idnits 2.17.1 draft-mirsky-mpls-p2mp-bfd-10.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (April 17, 2020) is 1442 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-15) exists of draft-ietf-bess-mvpn-fast-failover-10 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS Working Group G. Mirsky 3 Internet-Draft ZTE Corp. 4 Intended status: Standards Track April 17, 2020 5 Expires: October 19, 2020 7 BFD for Multipoint Networks over Point-to-Multi-Point MPLS LSP 8 draft-mirsky-mpls-p2mp-bfd-10 10 Abstract 12 This document describes procedures for using Bidirectional Forwarding 13 Detection (BFD) for multipoint networks to detect data plane failures 14 in Multiprotocol Label Switching (MPLS) point-to-multipoint (p2mp) 15 Label Switched Paths (LSPs) using active tails with unsolicited 16 notifications mode. It also describes the applicability of LSP Ping, 17 as in-band, and the control plane, as out-band, solutions to 18 bootstrap a BFD session in this environment. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on October 19, 2020. 37 Copyright Notice 39 Copyright (c) 2020 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (https://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Conventions used in this document . . . . . . . . . . . . . . 2 56 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 57 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 58 3. Multipoint BFD Encapsulation . . . . . . . . . . . . . . . . 3 59 3.1. IP Encapsulation of Multipoint BFD . . . . . . . . . . . 3 60 3.2. Non-IP Encapsulation of Multipoint BFD . . . . . . . . . 4 61 4. Bootstrapping Multipoint BFD . . . . . . . . . . . . . . . . 4 62 4.1. LSP Ping . . . . . . . . . . . . . . . . . . . . . . . . 4 63 4.2. Operation of Multipoint BFD with Active Tail over P2MP 64 MPLS LSP . . . . . . . . . . . . . . . . . . . . . . . . 5 65 4.3. Control Plane . . . . . . . . . . . . . . . . . . . . . . 7 66 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 67 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 68 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 69 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 70 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 71 8.2. Informative References . . . . . . . . . . . . . . . . . 9 72 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 74 1. Introduction 76 [RFC8562] defines a method of using Bidirectional Detection (BFD) 77 [RFC5880] to monitor and detect unicast failures between the sender 78 (head) and one or more receivers (tails) in multipoint or multicast 79 networks. [RFC8562] added two BFD session types - MultipointHead and 80 MultipointTail. Throughout this document, MultipointHead and 81 MultipointTail refer to the value bfd.SessionType is set on a BFD 82 system. This document describes procedures for using such mode of 83 BFD protocol to detect data plane failures in Multiprotocol Label 84 Switching (MPLS) point-to-multipoint (p2mp) Label Switched Paths 85 (LSPs). The document also describes the applicability of out-band 86 solutions to bootstrap a BFD session in this environment. 88 2. Conventions used in this document 90 2.1. Terminology 92 MPLS: Multiprotocol Label Switching 94 LSP: Label Switched Path 96 BFD: Bidirectional Forwarding Detection 97 p2mp: Point-to-Multipoint 99 FEC: Forwarding Equivalence Class 101 G-ACh: Generic Associated Channel 103 ACH: Associated Channel Header 105 GAL: G-ACh Label 107 2.2. Requirements Language 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 111 "OPTIONAL" in this document are to be interpreted as described in BCP 112 14 [RFC2119] [RFC8174] when, and only when, they appear in all 113 capitals, as shown here. 115 3. Multipoint BFD Encapsulation 117 [RFC8562] uses BFD in the Demand mode from the very start of a point- 118 to-multipoint (p2mp) BFD session. Because the head doesn't receive 119 any BFD control packet from a tail, the head of the p2mp BFD session 120 transmits all BFD control packets with the value of Your 121 Discriminator field set to zero. As a result, a tail cannot 122 demultiplex BFD sessions using Your Discriminator, as defined in 123 [RFC5880]. [RFC8562] requires that to demultiplex BFD sessions, the 124 tail uses the source IP address, My Discriminator, and the identity 125 of the multipoint tree from which the BFD control packet was 126 received. The p2mp MPLS LSP label MAY provide the identification of 127 the multipoint tree in case of inclusive p-tree or upstream assigned 128 label in case of aggregate p-tree. If the BFD control packet is 129 encapsulated in IP/UDP, then the source IP address MUST be used to 130 demultiplex the received BFD control packet as described in 131 Section 3.1. The non-IP encapsulation case is described in 132 Section 3.2. 134 3.1. IP Encapsulation of Multipoint BFD 136 [RFC8562] defines IP/UDP encapsulation for multipoint BFD over p2mp 137 MPLS LSP: 139 UDP destination port MUST be set to 3784; 141 destination IP address MUST be set to one of the loopback 142 addresses from 127/8 range for IPv4 or to one of IPv4-mapped IPv4 143 loopback addresses from ::ffff:127.0.0.0/104 range for IPv6.; 145 This specification further clarifies that: 147 if multiple alternative paths for the given p2mp LSP Forwarding 148 Equivalence Class (FEC) exist, the MultipointHead SHOULD use 149 Entropy Label [RFC6790] used for LSP Ping [RFC8029] to exercise 150 that particular alternative path; 152 or the MultipointHead MAY use the UDP port number as discovered by 153 LSP Ping traceroute [RFC8029] as the source UDP port number to 154 possibly exercise that particular alternate path. 156 3.2. Non-IP Encapsulation of Multipoint BFD 158 In some environments, the overhead of extra IP/UDP encapsulations may 159 be considered as overburden thus making the use of more compact G-ACh 160 encapsulation attractive. Also, the validation of the IP/UDP 161 encapsulation of BFD control packet of p2mp BFD session may fail 162 because of a problem not related to neither MPLS label stack nor to 163 BFD. Avoiding unnecessary encapsulation of p2mp BFD over MPLS LSP 164 improves the accuracy of the correlation of the detected failure and 165 defect in MPLS LSP. Non-IP encapsulation for multipoint BFD over 166 p2mp MPLS LSP MUST use Generic Associated Channel (G-ACh) Label (GAL) 167 (see [RFC5586]) at the bottom of the label stack followed by 168 Associated Channel Header (ACH). If BFD Control, PW-ACH 169 encapsulation (without IP/UDP Headers) channel to be used in ACH, an 170 implementation would not be able to verify the identity of the 171 MultipointHead and, as a result, will not properly demultiplex BFD 172 packets. Hence, a new channel type value is needed. The Channel 173 Type field in ACH MUST be set to TBA1 value Section 6. To provide 174 the identity of the MultipointHead for the particular multipoint BFD 175 session a Source Address TLV [RFC7212] MUST immediately follow a BFD 176 control message. 178 4. Bootstrapping Multipoint BFD 180 4.1. LSP Ping 182 LSP Ping is the part of on-demand OAM toolset to detect and localize 183 defects in the data plane, and verify the control plane against the 184 data plane by ensuring that the LSP is mapped to the same FEC, at the 185 egress, as the ingress. 187 LSP Ping, as defined in [RFC6425], MAY be used to bootstrap 188 MultipointTail. If the LSP Ping used, it MUST include the Target FEC 189 TLV and the BFD Discriminator TLV defined in [RFC5884]. The Target 190 FEC TLV MUST use sub-TLVs defined in Section 3.1 [RFC6425]. It is 191 RECOMMENDED setting the value of Reply Mode field to "Do not reply" 192 [RFC8029] for the LSP Ping to bootstrap MultipointTail of the p2mp 193 BFD session. Indeed, because BFD over a multipoint network is using 194 BFD Demand mode, the LSP echo reply from a tail has no useful 195 information to convey to the head, unlike in case of the BFD over a 196 p2p MPLS LSP [RFC5884]. A MultipointTail that receives the LSP Ping 197 that includes the BFD Discriminator TLV: 199 o MUST validate the LSP Ping; 201 o MUST associate the received BFD Discriminator value with the p2mp 202 LSP; 204 o MUST create p2mp BFD session and set bfd.SessionType = 205 MultipointTail as described in [RFC8562]; 207 o MUST use the source IP address of LSP Ping, the value of BFD 208 Discriminator from the BFD Discriminator TLV, and the identity of 209 the p2mp LSP to properly demultiplex BFD sessions. 