The SIP trunk built for Vapi voice agents

Yes. didlogic connects to Vapi as a Custom BYO SIP Trunk. Our SIP trunks meet every requirement in Vapi’s BYO specification, including UDP and TLS signaling, G.711 codec, username and password authentication, SRTP, custom SIP header pass-through, and SIP REFER for transfers. A test call typically goes through within 10 minutes of finishing setup.

Vapi’s docs cover four configurations by name: Plivo, Telnyx, Zadarma, and Custom BYO SIP Trunk. didlogic connects through the Custom BYO option, which is the standard path for any provider implementing standard SIP. Many production Vapi teams run on didlogic today, and a step-by-step Vapi setup guide is published on the didlogic docs.

Two main differences. First, no per-channel fees, which is the line item that bloats Twilio bills on outbound AI campaigns. Second, deeper global DID coverage (130+ countries with licensed local voice in 17, versus Twilio’s smaller direct-coverage footprint). The Vapi platform fee is the same either way. What changes is the telephony layer underneath. See our Twilio alternative for AI voice page for a detailed breakdown.

Telnyx is also pushing its own AI voice platform, which competes with Vapi for the same customer. didlogic does not sell an AI voice product. We only provide the telephony layer, so there is no conflict with the Vapi stack you chose.

Vapi’s signaling SBC is hosted in AWS us-west-2 (Oregon), so SIP signaling and RTP media cross to North America regardless of where your number is. What you can control is the carrier-side path. didlogic peering keeps the leg from a European or APAC carrier to a US PoP short and clean. Conversation latency you experience also depends on Vapi’s STT, LLM, and TTS providers, which sit above the voice transport layer.

That is almost always RTP inactivity on silence. When the AI is thinking, no audio is being sent in either direction, and intermediate devices time out the RTP stream. didlogic SBCs send RTP keepalives during silence by default, which keeps the media path live across the gaps. On other providers, the fix is RTP keepalives or a longer RTP inactivity timeout on the carrier side.

Vapi’s signaling IPs are 44.229.228.186 and 44.238.177.138. didlogic’s outbound to Vapi works without additional configuration on our side. On the Vapi side, you point the byo-sip-trunk credential at the didlogic regional gateway (sip.nyc.didlogic.net or sip.lax.didlogic.net for Vapi’s US-located SBC). Username and password authentication is recommended over IP-based, in line with Vapi’s own guidance.

Yes. Vapi’s transferCall tool with type: “sip” sends a SIP REFER to the destination URI. didlogic handles incoming REFER on the trunk and routes the transfer through. The transfer URI in the Vapi tool definition should point at the didlogic side (for example, sip:[email protected]) in proper E.164 format.

Yes. Vapi reads custom SIP headers prefixed with X- and uses them to fill template variables in your assistant. didlogic preserves custom SIP headers on inbound INVITE messages, so headers like X-First_Name, X-Account_ID, or X-Lead_Source arrive at Vapi as you set them.

Yes. Vapi’s BYO SIP Trunk supports both inbound and outbound on the same credential. didlogic supports both directions on the same SIP account. For outbound, the no-channel-fees model means concurrency scales without telephony tier upgrades.

Yes. Vapi’s own number inventory focuses on US and Canada. didlogic supplies numbers in 130+ countries, including markets where most providers have gaps (parts of MENA, Southeast Asia, and Africa). Once provisioned on didlogic, the number works through Vapi like any other byo-sip-trunk DID.

Yes. didlogic supports paperless LNP in 8 countries and manual porting in most others. Porting a number does not require downtime. A common pattern is porting your Twilio numbers to didlogic while keeping Twilio for SMS or other rails. Vapi’s BYO setup does not care which carrier owns the DID.

Free Vapi numbers are US-only and shared infrastructure. For anything in production, particularly outside the US or at meaningful concurrency, a BYO SIP trunk gives you owned numbers, deterministic routing, and no shared-pool failure modes. didlogic gives you that in 130+ countries.