Re: [tsvwg] COMMENT PLEASE: Which DSCP value should we use for LE PHB?

[Gorry Fairhurst <[e-mail]>]

On 07/07/2017, 12:03, Bless, Roland (TM) wrote:
> Hi Gorry,
>
> Am 07.07.2017 um 10:58 schrieb Gorry Fairhurst:
>> This email is intended to start a discussion about the most appropriate
>> DiffServ codepoint to assign to the LE PHB specified in:
>> https://tools.ietf.org/html/draft-ietf-tsvwg-le-phb-02
>>
>> The current list of available codepoints is listed by IANA here:
>> https://www.iana.org/assignments/dscp-registry/dscp-registry.xhtml
>>
>> The draft currently suggests using the DSCP value, '000010'.
> I think it is DSCP value 2.
That's two indeed:-).
>> Question 1: Is this codepoint a good choice for the TSVWG group to
>> assign for the LE PHB?
>>
>>    Things to consider:
>>      - Is the codepoint currently being used for other (non-standard
>> applications) that may get in the way of the deployment of the LE PHB?
> Currently, nothing should be using a non-assigned Standard DSCP.
> I really don't like these discussion along the lines of: oh, probably
> there are some standard-ignoring boxes/apps out there, so lets try to
> work around their broken design. So, yes, it's probably good to know,
> but IMHO it's better to get this other stuff fixed rather than to always
> create workaround.
And, I think a more usedful disucssion here is around - "what happens 
when you use existing codepoints that are IETF-approved, and they pass 
through the current Internet" - do they emerge as the codepoint you propose?

>>      - Is there ant evidence that this DSCP value is less likely to be
>> forwarded than other unused codepoints?
>>      - Is this codepoint observed in the wild due to common DSCP-mangling
>> pathologies (such as ToS-byte bleaching)?
>>
>> Question 2: Is there an alternate unassigned codepint that could be
>> chosen that would give better opprotunities for deployment?
>>      Things to consider:
>>      - A codepoint less than 7 appears to have less chance of
>> DSCP-mangling pathologies (such as ToS-byte bleaching)
>>      - IANA currently allocates from pool 1 (xxxxx0), but we could
>> consider asking to use pool 3 ('xxxx01'), e.g., '000001'or '000101'.
> I don't see any compelling reason to start using another pool right now.
Don't you? I think this depends on the outcome.
>> Measurement experience and thoughts on this topic are welcome on the
>> mailing list ahead of the TSVWG meeting. At this meeting, I would like
>> to see some discussion confirming the choice of DSCP codepoint or
>> suggesting a more appropriate codepoint for the working group to request.
> Thanks for triggering the discussion.
>
> Regards,
>   Roland
Roland, do you have any measurement data?

Gorry