When I recently had problems keeping a UDP session alive over a NAT router I found out that my Raspberry Pi acting as the NAT router only keeps port mapping for the UDP session for 3 minutes. If there is no traffic during that time the mapping is discarded and all incoming packets afterward will … Continue reading UDP NAT Timeouts and How To Change Them On Linux
I'm getting quite a number of questions lately on what Network Function Virtualization (NFV) and Software-Defined Networking (SDN) are all about. Whenever I try to give an elevator pitch style answer, however, I can often see that lots of question marks remain. I guess the problem is that people who haven't seen virtualization in practice so far have difficulties imagining the concept. So I've decided to explain NFV and SDN from a different angle, starting with virtualization on the desktop or notebook PC, i.e. at home, which is what most people can try out themselves, imagine or at least relate to. Once the concept of virtualization at home becomes clear, the next step is to have a look why and how virtualization is used in data centers in the cloud today. From here it's only a tiny step to NFV. And finally, I'll explain how SDN fits into the picture. This is probably one of the longest posts I ever had, so bring some time. As part of the exercise, I'll cover things like Software-Defined Networks (SDNs), Network Function Virtualization (NFV), OpenStack, OpenFlow, the OpenNetwork Foundation, etc. (Note: Should you have noticed that the order of the terms in the last sentence does not make sense at all, you probably know already everything that I'm going to talk about in this post).
In my post from a couple of day ago on how to home-cloud-enable everyone, one of the important building blocks is an SSH tunnel from a server with a public IP address to the Owncloud server at home, i.e. not accessible directly from the Internet. I didn’t go into the details of how this works, … Continue reading Using SSH to Tunnel Packets Back To The Homecloud
Believe it or not but I am still using an 802.11g access point at home because the 802.11n access point that is part of my high end VDSL router at home is just crap. In most cases the 20 Mbit/s I can get out of it through two walls is good enough for my purposes. … Continue reading Some Wi-Fi 802.11n and 802.11ac speeds in practice
Now that I know a couple of ways how to build a clock generator I've moved on to the next step and have started looking into what kind of RAM I want to use for my Do It Yourself CPU (DIY-CPU). Here's the story of how that went: As it's an experimental system I only … Continue reading The DIY-CPU Project – Experimenting With RAM Using a Raspberry Pi
About twice a year there are rumors in the German mobile industry that O2 and E-Plus are about to merge one way or other. This time, it's more than a rumor as O2 has actually made an official offer of around 5 billion Euros in cash + 17% of O2 stock for Dutch telecom incumbent … Continue reading O2 Germany and E-Plus To Merge (Yet Again)? Some Thoughts on Benefits and Tech Background
Antennas and base station sites, they can be seen everywhere these days but it's pretty difficult to see how they change over time. When I recently came home and looked out the window I could at first not exactly say what it was but I had the impression that something had changed at the antenna … Continue reading How Antennas Change Over Time
And here's the post I hinted at earlier on cellular network coverage in the popular district I've been reporting about with an antenna on everything that does not move. Think I exaggerate? Then have a look at the screenshot on the left, produced with output from my Cell Logger App. Each red dot is the … Continue reading Seoul: A Cell Every 50 Meters
Once you have more than just your notebook connected as part of your local wireless network at home to ultimately reach the Internet, there is of course the need and desire to exchange data between the devices. Sure, there are cloud services, but for those who like to keep their files and private data close … Continue reading File Exchange with Android Devices in the Home Network: SMB
As reported in the press and here yesterday, it's been 20 years since the first GSM call was made in a commercial network. July 1st 1991, what's behind the date? According to this book on the history of GSM in Germany, published in 1994 (!), the date was set already in the mid 1980's as … Continue reading Some background info on the First GSM Call on July 1st 1991