[Webtransport] Re: [Interop] Public WebTransport Test Server (PyWebTransport)

[lemonsterfy <[e-mail]>]

Hi Alan,

The Devious Baton endpoint is now live.

- Endpoint: https://interop.wtransport.org/webtransport/devious-baton
- Spec Compliance: draft-frindell-webtrans-devious-baton-00
  <https://datatracker.ietf.org/doc/draft-frindell-webtrans-devious-baton/>

Implementation Notes
This deployment runs on our newly refactored Rust protocol core
(v0.13.0). Key implementation behaviors include:

- Flow Control: Immediate session termination (DA_YAMN) upon credit
violation [Section 4.1].
- Payloads: Randomized padding generation and validation [Section 4.3].
- State Machine: Strict enforcement of stream type transitions
(Uni/Bidi) [Section 4.2].
- Validation Scope: Predictive baton validation is waived for
Peer-Initiated Bidirectional Streams. Deterministic stream correlation
in concurrent (`count > 1`) scenarios requires auxiliary state
tracking. To preclude false positives, the server validates payload
format but accepts the peer-provided baton value.
- Datagram MTU: The requirement to echo an identical baton message
[Section 4.4] conflicts with Path MTU limits if the peer sends
extensive padding [Section 4.3]. In such cases, our server suppresses
the datagram response to adhere to transport constraints.

The Devious Baton protocol proves highly effective for verifying
concurrent stream logic and flow control accounting.

Verification
To facilitate testing, we provide a standalone client compatible with
draft-ietf-webtrans-http3-14 and latest WG consensus:
<
https://github.com/wtransport/pywebtransport/blob/main/examples/interop/tests/test_devious_baton.py
>

We welcome any interoperability feedback.


Best regards,

lemonsterfy
On behalf of The WTransport Authors
On Tue, Jan 6, 2026 at 1:07 PM lemonsterfy <[e-mail]> wrote:
>
> Hi Alan,
>
> Thank you for the suggestion. We recognize the value of the Devious
> Baton protocol (draft-frindell-webtrans-devious-baton-00) for
> verifying flow control accounting and stream concurrency management.
>
> We will deploy this endpoint on our public interop server to
> facilitate broader interoperability testing.
>
> Our implementation will strictly adhere to the draft's semantics:
>
> * **Endpoint Path:** Exposed at `/webtransport/devious-baton` as
> recommended [Section 3].
> * **Flow Control:** We will enforce strict credit checks. Sessions
> will be terminated with the `DA_YAMN` (0x01) error code upon stream
> limit violations, rather than blocking [Section 4.1].
> * **Stream Logic:** Baton passing will be handled based on strict
> stream type and initiator derivation rules [Section 4.2].
>
> We will notify the Working Group once the endpoint is available.
>
> Best regards,
>
> lemonsterfy
> On behalf of The WTransport Authors
>
> On Tue, Jan 6, 2026 at 5:30 AM Alan Frindell <[e-mail]> wrote:
> >
> > Hi, this is great!.  Is it possible to add a devious-baton endpoint as
well?
> >
> >
https://www.ietf.org/archive/id/draft-frindell-webtrans-devious-baton-00.html
> >
> > Thanks
> >
> > -Alan
> >
> > On 1/5/26, 11:03 AM, "lemonsterfy" <[e-mail] <mailto:
[e-mail]>> wrote:
> >
> >
> >
> > Hello WG,
> >
> >
> > We have deployed a public WebTransport test server running
PyWebTransport.
> >
> >
> > This endpoint tracks draft-ietf-webtrans-http3-14 and the latest
> > Working Group consensus to facilitate protocol compliance
> > verification.
> >
> >
> > Infrastructure
> >
> >
> > * Public Instance:
https://urldefense.com/v3/__https://interop.wtransport.org__;!!Bt8RZUm9aw!9xqW44OpaWPOdjJpdyJF3byvS5P0h_kM157vmR-MHzocJfQG02-3tI1DLCfRpc3T5YKnYrBJ9hLkR9M$
<
https://urldefense.com/v3/__https://interop.wtransport.org__;!!Bt8RZUm9aw!9xqW44OpaWPOdjJpdyJF3byvS5P0h_kM157vmR-MHzocJfQG02-3tI1DLCfRpc3T5YKnYrBJ9hLkR9M$>
(IPv4 / IPv6 Dual-Stack)
> > * OCI Image: ghcr.io/wtransport/interop-server:latest (UDP 4433)
> >
> >
> > Endpoints
> >
> >
> > * /echo: Bidirectional stream and datagram reflection.
> > * /stats: Session statistics and negotiated transport parameters (JSON).
> > * /status: Global server health metrics.
> >
> >
> > We welcome interoperability reports from other client implementations.
> >
> >
> > Best regards,
> >
> >
> > lemonsterfy
> > On behalf of The WTransport Authors
> >
> >
> > --
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> >
> >