idnits 2.17.1 draft-ietf-pim-anycast-rp-00.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** Looks like you're using RFC 2026 boilerplate. This must be updated to follow RFC 3978/3979, as updated by RFC 4748. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- == No 'Intended status' indicated for this document; assuming Proposed Standard == The page length should not exceed 58 lines per page, but there was 6 longer pages, the longest (page 2) being 60 lines == It seems as if not all pages are separated by form feeds - found 0 form feeds but 7 pages Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack a Security Considerations section. ** The document seems to lack an IANA Considerations section. (See Section 2.2 of https://www.ietf.org/id-info/checklist for how to handle the case when there are no actions for IANA.) ** The document seems to lack separate sections for Informative/Normative References. All references will be assumed normative when checking for downward references. ** There are 11 instances of too long lines in the document, the longest one being 6 characters in excess of 72. ** The document seems to lack a both a reference to RFC 2119 and the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords. RFC 2119 keyword, line 62: '... acting as an RP MUST be configured wi...' RFC 2119 keyword, line 107: '... o RP1 MAY join back to the source-t...' RFC 2119 keyword, line 108: '...S1. However, RP1 MUST create (S1,G) st...' RFC 2119 keyword, line 116: '... o RP2 MAY join back to the source-t...' RFC 2119 keyword, line 117: '...S1. However, RP2 MUST create (S1,G) st...' (2 more instances...) Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the RFC 3978 Section 5.4 Copyright Line does not match the current year -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (November 9, 2003) is 7466 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 2362 (ref. '1') (Obsoleted by RFC 4601, RFC 5059) ** Downref: Normative reference to an Informational draft: draft-ietf-mboned-anycast-rp (ref. '2') Summary: 8 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Dino Farinacci 3 INTERNET-DRAFT Procket Networks 4 Expiration Date: May 2004 Yiqun Cai 5 cisco Systems 6 November 9, 2003 8 Anycast-RP using PIM 9 11 Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC2026. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 Copyright Notice 34 Copyright (C) The Internet Society (2002). All Rights Reserved. 36 Abstract 38 This proposal allows Anycast-RP to be used inside a domain which runs 39 PIM only. There are no other multicast protocols required to support 40 Anycast-RP, such as MSDP, which has been used traditionally to solve 41 this problem. 43 1. Introduction 45 Anycast-RP as described in [2] is a mechanism ISP-based backbones 46 have used to get fast convergence when a PIM Rendezvous Point (RP) 47 router fails. To allow receivers and sources to Rendezvous to the 48 closest RP, the packets from a source needs to get to all RPs to find 49 joined receivers. 51 This notion of receivers finding sources is the fundamental problem 52 of source discovery which MSDP was intended to solve. However, if one 53 would like to retain the Anycast-RP benefits from [2] with less 54 protocol machinery, removing MSDP from the solution space is an 55 option. 57 This draft extends the Register mechanism in PIM so Anycast-RP 58 functionality can be retained without using MSDP. 60 2. Requirements 62 o Each router acting as an RP MUST be configured with a loopback 63 interface using the same (shared) IP address. This address is used to 64 tell other routers in the PIM domain, what IP address to use for the 65 RP address. 67 o The RP address or a prefix that covers the RP address is injected 68 into the unicast routing system inside of the domain. 70 o Each RP configures all other RPs used in the Anycast-RP set. This 71 must be consistently configured in all RPs in the set. 73 3. Mechanism 75 The following diagram illustrates a domain using 3 RPs where 76 receivers are joining to the closest RP according to where unicast 77 routing metrics take them and 2 sources sending packets to their 78 respective RPs. 80 S1-----RP1 RP2 RP3------S3 81 / \ | 82 / \ | 83 R1 R1' R2 85 Assume the above scenario is completely connected where R1, R1', and 86 R2 are receivers for a group, and S1 and S2 send to that group. 