Category: Uncategorized

7 Days, 15 Terabytes and 1 Kernel Bug Later

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.

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VoLTE – Some Thoughts About Register vs. Subscribe

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:

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Is There An Upload Time Limit In Owncloud?

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?

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1 Million Let’s Encrypt Certificates in 3 Months

Lets-encrypt-logoToday 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!

VoLTE – Some Thoughts On Early-Media

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:

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How Fast Is That SSD In My Notebook?

In theory the 1 terabyte Samsung 840 Evo SSD I use in my notebook has a sustained write performance of well over 400 MB/s according to this fabulous review over at Anandtech. That is two thirds of the theoretical maximum speed the SATA 3 interface can deliver. While this is all nice and well I wondered how fast the SSD would be in combination with my notebook and my typical usage scenarios.

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Pushing My Owncloud File Size To 3 GB

owncloud-logoBy default, Owncloud is configured to handle files up to a size of 512 MB. While that’s probably good enough for most, I do run into this limit rather often. There are instructions how to increase the limit from an Owncloud point of view but when I recently wanted to transfer a 2.7 GB file my setup failed outside of Owncloud. It took me a bit before I found out how to fix it so I thought I put together all things I have now learned about how to configure a system for large file transfers in Owncloud with a number of security and privacy tips thrown in for good measure.

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Time To Switch From Opera to Firefox On Mobile – At Least For Me

firefox-logoEver since I discovered last year that Opera’s web browser on my smartphone was responsible for strange queries to my web server from China to generate a thumbnail image (see ‘When Opera Calls From China‘) it had been at the back of my mind that Opera is not open source and hence I have little trust in it. These days it also seems like Opera is going to be sold to a Chinese consortium which would make it even less attractive for me to continue using it. Time to change to another browser on my Android based devices then. How about Firefox?

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