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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-ssm232-06.txt Rob Rockell 3 Greg Shepherd 4 Category Best Current Practice 5 Expires: March 2004 September 2003 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 (2003). 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 [SSM] destination addresses and are reserved for use by source- 48 specific 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 [SSM] 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 know 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 [SSM], 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 [MSDP] 101 2. Operational practices in 232/8 103 2.1. Preventing local sources from sending to shared tree 105 Eliminating the use of shared trees for groups in 232/8, while 106 maintaining coexistence with PIM-SM, behavior of the RP and/or the DR 107 needs to be modified. This can be accomplished by 109 - preventing data for 232/8 groups from being sent encapsulated to 110 the RP by the DR 112 - preventing the RP from accepting registers for 232/8 groups from 113 the DR 115 - preventing the RP from forwarding accepted data down (*,G) 116 tree for 232/8 groups 118 2.2. Preventing remote sources from being learned/joined via MSDP 120 PIM-SSM does not require active source announcements via MSDP. All 121 source announcements are received out of band, the the last hop 122 router being responsible for sending (S,G) joins directly to the 123 source. To prevent propagation of SAs in the 232/8 range, an RP 124 SHOULD 126 - never originate an SA for any 232/8 groups 128 - never accept or forward an SA for any 232/8 groups. 130 2.3. Preventing receivers from joining the shared tree 132 Local PIM domain practices need to be enforced to prevent local 133 receivers from joining the shared tree for 232/8 groups. This can be 134 accomplished by 136 - preventing DR from sending (*,G) joins for 232/8 groups 138 - preventing RP from accepting (*,G) join for 232/8 groups 140 However, within a local PIM domain, any last-hop router NOT 141 preventing (*,G) joins may trigger unwanted (*,G) state toward 142 the RP which intersects an existing (S,G) tree, allowing the 143 receiver on the shared tree to receive the data, breaking the 144 source-specific [SSM] service model. It is therefore recommended 145 that ALL routers in the domain MUST reject AND never originate 146 (*,G) joins for 232/8 groups. 148 In those cases in which an ISP is offering its customers (or 149 others) the use of the ISP's RP, the ISP SHOULD NOT allow (*,G) 150 joins in the 232/8 range. 152 2.4. Preventing RP's as candidates for 232/8 154 Because PIM-SSM does not require an RP, all RPs SHOULD NOT offer 155 themselves as candidates in the 232/8 range. This can be accomplished 156 by 158 - preventing RP/BSR from announcing in the 232/8 range 160 - preventing ALL routers from accepting RP delegations in the 161 232/8 range 163 - precluding RP functionality on RP for the 232/8 range 165 Note that in typical practice, RP's announce themselves as candidates 166 for the 224/4 (which obviously includes 232/8). It is still 167 acceptable to allow the advertisement of 224/4 (or any other superset 168 of 232/8); however, this approach relies on the second point, above, 169 namely, that routers silently just ignore the RP delegation in the 170 232/8 range, and prevent sending or receiving using the shared tree, 171 as described previously. Finally, an RP SHOULD NOT be configured as 172 a candidate RP for 232/8 (or more specific range). 174 3. Intellectual Property 176 The IETF takes no position regarding the validity or scope of any 177 intellectual property or other rights that might be claimed to 178 pertain to the implementation or use of the technology described in 179 this document or the extent to which any license under such rights 180 might or might not be available; neither does it represent that it 181 has made any effort to identify any such rights. Information on the 182 IETF's procedures with respect to rights in standards-track and 183 standards-related documentation can be found in BCP-11 [RFC2028]. 184 Copies of claims of rights made available for publication and any 185 assurances of licenses to be made available, or the result of an 186 attempt made to obtain a general license or permission for the use of 187 such proprietary rights by implementors or users of this 188 specification can be obtained from the IETF Secretariat. 190 The IETF invites any interested party to bring to its attention any 191 copyrights, patents or patent applications, or other proprietary 192 rights which may cover technology that may be required to practice 193 this standard. Please address the information to the IETF Executive 194 Director. 196 4. Acknowledgments 198 This document is the work of many people in the multicast community, 199 including (but not limited to) Dino Farinacci, John Meylor, John 200 Zwiebel, Tom Pusateri, Dave Thaler, Toerless Eckert, Leonard 201 Giuliano, Mike McBride, and Pekka Savola. 203 5. Security Considerations 205 This document describes operational practices that introduce no new 206 security issues to either PIM-SM or PIM-SSM. 208 However, in the event that the operational practices described in 209 this document are not adhered to, some problems may surface. In 210 particular, section 2.3 describes the effects of non-compliance of 211 last-hop routers (or to some degree, rogue hosts sending PIM messages 212 themselves) on the source-specific service model; creating the (*,G) 213 state for source-specific (S,G) could enable a receiver to receive 214 data it should not get. This can be mitigated by host-side multicast 215 source filtering. 217 6. IANA Considerations 219 This document creates no new requirements on IANA namespaces 220 [RFC2434]. 222 7. References 224 7.1. Normative References 226 [MSDP] Meyer, D. and B. Fenner (Editors), "The Multicast 227 Source Discovery Protocol (MSDP)", 228 draft-ietf-msdp-spec-20.txt. Work in Progress. 230 [SSM] Holbrook, H., and B. Cain,, "Source-Specific 231 Multicast", draft-ietf-ssm-arch-03.txt. Work in 232 Progress. 234 [RFC2119] Bradner, S., "Key words for use in RFCs to 235 Indicate Requirement Levels", RFC 2119, March, 236 1997. 238 [RFC2026] Bradner, S., "The Internet Standards Process -- 239 Revision 3", RFC 2026/BCP 9, October, 1996. 241 [RFC2028] Hovey, R. and S. Bradner, "The Organizations 242 Involved in the IETF Standards Process", RFC 243 2028/BCP 11, October, 1996. 245 [RFC2362] Estrin, D., et. al., "Protocol Independent 246 Multicast-Sparse Mode (PIM-SM): Protocol 247 Specification", RFC 2362, June, 1998. 249 [RFC2434] Narten, T., and H. Alvestrand, "Guidelines for 250 Writing an IANA Considerations Section in RFCs", 251 RFC 2434/BCP 26, October 1998. 253 7.2. Informative References 255 [IANA] http://www.iana.org 257 8. Author's Addresses 259 David Meyer 260 Email: dmm@1-4-5.net 262 Robert Rockell 263 Sprint 264 Email: rrockell@sprint.net 266 Greg Shepherd 267 Procket 268 Email: shep@procket.com 270 9. Full Copyright Statement 272 Copyright (C) The Internet Society (2003). All Rights Reserved. 274 This document and translations of it may be copied and furnished to 275 others, and derivative works that comment on or otherwise explain it 276 or assist in its implementation may be prepared, copied, published 277 and distributed, in whole or in part, without restriction of any 278 kind, provided that the above copyright notice and this paragraph are 279 included on all such copies and derivative works. However, this 280 document itself may not be modified in any way, such as by removing 281 the copyright notice or references to the Internet Society or other 282 Internet organizations, except as needed for the purpose of 283 developing Internet standards in which case the procedures for 284 copyrights defined in the Internet Standards process must be 285 followed, or as required to translate it into languages other than 286 English. 288 The limited permissions granted above are perpetual and will not be 289 revoked by the Internet Society or its successors or assigns. 291 This document and the information contained herein is provided on an 292 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 293 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 294 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 295 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 296 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.