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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ISIS WG C. Wang 3 Internet-Draft Z. Zhang 4 Intended status: Standards Track ZTE Corporation 5 Expires: April 18, 2016 October 16, 2015 7 IS-IS Extension for BIER-Lite 8 draft-wang-isis-bier-lite-extension-00 10 Abstract 12 Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is 13 an architecture that provides optimal multicast forwarding through a 14 "BIER domain" without requiring intermediate routers to maintain any 15 multicast related per-flow state. BIER also does not require any 16 explicit tree-building protocol for its operation. Currently, the 17 data plane of BIER is apt to use BIER-MPLS encapsulation to transmit 18 multicast traffic. However, this document tries to propose a 19 solution named BIER-Lite about how to extend IS-IS protocol to 20 support BIER forwarding in non-MPLS underlay network instead of MPLS 21 underlay network. 23 Status of this Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on April 18, 2016. 40 Copyright Notice 42 Copyright (c) 2015 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Convention and Terminology . . . . . . . . . . . . . . . . . . 5 59 3. BIER-Lite Sub-TLV in IS-IS extension . . . . . . . . . . . . . 6 60 4. Flooding of BIER-Lite Information . . . . . . . . . . . . . . 8 61 5. Considerations on BIER-Lite . . . . . . . . . . . . . . . . . 9 62 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 63 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 64 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 65 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 66 8.2. Informative References . . . . . . . . . . . . . . . . . . 12 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 69 1. Introduction 71 Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is 72 an architecture that provides optimal multicast forwarding through a 73 "BIER domain" without requiring intermediate routers to maintain any 74 multicast related per-flow state. BIER also does not require any 75 explicit tree-building protocol for its operation. A multicast data 76 packet enters a BIER domain at a "Bit-Forwarding Ingress Router" 77 (BFIR), and leaves the BIER domain at one or more "Bit-Forwarding 78 Egress Routers" (BFERs). The BFIR router adds a BIER header to the 79 packet. The BIER header contains a bit-string in which each bit 80 represents exactly one BFER to forward the packet to. The set of 81 BFERs to which the multicast packet needs to be forwarded is 82 expressed by setting the bits that correspond to those routers in the 83 BIER header. 85 Currently, the data plane of BIER is defined in BIER-MPLS 86 encapsulation [I-D.ietf-bier-mpls-encapsulation] to transmit 87 multicast traffic in MPLS encapsulation. Admittedly, BIER-MPLS 88 introduces the advantages of MPLS forwarding. However, this requires 89 the underlay network is an MPLS network, and along the path, there 90 need label switching and label lookup. Additionally, every BFR 91 requires per-label forwarding table to assist BIER forwarding. 92 What!_s more, prior of that, IGP protocol or BGP protocol requires a 93 precise mechanism to generate these label information, after that, to 94 advertise these label information to form the per-label forwarding 95 table between the label and the bit index forwarding table(BIFT). 96 Sometimes, how to categorize this label information in differentiated 97 MPLS Encapsulation sub-sub-TLV is a difficult decision. And some 98 other times, after the label information advertisement, there may be 99 some redundant label information as well as some redundant label 100 forwarding table because each BFR advertises continuous labels for 101 different Set Identifiers for each combination of Sub-domain and 102 BitStringLength which may be redundant because traffic to some BFERs 103 may not transit this advertising node, especially when these BFERs 104 belonging to the same Set Identifier reside together geographically. 106 In fact, some multicast scenario may be not in MPLS network, or may 107 be in a relatively simple network. In other words, if BIER 108 forwarding uses IP forwarding instead of MPLS forwarding in these 109 kind of networks, it would be much easier to deploy BIER in current 110 deployment. Of course, if the BIER forwarding is compatible with 111 BIER-MPLS encapsulation forwarding, that would be much more 112 significant. 114 The following section tries to propose how to extend IS-IS protocol 115 to support BIER forwarding in non-MPLS underlay network instead of 116 MPLS underlay network. 118 And this document names this solution as BIER-Lite. 120 2. Convention and Terminology 122 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 123 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 124 document are to be interpreted as described in [RFC2119]. 126 The terms about BIER are defined in [I-D.ietf-bier-architecture]. 128 3. BIER-Lite Sub-TLV in IS-IS extension 130 Given that the BIER-Lite-specific information that a BFR needs to 131 advertise to other BFRs are associated with the BFR-Prefix and Multi- 132 Topology information, the TLVs 135,236[RFC5305][RFC5308] and TLVs 133 235,237 [RFC5120]are used to carry and flood BIER-Lite-specific 134 information. 136 Here, in order to implement the BIER forwarding in non-MPLS network 137 and simplify the BIER forwarding mentioned in 138 [I-D.ietf-bier-mpls-encapsulation] , a new BIER-Lite sub-TLV of the 139 Extended Reachability TLVs is defined to advertise BIER-Lite-specific 140 information, which is illustrated as follow in Figure 1. 