[tsvwg] L4S CC-signaling and tunneling

[Sebastian Moeller <[e-mail]>]

Dear List,

after Bob's recent emphasis on L4S's conscious design to be operable with its AQM operating on tunneled traffic, I took the liberty to actually look at the three currently discussed L4S RFC drafts. All I found when searching for tunnel and/or encap* was the following in https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-06:

"6.3.4.  Other Potential Deployment Issues


   An L4S AQM uses the ECN field to signal congestion.  So, in common
   with Classic ECN, if the AQM is within a tunnel or at a lower layer,
   correct functioning of ECN signalling requires correct propagation of
   the ECN field up the layers [RFC6040],   [I-D.ietf-tsvwg-ecn-encap-guidelines]."


I am a bit puzzled how terse this description is given how much emphasis there seems to have been on making L4S congestion signaling work properly with tunnel layers. While I am loath to propose to inflate the L4S drafts any further, maybe some fat could be trimmed at other places to make some room for a more detailed description of the desired/required tunnel transition properties.


Best Regards
	Sebastian