Network Monitoring and Assurance: Visibility and One-Way Delay

The general-purpose network test equipment market is changing, driven by the emergence of 5G, greater need for interoperability testing, and increase in outsourcing, said RCR Wireless news in a recent article, citing research from TechNavio. We would add that rapidly developing changes in network monitoring extend far beyond the realm of traditional test and measurement.

For example, consider the importance of visibility into network performance, and what that actually means: insight that “allows IT to control and optimize the network, along with applications and IT services,” stressed Light Reading in a recent article
Without such visibility, “organizational speed decreases, network problems take longer to resolve and security threats increase,” Light Reading elaborated. A successful strategy to achieve visibility requires considering end-to-end architecture and setting up systems for immediate ROI—and recognizing the unique dynamics of the network itself. 

“Ultimately, one-size does not fit all in terms of visibility architectures,” Light Reading concluded. “You need one that is sized to your network’s specific configuration and needs.”

One-way delay
Another, more specific, aspect to consider: one-way network delay—a topic both RCR Wireless and Light Reading and touched on in articles focused on techniques operators can employ to ensure data gets where it needs to be, when it needs to get there. 

“Delay is proving to be one of the most challenging metrics to manage in advanced wireline and wireless networks,” RCR Wireless said. Yet it is also “a critical component of both end user experience and infrastructure stability, since it can lead to dropped calls, slow browsing and TCP transport protocol performance impacts.”

Light Reading concurred: “lengthy network delays, is an issue bedeviling video content and service providers of all stripes and sizes. Buffering delays of even just a few milliseconds can lead to a poorer customer quality-of-experience (QoE) and much higher rates of video abandonment by subscribers.”

It’s difficult to effectively measure and manage delay, RCR Wireless elaborated, because it “has both fixed and variable components, and it varies over time as network conditions change.” Plus, “In order to properly measure and assure network delay, both one-way and two-way delay must be considered.”
Further, RCR Wireless said, distributed deployment of measurement mechanisms (e.g. GPS at endpoints or in-line devices for clock synchronization) add cost and potential failure points to the network. Instead, operators have come to rely on estimating one-way delay by dividing round-trip delay in two. This is not an accurate way to measure one-way delay, however. 

“The obvious shortcoming with these rough estimates is that they don’t offer any visibility into what might actually be happening on either network path,” Light Reading noted. “As a result, the estimates for one-way delays could be way off because of the asymmetrical nature of most video traffic. Worse yet, these estimates could wind up producing ‘false positives,’ incorrectly indicating no latency problems overall when in fact there may be huge traffic delays occurring in one direction or the other.

Clearly, “service providers must measure and monitor one-way network latency directly and accurately,” regardless of the cost of doing so, Light Reading concluded. (We would add that it does not need to be prohibitively costly, and solutions exist that leverage virtualization and other low-cost technologies to accurately measure one-way delay.)