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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 L3VPN Working Group IJsbrand Wijnands 3 Internet Draft Eric C. Rosen 4 Intended Status: Proposed Standard Cisco Systems, Inc. 5 Updates: 6514 6 Expires: May 27, 2014 Uwe Joorde 7 Deutsche Telekom 9 November 27, 2013 11 Encoding mLDP FECs in the NLRI of BGP MCAST-VPN Routes 13 draft-ietf-l3vpn-mvpn-mldp-nlri-03.txt 15 Abstract 17 Many service providers offer "BGP/MPLS IP VPN" service to their 18 customers. Existing IETF standards specify the procedures and 19 protocols that a service provider uses in order to offer this service 20 to customers who have IP unicast and IP multicast traffic in their 21 VPNs. It is also desirable to be able to support customers who have 22 MPLS multicast traffic in their VPNs. This document specifies the 23 procedures and protocol extensions that are needed to support 24 customers who use the Multicast Extensions to Label Distribution 25 Protocol (mLDP) as the control protocol for their MPLS multicast 26 traffic. Existing standards do provide some support for customers 27 who use mLDP, but only under a restrictive set of circumstances. 28 This document generalizes the existing support to include all cases 29 where the customer uses mLDP, without any restrictions. 31 Status of this Memo 33 This Internet-Draft is submitted to IETF in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF), its areas, and its working groups. Note that 38 other groups may also distribute working documents as Internet- 39 Drafts. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 45 The list of current Internet-Drafts can be accessed at 46 http://www.ietf.org/ietf/1id-abstracts.txt. 48 The list of Internet-Draft Shadow Directories can be accessed at 49 http://www.ietf.org/shadow.html. 51 Copyright and License Notice 53 Copyright (c) 2013 IETF Trust and the persons identified as the 54 document authors. All rights reserved. 56 This document is subject to BCP 78 and the IETF Trust's Legal 57 Provisions Relating to IETF Documents 58 (http://trustee.ietf.org/license-info) in effect on the date of 59 publication of this document. Please review these documents 60 carefully, as they describe your rights and restrictions with respect 61 to this document. Code Components extracted from this document must 62 include Simplified BSD License text as described in Section 4.e of 63 the Trust Legal Provisions and are provided without warranty as 64 described in the Simplified BSD License. 66 Table of Contents 68 1 Introduction .......................................... 3 69 2 Why This Document is Needed ........................... 4 70 3 Encoding an mLDP FEC in the MCAST-VPN NLRI ............ 5 71 4 Wildcards ............................................. 7 72 5 IANA Considerations ................................... 7 73 6 Security Considerations ............................... 8 74 7 Acknowledgments ....................................... 8 75 8 Authors' Addresses .................................... 8 76 9 Normative References .................................. 9 77 10 Informative References ................................ 9 78 1. Introduction 80 Many service providers (SPs) offer "BGP/MPLS IP VPN" service to their 81 customers. When a customer has IP multicast traffic in its VPN, the 82 service provider needs to signal the customer multicast states across 83 the backbone. A customer with IP multicast traffic is typically 84 using PIM ("Protocol Independent Multicast") [PIM] and/or IGMP 85 ("Internet Group Management Protocol") [IGMP] as the multicast 86 control protocol in its VPN. The IP multicast states of these 87 protocols are commonly denoted as "(S,G)" and/or "(*,G)" states, 88 where "S" is a multicast source address and "G" is a multicast group 89 address. [MVPN-BGP] specifies the way an SP may use BGP to signal a 90 customer's IP multicast states across the SP backbone. This is done 91 by using "Multiprotocol BGP" Updates whose "Subsequent Address 92 Family" value is "MCAST-VPN" (5). The NLRI ("Network Layer 93 Reachability Information") field of these Updates includes a customer 94 Multicast Source field and a customer Multicast Group field, thus 95 enabling the customer's (S,G) or (*,G) states to be encoded in the 96 NLRI. 98 It is also desirable for the BGP/MPLS IP VPN service to be able to 99 support customers who are using MPLS multicast, either instead of, or 100 in addition to, IP multicast. This document specifies the procedures 101 and protocol extensions needed to support customers who use mLDP 102 ("Multicast Extensions to Label Distribution Protocol") [mLDP] to 103 create and maintain Point-to-Multipoint (P2MP) and/or Multipoint-to- 104 Multipoint (MP2MP) Label Switched Paths (LSPs). While mLDP is not 105 the only protocol that can be used to create and maintain multipoint 106 LSPs, consideration of other MPLS multicast control protocols is 107 outside the scope of this document. 