Re: [tsvwg] severity of interaction between L4S and non-L4S flows (was: draft-ietf-tsvwg-l4sops-01.txt)

[Pete Heist <[e-mail]>]

Hi Greg,

Regarding the guidance for general purpose servers in Section 4:

---
*  Taking action based on the detection of RFC3168 FIFO
   bottlenecks is likely not needed for short transactional
   transfers (e.g. sub 10 seconds) since these are unlikely to
   achieve the steady-state conditions where unfairness has been
   observed.
---

Do you have any data to back up the sub 10 seconds threshold?

What we've seen is non-L4S flows yielding quickly to L4S flows in
RFC3168 queues. In this plot of Prague vs CUBIC in a single Codel
queue, the flows start at T=5 seconds, harm to CUBIC occurs almost
immediately, and CUBIC's steady state near minimum cwnd is reached 4-5
seconds after flow start:

https://sce.dnsmgr.net/results/l4s-2020-11-11T120000-final/l4s-s6-rfc3168-1q/l4s-s6-rfc3168-1q-ns-prague-vs-cubic-noecn-fq_codel-50Mbit-20ms_tcp_delivery_with_rtt.svg

We also posted a test showing the FCT harm to short flows by a single
long flow, where flow lengths for the short flows were taken from a
lognormal distribution with a P5 of 64KB and a P95 of 2MB:

https://github.com/heistp/ccafct#sample-output

Thanks,
Pete

On Mon, 2021-07-12 at 16:01 -0700, [e-mail] wrote:
> 
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> This draft is a work item of the Transport Area Working Group WG of the
> IETF.
> 
>         Title           : Operational Guidance for Deployment of L4S in
> the Internet
>         Author          : Greg White
>         Filename        : draft-ietf-tsvwg-l4sops-01.txt
>         Pages           : 21
>         Date            : 2021-07-12
> 
> Abstract:
>    This document is intended to provide guidance in order to ensure
>    successful deployment of Low Latency Low Loss Scalable throughput
>    (L4S) in the Internet.  Other L4S documents provide guidance for
>    running an L4S experiment, but this document is focused solely on
>    potential interactions between L4S flows and flows using the
> original
>    ('Classic') ECN over a Classic ECN bottleneck link.  The document
>    discusses the potential outcomes of these interactions, describes
>    mechanisms to detect the presence of Classic ECN bottlenecks, and
>    identifies opportunities to prevent and/or detect and resolve
>    fairness problems in such networks.  This guidance is aimed at
>    operators of end-systems, operators of networks, and researchers.
> 
> 
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-tsvwg-l4sops/
> 
> There is also an HTML version available at:
> https://www.ietf.org/archive/id/draft-ietf-tsvwg-l4sops-01.html
> 
> A diff from the previous version is available at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-tsvwg-l4sops-01
> 
> 
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
> 
>