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Mirsky 10 ZTE Corp. 11 July 28, 2020 13 BFD for VXLAN 14 draft-ietf-bfd-vxlan-14 16 Abstract 18 This document describes the use of the Bidirectional Forwarding 19 Detection (BFD) protocol in point-to-point Virtual eXtensible Local 20 Area Network (VXLAN) tunnels used to form an overlay network. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at https://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on January 29, 2021. 39 Copyright Notice 41 Copyright (c) 2020 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (https://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Conventions Used in this Document . . . . . . . . . . . . . . 3 58 2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 60 3. Deployment . . . . . . . . . . . . . . . . . . . . . . . . . 4 61 4. Use of the Management VNI . . . . . . . . . . . . . . . . . . 5 62 5. BFD Packet Transmission over VXLAN Tunnel . . . . . . . . . . 6 63 6. Reception of BFD Packet from VXLAN Tunnel . . . . . . . . . . 8 64 7. Echo BFD . . . . . . . . . . . . . . . . . . . . . . . . . . 8 65 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 66 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 67 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 68 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 69 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 70 12.1. Normative References . . . . . . . . . . . . . . . . . . 10 71 12.2. Informational References . . . . . . . . . . . . . . . . 10 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 74 1. Introduction 76 "Virtual eXtensible Local Area Network" (VXLAN) [RFC7348] provides an 77 encapsulation scheme that allows building an overlay network by 78 decoupling the address space of the attached virtual hosts from that 79 of the network. 81 One use of VXLAN is in data centers interconnecting virtual machines 82 (VMs) of a tenant. VXLAN addresses requirements of the Layer 2 and 83 Layer 3 data center network infrastructure in the presence of VMs in 84 a multi-tenant environment by providing a Layer 2 overlay scheme on a 85 Layer 3 network [RFC7348]. Another use is as an encapsulation for 86 Ethernet VPN [RFC8365]. 88 This document is written assuming the use of VXLAN for virtualized 89 hosts and refers to VMs and VXLAN Tunnel End Points (VTEPs) in 90 hypervisors. However, the concepts are equally applicable to non- 91 virtualized hosts attached to VTEPs in switches. 93 In the absence of a router in the overlay, a VM can communicate with 94 another VM only if they are on the same VXLAN segment. VMs are 95 unaware of VXLAN tunnels as a VXLAN tunnel is terminated on a VTEP. 97 VTEPs are responsible for encapsulating and decapsulating frames 98 exchanged among VMs. 100 The ability to monitor path continuity, i.e., perform proactive 101 continuity check (CC) for point-to-point (p2p) VXLAN tunnels, is 102 important. The asynchronous mode of BFD, as defined in [RFC5880], is 103 used to monitor a p2p VXLAN tunnel. 105 In the case where a Multicast Service Node (MSN) (as described in 106 Section 3.3 of [RFC8293]) participates in VXLAN, the mechanisms 107 described in this document apply and can, therefore, be used to test 108 the connectivity from the source NVE to the MSN. 110 This document describes the use of Bidirectional Forwarding Detection 111 (BFD) protocol to enable monitoring continuity of the path between 112 VXLAN VTEPs that are performing as Network Virtualization Endpoints, 113 and/or availability of a replicator MSN using a Management VNI 114 (Section 4). All other uses of the specification to test toward 115 other VXLAN endpoints are out of the scope. 117 2. Conventions Used in this Document 119 2.1. Acronyms 121 BFD Bidirectional Forwarding Detection 123 CC Continuity Check 125 p2p Point-to-point 127 MSN Multicast Service Node 129 NVE Network Virtualization Endpoint 131 VFI Virtual Forwarding Instance 133 VM Virtual Machine 135 VNI VXLAN Network Identifier (or VXLAN Segment ID) 137 VTEP VXLAN Tunnel End Point 139 VXLAN Virtual eXtensible Local Area Network 141 2.2. Requirements Language 143 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 144 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 145 "OPTIONAL" in this document are to be interpreted as described in BCP 146 14 [RFC2119] [RFC8174] when, and only when, they appear in all 147 capitals, as shown here. 149 3. Deployment 151 Figure 1 illustrates the scenario with two servers, each of them 152 hosting two VMs. The servers host VTEPs that terminate two VXLAN 153 tunnels with VXLAN Network Identifier (VNI) number 100 and 200 154 respectively. Separate BFD sessions can be established between the 155 VTEPs (IP1 and IP2) for monitoring each of the VXLAN tunnels (VNI 100 156 and 200). Using a BFD session to monitor a set of VXLAN VNIs between 157 the same pair of VTEPs might help to detect and localize problems 158 caused by misconfiguration. An implementation that supports this 159 specification MUST be able to control the number of BFD sessions that 160 can be created between the same pair of VTEPs. This method is 161 applicable whether the VTEP is a virtual or physical device. 