87 Assume RP1, RP2 and RP3 are all assigned the same IP address which is 88 used as the Anycast-RP address (let's say the IP address is RPA). 90 The following procedure is used when S1 starts sourcing traffic: 92 o S1 sends a multicast packet. 94 o The DR directly attached to S1 will form a PIM Register message to 95 send to RP1. The IP address to use is the Anycast-RP address. 97 o RP1 will receive the PIM Register message, decapsulate it, send the 98 packet down the shared-tree to get the packet to receivers R1 and R1'. 100 o RP1 is configured with RP2 and RP3's IP address. It will forward the 101 Register message from S1's DR to both of them. RP1 will include 102 it's own IP address as the source address for the PIM Register 103 message. 105 o RP1 sends a Register-Stop back to the DR. 107 o RP1 MAY join back to the source-tree by triggering a (S1,G) Join 108 message toward S1. However, RP1 MUST create (S1,G) state. 110 o RP2 receives the Register message from RP1, decapsulates it, and 111 also sends the packet down the shared-tree to get the packet to 112 receiver R2. 114 o RP2 sends a Register-Stop back to the RP1. 116 o RP2 MAY join back to the source-tree by triggering a (S1,G) Join 117 message toward S1. However, RP2 MUST create (S1,G) state. 119 o RP3 receives the Register message from RP1, decapsulates it, but 120 since there is no receivers joined for the group, it can discard 121 the packet. 123 o RP3 sends a Register-Stop back to the RP1. 125 o RP3 creates (S1,G) state so when a receiver joins after S1 starts 126 sending, RP3 can join quickly to the source-tree for S1. 128 The procedure for S3 sending follows the same as above but it is RP3 129 which forwards the Register originated by S3's DR to RP1 and RP2. 130 Therefore, this example shows how sources anywhere in the domain, 131 associated with different RPs, can reach all receivers, also 132 associated with different RPs, in the same domain. 134 4. Observations and Guidelines about this Proposal 136 o An RP will forward a Register only if the Register is received 137 from an IP address not in the Anycast-RP list (i.e. the Register 138 came from a DR and not another RP). 140 o Each DR that PIM registers for a source will send the message to it's 141 closest RP address. Therefore there are no changes to the DR logic. 143 o Packets flow to all receivers no matter what RP they have joined to. 145 o The source gets Registered to a single RP by the DR, it's the 146 responsibility of the RP, the DR selects, to get the packet to all 147 other RPs in the Anycast-RP set. 149 o Logic is changed only in the RPs. The logic change is for forwarding 150 Register messages. Register-Stop processing is unchanged. However, an 151 implementation MAY suppress sending Register-Stop messages in response 152 to a Register received from an RP. 154 o The rate-limiting of Register and Register-Stop messages are done 155 end-to-end. That is from DR -> RP1 -> {RP2 and RP3}. There is no need for 156 specific rate-limiting logic between the RPs. 158 o When topology changes occur, the existing source-tree adjusts as it 159 does today according to [1]. The existing shared-trees, as well, 160 adjust as it does today according to [1]. 162 o Physical RP changes are as fast as unicast route convergence. 163 Retaining the benefit of [2]. 165 o An RP that doesn't support this draft can be mixed with RPs that do 166 support this draft. However, the non-supporter RPs should not have 167 sources registering to it but may have receivers joined to it. 169 o If Null Registers are sent (Registers with an IP header and no IP 170 payload), they MUST be replicated to all of the RPs in the Anycast-RP 171 set so that source state remains alive for active sources. 173 o The number of RPs in the Anycast-RP set should remain small so the 174 amount of non-native replication is kept to a minimum. 176 5. Possible Configuration Language 178 A possible set of commands to be used could be: 180 ip pim anycast-rp 182 Where: 184 describes the Anycast-RP set for the RP which 185 is assigned to the group range. This IP address is the address 186 that first-hop and last-hop PIM routers use to register and join 187 to. 189 describes the IP address where Register messages are 190 forwarded to. This IP address is any address assigned to the RP 191 router not including the . 