Re: Feedback and questions regarding DataChannel large-file transfers and multipoint usage

Hi Yvan,

Some thoughts below.

> On 23 Nov 2025, at 19:00, Yvan Wamba <yvangoudjou04@gmail.com> wrote:
> 
> Hello WebRTC WG,
> 
> My name is Yvan Ngoudjou, and over the last few years I’ve been working on two WebRTC-based projects that exposed some behaviors or limitations where I believe feedback from the Working Group might be valuable.
> 
> While implementing these projects, I encountered recurrent patterns related to multipoint architectures and large DataChannel transfers, and I would appreciate guidance or confirmation regarding the expected behavior from the current specification.
> 
> 1. Multipoint (mesh) usage at small scale — API considerations
> 
> In one of my projects, I implemented a small-scale multipoint architecture (3–6 participants) using pure mesh with RTCPeerConnection.
> From a spec perspective, I’m trying to understand:
> 
> a) Is the current API surface intended to fully support small multipoint scenarios via mesh, or are users implicitly expected to move toward SFU architectures for stability?
> 

The current API should work for the usecase. TURN servers may be needed to ensure connection between peers.
> b) Are there known areas in the spec where multipoint mesh creates edge cases (e.g., SDP negotiation sequencing, glare handling, ICE restarts across multiple peers) that the WG considers out-of-scope for further improvements?
> 
I am not aware of issues, except maybe the case of ICE candidate restrictions in case camera/microphone is not granted.

> c) Would the WG be open to documented guidance or non-normative notes addressing best practices for small multipoint topologies built purely on top of the standardized API?
> 
> Mesh clearly works today, but in practice developers tend to rebuild custom logic around negotiation and connection orchestration.
> Clarifying the WG’s position would help tool authors (including myself) understand the intended use boundary.
> 
I am not aware of documents like this owned by the WG.


> 
> 2. Large-file peer-to-peer transfer over DataChannels (>4 GB)
> 
> My second project involves peer-to-peer transfer of large files using a reliable DataChannel with chunking.
> During testing, several limitations surfaced:
> 
> a) Transfers above ~4 GB fail or stall
> 
> Across Chromium-based browsers, transfers of very large files tend to hang or terminate prematurely.
> Is the specification expecting any implicit limitation (buffering, internal SCTP behavior, memory pressure, congestion control) that implementers must follow?
> 

This looks like implementation restrictions, filing bugs is probably the way to go go.

> b) Is there a recommended approach (from a WebRTC API standpoint) when handling long-lived DataChannels transporting high-volume data?
> 
> For example:
> 
> aggressive backpressure management?
> 
> limiting RTCDataChannel bufferedAmount?
> 
> recommended pacing strategies?
> 
> The current spec gives implementers freedom, but guidance or non-normative notes might be beneficial for interoperability.
> 

Working with implementors first seems the right approach to diagnose the issue you are facing.

> 
> 3. iOS / Safari DataChannel interop issues
> 
> During testing with Safari/iOS, even small file transfers (few MB) frequently fail.
> 
This looks like an implementation restriction or a bug.
> I understand that WebKit’s WebRTC implementation is still evolving, but I’d like clarification on:
> 
> a) Are there known interop limitations for DataChannel reliability on iOS that the WG officially tracks?
> 
> b) Would contributions documenting these failures (logs, reproducible tests, etc.) be useful to the WG or should they be directed exclusively to WebKit’s bug tracker?
> 
> I am willing to provide reproducible test cases if they can help move discussions forward.
> 
It would be great if you could provide reproducible test cases. Filing bugs at https://bugs.webkit.org <https://bugs.webkit.org/> for iOS WebKit is one way to provide such feedback.

> 
> Closing
> 
> I’d be happy to contribute additional implementation feedback, tests, or clarifications based on my experience with:
> 
> multipoint mesh call setups,
> 
> chunked high-volume DataChannel transfers,
> 
> Safari/iOS interoperability issues.
> 
> Thank you for maintaining this specification and for your guidance.
> 
> Best regards,
> Yvan Ngoudjou
>