[tsvwg] Re: 5G+ Ultra (aka L4S)

[Sebastian Moeller <[e-mail]>]

Hi Ingemar,


> On 27. Apr 2026, at 10:56, Ingemar Johansson S <ingemar.s.johansson=[e-mail]> wrote:
> 
> Some additional
> 
> Accurate ECN is only applicable for TCP based (Prague) flows. 
> Facetime runs RTP/UDP and use, I think but aint sure, RFC8888 for the feedback. 
> I don't know about GFN.
> QUIC supports ECN feedback in the ACK frames but I am not aware of QUIC applications that are L4S capable. 


Thanks, indeed what I wanted to ask is really, is the service restricted to the enumerated devices and if so how is that implemented?

Regards
	Sebastian

> 
> Page 6 in the presentation below outlines how to run chrome canary with L4S support
> https://datatracker.ietf.org/meeting/125/materials/slides-125-ccwg-scream-v2-01

Sweet! Thanks a lot.

Regards
	Sebastian

> 
> /Ingemar
> 
>> -----Original Message-----
>> From: Sebastian Moeller <moeller0=[e-mail]>
>> Sent: Monday, 27 April 2026 10:30
>> To: Ruediger.Geib=[e-mail]
>> Cc: moeller0=[e-mail]; [e-mail]; [e-mail]
>> Subject: [tsvwg] Re: 5G+ Ultra (aka L4S)
>> 
>> Hi Ruediger,
>> 
>> 
>>> On 27. Apr 2026, at 10:24, Ruediger.Geib=[e-mail]
>> wrote:
>>> 
>>> Hi Sebastian,
>>> 
>>> while I certainly support and supported that development by communicating
>> standardization results, I've been involved by profession only where the network
>> section I work on - IP/MPLS core - plays a role: prove, that it doesn't change IP
>> ECN codepoints of transiting traffic. I can't reliably answer mobile edge related
>> questions, and I won't do technology related guesswork related to a commercial
>> deployment of another Deutsche Telekom branch .
>>> 
>>> All I can offer is a link to a whitepaper published, when Deutsche Telekom and
>> Ericsson started this activity:
>>> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.
>>> 
>> telekom.com%2Fresource%2Fblob%2F628056%2Fdb8412520298f03744f938dc3
>> 3b0d
>>> c9a%2Fdl-210526-whitepaper-
>> data.pdf&data=05%7C02%7Cingemar.s.johansson
>>> 
>> %40ericsson.com%7C48d79583b6a84d7ba29308dea4376537%7C92e84cebfbfd
>> 47abb
>>> 
>> e52080c6b87953f%7C0%7C0%7C639128755026898789%7CUnknown%7CTWFp
>> bGZsb3d8e
>>> 
>> yJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiT
>> WF
>>> 
>> pbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=dUswHddXjNVZ7oRaNfJyDTS
>> zYfkCd
>>> WQbf%2FXLhiu0qfI%3D&reserved=0
>> 
>> 
>> Thanks a lot. Interesting, unsure how close this is to what is deployed right now,
>> but it can serve as basis to form hypothesis to test.
>> 
>> Regards
>> Sebastian
>> 
>> 
>> 
>>> 
>>> Regards,
>>> 
>>> Ruediger
>>> 
>>> -----Ursprüngliche Nachricht-----
>>> Von: Sebastian Moeller <moeller0=[e-mail]>
>>> Gesendet: Montag, 27. April 2026 09:45
>>> An: Geib, Rüdiger <[e-mail]>
>>> Cc: [e-mail]; [e-mail];
>>> [e-mail]
>>> Betreff: Re: [tsvwg] 5G+ Ultra (aka L4S)
>>> 
>>> Hi Ruediger,
>>> 
>>> great to hear directly from close to the the source ;). I do have a few questions
>> that you might be able to shed some light on (or in-officialyl speculate on:
>>> 
>>> a) is 5g+ ultra a complete L4S system with AQMs on both the L-queue and the
>> C-queue?
>>> b) the mentioned network slice, is that only used for ECT(1) traffic?
>>> c) is ECT(1) really the relevant feature for traffic to end up in that network
>> slice or is this also filtered by application/IP-range?
>>> d) is the device side limit truly hard-filtered to the enumerated devices or are
>> these devices simply the only ones that support AccECN?
>>> 
>>> Regards
>>>       Sebastian
>>> 
>>> 
>>> 
>>>> On 27. Apr 2026, at 09:29, Ruediger.Geib=[e-mail]
>> wrote:
>>>> 
>>>> Hi Ingemar,
>>>> thanks...commercial roll out was more than a year ago in Germany (I think,
>> Gamescon 2024). T-Mobile US meanwhile supports L4S by 5G-SA too. Other
>> (mobile network) operators test L4S.   Apart from network operator gear,
>> terminating equipment and applications need to support L4S (AccECN and a
>> transport-protocol making use of it). For the time being that creates a certain
>> similarity of the supported applications by those network operators with
>> commercial L4S deployments (cable and mobile). It's not yet: turn on L4S on a
>> router and all interactive real-time app delays are gone...
>>>> Regards,
>>>> Ruediger
>>>> Von: Ingemar Johansson S
>>>> <ingemar.s.johansson=[e-mail]>
>>>> Gesendet: Freitag, 24. April 2026 13:43
>>>> An: tsvwg <[e-mail]>; [e-mail]
>>>> Betreff: [tsvwg] 5G+ Ultra (aka L4S)
>>>> As a FYI
>>>> L4S support in 5G is now definitely being rolled out
>>>> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww
>>>> .telekom.com%2Fen%2Fmedia%2Fmedia-information%2Farchive%2F5g-
>> ultra-fo
>>>> 
>> &data=05%7C02%7Cingemar.s.johansson%40ericsson.com%7C48d79583b6a84d
>> 7b
>>>> 
>> a29308dea4376537%7C92e84cebfbfd47abbe52080c6b87953f%7C0%7C0%7C63
>> 91287
>>>> 
>> 55026921423%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYi
>> OiIwL
>>>> 
>> jAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C
>> %7C
>>>> 
>> %7C&sdata=D4VLkpqdowE4OpUBkiDL%2B9cm6LXpCxIaIDdaInHWyq4%3D&rese
>> rved=0
>>>> r-video-calls-1104096 And for those who can, and wish to order the
>>>> new option.
>>>> https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww
>>>> .telekom.de%2Foptionsuebersicht%2Fmobilfunk%2F5gplus-
>> ultra&data=05%7C
>>>> 
>> 02%7Cingemar.s.johansson%40ericsson.com%7C48d79583b6a84d7ba29308dea
>> 43
>>>> 
>> 76537%7C92e84cebfbfd47abbe52080c6b87953f%7C0%7C0%7C6391287550269
>> 36932
>>>> 
>> %7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMD
>> AwMCIs
>>>> 
>> IlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata
>> =k
>>>> ArfEUcmAs4ba0w3R5UhsOnXyDLun4eqEt1Ts6TsktY%3D&reserved=0
>>>> 
>>>> /Ingemar
>>>> =================================
>>>> Ingemar Johansson  M.Sc. Master Researcher  Ericsson Research GFTL ER
>>>> NAP NCM Netw Proto & E2E Perf Laboratoriegränd 11
>>>> 977 53, Luleå, Sweden
>>>> [phone]
>>>> [e-mail]
>>>> http://www.ericsson.com/
>>>>      Experience is merely the name           men gave to their mistakes.
>>>>                    Oscar Wilde
>>>> =================================