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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT David Meyer 3 draft-ietf-mboned-ssm232-08.txt Rob Rockell 4 Greg Shepherd 5 Category Best Current Practice 6 Expires: September 2004 March 2004 8 Source-Specific Protocol Independent Multicast in 232/8 9 11 Status of this Document 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 This document is a product of the MBONED WG. Comments should be 33 addressed to the authors, or the mailing list at 34 mboned@ns.uoregon.edu. 36 Copyright Notice 38 Copyright (C) The Internet Society (2004). All Rights Reserved. 40 Abstract 42 IP Multicast group addresses in the 232/8 (232.0.0.0 to 43 232.255.255.255) range are designated as source-specific multicast 44 destination addresses and are reserved for use by source-specific 45 multicast applications and protocols. This document defines 46 operational recommendations to ensure source-specific behavior within 47 the 232/8 range. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 1.1. BCP, Experimental Protocols and Normative References. . . . 4 53 2. Operational practices in 232/8 . . . . . . . . . . . . . . . . 5 54 2.1. Preventing local sources from sending to shared tree. . . . 5 55 2.2. Preventing remote sources from being learned/joined via MSDP. 6 56 2.3. Preventing receivers from joining the shared tree . . . . . 6 57 2.4. Preventing RP's as candidates for 232/8 . . . . . . . . . . 7 58 3. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 7 59 4. Security Considerations. . . . . . . . . . . . . . . . . . . . 7 60 5. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 8 61 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 62 6.1. Normative References. . . . . . . . . . . . . . . . . . . . 9 63 6.2. Informative References. . . . . . . . . . . . . . . . . . . 9 64 7. Author's Addresses . . . . . . . . . . . . . . . . . . . . . . 10 65 8. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 10 66 9. Intellectual Property. . . . . . . . . . . . . . . . . . . . . 11 67 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 11 69 1. Introduction 71 Current PIM Sparse Mode (PIM-SM) [PIM-SM] relies on the shared 72 Rendezvous Point (RP) tree to learn about active sources for a group 73 and to support group-generic (not source specific) data distribution. 74 The IP Multicast group address range 232/8 has been designated for 75 Source-Specific PIM [RFC3569] applications and protocols [IANA] and 76 SHOULD support source-only trees only, precluding the requirement of 77 an RP and a shared tree; active sources in the 232/8 range will be 78 discovered out of band. PIM Sparse Mode Designated Routers (DR), with 79 local membership, are capable of joining the shortest path tree for 80 the source directly using Source-Specific PIM (also known as PIM-SSM 81 or simply SSM). 83 Operational best common practices in the 232/8 group address range 84 are necessary to ensure shortest path source-only trees across 85 multiple domains in the Internet [RFC3569], and to prevent data from 86 sources sending to groups in the 232/8 range from arriving via shared 87 trees. This avoids unwanted data arrival, and allows several sources 88 to use the same group address without conflict at the receivers. 90 The operational practices SHOULD: 92 o Prevent local sources from sending to shared tree 94 o Prevent receivers from joining the shared tree 96 o Prevent RP's as candidates for 232/8 98 o Prevent remote sources from being learned/joined via MSDP 99 [RFC3618] 101 1.1. BCP, Experimental Protocols and Normative References 103 This document describes the best current practice for a widely 104 deployed Experimental protocol, MSDP. There is no plan to advance the 105 MSDP's status (for example, to Proposed Standard). The reasons for 106 this include: 108 o MSDP was originally envisioned as a temporary protocol to be 109 supplanted by whatever the IDMR working group produced as an 110 inter-domain protocol. However, the IDMR WG (or subsequently, 111 the BGMP WG) never produced a protocol that could be deployed 112 to replace MSDP. 114 o One of the primary reasons given for MSDP to be classified as 115 Experimental was that the MSDP Working Group came up with 116 modifications to the protocol that the WG thought made it 117 better but that implementors didn't see any reasons to 118 deploy. Without these modifications (e.g., UDP or GRE 119 encapsulation), MSDP can have negative consequences to initial 120 packets in datagram streams. 122 o Scalability: Although we don't know what the hard limits might 123 be, readvertising everything you know every 60 seconds clearly 124 limits the amount of state you can advertise. 