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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PIM WG Yiqun Cai 3 Internet Draft Heidi Ou 4 Intended Status: Proposed Standard 5 Expires: July 7, 2009 Cisco Systems, Inc. 7 January 7, 2009 9 PIM Multi-Topology ID (MT-ID) Join-Attribute 11 draft-ietf-pim-mtid-00.txt 13 Status of this Memo 15 This Internet-Draft is submitted to IETF in full conformance with the 16 provisions of BCP 78 and BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on July 7, 2009. 36 Copyright Notice 38 Copyright (c) 2009 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. 48 Abstract 50 This document introduces a new type of PIM Join Attribute that 51 extends PIM signaling to identify a topology that should be used when 52 constructing a particular multicast distribution tree. 54 Table of Contents 56 1 Specification of Requirements ...................... 2 57 2 Introduction ....................................... 3 58 3 Functional Overview ................................ 3 59 3.1 PIM RPF Topology ................................... 3 60 3.2 PIM MT-ID .......................................... 4 61 3.3 Applicability ...................................... 4 62 4 Protocol Specification of PIM MT-ID ................ 5 63 4.1 Sending PIM MT-ID Join Attribute ................... 5 64 4.2 Receiving PIM MT-ID Join Attribute ................. 5 65 4.3 Validating PIM MT-ID Join Attribute ................ 6 66 4.4 Conflict Resolution ................................ 6 67 4.4.1 Upstream Routers ................................... 6 68 4.4.2 Downstream Routers ................................. 7 69 5 PIM MT-ID Join Attribute TLV Format ................ 7 70 6 IANA Considerations ................................ 8 71 7 Security Considerations ............................ 8 72 8 Acknowledgments .................................... 8 73 9 Authors' Addresses ................................. 8 74 10 Normative References ............................... 9 75 11 Informative References ............................. 9 77 1. Specification of Requirements 79 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 80 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 81 document are to be interpreted as described in [RFC2119]. 83 2. Introduction 85 Some unicast protocols, such as OSPF and IS-IS, allow a single 86 network to be viewed as multiple topologies [RFC4915, RFC5120]. This 87 enables PIM to construct multicast distribution trees using separate 88 network paths even when the roots of the trees are the same. 90 This capability can be used to improve the resilience of multicast 91 applications. For instance, a multicast stream can be duplicated and 92 transported using different network layer addresses simultaneously. 93 Assuming that two source trees, (S1, G1) and (S1, G2), are used for 94 the stream. By using MT capable unicast routing protocols and 95 procedures described in this document, it is possible to construct 96 two source trees for (S1, G1) and (S1, G2) in such a way that they do 97 not share any transit network segment. As a result, a single network 98 failure will not cause any loss to the stream. 100 This draft introduces a new type of PIM Join Attribute used to encode 101 the identity of the topology PIM uses for RPF. It is based on 102 [RFC5384], and specifies additional procedures and rules to process 103 the attribute and resolve conflict. 105 3. Functional Overview 107 3.1. PIM RPF Topology 109 PIM RPF topology is a collection of routes used by PIM to perform RPF 110 operation when building shared or source trees. In the rest of the 111 document, PIM RPF topology may be simply referred to as "topology" 112 when there is no ambiguity. 114 In a multi-topology environment, multiple RPF topologies can be 115 created in the same network. A particular source may be reachable in 116 only one of the topologies, or in several of them via different 117 paths. 119 To select the RPF topology for a particular multicast distribution 120 tree, one or more of the following can be done. 122 1. configure a policy that maps a group range to a topology. When 123 RPF information needs to be resolved for the RP or the sources 124 for a group within the range, the RPF lookup takes place in the 125 specified topology. This can be used for PIM-SM/SSM/Bidir. 