211 Besides bootstrapping a BFD session over a p2mp LSP, LSP Ping SHOULD 212 be used to verify the control plane against the data plane 213 periodically by checking that the p2mp LSP is mapped to the same FEC 214 at the MultipointHead and all active MultipointTails. The rate of 215 generation of these LSP Ping Echo request messages SHOULD be 216 significantly less than the rate of generation of the BFD Control 217 packets because LSP Ping requires more processing to validate the 218 consistency between the data plane and the control plane. An 219 implementation MAY provide configuration options to control the rate 220 of generation of the periodic LSP Ping Echo request messages. 222 4.2. Operation of Multipoint BFD with Active Tail over P2MP MPLS LSP 224 [RFC8562] defined how the BFD Demand mode can be used in multipoint 225 networks. When applied in MPLS, procedures specified in [RFC8562] 226 allow an egress LSR to detect a failure of the part of the MPLS p2mp 227 LSP from the ingress LSR. The ingress LSR is not aware of the state 228 of the p2mp LSP. [RFC8563], using mechanisms defined in [RFC8562], 229 defined an "active tail" behavior. An active tail might notify the 230 head of the detected failure and responds to a poll sequence 231 initiated by the head. The first method, referred to as Head 232 Notification without Polling, is mentioned in Section 5.2.1 233 [RFC8563], is the simplest of all described in [RFC8563]. The use of 234 this method in BFD over MPLS p2mp LSP is discussed in this document. 235 Analysis of other methods of a head learning of the state of an MPLS 236 p2mp LSP is outside the scope of this document. 238 As specified in [RFC8563] for the active tail mode BFD variables MUST 239 be as follows: 241 On an ingress LSR: 243 o bfd.SessionType is MultipointHead; 245 o bfd.RequiredMinRxInterval is set to nonzero allowing egress LSRs 246 to send BFD Control packets. 248 On an egress LSR: 250 o bfd.SessionType is MultipointTail; 252 o bfd.SilentTail is set to zero. 254 In Section 5.2.1 [RFC8563] is noted that "the tail sends unsolicited 255 BFD packets in response to the detection of a multipoint path 256 failure" but without the specifics on the information in the packet 257 and frequency of transmissions. This document defines the procedure 258 of the active tail with unsolicited notifications for p2mp MPLS LSP 259 as specified below. 261 Upon detecting the failure of the p2mp MPLS LSP, an egress LSR sends 262 BFD control packet with the following settings: 264 o the Poll (P) bit is set; 266 o the Status (Sta) field set to Down value; 268 o the Diagnostic (Diag) field set to Control Detection Time Expired 269 value; 271 o the value of the Your Discriminator field is set to the value the 272 egress LSR has been using to demultiplex that BFD multipoint 273 session; 275 o BFD Control packet is encapsulated in IP/UDP with the destination 276 IP address of the ingress LSR and the UDP destination port number 277 set to 4784 per [RFC5883] 279 o these BFD Control packets are transmitted at the rate of one per 280 second until either it receives the valid for this BFD session 281 control packet with the Final (F) bit set from the ingress LSR or 282 the defect condition clears. 284 To improve the likelihood of notifying the ingress LSR of the failure 285 of the p2mp MPLS LSP, the egress LSR SHOULD transmit three BFD 286 Control packets defined above in short succession. 288 An ingress LSR that has received the BFD Control packet, as described 289 above, sends the unicast IP/UDP encapsulated BFD control packet with 290 the Final (F) bit set to the egress LSR. 292 4.3. Control Plane 294 BGP-BFD Attribute [I-D.ietf-bess-mvpn-fast-failover] MAY be used to 295 bootstrap multipoint BFD session on a tail. 297 5. Security Considerations 299 This document does not introduce new security aspects but inherits 300 all security considerations from [RFC5880], [RFC5884], [RFC7726], 301 [RFC8562], [RFC8029], and [RFC6425]. 