MPLS WG K. Kompella Internet-Draft R. Bonica Updates: 7506, 8029 (if approved) Juniper Networks Intended status: Standards Track 9 December 2021 Expires: 12 June 2022 Deprecating the Use of Router Alert in LSP Ping draft-kompella-mpls-lspping-norao-00 Abstract LSP ping messages (RFC 8029) are encapsulated in IP headers that include a Router Alert Option (RAO). The rationale for including an RAO is questionable. Furthermore, RFC6398 identifies security vulnerabilities associated with the RAO. Therefore, this document removes the RAO from LSP ping message encapsulations. It updates RFCs 7506 and 8029. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 12 June 2022. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. Kompella & Bonica Expires 12 June 2022 [Page 1] Internet-Draft RAO-less LSP Ping December 2021 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Router Alert for LSP Ping (RFC 8029) . . . . . . . . . . . . 3 2.1. Echo Request . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Echo Reply . . . . . . . . . . . . . . . . . . . . . . . 4 3. Update to RFC 7506 . . . . . . . . . . . . . . . . . . . . . 4 4. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction LSP ping [RFC8029] detects data-plane failures in MPLS Label Switched Paths (LSPs). It can operate in "ping mode" or "traceroute mode". When operating in ping mode, it verifies end-to-end LSP continuity. When operating in traceroute mode, it can localize failures to a particular node along an LSP. LSP ping defines a probe message, called the "MPLS echo request". It also defines a response message, called the "MPLS echo reply". Both messages are encapsulated in UDP and IP. The echo request message is further encapsulated in an MPLS label stack. When operating in ping mode, LSP ping sends a single echo request message, with the MPLS TTL set to a high value (e.g., 255). This message is intended to reach the egress Label Switching Router (LSR). When operating in traceroute mode, MPLS ping sends multiple echo request messages. It manipulates the MPLS TTL so that the first message expires on the first LSR along the path and subsequent messages expire on subsequent LSRs. Kompella & Bonica Expires 12 June 2022 [Page 2] Internet-Draft RAO-less LSP Ping December 2021 The IP header that encapsulates an echo request message must include a Router Alert Option (RAO), while the IP header that encapsulates an echo reply message may include an RAO. In both cases, the rationale for including an RAO is questionable. Furthermore, [RFC6398] identifies security vulnerabilities associated with the RAO and recommends against its use outside of controlled environments. Therefore, this document removes the RAO from both LSP ping message encapsulations. It updates RFCs 7506 [RFC7506] and 8029. 1.1. Terminology 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 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. LSP: Label Switched Path LSR: Label Switching Router RAO: Router Alert Option 2. Router Alert for LSP Ping (RFC 8029) 2.1. Echo Request While the MPLS echo request message must traverse every node in the LSP under test, it must not traverse any other node. Specifically, the message must not be forwarded beyond the egress Label Switching Router (LSR). To achieve this, RFC 8029 proposes the following: 1. When the echo request message is encapsulated in IPv4, the IPv4 destination address must be chosen from the subnet 127/8. When the echo request message is encapsulated in IPv6, the IPv6 destination address must be chosen from the subnet 0:0:0:0:0:FFFF:7F00:0/104. 2. When the echo request message is encapsulated in IPv4, the IPv4 TTL must be equal to 1. When the echo request message is encapsulated in IPv6, the IPv6 Hop Limit must be equal to 1. Kompella & Bonica Expires 12 June 2022 [Page 3] Internet-Draft RAO-less LSP Ping December 2021 3. When the echo request message is encapsulated in IPv4, the IPv4 header must include an RAO. When the echo request message is encapsulated in IPv6, the IPv6 header chain must include a Hop- by-hop extension header and the Hop-by-hop extension header must include an RAO. Currently, ALL of these are required. However, any one is sufficient to prevent forwarding the packet beyond the egress LSR. Therefore, this document RECOMMENDS removing Requirement 3 from RFC 8029. The authors are not aware of any implementation that relies on the RAO to prevent packets from being forwarded beyond the egress LSR. 2.2. Echo Reply An LSP ping replies to the MPLS echo message with an MPLS echo reply message. It has four reply modes: 1. Do not reply 2. Reply via an IPv4/IPv6 UDP packet 3. Reply via an IPv4/IPv6 UDP packet with Router Alert 4. Reply via application-level control channel The rationale for mode 3 is questionable, if not wholly misguided. According to RFC 8029, "If the normal IP return path is deemed unreliable, one may use 3 (Reply via an IPv4/IPv6 UDP packet with Router Alert)." However, it is not clear that the use of the RAO increases the reliability of the return path. In fact, one can argue it decreases the reliability in many instances, due to the additional burden of processing the RAO. This document RECOMMENDS removing mode 3 from RFC 8029. The authors are not aware of any implementations of mode 3. 3. Update to RFC 7506 RFC 7506 defines the IPv6 Router Alert Option for MPLS Operations, Administration, and Management. This document RECOMMENDS that RFC 7506 be reclassified as Historic. Kompella & Bonica Expires 12 June 2022 [Page 4] Internet-Draft RAO-less LSP Ping December 2021 4. Backwards Compatibility LSP Ping implementations SHOULD ignore RAO options when they arrive on incoming echo request and echo reply messages. 5. IANA Considerations If this document is approved, mark the IPv6 RAO value of MPLS OAM (69) in [IANA-IPV6-RAO] as "Deprecated". Also, mark Reply Mode 3 ("Reply via an IPv4/IPv6 UDP packet with Router Alert") in [IANA-LSP-PING] as "Deprecated". 6. Security Considerations The recommendations this document makes do not compromise security. 7. Normative References [IANA-IPV6-RAO] IANA, "IPv6 Router Alert Option Values", n.d., . [IANA-LSP-PING] IANA, "Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters", n.d., . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC6398] Le Faucheur, F., Ed., "IP Router Alert Considerations and Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October 2011, . [RFC7506] Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert Option for MPLS Operations, Administration, and Maintenance (OAM)", RFC 7506, DOI 10.17487/RFC7506, April 2015, . Kompella & Bonica Expires 12 June 2022 [Page 5] Internet-Draft RAO-less LSP Ping December 2021 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., Aldrin, S., and M. Chen, "Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures", RFC 8029, DOI 10.17487/RFC8029, March 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Authors' Addresses Kireeti Kompella Juniper Networks 1133 Innovation Way Sunnyvale, CA 94089 United States Email: kireeti.ietf@gmail.com Ronald Bonica Juniper Networks 1133 Innovation Way Sunnyvale, CA 94089 United States Email: rbonica@juniper.net Kompella & Bonica Expires 12 June 2022 [Page 6]