Replace expensive PRI circuits with flexible cloud voice
SIP (Session Initiation Protocol) trunking connects your phone system to the public network over your internet connection — replacing the physical PRI circuits that cost thousands a month in line rentals and per-minute charges. With RingOffice, the trunks run on its own carrier-grade softswitch (3CX-certified), so the voice network, the phone platform and the managed service all come from one accountable provider. Every trunk is professionally configured, monitored 24/7 and backed by multi-carrier redundancy, so a single carrier outage doesn't take your calls down.
RingOffice's own trunk service
On a white-labelled carrier-grade softswitch — not a reseller stitching together third-party carriers.
3CX-certified
Certified for 3CX and compatible with any SIP-compliant phone system.
One accountable provider
Voice network, platform and management from one team.
Legacy PRI vs RingOffice SIP trunking
You have an existing phone system
Keep your SIP-compliant PBX and replace only the carrier connection — no rip-and-replace.
Your PRI contract is expiring
PRI renewals lock you in for years at legacy rates; SIP gives you flexible terms.
You need to add locations
A new office no longer needs a new PRI circuit — trunks provision in days from your existing system.
Three scenarios where businesses switch to SIP
Most businesses make the switch when their PRI contract expires, when they're adding a location, or when their current carrier's reliability becomes a business problem. In every case the outcome is the same: lower monthly costs, better reliability, and carrier infrastructure that scales with the business instead of holding it back.
Get a quote →A SIP trunk provider built for resilience: multi-carrier architecture
Single-carrier SIP means single-carrier outages. RingOffice routes calls across multiple carriers with automatic failover, so a carrier event doesn't become your outage.
Complete North America coverage
RingOffice SIP trunking covers the continental United States and Canada with local DID numbers in every major market — so you can have a local presence in any city without a physical office.
United States
Local DIDs nationwide and toll-free numbers (800/888/877/866/855/844/833), with E911 service.
Canada
Local DIDs across the provinces and Canadian toll-free numbers, with E911 service.
International
Outbound calling to 40+ countries at competitive per-minute rates, plus inbound DIDs in major international markets.
Technical specifications for our 3CX SIP trunks and BYOC
Carrier-grade infrastructure, professionally configured — no technical burden on your team.
PBX compatibility
▸Certified for 3CX
▸Any SIP-compliant PBX (RFC 3261)
▸Hosted or on-premise phone systems
▸SBC-fronted deployments
▸IP desk phones & softphones
▸RingOffice configures the SBC for you
Protocol support
▸SIP over UDP, TCP, TLS
▸G.711, G.729, G.722 codecs
▸T.38 fax protocol
▸SRTP media encryption
▸RFC 3261 compliant
▸DTMF RFC 2833
Network requirements
▸20–100 Kbps per call (codec dependent)
▸QoS / DSCP marking recommended
▸Static IP or dynamic DNS
▸SBC recommended for security
▸Firewall ports: 5060 / 5061 SIP
▸RTP ports: 10000–20000
Get your per-channel SIP rate
Tell us your channel count, term and call volume, and we will send a transparent per-channel SIP quote built to your setup — no hidden markup.
Questions buyers ask about SIP trunking
The real questions teams ask when moving off PRI.
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