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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 INTERNET-DRAFT David Meyer 2 draft-ietf-mboned-ssm232-07.txt Rob Rockell 3 Greg Shepherd 4 Category Best Current Practice 5 Expires: July 2004 January 2004 7 Source-Specific Protocol Independent Multicast in 232/8 8 10 Status of this Document 12 This document is an Internet-Draft and is in full conformance with 13 all provisions of Section 10 of RFC2026. 15 Internet-Drafts are working documents of the Internet Engineering 16 Task Force (IETF), its areas, and its working groups. Note that 17 other groups may also distribute working documents as Internet- 18 Drafts. 20 Internet-Drafts are draft documents valid for a maximum of six months 21 and may be updated, replaced, or obsoleted by other documents at any 22 time. It is inappropriate to use Internet-Drafts as reference 23 material or to cite them other than as "work in progress." 25 The list of current Internet-Drafts can be accessed at 26 http://www.ietf.org/ietf/1id-abstracts.txt 28 The list of Internet-Draft Shadow Directories can be accessed at 29 http://www.ietf.org/shadow.html. 31 The key words "MUST"", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 32 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 33 document are to be interpreted as described in RFC 2119 [RFC 2119]. 35 This document is a product of the MBONED WG. Comments should be 36 addressed to the authors, or the mailing list at 37 mboned@ns.uoregon.edu. 39 Copyright Notice 41 Copyright (C) The Internet Society (2004). All Rights Reserved. 43 Abstract 45 IP Multicast group addresses in the 232/8 (232.0.0.0 to 46 232.255.255.255) range are designated as source-specific multicast 47 destination addresses and are reserved for use by source-specific 48 multicast applications and protocols. This document defines 49 operational recommendations to ensure source-specific behavior within 50 the 232/8 range. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 2. Operational practices in 232/8 . . . . . . . . . . . . . . . . 4 56 2.1. Preventing local sources from sending to shared tree. . . . 4 57 2.2. Preventing remote sources from being learned/joined via MSDP. 4 58 2.3. Preventing receivers from joining the shared tree . . . . . 5 59 2.4. Preventing RP's as candidates for 232/8 . . . . . . . . . . 5 60 3. Intellectual Property. . . . . . . . . . . . . . . . . . . . . 6 61 4. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 6 62 5. Security Considerations. . . . . . . . . . . . . . . . . . . . 6 63 6. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 7 64 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 65 7.1. Normative References. . . . . . . . . . . . . . . . . . . . 8 66 7.2. Informative References. . . . . . . . . . . . . . . . . . . 8 67 8. Author's Addresses . . . . . . . . . . . . . . . . . . . . . . 9 68 9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 9 70 1. Introduction 72 Current PIM Sparse Mode (PIM-SM) [RFC2362] relies on the shared 73 Rendezvous Point (RP) tree to learn about active sources for a group 74 and to support group-generic (not source specific) data distribution. 75 The IP Multicast group address range 232/8 has been designated for 76 Source-Specific PIM [RFC3569] applications and protocols [IANA] and 77 SHOULD support source-only trees only, precluding the requirement of 78 an RP and a shared tree; active sources in the 232/8 range will be 79 discovered out of band. PIM Sparse Mode Designated Routers (DR), with 80 local membership, are capable of joining the shortest path tree for 81 the source directly using Source-Specific PIM (also known as PIM-SSM 82 or simply SSM). 84 Operational best common practices in the 232/8 group address range 85 are necessary to ensure shortest path source-only trees across 86 multiple domains in the Internet [RFC3569], and to prevent data from 87 sources sending to groups in the 232/8 range from arriving via shared 88 trees. This avoids unwanted data arrival, and allows several sources 89 to use the same group address without conflict at the receivers. 91 The operational practices SHOULD: 93 o Prevent local sources from sending to shared tree 95 o Prevent receivers from joining the shared tree 97 o Prevent RP's as candidates for 232/8 99 o Prevent remote sources from being learned/joined via MSDP 100 [RFC3618] 102 2. Operational practices in 232/8 104 2.1. Preventing local sources from sending to shared tree 106 Eliminating the use of shared trees for groups in 232/8, while 107 maintaining coexistence with PIM-SM, behavior of the RP and/or the DR 108 needs to be modified. This can be accomplished by 110 - preventing data for 232/8 groups from being sent encapsulated to 111 the RP by the DR 113 - preventing the RP from accepting registers for 232/8 groups from 114 the DR 116 - preventing the RP from forwarding accepted data down (*,G) 117 tree for 232/8 groups 119 2.2. Preventing remote sources from being learned/joined via MSDP 121 PIM-SSM does not require active source announcements via MSDP. All 122 source announcements are received out of band, the the last hop 123 router being responsible for sending (S,G) joins directly to the 124 source. To prevent propagation of SAs in the 232/8 range, an RP 125 SHOULD 127 - never originate an SA for any 232/8 groups 129 - never accept or forward an SA for any 232/8 groups. 131 2.3. Preventing receivers from joining the shared tree 133 Local PIM domain practices need to be enforced to prevent local 134 receivers from joining the shared tree for 232/8 groups. This can be 135 accomplished by 137 - preventing DR from sending (*,G) joins for 232/8 groups 139 - preventing RP from accepting (*,G) join for 232/8 groups 141 However, within a local PIM domain, any last-hop router NOT 142 preventing (*,G) joins may trigger unwanted (*,G) state toward the RP 143 which intersects an existing (S,G) tree, allowing the receiver on the 144 shared tree to receive the data, breaking the source-specific 145 [RFC3569] service model. It is therefore recommended that ALL routers 146 in the domain MUST reject AND never originate (*,G) joins for 232/8 147 groups. 