Telepresence Infrastructure Testing

Telepresence is the ability to conduct live meetings and simulate the attendee’s senses, by delivering high quality video and audio over an IP network.  To ensure you end up with the experience you want, each session is reliant on zero media faults and zero network interruptions.

To conduct a Telepresence meeting you connect multiple individual end-points to a central meeting management server. The server manages many aspects of the call including the video and audio distribution.  However, prior to commencing a call the unique remote end-points need to authenticate usually through a SIP registration server. Other components in a Telepresence deployment include meeting schedulers.

Testing your telepresence equipment is essential to ensure that you end up with the experience you want. Testing can be complex,  as a critical feature to testing Telepresence, is the ability to measure performance on each and every one of the 4 unique media flows (video  in – out and audio in – out) associated with each and every emulated test or end-point.   You may also want to inject traffic into the system so that you can disrupt the meeting, further testing the security and reliability of the deployment.


Sample Telepresence Test Scenarios

  • Live Meeting Performance:
    • Emulate and measure performance of the Telepresence meeting’s video and audio with stateful emulated end-points. Test for interoperability issues with end-points using different video and audio codecs.
  • Network Capacity Testing:
    • Examine network capacity with a small number and/or many emulated Telepresence end-points, threshold test acceptable packet loss.
    • Create real world scenarios with mixed application traffic loads. Examine the impact on each and every emulated Telepresence end-point’s video and audio quality.
  • Telepresence Meeting Scalability:
    • Test the registration server capacity to handle many registrations. Determine if a meeting manager server functionality handles over subscriptions to a meeting correctly. Emulate and analyze secure media sessions such as SRTP.

diversifEye Per Flow test platform allows you measure the characteristics on each and every flow using the following test scenario’s.

  • Stateful: Test end-points must communicate with 3rd party servers
  • TCP/UDP Aware: Capable of negotiating network control signals and requests
  • SIP Aware: Respond to SIP protocol requests
  • Application Aware: Test end-points should receive and transmit video and audio i.e. (4 x media flows)
  • Per flow Aware: Measure performance on each of the associated voice and video flows
  • Codec Independent: Test end-points can use a number of different codecs
  • Multiple Clients: The number of test points needs to be scalable

Measuring UC/Video Quality with Network Observer


If you’re implementing videoconferencing, it’s important to know what metrics to monitor to ensure high quality videoconference calls. First, let’s look at the key metrics for managing unified communications apps.

Mean Opinion Score (MOS): Starting with a theoretical perfect score of 5 (excellent), impairment factors such as codec, delay, jitter, and packet loss are used to calculate how a typical user would rate voice quality.

QoS: helps verify that precedence settings are the same for all components of the call or videoconference

Packet loss: the percentage of packets that did not reach their destination. Consult the vendor to understand maximum packet loss the solution can sustain before quality is impacted.

Jitter: measures the variability of delay in packet arrival times

Delay: The amount of time it takes a packet to reach its destination. Whenever packets travel a network, some delay is inevitable. Consult the vendor for maximum delay allowed before call quality is impacted.

Next, let’s explore where you’d find these metrics in Observer.

From the main Observer screen, open the capture containing the relevant conversation, and click the Expert Analysis tab at the bottom of the screen. Select the VoIP Events icon on the left side of the screen. VoIP Events provides multiple ways to analyze conversations in aggregate or on a per-call basis. Let’s explore the tabs within VoIP Events.

VoIP Summary: provides key metric averages for all conversations contained in the capture

Calls Tab: shows each video or VoIP conversation for more granular investigation. Right-click in the column of any metric you do not understand and select Expert Explanation for a definition.

RTP/PTCP Graph: graphs jitter and lost packets over the time of a call

Expert VoIP Settings: configures metrics, graphs, and alarms within VoIP Events


With a basic understanding of key metrics and the technical specifications from your videoconferencing solution, you can set thresholds and alarms for supported codecs in Observer to notify you of potential issues before they impact the user.

Choosing the Right Videoconferencing Technology

Network Instruments observerWith the development of more affordable and robust videoconferencing solutions, many organizations are evaluating this technology as a way to increase project collaboration and reduce travel costs. But how do you decide which videoconference technology is right for you?

Network Instruments spoke with video expert, Dr. Phil Hippensteel, Assistant Professor of Information Systems at Penn State Harrisburg, to understand the types of videoconferencing technologies, the benefits of each, and network considerations.

Where to Begin
Start with this question: What type of endpoint will the conference attendees be using? (Or where will the conference attendees be sitting?) The answer will either be a dedicated conference room or the users’ desktops.

PC videoconference: These solutions allow users to videoconference directly from their desktops via webcam, microphone, and software client.

Dedicated videoconference room: These solutions provide all required components packaged into a single appliance, usually a console with a high quality remote controlled video camera.

Telepresence systems: These higher-end videoconferencing systems are typically employed by large corporate offices. Telepresence solutions incorporate state-of-the-art room designs and acoustics, video cameras, displays, and audio systems combined with high capacity bandwidth transmissions.

The following matrix will help you evaluate technologies based upon your organization’s conferencing needs, project budget, and network environment.

Comparative Qualities PC Videoconference Videoconference Room Telepresence System
Initial Costs Webcam and software client: $25-$121 per desktopClient/Server: $2000-$50,000 per server $10,000-$50,000 per room $150,000-$500,000 per room
Equipment Webcam, software client, and potentially a server Dedicated room, remote controlled video camera, software or hardware console State-of-the-art room acoustics, high-definition video and audio systems, multiple video cameras and displays, and integrated lighting
Network Considerations Individual sessions consume low bandwidthMany concurrent sessions eat bandwidthMore tolerant of latency and dropped packetsTypically relies on Internet as backbone

Impact of desktop video on WAN tends to be underestimated

VLAN typically required to separate trafficAcceptable packet loss range: 0.1%-2%Ideally requires QoS prioritizationLatency should be less than 300 ms round trip between endpoints VLAN required to separate trafficRequires significant, dedicated bandwidthRequires QoS prioritizationCan require audit of room and network by vendor
Primary Benefits Desktop convenienceGreat for remote locations and employeesLess effort to deploy per PC Higher quality meeting experienceMultiple locations communicate simultaneously True “in person virtual meeting room”
Video Codecs Primarily H.323 and
H.264 SVC
H.323, H.264 SVC, and proprietary codes Many proprietary codecs
Primary Vendors RADVISION, Vidyo, Polycom Cisco, Polycom, Vidyo Cisco, Polycom

Use this matrix as a starting point for understanding the decisions you’ll need to make when evaluating any solution. For more in-depth information on technologies, critical network preparations, and costs of videoconferencing, check out the following resources:

Videoconference codec primer
Videoconferencing tutorial
Desktop conferencing and WAN performance
Understanding telepresence basics