3CX supports over 100 different SIP trunk providers globally. Applying and testing to become a 3CX supported VoIP provider is the best way to get your services out in front of 3CX customers and partners. To help you with this, we’ve prepared a technical document with the requirements for becoming a 3CX supported SIP trunk provider.

Technical requirements for VoIP providers

Getting your SIP trunks added to our list of supported VoIP provider pages will take a little work and some specific technical requirements. We break our requirements down into two separate categories:

Mandatory

· Registration-based trunks

· Instance parameter support

· Allowed IP address list

· DTMF support for RFC2833

· Proxy audio

· Error codes

Optional

· E164 number formatting

· TLS / SRTP

· T38 Support

· SMS / MMS Support

Due to the fact that these categories are relatively lengthy and somewhat complex, we have prepared a breakdown of each point including descriptions and SIP message examples. If you are a VoIP provider and interested in becoming a supported provider, check out our VoIP provider documentation to review the mandatory and optional requirements.

Why become a supported provider?

Imagine getting your name and brand in front of over 600,000 companies. Becoming a supported provider means:

· Your service will be included in the management console as one of the pre-configured SIP trunks in 3CX.

· Your company will be listed on our supported VoIP provider pages.

· We will test each version of our software against your service before release.

· We will offer first-level support to our partners and customers using your service.

Via：https://www.3cx.com/blog/news/voip-provider-requirements/