149 In those cases in which an ISP is offering its customers (or others) 150 the use of the ISP's RP, the ISP SHOULD NOT allow (*,G) joins in the 151 232/8 range. 153 2.4. Preventing RP's as candidates for 232/8 155 Because PIM-SSM does not require an RP, all RPs SHOULD NOT offer 156 themselves as candidates in the 232/8 range. This can be accomplished 157 by 159 - preventing RP/BSR from announcing in the 232/8 range 161 - preventing ALL routers from accepting RP delegations in the 162 232/8 range 164 - precluding RP functionality on RP for the 232/8 range 166 Note that in typical practice, RP's announce themselves as candidates 167 for the 224/4 (which obviously includes 232/8). It is still 168 acceptable to allow the advertisement of 224/4 (or any other superset 169 of 232/8); however, this approach relies on the second point, above, 170 namely, that routers silently just ignore the RP delegation in the 171 232/8 range, and prevent sending or receiving using the shared tree, 172 as described previously. Finally, an RP SHOULD NOT be configured as 173 a candidate RP for 232/8 (or more specific range). 175 3. Intellectual Property 177 The IETF takes no position regarding the validity or scope of any 178 intellectual property or other rights that might be claimed to 179 pertain to the implementation or use of the technology described in 180 this document or the extent to which any license under such rights 181 might or might not be available; neither does it represent that it 182 has made any effort to identify any such rights. Information on the 183 IETF's procedures with respect to rights in standards-track and 184 standards-related documentation can be found in BCP-11 [RFC2028]. 185 Copies of claims of rights made available for publication and any 186 assurances of licenses to be made available, or the result of an 187 attempt made to obtain a general license or permission for the use of 188 such proprietary rights by implementors or users of this 189 specification can be obtained from the IETF Secretariat. 191 The IETF invites any interested party to bring to its attention any 192 copyrights, patents or patent applications, or other proprietary 193 rights which may cover technology that may be required to practice 194 this standard. Please address the information to the IETF Executive 195 Director. 197 4. Acknowledgments 199 This document is the work of many people in the multicast community, 200 including (but not limited to) Dino Farinacci, John Meylor, John 201 Zwiebel, Tom Pusateri, Dave Thaler, Toerless Eckert, Leonard 202 Giuliano, Mike McBride, and Pekka Savola. 204 5. Security Considerations 206 This document describes operational practices that introduce no new 207 security issues to either PIM-SM or PIM-SSM. 209 However, in the event that the operational practices described in 210 this document are not adhered to, some problems may surface. In 211 particular, section 2.3 describes the effects of non-compliance of 212 last-hop routers (or to some degree, rogue hosts sending PIM messages 213 themselves) on the source-specific service model; creating the (*,G) 214 state for source-specific (S,G) could enable a receiver to receive 215 data it should not get. This can be mitigated by host-side multicast 216 source filtering. 218 6. IANA Considerations 220 This document creates no new requirements on IANA namespaces 221 [RFC2434]. 223 7. References 225 7.1. Normative References 227 [RFC2119] Bradner, S., "Key words for use in RFCs to 228 Indicate Requirement Levels", RFC 2119, March, 229 1997. 231 [RFC2026] Bradner, S., "The Internet Standards Process -- 232 Revision 3", RFC 2026/BCP 9, October, 1996. 234 [RFC2028] Hovey, R. and S. Bradner, "The Organizations 235 Involved in the IETF Standards Process", RFC 236 2028/BCP 11, October, 1996. 238 [RFC2362] Estrin, D., et. al., "Protocol Independent 239 Multicast-Sparse Mode (PIM-SM): Protocol 240 Specification", RFC 2362, June, 1998. 242 [RFC2434] Narten, T., and H. Alvestrand, "Guidelines for 243 Writing an IANA Considerations Section in RFCs", 244 RFC 2434/BCP 26, October 1998. 246 [RFC3569] Bhattacharyya, S. Editor, "An Overview of 247 Source-Specific Multicast (SSM)" RFC 3569, July, 248 2003. 250 [RFC3618] Meyer, D. and B. Fenner (Editors), "The Multicast 251 Source Discovery Protocol (MSDP)", RFC 3618, 252 October, 2003. 254 7.2. Informative References 256 [IANA] http://www.iana.org 258 8. Author's Addresses 260 David Meyer 261 Email: dmm@1-4-5.net 263 Robert Rockell 264 Sprint 265 Email: rrockell@sprint.net 267 Greg Shepherd 268 Procket 269 Email: shep@procket.com 271 9. Full Copyright Statement 273 Copyright (C) The Internet Society (2004). All Rights Reserved. 275 This document and translations of it may be copied and furnished to 276 others, and derivative works that comment on or otherwise explain it 277 or assist in its implementation may be prepared, copied, published 278 and distributed, in whole or in part, without restriction of any 279 kind, provided that the above copyright notice and this paragraph are 280 included on all such copies and derivative works. However, this 281 document itself may not be modified in any way, such as by removing 282 the copyright notice or references to the Internet Society or other 283 Internet organizations, except as needed for the purpose of 284 developing Internet standards in which case the procedures for 285 copyrights defined in the Internet Standards process must be 286 followed, or as required to translate it into languages other than 287 English. 289 The limited permissions granted above are perpetual and will not be 290 revoked by the Internet Society or its successors or assigns. 292 This document and the information contained herein is provided on an 293 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 294 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 295 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 296 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 297 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.