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'I-D.keyupate-bess-evpn-virtual-hub' Summary: 1 error (**), 0 flaws (~~), 12 warnings (==), 2 comments (--). 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 August 3, 2018 5 Expires: February 4, 2019 7 BIER Penultimate Hop Popping 8 draft-zzhang-bier-php-01 10 Abstract 12 Bit Index Explicit Replication (BIER) can be used as provider tunnel 13 for MVPN/GTM [RFC6514] [RFC7716] or EVPN BUM [RFC7432]. It is 14 possible that not all routers in the provider network support BIER 15 and there are various methods to handle BIER incapable transit 16 routers. However the MVPN/EVPN PEs are assumed to be BIER capable - 17 they are BFIRs/BFERs. This document specifies a method to allow BIER 18 incapable routers to act as MVPN/EVPN PEs with BIER as the transport, 19 by having the upstream BFR (connected directly or indirectly via a 20 tunnel) of a PE remove the BIER header and send the payload to the 21 PE. 23 Requirements Language 25 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 26 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 27 document are to be interpreted as described in RFC2119. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on February 4, 2019. 46 Copyright Notice 48 Copyright (c) 2018 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 2 64 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 65 3. Specifications . . . . . . . . . . . . . . . . . . . . . . . 3 66 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 67 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 68 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 69 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 70 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 71 7.2. Informative References . . . . . . . . . . . . . . . . . 6 72 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 74 1. Terminologies 76 Familiarity with BIER/MVPN/EVPN protocols and procedures is assumed. 77 Some terminologies are listed below for convenience. 79 [To be added]. 81 2. Introduction 83 The BIER architecture includes three layers: the "routing underlay", 84 the "BIER layer", and the "multicast flow overlay". The multicast 85 flow overlay is responsible for the BFERs to signal to BFIRs that 86 they are interested in receiving certain multicast flows so that 87 BFIRs can encode the correct bitstring for BIER forwarding by the 88 BIER layer. 90 MVPN and EVPN are two similar overlays where BGP Auto-Discovery 91 routes for MVPN/EVPN are exchanged among all PEs to signal which PEs 92 need to receive multicast traffic for all or certain flows. 94 Typically the same provider tunnel type is used for traffic to reach 95 all receiving PEs. 97 Consider an MVPN/EVPN deployment where enough P/PE routers are BIER 98 capable for BIER to become the preferred the choice of provider 99 tunnel. However, some PEs cannot be upgraded to support BIER 100 forwarding. While there are ways to allow an ingress PE to send 101 traffic to some PEs with one type of tunnel and send traffic to some 102 other PEs with a different type of tunnel, the procedure becomes 103 complicated and forwarding is not optimized. 105 One way to solve this problem is to use Penultimate Hop Popping (PHP) 106 so that the upstream BFR can pop the BIER header and send the payload 107 "natively" (note that the upstream BFR can be connected directly or 108 indiretly via a tunnel to the PE). This is similar to MPLS PHP 109 though it is the BIER header that is popped. In case of MPLS 110 encapsulation, even the signaling is similar - a BIER incapable 111 router signals as if it supported BIER, but to request PHP at the 112 penultimate hop, it signals an Implicit Null label instead of a 113 regular BIER label as the Label Range Base in its BIER MPLS 114 Encapsulation sub-TLV. 116 In order for the PE to be able to correctly forward the packets 117 resulting from the PHP, certain conditions must be met, as specified 118 in Section 3. 120 While the above text uses MVPN/EVPN as example, BIER PHP is 121 applicable to any scenario where the multicast flow overlay edge 122 router does not support BIER. 124 This works well if a BIER incapable PE only needs to receive 125 multicast traffic. If it needs to send multicast traffic as well, 126 then it must Ingress Replicate to a BIER capable helper PE, who will 127 in turn relay the packet to other PEs. The helper PE is either a 128 Virtual Hub as specified in [RFC7024] for MVPN and [I-D.keyupate- 129 bess-evpn-virtual-hub] for EVPN, or an AR-Replicator as specified in 130 [I-D.ietf-bess-evpn-optimized-ir] for EVPN. 132 3. Specifications 134 The procedures in this section can be applied only if, by means 135 outside the scope of this document, it is known that one of the 136 following conditions is met. 138 o The payload after BIER header is IPv4 or IPv6 (i.e., the Proto 139 field in the BIER header is 4 or 6). 141 Notice that in this case the Destination Address in the IPv4/IPv6 142 header must be in the address space for the BIER layer. 144 o The payload after BIER header is MPLS packet with downstream- 145 assigned label at top of stack (i.e., the Proto field in the BIER 146 header is 1). For example, a label from a Domain-wide Common 147 Block (DCB) is used as specified in [I-D.zzhang-bess-mvpn-evpn- 148 aggregation-label]. 