127 2. configure a policy that maps a source prefix range to a 128 topology. This can be used for PIM-SM and PIM-SSM. 130 3. use the topology identified by the Join Attribute encoding in 131 the received PIM packets. 133 The details of the first two methods are implementation specific and 134 are not discussed in this document. The specification to support the 135 third method is included in this document. 137 3.2. PIM MT-ID 139 For each PIM RPF topology created, a unique numerical ID is assigned. 140 This ID is called PIM MT-ID. PIM MT-ID has the following property, 142 - this value is not required to be the same as the MT-ID used by 143 the unicast routing protocols that contribute routes to the 144 topology. Although in practice, when only one unicast routing 145 protocol (such as OSPF or IS-IS) is used, PIM MT-ID is typically 146 assigned the same value as the IGP topology identifier. 148 - this value must be unique and consistent within the network 149 domain for the same topology 151 - 0 is reserved as the default, and MUST NOT be included in the 152 join attribute encoding. 154 - how to assign a PIM MT-ID to a topology is decided by the network 155 administrator and is outside the scope of this document 157 3.3. Applicability 159 The PIM MT-ID join attribute described in this draft applies to PIM 160 Join/Assert packets used by PIM SM/SSM/Bidir. It is not used in any 161 other PIM packets, such as Prune, Register, Register-Stop, Graft, 162 Graft-ack, DF Election, Candidate-RP, and Bootstrap. As such, it can 163 only be used to build shared or source trees for PIM SM/SSM and PIM- 164 bidir downstream. 166 When this attribute is used in combination with RPF vectors defined 167 in [ID.ietf-pim-rpf-vector] [ID.ietf-l3vpn-2547bis-mcast], they are 168 processed against the topology identified by the PIM MT-ID attribute. 170 4. Protocol Specification of PIM MT-ID 172 4.1. Sending PIM MT-ID Join Attribute 174 When a PIM router originates a PIM Join/Assert packet, it may choose 175 to encode PIM MT-ID of the topology in which RPF lookup takes place 176 for the corresponding (*,G) or (S,G) entry. The chosen PIM MT-ID MUST 177 be the one decided by local topology selection configuration if it 178 exists, or the one received from downstream routers after conflict 179 resolution procedures are applied. 181 The following are the exceptions, 183 - a router MUST NOT attach the attribute if PIM MT-ID is 0. The 184 value of 0 is ignored on reception. 186 - a router SHOULD NOT do so if the upstream router, or one of the 187 routers on the LAN does not include "PIM Join Attribute" option 188 in its Hello packets. 190 - a router SHOULD NOT encode PIM MT-ID for pruned sources. If 191 encoded, the value is ignored. 193 4.2. Receiving PIM MT-ID Join Attribute 195 When a PIM router receives a PIM MT-ID join attribute in a 196 Join/Assert packet, it MUST perform the following, 198 - validate the attribute encoding. The detail is described in the 199 next section. 201 - if the join attribute is valid, use the rules described in the 202 section "Conflict Resolution" to determine a PIM MT-ID to use. 204 - use the topology identified by the selected PIM MT-ID to perform 205 RPF lookup for the (*,G)/(S,G) entry unless a different topology 206 is specified by a local configuration. The local configuration 207 always takes precedence. 209 4.3. Validating PIM MT-ID Join Attribute 211 An encoded PIM MT-ID join attribute is valid if all of the following 212 conditions are satisfied, 214 - there is at most 1 PIM MT-ID attribute encoded. 216 - the length field must be 2 and the value must not be 0. 218 If an encoded PIM MT-ID join attribute is deemed invalid, it is 219 ignored and not forwarded further. The packet is processed as if the 220 attribute were not present. 222 It is important to note that, if the sender is not a PIM neighbor 223 that has included "PIM Join Attribute" option in its Hello packets, 224 or if the "F" bit in the encoding is reset, the encoding may still be 225 considered valid by an implementation and is allowed to be forwarded. 227 4.4. Conflict Resolution 229 Depending on whether a PIM router is an upstream or a downstream 230 router, the action it takes to resolve conflicting PIM MT-ID 231 attributes differs. The detail is described below. 