Re: [tsvwg] Publication has been requested for draft-ietf-tsvwg-iana-dscp-registry-04
Gorry Fairhurst <gorry@erg.abdn.ac.uk> Wed, 09 May 2018 08:14 UTC
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Date: Wed, 09 May 2018 09:13:46 +0100
From: Gorry Fairhurst <gorry@erg.abdn.ac.uk>
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Subject: Re: [tsvwg] Publication has been requested for draft-ietf-tsvwg-iana-dscp-registry-04
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These request are all OK with me, and I have made the changes. The recent thread on the TSVWG list has made me wonder again whether it is possible for me to be slightly clearer about explaining the TOS precedence bleaching - without drilling into all the detail. This has always a nightmare to write concisely, but I think I may be able to do better, and if you agree, I would also incorporate the slightly longer replacement text below: OLD: An example is the need to assign a suitable recommended default codepoint for the Lower Effort (LE) per-hop behavior (PHB) [I-D.ietf-tsvwg-le-phb]. The LE PHB is designed to protect best-effort (BE) traffic (packets forwarded with the default PHB) from LE traffic in congestion situations, i.e., when resources become scarce, best-effort traffic has precedence over LE traffic and may preempt it. The continued presence of bleaching of the IP precedence field, setting the first three bits of the former TOS byte to zero (i.e., zeroing the top three bits of the DSCP) in deployed networks motivates the desire for the LE PHB to use a DSCP with a zero value for the first three bits [I-D.ietf-tsvwg-le-phb]. NEW: An example is the need to assign a suitable recommended default codepoint for the Lower Effort (LE) per-hop behavior (PHB) [I-D.ietf-tsvwg-le-phb]. The LE PHB is designed to protect best-effort (BE) traffic (packets forwarded with the default PHB) from LE traffic in congestion situations, i.e., when resources become scarce, best-effort traffic has precedence over LE traffic and is allowed to preempt it. The continued presence of bleaching of the IP precedence field in deployed networks can result in setting the first three bits of the former TOS byte to zero (disabling any class-based flow management by routers configured with TOS-based packet processing). There is a need to avoid this remapping of the DSCP for the LE PHB by assiging a codepoint that has a zero value in the first three bits [I-D.ietf-tsvwg-le-phb]. Furthermore, if the LE PHB were to have been assigned one of the currently unused Pool 1 codepoints with a zero value in the first three bits, any bleaching of the IP precedence field would result in other (higher assurance) traffic being remapped to the assigned DSCP. This remapping could then cause diffserv-marked traffic to receive an unintentional LE treatment for the remainder of the Internet path. It is therefore important to avoid the resulting priority inversion. The absence of unassigned codepoints in Pool 1 that exhibit these important properties motivates assigning a Pool 3 codepoint as the default that is recommended for use with this PHB. --- - Your thoughts please, I'll hold publishing the new revision until I hear from you, Gorry On 09/05/2018, 06:18, Spencer Dawkins at IETF wrote: > On Tue, May 8, 2018 at 9:00 AM, David Black <david.black@dell.com > <mailto:david.black@dell.com>> wrote: > > David Black has requested publication of > draft-ietf-tsvwg-iana-dscp-registry-04 as Proposed Standard on > behalf of the TSVWG working group. > > Please verify the document's state at > https://datatracker.ietf.org/doc/draft-ietf-tsvwg-iana-dscp-registry/ > <https://datatracker.ietf.org/doc/draft-ietf-tsvwg-iana-dscp-registry/> > > > I have a couple of comments, but this draft is ready for Last Call. > Could you take a look at my comments, and let me know what the right > thing to do is? > > Thanks! > > Spencer > > There's a reference to > https://tools.ietf.org/html/rfc8126#section-4.9 in the Introduction, > but that text uses "Standards Action" with the reference but without > any expansion, while further down, the next occurrence of "Standards > Action" explains that this means "values are assigned by Standards > Track or Best Current Practice RFCs", without providing a reference. > Perhaps expanding > These are assigned by > Standards Action, as defined in [RFC8126]. > > to read > > These are assigned by > Standards Action, as defined in [RFC8126], i.e., values are assigned > by Standards Track or Best Current Practice RFCs > > and dropping the expansion from the second mention would be clearer? > > Independent of that question, I had to read through the text > containing the second mention a couple of times. > > Although Pool 1 has not yet been completely exhausted, this document > changes the IANA registration policy of Pool 3 to assignment by > Standards Action, i.e., values are assigned by Standards Track or > Best Current Practice RFCs. The rationale for this update is a need > to assign codepoints for particular PHBs that are unable to use any > of the unassigned values in Pool 1. > > Would it be correct to say > > Although Pool 1 has not yet been completely exhausted, there is a need > to assign codepoints for particular PHBs that are unable to use any > of the unassigned values in Pool 1. This document > changes the IANA registration policy of Pool 3 to assignment by > Standards Action, i.e., values are assigned by Standards Track or > Best Current Practice RFCs, allowing these codepoints to be assigned. > > ?
- [tsvwg] Publication has been requested for draft-… David Black
- Re: [tsvwg] Publication has been requested for dr… Spencer Dawkins at IETF
- Re: [tsvwg] Publication has been requested for dr… Gorry Fairhurst
- Re: [tsvwg] Publication has been requested for dr… Spencer Dawkins at IETF
- Re: [tsvwg] Publication has been requested for dr… Spencer Dawkins at IETF