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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BIER Z. Zhang 3 Internet-Draft Juniper Networks 4 Intended status: Standards Track October 31, 2019 5 Expires: May 3, 2020 7 BIER Penultimate Hop Popping 8 draft-ietf-bier-php-04 10 Abstract 12 Bit Index Explicit Replication (BIER) can be used as provider tunnel 13 for Multicast Virtual Private Network (MVPN) [RFC6514], Global 14 Table Multicast [RFC7716] or Ethernet Virtual Private Network (EVPN) 15 [RFC7432]. It is possible that not all routers in the provider 16 network support BIER and there are various methods to handle BIER 17 incapable transit routers. However those methods assume the MVPN/ 18 EVPN Provider Edges (PEs) are BIER capable. This document specifies 19 a method to allow BIER incapable routers to act as MVPN/EVPN PEs with 20 BIER as the transport, by having the upstream BIER Forwarding Router 21 (BFR) that is connected directly or indirectly via a tunnel to a BIER 22 incapable PE remove the BIER header and send the payload to the PE. 24 Requirements Language 26 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 27 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 28 document are to be interpreted as described in RFC2119. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on May 3, 2020. 47 Copyright Notice 49 Copyright (c) 2019 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 65 2. Specifications . . . . . . . . . . . . . . . . . . . . . . . 3 66 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 67 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 68 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 69 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 70 6.1. Normative References . . . . . . . . . . . . . . . . . . 5 71 6.2. Informative References . . . . . . . . . . . . . . . . . 6 72 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 74 1. Introduction 76 The BIER architecture includes three layers: the "routing underlay", 77 the "BIER layer", and the "multicast flow overlay". The multicast 78 flow overlay is responsible for the BIER Forwarding Egress Routers 79 (BFERs) to signal to BIER Forwarding Ingress Routers (BFIRs) that 80 they are interested in receiving certain multicast flows so that 81 BFIRs can encode the correct bitstring for BIER forwarding by the 82 BIER layer. 84 MVPN and EVPN are two similar overlays where BGP Auto-Discovery 85 routes for MVPN/EVPN are exchanged among all PEs to signal which PEs 86 need to receive multicast traffic for all or certain flows. 87 Typically the same provider tunnel type is used for traffic to reach 88 all receiving PEs. 90 Consider an MVPN/EVPN deployment where enough provider routers are 91 BIER capable for BIER to become the preferred the choice of provider 92 tunnel. However, some PEs cannot be upgraded to support BIER 93 forwarding. While there are ways to allow an ingress PE to send 94 traffic to some PEs with one type of tunnel and send traffic to some 95 other PEs with a different type of tunnel, the procedure becomes 96 complicated and forwarding is not optimized. 98 One way to solve this problem is to use Penultimate Hop Popping (PHP) 99 so that the upstream BFR can pop the BIER header and send the payload 100 "natively" (note that the upstream BFR can be connected directly or 101 indirectly via any type of tunnel to the PE). This is similar to 102 Multi-Protocol Label Switching (MPLS) PHP though it is the BIER 103 header that is popped. 105 The transition of an existing MVPN/EVPN deployment with traditional 106 provider tunnels to using BIER with some PEs not capable of receiving 107 BIER packets can be incremental. All PEs are first upgraded to 108 support BIER at least in the control plane, with those not capable of 109 BIER forwarding requesting PHP. Then BIER capable ingress PEs 110 independently and incrementally switch to BIER transport. 112 While the above text uses MVPN/EVPN as example, BIER PHP is 113 applicable to any scenario where the multicast flow overlay edge 114 router does not support BIER, as long as the edge router does not 115 need to know the transmitting BFIR or participate in BIER OAM 116 procedures. 118 This works well if a BIER incapable PE only needs to receive 119 multicast traffic. If it needs to send multicast traffic as well, 120 then it must Ingress Replicate to a BIER capable helper PE, who will 121 in turn relay the packet to other PEs. The helper PE is either a 122 Virtual Hub as specified in [RFC7024] for MVPN and [I-D.keyupate- 123 bess-evpn-virtual-hub] for EVPN, or an AR-Replicator as specified in 124 [I-D.ietf-bess-evpn-optimized-ir] for EVPN. 126 2. Specifications 128 The procedures in this section apply only if, by means outside the 129 scope of this document, it is known that the payload after BIER 130 header is one of the following: 132 o MPLS packets with downstream-assigned label at top of stack (i.e., 133 the Proto field in the BIER header is 1). For example, a label 134 from a Domain-wide Common Block (DCB) is used as specified in [I- 135 D.ietf-bess-mvpn-evpn-aggregation-label]. 137 o IPv4/IPv6 multicast packets for which Reverse Path Forwarding 138 check is disabled. 