Support for Avaya Softphones - XenApp/XenDesktop

Support for Avaya Softphones - XenApp/XenDesktop

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Article ID: CTX124634

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Description

This article describes how to configure XenApp/XenDesktop to support Avaya Softphones.
The preferred method for delivering Avaya softphones from XenDesktop and XenApp is the Avaya VDI Communicator (see http://www.avaya.com/usa/product/vdi-communicator). This article also describes the fallback approach of delivering softphones using generic HDX RealTime technologies.

Configuration Guidelines and Test Report

XenDesktop 3 Feature Pack 1 unveiled the new Spectrum audio subsystem, offering broad compatibility with softphones and the voice chat features of unified communications applications. With XenDesktop 4 and the 11.2 Citrix online plug-in for Windows, Citrix introduced new audio codec technology that delivers brilliant voice clarity with minimal bandwidth consumption. This article summarizes our test results with Avaya softphone applications delivered using the VDI model of FlexCast, and provides tips for optimal configuration.

Even before the Spectrum audio subsystem was introduced, Avaya softphones could be delivered in control mode (also known as telecommuter mode or dual connect mode) where the application controls a physical telephone set, be it your office phone, mobile phone, home phone or whatever. From the Avaya softphone application, users can transfer calls and use speed dial, call history, account codes and other features normally available only on a proprietary office phone. Customers tell us that this approach has made it practical for them to support at-home workers and thereby reduce the cost of office space. For traveling workers, it means they can use any phone and get the same IP-PBX features they enjoy when in the office.

With the introduction of XenDesktop 4 it enables VoIP mode (also known as My Computer Mode or softphone-only mode or road warrior mode). In this mode, the user does not require a physical telephone, just a headset that connects to the user’s personal computer or thin client. The voice traffic between the hosted softphone application and the user device is sent over Citrix’s ICA protocol. This mode was the focus of the testing done with XenDesktop and the Avaya softphone clients.

Tested Softphones and Operating System Platforms

The softphones specifically tested by Citrix with XenDesktop 4 were:

  • Avaya one-X Communicator 1.0.0.57

  • Avaya IP Softphone R5

  • Avaya IP Softphone R6

Citrix does not foresee any compatibility issues with other current Avaya softphones (such as, one-X Agent 2.0 R2). For the latest compatibility information, check the Citrix Ready Web site at http://community.citrix.com/citrixready

Memory and CPU Consumption of Avaya Softphones

The memory and CPU consumption of the Avaya softphones were 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 XenDesktop VDA platform in the data center, Citrix recommends using XenDesktop’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 VDA platform 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 to 100 Kbps per call (depending on Network Layer2 overheads). G729 provides good voice quality and has the lower bandwidth requirement of 30 to 40 Kbps per call (depending on Network Layer 2 overheads).

Configuration

XenDesktop configuration guidelines:

  • Citrix generally recommend using Bidirectional Audio (leveraging the XenDesktop audio driver) rather than raw isochronous USB redirection, because this consumes less bandwidth and put less load on the server.
  • Choose the Optimized-for-Speech (Medium quality) audio codec setting rather than the default High Definition setting to minimize bandwidth consumption and latency (encoding time). This codec is ideal for VoIP.
  • On each user device, install the minimum required Citrix 11.2 or 12.0 online plug-in/Receiver 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.
    The 12.0 version of the online plug-in for Windows (Citrix Receiver released March 2010) introduced echo cancellation in the client software.

    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 on a hypervisor, you might need to either allocate two virtual CPUs or disable the Citrix Gateway Protocol (CGP).

    • Obtain XenDesktop 4 VDA Hotfix 2 (or above), which includes an enhancement for network congestion to prevent delay in the audio path (Prior to availability of VDA Update 2, this enhancement is available and included in the following CTX132483 – Hotfix XDE400VDAWX64008 (Version 4.0.5066) - For Citrix XenDesktop 4.0 Virtual Desktop Agent x64 . This enhancement introduces voice energy detection, allowing ambient noise (silent packets) to be discarded. This feature is controlled using a registry key.

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

     

    When installing the Avaya softphone, do not select the IP Softphone for Citrix installation mode, as it is strictly for installation on Citrix XenApp under Terminal Services. Installation on XenDesktop is equivalent to installing on a standard Windows desktop.

    Evaluation of Audio Quality over WAN

    The Citrix Test team evaluated audio quality under a variety of Wide Area Network conditions using a network simulator. The following results were observed at 5% jitter (E = Excellent; G = Good; F = Fair):

    Packet Loss (%)

    Network Latency (roundtrip, i.e. ping time)

    0 ms

    50 ms

    100 ms

    150 ms

    200 ms

    0.0

    E

    E

    E

    E

    E

    0.5

    E

    E

    E

    E

    E

    1.0

    E

    E

    E

    E

    G

    1.5

    G

    G

    G

    G

    F

    2.0

    G

    G

    G

    G

    F

    (Measured at 5% jitter with Optimized-for-Speech codec setting)

    The generally recommended packet loss metric to support VoIP is 0.5% or less.

    Impact of High Jitter

    Packet Loss (%)

    Network Latency (roundtrip [ping time])

    0 ms

    50 ms

    100 ms

    150 ms

    200 ms

    0.0

    E

    E

    F

    P

    P

    0.5

    E

    E

    F

    P

    P

    1.0

    E

    E

    F

    P

    P

    1.5

    E

    E

    F

    P

    P

    2.0

    E

    E

    F

    P

    P

    (Results with jitter at 10% of one-way latency. E = Excellent; G = Good; F = Fair, P = Poor)

    Note: The XenDesktop 4 release does not include jitter buffering. High levels of VoIP jitter over the ICA connection from the user to the VDA platform can result in bad call quality or delay in the conversation.

    Additional Resources

    CTX133024 – Delivering Softphones with XenDesktop

    Issue/Introduction

    This article provides configuration guidelines for delivering Avaya softphones on XenDesktop under the VDI model, and provides results from testing performed by Citrix.
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