Intent to Experiment: Reverse Origin Trial for WebRTC's Plan B SDP semantics

[Henrik Boström]

Contact emails

hb...@chromium.org, h...@chromium.org

Spec

WebRTC is a W3C Recommendation and multiple IETF standards:

https://www.w3.org/2021/01/pressrelease-webrtc-rec.html.en

https://www.w3.org/TR/webrtc/

https://tools.ietf.org/html/rfc8829

The Session Description Protocol (SDP) used by WebRTC currently has two implementations:

• "Unified Plan", the spec-compliant SDP format implemented by all browsers.
• "Plan B", the non-standard SDP format that does not have a spec, is deprecated but not yet removed and is only implemented in Chromium-based browsers. JavaScript applications have access to it by using a non-standard API.

Summary

We want to remove the non-standard SDP format, "Plan B", from Chromium. Removal dates have already been announced, but in order to aid applications from migrating from Plan B to Unified Plan and to ensure we can keep the deadlines we have set, a Reverse Origin Trial is desired to give applications that opt-in more time to migrate.

Deadlines and rationale for Reverse Origin Trial were provided in the intent to deprecate. The target dates are:

• M89 (Stable in February, 2021): Deprecation warning is added in the developer console.

• M93 (Stable in August, 2021): Plan B is removed, with the option to extend this deadline by opting-in to a Reverse Origin Trial.

• M96 (Stable in January, 2022): The extended deadline ends and Plan B is removed for everybody.

I would like to make the Reverse Origin Trial available as of M90 or M91 (when this CL lands).

Goals for experimentation

Unblock Plan B removal.

Experiment timeline

M90-M96.

Any risk when the experiment finishes?

If Plan B is removed while still in use, some applications would experience incompatibility issues when attempting to set up audio or video channels, especially in multi-participant conferencing setups. 1:1 calling will still work for some applications.

Ongoing technical constraints

N/A. There were some Unified Plan bugs and performance issues discovered that have been addressed in M90.

Debuggability

When using Plan B you will get a deprecation warning in the JS console. It will look different depending on if you have opted in to the Reverse Origin Trial.

Will this feature be supported on all five Blink platforms supported by Origin Trials (Windows, Mac, Linux, Chrome OS, and Android)?

Yes.

Link to entry on the feature dashboard

N/A, Unified Plan was shipped several years ago. Should I create an entry even for the Reverse Origin Trial?

[Philip Jägenstedt]

LGTM per the plan in the Intent to Deprecate.

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[Joe Medley]

"Should I create an entry even for the Reverse Origin Trial?"

Yes, you should.

Joe Medley | Technical Writer, Chrome DevRel | jme...@google.com | 816-678-7195

If an API's not documented it doesn't exist.

[Joe Medley]

To be clear, Chrome Status isn't extra. It's a tool for creating intents and it tries to help you get everything needed for that. The option for Feature deprecation contains a stage for a reverse origin trial.

Joe Medley | Technical Writer, Chrome DevRel | jme...@google.com | 816-678-7195

If an API's not documented it doesn't exist.

[Henrik Boström]

OK, I filed https://www.chromestatus.com/feature/5823036655665152

[Joe Medley]

Thank you!

Joe Medley | Technical Writer, Chrome DevRel | jme...@google.com | 816-678-7195

If an API's not documented it doesn't exist.

[Henrik Boström]

Usage limits are not applied to Deprecation Trials so even if usage exceeds 0.5% this would not affect being able to use Plan B if opted in to the trial.

On Thu, Jul 8, 2021 at 12:29 PM Yash Gogia <yrg...@gmail.com> wrote:

Hi,

The guide that talks about origin trials, mentions that there is a built-in safeguard that automatically disables an experimental feature globally if its usage exceeds 0.5% of all Chrome page loads. 

Source: https://github.com/GoogleChrome/OriginTrials/blob/gh-pages/developer-guide.md#3-what-happens-if-a-large-site-such-as-a-google-service-starts-depending-on-an-experimental-feature

I would like to understand if this applies to reverse origin trials as well. From chrome status, it looks like the usage is hovering around 0.2% already and I am sure many more websites would add the trial as the August date for Chrome 93 approaches. A confirmation that this automatic cutoff would not apply to the reverse origin trial would give us a lot more confidence.

Thanks,
Yash

[Yash Gogia]

Hi,

The guide that talks about origin trials, mentions that there is a built-in safeguard that automatically disables an experimental feature globally if its usage exceeds 0.5% of all Chrome page loads. 