303 Also, BFD for p2mp MPLS LSP MUST follow the requirements listed in 304 section 4.1 [RFC4687] to avoid congestion in the control plane or the 305 data plane caused by the rate of generating BFD control packets. An 306 operator SHOULD consider the amount of extra traffic generated by 307 p2mp BFD when selecting the interval at which the MultipointHead will 308 transmit BFD control packets. Also, the operator MAY consider the 309 size of the packet the MultipointHead transmits periodically as using 310 IP/UDP encapsulation adds up to 28 octets, which is more than 50% of 311 BFD control packet length, comparing to G-ACh encapsulation. 313 6. IANA Considerations 315 IANA is requested to allocate value (TBA1) from its MPLS Generalized 316 Associated Channel (G-ACh) Types registry. 318 +-------+------------------------+---------------+ 319 | Value | Description | Reference | 320 +-------+------------------------+---------------+ 321 | TBA1 | Multipoint BFD Session | This document | 322 +-------+------------------------+---------------+ 324 Table 1: Multipoint BFD Session G-ACh Type 326 7. Acknowledgements 328 The author sincerely appreciates the comments received from Andrew 329 Malis and thought stimulating questions from Carlos Pignataro. 331 8. References 332 8.1. Normative References 334 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 335 Requirement Levels", BCP 14, RFC 2119, 336 DOI 10.17487/RFC2119, March 1997, 337 . 339 [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., 340 "MPLS Generic Associated Channel", RFC 5586, 341 DOI 10.17487/RFC5586, June 2009, 342 . 344 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 345 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 346 . 348 [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 349 (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, 350 June 2010, . 352 [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, 353 "Bidirectional Forwarding Detection (BFD) for MPLS Label 354 Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, 355 June 2010, . 357 [RFC6425] Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A., 358 Yasukawa, S., and T. Nadeau, "Detecting Data-Plane 359 Failures in Point-to-Multipoint MPLS - Extensions to LSP 360 Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011, 361 . 363 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and 364 L. Yong, "The Use of Entropy Labels in MPLS Forwarding", 365 RFC 6790, DOI 10.17487/RFC6790, November 2012, 366 . 368 [RFC7212] Frost, D., Bryant, S., and M. Bocci, "MPLS Generic 369 Associated Channel (G-ACh) Advertisement Protocol", 370 RFC 7212, DOI 10.17487/RFC7212, June 2014, 371 . 373 [RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S. 374 Aldrin, "Clarifying Procedures for Establishing BFD 375 Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726, 376 DOI 10.17487/RFC7726, January 2016, 377 . 379 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 380 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 381 Switched (MPLS) Data-Plane Failures", RFC 8029, 382 DOI 10.17487/RFC8029, March 2017, 383 . 385 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 386 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 387 May 2017, . 389 [RFC8562] Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky, 390 Ed., "Bidirectional Forwarding Detection (BFD) for 391 Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562, 392 April 2019, . 394 [RFC8563] Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky, 395 Ed., "Bidirectional Forwarding Detection (BFD) Multipoint 396 Active Tails", RFC 8563, DOI 10.17487/RFC8563, April 2019, 397 . 399 8.2. Informative References 401 [I-D.ietf-bess-mvpn-fast-failover] 402 Morin, T., Kebler, R., and G. Mirsky, "Multicast VPN fast 403 upstream failover", draft-ietf-bess-mvpn-fast-failover-10 404 (work in progress), February 2020. 406 [RFC4687] Yasukawa, S., Farrel, A., King, D., and T. Nadeau, 407 "Operations and Management (OAM) Requirements for Point- 408 to-Multipoint MPLS Networks", RFC 4687, 409 DOI 10.17487/RFC4687, September 2006, 410 . 412 Author's Address 414 Greg Mirsky 415 ZTE Corp. 417 Email: gregimirsky@gmail.com