BYOC — bring your own carrier — means connecting your own carrier’s SIP trunks to a communications platform instead of buying minutes from the platform itself. The platform keeps doing what platforms do — APIs, call flows, agent desktops — while a carrier you chose, at rates you negotiated, carries the calls to and from the phone network.
SIPNEX is an FCC-licensed carrier, and we sit on the carrier side of BYOC configurations every week — platforms in front, our trunks behind. This is the view from the trunk side, not from a platform’s marketing page.
What BYOC actually means
Every platform call has two layers. The software layer is why you picked the platform: programmable call control, IVR builders, agent routing, the developer API. The carriage layer is the unglamorous part underneath — originating and terminating calls on the public switched telephone network, owning the numbers, signing the calls.
By default the platform resells carriage bundled into its per-minute price — it buys wholesale capacity from underlying carriers, marks it up, and hands you one invoice. BYOC breaks the bundle: you keep the platform for its software and point its voice traffic at SIP trunks from a carrier you selected directly.
The major platforms all productized this, under different names:
- Twilio offers BYOC Trunking for Programmable Voice and Flex — your carrier connects to a dedicated ingress, and Twilio’s voice API runs on top of your carrier’s minutes.
- Zoom Phone supports BYOC as Cloud Peering (BYOC-C), the carrier peering directly with Zoom’s data centers, or Premises Peering (BYOC-P), with your own session border controller in the path.
- Microsoft Teams calls the same architecture Direct Routing — your carrier’s trunks reach Teams through a certified SBC.
- Genesys Cloud offers BYOC Cloud (SIP trunks straight to the Genesys media tier) and BYOC Premises.
Different labels, identical architecture: the platform stops being your carrier and becomes purely your software vendor.
Why operators bring their own carrier
Rate control. A platform’s bundled per-minute price includes the wholesale carrier cost plus the platform’s margin — on every single minute, forever. At low volume the margin is a rounding error; at dialer or contact-center volume it becomes the largest controllable line item in the operation. BYOC replaces the opaque bundled rate with a carrier rate you can see, negotiate, and re-shop.
Attestation ownership. Under STIR/SHAKEN, the carrier that puts your call onto the PSTN signs it, and the attestation level it can honestly assign depends on its relationship with you and your numbers. When the platform is your carrier, you inherit whatever signing arrangement its upstream stack produces. When you bring your own carrier, you choose the entity that signs — and A-level versus B-level attestation is the single largest controllable factor in whether your calls display cleanly or get flagged.
Number ownership and portability. With BYOC, your DIDs live at your carrier, not inside the platform. Switch platforms next year and your numbers do not move at all — you repoint trunks. Without BYOC, leaving a platform means porting every number out of it, with the project timeline and reputation-continuity risk that implies.
One carrier, many workloads. A carrier relationship is reusable. The same trunk group and DID inventory can feed a CPaaS integration, a PBX, and a dialer cluster simultaneously. A platform’s bundled minutes feed exactly one thing: that platform.
How BYOC works technically
Strip the product names away and BYOC is ordinary SIP trunking with a platform as one of the endpoints. If the underlying mechanics are new to you, start with how SIP trunking works; here is the BYOC-specific part.
Outbound (platform to PSTN). When your application or agent places a call, the platform builds the SIP INVITE as usual — but forwards it to your carrier’s ingress instead of the platform’s own upstream carriers. Your carrier authenticates the trunk, validates the caller ID against your authorized numbers, signs the call with its STIR/SHAKEN certificate, and terminates it to the called party’s network. The platform executed the call logic; your carrier originated the call.
Inbound (PSTN to platform). A call arrives at your carrier for one of your DIDs. The carrier forwards the INVITE to the platform’s BYOC ingress — typically a fully qualified domain name the platform assigns you (Twilio’s follow the pattern yourname.sip.us1.twilio.com). The platform answers, runs your call flow, and bridges media.
Authentication: IP-based, not registration. SIP trunks authenticate one of two ways. Registration-based trunks send a REGISTER with digest credentials so the carrier learns where the endpoint currently lives — built for PBXs behind NAT on changing addresses. IP-authenticated trunks skip registration: both sides whitelist each other’s static addresses. Platform BYOC ingress is essentially always the second model — platform gateways sit on fixed, published address ranges, so carrier and platform exchange IP ACLs, usually with TLS signaling and SRTP media on top. No registration handshake to break at 2 a.m.
The SBC variants. Teams Direct Routing and Zoom BYOC-P put a session border controller you operate between carrier and platform — it normalizes SIP dialects, handles encryption, and gives you a demarcation point for traces. Zoom BYOC-C and Genesys BYOC Cloud skip the customer SBC and peer carrier to cloud directly.