Source: https://github.com/GoogleChrome/OriginTrials/blob/gh-pages/developer-guide.md#3-what-happens-if-a-large-site-such-as-a-google-service-starts-depending-on-an-experimental-feature

I would like to understand if this applies to reverse origin trials as well. From chrome status, it looks like the usage is hovering around 0.2% already and I am sure many more websites would add the trial as the August date for Chrome 93 approaches. A confirmation that this automatic cutoff would not apply to the reverse origin trial would give us a lot more confidence.

Thanks,
Yash

On Friday, 5 March 2021 at 23:18:03 UTC+5:30 Joe Medley wrote:

[Abhi Shanmu]

Hi,

I am unable to find reverse origin trial listed in this page for me to register. 
https://developer.chrome.com/origintrials/#/trials/active

How can I register my domains for the reverse origin trial?

Thanks,

Abhi

[Mike Taylor]

Hi Abhi,

Assuming you're looking for the deprecation trial ("reverse origin trial") for Plan B SDP semantics, https://developer.chrome.com/origintrials/#/view_trial/3892235977954951169 should be the right link.

(there's no visual differentiation between regular and deprecation trials in the UI, but maybe that would be a nice feature to add)

later,

Mike

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/02d760be-eea7-45f5-943e-bfc04a16bb56n%40chromium.org.

[Web Development]

I registered for  RTCPeerConnection Plan B SDP Semantics   and everything working fine in windows and android chrome browser.
But  in android webView it showing Origin trial "UNKNOWN ValidTokenNotProvided"
Does it support in android system webview?

[V Chang]

[Urgent Support]

Hi, 

Is there any possibility to extend the Trial for RTCPeerConnection Plan B SDP Semantics?

We are helping our client on the call center video solution. However, we have a big issue regarding this trial support end on May 25th 2022.  Please advise. Thank you for your support in advance.

Web Development 在 2021年12月17日 星期五上午12:22:55 [UTC+8] 的信中寫道：

[Henrik Boström]

UMAs show Plan B usage is down to 0.00000473% and we already extended the deprecation trial by 6 months for those who did not notice the 1 year warning/canary exception prior to that. Because of this, support for Plan B including the Plan B deprecation trial flag was removed in M102 which is currently Beta and soon getting its Stable cut.

Big issue? Are you not able to migrate in time?

[V Chang]

Hi Henrik,

Yes. We have an big issue on fixing the problem to run without this trial, which will cause our end users not be able to make video call to call center for banking service. 
We are still working on fixing the problem. However, we cannot make it before May 25th. Is there any alternative? Thanks!

Henrik Boström 在 2022年5月12日 星期四下午2:26:43 [UTC+8] 的信中寫道：

[Eric Liao]

Hi,

Continue V Chang's Problem.

Our video system still uses Plan B SDP, and we find that if we use chrome(M89), the video still can work normally now
So, if we don't upgrade the browser, will it be affected after May 25th?
It's very important for us, I am looking forward to your reply, thank you!

V Chang 在 2022年5月13日 星期五上午12:59:28 [UTC+8] 的信中寫道：

[Henrik Boström]

> Our video system still uses Plan B SDP, and we find that if we use chrome(M89), the video still can work normally now

> So, if we don't upgrade the browser, will it be affected after May 25th?

That's correct, in M89 Plan B was always allowed and the Deprecation Trial did not exist yet. So even after the trial ends, M89 will still continue to support Plan B.

The deprecation/removal of Plan B only affects more recent versions than that.

> However, we cannot make it before May 25th. Is there any alternative? Thanks!

It's not possible to extend the trial because the M102 stable release candidate does not contain the deprecation trial flag anymore. To be clear:
- In M101, attempting to set sdpSemantics to "plan-b" without a trial or after the trial has ended throws an exception.

- In M102, sdpSemantics is ignored and you get "unified-plan" even if you ask for "plan-b" (regardless of trial status). M102 stable release is scheduled for May 24, rollout happens gradually.

So there will be no way of getting Plan B on recent versions using any API.

Incidentally, you can still change the default SDP semantics (what you get when it is not overriden by the sdpSemantics API) using a command line flag if you're launching Chrome from a command line:

--disable-features=RTCUnifiedPlanByDefault

Obviously this is not something normal web users would do (and it would affect all websites) so I'm not sure this helps, but FYI that exists in case you're in control of the user's environment.

Also as a side note - the exact removal timeline is a little different on CrOS than other platforms due to a bug in a dependency, but CrOS is also sensitive to trial ending and the trial not existing in M102. More info at https://crbug.com/1327544.