Video Quality of Experience
Requirements and Considerations for Meaningful Insight
Video is the dominant driver of Internet traffic; depending on the region, video is either already the majority of bandwidth on communications service provider (CSP) networks or it’s destined to become so soon.
While some of this video traffic is “on-deck” (i.e., part of a CSP’s brand or company), the majority of is characterized as being “over-the-top” (OTT); OTT services exist in two forms:
- Services provided by a third-party: examples include Netflix, HBO, Hulu, Amazon, Vimeo, Vevo, Periscope, Twitch, Qello, BBC (iPlayer), Sky TV and other television networks, etc.
- Services provided by the CSP: examples include Bell’s Fibe TV App2 and Comcast’s Xfinity TV App
The popularity of video in general, and OTT video in particular, is responsible for two fundamental shifts in consumer behavior:
- Higher peak bandwidth levels, concentrated in a shorter period of time: Since OTT video is an “on demand” application, it drives traffic when it is viewed; previously, video content was often acquired in bulk and throughout the day via P2P networks and then consumed later. Collectively, subscriber demand for video typically peaks in the range of 8pm to 11pm.
- Heightened subscriber sensitivity to quality: Video is a sensory experience with rapidly changing sights and sounds, so shifts in quality (e.g., stalls, pixelization, compression artifacts, shifts up or down in resolution, changes in frame-rate) are instantly recognized by the viewer.
From the CSP perspective, video is decreasing network efficiency in the macro sense, in that the peak-to-trough ratio is increasing and there’s a large amount of available but unutilized capacity throughout the day. During these high peaks, the network is more prone to congestion; from the viewers’ perspective, congestion can very visibly manifest as degradation in video streaming quality.
Accordingly, CSPs worldwide are looking for solutions that measure and monitor the subscriber quality of experience (QoE) for video; and, in particular, for OTT video.
Video Quality of Experience: Requirements and Considerations for Meaningful Insight
By understanding the complexities associated with measuring video QoE from the end user perspective, CSPs will be in a position to make an informed decision on a suitable solution.
Video QoE in Encrypted Traffic
To be effective for today’s and tomorrow’s Internet, the video QoE solution must work with encrypted video.
Here are three truths about video streaming:
- Someday, practically all video streaming traffic will be encrypted
- Someday soon, most video streaming traffic will be encrypted
- Already, an enormous amount of video streaming traffic is encrypted
As a consequence, solutions that rely on reading video header fields (e.g., container type, codec, resolution, etc.) are already limited in their efficacy and have a very limited remaining operational life.
In addition to obscuring information about the video stream, encryption makes it quite challenging to correlate multiple flows that correspond to the same video. Weak solutions might produce an incorrect QoE score per flow, mistakenly interpreting the flows as separate streams.
Video Quality of Experience Score
Since 2010, Sandvine has provided CSPs with insight into video quality of experience, from the subscriber perspective, with our video QoE score.
Session Awareness and Sampling Frequency
Video sessions are typically long-lived, and an accurate assessment of the viewer’s quality of experience is only possible if the necessary measurements are taken throughout the full duration. However, measurements taken too frequently will incur processing overhead with diminishing returns; measurements taken too infrequently will fail to accurately capture the quality of experience and may fall prey to a sampling error.
Sandvine’s video QoE metric is based on measurements taken every 15 seconds, throughout the entire lifetime of a video session. As a result, there are multiple samples even for short videos, and an accurate assessment can be built of the viewer’s experience for the entire flow.
The measurements for each video are made by the Sandvine Policy Traffic Switch (PTS), and reported as they are made to the Service Delivery Engine (SDE) which performs the calculations to determine the QoE score for the entire flow.
Since both the PTS and SDE are completely session aware, they perform state tracking for a video asset delivered across multiple HTTP GET transactions issued into the same, or different, TCP connections.
Overcoming Routing Asymmetry
For the purposes of measuring video QoE, all routing asymmetry must be resolved – this is the only way in which the full video stream can be seen, which is the only way that quality of experience can be determined with any accuracy.
Sandvine’s solution (as a whole, not just for video quality of experience) completely resolves network asymmetry from the perspective of our packet-processing and policy control applications.
Video Quality of Experience Score
Since 2010, Sandvine has provided CSPs with insight into video QoE that meets all of the requirements to measure quality from the perspective of the end viewer.