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Fairhurst 3 Internet-Draft University of Aberdeen 4 Updates: 2474 (if approved) May 07, 2018 5 Intended status: Standards Track 6 Expires: November 06, 2018 8 IANA Assignment of DSCP Pool 3 (xxxx01) Values to require Publication of 9 a Standards Track or Best Current Practice RFC 10 draft-ietf-tsvwg-iana-dscp-registry-03 12 Abstract 14 The Differentiated Services (Diffserv) architecture specifies use of 15 a field in the IPv4 and IPv6 packet headers to carry Diffserv 16 Codepoint (DSCP) values. The Internet Assigned Numbers Authority 17 (IANA) maintains a registry of assigned DSCP values. 19 This update to RFC2474 changes the IANA assignment method for Pool 3 20 of the registry (i.e., DSCP values of the form xxxx01) to Standards 21 Action, i.e., values are assigned through a Standards Track or Best 22 Current Practice RFC. The update also removes permission for 23 experimental and Local Use of the Codepoints that form Pool 3 of the 24 DSCP registry; Pool 2 Codepoints (i.e., DSCP values of the form 25 xxxx11) remain available for these purposes. 27 Status of this Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on November 06, 2018. 44 Copyright Notice 46 Copyright (c) 2018 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents (http://trustee.ietf.org/ 51 license-info) in effect on the date of publication of this document. 52 Please review these documents carefully, as they describe your rights 53 and restrictions with respect to this document. Code Components 54 extracted from this document must include Simplified BSD License text 55 as described in Section 4.e of the Trust Legal Provisions and are 56 provided without warranty as described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 61 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 3. The update to RFC2474 . . . . . . . . . . . . . . . . . . . . 4 63 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 64 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 65 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 66 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 7.1. Normative References . . . . . . . . . . . . . . . . . . . 5 68 7.2. Informative References . . . . . . . . . . . . . . . . . . 6 69 Appendix A. Revision Notes . . . . . . . . . . . . . . . . . . . . 6 70 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 72 1. Introduction 74 The Differentiated Services (Diffserv) [RFC2475] architecture 75 (updated by [RFC3260]) provides scalable service differentiation in 76 the Internet. Diffserv uses the six most significant bits of the 77 former IPv4 Type of Service (TOS) octet or the former IPV6 Traffic 78 Class octet to convey the field, which is used to carry the Diffserv 79 Codepoint (DSCP). This DSCP value is used to select a Diffserv Per 80 hop Behaviour, PHB. 82 The six bit field is capable of conveying 64 distinct codepoints, and 83 this codepoint space has been divided into three pools for the 84 purpose of codepoint assignment and management (as shown in figure 85 1). Pool 1 comprises 32 codepoints [RFC2474]. These are assigned by 86 Standards Action, as defined in [RFC8126]. Pool 2 comprises a pool 87 of 16 codepoints reserved for experimental or Local Use (EXP/LU) as 88 defined in [RFC2474], and Pool 3 comprises 16 codepoints, which were 89 specified as "initially available for experimental or local use, but 90 which should be preferentially utilized for standardized assignments 91 if Pool 1 is ever exhausted" [RFC2474]. 93 +------+-----------------+ 94 | Pool | Codepoint Space | 95 +------+-----------------+ 96 | 1 | xxxxx0 | 97 +------+-----------------+ 98 | 2 | xxxx11 | 99 +------+-----------------+ 100 | 3 | xxxx01 | 101 +------+-----------------+ 103 Figure 1: Format of the field for codepoints allocated in the 104 three IANA pools (where 'x' refers to either '0' or '1'). 106 At the time of writing this document, 22 of the 32 Pool 1 codepoints 107 have currently been assigned. 109 Although Pool 1 has not yet been completely exhausted, this document 110 changes the IANA registration policy of Pool 3 to assignment by 111 Standards Action, i.e., values are assigned by Standards Track or 112 Best Current Practice RFCs. The rationale for this update is a need 113 to assign codepoints for particular PHBs that are unable to use any 114 of the unassigned values in Pool 1. 116 An example is the need to assign a suitable recommended default 117 codepoint for the Lower Effort (LE) per-hop behavior (PHB) [I-D.ietf- 118 tsvwg-le-phb]. The LE PHB is designed to protect best-effort (BE) 119 traffic (packets forwarded with the default PHB) from LE traffic in 120 congestion situations, i.e., when resources become scarce, best- 121 effort traffic has precedence over LE traffic and may preempt it. 122 The continued presence of bleaching of the IP precedence field, 123 setting the first three bits of the former TOS byte to zero (i.e., 124 zeroing the top three bits of the DSCP) in deployed networks 125 motivates the desire for the LE PHB to use a DSCP with a zero value 126 for the first three bits [I-D.ietf-tsvwg-le-phb]. At the same time, 127 it is also important to reduce the likelihood of priority inversion 128 caused by unintentional re-mapping of other (higher assurance) 129 traffic to the DSCP used for this PHB. The absence of unassigned 130 codepoints in Pool 1 that exhibit these important properties 131 motivates assigning a Pool 3 codepoint as the default that is 132 recommended for use with this PHB. 134 To allow the IETF to utilise Pool 3 codepoints, this document 135 requests IANA to to manage Pool 3 assignments for DSCP values in Pool 136 3 via the Standards Action policy [RFC8126]. This assignment method 137 requires publication of a Standards Track or Best Current Practice 138 RFC. 140 2. Terminology 142 This document assumes familiarity with the terminology used in 143 [RFC2475] updated by [RFC3260]. 