Category: Uncategorized

Ubuntu visualizes current and previous power consumption and recharge behavior in a couple of nice graphs as shown in the screenshots above and below. When I have screen brightness quite high but not much else is going on, my notebook draws around 12-13 Watts of power and my battery lasts around 4 hours. Turning up brightness, running a virtual machine or two and streaming a video from Youtube and power consumption is obviously significantly higher. Sometimes it would be nice, however, to not only see a graph but to get a reading of how much power my notebook takes at any point in time. Fortunately there’s a command for that.

Continue reading Linux Command To Get The Notebook’s Current Power Consumption

Most services on the Internet make use of a single TCP or UDP connection. The client opens a TCP connection from a random port to a well known port on the server (e.g. port 443 for HTTPS) and performs authentication and establishment of an encrypted session in that connection. Simple! In VoLTE, however, things are much more complicated as there are three streams used in practice and TCP and UDP can even be mixed. Continue reading VoLTE – Some Thoughts On Port Usage

Back in September last year I waded through the legislative proposal to phase out surcharges in the EU in two steps. The first step foreseen for April 2016 is coming closer and my mobile network operator has informed me in my latest invoice of the coming changes for this and also for the next step in mid-June 2017. This makes for interesting reading as this is the first time I have seen something about this topic other than press articles and EU legislative proposals.

Continue reading EU Roaming Fees Phase Out News

Recently I’ve upgraded my notebook to 16 GB of RAM to enable me to run more virtual machines in parallel and to prepare for a 32 to 64-bit OS upgrade. Unfortunately I discovered after a week or so that my disk write speed was deteriorating significantly over time. The more I looked the worse it seemed to get. What followed was a 7 day and night chase and 15+ terabytes of data transfers until I finally found the reason and a workaround.

Continue reading 7 Days, 15 Terabytes and 1 Kernel Bug Later

When I first came across the VoLTE service registration process I was a bit baffled why it is split in two procedures. The reason for my confusion was that in the circuit switched world there is only one process, a “location update”. Once done that’s it and the mobile can go back to sleep. In VoLTE there is a registration procedure and a subscription procedure that follows. Here’s why:

Continue reading VoLTE – Some Thoughts About Register vs. Subscribe

I’ve written about having IPv6 access both at home and on my mobile devices anywhere now a number of times before but actually, it’s not as universal as that after all because there is one loophole…

Continue reading IPv6 When Roaming

In recent releases, developers of the seminal open source ‘Conversations‘ Jabber Android app have added two really cool new features: Group Chat encryption and the ability to edit the last message that was sent.

Continue reading New Features In The ‘Conversations’ Instant Messenger

In a previous post I’ve explored the steps that are necessary to increase Owncloud’s file size limit to 3GB and checked that such large files can still be downloaded over a ‘slow’ 10 Mbit/s VDSL uplink when each gigabyte takes around 20 minutes to be transferred. In my initial use case I uploaded my large files locally over a high speed link so I didn’t encounter any timeouts. But what if large files are downloaded over slower links, is there a timeout in Apache or Owncloud that aborts the process after some time?

Continue reading Is There An Upload Time Limit In Owncloud?

Today the Let’s Encrypt initiative has announced that only 3 months after opening to the public, 1 million certificates for encrypting web traffic have been issued. 90% of the sites for which certificates have been requested did not encrypt their traffic before. In other words Let’s Encrypt’s mission to foster adoption of HTTPS by making it simple to get a certificate is working very well indeed!

This, by the way, also applies to this web site as I also use a Let’s Encrypt SSL certificate! I’ve previously hosted this blog at Typepad and one of the many reasons to leave was to get my site’s data traffic properly encrypted during transport. One nice side effect of this is that I no longer need to establish a VPN tunnel to write posts during my daily commute as everything is encrypted now.

Congratulations to Let’s Encrypt!

In the good old fixed line SIP world things are straight forward when a SIP user wants to call someone: INVITE, TRYING, RINGING, OK and you are there. In the VoLTE world things are a bit more complicated as the service tries to replicate the circuit switched telephony service. Here, a media stream can already sent before the receiving party answers the call so the caller hears an alerting (ringing) tone or even music in some cases. This is what’s known as early media in VoLTE and there are two ways how this is done in practice:

Continue reading VoLTE – Some Thoughts On Early-Media