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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (June 11, 2018) is 2145 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: '0x00000000-0x0000FFFF' is mentioned on line 165, but not defined -- Possible downref: Non-RFC (?) normative reference: ref. 'IANA-WKS' Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Borkenhagen 3 Internet-Draft AT&T 4 Intended status: Standards Track R. Bush 5 Expires: December 13, 2018 Internet Initiative Japan 6 R. Bonica 7 Juniper Networks 8 S. Bayraktar 9 Cisco Systems 10 June 11, 2018 12 Well-Known Community Policy Behavior 13 draft-ymbk-grow-wkc-behavior-02 15 Abstract 17 Well-Known BGP Communities are manipulated inconsistently by current 18 implementations. This results in difficulties for operators. It is 19 recommended that removal policies be applied consistently to Well- 20 Known Communities. 22 Requirements Language 24 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 25 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to 26 be interpreted as described in RFC 2119 [RFC2119] only when they 27 appear in all upper case. They may also appear in lower or mixed 28 case as English words, without normative meaning. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on December 13, 2018. 47 Copyright Notice 49 Copyright (c) 2018 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 65 2. Manipulation of Communities by Policy . . . . . . . . . . . . 3 66 3. Community Manipulation Policy Differences . . . . . . . . . . 3 67 4. Documentation of Vendor Implementations . . . . . . . . . . . 3 68 4.1. Note on an Inconsistency . . . . . . . . . . . . . . . . 4 69 5. Note for Those Writing RFCs for New Community-Like 70 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 4 71 6. Action Items . . . . . . . . . . . . . . . . . . . . . . . . 4 72 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 73 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 74 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 75 10. Normative References . . . . . . . . . . . . . . . . . . . . 5 76 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 78 1. Introduction 80 The BGP Communities Attribute was specified in [RFC1997] which 81 introduced the concept of Well-Known Communities. In hindsight, it 82 did not prescribe as fully as it should have how Well-Known 83 Communities may be manipulated by policies applied by operators. 84 Currently, implementations differ in this regard, and these 85 differences can result in inconsistent behaviors that operators find 86 difficult to identify and resolve. 88 This document describes the current behavioral differences in order 89 to assist operators in generating consistent community-manipulation 90 policies in a multi-vendor environment, and to prevent the 91 introduction of additional divergence in implementations. 93 2. Manipulation of Communities by Policy 95 [RFC1997] says: 97 "A BGP speaker receiving a route with the COMMUNITIES path attribute 98 may modify this attribute according to the local policy." 100 One common operational need is to add or remove one or more 101 communities to the current set. Another common need is to replace 102 all received communities with a new set as defined by policy. All 103 BGP policy implementations we know of provide syntax to "set" a 104 community that operators use to mean "remove any/all communities 105 present on the update received from the neighbor, and apply this set 106 of communities instead." 108 3. Community Manipulation Policy Differences 110 Vendor implementations differ in the treatment of certain Well-Known 111 communities when modified using the syntax to "set" the community. 112 Some replace all communities including the Well-Known ones with the 113 new set, while others replace all non-Well-Known Communities but do 114 not modify any Well-Known Communities that are present. 116 These differences result in what would appear to be identical policy 117 configurations having very different results on different platforms. 119 4. Documentation of Vendor Implementations 121 In Juniper Networks' JunOS, "community set" removes all received 122 communities, Well-Known or otherwise. 124 In Cisco Systems' IOS-XR, "set community" removes all received 125 communities except for the following: 127 +-------------+-----------------------------------+ 128 | Numeric | Common Name | 129 +-------------+-----------------------------------+ 130 | 0:0 | internet | 131 | 65535:0 | graceful-shutdown | 132 | 65535:1 | accept-own rfc7611 | 133 | 65535:65281 | NO_EXPORT | 134 | 65535:65282 | NO_ADVERTISE | 135 | 65535:65283 | NO_EXPORT_SUBCONFED (or local-AS) | 136 +-------------+-----------------------------------+ 138 Communities not removed by Cisco IOS/XR 140 Table 1 142 IOS-XR does allow Well-Known communities to be removed one at a time 143 by explicit policy; for example, "delete community accept-own". 144 Operators are advised to consult IOS-XR documentation and/or Cisco 145 Systems support for full details. 147 On Brocade NetIron: "set community X" removes all communities and 148 sets X. 150 In Huawei's VRP product, "community set" removes all received 151 communities, well-Known or otherwise. 153 In OpenBSD's OpenBGPD, "community set" removes no communities, well- 154 Known or otherwise. 156 4.1. Note on an Inconsistency 158 The IANA publishes a list of Well-Known Communities [IANA-WKS]. 160 IOS-XR's set of well-known communities that "set community" will not 161 overwrite diverges from IANA's list. Quite a few well-known 162 communities from IANA's list do not receive special treatment in IOS- 163 XR, and at least one specific community on IOS-XR's special treatment 164 list (internet == 0:0) is not really on IANA's list -- it's taken 165 from the "Reserved" range [0x00000000-0x0000FFFF]. 167 This merely notes an inconsistency. It is not a plea to 'protect' 168 the entire IANA list from "set community." 170 5. Note for Those Writing RFCs for New Community-Like Attributes 172 Care should be taken when establishing new [RFC1997]-like attributes 173 (large communities, wide communities, etc) to avoid repeating this 174 mistake. 176 6. Action Items 178 Unfortunately, it would be operationally disruptive for vendors to 179 change their current implementations. 181 Vendors SHOULD share the behavior of their implementations for 182 inclusion in this document, especially if their behavior differs from 183 the examples described. 185 For new well-known communities specified (after this draft), vendors 186 MUST treat "community set" command to mean "remove all other 187 communities, Well-Known or otherwise." 189 7. Security Considerations 191 Surprising defaults and/or undocumented behaviors are not good for 192 security. This document attepts to remedy that. 194 8. IANA Considerations 196 This document has no IANA Considerations other than to be aware that 197 any future Well-Known Communities will be subject to the policy 198 treatment described here. 200 9. Acknowledgements 202 The authors thank Martijn Schmidt for his contribution, Qin Wu for 203 the Huawei data point. 205 10. Normative References 207 [IANA-WKS] 208 "IANA Well-Known Comunities", 209 . 212 [RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities 213 Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996, 214 . 216 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 217 Requirement Levels", BCP 14, RFC 2119, 218 DOI 10.17487/RFC2119, March 1997, 219 . 221 Authors' Addresses 223 Jay Borkenhagen 224 AT&T 225 200 Laurel Avenue South 226 Middletown, NJ 07748 227 United States of America 229 Email: jayb@att.com 230 Randy Bush 231 Internet Initiative Japan 232 5147 Crystal Springs 233 Bainbridge Island, WA 98110 234 United States of America 236 Email: randy@psg.com 238 Ron Bonica 239 Juniper Networks 240 2251 Corporate Park Drive 241 Herndon, VA 20171 242 US 244 Email: rbonica@juniper.net 246 Serpil Bayraktar 247 Cisco Systems 248 170 W. Tasman Drive 249 San Jose, CA 95134 250 United States of America 252 Email: serpil@cisco.com