wdiff rfc8436.original rfc8436.txt

Transport Area Working Group
Internet Engineering Task Force (IETF) G. Fairhurst
Internet-Draft
Request for Comments: 8436 University of Aberdeen
Updates: 2474 (if approved) June 07, August 2018
Intended status:
Category: Standards Track
Expires: December 07, 2018
ISSN: 2070-1721

Update to IANA Assignment of DSCP Registration Procedures for Pool 3 (xxxx01) Values to require Publication of
a Standards Track or Best Current Practice RFC
draft-ietf-tsvwg-iana-dscp-registry-08 in the
Differentiated Services Field Codepoints (DSCP) Registry

Abstract

The Differentiated Services (Diffserv) architecture specifies use of
a
the DS field in the IPv4 and IPv6 packet headers to carry Diffserv
Codepoint one of 64
distinct differentiated services field codepoint (DSCP) values. The
Internet Assigned Numbers Authority (IANA) maintains a registry of
assigned DSCP values.

This update to RFC2474 RFC 2474 changes the IANA assignment registration policy for Pool
3 of the registry (i.e., DSCP values of the form xxxx01) to Standards
Action, i.e., values are assigned through a Standards Track or Best
Current Practice RFC. The update also removes permission for
experimental and Local Use local use of the Codepoints codepoints that form Pool 3 of the
DSCP registry; Pool 2 Codepoints (i.e., DSCP values of the form
xxxx11) remain available for these purposes.

Status of this This Memo

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provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on December 07, 2018.
https://www.rfc-editor.org/info/rfc8436.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The update Updates to RFC2474 . RFC 2474 . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
7.2.
6.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Revision Notes
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7

1. Introduction

The Differentiated Services (Diffserv) [RFC2475] architecture
(updated by [RFC3260]) provides scalable service differentiation in
the Internet. Diffserv uses the six most significant bits of the
former IPv4 Type of Service (TOS) octet or the former IPv6 Traffic
Class octet to convey the field, which is used to carry the Diffserv
Codepoint (DSCP). DSCP.
This DSCP value is used to select a Diffserv Per
hop Behaviour, PHB. per-hop behavior (PHB).

The six bit six-bit field is capable of conveying 64 distinct codepoints, and
this codepoint space has been divided into three pools for the
purpose of codepoint assignment and management (as shown in figure
Figure 1). Pool 1 comprises 32 codepoints [RFC2474]. These are
assigned by Standards Action, as defined in [RFC8126]. Pool 2
comprises a pool of 16 codepoints reserved for experimental Experimental or Local
Use (EXP/LU) as defined in [RFC2474], and [RFC2474]. Pool 3 comprises 16
codepoints, which were originally specified as "initially available
for experimental or local use, but which should be preferentially
utilized for standardized assignments if Pool 1 is ever exhausted" by
[RFC2474].

+------+-----------------+
| Pool | Codepoint Space |
+------+-----------------+
| 1 | xxxxx0 |
+------+-----------------+
| 2 | xxxx11 |
+------+-----------------+
| 3 | xxxx01 |
+------+-----------------+

Figure 1: Format of the field Field for codepoints allocated Codepoints Allocated in the
three Three
IANA pools (where 'x' refers Pools (Where "x" Refers to either '0' Either "0" or '1'). "1")

At the time of writing this document, 22 of the 32 Pool 1 codepoints
have currently been assigned.

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 Action.
(Section 4.9 of [RFC8126] defines this as "assigned only through
Standards Track or Best Current Practice RFCs in the IETF Stream"). Stream".)

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]. PHB [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 (when
resources become scarce, best-
effort best-effort traffic has precedence over LE
traffic and is allowed to preempt it). In deployed networks, there is continued use of
bleaching (i.e. intentionally setting to zero) of the IP precedence
field. Precedence
field continues to be used. (Setting the IP Precedence field to zero
disables any class-
based class-based flow management by routers configured with
TOS-based packet
processing). processing.) This causes the first three bits of
the former TOS byte (now the upper part of the DSCP field) to become
zero. There Therefore, there is
therefore a need to avoid this remapping of the DSCP
for the LE PHB by assigning a codepoint that already has a zero value
in the first three bits [I-D.ietf-tsvwg-le-phb]. [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 Precedence field would result in
other (higher assurance) traffic being also remapped to the assigned
DSCP. This remapping could then cause diffserv-marked Diffserv-marked traffic to
receive an unintentional LE treatment for the remainder of the
Internet path. It Therefore, 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.

To allow the IETF to utilise utilize Pool 3 codepoints, this document
requests IANA to to manage Pool 3 assignments for DSCP values in Pool 3
via the Standards Action policy [RFC8126].

2. Terminology

This document assumes familiarity with the terminology used in
[RFC2475] updated by [RFC3260].

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

3. The update Updates to RFC2474 RFC 2474

This document updates section Section 6 of [RFC2474], [RFC2474] in the following ways.

It updates the following text concerning the assignment policy:

OLD: which are initially available for experimental or local use,
but which should be preferentially utilized for standardized
assignments if Pool 1 is ever exhausted.

NEW: which are utilized for standardized assignments (replacing the
previous availability for experimental or local use).

It removes the footnote in RFC2474 RFC 2474 relating to Pool 3:

DELETE: "(*) may be utilized for future Standards Action allocations
as necessary"

The new registry assignment policy is shown in Figure 2.

Pool Codepoint space Space Assignment Policy
---- --------------- ------------------
1 xxxxx0 Standards Action
2 xxxx11 EXP/LU
3 xxxx01 Standards Action

Note for Pool 2: "Reserved for experimental Experimental or Local Use"

Figure 2: Updated Assignment Policy for the DSCP Registry

4. Security Considerations

Security considerations for the use of DSCP values are described in
the RFCs that define their usage. This document does not present new
security considerations.

