Back in 2009 (!) I described the theory behind how a mobile network assigns an IPv6 Prefix to a mobile device. 3GPP TS 23.221 and TS 23.060 are a good starting point. 6 years later things have moved from theory to practice so I decided to write another blog entry on the topic, this time with some more details out of traces made in a live network.
Continue reading How To Get an IPv6 Prefix From The LTE Network
Once upon a time a PC was connected with a cable to a network and usually had one IP address. The same applied to smartphones until a couple of years ago. But no more, most smartphones today have more than one IP address at a time, at least some of the time. Any idea how many? Make your own count before reading on.
Continue reading How Many Simultaneous IP Addresses Does Your Mobile Have?
In the past few years a number of hotel chains have experimented with Wifi De-associaten attacks to force venue guests off their own Wifi access points. Fortunately the FCC has responded quite sharply and so I haven’t seen further reports about such behavior in the wild. FCC rulings are good, countermeasures are even better. So far I haven’t seen them “in the wild” which was a bit disappointing. Up until now.
Continue reading First Wifi Access Point With PMF Frames Sighted
I’m probably one of the few people on this planet who appreciates and uses IPv6 both over my DSL connection at home and also over my cellular connection. Unfortunately there is one thing missing on the mobile side: Unrestricted incoming IPv6 access.
Continue reading IoT Needs Bi-Directional IPv6 In Mobile Networks
In the previous blog post on VoLTE I discussed how speech codecs are negotiated during connection establishment. VoLTE uses the AMR and WB-AMR codecs that are adaptive and can encode the voice stream in several data rates and qualities. In the case of WB-AMR, voice streams can be sent with data rates between 6.6 and 23.65 kbit/s. In practice, many networks limit the codec rate to 12.65 kbit/s in the case of WB-AMR and to 12.2 kbit/s for the narrowband AMR codec. Let’s have a closer look how that is done in practice.
Continue reading VoLTE – Some Thoughts On Bandwidth Negotiation
When somebody asks me which book to read to really understand how a computer works I point him or her to the must read book on the topic ‘But How Do It Know‘. If after reading they come back and ask how such a computer actually ends up in chips here are my next suggestions for them:
Quite high on my list of things to do and get into when I have a bit of time are quadcopters. Well, actually that topic is on my list for years now but there’s always something else to do. Anyway today I came across a Quadcopter project with LTE connectivity for control. Cool idea, have a look here.
Speaking of quadcopters, another project that is on that wishlist of mine is the Crazyflie. Everything is open in this project, so it has a special appeal to me. That quadcopter might be a bit too small for LTE connectivity, however.
In the good old fixed line SIP world, the originator of a speech call told the other side which speech codecs it supported. The other side then picked a suitable codec and informed the originator about the choice. That was it and things were ready to go. In VoLTE, you might have guessed, it’s not quite as simple. Today, codecs are rate adaptive and bandwidth for the data stream can be limited by the mobile network to a value that is lower than the highest data rate of a codec family.
I’m quite advanced in my IPv6 adventures but there has been one thing that has been holding me back so far: The DNS resolver in my DSL router at home refuses to properly return the IPv6 address of my local server. Instead it doesn’t respond at all to this request. As a consequence my web browser waits for 10 seconds before it gives up and then uses the IPv4 address of the server instead that was returned just fine. This had me baffled for a long time because all other DNS resolvers returned the IPv6 address just fine. Now it turned out that this is not a bug at all but a feature.
Continue reading My IPv6 DNS AAAA-Resolver Bug Is A Feature – With A Fix