How to compare SIP providers

Choosing a SIP provider is not a logo-picking exercise. The provider you select determines whether your calls arrive authenticated, how quickly you can port numbers, how routes hold up under load, and what you pay per minute at scale. Most buyer's guides rank providers by brand recognition or feature checklists. This one ranks them by the operational benchmarks that actually decide call quality and compliance: caller-ID attestation, route control, security posture, and pricing transparency.

The single axis that separates the field is carrier ownership. A provider that owns its underlying network behaves very differently from one that resells upstream capacity, and the difference shows up in your call analytics, your porting timelines, and your invoice.

Why carrier ownership is the differentiating axis

Under the U.S. STIR/SHAKEN framework, the originating provider attests to each call it signs. To assign full A-level attestation, a provider must be responsible for putting the call on the network, have a direct authenticated relationship with the customer, and have a verified association with the number being used. A provider that meets all three can vouch for the call. A reseller that does not control the originating network or own the number typically cannot, so its traffic is more likely to carry partial or gateway attestation and get flagged as "Scam Likely" at the terminating end.

This stopped being a nice-to-have in 2025. The FCC's Third-Party Authentication Order, effective September 18, 2025, requires every voice provider with a STIR/SHAKEN obligation to obtain its own Service Provider Code token and certificate rather than leaning on an upstream carrier's certificate. Providers that own their network and authenticate their own traffic are structurally better positioned to meet this bar.

The coverage gap is real and getting worse, not better. A recent FCC fact sheet notes that large providers exchange STIR/SHAKEN information on roughly 86% of the traffic exchanged between them, yet a significant share of calls still reach the terminating provider without authentication intact because the framework only works on IP networks. The structural cause is straightforward: calls that traverse non-IP segments lose their authentication along the way. The fewer hops and the more of the path a provider controls, the better your attestation survives.

The buyer's matrix

The table below compares the provider archetypes you will encounter on most "best SIP provider" lists, scored on the dimensions that matter to a procurement decision. The point is not which company is best in the abstract, but which architecture fits a given buyer's volume, compliance needs, and geography.

Use the matrix as a filter, not a verdict. A 20-seat office may be perfectly served by a UCaaS bundle. A contact center signing millions of calls a month, or a healthcare or financial operation where a "Scam Likely" label costs real money, should weight attestation and route control heavily, and those favor a carrier-owned platform.

The SIP security baseline is being rewritten

SIP security models were designed for a carrier-to-carrier interconnect world. That world is gone. The GSMA's Fraud and Security Group published its FS.38 "SIP Network Security" permanent reference document precisely because legacy threat models no longer cover the IP-native, multi-cloud topology of modern SIP deployments. FS.38 takes a defense-in-depth approach rather than assuming a session border controller at the edge is sufficient, and it folds SIP into the same protocol-correlation framework the industry already applies to SS7 and Diameter.

For a buyer, the practical question is whether your provider treats security as an architectural property or a bolt-on. Ask how they handle media encryption (the SRTP protocol is the relevant standard), how they isolate signaling, and whether their security posture is built into the network you are buying or layered on top of someone else's.

What the institutional buyers actually do

Two reference points cut through the marketing.

Higher education buys SIP through Internet2's NET+ Lumen program, active since 2012. Institutions get peer-authored, pre-negotiated SIP trunking contracts rather than negotiating alone. As Internet2 describes it, the program offers SIP-based services such as local trunks, long-distance trunks, toll-free, conferencing, and UC services designed to provide flexibility, local control, and local survivability so each campus can tailor the deployment to its needs. The lesson for any buyer: route quality, local control, and survivability are the criteria institutions with real procurement clout prioritize.

State governments do something similar in the open. Louisiana's Division of Administration publishes a SIP trunking service catalog with vetted vendor contracts, and it applies a support service fee of 0.5% to the monthly cost. Agencies submit a request, the office gathers requirements, identifies which vendors can serve the area, and validates rate quotes before the agency chooses on technical fit, timeline, or price. That is a transparent, requirements-first procurement process, and it is a good template for a private buyer's own evaluation.

Read past the headline rate

SIP trunking's core economic appeal is durable. Migrating off legacy PRI lines saves enterprises between 25% and 65%, which is why high-volume, multi-site operations move first. The SIP trunking market sits around $73 billion in 2025 on most estimates and is growing at a double-digit CAGR as PSTN decommissioning mandates push the remaining legacy lines onto IP. Underneath all of it sits a single open standard: SIP, the IETF-standardized signaling protocol every commercial provider builds against.

But the headline per-minute rate hides the variables that matter. Ask:

• Is the rate the wholesale rate, or a reseller markup over someone else's wholesale?
• What are the porting fees and timelines, and who actually owns the numbers?
• Are there separate charges for attestation, fraud monitoring, or international termination?
• How does pricing change at your real volume, not the demo volume?

A carrier-owned provider can usually quote a transparent per-minute rate because it is not buying capacity from a layer above it. Independent SIP pricing surveys in 2026 put typical metered retail rates between roughly half a cent and three cents per minute depending on destination and provider tier. Telnyx SIP trunking lands near $0.005 per minute, at the low end of that range and roughly half a typical retail metered rate, because Telnyx terminates on its own network rather than buying capacity from a layer above it. That structural fact, more than any promotion, is what keeps pricing predictable as you scale.

A practical evaluation checklist

When you put providers side by side, score each on the operational axes rather than the brochure:

1. Attestation: Do they sign their own traffic with their own certificate, and can they show you A-attestation rates?
2. Network control: Do they own the underlying carrier network, or resell it? How many points of presence, and where?
3. Portability: How fast can they port your numbers, and do they own number inventory directly?
4. Security architecture: Is encryption and signaling isolation native to the platform?
5. Pricing transparency: Is the per-minute rate the real rate at your volume, with porting and ancillary fees disclosed up front?

Run every shortlisted provider through those five questions and the field sorts itself quickly.

Where Telnyx fits

Telnyx is one of the few SIP providers that owns its underlying carrier network rather than reselling upstream capacity. That ownership is what lets us sign eligible traffic at A-level STIR/SHAKEN attestation as the originating carrier, the highest level the framework allows, where we have direct authenticated knowledge of the caller and the number. It also lets us route calls across our own global points of presence in 40+ countries, port numbers we control directly, and quote transparent per-minute pricing at scale. Our CEO, David Casem, frames the architecture simply: "By moving to a SIP-native core with co-located compute, we've solved the network physics of voice."

If you are building or buying voice, the practical entry points are our SIP trunks for enterprise-grade trunking, our Voice API for programmable call control, and direct provisioning of phone numbers on the same platform. Teams replacing legacy carriers can route their own traffic through our bring your own carrier option, and regulated operations can dig into our guidance on SIP trunking for healthcare to see how the compliance pieces fit together.

Carrier ownership is also the foundation everything else builds on. The same network that authenticates and routes your calls is where Telnyx runs co-located GPU inference and voice AI, so when you are ready to add an AI layer, the carrier is already in scope. Voice is the wedge, not the ceiling.

Compare us on the five questions above, not on the logo. Start building on Telnyx today, or talk to our team about a SIP deployment sized to your volume and compliance needs.