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Placing calls from a RingTrunk trunk

How outbound calls work on a RingTrunk SIP trunk. Digest authentication, the caller ID rule, which destinations are carried, channel and calls-per-second limits, and the codec.

Updated 6 September 2026

In short: Outbound calls on RingTrunk authenticate with SIP digest, must present one of your attached numbers as caller ID, and reach Indian mobile numbers only.

Outbound calls, called termination, are calls your system places. Your platform authenticates to pstn.ringtrunk.com with the trunk id as the username and the password you were shown once, and sends an INVITE. We deliver the call to the Indian mobile network.

Authentication

SIP digest, any realm. There is no IP allow-list requirement on your side for outbound calls, so a platform behind NAT or on a dynamic address can place calls. If you want to lock a trunk to fixed addresses as well, set a termination IP ACL under the trunk's Settings; with an ACL configured, both the credentials and the source address are checked on every call.

Caller ID

The From number must be one of the numbers attached to the trunk, in plain 10-digit form, for example 9XXXXXXXXX. Presenting any other number, including a customer's number or a number from another provider, is rejected with 403 cli_not_allowed before the call reaches the network. This is an Indian regulatory requirement, not a platform preference.

Attach more numbers to a trunk to use them as caller IDs.

Destinations

Destination	Carried
Indian mobile numbers: 10 digits starting 6, 7, 8 or 9	Yes
Landlines	No, `403 destination_not_supported`
Short codes such as 100, 112, 1800…	No, `403 destination_not_supported`
International numbers	No, `403 destination_not_supported`

Dial the destination as a 10-digit number or with the +91 prefix; both forms are normalised.

Capacity

Channels. Every number comes with a number of concurrent channels, and the trunk's limit is the sum across its attached numbers. A call that would exceed it is refused with 486 Busy Here. Calls already in progress are never affected by a spike.
Calls per second. A separate rate cap. Exceeding it returns 503 with a circuit-congestion reason. Pace your dialling and retry.

Codec

G.711 A-law (PCMA) with 20 ms packets. Offering only G.729 or Opus fails with 488 Not Acceptable Here. Restrict the trunk, gateway or endpoint to A-law.

Placing a call from LiveKit

bash

lk sip participant create \
  --trunk <YOUR_OUTBOUND_TRUNK_ID> \
  --call +91XXXXXXXXXX \
  --number 9XXXXXXXXX \
  --room my-room

--call is the destination, --number the caller ID. See Connect LiveKit Cloud for the trunk setup.

Timing

A new trunk can take up to 60 seconds before its first registration succeeds. A rotated password is active within 60 seconds; the old one keeps working until then, and existing registrations are not dropped. Suspending a trunk blocks new calls immediately without disconnecting calls in progress.