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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: June 2, 2014 Uwe Joorde 7 Deutsche Telekom 9 December 2, 2013 11 Encoding mLDP FECs in the NLRI of BGP MCAST-VPN Routes 13 draft-ietf-l3vpn-mvpn-mldp-nlri-04.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 3. Encoding an mLDP FEC in the MCAST-VPN NLRI 193 This section specifies the way to encode an mLDP FEC element in the 194 NLRI of the following three MCAST-VPN route types defined in [MVPN- 195 BGP]: 197 - C-multicast Source Tree Join, 199 - S-PMSI A-D route, and 201 - Leaf A-D route. 203 The other four MCAST-VPN route types defined in [MVPN-BGP] do not 204 ever need to carry mLDP FEC Elements. The C-multicast Shared Tree 205 Join route and the Source Active A-D route are used to communicate 206 state about unidirectional shared trees; since mLDP does not have 207 unidirectional shared trees, these routes are not used to signal mLDP 208 states. The Intra-AS I-PMSI A-D route and the Inter-AS I-PMSI A-D 209 route do not identify specific customer multicast states, and hence 210 do not carry any information that is specific to the customer's 211 multicast control protocol. 213 Per [MVPN-BGP], the first octet of the NLRI of an MCAST-VPN route is 214 a "route type". Only values 1-7 are defined. The high order 5 bits 215 of that octet are thus always zero. 217 This document updates [MVPN-BGP] by specifying a use for the high 218 order 2 bits of the "route type" octet. The following two values are 219 defined: 221 - If the two high order bits are both zero, the NLRI is as 222 specified in [MVPN-BGP] and/or [MVPN-WILDCARDS]. 224 - If the two high order bits have the value 01, the NLRI encoding 225 is modified as follows: the "Multicast Source Length", "Multicast 226 Source", "Multicast Group" length, and "Multicast Group" fields 227 are omitted, and in their place is a single mLDP FEC Element, as 228 defined in [mLDP]. See section 2.2 of [mLDP] for a diagram of 229 the mLDP FEC element. 231 The other two possible values (11 and 10) for the two high order bits 232 may be used at a later time to identify other multicast control 233 protocols. 235 As a result, the NLRI of an S-PMSI A-D route with an mLDP FEC in its 236 NLRI will consist of a Route Distinguisher, followed by the mLDP FEC, 237 followed by the "Originating Router's IP Address Field". 239 The NLRI of a C-multicast Source Tree Join route with an mLDP FEC in 240 its NLRI will consist of a Route Distinguisher, followed by the 241 Source AS, followed by the mLDP FEC. 243 In a Leaf A-D route that has been derived from an S-PMSI A-D route, 244 the "route key" field remains the NLRI of the S-PMSI A-D route from 245 which it was derived. 247 In a Leaf A-D route that has not been derived from an S-PMSI A-D 248 route, the "route key" field is as specified in [SEGMENTED-MVPN], 249 except that the "Multicast Source Length", "Multicast Source", 250 "Multicast Group" length, and "Multicast Group" fields are omitted, 251 and in their place is a single mLDP FEC Element. Thus the route key 252 field consists of a Route Distinguisher, an MLDP FEC element, and the 253 IP address of the Ingress PE router. 255 An mLDP FEC element contains an "address family" field from IANA's 256 "Address Family Numbers" registry. This identifies the address 257 family of the "root node address" field of the FEC element. When an 258 mLDP FEC element is encoded into the NLRI of an a BGP update whose 259 SAFI is MCAST-VPN, the address family of the root node (as indicated 260 in the FEC element) MUST "correspond to" the address family that is 261 identified in the AFI field of that BGP update. These two "address 262 family" fields are considered to "correspond" under the following 263 conditions: 265 - they contain identical values, or 266 - the BGP update's AFI field identifies IPv4 as the address family, 267 and the mLDP FEC element identifies "Multi-Topology IPv4" as the 268 address family of the root node, or 270 - the BGP update's AFI field identifies IPv6 as the address family, 271 and the mLDP FEC element identifies "Multi-Topology IPv6" as the 272 address family of the root node. 274 For more information about the "multi-topology" address families, see 275 [LDP-MT] and [mLDP-MT]. 