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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BIER Working Group IJ. Wijnands 3 Internet-Draft Individual 4 Intended status: Informational M. Mishra 5 Expires: May 30, 2021 Cisco Systems 6 X. Xu 7 Alibaba Group 8 H. Bidgoli 9 Nokia 10 November 26, 2020 12 An Optional Encoding of the BIFT-id Field in the non-MPLS BIER 13 Encapsulation 14 draft-ietf-bier-non-mpls-bift-encoding-03 16 Abstract 18 Bit Index Explicit Replication (BIER) is an architecture that 19 provides optimal multicast forwarding through a "multicast domain", 20 without requiring intermediate routers to maintain any per-flow state 21 or to engage in an explicit tree-building protocol. The Multicast 22 packet is encapsulated using a BIER Header and transported through an 23 MPLS or non-MPLS network. When MPLS is used as the transport, the 24 Bit Indexed Forwarding Table (BIFT) is identified by a MPLS Label. 25 When non-MPLS transport is used, the BIFT is identified by a 20bit 26 value. This document describes one way of encoding the 20bit value. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on May 30, 2021. 45 Copyright Notice 47 Copyright (c) 2020 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 2. Terminology and Definitions . . . . . . . . . . . . . . . . . 3 64 3. Specification of Requirements . . . . . . . . . . . . . . . . 3 65 4. The Bit Index Forwarding Table . . . . . . . . . . . . . . . 3 66 5. The Non-MPLS Static BSL-SD-SI BIFT Encoding . . . . . . . . . 4 67 6. The Non-MPLS Static IBU-SI BIFT Encoding . . . . . . . . . . 4 68 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 69 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 70 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 71 10. Normative References . . . . . . . . . . . . . . . . . . . . 5 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 74 1. Introduction 76 Bit Index Explicit Replication (BIER) [RFC8279] is an architecture 77 that provides optimal multicast forwarding through a "multicast 78 domain", without requiring intermediate routers to maintain any per- 79 flow state or to engage in an explicit tree-building protocol. The 80 Multicast packet is encapsulated [RFC8296] using a BIER Header and 81 transported through an MPLS or non-MPLS network. When MPLS is used 82 as the transport, the Bit Indexed Forwarding Table (BIFT) is 83 identified by a MPLS Label. When non-MPLS transport is used, the 84 BIFT is identified by a 20bit value. This document describes one way 85 of encoding the 20bit value, based on the Sub-Domain (SD), Set 86 Identifier (SI) and BitStringLength (BSL) values. 88 The BIER architecture requires that a BFR has a BIFT for every 89 combination of that is being used. When processing a 90 BIER packet, the correct BIFT is inferred from the BIFT-id field of 91 the encapsulation. When the non-MPLS encapsulation is used in a 92 given BIER domain, it may be desirable for the a BIFT-id to be unique 93 in that domain. This document describes an OPTIONAL method that can 94 be used to form domain-wide unique BIFT-ids based on the triples. If in the future the BIER architecture is extended 96 with an additional BIFT argument, this encoding does not generate 97 domain-wide unique identifiers anymore. 99 This encoding, if used, is only for the convenience of the network 100 adminstrators. When forwarding a BIER packet, the BIFT-id is used as 101 an opaque 20-bit value that identifies a BIFT; the forwarding 102 procedures do not parse the 20-bit value, they just use it as a 103 lookup key. 105 2. Terminology and Definitions 107 Readers of this document are assumed to be familiar with the 108 terminology and concepts of the documents listed as Normative 109 References. For convenience, some of the more frequently used terms 110 appear below. 112 BIER: 113 Bit Indexed Explicit Replication. 115 BIFT-id: 116 Bit Indexed Forwarding Table Identifier. 118 3. Specification of Requirements 120 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 121 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 122 document are to be interpreted as described in [RFC2119]. 124 4. The Bit Index Forwarding Table 126 In MPLS networks a BIER label is allocated for each Bit Index 127 Forwarding Table (BIFT) from the platform specific, downstream label 128 database ([RFC8296]). This label is associated with a particular 129 combination of BIER Sub-Domain (SD), Set Identifier (SI) and 130 BitStringLength (BSL). In order for the network to know which MPLS 131 label represents a particular combination of , this 132 mapping has to be advertised through the network. This is currently 133 done through an IGP or BGP. In MPLS networks this is not a drawback 134 as the MPLS label has to be advertised anyway. 136 When the non-MPLS encoding is chosen, there is no need to advertise 137 the BIFT-id to mapping if the BIFT-id is domain-wide 138 unique. For this reason we're defining two encodings that MAY be 139 used by operators to compute the domain-wide unique BIFT-id values 140 from the SD, BSL and/or SI. Although the BIFT-id is not expected to 141 change, it may change when the BSL mismatch procedures [RFC8279] 142 section 6.10.2 are applied. 144 5. The Non-MPLS Static BSL-SD-SI BIFT Encoding 146 Find below the first 32 bits of the BIER header, encoding the SD, SI 147 and BSL into the 20 bit BIFT-id field. 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 | BSL | SD | SI | TC |S| TTL | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 |-------- 20 bit BIFT-id Field ---------| 155 Figure 1 157 BSL: This 4-bit field encodes the length in bits of the BitString. 158 These are the same values as documented in [RFC8296]. 160 SD: This is a 8-bit field that encodes the Sub-Domain as described 161 in [RFC8279]. 163 SI: This is a 8-bit field that encodes the Set-ID as described in 164 [RFC8279]. 166 TC: This is a 3-bit field set to 000 (following [RFC8296]). 168 S: This is a 1-bit field set to 1 (following [RFC8296]). 170 TTL: See [RFC8296]. 172 6. The Non-MPLS Static IBU-SI BIFT Encoding 174 Find below the first 32 bits of the BIER header, encoding the 175 provisioned Index BIFT Unit (IBU) and SI into the 20 bit BIFT-id 176 field. The IBU replaces the BSL and SD values as described in the 177 encoding above. This provides additional flexibility in-case there 178 is a need to support additional arguments other than BSL and SD to 179 create the BIFT-id. 181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 182 | IBU | SI | TC |S| TTL | 183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 |-------- 20 bit BIFT-id Field ---------| 187 Figure 2 189 IBU: The IBU is a 12-bit field that encodes the provisioned Index 190 BIFT Unit. 192 SI: This is a 8-bit field that encodes the Set-ID as described in 193 [RFC8279]. 195 TC: This is a 3-bit field set to 000 (following [RFC8296]). 197 S: This is a 1-bit field set to 1 (following [RFC8296]). 199 TTL: See [RFC8296]. 201 7. Security Considerations 203 This document does not introduce any new security considerations 204 other than already discussed in [RFC8279]. 206 8. IANA Considerations 208 There is no IANA consideration. 210 9. Acknowledgments 212 The authors like to thank the following people for their comments and 213 contributions to this document; Eric Rosen, Neale Ranns, Jeffrey 214 Zhang. 216 10. Normative References 218 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 219 Requirement Levels", BCP 14, RFC 2119, 220 DOI 10.17487/RFC2119, March 1997, 221 . 223 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 224 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 225 Explicit Replication (BIER)", RFC 8279, 226 DOI 10.17487/RFC8279, November 2017, 227 . 229 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 230 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 231 for Bit Index Explicit Replication (BIER) in MPLS and Non- 232 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 233 2018, . 235 Authors' Addresses 237 IJsbrand Wijnands 238 Individual 239 Belgium 241 Email: ice@braindump.be 243 Mankamana Mishra 244 Cisco Systems 245 821 alder drive 246 Milpitas , CA 247 USA 249 Email: mankamis@cisco.com 251 Xiaohu Xu 252 Alibaba Group 254 Email: xiaohu.xxh@alibaba-inc.com 256 Hooman Bidgoli 257 Nokia 258 600 March Rd. 259 Ottawa, Ontario K2K 2E6 260 Canada 262 Email: hooman.bidgoli@nokia.com