Author: Martin

A couple of days ago I suddenly had strange intermittent problems to connect to my services at home. It worked one minute and the servers were not found the next. At first I thought it must be a DSL problem but I quickly figured out that this was not the case at all when I checked the DNS resolution for my domains. Here’s the response of two DNS queries which were one minute apart.

$ ping www.some-domain.com
PING www.some-domain.com (217.253.68.195) 56(84) bytes of data.
[...]
$ ping www.some-domain.com
PING www.some-domain.com (79.216.56.147) 56(84) bytes of data.

What should have been the same IP address suddenly oscillated between two entirely different IP addresses. What’s more is that this happened for several of my domain names via the local DNS resolvers, over Google’s 8.8.8.8 DNS server and also over two VPN tunnels over which yet other DNS resolvers were used.

Continue reading DNS Pogo Oscillations

A couple of weeks ago, the German Telecoms regulator (Bundesnetzagentur) published their annual report for 2017. I was a bit surprised that I last wrote about such a report in 2015 so it was really time for a status update and a then-and-now comparison.

Continue reading German Telecoms Regulator Report For 2017

Once upon a time, Skype was THE voice and video calling platform for me. It was independent, decentralized and offered end-to-end encryption. But that was a long time ago, today it’s centralized, more closed source than ever, and encryption seems to be rather optional. But on PCs there was little else that was usable and universal, perhaps until now. A few days ago I started to test Nextcloud Talk, that, despite its name is a full blown Voice and Video Conferencing and Calling Solution.

Continue reading Nextcloud Talk – Voice and Video Calling – First Impressions

Two years ago, I moved this blog from Typepad, a blog hosting service I used for over a decade but who didn’t deliver value for money anymore to a web hosting provider and WordPress as a publishing platform. Now, it was time to move once again, for different reasons, however, from a web hoster to a virtual machine.

Continue reading Moving The Blog To A Virtual Machine

Over the past few weeks, I’ve been using Nextcloud Talk quite a bit. While I’m very happy with it in general, I have actually found two scenarios in which the standard setup is not able to establish a connection between the two (or more) parties of a call: In roaming scenarios with my mobile network operator of choice and when I use Nextcloud Talk in the web browser on the PC at work behind the firewall. But there is a fix, at least for one of them.

Continue reading A TURN Server for Nextcloud Talk

It’s been a while since I talked about LTE based technologies for the Internet of Things (IoT) or Machine to Machine (M2M) communication. Slowly but steadily, we are now seeing NB-IoT and CAT-M1 technology deployed in practice even though I would have thought things would move faster. 3GPP has not slept in the meantime, however, and has continued to evolve both the standards for NB-IoT and also for CAT-M. In this post, I’d like to describe some interesting additions to the CAT-M system that has resulted in specifications for CAT-M2 devices.

Continue reading CAT-M Evolution in 3GPP Rel. 14

One of the nice things of my Fritzbox DSL router is that it draws nice graphs of what is happening on my VDSL line. And one thing I find particularly puzzling in the top graph in the screenshot above is that the signal to noise ratio on the line starts at around 60 db and then quickly decreases down to only 20 db at around 2 MHz. After that it skyrockets again to 60 db and then expectedly degrades again slowly.

Continue reading Why Is My SNR So Bad At 2 MHz?

Back on the history track again, I picked up an electronic copy of Leslie Berlin’s ‘Troublemakers – Silicon Valley’s Coming of Age’ about the early days of Silicon Valley.

I’ve read quite a number of books about the rise of Silicon valley in the past, some on famous people like Steve Jobs but most on much lesser known people that didn’t all necessarily get rich and famous but who nevertheless shaped the industry and the way we live today. ‘Troublemakers’ is a book that again deals with this kind of people and Lesslie has decided to tell the story of a number of them that were not covered in this detail in other books I’ve read on Silicon Valley so far.

Continue reading Book Review – Troublemakers

In many countries, 5G networks will be launched initially in a configuration referred to ‘Non-Standalone Architecture – Option 3’. This means that the mobile device connects to a 4G cell that has a co-located 5G cell which it can then include in the data transfer. This is why ‘option 3’ is also referred to as EN-DC (eUTRAN NR – Dual Connectivity). When I was recently asked how and where a 5G capable mobile devices signal their 5G capabilities to a 4G LTE cell during connection establishment, I could give a rough answer. However, I decided to look up the details in the 3GPP specifications and write them down here as I’m sure this was not the last time the question come up.

Continue reading 5G EN-DC: How Does The UE Signal Its 5G Capabilities?

While I recently had my Tmux moment and have used the program ever since to multiplex many shell sessions in a single window, I have noticed a couple of quircks. When using ssh in tmux to connect to remote servers, some programs such as htop and the nano text editor don’t act correctly when scrolling. Text that should not be visible anymore is still there and the cursor jumps to the middle of the screen instead of to the end. Also, the ‘home’ and ‘end’ keys are not properly mapped so it’s not possible to use these keys in nano to jump to the beginning and end of a line. After a bit of searching on the web, I found a number of tips and tricks which, when used in combination, fix all of this.

Continue reading Tmux, SSH, Nano and Scrolling