142 Here, in order to implement the BIER forwarding in non-MPLS network 143 and simplify the BIER forwarding mentioned in 144 [I-D.ietf-bier-mpls-encapsulation] , a new BIER-Lite sub-TLV of the 145 Extended Reachability TLVs is defined to advertise BIER-Lite-specific 146 information, which is illustrated as follow in Figure 1. 148 0 1 2 3 149 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 | Type | Length | M | Resverd |BSL Identifier | 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 153 | Reserved | subdomain-id | BFR-id | 154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 Figure 1: BIER-Lite Sub-TLV in IS-IS extension 158 Type: indicates BIER-Lite sub-TLV 160 Length: 6 octet. 162 M: indicating whether is compatible with BIER MPLS Encapsulation 163 sub-sub-TLV. When M is set to 1, it means if there has BIER MPLS 164 Encapsulation sub-sub-TLV, validating and using the BSL information 165 and label information in BIER MPLS Encapsulation sub-sub-TLV. When M 166 is set to 0, it means validating and using the BSL information in the 167 BSL Identifier even if there has BIER MPLS Encapsulation sub-sub-TLV 168 and ignoring all the information in BIER MPLS Encapsulation sub-sub- 169 TLV. 171 BSL Identifier: indicating the BSL the sending BFR supporting. 173 Sub-domain-ID: unique value identifying the BIER sub-domain within 175 the BIER domain, as described in section 1 of 176 [I-D.ietf-bier-architecture]. 178 BFR-id: a 2 octet field encoding the BFR-id, as documented in 179 section 2 [I-D.ietf-bier-architecture]. If the BFR-id is zero, it 180 means, the advertising router is not advertising any BFR-id. 182 The sending BFR may support one or several BSLs, as following: 184 00000001: represents BSL 64 bits; 186 00000010: represents BSL 128 bits; 188 00000100: represents BSL 256 bits; 190 00001000: represents BSL 512 bits; 192 00010000: represents BSL 1024 bits; 194 00100000: represents BSL 2048 bits; 196 01000000: represents BSL 4096 bits; 198 Each bit represents one BSL. When there are two or more bits set, 199 that means the sending BFR supports more than one BSL. For example, 200 if the BSL Identifier is 00010101, it means the sending BFR supports 201 1024 bits, 256 bits and 64 bits. 203 Each BFR sub-domain MUST be associated with a single IS-IS topology. 205 On the other hand, the BIER-Lite sub-TLV, which encapsulates the BSL 206 information together with the BIER Info sub-TLV, may be a 207 complementation and an extension of BIER Info sub-TLV defined in 208 [I-D.ietf-bier-isis-extensions]. Additionally, adding an M 209 identifier in the BIER Info sub-TLV to be compatible with BIER MPLS 210 encapsulation sub-sub-TLV defined in [I-D.ietf-bier-isis-extensions]. 211 So, BIER-Lite sub-TLV can also multiplex and extend BIER Info sub-TLV 212 defined in [I-D.ietf-bier-isis-extensions] instead of defining a new 213 TLV. 215 4. Flooding of BIER-Lite Information 217 Flooding of the IS-IS Extended Reachablity TLVs that is used for 218 advertising BIER-Lite sub-TLV should be infrequently. 220 5. Considerations on BIER-Lite 222 TBD. 224 6. Security Considerations 226 It will be considered in a future revision. 228 7. IANA Considerations 230 This document can request a new allocation from IS-IS Extended 231 Reachablity sub-TLV registry for BIER-Lite sub-TLV. Or it can 232 multiplex and extend M information and BSL Identifier information to 233 BIER Info sub-TLV defined in [I-D.ietf-bier-isis-extensions]. 235 8. References 237 8.1. Normative References 239 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 240 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 241 RFC2119, March 1997, 242 . 244 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 245 Topology (MT) Routing in Intermediate System to 246 Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/ 247 RFC5120, February 2008, 248 . 250 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 251 Engineering", RFC 5305, DOI 10.17487/RFC5305, 252 October 2008, . 254 [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, 255 DOI 10.17487/RFC5308, October 2008, 256 . 258 8.2. Informative References 260 [I-D.ietf-bier-architecture] 261 Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and 262 S. Aldrin, "Multicast using Bit Index Explicit 263 Replication", draft-ietf-bier-architecture-02 (work in 264 progress), July 2015. 266 [I-D.ietf-bier-isis-extensions] 267 Ginsberg, L., Aldrin, S., Zhang, J., and T. Przygienda, 268 "BIER support via ISIS", 269 draft-ietf-bier-isis-extensions-00 (work in progress), 270 April 2015. 272 [I-D.ietf-bier-mpls-encapsulation] 273 Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J., and 274 S. Aldrin, "Encapsulation for Bit Index Explicit 275 Replication in MPLS Networks", 276 draft-ietf-bier-mpls-encapsulation-02 (work in progress), 277 August 2015. 279 [I-D.ietf-bier-ospf-bier-extensions] 280 Psenak, P., Kumar, N., Wijnands, I., Dolganow, A., 281 Przygienda, T., Zhang, J., and S. Aldrin, "OSPF Extensions 282 For BIER", draft-ietf-bier-ospf-bier-extensions-00 (work 283 in progress), April 2015. 285 Authors' Addresses 287 Cui Wang 288 ZTE Corporation 289 No.50 Software Avenue, Yuhuatai District 290 Nanjing 291 China 293 Email: wang.cui1@zte.com.cn 295 Zheng Zhang 296 ZTE Corporation 297 No.50 Software Avenue, Yuhuatai District 298 Nanjing 299 China 301 Email: zhang.zheng@zte.com.cn