Re: [aqm] I-D Action: draft-ietf-aqm-recommendation-04.txt

[Simon Barber <[e-mail]>]

Hi Mikael,

I can't find reference to DSCP 000010 or 000110, where are they defined?

I know the title 'assured forwarding' seems to imply better than best 
effort, but I think this is a mistake for AF1 - which seems to be 
recommended for bulk traffic that is not latency sensitive. You can't 
make everything high priority! I believe AF1 according to the list of 
recommended applications, would be better served at less than best 
effort priority - so the 4 queue 1a mapping based on the top 3 bits of 
the TOS byte would be OK. AF2 -> lower than best effort would be wrong 
however.

Simon


On 5/13/2015 1:47 AM, Mikael Abrahamsson wrote:
> On Tue, 12 May 2015, Simon Barber wrote:
>
>> Hi John,
>>
>> Where would be the best place to see if it would be possible to get 
>> agreement on a global low priority DSCP?
>
> Currently the general assumption among ISPs is that DSCP should be 
> zeroed between ISPs unless there is a commercial agreement saying that 
> it shouldn't. This is generally accepted (there are NANOG mailing list 
> threads on several occasions in the past 5-10 years where this was the 
> outcome).
>
> The problem is quite complex if you actually want things to act on 
> this DSCP value, as there are devices with default behaviour is 4 
> queue 802.1p, with 1 and 2 (which will match AF1x and AF2x) will have 
> lower priority than 0 and 3 (BE and AF3x), and people doing DSCP based 
> forwarding, usually does things the other way around.
>
> It might be possible to get the last DSCP bits to map into this, 
> because for DSCP-ignorant quipment, this would still be standard BE to 
> something only looking at CSx (precedence), but that would be lower 
> than 000000. So DSCP 000110 (high drop BE) might work, because it's 
> incremental. Possibly DSCP 000010 (low drop BE) might be able to get 
> some agreement because it doesn't really cause any problems in the 
> existing networks (most likely) and it could be enabled incrementally.
>
> I would suggest bringing this kind of proposal to operator 
> organizations and the IETF. It needs to get sold to the ISPs mostly, 
> because in this aspect the IETF decision will mostly be empty 
> hand-waving unless the operators do something.
>