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Indian DID numbers with SIP trunking

What a DID (direct inward dialing) number is, how an Indian DID on RingTrunk delivers calls straight to your SIP server with ordered failover, the number formats to expect on the INVITE, and how many calls a DID can carry at once.

Updated 6 September 2026

In short: a DID (direct inward dialing) number on RingTrunk is an Indian mobile number whose incoming calls are delivered directly to the SIP server you name, with no menu, no operator and no device in between, and the same number is the caller ID for calls you place.

What DID means

Direct inward dialing is the telephony term for a number that reaches a specific destination directly. On a phone system that destination is a desk; on RingTrunk it is the origination URI on your trunk: a LiveKit SIP endpoint, your own SIP service, or anything else that accepts an INVITE.

How an Indian DID reaches you

  1. Someone dials your number from any Indian phone.
  2. RingTrunk sends an INVITE from its source IP to the first enabled origination URI on the trunk the number is attached to. The INVITE carries no credentials, so your server accepts it by that IP.
  3. If that URI does not answer, the next one in priority order is tried. This is failover, not load balancing.
  4. The user part of the request URI is your number in 10-digit form, for example 9XXXXXXXXX, so you can route on it. The From header carries the caller's number.

Media then flows directly between the carrier and your server. RingTrunk does not sit in the audio path and never records it.

Formats to expect

On RingTrunk itself numbers are always 10 digits with no prefix. Platforms that match the To header against a list, such as LiveKit's inbound trunk, should list the number in every form it may arrive in: 9XXXXXXXXX, +919XXXXXXXXX, 09XXXXXXXXX, 919XXXXXXXXX.

How many calls a DID carries

Every number comes with a number of channels, one channel being one concurrent call. A trunk's limit is the sum across its attached numbers, and a call beyond it is refused with 486 Busy Here while calls in progress are untouched.

When nobody is there to answer

Set a forwarding number on the DID and incoming calls ring that phone instead of your SIP endpoints, with the DID itself shown as caller ID. Clear it and delivery returns to the trunk. Details in Receiving calls.

Getting a DID

Request access at ringtrunk.com, create a trunk, attach the number. The LiveKit Cloud guide shows the receiving side end to end.