As telco regulatory agency in Croatia introduced some news, Croatian operators must be able to make telco interconnections not only with SS7/TDM, but also with SIP. As SIP is more scalable and has other advantages, that was a good call. We needed to deal with a new set of problems, like different SIP implementations, compatibility issues between core softswitches, etc.. Our voice processing cluster was already running and processing traffic, but we needed to make sure everything will work well under excessive load. We were getting ready for one of the biggest TV shows to process all voice calls and text messages. It was also the right moment for couple telcos to test their interconnection and to terminate test calls on our system.
With our high availability cluster, hosted on multiple locations, we were under 'traffic attack'