GoIP: Running IP Telephony for 100,000 Customers
As telephony specialist at Debitel Danmark, I ran GoIP - one of Denmark's largest IP telephony providers. 100,000+ private customers, Asterisk, and a migration to Centile that could not fail.
I joined Debitel Danmark as telephony specialist in November 2006. My responsibility was GoIP, one of Denmark's largest IP telephony providers at the time, serving over 100,000 private customers and many large business clients.
Inheriting a live system
The platform ran on Asterisk with a custom PHP layer handling provisioning, CDR (Call Detail Records), and billing. There was no handover from the previous developers. I inherited a production system serving 100,000+ paying customers with no documentation and no one to ask. Every discovery was made by reading code and tracing call flows through the live system.
The migration
I initiated a migration from the Asterisk/PHP platform to Centile, a more robust Java-based telephony platform. This wasn't a greenfield project. Every customer's phone had to keep working during the migration. Call routing between old and new systems had to be seamless. CDR data had to remain accurate because it drove billing. One mistake meant either dropped calls or wrong invoices for 100,000 people.
The infrastructure work included replacing Asterisk gateways with ISDN30 gateways and transitioning to pure IP telephony through IP-to-ISDN30 converters. I also built virtual PBXes and dynamic IVR call flows with database-driven routing and web-based administration.
The internal IVR
I redesigned the internal IVR system for customer self-service: theft blocking, balance checking, account management. The kind of thing you interact with when you call your phone company and press 1 for this, 2 for that. Except this one had to handle the load of 100,000 customers and route correctly every single time.
What happened to GoIP
Debitel was acquired by Telia in 2007 and eventually rebranded to CallMe in 2008. Telia later sold its Danish operations, including CallMe, to Norlys in 2024 for DKK 6.25 billion. The platform I helped build and migrate became part of a multi-billion kroner telecom operation.
I left in June 2008 to join Fest Data, where I would later co-found Talk IP with Thomas Fest.