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Mishra 5 Expires: May 7, 2020 Cisco 6 November 4, 2019 8 Flex Algorithm for BIER 9 draft-nainar-bier-flex-algo-00 11 Abstract 13 Bit Index Explicit Replication (BIER) is an architecture that 14 provides optimal multicast forwarding through a "BIER domain" without 15 requiring intermediate routers to run explicit tree-building protocol 16 or to maintain multicast-related, per-flow state. IGP protocols are 17 extended to carry BFR-Id and other encapsulation informations that 18 are used by traditional path computing algorithm using link metric 19 for a loop-free best path selection. 21 This document defines a constrained based path selection using IGP 22 flexible Algorithm for BIER. 24 Requirements Language 26 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 27 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 28 "OPTIONAL" in this document are to be interpreted as described in RFC 29 2119 [RFC2119] RFC 8174 [RFC8174] when and only when, they appear in 30 all capitals, as shown here. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at https://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on May 7, 2020. 49 Copyright Notice 51 Copyright (c) 2019 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (https://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 67 1.1. Acronyms and Terminology . . . . . . . . . . . . . . . . 3 68 1.1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . 3 69 1.1.2. Terminology . . . . . . . . . . . . . . . . . . . . . 3 70 2. Flexible Algorithm . . . . . . . . . . . . . . . . . . . . . 3 71 3. Constraint Forwarding Identifier . . . . . . . . . . . . . . 4 72 3.1. BFR ID Mapping for Flexible Algorithm . . . . . . . . . . 4 73 3.2. BIER-MPLS Label Mapping for Flexiblem Algorithm . . . . . 5 74 4. IGP Extensions Flexible Algorithm . . . . . . . . . . . . . . 6 75 4.1. ISIS . . . . . . . . . . . . . . . . . . . . . . . . . . 6 76 4.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 6 77 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 78 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 80 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 81 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 82 8.2. Informative References . . . . . . . . . . . . . . . . . 7 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 85 1. Introduction 87 [RFC8279] defines Bit Index Explicit Replication (BIER), an 88 architecture that provides optimal multicast forwarding through a 89 "BIER domain" without requiring intermediate routers to run explicit 90 tree-building protocol or to maintain multicast-related, per-flow 91 state. [RFC8401] and [RFC8444] defines the IGP protocols extensions 92 to carry BFR-Id and other encapsulation informations that are used by 93 traditional path computing algorithm using link metric for a loop- 94 free best path selection. 96 The ability to compute constrained path using attributes beyond the 97 basic link metric and steering the multicast traffic over such 98 constrained path brings a lot of benefits such as efficient load 99 distribution, path dis-jointness and resiliency. Bandwidth-aware, 100 delay-sensitive or multi-planar are some of the examples for such 101 constrained path selection. The path computation and traffic 102 steering over flexible algorithm based constrained path requires 103 advertising a set of Path constraints associated to each link and a 104 unique dataplane based identifier to differentiate the data packets 105 that needs to be steered over such computed constrained paths. 107 This document specifies the IGP protocol extensions and the mechanism 108 to implement IGP Flexible Algorithm for BIER network. 110 1.1. Acronyms and Terminology 112 1.1.1. Acronyms 114 TBD 116 1.1.2. Terminology 118 This document uses the terminologies defined in [RFC8279], [RFC8296], 119 and so the readers are expected to be familiar with the same. 121 2. Flexible Algorithm 123 Different types of contraints may be used to compute a path over the 124 BIER network. Link performance and multi-plane are some of the 125 common examples for such constraints. An example multiplane BIER 126 network is shown in below figure 1. 128 +---(gBFR1)--------------(gBFR2) 129 / + + 130 / | \ | \ 131 / | \ | \ 132 (BFIR) | (gBFR3)------------~(gBFR4)------+ 133 \ | + | + \ 134 \ | | | | \ 135 \ + | | | \ 136 +----(rBFR1)--------------(rBFR2) | (BFER) 137 + | + | / 138 \ | \ | / 139 \ | \ | / 140 + + / 141 (rBFR3)---------------(rBFR4)---+ 143 Figure 1. MultiPlane BIER Network 145 The above BIER network is enabled with "green" and "red" planes by 146 assigning a contiguous set of BFRs to each plane. For example, 147 gBFR1, gBFR2, gBFR3 and gBFR4 belongs to "green" plane while rBFR1, 148 rBFR2, rBFR3 and rBFR$ belong sto "red" plane. BFIR and BFER are 149 enabled with both the planes. 151 Any BFR must have a mechanism to identify the set of constraints 152 associated to each algorithm so that a loop free path can be 153 computed. Any BFR must have a mechanism to map the data packet to 154 the associated constrained path for loop free constrained forwarding. 156 3. Constraint Forwarding Identifier 158 This section explains different mechanism for identifying the 159 constraints forwarding in the BIER encapsulated data packet. 161 3.1. BFR ID Mapping for Flexible Algorithm 163 For each Flexible Algorithm, a domain wide unique BFR-ID will be 164 assigned with BFR-Prefix for each participating BFER within the BIER 165 domain. 167 +---(gBFR1)--------------(gBFR2) 168 / + + 169 / | \ | \ 170 / | \ | \ 171 (BFIR) | (gBFR3)------------~(gBFR4)------+ 172 \ | + | + \ 173 \ | | | | \ 174 \ + | | | \ 175 +----(rBFR1)--------------(rBFR2) | (BFER) (0001 = red) 176 + | + | / (0010 = green) 177 \ | \ | / 178 \ | \ | / 179 + + / 180 (rBFR3)---------------(rBFR4)---+ 181 Figure 2. BFR-ID Mapping 183 Each BFER is assigned with domain wide unique BFR-ID for each 184 Flexible Algorithm. In Figure 2, BFER assigns 0001 for "red" plane 185 while using 0010 for "green" plane. Any BFR participating in one 186 plane may not have the BFR-ID associated with other planes. 188 BFIR pushes the relevant BFR-ID to enforce the forwarding over any 189 specific contraint path which can be influenced by a local policy. 191 3.2. BIER-MPLS Label Mapping for Flexiblem Algorithm 193 For each Flexible Algorithm, a locally unique BIER-MPLS label is 194 assigned by each participating BFR within the BIER domain. In this 195 option, each BFER is assigned with just one BFR-ID as mentioned in 196 [RFC8279]. 198 +---(gBFR1)--------------(gBFR2) 199 / + + 200 / | \ | \ 201 / | \ | \ 202 (BFIR) | (gBFR3)------------~(gBFR4)------+ 203 \ | + | + \ 204 \ | | | | \ 205 \ + | | | \ (BFR-ID = 0001) 206 +----(rBFR1)--------------(rBFR2) | (BFER) (L1 = red) 207 + | + | / (L2 = green) 208 \ | \ | / 209 \ | \ | / 210 + + / 211 (rBFR3)---------------(rBFR4)---+ 213 Figure 3. BIER-MPLS Label Mapping 215 Each BFR is assigned with locally unique BIER-MPLS for each Flexible 216 Algorithm. The BIER-MPLS label along with the relevant constraints 217 are advertised to other BFR using extensions defined in section x. 218 In Figure 3, BFER is assigned with BFR-ID of 1 and advertise BIER- 219 MPLS label L1 for "red" plane and L2 for "green" plane. 221 BFIR pushes the relevant BIER-MPLS advertised by the nexthop. Any 222 BFR participating in both the plane will have the forwarding 223 instruction for both the planes populated in different BIFT. The 224 incoming BIER-MPLS label is used to identify the plane and the BIFT 225 to perform the lookup and forwarding. 227 Additional details about non-MPLS BIER encapsulation will be included 228 in later revisions. 230 4. IGP Extensions Flexible Algorithm 232 This section defines the IGP protocol extensions for BIER Flexible 233 Algorithm. 235 4.1. ISIS 237 4.2. OSPF 239 5. Security Considerations 241 To be Updated. 243 6. IANA Considerations 245 TBD. 247 7. Acknowledgements 249 To be Updated. 251 8. References 253 8.1. Normative References 255 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 256 Requirement Levels", BCP 14, RFC 2119, 257 DOI 10.17487/RFC2119, March 1997, 258 . 260 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 261 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 262 May 2017, . 264 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 265 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 266 Explicit Replication (BIER)", RFC 8279, 267 DOI 10.17487/RFC8279, November 2017, 268 . 270 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 271 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 272 for Bit Index Explicit Replication (BIER) in MPLS and Non- 273 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 274 2018, . 276 [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. 277 Zhang, "Bit Index Explicit Replication (BIER) Support via 278 IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, 279 . 281 [RFC8444] Psenak, P., Ed., Kumar, N., Wijnands, IJ., Dolganow, A., 282 Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2 283 Extensions for Bit Index Explicit Replication (BIER)", 284 RFC 8444, DOI 10.17487/RFC8444, November 2018, 285 . 287 [RFC8459] Dolson, D., Homma, S., Lopez, D., and M. Boucadair, 288 "Hierarchical Service Function Chaining (hSFC)", RFC 8459, 289 DOI 10.17487/RFC8459, September 2018, 290 . 292 8.2. Informative References 294 [I-D.ietf-lsr-flex-algo] 295 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 296 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 297 algo-04 (work in progress), September 2019. 299 Authors' Addresses 301 Nagendra Kumar 302 Cisco Systems, Inc. 304 Email: naikumar@cisco.com 306 Ijsbrand Wijnands 307 Cisco Systems, Inc. 309 Email: iwijnand@cisco.com 310 Mankamana Mishra 311 Cisco Systems, Inc. 313 Email: mankamis@cisco.com