Re: [tsvwg] CC/bleaching thoughts for draft-ietf-tsvwg-le-phb-04

["Bless, Roland (TM)" <[e-mail]>]

Hi Mikael,

Am 19.04.2018 um 12:52 schrieb Mikael Abrahamsson:
> On Thu, 19 Apr 2018, Bless, Roland (TM) wrote:
> 
>> Ok, so _bleaching_ for me would be to set the DSCP to 0. The subsequent
> 
> Ok, what should I call the following (all values decimal for the 6 DSCP
> CP bits)
> 
> Look at diffserv CP values 0-63.
> If CP in range 2-63, SET CP=0
> If CP == 1 pass unchanged
> If CP == 0 pass unchanged
> 
> This bleaches 2-63 to 0 and leaves 1 unchanged. What do we call this?

This is correctly stated, so I would always qualify bleaching with
the respective DSCPs that are bleached.

>> This is a bit confusing. What do you mean by "bleach" here, treat
>> LE as BE? Remarking of DSCPs is a somewhat orthogonal problem since
> 
> For me there are two things an ISP does depending on DSCP values. It has
> a policy that (might) inspect CP values and change them. It also has a
> PHB depending on the CP values.
> 
> The simplest policy is "SET CP = 0 on all packets". This seems to be
> what you call bleaching.

Yep.

>> Diffserv requires a flexible mapping from DSCP -> PHB. So my
>> recommendation is to remark CS1 to LE for domains that formerly used
>> CS1 as LE codepoint. Otherwise, you cannot be sure whether CS1 actually
>> is CS1 in its original meaning or whether it should be treated as LE.
>> Removing that ambiguity is the main motivation for my LE PHB draft.
> 
> If the domain previously just bleached everything and now wants to
> deploy support for LE (both allowing the CP to enter the ISP network and
> also creating different PHB for LE vs BE), what should it do regarding CS1?

> Saying "it depends" is not helpful. This is the Internet with billions
> of devices and users. What should be the default behaviour for
> non-managed devices run by normal people that they bought from the
> electronics store. I am not talking about managed enterprise networks
> etc. I am talking about the most common network out there, the "oh, I
> need Internet access to watch cat pictures on my own device and it's
> default out of box configured from DSCP point of view".

I think that Ruediger also stated that it depends on what was previously
the semantics of CS1 at that particular link. The problem is indeed at
app level, since there may be some apps using CS1 in LE semantics and
some probably in genuine CS semantics. So the choice is to map CS1->LE
or to bleach it unless you want to support genuine CS1. As a provider
it is your own risk and I think one could monitor the traffic volume.
If it is negligible, then using BE or elevated services for CS1 is no
problem, but otherwise this traffic may adversely affect other BE traffic.

>>> 3. Bleach rest to BE.
>>
>> What is the rest?
> 
> CP between 2 and 63. Not 0 and 1.

Ok, that is much more precise.

Regards
 Roland