What is Jitter and should we care about it?
This blog is Part 2 of a 3 part blog and concentrates on jitter (variable latency). Part 1 dealt with distance, latencies and orbits and subsequent parts will discuss the effect of atmospheric conditions and choice of wavebands.
First, it’s worth noting that while the term jitter is used by network specialists and certain application performance engineers, it isn’t really a network term at all - it’s a communication engineer’s term - and essentially refers to the difference between when a timing signal should have been received and when it was actually received.
So, in an ideal world, if you transmit a signal (down a wire or as a wave) 1 Million times a second (1Mhz) at even spacing then that’s what you expect to receive: 1 pulse at exactly every microsecond (millionth of a second). That’s not to say that all the pulses might not all be delayed (perhaps due to distance), but the expectation is that they are delayed by the same amount and so the jitter is 0. Unfortunately real life is not like that and signals can arrive relatively too early, or too late. This is jitter.
Why is satellite latency so high? (and it's not all to do with distance)
This blog is Part 1 of a 3-part blog and concentrates on high latency, the subsequent parts will discuss jitter, the effect of atmospheric conditions and choice of wavebands.
If we want to our applications to be available globally we have to bear in mind that there are lots of places on the Earth where wired and mobile (or other wireless communications) are not available, for example:
- In remote places (some less remote than you might think!)
- On aircraft flying over oceans or remote locations
- On ships distant from the shore
- In certain military situations
- Certain emergency services requirements, i.e. first responder
Just about the only reasonable way to serve these locations is to use satellite communications, provided you have a view of the sky that is. Due to their height satellites have a very large coverage (up to slightly less that 50% of the Earth’s surface you might think, but more on that in a moment).
Unsurprisingly, there's a lot of buzz around 5G at this week’s Mobile World Congress trade show in Barcelona, Spain. But believe me, the 5G wireless network isn't going to be the panacea that many expect it to be.
Bob O’Donnell of TECHnalysis wrote an great report "The Messy Path to 5G" detailing some of issues that are impacting deployment of 5G, but one thing is for certain - the need to properly test app performance prior to their launch isn't going to go away due to the abundance of bandwidth.
There’s a cycle in technology where people figure out that you can make money out of something and so everyone jumps on the bandwagon. You know .com, e-commerce (in fact e-everything), SaaS (and its forerunner ASP), the Cloud, Big Data... Though the bandwagons come and go, some practical technologies usually emerge as successful and viable and remain long after the bandwagon has disappeared out of sight. Currently one of those bandwagons is IoT (the Internet of Things).
It’s that time of year when we see a whole raft of articles telling you the “Top 10” things you must do next year to succeed. One thing that will probably be missing, although it really shouldn’t be, is incorporating effective operational testing into your software development & testing cycle. Believe me, operational testing it is important -it just isn’t getting the attention it deserves.
So, what is Operational Testing and why is it Important?
It was great to attend The National Software Testing Conference held in London recently, both as an exhibitor and a speaker. I really love this type of event as they provide a great opportunity to talk to professionals, in this case software test professionals, who are “at the coalface”.
During conversations with several delegates who visited our (iTrinegy) stand I was encouraged to hear that they understood the concept (and saw the value and need) of including verifying application behaviour over networks as part of their test regime. A few years back, if you asked the question “So how are you checking that your application will work over in a production network?” It would not have been surprising to get a reply along the lines of “Oh, that’s not part of my remit, I leave that to the operations team/network team”.
What was your first job in IT?
I started out in British Telecom’s Research and Development department. They needed a system to help manage the transition of systems and processes and my job was to program various modules.
How did you first get involved with Network Emulation & Profiling?
Among the many things BT was doing at the time was a project to look at the quality of VoIP systems, to see if they could be a viable alternative to fixed lines. The problem they had was how to replicate the network conditions in order to perform the tests. This ended up on my desk, and that’s what got me thinking about the potential for helping all kinds of businesses understand the impact of networks on their applications.
What do you find most satisfying about what you do?
When customers recognize the value from testing their products and systems more effectively because of our Network Emulation and Profiling technology. I also get great satisfaction when I assist customers personally on implementing very complex virtual test network environments.
It is estimated that there are already 14 billion objects connected to the Internet, so that is currently more than 2 devices per man, woman and child in the world today. Industry analysts are projecting that this could rise to anywhere from 20 billion devices to 100 billion by 2020 and if IoT really takes off in a big way with more connected cars, more wearable tech (both for recreational and healthcare monitoring purposes), and more connected buildings etc., it is easy to see how such growth is going to be achieved. Some may suggest that even 100 billion connected devices is a bit on the conservative side.
In most cases, these devices will act as sensors and, individually, only demand relatively small amounts of network bandwidth to communicate small amounts of data. However, when you scale this up to many millions or billions of connected devices, the demand on the network becomes huge.
At iTrinegy we used to build Network Emulators, and we still do. But that sounds like something that a boffin scientist might use, not a regular IT person. So it’s worth taking a step back…
… with the Network now being an integral part of almost every app(lication) - btw somehow we’ve got into saying “app” on mobiles and tablets and “application” on everything else, so I’m going to use “app(lication)” for both/either - what people need is a way of make sure (sometimes called testing!) their app(lication) works in the final network.
And, that’s not just for today’s applications: IoT devices, connected cars and smart metering are all going to depend on the network.
So what we need, to make sure it’s all going to work properly when we put it “out there”, is a network that behaves like the real network, but that you can control.
These days choosing a coffee shop is not that straightforward. Is it about the quality of the coffee? or the food, maybe? Or maybe, it’s about the quality of the internet connection...
It’s one of those days where I have back to back client meetings when I get a call to say that the next meeting is postponed. Phew, time for some lunch so I head for the nearest coffee shop for my usual americano and of course time to catch-up up on some emails as the iPhone hadn’t stopped buzzing all morning.
The first one I come across is a well known chain just at the top of Long Acre near to Covent Garden. Perfect, meets my criteria for good coffee, plenty of available seats and of course free WiFi. I order my small americano which comes in one of those tall glasses so I have to precariously hold it in one hand whilst carrying my briefcase in the other. No mean feat but I’ve mastered this over many years of killing time in coffee shops! I head to the front of the eatery where there is plenty of available seating compared to the back. Great, arrived safely and without spilling a drop of coffee. I boot-up the laptop and connect to the WiFi. All good so far and Outlook starts to download the emails but it’s very slow.