109 When a customer is using mLDP in its VPN, the customer multicast 110 states associated with mLDP are denoted by an mLDP "FEC Element" 111 ("Forwarding Equivalance Class element", see [mLDP]), instead of by 112 an (S,G) or (*,G). Thus it is necessary to have a way to encode a 113 customer's mLDP FEC Elements in the NLRI field of the BGP MCAST-VPN 114 routes. 116 While [MVPN-BGP] does specify a way of encoding an mLDP FEC Element 117 in the MCAST-VPN NLRI field, the encoding specified therein makes a 118 variety of restrictive assumptions about the customer's use of mLDP. 119 (These assumptions are described in section 2 of this document.) The 120 purpose of this document is to update [MVPN-BGP] so that customers 121 using mLDP in their VPNs can be supported even when those assumptions 122 do not hold. 124 Some SPs use the MVPN procedures to provide "global table multicast" 125 service (i.e., multicast service that is not in the context of a VPN) 126 to customers. Methods for doing this are specified in [GTM] and in 127 [SEAMLESS-MCAST]. The procedures described in this document can be 128 used along with the procedures of [GTM] or [SEAMLESS-MCAST] to 129 provide global table multicast service to customers that use MPLS 130 multicast in a global table context. 132 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 133 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 134 document are to be interpreted as described in [RFC2119]. 136 2. Why This Document is Needed 138 An mLDP FEC Element consists of a FEC Type, a Root Node, and an 139 Opaque Value. mLDP uses several FEC types, and in particular, uses 140 the FEC type to distinguish between P2MP LSPs and MP2MP LSPs. 142 Section 11.1.2 of [MVPN-BGP] ("Originating routes: mLDP as the C- 143 multicast control protocol") states: 145 Whenever a PE receives from one of its CEs a P2MP Label Map over interface I, where X is the Root Node Address, Y is 147 the Opaque Value, and L is an MPLS label ... the PE constructs a 148 Source Tree Join C-multicast route whose MCAST-VPN NLRI contains 149 X as the Multicast Source field, and Y as the Multicast Group 150 field. 152 In other words, the Root Node of the mLDP FEC Element appears in the 153 Multicast Source Field, and the Opaque Value of the mLDP FEC Element 154 appears in the Multicast Group field. 156 This method of encoding an mLDP FEC in an MCAST-VPN NLRI can only be 157 used if all of the following conditions hold: 159 1. A customer using mLDP is not also using PIM/IGMP. 161 The encoding in [MVPN-BGP] does not specify any way in which 162 one can determine, upon receiving a BGP Update, whether the 163 Multicast Group field contains an IP address or whether it 164 contains an mLDP FEC Element Opaque Value. Therefore it may 165 not uniquely identify a customer multicast state if the 166 customer is using both PIM/IGMP and mLDP in its VPN. 168 2. A customer using mLDP is using only the mLDP P2MP FEC Element, 169 and is not using the mLDP MP2MP FEC Element. 171 The encoding in [MVPN-BGP] does not specify any way to encode 172 the type of the mLDP FEC Element; it just assumes it to be a 173 P2MP FEC Element. 175 3. A customer using mLDP is using only an mLDP Opaque Value type 176 for which the Opaque Value is exactly 32 bits or 128 bits long. 178 The use of Multicast Group fields that have other lengths is 179 declared by [MVPN-BGP] to be "out of scope" of that document 180 (see, e.g., section 4.3 of that document). 182 This condition holds if the customer uses only the mLDP 183 "Generic LSP Identifier" Opaque Value type (defined in [mLDP]). 