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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (9 December 2021) is 156 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) -- Possible downref: Non-RFC (?) normative reference: ref. 'IANA-IPV6-RAO' -- Possible downref: Non-RFC (?) normative reference: ref. 'IANA-LSP-PING' Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS WG K. Kompella 3 Internet-Draft R. Bonica 4 Updates: 7506, 8029 (if approved) Juniper Networks 5 Intended status: Standards Track 9 December 2021 6 Expires: 12 June 2022 8 Deprecating the Use of Router Alert in LSP Ping 9 draft-kompella-mpls-lspping-norao-00 11 Abstract 13 LSP ping messages (RFC 8029) are encapsulated in IP headers that 14 include a Router Alert Option (RAO). The rationale for including an 15 RAO is questionable. Furthermore, RFC6398 identifies security 16 vulnerabilities associated with the RAO. 18 Therefore, this document removes the RAO from LSP ping message 19 encapsulations. It updates RFCs 7506 and 8029. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on 12 June 2022. 38 Copyright Notice 40 Copyright (c) 2021 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 45 license-info) in effect on the date of publication of this document. 46 Please review these documents carefully, as they describe your rights 47 and restrictions with respect to this document. Code Components 48 extracted from this document must include Revised BSD License text as 49 described in Section 4.e of the Trust Legal Provisions and are 50 provided without warranty as described in the Revised BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 56 2. Router Alert for LSP Ping (RFC 8029) . . . . . . . . . . . . 3 57 2.1. Echo Request . . . . . . . . . . . . . . . . . . . . . . 3 58 2.2. Echo Reply . . . . . . . . . . . . . . . . . . . . . . . 4 59 3. Update to RFC 7506 . . . . . . . . . . . . . . . . . . . . . 4 60 4. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 5 61 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 62 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 63 7. Normative References . . . . . . . . . . . . . . . . . . . . 5 64 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 66 1. Introduction 68 LSP ping [RFC8029] detects data-plane failures in MPLS Label Switched 69 Paths (LSPs). It can operate in "ping mode" or "traceroute mode". 70 When operating in ping mode, it verifies end-to-end LSP continuity. 71 When operating in traceroute mode, it can localize failures to a 72 particular node along an LSP. 74 LSP ping defines a probe message, called the "MPLS echo request". It 75 also defines a response message, called the "MPLS echo reply". Both 76 messages are encapsulated in UDP and IP. The echo request message is 77 further encapsulated in an MPLS label stack. 79 When operating in ping mode, LSP ping sends a single echo request 80 message, with the MPLS TTL set to a high value (e.g., 255). This 81 message is intended to reach the egress Label Switching Router (LSR). 82 When operating in traceroute mode, MPLS ping sends multiple echo 83 request messages. It manipulates the MPLS TTL so that the first 84 message expires on the first LSR along the path and subsequent 85 messages expire on subsequent LSRs. 87 The IP header that encapsulates an echo request message must include 88 a Router Alert Option (RAO), while the IP header that encapsulates an 89 echo reply message may include an RAO. In both cases, the rationale 90 for including an RAO is questionable. Furthermore, [RFC6398] 91 identifies security vulnerabilities associated with the RAO and 92 recommends against its use outside of controlled environments. 94 Therefore, this document removes the RAO from both LSP ping message 95 encapsulations. It updates RFCs 7506 [RFC7506] and 8029. 97 1.1. Terminology 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 101 "OPTIONAL" in this document are to be interpreted as described in 102 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 103 capitals, as shown here. 105 LSP: Label Switched Path 107 LSR: Label Switching Router 109 RAO: Router Alert Option 111 2. Router Alert for LSP Ping (RFC 8029) 113 2.1. Echo Request 115 While the MPLS echo request message must traverse every node in the 116 LSP under test, it must not traverse any other node. Specifically, 117 the message must not be forwarded beyond the egress Label Switching 118 Router (LSR). 