The Integration Problem That Won't Go Away
Every cloud contact center and voice AI platform eventually hits the same requirement: connect to the Public Switched Telephone Network. That means bridging SIP, the 1990s telecom standard, with WebRTC's browser-native communication.
The CPaaS market grew to $17 billion in 2023 precisely because this integration is harder than it looks. While both protocols use Session Description Protocol for media negotiation, their transport layers are incompatible. SIP expects transactional text-based signaling over UDP/TCP. WebRTC mandates encrypted DTLS-SRTP over WebSockets with ICE for NAT traversal.
Direct interoperability fails because legacy SIP trunks send plain RTP audio that browsers reject. Build this wrong and you spend months recreating transaction state machines.
The Middleware Trade-Off
Python lacks mature SIP stacks. The aiortc library handles WebRTC but doesn't scale to production PSTN volumes. This creates an architectural problem: Python shops building voice AI need external SIP engines.
Drachtio emerged as the pragmatic answer. It's Node.js middleware with a C++ core that handles SIP message parsing while Python services manage business logic via HTTP webhooks or Redis. This "sidecar pattern" separates concerns: Drachtio manages protocol complexity, Flask handles "Which AI agent gets this call?"
The alternative is Kamailio with its KEMI Python interface. It delivers carrier-grade performance at tens of thousands of calls per second. The catch: brutal learning curve and C-like configuration that makes debugging embedded Python crashes difficult.
What Actually Ships
For most implementations, Drachtio provides faster time-to-market at thousands of calls per second. That's sufficient for contact centers and AI voice agents. Kamailio makes sense when you're building carrier-grade infrastructure.
The broader lesson: legacy integration often forces polyglot architectures. The "best" technology stack sometimes means accepting that different problems need different tools. Python's AI capabilities don't eliminate the need for specialized protocol handling.
History suggests companies that ship working PSTN integration win more business than those stuck perfecting single-language purity.