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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 (March 5, 2019) is 1879 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) No issues found here. Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BESS WG Z. Zhang 3 Internet-Draft Y. Wang 4 Intended status: Standards Track G. Mirsky 5 Expires: September 6, 2019 ZTE Corporation 6 March 5, 2019 8 Bidirectional Forwarding Detection (BFD) for EVPN Ethernet Segment 9 Failover Use Case 10 draft-zwm-bess-es-failover-00.txt 12 Abstract 14 This document introduces a method for fast switchover of Designated 15 Forwarder for Ethernet Segment failover by using Bidirectional 16 Forwarding Detection protocol. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on September 6, 2019. 35 Copyright Notice 37 Copyright (c) 2019 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (https://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Proposal . . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 3 55 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 56 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 57 6. Normative References . . . . . . . . . . . . . . . . . . . . 4 58 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 60 1. Introduction 62 [RFC7432] introduces Ethernet Virtual Private Network (EVPN) 63 technology. Designated Forwarder (DF) election procedures for multi- 64 homing Ethernet Segments has been described in it. When PE (provider 65 edge) receives BUM (Broadcast, Unknown Unicast and Multicast) flows, 66 only DF forwards the BUM flows to CE (customer edge). Non-DFs do not 67 forward the BUM flows in order to avoid duplication. If the link 68 between DF and CE fails, another PE will forward the BUM flows after 69 it is elected as DF. 71 [I-D.ietf-bess-evpn-df-election-framework] defines the DF election 72 framework, including that Backup Designated Forwarder (BDF) can be 73 elected as the next best for the role. But before the BDF is elected 74 as DF, the BUM flows are discarded after the link between DF and CE 75 fails. 77 +-----+ 78 +-----X----+ PE1 | 79 | +--+--+ 80 | 81 +-+--+ 82 | CE | 83 +-+--+ 84 | 85 | +--+--+ 86 +----------+ PE2 | 87 +-----+ 89 For example, CE is multihomed to PE1 and PE2. PE1 is elected as DF. 90 All BUM flows are forwarded by PE1 when the link between PE1 and CE 91 is operational. When the link between PE1 and CE fails, the BUM 92 flows are discarded until PE2 is elected as DF. 94 This document will use terminology defined in [RFC7432] and 95 [I-D.jain-bess-evpn-lsp-ping]. 97 2. Proposal 99 In order to avoid the BUM packet loss on BDF after the link between 100 DF and CE fails, a data-plane detection function is needed for DF 101 fast switchover. [RFC5884] provides mechanisms for using LSP Ping to 102 bootstrap a BFD session. [I-D.jain-bess-evpn-lsp-ping] introduces 103 four new Target FEC Stack sub-TLVs that are included in the LSP-Ping 104 Echo Request packet. This document uses the mechanisms defined in 105 [RFC5884] and the EVPN Ethernet Auto-Discovery (AD) sub-TLV defined 106 in [I-D.jain-bess-evpn-lsp-ping] to provide DF fast switchover by 107 data-plane failure detection. 109 An LSP-Ping Echo Request message which carries EVPN AD Sub-TLV 110 associated with the DF-CE Ethernet Segment Identifier (ESI) is used 111 to bootstrap the BFD session between BDF and DF. After the BFD 112 session is built, when the ES fault occurs on DF-CE link, BDF detects 113 the fault by the state change BFD control packet sent by DF, or BDF 114 detects the fault when the detection timer expires. Then BDF becomes 115 DF and will forward the BUM flows to CE. 117 3. Specification 119 [I-D.jain-bess-evpn-lsp-ping] section 4.3 defines an Ethernet AD sub- 120 TLV as a new Target FEC Stack sub-TLV. It is carried in the LSP-Ping 121 Echo Request message. BDF generates an LSP-Ping Echo Request message 122 which carries the associated ES AD sub-TLV. And BDF sends the 123 message with a local discriminator assigned by BDF for this BFD 124 session to DF. DF responds with the BFD control packet with 'Your 125 discriminator' set to the discriminator value received in the Echo 126 request message from the BDF. BDF can demultiplex the BFD session 127 based on the received 'Your Discriminator' field. 129 After the BFD session is established, when the link between DF and CE 130 fails, DF MUST send a BFD control packet with the value of State 131 field set to AdminDown through the established BFD session to BDF. 132 If DF is not operational, BDF also detects the failure when the BFD 133 detection time expires. Then BDF becomes DF immediately and forwards 134 the BUM flows to CE. 136 When the ES between 'old' DF and CE recovers, the BFD session MAY be 137 reused or a new BFD session can be established for the ES failover 138 monitor. 140 For the same example in last section, PE2 generates an LSP-Ping Echo 141 Request message which carries the associated ES AD sub-TLV and sends 142 the message with an assigned local discriminator to DF. PE1 responds 143 with a BFD control packet with 'Your discriminator' set to the 144 received discriminator from PE2. PE2 can demultiplex the BFD session 145 based on the received 'Your Discriminator' field. 147 When the link between PE1 and CE fails, PE1 sends a BFD control 148 packet with the state set to AdminDown to PE2 through the BFD 149 session. If the packet is lost, PE2 also can detect the fault by the 150 session detection time expiration. PE2 becomes DF immediately, then 151 the BUM packets can be forwarded to CE. 153 4. Security Considerations 155 This document does not introduce any new security considerations 156 other than already discussed in [RFC7432] and [RFC5884]. 158 5. IANA Considerations 160 There is no IANA consideration. 162 6. Normative References 164 [I-D.ietf-bess-evpn-df-election-framework] 165 Rabadan, J., satyamoh@cisco.com, s., Sajassi, A., Drake, 166 J., Nagaraj, K., and S. Sathappan, "Framework for EVPN 167 Designated Forwarder Election Extensibility", draft-ietf- 168 bess-evpn-df-election-framework-09 (work in progress), 169 January 2019. 171 [I-D.jain-bess-evpn-lsp-ping] 172 Jain, P., Salam, S., Sajassi, A., Boutros, S., and G. 173 Mirsky, "LSP-Ping Mechanisms for EVPN and PBB-EVPN", 174 draft-jain-bess-evpn-lsp-ping-08 (work in progress), 175 December 2018. 177 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 178 "Bidirectional Forwarding Detection (BFD) for MPLS Label 179 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 180 June 2010, . 182 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 183 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based 184 Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 185 2015, . 187 Authors' Addresses 188 Zheng(Sandy) Zhang 189 ZTE Corporation 190 No. 50 Software Ave, Yuhuatai Distinct 191 Nanjing 192 China 194 Email: zzhang_ietf@hotmail.com 196 Yubao Wang 197 ZTE Corporation 198 No. 50 Software Ave, Yuhuatai Distinct 199 Nanjing 200 China 202 Email: wang.yubao2@zte.com.cn 204 Greg Mirsky 205 ZTE Corporation 207 Email: gregimirsky@gmail.com