150 A BIER incapable router, if acting as a multicast flow overlay 151 router, MUST signal its BIER information as specified in [RFC8401] or 152 [I-D.ietf-bier-ospf-bier-extensions] or [I-D.ietf-bier-idr- 153 extensions], with a PHP sub-sub-TLV included in the BIER sub-TLV 154 attached to the BIER incapable router's BIER prefix to request BIER 155 PHP from other BFRs. The sub-sub-TLV's type is TBD, and the length 156 is 0. 158 With MPLS encapsulation, the BIER incapable multicast flow overlay 159 router MAY omit the BIER MPLS Encapsulation sub-sub-TLV, or MUST set 160 the Label Range Base in BIER MPLS Encapsulation sub-sub-TLV to 161 Implicit Null Label [RFC3032]. 163 With MPLS encapsulation, if a BFER does not support certain BSL, it 164 MAY still advertise a corresponding BIER MPLS Encapsulation sub-TLV 165 but set the Label Range Base to Implicit Null Label. 167 If a BFR follows section 6.9 of [RFC8279] to handle BIER incapable 168 routers, it must treat a router as BIER incapable if the Label Range 169 Base dvertised by the router is Implicit Null, or if the router 170 advertises a PHP sub-sub-TLV, so that the router is not used as a 171 transit BFR. 173 If the downstream neighbor for a BIER prefix is the one advertising 174 the prefix with a PHP sub-sub-TLV or with an Implicit Null Label as 175 the Label Range Base in its BIER MPLS Encapsulation sub-sub-TLV, then 176 when the corresponding BIRT or BIFT entry is created/updated, the 177 forwarding behavior MUST be that the BIER header is removed and the 178 payload be sent to the downstream router without the BIER header, 179 either directly or over a tunnel. 181 4. Security Considerations 183 This specification does not introduce additional security concerns 184 beyond those already discussed in BIER architecture and OSPF/ISIS/BGP 185 exentions for BIER signaling. 187 5. IANA Considerations 189 This document requests a new sub-sub-TLV type value from the "Sub- 190 sub-TLVs for BIER Info Sub-TLV" registry in the "IS-IS TLV 191 Codepoints" registry: 193 Type Name 194 ---- ---- 195 TBD BIER PHP Request 197 This document also requests a new sub-TLV type value from the OSPFv2 198 Extended Prefix TLV Sub-TLV registry: 200 Type Name 201 ---- ---- 202 TBD BIER PHP Request 204 6. Acknowledgements 206 The author wants to thank Eric Rosen and Antonie Przygienda for their 207 review, comments and suggestions. The author also wants to thank 208 Senthil Dhanaraj for his suggestion of requesting PHP if a BFER does 209 not support certain BSL. 211 7. References 213 7.1. Normative References 215 [I-D.ietf-bess-evpn-optimized-ir] 216 Rabadan, J., Sathappan, S., Henderickx, W., Sajassi, A., 217 Isaac, A., and M. Katiyar, "Optimized Ingress Replication 218 solution for EVPN", draft-ietf-bess-evpn-optimized-ir-03 219 (work in progress), February 2018. 221 [I-D.ietf-bier-idr-extensions] 222 Xu, X., Chen, M., Patel, K., Wijnands, I., and T. 223 Przygienda, "BGP Extensions for BIER", draft-ietf-bier- 224 idr-extensions-05 (work in progress), March 2018. 226 [I-D.ietf-bier-ospf-bier-extensions] 227 Psenak, P., Kumar, N., Wijnands, I., Dolganow, A., 228 Przygienda, T., Zhang, Z., and S. Aldrin, "OSPFv2 229 Extensions for BIER", draft-ietf-bier-ospf-bier- 230 extensions-18 (work in progress), June 2018. 232 [I-D.keyupate-bess-evpn-virtual-hub] 233 Patel, K., Sajassi, A., Drake, J., Zhang, Z., and W. 234 Henderickx, "Virtual Hub-and-Spoke in BGP EVPNs", draft- 235 keyupate-bess-evpn-virtual-hub-00 (work in progress), 236 March 2017. 238 [I-D.zzhang-bess-mvpn-evpn-aggregation-label] 239 Zhang, Z., Rosen, E., Lin, W., Li, Z., and I. Wijnands, 240 "MVPN/EVPN Tunnel Aggregation with Common Labels", draft- 241 zzhang-bess-mvpn-evpn-aggregation-label-01 (work in 242 progress), April 2018. 244 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 245 Requirement Levels", BCP 14, RFC 2119, 246 DOI 10.17487/RFC2119, March 1997, 247 . 249 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 250 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 251 Explicit Replication (BIER)", RFC 8279, 252 DOI 10.17487/RFC8279, November 2017, 253 . 255 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 256 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 257 for Bit Index Explicit Replication (BIER) in MPLS and Non- 258 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 259 2018, . 261 [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. 262 Zhang, "Bit Index Explicit Replication (BIER) Support via 263 IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, 264 . 266 7.2. Informative References 268 [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ 269 BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 270 2012, . 272 [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP 273 Encodings and Procedures for Multicast in MPLS/BGP IP 274 VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, 275 . 277 [RFC7024] Jeng, H., Uttaro, J., Jalil, L., Decraene, B., Rekhter, 278 Y., and R. Aggarwal, "Virtual Hub-and-Spoke in BGP/MPLS 279 VPNs", RFC 7024, DOI 10.17487/RFC7024, October 2013, 280 . 282 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 283 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based 284 Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 285 2015, . 287 Author's Address 289 Zhaohui Zhang 290 Juniper Networks 292 EMail: zzhang@juniper.net