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SIP (Session Initiation Protocol)

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

Short answer: SIP, short for Session Initiation Protocol, is the IETF signalling standard laid out in RFC 3261 for starting, changing and ending voice and video sessions over IP. It manages who is calling whom and on what terms, while the audio itself travels separately as RTP. Any SIP-compliant app is able to use a SMS Conecta number.

Nearly every business phone system, softphone and VoIP provider speaks SIP, which is exactly why one SIP account can work across so many unrelated apps.

Definition

SIP is a text-based protocol, broadly resembling HTTP in style, whose requests (REGISTER, INVITE, BYE and others) tell servers where a user can be reached and open or close a call session.

How it works

  1. Your app sends a REGISTER request to the provider's SIP server, proving its identity via digest authentication.
  2. Placing a call means sending an INVITE with an SDP body listing the codecs it supports.
  3. The far end answers, a codec is agreed, and audio starts flowing as RTP packets.
  4. Either party can send BYE to close the call.

How it applies to SMS Conecta

Every SMS Conecta number comes with its own SIP username and password, visible on that number's dashboard page. Register against sip.smsconecta.com on UDP/TCP port 5060 or TLS port 5061, using G.711 µ-law or A-law and DTMF via either RFC 2833 or SIP INFO.

Server:   sip.smsconecta.com
Port:     5060 (UDP/TCP) or 5061 (TLS)
Username: <SIP_USERNAME>
Password: <SIP_PASSWORD>
Codecs:   PCMU, PCMA

SIP ports and transports on SMS Conecta

TransportPortServer
UDP5060sip.smsconecta.com
TCP5060sip.smsconecta.com
TLS5061sip.smsconecta.com

Common misconception

SIP doesn't carry the voice itself and isn't a phone number in its own right. The SIP account is the login credentials; the phone number is what a caller actually dials to reach it.

Related terms

  • SIP trunk
  • Softphone
  • Codec G.711
  • DTMF
  • NAT and STUN

Frequently asked questions

Is SIP just another name for VoIP?

No. VoIP is the broad concept of carrying voice over IP networks; SIP is the protocol most commonly used to set those calls up.

Which SIP apps can I use with SMS Conecta?

Any software that speaks SIP, which includes Zoiper, Linphone, MicroSIP, Bria, Groundwire, Asterisk, FreePBX, 3CX, FusionPBX and VICIdial.

Can I register over TLS instead of plain SIP?

Yes, TLS is on port 5061, while plain UDP and TCP use port 5060.

Is the call audio itself encrypted?

TLS only secures the signalling. SRTP media encryption is not offered.

Related pages

Sources