233 4.4.1. Upstream Routers 235 If an upstream router has a local configuration that specifies a 236 different topology than that from an incoming Join/Assert packet, 237 including the case PIM MT-ID is not encoded in the incoming packet, 238 it is not considered a conflict. 240 A conflict occurs when a router doesn't have local topology selection 241 policy and it has received different PIM MT-ID from Join packets sent 242 by its downstream routers or Assert packets from another forwarding 243 router on the LAN. 245 - if an upstream router receives different PIM MT-ID attributes 246 from PIM Join packets, it MUST follow the rules specified in 247 [RFC5384] to select one. The PIM MT-ID chosen will be the one 248 encoded for its upstream neighbor. 250 - if an upstream router receives a different PIM MT-ID attribute in 251 an ASSERT packet, it MUST use the tie-breaker rules as specified 252 in [RFC4601] to determine an ASSERT winner. PIM MT-ID is not 253 considered in deciding a winner from Assert process. 255 4.4.2. Downstream Routers 257 A conflict is detected by a downstream router when it sees a 258 different PIM MT-ID attribute from other routers on the LAN, 259 regardless of whether the router has local topology selection policy 260 or not. 262 - if a downstream router sees different PIM MT-ID attributes from 263 PIM Join packets, it MUST follow the specification of [RFC4601] 264 as if the attribute did not exist. For example, the router 265 suppresses its own Join packet if a Join for the same (S,G) is 266 seen. 268 The router MUST NOT use the rules specified in [RFC5384] to 269 select a PIM MT-ID from Join packets sent by other downstream 270 routers. 272 - if a downstream router sees its preferred upstream router loses 273 in the ASSERT process, and the ASSERT winner uses a different PIM 274 MT-ID, the downstream router SHOULD still choose the ASSERT 275 winner as the RPF neighbour but it MUST NOT encode PIM MT-ID when 276 sending Join packets to it. 278 5. PIM MT-ID Join Attribute TLV Format 280 0 1 2 3 281 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 1 282 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 283 |F|E| Attr Type | Length | Value | 284 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 286 - F bit: 1 Transitive Attribute. 288 - E bit: As specified by [RFC5384] 290 - Attr Type: 3. 292 - Length: 2. 294 - Value: PIM MT-ID, 1 to 65535. 296 6. IANA Considerations 298 A new PIM Join Attribute type needs to be assigned. 3 is proposed for 299 now. 301 7. Security Considerations 303 As a type of PIM Join Attribute, the security considerations 304 described in [RFC5384] apply here. Specifically, malicious alteration 305 of PIM MT-ID may cause the resiliency goals to be violated. 307 8. Acknowledgments 309 The authors would like to thank Eric Rosen, Ice Wijnands, Dino 310 Farinacci, Colby Barth and Les Ginsberg for their input. 312 9. Authors' Addresses 314 Yiqun Cai 315 Cisco Systems, Inc 316 170 West Tasman Drive 317 San Jose, CA 95134 319 E-mail: ycai@cisco.com 321 Heidi Ou 322 Cisco Systems, Inc 323 170 West Tasman Drive 324 San Jose, CA 95134 326 E-mail: hou@cisco.com 328 10. Normative References 330 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 331 Requirement Levels", RFC 2119, March 1997. 333 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 334 "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol 335 Specification (Revised)", RFC 4601, August 2006. 337 [RFC5384] A. Boers, I. Wijnands, E. Rosen, "The Protocol Independent 338 Multicast (PIM) Join Attribute Format", RFC 5384, November 2008 340 11. Informative References 342 [RFC4915] P. Psenak, S. Mirtorabi, A. Roy, L. Nguyen, P. Pillay- 343 Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, June 2007. 345 [RFC5120] T. Przygienda, N. Shen, N. Sheth, "M-ISIS: Multi Topology 346 (MT) Routing in Intermediate System to Intermediate Systems (IS- 347 ISs)", RFC 5120, February 2008. 349 [ID.ietf-pim-rpf-vector] I. Wijnands, A. Boers, E. Rosen, "The RPF 350 Vector TLV", draft-ietf-pim-rpf-vector. 352 [ID.ietf-l3vpn-2547bis-mcast] E. Rosen,R Aggarwal, "Multicast in 353 MPLS/BGP IP VPNs", draft-ietf-l3vpn-2547bis-mcast