Twilio · Vonage · Bandwidth · open SIP
Communications APIs, and the pages that opened.
A free study lab for communications platform as a service: Twilio, Vonage, Bandwidth, Sinch, Telnyx, Plivo, Infobip, and Bird, plus FreeSWITCH, Asterisk, Kamailio, LiveKit, Jitsi, Matrix, and Jami. SIP, WebRTC, RTP, numbers, messaging, STIR/SHAKEN, emergency calling, webhooks, IVR, contact center, AI voice, and migration. A number that was not on an opened page is marked confirm. Emergency and recording notes are not legal advice.
12 tracks
What CPaaS names
The word, then the companies whose pages opened
3 lessons
SIP, WebRTC, RTP
Signaling, the description, and the media
3 lessons
Numbers and trunks
E.164, DID, and the private and public domains
3 lessons
SMS, MMS, 10DLC
Text, media, and the registration names
3 lessons
STIR and SHAKEN
Identity, attestation, and the vendor pages
3 lessons
Emergency calling
E911 words, and the duty pages that opened
3 lessons
Programmable APIs
Voice, video, messaging, and verify
3 lessons
Webhooks and IVR
Events inbound, and the verbs that gather
3 lessons
Contact center and AI
IVR, ACD, and the agent pages
3 lessons
Observability and price
Counts you can defend, and prices you confirm
3 lessons
Compliance and migration
From a PBX toward a trunk, without a fake cutover
3 lessons
Open alternatives
FreeSWITCH through Jami, then dates you confirm
3 lessons
Read this before the first lesson
The Wikipedia article that opened for this topic is Platform as a service. Its communications section calls a CPaaS a cloud platform for adding voice, video, and messaging to an application without building that infrastructure. Twilio's article describes programmable call and text APIs. Vonage's article describes a cloud communications provider, now an Ericsson subsidiary, whose offering includes communications APIs. Bandwidth's own home page lists voice, messaging, emergency calling, WebRTC, and authentication APIs.
SIP, in the Wikipedia article and in RFC 3261, sets up the session. RTP, in RFC 3550, carries the media. WebRTC, in RFC 8825, is an overview of browser real-time protocols, and the RFC says it does not itself specify a protocol. Those jobs stay on separate arrows. A vendor menu does not replace the RFC.
Some names in the brief did not survive contact with the public web. A Wikipedia title MessageBird returned HTTP 404, while developers.messagebird.com and bird.com/docs did open. The Zoom, Talkdesk, and Avaya sibling URL returned HTTP 404, so it is not linked. Cisco CUCM and UCCE were not opened, so those menus are confirm. The FCC call-authentication URL returned HTTP 403. Emergency notes cite the Enhanced 911 article and the vendor pages that did open. They are not legal advice.
Sources and go deeper
Opened 2026-10. A row marked confirm has no link, because that page was not verified.
- Wikipedia. Platform as a service, Communications platform as a service section last checked 2026-10
- Wikipedia. Twilio last checked 2026-10
- Wikipedia. Vonage last checked 2026-10
- Bandwidth. Bandwidth home last checked 2026-10
- RFC. RFC 3261, SIP last checked 2026-10
- RFC. RFC 3550, RTP last checked 2026-10
- RFC. RFC 8825, real-time protocols for browser-based applications last checked 2026-10
- Wikipedia. E.164 last checked 2026-10
- Wikipedia. STIR/SHAKEN last checked 2026-10
- Confirm. MessageBird Wikipedia article. confirm. The title returned HTTP 404. last checked 2026-10
- Confirm. Zoom, Talkdesk, and Avaya sibling lab. confirm. The URL returned HTTP 404. last checked 2026-10
- Confirm. Cisco CUCM and UCCE pages. confirm. Not opened in this session. last checked 2026-10
- Confirm. FCC call-authentication page. confirm. The request returned HTTP 403. last checked 2026-10
- Confirm. Current vendor price tables other than the Plivo WhatsApp commitment. confirm. last checked 2026-10