140 A BIER incapable router, if acting as a multicast flow overlay 141 router, MUST signal its BIER information as specified in [RFC8401] or 142 [RFC8444] or [I-D.ietf-bier-idr-extensions], with a PHP sub-sub-TLV 143 included in the BIER sub-TLV attached to the BIER incapable router's 144 BIER prefix to request BIER PHP from other BFRs. The sub-sub-TLV's 145 type is TBD, and the length is 0. 147 With MPLS encapsulation, the BIER incapable multicast flow overlay 148 router MAY omit the BIER MPLS Encapsulation sub-sub-TLV, or MUST set 149 the Label field in BIER MPLS Encapsulation sub-sub-TLV to Implicit 150 Null Label [RFC3032]. 152 With MPLS encapsulation, if a BFER does not support certain BSL, it 153 MAY still advertise a corresponding BIER MPLS Encapsulation sub-TLV 154 but set the Label field to Implicit Null Label. 156 If a BFR follows section 6.9 of [RFC8279] to handle BIER incapable 157 routers, it must treat a router as BIER incapable if the label 158 advertised by the router is Implicit Null, or if the router 159 advertises a PHP sub-sub-TLV, so that the router is not used as a 160 transit BFR. 162 If the downstream neighbor for a BIER prefix is the one advertising 163 the prefix with a PHP sub-sub-TLV or with an Implicit Null Label in 164 the Label field in its BIER MPLS Encapsulation sub-sub-TLV, then when 165 the corresponding BIRT or BIFT entry is created/updated, the 166 forwarding behavior MUST be that the BIER header is removed and the 167 payload be sent to the downstream router without the BIER header, 168 either directly or over any type of tunnel. 170 3. Security Considerations 172 This specification does not introduce additional security concerns 173 beyond those already discussed in BIER architecture and OSPF/ISIS/BGP 174 extensions for BIER signaling. 176 4. IANA Considerations 178 This document requests a new sub-sub-TLV type value from the "Sub- 179 sub-TLVs for BIER Info Sub-TLV" registry in the "IS-IS TLV 180 Codepoints" registry: 182 Type Name 183 ---- ---- 184 TBD BIER PHP Request 186 This document also requests a new sub-TLV type value from the OSPFv2 187 Extended Prefix TLV Sub-TLV registry: 189 Type Name 190 ---- ---- 191 TBD BIER PHP Request 193 5. Acknowledgements 195 The author wants to thank Eric Rosen and Antonie Przygienda for their 196 review, comments and suggestions. The author also wants to thank 197 Senthil Dhanaraj for his suggestion of requesting PHP if a BFER does 198 not support certain BSL. 200 6. References 202 6.1. Normative References 204 [I-D.ietf-bess-mvpn-evpn-aggregation-label] 205 Zhang, Z., Rosen, E., Lin, W., Li, Z., and I. Wijnands, 206 "MVPN/EVPN Tunnel Aggregation with Common Labels", draft- 207 ietf-bess-mvpn-evpn-aggregation-label-03 (work in 208 progress), October 2019. 210 [I-D.ietf-bier-evpn] 211 Zhang, Z., Przygienda, T., Sajassi, A., and J. Rabadan, 212 "EVPN BUM Using BIER", draft-ietf-bier-evpn-01 (work in 213 progress), April 2018. 215 [I-D.ietf-bier-idr-extensions] 216 Xu, X., Chen, M., Patel, K., Wijnands, I., and T. 217 Przygienda, "BGP Extensions for BIER", draft-ietf-bier- 218 idr-extensions-07 (work in progress), September 2019. 220 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 221 Requirement Levels", BCP 14, RFC 2119, 222 DOI 10.17487/RFC2119, March 1997, 223 . 225 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 226 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 227 Explicit Replication (BIER)", RFC 8279, 228 DOI 10.17487/RFC8279, November 2017, 229 . 231 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 232 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 233 for Bit Index Explicit Replication (BIER) in MPLS and Non- 234 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 235 2018, . 237 [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. 238 Zhang, "Bit Index Explicit Replication (BIER) Support via 239 IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, 240 . 242 [RFC8444] Psenak, P., Ed., Kumar, N., Wijnands, IJ., Dolganow, A., 243 Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2 244 Extensions for Bit Index Explicit Replication (BIER)", 245 RFC 8444, DOI 10.17487/RFC8444, November 2018, 246 . 248 6.2. Informative References 250 [I-D.ietf-bess-evpn-optimized-ir] 251 Rabadan, J., Sathappan, S., Lin, W., Katiyar, M., and A. 252 Sajassi, "Optimized Ingress Replication solution for 253 EVPN", draft-ietf-bess-evpn-optimized-ir-06 (work in 254 progress), October 2018. 256 [I-D.keyupate-bess-evpn-virtual-hub] 257 Patel, K., Sajassi, A., Drake, J., Zhang, Z., and W. 258 Henderickx, "Virtual Hub-and-Spoke in BGP EVPNs", draft- 259 keyupate-bess-evpn-virtual-hub-02 (work in progress), 260 September 2019. 262 [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ 263 BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 264 2012, . 266 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 267 Encodings and Procedures for Multicast in MPLS/BGP IP 268 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 269 . 271 [RFC7024] Jeng, H., Uttaro, J., Jalil, L., Decraene, B., Rekhter, 272 Y., and R. Aggarwal, "Virtual Hub-and-Spoke in BGP/MPLS 273 VPNs", RFC 7024, DOI 10.17487/RFC7024, October 2013, 274 . 276 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 277 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based 278 Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 279 2015, . 281 Author's Address 283 Zhaohui Zhang 284 Juniper Networks 286 EMail: zzhang@juniper.net