163 +------------+-------------+ 164 | Server 1 | 165 | +----+----+ +----+----+ | 166 | |VM1-1 | |VM1-2 | | 167 | |VNI 100 | |VNI 200 | | 168 | | | | | | 169 | +---------+ +---------+ | 170 | VTEP (IP1) | 171 +--------------------------+ 172 | 173 | +-------------+ 174 | | Layer 3 | 175 +---| Network | 176 +-------------+ 177 | 178 +-----------+ 179 | 180 +------------+-------------+ 181 | VTEP (IP2) | 182 | +----+----+ +----+----+ | 183 | |VM2-1 | |VM2-2 | | 184 | |VNI 100 | |VNI 200 | | 185 | | | | | | 186 | +---------+ +---------+ | 187 | Server 2 | 188 +--------------------------+ 190 Figure 1: Reference VXLAN Domain 192 At the same time, a service layer BFD session may be used between the 193 tenants of VTEPs IP1 and IP2 to provide end-to-end fault management 194 (this use case is outside the scope of this document). In such a 195 case, for VTEPs BFD Control packets of that session are 196 indistinguishable from data packets. 198 For BFD Control packets encapsulated in VXLAN (Figure 2), the inner 199 destination IP address SHOULD be set to one of the loopback addresses 200 from 127/8 range for IPv4 or to one of IPv4-mapped IPv6 loopback 201 addresses from ::ffff:127.0.0.0/104 range for IPv6. 203 4. Use of the Management VNI 205 In most cases, a single BFD session is sufficient for the given VTEP 206 to monitor the reachability of a remote VTEP, regardless of the 207 number of VNIs. When the single BFD session is used to monitor the 208 reachability of the remote VTEP, an implementation SHOULD choose any 209 of the VNIs. An implementation that supports this specification MUST 210 support the use of the Management VNI as control and management 211 channel between VTEPs. The selection of the VNI number of the 212 Management VNI MUST be controlled through a management plane. An 213 implementation MAY use VNI number 1 as the default value for the 214 Management VNI. All VXLAN packets received on the Management VNI 215 MUST be processed locally and MUST NOT be forwarded to a tenant. 217 5. BFD Packet Transmission over VXLAN Tunnel 219 BFD packets MUST be encapsulated and sent to a remote VTEP as 220 explained in this section. Implementations SHOULD ensure that the 221 BFD packets follow the same forwarding path as VXLAN data packets 222 within the sender system. 224 BFD packets are encapsulated in VXLAN as described below. The VXLAN 225 packet format is defined in Section 5 of [RFC7348]. The value in the 226 VNI field of the VXLAN header MUST be set to the value selected as 227 the Management VNI. The Outer IP/UDP and VXLAN headers MUST be 228 encoded by the sender as defined in [RFC7348]. 230 0 1 2 3 231 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 1 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 233 | | 234 ~ Outer Ethernet Header ~ 235 | | 236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 237 | | 238 ~ Outer IPvX Header ~ 239 | | 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 241 | | 242 ~ Outer UDP Header ~ 243 | | 244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 245 | | 246 ~ VXLAN Header ~ 247 | | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | | 250 ~ Inner Ethernet Header ~ 251 | | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | | 254 ~ Inner IPvX Header ~ 255 | | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 | | 258 ~ Inner UDP Header ~ 259 | | 260 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 | | 262 ~ BFD Control Packet ~ 263 | | 264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 265 | Outer Ethernet FCS | 266 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 268 Figure 2: VXLAN Encapsulation of BFD Control Packet 270 The BFD packet MUST be carried inside the inner Ethernet frame of the 271 VXLAN packet. The choice of Destination MAC and Destination IP 272 addresses for the inner Ethernet frame MUST ensure that the BFD 273 Control packet is not forwarded to a tenant but is processed locally 274 at the remote VTEP. The inner Ethernet frame carrying the BFD 275 Control packet- has the following format: 277 Ethernet Header: 279 Destination MAC: A Management VNI, which does not have any 280 tenants, will have no dedicated MAC address for decapsulated 281 traffic. The value [TBD1] SHOULD be used in this field. 283 Source MAC: MAC address associated with the originating VTEP. 285 IP header: 287 Destination IP: IP address MUST NOT be of one of tenant's IP 288 addresses. The IP address SHOULD be selected from the range 289 127/8 for IPv4, for IPv6 - from the range ::ffff:127.0.0.0/104. 