120 To achieve this, RFC 8029 proposes the following: 122 1. When the echo request message is encapsulated in IPv4, the IPv4 123 destination address must be chosen from the subnet 127/8. When 124 the echo request message is encapsulated in IPv6, the IPv6 125 destination address must be chosen from the subnet 126 0:0:0:0:0:FFFF:7F00:0/104. 128 2. When the echo request message is encapsulated in IPv4, the IPv4 129 TTL must be equal to 1. When the echo request message is 130 encapsulated in IPv6, the IPv6 Hop Limit must be equal to 1. 132 3. When the echo request message is encapsulated in IPv4, the IPv4 133 header must include an RAO. When the echo request message is 134 encapsulated in IPv6, the IPv6 header chain must include a Hop- 135 by-hop extension header and the Hop-by-hop extension header must 136 include an RAO. 138 Currently, ALL of these are required. However, any one is sufficient 139 to prevent forwarding the packet beyond the egress LSR. 141 Therefore, this document RECOMMENDS removing Requirement 3 from RFC 142 8029. 144 The authors are not aware of any implementation that relies on the 145 RAO to prevent packets from being forwarded beyond the egress LSR. 147 2.2. Echo Reply 149 An LSP ping replies to the MPLS echo message with an MPLS echo reply 150 message. It has four reply modes: 152 1. Do not reply 154 2. Reply via an IPv4/IPv6 UDP packet 156 3. Reply via an IPv4/IPv6 UDP packet with Router Alert 158 4. Reply via application-level control channel 160 The rationale for mode 3 is questionable, if not wholly misguided. 161 According to RFC 8029, "If the normal IP return path is deemed 162 unreliable, one may use 3 (Reply via an IPv4/IPv6 UDP packet with 163 Router Alert)." 165 However, it is not clear that the use of the RAO increases the 166 reliability of the return path. In fact, one can argue it decreases 167 the reliability in many instances, due to the additional burden of 168 processing the RAO. This document RECOMMENDS removing mode 3 from 169 RFC 8029. 171 The authors are not aware of any implementations of mode 3. 173 3. Update to RFC 7506 175 RFC 7506 defines the IPv6 Router Alert Option for MPLS Operations, 176 Administration, and Management. This document RECOMMENDS that RFC 177 7506 be reclassified as Historic. 179 4. Backwards Compatibility 181 LSP Ping implementations SHOULD ignore RAO options when they arrive 182 on incoming echo request and echo reply messages. 184 5. IANA Considerations 186 If this document is approved, mark the IPv6 RAO value of MPLS OAM 187 (69) in [IANA-IPV6-RAO] as "Deprecated". 189 Also, mark Reply Mode 3 ("Reply via an IPv4/IPv6 UDP packet with 190 Router Alert") in [IANA-LSP-PING] as "Deprecated". 192 6. Security Considerations 194 The recommendations this document makes do not compromise security. 196 7. Normative References 198 [IANA-IPV6-RAO] 199 IANA, "IPv6 Router Alert Option Values", n.d., 200 . 203 [IANA-LSP-PING] 204 IANA, "Multiprotocol Label Switching (MPLS) Label Switched 205 Paths (LSPs) Ping Parameters", n.d., 206 . 209 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 210 Requirement Levels", BCP 14, RFC 2119, 211 DOI 10.17487/RFC2119, March 1997, 212 . 214 [RFC6398] Le Faucheur, F., Ed., "IP Router Alert Considerations and 215 Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October 216 2011, . 218 [RFC7506] Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert 219 Option for MPLS Operations, Administration, and 220 Maintenance (OAM)", RFC 7506, DOI 10.17487/RFC7506, April 221 2015, . 223 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 224 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 225 Switched (MPLS) Data-Plane Failures", RFC 8029, 226 DOI 10.17487/RFC8029, March 2017, 227 . 229 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 230 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 231 May 2017, . 233 Authors' Addresses 235 Kireeti Kompella 236 Juniper Networks 237 1133 Innovation Way 238 Sunnyvale, CA 94089 239 United States 241 Email: kireeti.ietf@gmail.com 243 Ronald Bonica 244 Juniper Networks 245 1133 Innovation Way 246 Sunnyvale, CA 94089 247 United States 249 Email: rbonica@juniper.net