Telecom Infrastructure, Voice AI & the Art of Systems That Cannot Fail
"At 2:47 AM on a Tuesday, I was staring at a PCAP that wouldn't give me the answer. The call flow looked clean in the SBC logs. The CDRs showed answered calls. The business reported zero traffic.
After three hours I found it: a codec mismatch introduced during a migration window that nobody had tested against the carrier's actual interconnect. The fix took eleven minutes. The investigation took the rest of the night.
I have been writing things down like that for 13 years. This book is the organized version of those notes."
— K.K. Upadhayay
Symptom: A carrier platform reported $47,000 USD in fraudulent international long-distance charges over 72 hours before the billing team flagged the anomaly.
Dead Ends: The SBC had no real-time visibility. CDR anomaly alerts had not fired. Engineers had no indication anything was wrong.
Root Cause: No INVITE rate limiting on the access-facing interface. An attacker with stolen credentials generated 800 INVITEs/minute to premium-rate numbers. CDR threshold set for previous year's lower traffic volumes — never updated. Both controls were technically compliant. The policy was wrong.
Lesson: Security thresholds must be reviewed when traffic volumes change. A correct threshold at 50,000 calls/day is dangerous at 500,000 calls/day.
10 incidents like this across 10 chapters. Every one is real.
Associate Director, Telecom Operations. 13 years across SIP, SMPP, SBC, PCAP analysis, A2P messaging, NOC operations, Voice AI infrastructure, and IT & Cyber Law.
Every incident in this book is from production. The pattern across all of them is the same: the failure was never where anyone was looking.
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