Wholesale SIP trunking. Carrier rates, no middleman.

Retail trunks are packaged for end users: per-seat plans, bundled features, office-scale volume, and support that assumes the buyer has never read a SIP trace. Wholesale strips all of that out. You get raw carrier capacity at tiered per-minute rates, billed 12/6, with unlimited concurrent channels. There are no per-channel, setup, porting, or platform fees. If you are provisioning phones for one office, retail SIP trunking is the right product. If you are moving hundreds of thousands of minutes a month, wholesale is.

Who buys at wholesale? ITSPs building their own voice products on carrier capacity. Resellers and MSPs who sell under their own brand and keep the customer relationship. PBX integrators provisioning trunks across dozens of client systems. Dialer shops running Asterisk and VICIdial at volumes where a tenth of a cent per minute is real money. Most providers serving these buyers are aggregators — two or three hops removed from the switch that actually terminates the call. Every hop adds margin and subtracts accountability. Buying from SIPNEX removes the hops.

The credentials behind the trunk are the carrier’s own. SIPNEX holds direct FCC authorization and files FCC Form 499. It signs every call with its own STIR/SHAKEN SP-KI certificate, so A-level attestation applies at every tier. It is registered in the Robocall Mitigation Database and is a registered RespOrg. The full carrier-services picture — termination, origination, DIDs, peering — lives on the wholesale VoIP page. If all you need is outbound minutes, SIPNEX also operates as a wholesale termination provider — see wholesale voice termination for termination-only detail.

Pricing at SIPNEX is volume-tiered and published. No quote gate, no NDA, no “contact sales to see a number.” Rates start at $0.025-$0.030 per minute at the entry tier. They step down to $0.005-$0.008 per minute at 10 million or more monthly minutes:

• Entry tier — under 100,000 minutes/month: $0.025-$0.030 per minute
• Top published tier — 10M+ minutes/month: $0.005-$0.008 per minute
• Above 10M minutes/month — custom pricing
• Billing increments — 12/6 (6-second steps after a 12-second minimum)
• Per-channel, setup, porting, and platform fees — none

Tier assignment is automatic. We meter your actual monthly usage and apply the matching rate. Cross into a higher tier and the better rate applies — no renegotiation, no contract amendment, no call to an account manager. Concurrent channels are unlimited at every tier, so concurrency never shows up as a line item. The current tier table is on the published volume-tier pricing page.

Every trunk ships with the full carrier feature set. Nothing below is an add-on, an upsell, or a higher-tier unlock:

• A-level STIR/SHAKEN attestation — signed directly with SIPNEX’s own SP-KI certificate, at every volume tier
• Unlimited concurrent channels — no caps, no per-channel fees
• G.711u native pass-through — with G.729 fallback for bandwidth-constrained links
• Sub-3-second average PDD — calls start ringing while slower routes are still setting up
• 24-hour trunk provisioning — with same-day DID provisioning for most orders
• CNAM registration — included with every DID
• Nationwide US DID inventory — with bulk DID volume discounts

• Carrier status. Ask for the FCC Form 499 Filer ID and the Robocall Mitigation Database listing. Every provider in the US call path must file in the RMD. Intermediate and terminating carriers are barred from accepting traffic from providers that are not listed. A provider that cannot show both is reselling someone else’s network.
• Who signs the call. A-level attestation requires the signer to know the customer and its right to the number. Most resellers cannot sign at all: their upstream carrier signs, and it usually signs at B-level because it cannot verify your number rights. Ask whose SP-KI certificate ends up on the Identity header. Partial (B) attestation is, for the analytics engines, a lower-trust signal, and no carrier publishes how big the answer-rate gap is. The structural reason is in A-level vs B-level STIR/SHAKEN attestation.
• Billing increments. Get the increment in writing. At the same headline rate, 60/60 doubles the cost of a typical 25-second dialer call compared with 12/6. Twilio and Telnyx bill voice 60/60; SIPNEX dialer traffic bills 12/6. The worked math is in the 60/60 versus 12/6 section of SIP providers that allow auto dialers.
• Route quality on your traffic. Ask for ASR, ACD, and PDD on the routes you will actually send, not network-wide averages. Then verify the figures from your own switch during a trial, on your own lead lists.
• CPS and concurrency. Ask for the calls-per-second ceiling and what happens above it. Telnyx documents its standard default as 20 CPS per SIP username or source IP, and rejects excess attempts as SIP 503. A campaign ramp that exceeds the ceiling turns into failed originations mid-shift.
• Media handling. Confirm that G.711u passes through untouched, and ask where transcoding happens, if anywhere. Every transcoding step degrades audio. G.729 should be a fallback you choose for a constrained link, not something the route imposes.
• Numbers and porting. If you will provision DIDs, ask about inventory coverage, porting turnaround, CNAM, E911, and toll-free control. Whoever holds the RespOrg record controls a toll-free number’s routing and every change to it — ask whether that is the carrier itself.
• Technical support model. Wholesale assumes your team runs first-line technical support for your own customers. Ask how a carrier-side fault escalates, who answers after hours, and what the response targets are.

