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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 A. Przygienda 4 Intended status: Standards Track Juniper Networks 5 Expires: October 12, 2018 A. Dolganow 6 H. Bidgoli 7 Nokia 8 I. Wijnands 9 Cisco Systems 10 A. Gulko 11 Thomson Reuters 12 April 10, 2018 14 BIER Underlay Path Calculation Algorithm and Contraints 15 draft-ietf-bier-bar-ipa-01 17 Abstract 19 This document specifies general rules for interaction between the BAR 20 and IPA fields defined in [I-D.ietf-bier-isis-extensions] and 21 [I-D.ietf-bier-ospf-bier-extensions]. 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 October 12, 2018. 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. General Rules for the BAR and IPA fields . . . . . . . . . . 3 66 3.1. When BAR Is Not Used . . . . . . . . . . . . . . . . . . 4 67 3.2. Exceptions/Extensions to the General Rules . . . . . . . 4 68 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 69 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 70 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 71 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 72 6.2. Informative References . . . . . . . . . . . . . . . . . 5 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 75 1. Terminologies 77 Familiarity with BIER protocols and procedures is assumed. Some 78 terminologies are listed below for convenience. 80 [To be added]. 82 2. Introduction 84 In the BIER architecture, packets with a BIER encapsulation header 85 are forwarded to the neighbors on the underlay paths towards the 86 BFERs. For each sub-domain, the paths are calculated in the underlay 87 topology for the sub-domain, following a calculation algorithm 88 specific to the sub-domain. The could be 89 congruent or incongruent with unicast. The topology could be a 90 default topology, a multi-topology [RFC5120] topology. The algorithm 91 could be a generic IGP algorithm (e.g. SPF) or could be a BIER 92 specific one defined in the future. 94 In [I-D.ietf-bier-isis-extensions] and 95 [I-D.ietf-bier-ospf-bier-extensions], an 8-bit BAR field and 8-bit 96 IPA field are defined to signal the BIER specific algorithm and 97 generic IGP Algorithm respectively and only value 0 is allowed for 98 both fields currently. This document specifies the general rules for 99 the two fields and their interaction when either or both fields are 100 not 0. 102 3. General Rules for the BAR and IPA fields 104 For a particular sub-domain, all routers SHOULD be provisioned with 105 and signal the same BAR and IPA values. When a BFR discovers another 106 BFR advertising different BAR or IPA value from its own provisioned, 107 it MUST treat the advertising BFR as incapable of supporting BIER for 108 the sub-domain. How incapable routers are handled is outside the 109 scope of this document. 111 It is expected that both the BAR and IPA values could have both 112 algorithm and constraints semantics. To generalize, we introduce the 113 following terms: 115 o BC: BIER-specific Constraints 117 o BA: BIER-specific Algorithm 119 o RC: Generic Routing Constraints 121 o RA: Generic Routing Algorithm 123 o BCBA: BC + BA 125 o RCRA: RC + RA 127 A BAR value corresponds to a BCBA, and a IPA value corresponds to a 128 RCRA. Any of the RC/BC/BA could be "NULL", which means there are no 129 corresponding constraints or algorithm. 131 For a particular topology X (which could be a default topology or 132 multit-topolgy topology) that a sub-domain is associated with, a 133 router calculates the underlay paths according to its provisioned 134 BCBA and RCRA the following way: 136 1. Apply the BIER constraints, resulting in BC(X). 138 2. Apply the routing constraints, resulting in RC(BC(X)). 140 3. Select the algorithm AG as following: 142 A. If BA is NULL, AG is set to RA. 144 B. If BA is not NULL, AG is set to BA. 146 4. Run AG on RC(BC(X)). 148 3.1. When BAR Is Not Used 150 The BIER Algorithm registry established by 151 [I-D.ietf-bier-isis-extensions] and also used in 152 [I-D.ietf-bier-ospf-bier-extensions] has value 0 for "No BIER 153 specific algorithm is used". That translates to NULL BA and NULL BC. 154 Following the rules defined above, the IPA value alone identifies the 155 calculation algorithm and constraints to be used for a particular 156 sub-domain when BAR is 0. 158 3.2. Exceptions/Extensions to the General Rules 160 Exceptions or extensions to the above general rules may be specified 161 in the future for specific BAR and/or IPA values. When that happens, 162 compatibility with defined BAR and/or IPA values and semantics need 163 to be specified. 165 4. IANA Considerations 167 No IANA Consideration is requested in this document. 169 5. Acknowledgements 171 The authors thanks Alia Atlas, Eric Rosen, Senthil Dhanaraj and many 172 others for their suggestions and comments. In particular, the BCBA/ 173 RCRA representation for the interaction rules is based on Alia's 174 write-up. 176 6. References 178 6.1. Normative References 180 [I-D.ietf-bier-isis-extensions] 181 Ginsberg, L., Przygienda, T., Aldrin, S., and Z. Zhang, 182 "BIER support via ISIS", draft-ietf-bier-isis- 183 extensions-11 (work in progress), March 2018. 185 [I-D.ietf-bier-ospf-bier-extensions] 186 Psenak, P., Kumar, N., Wijnands, I., Dolganow, A., 187 Przygienda, T., Zhang, Z., and S. Aldrin, "OSPFv2 188 Extensions for BIER", draft-ietf-bier-ospf-bier- 189 extensions-17 (work in progress), April 2018. 191 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 192 Requirement Levels", BCP 14, RFC 2119, 193 DOI 10.17487/RFC2119, March 1997, 194 . 196 [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 197 Przygienda, T., and S. Aldrin, "Multicast Using Bit Index 198 Explicit Replication (BIER)", RFC 8279, 199 DOI 10.17487/RFC8279, November 2017, 200 . 202 6.2. Informative References 204 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 205 Topology (MT) Routing in Intermediate System to 206 Intermediate Systems (IS-ISs)", RFC 5120, 207 DOI 10.17487/RFC5120, February 2008, 208 . 210 Authors' Addresses 212 Zhaohui Zhang 213 Juniper Networks 215 EMail: zzhang@juniper.net 217 Antoni Przygienda 218 Juniper Networks 220 EMail: prz@juniper.net 222 Andrew Dolganow 223 Nokia 225 EMail: andrew.dolganow@nokia.com 227 Hooman Bidgoli 228 Nokia 230 EMail: hooman.bidgoli@nokia.com 231 IJsbrand Wijnands 232 Cisco Systems 234 EMail: ice@cisco.com 236 Arkadiy Gulko 237 Thomson Reuters 239 EMail: arkadiy.gulko@thomsonreuters.com