184 However, mLDP supports many other Opaque Value types whose 185 length is not restricted to be 32 or 128 bits. 187 The purpose of this document is to update [MVPN-BGP] so that 188 customers using mLDP can be supported, even when these conditions do 189 not hold. 191 In addition, neither [MVPN-BGP] nor [MVPN-WILDCARDS] addresses the 192 use of "wild cards" when the MCAST-VPN NLRI encodes an MLDP FEC. 193 This document specifies a way to encode mLDP FEC Element wild cards 194 in the NLRI of the relevant BGP MCAST-VPN routes. 196 3. Encoding an mLDP FEC in the MCAST-VPN NLRI 198 This section specifies the way to encode an mLDP FEC element in the 199 NLRI of the following three MCAST-VPN route types defined in [MVPN- 200 BGP]: 202 - C-multicast Source Tree Join, 204 - S-PMSI A-D route, and 206 - Leaf A-D route. 208 The other four MCAST-VPN route types defined in [MVPN-BGP] do not 209 ever need to carry mLDP FEC Elements. The C-multicast Shared Tree 210 Join route and the Source Active A-D route are used to communicate 211 state about unidirectional shared trees; since mLDP does not have 212 unidirectional shared trees, these routes are not used to signal mLDP 213 states. The Intra-AS I-PMSI A-D route and the Inter-AS I-PMSI A-D 214 route do not identify specific customer multicast states, and hence 215 do not carry any information that is specific to the customer's 216 multicast control protocol. 218 Per [MVPN-BGP], the first octet of the NLRI of an MCAST-VPN route is 219 a "route type". Only values 1-7 are defined. The high order 5 bits 220 of that octet are thus always zero. 222 This document updates [MVPN-BGP] by specifying a use for the high 223 order 2 bits of the "route type" octet. The following two values are 224 defined: 226 - If the two high order bits are both zero, the NLRI is as 227 specified in [MVPN-BGP] and/or [MVPN-WILDCARDS]. 229 - If the two high order bits have the value 01, the NLRI encoding 230 is modified as follows: the "Multicast Source Length", "Multicast 231 Source", "Multicast Group" length, and "Multicast Group" fields 232 are omitted, and in their place is a single mLDP FEC Element, as 233 defined in [mLDP]. See section 2.2 of [mLDP] for a diagram of 234 the mLDP FEC element. 236 The other two possible values (11 and 10) for the two high order bits 237 may be used at a later time to identify other multicast control 238 protocols. 240 As a result, the NLRI of an S-PMSI A-D route with an mLDP FEC in its 241 NLRI will consist of a Route Distinguisher, followed by the mLDP FEC, 242 followed by the "Originating Router's IP Address Field". 244 The NLRI of a C-multicast Source Tree Join route with an mLDP FEC in 245 its NLRI will consist of a Route Distinguisher, followed by the 246 Source AS, followed by the mLDP FEC. 248 In a Leaf A-D route that has been derived from an S-PMSI A-D route, 249 the "route key" field remains the NLRI of the S-PMSI A-D route from 250 which it was derived. 252 In a Leaf A-D route that has not been derived from an S-PMSI A-D 253 route, the "route key" field is as specified in [SEGMENTED-MVPN], 254 except that the "Multicast Source Length", "Multicast Source", 255 "Multicast Group" length, and "Multicast Group" fields are omitted, 256 and in their place is a single mLDP FEC Element. Thus the route key 257 field consists of a Route Distinguisher, an MLDP FEC element, and the 258 IP address of the Ingress PE router. 260 An mLDP FEC element contains an "address family" field from IANA's 261 "Address Family Numbers" registry. This identifies the address 262 family of the "root node address" field of the FEC element. When an 263 mLDP FEC element is encoded into the NLRI of an a BGP update whose 264 SAFI is MCAST-VPN, the address family of the root node (as indicated 265 in the FEC element) MUST "correspond to" the address family that is 266 identified in the AFI field of that BGP update. These two "address 267 family" fields are considered to "correspond" under the following 268 conditions: 270 - they contain identical values, or 272 - the BGP update's AFI field identifies IPv4 as the address family, 273 and the mLDP FEC element identifies "Multi-Topology IPv4" as the 274 address family of the root node, or 276 - the BGP update's AFI field identifies IPv6 as the address family, 277 and the mLDP FEC element identifies "Multi-Topology IPv6" as the 278 address family of the root node. 280 For more information about the "multi-topology" address families, see 281 [LDP-MT] and [mLDP-MT]. 