5. IANA Considerations

This section requests

IANA to change has changed the use of Pool 3 in the DSCP "Differentiated Services
Field Codepoints (DSCP)" registry and to will manage this pool using
Standards Action, as defined as Section 4.9 of [RFC8126].

This requests

IANA to make has made the following changes to the
Differentiated "Differentiated Services field
Field Codepoints (DSCP) Registry, (DSCP)" registry, made available at [Registry].

IANA is requested to reference RFC2474 has referenced RFC 2474 and Section 4 of RFC3260 RFC 3260 for the
overall format of the DSCP this registry.

IANA is requested to reference RFC2474 has referenced RFC 2474 and Section 4 of RFC3260 RFC 3260 for Pool 1.

This update document does not modify the IANA registry text for Pool 2.
This pool continues to preserve the note shown in Figure 2.

The previous registry text: text for Pool 3:

3 xxxx01 Experimental or Local Use May local use may be utilized for future
Standards Action allocations as necessary.

is replaced with the following registry text:

3 xxxx01 Standards Action.

To manage codepoints in Pool 3, IANA is requested to create has created and will maintain a "Pool
the "DSCP Pool 3 Codepoints" subregistry. Pool 3 of the registry
is to be has
been created initially empty, with a format identical to that used
for "Pool "DSCP Pool 1 Codepoints".

IANA is requested to reference RFC2474, has referenced RFC 2474, Section 4 of RFC3260, RFC 3260, and the current
document for Pool 3.

The Registration Procedure registration procedure for use of Pool 3 is Standards Action, as
defined as Section 4.9 of [RFC8126]. IANA is expected to normally
make assignments from Pool 1, until this Pool is exhausted, but it
MAY make assignments from Pool 3 where when the format of the codepoint has
properties that are needed for a specific PHB. The required
characteristics for choosing a requested DSCP value MUST be explained
in the IANA considerations Considerations section of the document that requests any
assignment from Pool 3.

6. Acknowledgments

G. Fairhurst received funding from the European Union's Horizon 2020
research and innovation program 2014-2018 under grant agreement No.
644334 (NEAT).

7. References

7.1.

6.1. Normative References

[Registry]
IANA, "Differentiated Services Field Codepoints (DSCP)",
<https://www.iana.org/assignments/dscp-registry/>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/
RFC2119, 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/
rfc2119>.
<https://www.rfc-editor.org/info/rfc2119>.

[RFC2474] Nichols, K., Blake, S., Baker, F. F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998, <http://www.rfc-
editor.org/info/rfc2474>.
<https://www.rfc-editor.org/info/rfc2474>.

[RFC3260] Grossman, D., "New Terminology and Clarifications for
Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002,
<http://www.rfc-editor.org/info/rfc3260>.
<https://www.rfc-editor.org/info/rfc3260>.

[RFC8126] Cotton, M., Leiba, B. B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www
.rfc-editor.org/info/rfc8126>.

[Registry]
IANA, "Differentiated Services Field Codepoints (DSCP),
https://www.iana.org/assignments/dscp-registry/dscp-
registry.xhtml", .

7.2.
<https://www.rfc-editor.org/info/rfc8126>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2. Informative References

[I-D.ietf-tsvwg-le-phb]

[LE-PHB] Bless, R., "A Lower Effort Per-Hop Behavior (LE PHB)",
Internet-Draft draft-ietf-tsvwg-le-phb-02, June 2017.
Work in Progress, draft-ietf-tsvwg-le-phb-05, July 2018.

[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<http://www.rfc-editor.org/info/rfc2475>.

Appendix A. Revision Notes

Note to RFC-Editor: please remove this entire section prior to
publication.

Individual submission as draft -00.

o This is the initial version of the document.

o Advice in this rev.
<https://www.rfc-editor.org/info/rfc2475>.

Acknowledgments

Godred Fairhurst received funding from Michelle Cotton on the IANA procedure.

o Thanks to Brian Carpenter for helpful inputs to this ID.

Individual submission as draft -01.

o Thanks to Roland Bless for review comments.

Individual submission as draft -02 (author requests adoption as a
TSVWG WG draft).

o Thanks to David Black for review comments in preparing rev -02.

Working Group submission as draft -00

o Adopted by the TSVWG working group.

Working Group submission as draft -01

o Fixed exploded acronyms.

Working Group submission as draft -02

o Corrections after WGLC.

Working Group submission as draft -03

o Corrections after TSVWG Shepherd Review.

Working Group submission as draft -04

o Added RFC 3260 as a necessary downref, with IANA asked to
reference this.

Working Group submission as draft -05

o Corrections following AD review.

o Expansion of explanation about why the proposed change will help
in assignment of a suitable DSCP for the LE PHB.

Working Group submission as draft -06

o GenART feedback to changed assignment method to assignment
policy,.

o Correction to the IANA reference documents.

Working Group submission as draft -07

o Revised after IESG feedback - Assignment Policy changed final para
text; Figure 2 reference changed; bleaching defined; definition of
standards action aligned with actual IANA policy.

Working Group submission as draft -08

o Revised after AD feedback - definition of standards action. European Union's Horizon
2020 research and innovation program 2014-2018 under grant agreement
No. 644334 (NEAT).

Author's Address

Godred Fairhurst
University of Aberdeen
Department of Engineering
Fraser Noble Building
Aberdeen,
Aberdeen AB24 3UE
Scotland
United Kingdom

Email: gorry@erg.abdn.ac.uk
URI: http://www.erg.abdn.ac.uk/