[tsvwg] Re: WGLC for A NQB PHB for Differentiated Services (draft-ietf-tsvwg-nqb) to end 27th May 2024.

[Sebastian Moeller <[e-mail]>]

This section:

The NQB queue SHOULD be given equivalent forwarding preference compared to Default. The node SHOULD provide a scheduler that allows NQB and Default traffic to share the link in a manner that treats the two classes equally, e.g., a deficit round-robin (DRR) scheduler with equal weights, or two Wireless Multimedia Access Categories with the same channel access (EDCA) parameters. The use of equal weights for DRR is given as a reasonable example, and is not intended to preclude other scheduling weights (see below for details). A node that provides rate limits or rate guarantees for Default traffic SHOULD ensure that such limits and/or guarantees are shared with NQB traffic in a manner that treats the two classes equally. This could be supported using a hierarchical scheduler where the rate limits and guarantees are configured on a parent class, and the two queues (Default and NQB) are arranged as the children of the parent class and given equal access to the capacity configured for the parent class (e.g. with equal DRR scheduling). Compliance with these recommendations helps to ensure that there are no incentives for QB traffic to be mismarked as NQB.

seems confused. If the QB and NQB queues are schedules with equal weights as recommended, there is a clear incentive for QB traffic to always pick the queue with lower current traffic, as from the individual flow's perspective that will give most capacity (assuming a QB flow aims for highest capacity). The only remedy here is the shallow queue, but for a sufficiently paced flow that is not that big a hurdle...

It is IMHO not all that helpful to look at this as a difference between traffic classes, as long as any flow can decide (even while already active) to switch between the queues, simply by asserting the NQB DSCP or not. I wonder whether the assertion of a Nash equilibrium for QB traffic staying the QB queue is actually verifiably true. (I think we should think here in terms of Nash equilibria, as the idea 'no incentives for QB traffic to be mismarked as NQB' implies a game theoretic approach).


Regards
	Sebastian







> On 20. May 2024, at 09:41, Gorry Fairhurst <[e-mail]> wrote:
> 
> This email starts a 3 week WG Last Call to determine if the following TSVWG ID is ready:
> 
> https://datatracker.ietf.org/doc/draft-ietf-tsvwg-nqb/
> 
> This document targets: PROPOSED STANDARD.
> The document shepherd will be: Gorry Fairhurst.
> 
> The WGLC will end at midnight UTC on 10th June 2024 (2024-06-27)
> 
> Please do read the draft, and please send any comments/concerns to  the TSVWG mailing list, including notes on whether these are ready to publish (or send an email directly to the chairs<[e-mail]>).
> 
> Best wishes,
> Gorry and Marten
> (tsvwg co-chairs)
> 
> —
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> The IETF WG Last Call process is described in RFC 6174.
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