283 4. Wildcards 285 [MVPN-WILDCARDS] specifies encodings and procedures that allow 286 "wildcards" to be specified in the NLRI of S-PMSI A-D routes. A set 287 of rules are given that specify when a customer multicast flow 288 "matches" a given S-PMSI A-D route whose NLRI contains wildcards. 289 However, the use of these wildcards is defined only for the case 290 where the customer is using PIM as its multicast control protocol. 291 The use of wildcards when the customer is using mLDP as its multicast 292 control protocol is outside the scope of this document. 294 5. IANA Considerations 296 [MVPN-BGP] does not create a registry for the allocation of new 297 MCAST-VPN Route Type values. In retrospect, it seems that it should 298 have done so. IANA should create a registry called "MCAST-VPN Route 299 Types", referencing this document and [MVPN-BGP]. The allocation 300 policy should be "Standards Action with Early Allocation", and the 301 assignable values are in the range 0-0xFF. The following values 302 should be assigned: 304 - 0x00: Reserved 306 - 0x01: Intra-AS I-PMSI A-D route (reference: [MVPN-BGP]) 308 - 0x02: Inter-AS I-PMSI A-D route (reference: [MVPN-BGP]) 310 - 0x03: S-PMSI A-D route for PIM as the C-multicast control 311 protocol (reference: [MVPN-BGP]) 313 - 0x43: S-PMSI A-D route for mLDP as the C-multicast control 314 protocol (reference: this document) 316 - 0x04: Leaf A-D route for PIM as the C-multicast control protocol 317 (reference: [MVPN-BGP]) 319 - 0x44: Leaf A-D route for mLDP as the C-multicast control protocol 320 (reference: this document) 322 - 0x05: Source Active A-D route for PIM as the C-multicast control 323 protocol (reference: [MVPN-BGP]) 325 - 0x06: Shared Tree Join route for PIM as the C-multicast control 326 protocol (reference: [MVPN-BGP]) 328 - 0x07: Source Tree Join route for PIM as the C-multicast control 329 protocol (reference: [MVPN-BGP]) 331 - 0x47: Source Tree Join route for mLDP as the C-multicast control 332 protocol (reference: this document) 334 6. Security Considerations 336 This document specifies a method of encoding an mLDP FEC element in 337 the NLRI of some of the BGP Update messages that are specified in 338 [MVPN-BGP]. The security considerations of [mLDP] and of [MVPN-BGP] 339 are applicable, but no new security considerations are raised. 341 7. Acknowledgments 343 The authors wish to think Pradosh Mohapatra and Saquib Najam for 344 their ideas and comments. We also thank Yakov Rekhter for his 345 comments. 347 8. Authors' Addresses 349 IJsbrand Wijnands 350 Cisco Systems, Inc. 351 De kleetlaan 6a Diegem 1831 352 Belgium 353 E-mail: ice@cisco.com 354 Eric C. Rosen 355 Cisco Systems, Inc. 356 1414 Massachusetts Avenue 357 Boxborough, MA, 01719 358 E-mail: erosen@cisco.com 360 Uwe Joorde 361 Deutsche Telekom 362 Hammer Str. 216-226 363 D-48153 Muenster, Germany 364 E-mail: Uwe.Joorde@telekom.de 366 9. Normative References 368 [mLDP] "Label Distribution Protocol Extensions for Point-to- 369 Multipoint and Multipoint-to-Multipoint Label Switched Paths", 370 Wijnands, Minei, Kompella, Thomas, RFC 6388, November 2011 372 [MVPN-BGP] "BGP Encodings and Procedures for Multicast in MPLS/BGP IP 373 VPNs", Aggarwal, Rosen, Morin, Rekhter, RFC 6514, February 2012 375 [RFC2119] "Key words for use in RFCs to Indicate Requirement 376 Levels.", Bradner, RFC 2119, March 1997 378 10. Informative References 380 [GTM] "Global Table Multicast with BGP-MVPN Procedures", Zhang, 381 Giuliano, Rosen, Subramanian, Pacella, Schiller, draft-zzhang-l3vpn- 382 mvpn-global-table-mcast-01.txt, October 2013 384 [IGMP] "Internet Group Management Protocol, Version 3", Cain, 385 Deering, Kouvelas, Fenner, Thyagarajan, RFC 3376, October 2002 387 [LDP-MT] "LDP Extensions for Multi-Topology Routing", Zhao, et. al., 388 draft-ietf-mpls-ldp-multi-topology-09.txt, October 2013 390 [mLDP-MT] "mLDP Extensions for Multi Topology Routing", Wijnands, 391 Raza, draft-iwijnand-mpls-mldp-multi-topology-03.txt, June 2013 393 [MVPN-WILDCARDS], "Wildcards in Multicast VPN Auto-Discovery Routes", 394 Rosen, Rekhter, Hendrickx, Qiu, RFC 6625, May 2012 396 [PIM] "Protocol Independent Multicast - Sparse Mode (PIM-SM)", 397 Fenner, Handley, Holbrook, Kouvelas, August 2006, RFC 4601 399 [SEAMLESS-MCAST] "Inter-Area P2MP Segmented LSPs", Rekhter, Aggarwal, 400 Morin, Grosclaude, Leymann, Saad, draft-ietf-mpls-seamless- 401 mcast-08.txt, November 2013