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SIP and Telecom Glossary: Terms for Phone Numbers, SMS and VoIP

Updated 2026-10-23 · By the SMS Conecta team (SMSConecta Inc.)

Short answer: This reference breaks down the telecom, SIP and verification vocabulary that comes up when buying and running a phone number online. Every entry opens with a one-line definition, explains how the underlying technology functions, and spells out what it means in practice for a SMS Conecta number: a genuine mobile, local or toll-free line that ships with its own SIP login.

Telecom terminology is crowded with acronyms that vendors use loosely. Each page here pins down a precise definition, points to the standard behind it where one exists, and links onward to the guide where you can put it to work.

  • SIP — The protocol that opens, controls and closes voice calls over the internet.
  • SIP trunk — A SIP link that carries traffic between a phone system and the public network.
  • DID — Direct inward dialing: a number delivered straight to one line or account.
  • Softphone — An app that places and answers SIP calls from a computer or phone.
  • PBX — A private branch exchange: the system that routes calls within an organisation.
  • Web dialer — A browser-based dialer, so calling needs no software installed.
  • E.164 — The ITU-T format for writing numbers internationally: + country code plus subscriber digits.
  • Toll-free number — A number the caller reaches without paying for the call.
  • Local number — A geographic number attached to a city, region or area code.
  • Mobile number — A number from a country's mobile range, usually SMS-capable.
  • Virtual number — A number used online rather than fixed to a physical SIM or landline.
  • Non-VoIP number — A number that carrier lookups file under mobile or landline instead of VoIP.
  • OTP — A short one-time password sent by SMS or call to confirm who you are.
  • Two-factor authentication — Sign-in requiring a second proof, like a code, beyond just a password.
  • SMS verification — Confirming ownership of a number by texting it a code.
  • Call forwarding — Sending calls that land on one number on to another phone automatically.
  • Caller ID — The number a person sees when your call reaches their phone.
  • G.711 codec — The uncompressed ITU-T voice codec, in µ-law (PCMU) and A-law (PCMA) forms.
  • DTMF — The tones generated by keypad presses during a call, used in menus and PINs.
  • NAT and STUN — How routers remap addresses, and the protocol SIP gear uses to work around it.
  • IVR — Interactive voice response: an automated menu driven by key taps or speech.
  • CNAM — Caller name delivery: a name displayed alongside a number on some networks.
  • STIR/SHAKEN — A signing framework for caller ID built to stop spoofed robocalls.
  • Number porting — Carrying an existing phone number from one provider to another.

How to use this glossary

The entries fall roughly into three groups: number types (DID, local, mobile, toll-free, E.164), calling technology (SIP, SIP trunk, softphone, PBX, codecs, DTMF, NAT), and identity verification (OTP, 2FA, SMS verification, caller ID, CNAM, STIR/SHAKEN).

Each term's page closes with a short note on how that concept maps onto SMS Conecta, so you can tell which features the service actually offers and which it does not.

Number types at a glance

TermWhat it means
Mobile numberA number drawn from a country's mobile number range
Local numberA geographic number linked to a particular city or area code
Toll-free numberA number the caller can dial without being billed for the call
DIDAny number delivered straight to a line, extension or SIP account
E.164The international format that expresses any number as +country code plus subscriber number

Where SMS Conecta fits

SMS Conecta provides genuine phone numbers across 181 countries, and each one comes with unlimited inbound SMS and calls, 500 outbound SMS, 1,000 outbound minutes every month, its own SIP login, call forwarding, and a browser-based dialer. Pricing is identical across every number type, starting at $1.80 per month on annual billing ($21.60 per year).

A handful of glossary entries describe features that sit outside the service, such as number porting or call recording, and those pages state that clearly.

Standards referenced

  • IETF RFC 3261, which governs SIP signalling
  • ITU-T Recommendation E.164, which defines the international number format
  • IETF RFC 4733, successor to RFC 2833, covering DTMF carried as RTP events
  • ITU-T G.711, covering the µ-law and A-law voice codecs

Next steps

New to SIP? Start with the SIP, softphone and DID entries, then move on to the setup guide to connect a number to your first app.

Frequently asked questions

Who should read this glossary?

Anyone who buys or uses a phone number online, from someone waiting on a verification code to a team wiring numbers into a PBX. Every entry opens with a plain definition before getting technical.

Are SMS Conecta numbers genuinely real phone numbers?

Yes. They are real mobile, local and toll-free numbers on national phone networks across 181 countries, commonly called virtual numbers simply because you access them online.

Does every entry describe something SMS Conecta offers?

No. A few entries, number porting among them, cover industry concepts that fall outside the service, and those pages say so directly.

Where should a SIP newcomer begin?

Start with the SIP and softphone entries, then move to the guide on setting up a SIP dialer.

Related pages

Sources