Subject: [tsvwg] Some comments on NQB (part 2)

From: Gorry Fairhurst <[email-masked]>
Date: Fri, 18 Mar 2022 19:22:56 +0000

2) I have been reflecting on the text in 4.3, largely because I have 
prodded to think what DSCPs can still be assigned for useful work.

There are some aspects of this text that still concern me, and I think 
this revolves around the use of which key words are used with which 
actions around the DSCPs. I don't think this is hard, but

2a) advocates remarking 45 to 5 at the edge
"To facilitate the default treatment of NQB traffic in backbones and 
core networks discussed in the previous section (where IP Precedence may 
be deployed), networks that support NQB SHOULD NOT use the value 45 for 
NQB at network interconnects unless that usage is explicitly documented 
in the TCA (Traffic Conditioning Agreement, see[RFC2475 
<about:blank?compose#RFC2475>]) for that interconnection."

- I want to know if the SHOULD is considered important? The impact is 
that this draft recommends remarking to deploy NQB. I now that some 
paths/policies might have this result anyway and aggregate all traffic 
with the same high-orde 3-bit values.

2b) The section has text that goes on to talk about ToS-based precedence:

Furthermore, in other network environments where IP Precedence ([RFC0791 
<about:blank?compose#RFC0791>]) is deployed, it is RECOMMENDED that the 
network operator re-mark NQB traffic to DSCP 5 in order to ensure that 
it is aggregated with Default traffic.

- is that remarking necessary to achieve the goal of being aggregated 
with Default traffic? or could it be optional when it leaves the edge?

- to me this practice is deprecated, so why would the IETF perpetuate 
that? - would the WG consider to just call these networks out as taking 
a non-standards approach.

2c) And in balance, advocates remarking 5 to 45 at the edge:

In order to enable interoperability with WiFi equipment as described 
inSection 8.3.1 <about:blank?compose#wifi_interop>, networks SHOULD 
re-mark NQB traffic (e.g. DSCP 5) to DSCP 45 prior to a customer access 
link, subject to the safeguards described below and in that section.

- This is also in-network re-marking, which we should consider 
carefully, (e.g. when the edge is not clearly formed).

Perhaps we could try and make sure we are on the same same page this 
meeting?

Best wishes,

Gorry