How to process trickled ICE candidates into offer and answer?

[MCCM Yu]

AFAIK, RtpEngine supports trickle ICE (a=ice-options:trickle) in case of WebRTC.

So I use my own signaling channel to exchange ICE candidates.

But how to add the exchanged ICE candidates into RtpEngine in both offer and answer cases?

1. offer

- call `offer` command with call-id, from-tag, and sdp

- when the remote ICE candidates arrived, calling `offer` again?

2. answer

- call `answer` command with call-id, from-tag, to-tag, and sdp

- when the remote ICE candidates arrived, calling `answer` again?

Please let me know the steps and exact format for adding ICE candidates.

[Richard Fuchs]

On 05/08/2025 01.55, MCCM Yu wrote:
> AFAIK, RtpEngine supports trickle ICE (a=ice-options:trickle) in case
> of WebRTC.
> So I use my own signaling channel to exchange ICE candidates.
> But how to add the exchanged ICE candidates into RtpEngine in both
> offer and answer cases?
>
> 1. offer
> - call `offer` command with call-id, from-tag, and sdp
> - when the remote ICE candidates arrived, calling `offer` again?
>
> 2. answer
> - call `answer` command with call-id, from-tag, to-tag, and sdp
> - when the remote ICE candidates arrived, calling `answer` again?

You would call "offer" in both cases. Reason being that typically with
SIP, trickle ICE updates are sent in SIP INFO messages, regardless of
whether it's an offer or an answer.

Only the call ID and the from-tag are required. Since answers have the
tags reversed, trickle ICE updates for an answer would have the from-tag
equal the to-tag.

The flag `fragment` must also be present in the `flags` list so that
these updates can be distinguished from full offers.

Cheers

[MCCM Yu]

Thank you. It works.

2025년 8월 5일 화요일 오후 8시 34분 4초 UTC+9에 rfuchs님이 작성: