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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 Cisco Systems 4 Intended status: Informational X. Xu 5 Expires: April 21, 2019 Alibaba Group 6 H. Bidgoli 7 Nokia 8 October 18, 2018 10 An Optional Encoding of the BIFT-id Field in the non-MPLS BIER 11 Encapsulation 12 draft-ietf-bier-non-mpls-bift-encoding-01 14 Abstract 16 Bit Index Explicit Replication (BIER) is an architecture that 17 provides optimal multicast forwarding through a "multicast domain", 18 without requiring intermediate routers to maintain any per-flow state 19 or to engage in an explicit tree-building protocol. The Multicast 20 packet is encapsulated using a BIER Header and transported through an 21 MPLS or non-MPLS network. When MPLS is used as the transport, the 22 Bit Indexed Forwarding Table (BIFT) is identified by a MPLS Label. 23 When non-MPLS transport is used, the BIFT is identified by a 20bit 24 value. This document describes one way of encoding the 20bit value. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at https://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on April 21, 2019. 43 Copyright Notice 45 Copyright (c) 2018 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (https://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 2. Terminology and Definitions . . . . . . . . . . . . . . . . . 3 62 3. Specification of Requirements . . . . . . . . . . . . . . . . 3 63 4. The Bit Index Forwarding Table . . . . . . . . . . . . . . . 3 64 5. The Non-MPLS Static BSL-SD-SI BIFT Encoding . . . . . . . . . 4 65 6. The Non-MPLS Static IBU-SI BIFT Encoding . . . . . . . . . . 4 66 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 67 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 68 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 69 10. Normative References . . . . . . . . . . . . . . . . . . . . 5 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 72 1. Introduction 74 Bit Index Explicit Replication (BIER) [RFC8279] is an architecture 75 that provides optimal multicast forwarding through a "multicast 76 domain", without requiring intermediate routers to maintain any per- 77 flow state or to engage in an explicit tree-building protocol. The 78 Multicast packet is encapsulated [RFC8296] using a BIER Header and 79 transported through an MPLS or non-MPLS network. When MPLS is used 80 as the transport, the Bit Indexed Forwarding Table (BIFT) is 81 identified by a MPLS Label. When non-MPLS transport is used, the 82 BIFT is identified by a 20bit value. This document describes one way 83 of encoding the 20bit value, based on the Sub-Domain (SD), Set 84 Identifier (SI) and BitStringLength (BSL) values. 86 The BIER architecture requires that a BFR has a BIFT for every 87 combination of that is being used. When processing a 88 BIER packet, the correct BIFT is inferred from the BIFT-id field of 89 the encapsulation. When the non-MPLS encapsulation is used in a 90 given BIER domain, it may be desirable for the a BIFT-id to be unique 91 in that domain. This document describes an OPTIONAL method that can 92 be used to form domain-wide unique BIFT-ids based on the triples. If in the future the BIER architecture is extended 94 with an additional BIFT argument, this encoding does not generate 95 domain-wide unique identifiers anymore. 97 This encoding, if used, is only for the convenience of the network 98 adminstrators. When forwarding a BIER packet, the BIFT-id is used as 99 an opaque 20-bit value that identifies a BIFT; the forwarding 100 procedures do not parse the 20-bit value, they just use it as a 101 lookup key. 103 2. Terminology and Definitions 105 Readers of this document are assumed to be familiar with the 106 terminology and concepts of the documents listed as Normative 107 References. For convenience, some of the more frequently used terms 108 appear below. 110 BIER: 111 Bit Indexed Explicit Replication. 113 BIFT-id: 114 Bit Indexed Forwarding Table Identifier. 116 3. Specification of Requirements 118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 120 document are to be interpreted as described in [RFC2119]. 122 4. The Bit Index Forwarding Table 124 In MPLS networks a BIER label is allocated for each Bit Index 125 Forwarding Table (BIFT) from the platform specific, downstream label 126 database ([RFC8296]). This label is associated with a particular 127 combination of BIER Sub-Domain (SD), Set Identifier (SI) and 128 BitStringLength (BSL). In order for the network to know which MPLS 129 label represents a particular combination of , this 130 mapping has to be advertised through the network. This is currently 131 done through an IGP or BGP. In MPLS networks this is not a drawback 132 as the MPLS label has to be advertised anyway. 134 When the non-MPLS encoding is chosen, there is no need to advertise 135 the BIFT-id to mapping if the BIFT-id is domain-wide 136 unique. For this reason we're defining two encodings that MAY be 137 used by operators to compute the domain-wide unique BIFT-id values 138 from the SD, BSL and/or SI. Although the BIFT-id is not expected to 139 change, it may change when the BSL mismatch procedures [RFC8279] 140 section 6.10.2 are applied. 142 5. The Non-MPLS Static BSL-SD-SI BIFT Encoding 144 Find below the first 32 bits of the BIER header, encoding the SD, SI 145 and BSL into the 20 bit BIFT-id field. 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | BSL | SD | SI | TC |S| TTL | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 |-------- 20 bit BIFT-id Field ---------| 153 Figure 1 155 BSL: This 4-bit field encodes the length in bits of the BitString. 156 These are the same values as documented in [RFC8296]. 158 SD: This is a 8-bit field that encodes the Sub-Domain as described 159 in [RFC8279]. 161 SI: This is a 8-bit field that encodes the Set-ID as described in 162 [RFC8279]. 164 TC: This is a 3-bit field set to 000 (following [RFC8296]). 166 S: This is a 1-bit field set to 1 (following [RFC8296]). 168 TTL: See [RFC8296]. 170 6. The Non-MPLS Static IBU-SI BIFT Encoding 172 Find below the first 32 bits of the BIER header, encoding the 173 provisioned Index BIFT Unit (IBU) and SI into the 20 bit BIFT-id 174 field. The IBU replaces the BSL and SD values as described in the 175 encoding above. This provides additional flexibility in-case there 176 is a need to support additional arguments other than BSL and SD to 177 create the BIFT-id. 179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 180 | IBU | SI | TC |S| TTL | 181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 183 |-------- 20 bit BIFT-id Field ---------| 185 Figure 2 187 IBU: The IBU is a 12-bit field that encodes the provisioned Index 188 BIFT Unit. 190 SI: This is a 8-bit field that encodes the Set-ID as described in 191 [RFC8279]. 193 TC: This is a 3-bit field set to 000 (following [RFC8296]). 195 S: This is a 1-bit field set to 1 (following [RFC8296]). 197 TTL: See [RFC8296]. 199 7. Security Considerations 201 This document does not introduce any new security considerations 202 other than already discussed in [RFC8279]. 204 8. IANA Considerations 206 There is no IANA consideration. 208 9. Acknowledgments 210 The authors like to thank the following people for their comments and 211 contributions to this document; Eric Rosen, Neale Ranns, Jeffrey 212 Zhang. 214 10. Normative References 216 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 217 Requirement Levels", BCP 14, RFC 2119, 218 DOI 10.17487/RFC2119, March 1997, 219 . 221 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 222 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 223 Explicit Replication (BIER)", RFC 8279, 224 DOI 10.17487/RFC8279, November 2017, 225 . 227 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 228 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 229 for Bit Index Explicit Replication (BIER) in MPLS and Non- 230 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 231 2018, . 233 Authors' Addresses 235 IJsbrand Wijnands 236 Cisco Systems 237 De Kleetlaan 6a 238 Diegem 1831 239 Belgium 241 Email: ice@cisco.com 243 Xiaohu Xu 244 Alibaba Group 246 Email: xiaohu.xxh@alibaba-inc.com 248 Hooman Bidgoli 249 Nokia 250 600 March Rd. 251 Ottawa, Ontario K2K 2E6 252 Canada 254 Email: hooman.bidgoli@nokia.com