handset. Select the appropriate option.

   

5. It is important to assure compatibility with XenApp. As shown in the following screen shot, select Use the following microphone recording level and change the position of the sidebar to the right-most position. 

   

Settings and Improvements in XenApp 6.0

There has been several audio enhancements that can help improve the audio experience in XenApp. The inbuilt codecs are optimized for delivery of speech, and therefore help improve the user experience of published softphones. The following are some of the settings that can help you fine-tune XenApp for softphones.

1. Choose medium quality (Optimized-for-speech) audio for softphones.

2. Ensure echo cancellation is enabled, which is available from client 12.0 onwards. This can be verified using the registry key mentioned in the following table:

Notes:

• During an active two-way softphone conversation, there is an impact on CPU usage of about 15 to 20 percent.

• For low bandwidth scenarios, the low bandwidth audio setting might perform better.

• This functionality is only valid if you have a client that is version 12.0 or later.