carriers-sip
Registration string
The line of settings — username, password, and server address — that tells your SIP device or trunk how to log in and announce itself to a provider.
A registration string is the line of settings that tells a SIP (Session Initiation Protocol) device or trunk how to log in and announce itself to a provider. It bundles together the username, the password, and the server address into one configuration entry, and it is what lets a phone or trunk say "here I am, send my calls here."
You can think of it as the credentials your system uses to check in. When VICIdial or a softphone starts up, it sends this string to the provider's SIP registrar, which verifies the username and password and then knows where to deliver incoming calls. That ongoing check-in process is what the term Phone registration describes.
Registration strings matter most when you set up a SIP trunk to a Carrier. Get one character wrong in the password or the server name and the trunk simply will not come up, which is one of the most common first-day stumbles for newcomers. Many providers display the exact string to copy and paste in their portal, so transcribing it carefully saves a lot of frustration.
Not every connection uses one, though. Some providers instead recognize you by your server's address — an approach called IP authentication — where there is no username or password to register at all. The provider just trusts calls coming from a known IP. So when you connect a new trunk, the first question is which method your carrier wants: a registration string to log in, or your IP address on an allow list.
When a registration string is doing its job, your trunk re-checks in with the provider every few minutes so the connection stays fresh and incoming calls keep finding you. If that refresh fails — because of a typo, an expired password, or a network block — the registration quietly lapses and calls stop arriving, often with no obvious error until someone notices the silence. That is why the registration status is one of the first things to look at when a trunk that was working suddenly goes quiet. A few good habits help: copy the credentials exactly as the provider gives them, store the password somewhere safe rather than retyping it, and confirm the trunk shows as registered before you start a Campaign. Once it is up and steady, a registration string mostly takes care of itself, and you only think about it again when something on the SIP trunk changes.
Related terms
Carrier
A carrier is the phone company that actually carries your calls onto the public phone network — VICIdial dials, the carrier delivers.
IP authentication
A way for your carrier to recognize your dialer by its public IP address instead of a username and password, so calls connect without login credentials.
Phone registration
The process where a softphone or SIP device announces itself to VICIdial so the server knows where to send the agent's calls.
SIP (Session Initiation Protocol)
The standard signaling protocol that sets up, manages, and ends internet phone calls — how VICIdial talks to phones and carriers.
SIP registrar
A SIP registrar is the part of the phone system that records where each extension currently is, so incoming calls know which device to ring.
SIP trunk
A virtual phone line over the internet that connects your dialer to a carrier, letting you place and receive many calls at once without physical wires.