SIP: how internet phones establish calls
Short answer: Session Initiation Protocol coordinates the signaling that starts, changes and ends an internet call. Audio travels through a separate media stream, so registration can work even when a firewall prevents sound.
A SIP account has a server and login credentials. A compatible client uses them to register the line, then negotiates the call and supported media settings.
Use the definition to check your setup
Session Initiation Protocol coordinates the signaling that starts, changes and ends an internet call. Audio travels through a separate media stream, so registration can work even when a firewall prevents sound.
A SIP account has a server and login credentials. A compatible client uses them to register the line, then negotiates the call and supported media settings.
SIP: how internet phones establish calls — points to check
| Review point | CallGlobal guidance |
|---|---|
| Concept | Session Initiation Protocol coordinates the signaling that starts, changes and ends an internet call. Audio travels through a separate media stream, so registration can work even when a firewall prevents sound. |
| Configuration implication | A SIP account has a server and login credentials. A compatible client uses them to register the line, then negotiates the call and supported media settings. |
| Product boundary | Consult the feature list; a glossary term does not identify an included capability. |
Where the CallGlobal line fits
Your number account provides the public telephone identity, its communication controls and the SIP credentials for compatible software. Other capabilities belong to the application or phone system you choose.
Review the live product feature list before relying on an additional function. Number porting, hosted IVR, voicemail, call recording and a public customer API are not included.
Protect the line and the account
- Keep account and SIP passwords private, including in support screenshots.
- Confirm the active rental term before relying on incoming communication.
- Use the complete international number and only an authorized caller identity.
Frequently asked questions
What does this term describe?
Session Initiation Protocol coordinates the signaling that starts, changes and ends an internet call. Audio travels through a separate media stream, so registration can work even when a firewall prevents sound.
How does this affect practical configuration?
A SIP account has a server and login credentials. A compatible client uses them to register the line, then negotiates the call and supported media settings.
Does every telephone concept name an included product feature?
No. A glossary explains terminology. The product feature page and your number dashboard identify the functions provided with a CallGlobal line.
Continue exploring
- SIP trunk
- softphone
- G.711 codec
- what a SIP number is
- set up a SIP dialer
- SIP troubleshooting
- Zoiper setup
- PBX: the system behind extensions and business call routing
Sources
- IETF: RFC 3261, SIP: Session Initiation Protocol (as of September 2026)