A small brain dump of topics that currently fascinate me. These are mostly pointers and maybe it is interesting to follow it. Books/Reading: My kobo ebook reader has the Site Reliability Engineering book and I am now mostly done. It is kind of a revelation and explains my interest to write code but also to operate infrastructure (like struggling with ruby, rmagick, nginx…). I am interested in backends since… well ever. The first time I noticed it when we talked…
Going from 2G/3G requires to learn a new set of abbreviations. The network is referred to as IP Multimedia Subsystem (IMS) and the HLR becomes Home subscriber server (HSS). ITU ASN1 to define the RPCs (request, response, potential errors), message structure and encoding in 2G/3G is replaced with a set of IETF RFCs. From my point of view names of messages, names of attributes change but the basic broken trust model remains. Having worked on probably the best ASN1/TCAP/MAP stack…
The classic question in IT is to buy something existing or to build it from scratch. When wanting to buy an off the shelves HLR (that actually works) in most cases the customer will end up in a vendor lock-in: The vendor might enforce to run on a hardware sold by your vendor. This might just be a dell box with a custom front, or really custom hardware in a custom chasis or even requiring you to put an entire…
When creating the MGCP and SIP implementation I didn’t want to do string splitting/scanning myself but follow the grammar of the two RFCs. I decided to use the PetitParser framework. PetitParser is a parsing combinator. Which mostly mean you create small parsers and combine them with things like a sequence (parse this, than that and expect the input to be fully consumed). For a long time this approach was just okay but I recently started to use the code on…
We are building a gsmSCF in Pharo. Normally I would use MongoDB and Voyage to store my objects but as a gsmSCF deals with the balance of users I wanted to use something that supports transactions. Looking at the SQL support in Pharo. I found SqueakDBX, DBXTalk, native Postgres drivers but all of them lacked prepared statement support and one really doesn’t want to format queries by hand. This is when I decided to port GNU Smalltalks DBI framework and…
Once up on a time I was sitting in a cold hall at the Barcelona exhibition ground, a power outage has taken down several DVB-H platforms (racks consisting of servers, streamers, RF equipment…) and once power was restored red LEDs were blinking, systems not coming up automatically, hordes of engineers trying to boot the right kernel, trying to remember the multicast routes they had typed in by hand, chaos, hectic. It was interesting to witness that as we could lay…
I ended up needing to configure FreeSWITCH to use a Sangoma ISDN card. At first we were foolish and used the setup script to install libraries into our system. Cleaning up It took dpkg -S and manual filtering to clean this mess. On a debian system there are files in /usr/ that do not belong to packages, these can be links to /etc/alternatives, or in case of python be bytecode files (*.pyc). Second attempt with building packages The next attempt…
Intro The last couple of days, to some degree weeks I was implementing a SIP stack for GNU Smalltalk to be used in my Smalltalk GSM project. The first time I encountered SIP was around 2001 when we were excited to run a SIP Phone on our Linux powered iPAQs (Linphone on Opie). For Smalltalk I started with looking at SipStack by Frank Shearar (who was very responsive to questions regarding his code and SIP in general). The main problem…
I started to play with smalltalk somewhere in February, more specific with the GNU Smalltalk implementation. Like it is with any new language and class library it takes a while to get productive and it took me until somewhere the last month where I finally started to do GSM handling in Smalltalk and thanks to laf0rge the code is now in a public repository and hosted along the other Osmocom projects. You can see all the subprojects over here. So…