277 4. Wildcards 279 [MVPN-WILDCARDS] specifies encodings and procedures that allow 280 "wildcards" to be specified in the NLRI of S-PMSI A-D routes. A set 281 of rules are given that specify when a customer multicast flow 282 "matches" a given S-PMSI A-D route whose NLRI contains wildcards. 283 However, the use of these wildcards is defined only for the case 284 where the customer is using PIM as its multicast control protocol. 285 The use of wildcards when the customer is using mLDP as its multicast 286 control protocol is outside the scope of this document. 288 5. IANA Considerations 290 [MVPN-BGP] does not create a registry for the allocation of new 291 MCAST-VPN Route Type values. In retrospect, it seems that it should 292 have done so. IANA should create a registry called "MCAST-VPN Route 293 Types", referencing this document and [MVPN-BGP]. The allocation 294 policy should be "Standards Action with Early Allocation", and the 295 assignable values are in the range 0-0xFF. The following values 296 should be assigned: 298 - 0x00: Reserved 300 - 0x01: Intra-AS I-PMSI A-D route (reference: [MVPN-BGP]) 302 - 0x02: Inter-AS I-PMSI A-D route (reference: [MVPN-BGP]) 304 - 0x03: S-PMSI A-D route for PIM as the C-multicast control 305 protocol (reference: [MVPN-BGP]) 307 - 0x43: S-PMSI A-D route for mLDP as the C-multicast control 308 protocol (reference: this document) 310 - 0x04: Leaf A-D route for PIM as the C-multicast control protocol 311 (reference: [MVPN-BGP]) 313 - 0x44: Leaf A-D route for mLDP as the C-multicast control protocol 314 (reference: this document) 316 - 0x05: Source Active A-D route for PIM as the C-multicast control 317 protocol (reference: [MVPN-BGP]) 319 - 0x06: Shared Tree Join route for PIM as the C-multicast control 320 protocol (reference: [MVPN-BGP]) 322 - 0x07: Source Tree Join route for PIM as the C-multicast control 323 protocol (reference: [MVPN-BGP]) 325 - 0x47: Source Tree Join route for mLDP as the C-multicast control 326 protocol (reference: this document) 328 6. Security Considerations 330 This document specifies a method of encoding an mLDP FEC element in 331 the NLRI of some of the BGP Update messages that are specified in 332 [MVPN-BGP]. The security considerations of [mLDP] and of [MVPN-BGP] 333 are applicable, but no new security considerations are raised. 335 7. Acknowledgments 337 The authors wish to think Pradosh Mohapatra and Saquib Najam for 338 their ideas and comments. We also thank Yakov Rekhter for his 339 comments. 341 8. Authors' Addresses 343 IJsbrand Wijnands 344 Cisco Systems, Inc. 345 De kleetlaan 6a Diegem 1831 346 Belgium 347 E-mail: ice@cisco.com 348 Eric C. Rosen 349 Cisco Systems, Inc. 350 1414 Massachusetts Avenue 351 Boxborough, MA, 01719 352 E-mail: erosen@cisco.com 354 Uwe Joorde 355 Deutsche Telekom 356 Hammer Str. 216-226 357 D-48153 Muenster, Germany 358 E-mail: Uwe.Joorde@telekom.de 360 9. Normative References 362 [mLDP] "Label Distribution Protocol Extensions for Point-to- 363 Multipoint and Multipoint-to-Multipoint Label Switched Paths", 364 Wijnands, Minei, Kompella, Thomas, RFC 6388, November 2011 366 [MVPN-BGP] "BGP Encodings and Procedures for Multicast in MPLS/BGP IP 367 VPNs", Aggarwal, Rosen, Morin, Rekhter, RFC 6514, February 2012 369 [RFC2119] "Key words for use in RFCs to Indicate Requirement 370 Levels.", Bradner, RFC 2119, March 1997 372 10. Informative References 374 [GTM] "Global Table Multicast with BGP-MVPN Procedures", Zhang, 375 Giuliano, Rosen, Subramanian, Pacella, Schiller, draft-zzhang-l3vpn- 376 mvpn-global-table-mcast-01.txt, October 2013 378 [IGMP] "Internet Group Management Protocol, Version 3", Cain, 379 Deering, Kouvelas, Fenner, Thyagarajan, RFC 3376, October 2002 381 [LDP-MT] "LDP Extensions for Multi-Topology Routing", Zhao, et. al., 382 draft-ietf-mpls-ldp-multi-topology-09.txt, October 2013 384 [mLDP-MT] "mLDP Extensions for Multi Topology Routing", Wijnands, 385 Raza, draft-iwijnand-mpls-mldp-multi-topology-03.txt, June 2013 387 [MVPN-WILDCARDS], "Wildcards in Multicast VPN Auto-Discovery Routes", 388 Rosen, Rekhter, Hendrickx, Qiu, RFC 6625, May 2012 390 [PIM] "Protocol Independent Multicast - Sparse Mode (PIM-SM)", 391 Fenner, Handley, Holbrook, Kouvelas, August 2006, RFC 4601 393 [SEAMLESS-MCAST] "Inter-Area P2MP Segmented LSPs", Rekhter, Aggarwal, 394 Morin, Grosclaude, Leymann, Saad, draft-ietf-mpls-seamless- 395 mcast-08.txt, November 2013