You're asking which SIP transport to use with Telnyx and how the transports differ — here's a concise guide. Recommendation • Use SIP_TRANSPORT_TLS (TLS) — it encrypts SIP signaling, offers the best security and reliability, and is the recommended choice for Telnyx integrations. Differences between transports • SIP_TRANSPORT_TLS ◦ Encryption: Yes (TLS over TCP, typically port 5061) ◦ Security: High — protects against eavesdropping and tampering ◦ Firewall traversal: Usually allowed ◦ Recommended: Yes • SIP_TRANSPORT_TCP ◦ Encryption: No ◦ Security: Low (better reliability than UDP but unencrypted) ◦ Firewall traversal: Usually allowed ◦ Recommended: Use only if TLS isn't supported • SIP_TRANSPORT_UDP ◦ Encryption: No ◦ Security: Low ◦ Firewall traversal: Often blocked or unreliable behind NAT/firewalls ◦ Recommended: Avoid unless required for legacy compatibility • SIP_TRANSPORT_AUTO ◦ Behavior: Automatically picks an available protocol (e.g., UDP or TCP) ◦ Encryption: Depends (may not use TLS) ◦ Recommended: Only if you need automatic fallback and can accept potential unencrypted signaling If you want, I can provide the exact config snippet for an outbound trunk using

SIP_TRANSPORT_TLS

. Would you like that? Sources: SIP APIs | LiveKit docs | Secure trunking | LiveKit docs