290 Alternatively, the destination IP address MAY be set to VTEP's 291 IP address. 293 Source IP: IP address of the originating VTEP. 295 TTL or Hop Limit: MUST be set to 255 in accordance with 296 [RFC5881]. 298 The fields of the UDP header and the BFD Control packet are 299 encoded as specified in [RFC5881]. 301 6. Reception of BFD Packet from VXLAN Tunnel 303 Once a packet is received, the VTEP MUST validate the packet. If the 304 packet is received on the management VNI and is identified as BFD 305 control packet addressed to the VTEP, and then the packet can be 306 processed further. Processing of BFD control packets received on 307 non-management VNI is outside the scope of this specification. 309 The received packet's inner IP payload is then validated according to 310 Sections 4 and 5 in [RFC5881]. 312 7. Echo BFD 314 Support for echo BFD is outside the scope of this document. 316 8. IANA Considerations 318 IANA is requested to assign a single MAC address to the value TBD1 319 from the "IANA Unicast 48-bit MAC Address" registry from the 320 "Unassigned (small allocations)" block. The Usage field will be "BFD 321 for VXLAN" with a Reference field of this document. 323 9. Security Considerations 325 Security issues discussed in [RFC5880], [RFC5881], and [RFC7348] 326 apply to this document. 328 This document recommends using an address from the Internal host 329 loopback addresses 127/8 range for IPv4 or an IP4-mapped IPv6 330 loopback address from ::ffff:127.0.0.0/104 range for IPv6 as the 331 destination IP address in the inner IP header. Using such an address 332 prevents the forwarding of the encapsulated BFD control message by a 333 transient node in case the VXLAN tunnel is broken as according to 334 [RFC1812]. 336 A router SHOULD NOT forward, except over a loopback interface, any 337 packet that has a destination address on network 127. A router 338 MAY have a switch that allows the network manager to disable these 339 checks. If such a switch is provided, it MUST default to 340 performing the checks. 342 The use of IPv4-mapped IPv6 addresses has the same property as using 343 the IPv4 network 127/8, moreover, the IPv4-mapped IPv6 addresses 344 prefix is not advertised in any routing protocol. 346 If the implementation supports establishing multiple BFD sessions 347 between the same pair of VTEPs, there SHOULD be a mechanism to 348 control the maximum number of such sessions that can be active at the 349 same time. 351 10. Contributors 353 Reshad Rahman 354 rrahman@cisco.com 355 Cisco 357 11. Acknowledgments 359 Authors would like to thank Jeff Haas of Juniper Networks for his 360 reviews and feedback on this material. 362 Authors would also like to thank Nobo Akiya, Marc Binderberger, 363 Shahram Davari, Donald E. Eastlake 3rd, Anoop Ghanwani, Dinesh Dutt, 364 Joel Halpern, and Carlos Pignataro for the extensive reviews and the 365 most detailed and constructive comments. 367 12. References 369 12.1. Normative References 371 [RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers", 372 RFC 1812, DOI 10.17487/RFC1812, June 1995, 373 . 375 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 376 Requirement Levels", BCP 14, RFC 2119, 377 DOI 10.17487/RFC2119, March 1997, 378 . 380 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 381 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 382 . 384 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 385 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 386 DOI 10.17487/RFC5881, June 2010, 387 . 389 [RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger, 390 L., Sridhar, T., Bursell, M., and C. Wright, "Virtual 391 eXtensible Local Area Network (VXLAN): A Framework for 392 Overlaying Virtualized Layer 2 Networks over Layer 3 393 Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014, 394 . 396 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 397 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 398 May 2017, . 400 12.2. Informational References 402 [RFC8293] Ghanwani, A., Dunbar, L., McBride, M., Bannai, V., and R. 403 Krishnan, "A Framework for Multicast in Network 404 Virtualization over Layer 3", RFC 8293, 405 DOI 10.17487/RFC8293, January 2018, 406 . 408 [RFC8365] Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R., 409 Uttaro, J., and W. Henderickx, "A Network Virtualization 410 Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365, 411 DOI 10.17487/RFC8365, March 2018, 412 . 414 Authors' Addresses 416 Santosh Pallagatti (editor) 417 VMware 419 Email: santosh.pallagatti@gmail.com 421 Sudarsan Paragiri 422 Individual Contributor 424 Email: sudarsan.225@gmail.com 426 Vengada Prasad Govindan 427 Cisco 429 Email: venggovi@cisco.com 431 Mallik Mudigonda 432 Cisco 434 Email: mmudigon@cisco.com 436 Greg Mirsky 437 ZTE Corp. 439 Email: gregimirsky@gmail.com