RTG Working Group G. Mirsky Internet-Draft ZTE Corp. Intended status: Standards Track J. Tantsura Expires: May 1, 2021 Apstra G. Mishra Verizon Inc. October 28, 2020 Bidirectional Forwarding Detection (BFD) on Multi-chassis Link Aggregation Group (MC-LAG) Interfaces draft-mtm-rtgwg-bfd-mc-lag-00 Abstract This document describes the use of Bidirectional Forwarding Detection for Multi-chassis Link Aggregation Group to provide faster than Link Aggregation Control Protocol convergence. This specification enhances RFC 7130 "Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) Interfaces". 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 May 1, 2021. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. 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 Mirsky, et al. Expires May 1, 2021 [Page 1] Internet-Draft BFD for MC-LAG October 2020 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 2 1.1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . 2 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 3. BFD on MC-LAG with IP-only Data Plane . . . . . . . . . . . . 3 4. BFD on MC-LAG with IP/MPLS Data Plane . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . 5 8.2. Informative . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction The [RFC7130] defines the use of Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) interfaces. A multi-chassis LAG (MC-LAG) is a type of LAG [IEEE.802.1AX.2008] with member links terminated on separate chassis. [IEEE.802.1AX.2008] does not specify MC-LAG but doesn't preclude it either. Link Aggregation Control Protocol (LACP), also defined in [IEEE.802.1AX.2008], can work with MC-LAG but, as in the LAG case, the fastest link failure detection interval is only in a range of single-digit seconds. This document defines how the mechanism defined to work on LAG interfaces [RFC7130] can be adapted to the MC-LAG case to enable sub-second detection of member link failure. 1.1. Conventions used in this document 1.1.1. Acronyms ACH: Associated Channel Header BFD: Bidirectional Forwarding Detection BoS: Bottom of the Stack G-ACh: Generic Associated Channel Mirsky, et al. Expires May 1, 2021 [Page 2] Internet-Draft BFD for MC-LAG October 2020 GAL: Generic Associated Label LAG: Link Aggregation Group LACP: Link Aggregation Control Protocol MC-LAG: Multi-chassis Link Aggregation Group MPLS: Multi-Protocol Label Switching 1.1.2. Requirements Language 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. 2. Problem Statement [RFC7130] does not specify the selection of the destination IP address for the BFD control packet. The only requirement related to the selection is in Section 2.1, stating that the use of the address family across all member links of the given LAG MUST be consistent across all the links. Thus it is implied that the same unicast IP address will be used on all member links of the LAG as the use of different destination addresses would defeat the purpose of [RFC7130] transforming the case into a set of single-hop BFD sessions [RFC5881]. But a single unicast IP address may not work in the MC- LAG case as the member links are terminated on the separate chassis. This document proposes how to overcome this problem if using IP or Multi-Protocol Label Switching (MPLS) data plane encapsulation. 3. BFD on MC-LAG with IP-only Data Plane As described in [RFC7130], a micro-BFD session on the LAG interfaces may use IPv4 or IPv6 address family. In some cases, two sessions, one with IPv4 and one with IPv6 addresses, may run concurrently. This document doesn't change any of these but specifies the selection of the destination IP address in the MC-LAG use case: o if IPv4 address family is used for the micro-BFD session, then an address from the link-local multicast address 224.0.0.0/24 range SHOULD be used as the destination IP address. The subnet broadcast address MAY be used as the destination IP address as well; Mirsky, et al. Expires May 1, 2021 [Page 3] Internet-Draft BFD for MC-LAG October 2020 o if the address family used is IPv6, then the IPv6 All Routers address with the link scope, as defined in [RFC4291], FF02::2/128 MUST be used as the destination IP address. 4. BFD on MC-LAG with IP/MPLS Data Plane There are more optional encapsulation formats for the case of micro- BFD on MC-LAG over IP/MPLS data plane: o [RFC5586] defined the special-purpose Generic Associated channel Label (GAL) that MAY be used in MPLS encapsulation of the micro- BFD control packet over the MPSL data plane. Depending on the channel type specified in the Associated Channel Header (ACH) that immediately follows after the GAL, micro-BFD MAY use IP/UDP, as displayed in Figure 1 or BFD format, i.e., BFD control packet without IP and UDP headers. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | GAL | TC |1| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 1|0 0 0 0| Reserved | IPv4 channel (0x0021) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination IP address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source IP address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | UDP header | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ BFD Control Packet ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: BFD on MC-LAG member link on IPv4/MPLS data plane If the IP/UDP format of BFD over MC-LAG interfaces is used, then the destination IP address MUST be set to the loopback address 127.0.0.1/32 for IPv4 [RFC1812], or the loopback address ::1/128 for IPv6 [RFC4291]. Mirsky, et al. Expires May 1, 2021 [Page 4] Internet-Draft BFD for MC-LAG October 2020 5. IANA Considerations This document makes no requests for IANA allocations. This section may be deleted by RFC Editor. 6. Security Considerations This document does not introduce new security concerns but inherits all security considerations discussed in [RFC5881] and [RFC7130]. 7. Acknowledgements TBD 8. References 8.1. Normative References [IEEE.802.1AX.2008] "IEEE Standard for Local and metropolitan area networks - Link Aggregation", IEEE 802.1-AX, November 2008. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., "MPLS Generic Associated Channel", RFC 5586, DOI 10.17487/RFC5586, June 2009, . [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, DOI 10.17487/RFC5881, June 2010, . [RFC7130] Bhatia, M., Ed., Chen, M., Ed., Boutros, S., Ed., Binderberger, M., Ed., and J. Haas, Ed., "Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) Interfaces", RFC 7130, DOI 10.17487/RFC7130, February 2014, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Mirsky, et al. Expires May 1, 2021 [Page 5] Internet-Draft BFD for MC-LAG October 2020 8.2. Informative [RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers", RFC 1812, DOI 10.17487/RFC1812, June 1995, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . Authors' Addresses Greg Mirsky ZTE Corp. Email: gregimirsky@gmail.com Jeff Tantsura Apstra Email: jefftant.ietf@gmail.com Gyan Mishra Verizon Inc. Email: gyan.s.mishra@verizon.com Mirsky, et al. Expires May 1, 2021 [Page 6]