126 o MSDP reached near ubiquitous deployment as the de-facto 127 standard inter-domain multicast protocol in the IPv4 Internet. 129 o No consensus could be reached regarding the reworking of MSDP 130 to address the many concerns of various constituencies within 131 the IETF. As a result, a decision was taken to document what is 132 (ubiquitously) deployed and move that document to Experimental. 133 While advancement of MSDP to Proposed Standard was considered, 134 for the reasons mentioned above, it was immediately discarded. 136 o The advent of protocols such as source specific multicast and 137 bi-directional PIM, as well as embedded RP techniques for 138 IPv6, have further reduced consensus that a replacement 139 protocol for MSDP for the IPv4 Internet is required. 141 The RFC Editor's policy regarding references is that they be split 142 into two categories known as "normative" and "informative". Normative 143 references specify those documents which must be read to understand 144 or implement the technology in an RFC (or whose technology must be 145 present for the technology in the new RFC to work) [RFCED]. In order 146 to understand this document, one must also understand both the PIM 147 and MSDP documents. As a result, references to these documents are 148 normative. 150 The IETF has adopted the policy that BCPs must not have normative 151 references to Experimental protocols. However, this document is a 152 special case in that the underlying Experimental document (MSDP) is 153 not planned to be advanced to Proposed Standard. 155 The MBONED Working Group requests approval under the Variance 156 Procedure as documented in RFC 2026 [RFC2026]. 158 Note to RFC-Editor: If IETF/IESG approves this, please change the 159 above sentence into: The MBONED Working Group has requested approval 160 under the Variance Procedure as documented in RFC 2026 [RFC2026]. 161 The IESG followed the Variance Procedure, and after an additional 4 162 week IETF Last Call evaluated the comments and status and has 163 approved this document. 165 The key words "MUST"", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 166 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 167 document are to be interpreted as described in RFC 2119 [RFC 2119]. 169 2. Operational practices in 232/8 171 2.1. Preventing local sources from sending to shared tree 173 Eliminating the use of shared trees for groups in 232/8, while 174 maintaining coexistence with PIM-SM, behavior of the RP and/or the DR 175 needs to be modified. This can be accomplished by 177 - preventing data for 232/8 groups from being sent encapsulated to 178 the RP by the DR 180 - preventing the RP from accepting registers for 232/8 groups from 181 the DR 183 - preventing the RP from forwarding accepted data down (*,G) 184 tree for 232/8 groups 186 2.2. Preventing remote sources from being learned/joined via MSDP 188 PIM-SSM does not require active source announcements via MSDP. All 189 source announcements are received out of band, the the last hop 190 router being responsible for sending (S,G) joins directly to the 191 source. To prevent propagation of SAs in the 232/8 range, an RP 192 SHOULD 194 - never originate an SA for any 232/8 groups 196 - never accept or forward an SA for any 232/8 groups. 198 2.3. Preventing receivers from joining the shared tree 200 Local PIM domain practices need to be enforced to prevent local 201 receivers from joining the shared tree for 232/8 groups. This can be 202 accomplished by 204 - preventing DR from sending (*,G) joins for 232/8 groups 206 - preventing RP from accepting (*,G) join for 232/8 groups 208 However, within a local PIM domain, any last-hop router NOT 209 preventing (*,G) joins may trigger unwanted (*,G) state toward the RP 210 which intersects an existing (S,G) tree, allowing the receiver on the 211 shared tree to receive the data, breaking the source-specific 212 [RFC3569] service model. It is therefore recommended that ALL routers 213 in the domain MUST reject AND never originate (*,G) joins for 232/8 214 groups. 216 In those cases in which an ISP is offering its customers (or others) 217 the use of the ISP's RP, the ISP SHOULD NOT allow (*,G) joins in the 218 232/8 range. 220 2.4. Preventing RP's as candidates for 232/8 222 Because PIM-SSM does not require an RP, all RPs SHOULD NOT offer 223 themselves as candidates in the 232/8 range. This can be accomplished 224 by 226 - preventing RP/BSR from announcing in the 232/8 range 228 - preventing ALL routers from accepting RP delegations in the 229 232/8 range 231 - precluding RP functionality on RP for the 232/8 range 233 Note that in typical practice, RP's announce themselves as candidates 234 for the 224/4 (which obviously includes 232/8). It is still 235 acceptable to allow the advertisement of 224/4 (or any other superset 236 of 232/8); however, this approach relies on the second point, above, 237 namely, that routers silently just ignore the RP delegation in the 238 232/8 range, and prevent sending or receiving using the shared tree, 239 as described previously. Finally, an RP SHOULD NOT be configured as 240 a candidate RP for 232/8 (or more specific range). 