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

[<[e-mail]>]

Gorry, 

Some new comments at the end.

Ruediger
RG>  DSCP 000001 might be an option. No other IETF recommended DSCP 
is re-marked to this one. It is to some extent RFC4594 compatible and 
RFC8100 could cope with it if default transport is applied.

Fred
FB> https://tools.ietf.org/html/rfc2474#section-6 indicates that 000001 
is experimental/local use, available for standards allocation only as necessary.
4597> "We RECOMMEND that the DSCP value(s) of the unsupported service class 
4597> be changed to 000xx1 on ingress and changed back to original value(s) 
4597> on egress..."

Brian
BC > That is a local use within a domain, completely compatible with both 
BC > pools 2 and 3 which are both defined as for local use. So 000001 is 
BC > really not suitable for standards track recommendation, until pool 1 
BC > is full.
....
BC> 000010 is just fine. Why are we still discussing this?

Gorry
GF>....there is reasonable doubt that a LE service can be safely deployed
across the Internet using a codepoint of 000010.

GF> There seems evidence that there are still even now deployed routers 
that have not adjusted their remarking behaviour after the IETF 
deprecated ToS Precedence bleaching. 

[RG2] True. I prefer a core-router to be able to re-mark DSCPs by bit-mask at  
interconnection interfaces rather than DSCP by DSCP. The config effort to customize 
re-marking on a DSCP by DSCP basis is high. An easy to configure alternative is to classify 
by bit-mask and re-mark to a single DSCP. Gorry, do you have any preference here?

GF>....A packet that uses AF marking and encounters ToS Precedence bleaching 
would expereince AF11, AF21, AF31, AF41 emerging remarked to a codepoint 
of 000010, and AF12, AF22, AF32, AF42, VA would emerge as 000100, etc.

GF> Because the LE PHB is a lower effort PHB, implementing a PHB with a codepoint 
of 000010 would result in some traffic originally marked as AFx1 being assigned a 
lower effort than AFx1 or AFx2. 

[RG2] That's a reasonable analysis. A network sending various DSCP into my domain 
without informing my NOC or setting up an SLA is not conservative with what it sends 
in my eyes. If receiving networks are expected to be supportive rather than liberal only 
in that case and are expected to maintain the original Diffserv coding sense of a 
non-cooperative sender, as described by Gorry, I think DSCP 000001 for LE is a good 
choice. That allows to maintain bit-mask based re-marking while maintaining the original 
Diffserv intent of non-cooperative networks, so I ignored the pools. 

Regards, Ruediger