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Mobile apps have “PING” for breakfast!

Why operators should measure what the customer sees…

Mobile operators are under pressure to offer super-responsive connectivity with low latency: whether it’s for your favourite multi-player game or whether it’s to ensure that zoom call with your boss runs smoothly.

The problem is, there’s quite a gap between the network latency measured with ICMP (via the “ping” command) and the effective latency experienced by an application which never actually uses ICMP. 

ICMP (specified in RFC 792) operates in a layer just above IP, meaning its messages are carried as IP payload.  ICMP is often used to signal errors between hosts, but in addition to the error messages, it defines one of the Internet’s most famous applications: ping. Most TCP/IP implementations support Ping directly in the operating system thereby avoiding the time taken to decapsulate the transport-level segment, identify the correct socket and send the message on to the application process.

These steps are necessary when interacting with applications such as HTTP (the application used to request a web page) or HTTPs (when performing a secured transaction). These applications and others, such as FTP, DNS or SMTP also use either TCP or UDP as a transport layer protocol which ICMP does not.

As wireless low-latency specialists, we make sure that our real-time latency tracking tool addresses these issues by performing different types of measurement campaigns. First, we do actively measure network latency using ICMP (knowing that ICMP may be routed differently than payload traffic). Hence, we also use other protocols like TWAMP and PTPd to get the most accurate results: important when we are measuring in milliseconds!

Second, we aim to measure the latency as the application sees it.  We use an intelligent mix of the HTTP/HTTPS/TCP/UDP protocols to mimic the application’s behaviour. We measure multiple times  per second and perform statistical analysis to generate an aggregated view. We accumulate these results to  perform advanced analysis like anomaly and trend detection – all in near real-time – and send notifications back to the application (and to OSS/NMS systems) if something is wrong.  To complement this, we also perform real-time measurements of the bandwidth and reliability (using packet loss count) in addition to taking snapshots of the path(s) taken by the data. This allows us to perform route cause analyses whenever the latency results are outside accepted boundaries for a prolonged period.

The results of both these campaigns can then be displayed and used for comparison and evaluation.

The diagram below shows a snapshot of LatenceTech’s Compact Dashboard presenting latency results for a mobile gaming application running on the  Encqor 5G (NSA) network using a MmWave RAN site and a Mobile EDGE platform in Montréal Canada in early 2022.

Real-time dashboard showing live low-latency results from MMwave measurements

Here we can see the difference between network level latency (10.6ms) and application level (17.2ms) latency by means of results which were aggregated over a 5- minute period. The 38% difference is significant! Knowing the network latency is great but having factual and continuous knowledge about application-level latency is a prerequisite to deploying a time-critical mobile applications.  

Below is another dashboard example, showing results from a low frequency band  and testing the latency from the device to server residing, this time, on the cloud.

Real-time dashboard showing live low-latency results from low-band measurements

We can see here the impact of the lower frequencies and longer distances to data processing, underlining the important role that MmWave and Edge computing will have in low-latency communications.

Time-sensitive mobile applications will require reliable, sustained low-latency connectivity which is best served by 5G technology.  But 5G alone will not be enough to deliver the service users need.  Tools to perform continuous tracking of  quality of service, and in particular network and application latency levels will be central to providing a reliable, high-performance service. Being able to rely on this quality of service means that new applications can be developed, and these will generate new economic benefits and value to end customers.  With the right network performance, think of all the innovate services that will be developed…

Short list of time critical application requiring ultra-low latency connectivity

When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it… your knowledge is of a meager and unsatisfactory kind.” –Lord Kelvin

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