242 3. Acknowledgments 244 This document is the work of many people in the multicast community, 245 including (but not limited to) Dino Farinacci, John Meylor, John 246 Zwiebel, Tom Pusateri, Dave Thaler, Toerless Eckert, Leonard 247 Giuliano, Mike McBride, and Pekka Savola. 249 4. Security Considerations 251 This document describes operational practices that introduce no new 252 security issues to either PIM-SM or PIM-SSM. 254 However, in the event that the operational practices described in 255 this document are not adhered to, some problems may surface. In 256 particular, section 2.3 describes the effects of non-compliance of 257 last-hop routers (or to some degree, rogue hosts sending PIM messages 258 themselves) on the source-specific service model; creating the (*,G) 259 state for source-specific (S,G) could enable a receiver to receive 260 data it should not get. This can be mitigated by host-side multicast 261 source filtering. 263 5. IANA Considerations 265 This document creates no new requirements on IANA namespaces 266 [RFC2434]. 268 6. References 270 6.1. Normative References 272 [PIM-SM] Fenner, B., et. al, "Protocol Independent Multicast - 273 Sparse Mode (PIM-SM): Protocol Specification 274 (Revised)", draft-ietf-pim-sm-v2-new-09.txt. Work 275 in progress. 277 [RFC2119] Bradner, S., "Key words for use in RFCs to 278 Indicate Requirement Levels", RFC 2119, March, 279 1997. 281 [RFC2026] Bradner, S., "The Internet Standards Process -- 282 Revision 3", RFC 2026/BCP 9, October, 1996. 284 [RFC2028] Hovey, R. and S. Bradner, "The Organizations 285 Involved in the IETF Standards Process", RFC 286 2028/BCP 11, October, 1996. 288 [RFC2434] Narten, T., and H. Alvestrand, "Guidelines for 289 Writing an IANA Considerations Section in RFCs", 290 RFC 2434/BCP 26, October 1998. 292 [RFC3569] Bhattacharyya, S. Editor, "An Overview of 293 Source-Specific Multicast (SSM)" RFC 3569, July, 294 2003. 296 [RFC3618] Meyer, D. and B. Fenner (Editors), "The Multicast 297 Source Discovery Protocol (MSDP)", RFC 3618, 298 October, 2003. 300 6.2. Informative References 302 [IANA] http://www.iana.org 304 7. Author's Addresses 306 David Meyer 307 Email: dmm@1-4-5.net 309 Robert Rockell 310 Sprint 311 Email: rrockell@sprint.net 313 Greg Shepherd 314 Procket 315 Email: shep@procket.com 317 8. Full Copyright Statement 319 Copyright (C) The Internet Society (2004). This document is subject 320 to the rights, licenses and restrictions contained in BCP 78 and 321 except as set forth therein, the authors retain all their rights. 323 This document and translations of it may be copied and furnished to 324 others, and derivative works that comment on or otherwise explain it 325 or assist in its implementation may be prepared, copied, published 326 and distributed, in whole or in part, without restriction of any 327 kind, provided that the above copyright notice and this paragraph are 328 included on all such copies and derivative works. However, this 329 document itself may not be modified in any way, such as by removing 330 the copyright notice or references to the Internet Society or other 331 Internet organizations, except as needed for the purpose of 332 developing Internet standards in which case the procedures for 333 copyrights defined in the Internet Standards process must be 334 followed, or as required to translate it into languages other than 335 English. 337 The limited permissions granted above are perpetual and will not be 338 revoked by the Internet Society or its successors or assigns. 340 This document and the information contained herein is provided on an 341 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 342 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 343 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 344 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 345 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 347 9. Intellectual Property 349 The IETF takes no position regarding the validity or scope of any 350 Intellectual Property Rights or other rights that might be claimed to 351 pertain to the implementation or use of the technology described in 352 this document or the extent to which any license under such rights 353 might or might not be available; nor does it represent that it has 354 made any independent effort to identify any such rights. 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