A longer version of this checklist, with the answers that should worry you, is in 7 questions to ask your SIP trunk provider.

A trunk is a SIP relationship between your switch and the carrier’s edge, plus the media that follows it. Your switch sends an INVITE to the carrier’s session border controller. The carrier authenticates it in one of two ways. IP authentication trusts a whitelisted source address, the usual choice for a fixed-location switch. SIP registration with digest credentials covers a switch whose address changes. From there, completing the call is the carrier’s job.

Completion starts with a routing lookup. Since local number portability, the dialed digits no longer say which carrier serves a number. So the carrier dips the Location Routing Number (LRN) and routes — and rates — the call on where the number actually lives. Before the INVITE leaves its network, an originating carrier that holds its own SP-KI certificate signs the STIR/SHAKEN Identity header. The call then hands off to the terminating carrier and, through it, reaches the PSTN (public switched telephone network). The billing side of that lookup is covered in what an LRN is.

Media follows signaling. With G.711u pass-through, the RTP audio your switch sends is what the far end hears; there is no transcoding step in between. G.729 is the fallback for bandwidth-constrained links. Post-dial delay measures the gap between your INVITE and the far-end ring, and predictive pacing is the first thing a high or variable PDD breaks. The codec bandwidth math is in the SIP trunk sizing guide; the signing mechanics are in the STIR/SHAKEN certificate chain guide.

Dialer operations. Short average call length makes the billing increment the biggest lever on your effective rate, ahead of the headline price. Bursty originations make the CPS ceiling the second. Attestation matters because lower trust is how the analytics engines read a partial (B) signature. The specifics of running Asterisk and VICIdial on carrier trunks are on the VICIdial carrier page.

ITSPs and resellers. Your product is built from number services as much as from minutes: local DIDs, porting, CNAM, E911, and toll-free. SIPNEX provisions E911 across all 50 US states and holds toll-free numbers as a RespOrg, so the toll-free record sits with the same carrier that terminates your calls. Porting timelines and pitfalls are in the number portability guide.

PBX integrators. You provision trunks across many client systems, so consistency beats cleverness: one authentication method per site, one codec policy, and a documented failover path. IP authentication suits a client PBX with a static address; registration suits sites behind dynamic addresses. The SIP trunk configuration guide maps where trunk settings live on 3CX, Yeastar, and other common platforms.

Most SIP trunking solutions are packaged around a single workload — an office phone system, a call center seat, an API. Wholesale capacity is workload-agnostic, because the Session Initiation Protocol (SIP) is the common signaling layer under nearly every modern voice product. Unified communications suites bundle voice with messaging, video, and presence, but the voice leg still rides a trunk. The platforms you build or resell decide the feature set. The trunk underneath decides whether the call connects fast and sounds right.

Contact centers are the demanding case. Outbound campaigns burst to hundreds of simultaneous calls, inbound queues live and die on call routing, and agents hear a dip in call quality before any dashboard graphs it. This is where the trunk spec earns its keep. Unlimited concurrent channels absorb the bursts. G.711u pass-through keeps audio unprocessed end to end. Sub-3-second post-dial delay keeps agents talking instead of listening to silence. Fewer dead-air seconds and fewer dropped calls register as customer satisfaction on the other end of the line.

For resellers, the wholesale layer is what makes the retail pitch work: business communications that complete more calls for less money. The cost savings come from tier math rather than corner-cutting, which keeps reselling this capacity cost-effective as volume grows. Aggregators advertise global reach — every country on one rate card — by stitching together other carriers’ routes. SIPNEX runs the opposite model: US-focused voice services, kept close to the switch that terminates them. Package the trunks as your own SIP trunk services, and every phone number you provision ships with CNAM registration included.

White-label is not a special program bolted onto these trunks — it is how they are designed to be used. You buy carrier capacity at tiered wholesale rates, set your own retail rates, and sell under your own brand. Your customers see your name on the invoice, your portal, your support line. SIPNEX stays invisible underneath: the switch, the attestation, the rate deck.

The margin math works because nothing structural eats it. No platform fees. No per-channel fees. No long-term contract holding you to volumes you have not hit yet. And because SIPNEX signs with its own SP-KI certificate, your end customers’ calls carry A-level attestation — a claim most resellers cannot make, because their upstream is itself a reseller. The commercial structure for building on SIPNEX capacity is documented in the VoIP reseller program. At 1 million minutes per month and above, direct SIP peering between your switch and ours is available.