Media. Voice travels as RTP between carrier media gateways and platform media servers, codec negotiated in SDP. Keep G.711u end to end — every transcode hop adds latency and degrades audio, and native pass-through avoids the problem entirely.
When BYOC is not worth it
BYOC is an operational commitment, and pretending otherwise sells trunks to people who will regret buying them.
Skip it at low volume. The platform’s markup on a few thousand minutes a month is less than the cost of the hours you will spend standing up and maintaining the integration. The bundled price buys real convenience; at small scale, take it.
Skip it with no telecom ops capacity. BYOC means someone on your team owns trunk configuration, reads SIP traces when calls fail, manages DID inventory and CNAM, and coordinates two vendors when a problem could live on either side of the ingress. If nobody owns that, bundled minutes are the correct product — a single vendor to call is worth the markup.
Check feature dependencies first. Some platform features assume platform-purchased numbers or platform-side carriage. Before committing, confirm the capabilities you rely on are supported on BYOC trunks — the gaps are occasionally surprising.
BYOC versus leaving the platform entirely
BYOC and full migration answer different questions. BYOC says: the software is worth keeping, the carriage is not. You keep the APIs and agent tooling and swap only the minutes underneath. Full migration says: neither layer earns its cost — replace the platform with your own stack (a PBX, an open-source dialer, direct trunks) and drop the software fees too.
In practice, BYOC is often stage one of a migration whether or not you planned it that way. Once your numbers and traffic live at your own carrier, replatforming later becomes purely a software decision — no ports, no attestation reset, no carriage disruption. If you are weighing the two paths for an outbound operation, our Twilio versus SIPNEX comparison walks through the full-migration math.
The carrier side of a BYOC setup
What you should demand from the carrier half of a BYOC configuration is exactly what SIPNEX built:
Signing that survives the hop. SIPNEX holds its own STIR/SHAKEN SP-KI certificate and signs at A-level for verified DIDs under the FCC’s call authentication framework. Because the carrier is the signer, that attestation applies regardless of which platform sits in front of the trunk — your CPaaS integration inherits carrier-grade attestation instead of the other way around.
Published rates instead of platform markup. Entry pricing runs $0.025–$0.030 per minute under 100k minutes per month and steps down to as low as $0.005 at 10M+, on 6-second billing. No per-channel fees, no platform fees, no setup or porting fees — the rate card is public.
Capacity and speed. Unlimited concurrent channels, sub-3-second average PDD, G.711u native, trunks provisioned in 24 hours, and same-day US DIDs with CNAM included on most orders — the carrier side of your BYOC project is ready before the platform side finishes paperwork.
Frequently asked questions
What does BYOC mean?
BYOC stands for bring your own carrier. It means connecting SIP trunks from a carrier you chose directly to a communications platform — a CPaaS like Twilio, a UCaaS like Zoom Phone or Microsoft Teams, or a contact-center platform like Genesys Cloud — instead of buying bundled minutes from the platform. The platform continues to provide the software; your carrier originates and terminates the calls, owns the numbers, and signs the traffic.
Why use BYOC with a CPaaS?
Three structural reasons: rate control, attestation ownership, and number portability. Bundled platform minutes carry a markup on every call, which compounds at volume. The carrier that originates your calls determines your STIR/SHAKEN attestation, so BYOC lets you choose a carrier that signs at A-level. And because your DIDs live at your carrier rather than inside the platform, you can change platforms later without porting a single number.
Does BYOC keep STIR/SHAKEN attestation?
Yes — attestation follows the carrier, not the platform. The carrier that puts the call onto the PSTN attaches the signed Identity header, and its attestation level depends on its verified relationship with you and your calling numbers. If your BYOC carrier holds its own SP certificate and has verified your DIDs, your calls carry A-level attestation even with a CPaaS executing the call logic in front of the trunk.
Is BYOC cheaper?
At volume, usually — but the mechanism matters more than a blanket claim. BYOC replaces the platform’s bundled per-minute price, which includes carriage plus margin, with your carrier’s direct rate plus whatever reduced per-call or per-minute fee the platform charges on BYOC traffic. Run the comparison at your actual minute count and check the platform’s BYOC fee schedule. At low volume, the savings rarely cover the operational overhead; at dialer volume, they typically dominate the decision.
SIPNEX is the carrier side of the BYOC equation: A-level attestation under our own certificate, published wholesale rates, unlimited channels, and trunks live in 24 hours. If the platform is the part you want to replace too, start with the Twilio alternative built for operators — or talk to us about a BYOC trunk at (833) 665-2220.
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FCC-licensed carrier with its own STIR/SHAKEN SP certificate. Operator-owned. SIP trunks built for operators who dial at volume.