[Bloat] [Ecn-sane] [iccrg] Fwd: [tcpPrague] Implementation and experimentation of TCP Prague/L4S hackaton at IETF104

Roland Bless roland.bless at kit.edu
Sat Mar 23 15:55:41 EDT 2019

Hi Michael,

thanks for the pointer. Looking forward to the talk...


On 23.03.19 at 18:48 Michael Welzl wrote:
> Hi,
> I’ll do what academics do and add our own data point, below:
>> On Mar 23, 2019, at 4:19 PM, Roland Bless <roland.bless at kit.edu
>> <mailto:roland.bless at kit.edu>> wrote:
>> Hi Mikael,
>> On 23.03.19 at 11:02 Mikael Abrahamsson wrote:
>>> On Sat, 23 Mar 2019, Roland Bless wrote:
>>>> I suggest to use an additional DSCP to mark L4S packets.
>>> DSCP doesn't work end-to-end on the Internet, so what you're suggesting
>>> isn't a workable solution.
>> It's true that DSCPs may be remarked, but RFC 2474
>> already stated
>>   Packets received with an unrecognized codepoint SHOULD be forwarded
>>   as if they were marked for the Default behavior (see Sec. 4), and
>>   their codepoints should not be changed.
>> The rtcweb WG also counts on e2e DSCPs.
>> After the LE PHB experience I would suggest to probably use
>> DSCP 5 which has got better chances to survive ToS bleaching (maybe
>> around 80%), if I understand
>> https://www.sciencedirect.com/science/article/pii/S0140366417312835
>> correctly. Diffserv behavior is usually configurable and can be changed
>> without replacing the network gear.
> Runa Barik, Michael Welzl, Ahmed Mustafa Elmokashfi, Thomas Dreibholz,
> Stein Gjessing: "Can WebRTC QoS Work? A DSCP Measurement Study", 30th
> International Teletraffic Congress (ITC 30), 3 - 7 September 2018,
> Vienna, Austria.
> https://itc-conference.org/_Resources/Persistent/780df4482d0fe80f6180f523ebb9482c6869e98b/Barik18ITC30.pdf
> We didn’t measure undefined codepoints though, only EF, AF42 and CS1.
> Table 2 compares bleaching for these codepoints with the results in the
> paper you point to; it’s quite similar.
> Well yes, there’s a significant amount of bleaching, we can’t deny that.
> But sometimes the codepoint survives, and it seems to survive
> surprisingly long into the path (fig.4 in our paper).
> In the MAPRG session in Prague, Runa Barik will give a talk about the
> measured delay impact of such opportunistic use of these DSCP values by
> an end system.
> Cheers,
> Michael

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