Choose the product before choosing a template
Gradwell publishes standard SIP Trunks alongside 3CX, Direct Routing and a separate high-volume platform. These are not interchangeable labels. Record the legal service, selected product, PBX or SBC owner, access path, peer details, numbers, channels, support tier and change contacts from the order before applying a vendor template.
The public guide says authentication may use IP whitelisting or username and password, but it does not establish one method for every product. Preserve the issued implementation record and the observed authorization exchange without exposing secrets.
Documented service facts
Reviewed 2026-10-07. Compare SIP trunk services →
SIP authentication
DocumentedGradwell's current guide says a deployment may use IP whitelisting or username and password, while its fraud guide describes IP authentication as a protection. The public pages do not establish which method applies to every product or order. Preserve the issued server, source addresses, identities, credentials and observed challenge or source-address decision for the exact trunk.
SIP registration
Not verifiedThe reviewed public pages do not define REGISTER as the universal connection model or publish one registrar, realm, Contact policy, expiry or refresh behavior. Obtain the implementation record for the selected standard, 3CX, Direct Routing or high-volume product and keep its signaling evidence separate from general setup guidance.
Inbound delivery
DocumentedGradwell advertises DIDs, flexible number presentation and inbound and outbound channels. Those portfolio claims do not define the delivered Request-URI, asserted identity, number normalization or route for one order. Retain the assigned inventory, port state, delivered identifiers and the PBX destination that matched each accepted test.
Routing and failover
DocumentedGradwell describes cloud deployment, multiple carriers, network resilience, monitoring and forwarding flexibility. The public pages do not publish one failover topology, trigger, retry response, restoration sequence, customer-access dependency or established-call behavior. Convert the ordered design into a bounded new-call failure test before making a continuity claim.
Number and regional availability
DocumentedThe service is presented for UK businesses and advertises local, non-geographic and international numbering plus porting. This does not establish current inventory, portability, identity rights, serviceability or regulatory eligibility for a particular address or number. Preserve dated order and port responses for the exact requirement.
Audio codecs and DTMF
Not verifiedThe public pages say codec and firewall settings are required but do not publish one codec, packetization, RTP-address, DTMF, transcoding or media-anchoring profile for all products. Obtain the selected service's interface specification and preserve both SDP bodies, negotiated payloads, RTP endpoints and decoded authorized-call evidence.
T.38 fax
Not verifiedThe reviewed SIP trunk pages do not establish T.38, G.711 pass-through, switchover, redundancy, gateway support or page limits. Treat fax as a separate entitlement and acceptance workflow tied to the exact product, gateway, codec path, access service and destination.
Signaling and media encryption
Not verifiedGradwell describes the service and network as secure and cites ISO 27001, monitoring and fraud controls. Those statements do not identify SIP TLS, certificate validation, SRTP, keying or an end-to-end protected path. Map each leg and verify the ordered controls and observed negotiation without transferring Wave or endpoint security features to the trunk.
Concurrent calls and call starts
DocumentedGradwell defines channels around simultaneous calls and separately markets a dedicated high-volume platform for high call-per-second and channel demand. Neither claim supplies a universal numeric entitlement. Record ordered channels, inbound and outbound limits, CAPS or call-start controls, burst policy, PBX and SBC ceilings and access bandwidth as separate quantities.
Emergency calling
Not verifiedThe reviewed public SIP trunk pages do not define emergency-call entitlement, caller identity, address registration, nomadic treatment, callback behavior or an approved test procedure. Obtain the current provider and regulatory process for every site, keep the location record current and maintain an alternative calling method.
Pricing model
DocumentedGradwell advertises PAYG and bundled options and says cost depends on requirements and usage. The public pages do not provide a complete current account rate card. Use a dated quote for channels, call starts, minutes, numbers, porting, connectivity, installation, options, support, taxes, term, renewal and cancellation.
Administration and support
DocumentedGradwell advertises central portal channel management, 24/7 network monitoring and separately priced 24/7/365 UK support. Preserve the purchased support tier, named contacts, escalation path, portal roles, maintenance notices, monitoring boundary and change record; portfolio wording does not establish one response target or service level for every account.
SMS and MMS
Not verifiedThe guide notes that SIP can manage multimedia sessions, including messaging, but the reviewed trunk pages do not establish SMS or MMS entitlement on trunk numbers, sender registration, API access, throughput, webhook security, retention or price. Treat messaging as a separately ordered service and workflow.
Keep channels and call starts separate
Gradwell defines a SIP channel around simultaneous calls. Its high-volume service is separately described for high channel capacity and call-per-second demand. Purchased channels, active inbound calls, active outbound calls, attempted call starts, bursts, PBX and SBC resources and access bandwidth are different limits.
Use the current order for numeric entitlements and an approved load plan for observed behavior. Marketing references to unlimited inbound traffic or major-PBX performance do not establish a universal call-start rate, exact-version compatibility or successful capacity test.
Turn resilience and security into path evidence
Gradwell describes its SIP infrastructure as cloud-based, monitored and deployed across multiple carriers. It also publishes fraud controls and recommends strong PBX and account protection. These facts do not define the ordered failover trigger, customer-access diversity, SIP TLS, certificate validation, SRTP or established-call survival.
Map the PBX-facing handoff, provider network, PSTN route and any recording or downstream leg. Preserve signaling, SDP and media evidence for protection, and run a bounded provider-approved new-call failure exercise before reporting continuity.
Prove number, media and emergency behavior
Flexible numbering and porting are ordering capabilities, not proof that a particular number is available, portable, active or delivered in the expected format. Keep assigned inventory, port state, Request-URI and asserted identity with the PBX route that accepted each authorized test.
The reviewed pages do not publish one codec, DTMF, T.38 or emergency-calling contract. Obtain the interface and emergency records for the exact service, then retain offer, answer, media, digit and approved emergency-validation evidence as separate acceptance items.
Bind price and operations to dated records
Gradwell advertises PAYG and bundled options, portal channel management, continuous network monitoring and optional support. A quote must still separate channels, call starts, usage, numbers, porting, connectivity, installation, support, taxes, term, renewal and cancellation.
Record portal roles, monitoring responsibility, named contacts, escalation, maintenance notices and the purchased support response. Public portfolio wording does not prove current serviceability, availability, price, interoperability or laboratory performance. No Gradwell service or call was tested for this record.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.
- Gradwell SIP Trunks ↗
- Gradwell SIP trunking portfolio ↗
- Gradwell SIP trunk guide ↗
- Gradwell telecoms-fraud guide ↗
Examples require adaptation to your topology. No live PBX or hardware testing is claimed.