145 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 146 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 147 "OPTIONAL" in this document are to be interpreted as described in 148 [RFC2119]. 150 3. The update to RFC2474 152 This document updates section 6 of [RFC2474], in the following ways. 154 It updates the following text concerning the assignment method: 156 OLD: which are initially available for experimental or local use, but 157 which should be preferentially utilized for standardized 158 assignments if Pool 1 is ever exhausted. 160 NEW: which are utilized for standardized assignments (replacing the 161 previous availability for experimental or local use). 163 It removes the footnote in RFC2474 relating to Pool 3: 165 DELETE: "(*) may be utilized for future Standards Action allocations 166 as necessary" 168 The new registry contents are shown in Figure 2. 170 Pool Codepoint space Assignment Policy 171 ---- --------------- ------------------ 173 1 xxxxx0 Standards Action 174 2 xxxx11 EXP/LU 175 3 xxxx01 Standards Action 177 Note for Pool 2: "Reserved for experimental or Local Use" 179 Figure 2: Updated Assignment Policy for the DSCP Registry 181 4. Security Considerations 183 Security considerations for the use of DSCP values are described in 184 the RFCs that define their usage. This document does not present new 185 security considerations. 187 5. IANA Considerations 189 This section requests IANA to change the use of Pool 3 in the DSCP 190 registry and to manage this pool using a Standards Action assignment 191 method. 193 This requests IANA to make the following changes to the 194 Differentiated Services field Codepoints (DSCP) Registry, made 195 available at [Registry]. 197 This update does not modify the IANA registry text for Pool 2. This 198 pool continues to preserve the note shown in Figure 2. 200 The previous registry text: 202 3 xxxx01 Experimental or Local Use May be utilized for future 203 Standards Action allocations as necessary. 205 is replaced with the following registry text: 207 3 xxxx01 Standards Action. 209 To manage codepoints in Pool 3, IANA is requested to create and 210 maintain a "Pool 3 Codepoints" entry. Pool 3 of the registry is to 211 be created initially empty, with a format identical to that used for 212 "Pool 1 Codepoints". 214 The Registration Procedure for use of Pool 3 is "Standards Action" 215 [RFC8126]. IANA is expected to normally make assignments from Pool 216 1, until this Pool is exhausted, but MAY make assignments from Pool 3 217 where the format of the codepoint has properties that are needed for 218 a specific PHB. The required characteristics for choosing the DSCP 219 value MUST be explained in the IANA considerations of the document 220 that requests any assignment from Pool 3 222 IANA is requested to reference RFC3260 and this current document. 224 6. Acknowledgments 226 G. Fairhurst received funding from the European Union's Horizon 2020 227 research and innovation program 2014-2018 under grant agreement No. 228 644334 (NEAT). 230 7. References 232 7.1. Normative References 234 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 235 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 236 RFC2119, March 1997, . 239 [RFC2474] Nichols, K., Blake, S., Baker, F. and D. Black, 240 "Definition of the Differentiated Services Field (DS 241 Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 242 10.17487/RFC2474, December 1998, . 245 [RFC3260] Grossman, D., "New Terminology and Clarifications for 246 Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002, 247 . 249 [RFC8126] Cotton, M., Leiba, B. and T. Narten, "Guidelines for 250 Writing an IANA Considerations Section in RFCs", BCP 26, 251 RFC 8126, DOI 10.17487/RFC8126, June 2017, . 254 [Registry] 255 IANA, "Differentiated Services Field Codepoints (DSCP), 256 https://www.iana.org/assignments/dscp-registry/dscp- 257 registry.xhtml", . 259 7.2. Informative References 261 [I-D.ietf-tsvwg-le-phb] 262 Bless, R., "A Lower Effort Per-Hop Behavior (LE PHB)", 263 Internet-Draft draft-ietf-tsvwg-le-phb-02, June 2017. 265 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. 266 and W. Weiss, "An Architecture for Differentiated 267 Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, 268 . 270 Appendix A. Revision Notes 272 Note to RFC-Editor: please remove this entire section prior to 273 publication. 275 Individual submission as draft -00. 277 o This is the initial version of the document. 279 o Advice in this rev. from Michelle Cotton on the IANA procedure. 281 o Thanks to Brian Carpenter for helpful inputs to this ID. 283 Individual submission as draft -01. 285 o Thanks to Roland Bless for review comments. 287 Individual submission as draft -02 (author requests adoption as a 288 TSVWG WG draft). 290 o Thanks to David Black for review comments in preparing rev -02. 292 Working Group submission as draft -00 294 o Adopted by the TSVWG working group. 296 Working Group submission as draft -01 298 o Fixed exploded acronyms. 300 Working Group submission as draft -02 301 o Corrections after WGLC. 303 Working Group submission as draft -03 305 o Corrections after TSVWG Shepherd Review. 307 Author's Address 309 Godred Fairhurst 310 University of Aberdeen 311 Department of Engineering 312 Fraser Noble Building 313 Aberdeen, AB24 3UE 314 Scotland 316 Email: gorry@erg.abdn.ac.uk 317 URI: http://www.erg.abdn.ac.uk/