193 Example: 195 From the illustration above, the configuration commands would be: 197 ip pim anycast-rp RPA RP1 198 ip pim anycast-rp RPA RP2 199 ip pim anycast-rp RPA RP3 201 Comment: 203 It may be useful to include the local router's IP address in the 204 command set so the above lines can be cut-and-pasted or scripted 205 into all the RPs in the Anycast-RP set. 207 But the implementation would have to be aware of it's own address 208 and not inadvertently send a Register to itself. 210 6. Interaction with MSDP running in an Anycast-PIM Router 212 The objective of this Anycast-PIM proposal is to remove the 213 dependence on using MSDP. This can be achieved by removing MSDP 214 peering between the Anycast RPs. However, to advertise internal 215 sources to routers outside of a PIM routing domain and to learn 216 external sources from other routing domains, MSDP may still be 217 required. 219 In this capacity, when there are internal sources that need to be 220 advertised externally, an Anycast-RP which receives a Register 221 message, either from a DR or an Anycast-RP, should process it as 222 described in this specification as well as how to process a Register 223 message as described in [2]. That means an SA for the same internal 224 source could be originated by multiple Anycast-RPs doing the MSDP 225 peering. If this is not desirable, configuration of one or more 226 (rather than all) Anycast-RP MSDP routers would be the only ones to 227 originate SAs for internal sources. And in some situations, there is 228 a good possibility not all Anycast-RPs in the set will have MSDP 229 peering sessions so this issue can be mitigated to a certain extent. 231 From an Anycast-RP perspective, a source should be considered 232 internal to a domain, when it is discovered by an Anycast-RP through 233 a received Register message. Regardless, if the Register message was 234 sent by a DR, another Anycast-RP member, or the router itself. 236 For learning sources external to a domain, the MSDP SA messages could 237 arrive to multiple MSDP-peering Anycast-RPs. If data does not 238 accompany the SA, follow the rules documented in [2]. That is, have 239 PIM send a (S,G) join towards the source. If data accompanies the SA, 240 duplicate packets could be delivered to receivers (since each RP 241 would deliver the packet down each of their respective shared-trees). 242 To avoid this, only the highest IP address RP in the Anycast-RP set 243 will deliver the SA-data-encapsulated packets down it's shared tree. 244 To reach other share-trees rooted at the other Anycast-RPs, the 245 highest IP addressed router will create a Register message and 246 forward packet to the set of RPs in the Anycast-RP set as it would as 247 a functioning DR receiving packets from a directly connected source. 248 If not all routers in the Anycast-RP set are MSDP peering routers, 249 then configuration is required to identify which members are MSDP 250 peers, and the highest IP address of this subset will be used to 251 create and originate the Register message. 253 Within a routing domain, it is recommended that an Anycast-RP set 254 defined in this specification should not be mixed with MSDP peering 255 amoung the members. In some cases, the source discovery will work but 256 it may not be obvious to the implementations what sources are local 257 to the domain and which are not. This may affect external MSDP 258 advertisement of internal sources. 260 Having said that, this draft makes no attempt to connect MSDP peering 261 domains together by using Anycast-PIM inside a transit domain. 263 7. Acknowledgments 265 The authors would like to thank Yiqun Cai and Dino Farinacci for 266 prototyping this draft in the cisco IOS implementation and Procket 267 implementation, respectively. 269 The authors would like to thank John Zwiebel for doing 270 interoperability testing of the two prototype implementations. 272 And finally, the authors would like to thank Greg Shepard and Lenny 273 Giuliano for comments on the draft. 275 8. Author Information 277 Dino Farinacci 278 Procket Networks 279 dino@procket.com 281 Yiqun Cai 282 cisco Systems 283 ycai@cisco.com 285 9. References 287 [1] Estrin, et al., "Protocol Independent Multicast-Sparse Mode (PIM- 288 SM): Protocol Specification", RFC 2362, June 1998. 290 [2] Kim, Meyer, Kilmer, Farinacci, "Anycast RP mechanism using PIM 291 and MSDP", Internet Draft draft-ietf-mboned-anycast-rp-08.txt, 292 May 2001.